Bio

Bio


Dr. Maan is currently a Plastic Surgery resident at Stanford University. He earned his medical degree from King’s College London School of Medicine. Before leaving the UK, he also earned an MSc in Surgical Technology from Imperial College London, completed Core Surgical Training, and was inducted as a Member of the Royal College of Surgeons of England (MRCS). In 2012, he moved to Stanford to pursue a postdoctoral fellowship in regenerative medicine in the laboratory of Dr Geoffrey Gurtner, where he spent 3 years before starting residency.

Clinical Focus


  • Residency
  • Plastic & Reconstructive Surgery

Honors & Awards


  • Thuss Award, Stanford University Plastic Surgery (2016)
  • Clifford C. Snyder, MD Past Chairman Award, Plastic Surgery Research Council (2015)
  • TRAM Pilot Grant Renewal, Stanford University Translational Research and Applied Medicine (2015)
  • Best Basic Science Presentation Award, Stanford Plastic Surgery Research Symposium (2014)
  • Excellence in Research Award, American College of Surgeons (2014)
  • Plastic Surgery Education Foundation Research Fellowship Grant, Plastic Surgery Foundation (2014)
  • TRAM Pilot Grant, Stanford University Translational Research and Applied Medicine (2014)
  • Highly Commended Certificate Award, British Medical Association Medical Book Awards (2013)
  • MBBS with Honors, King's College London School of Medicine (2008)

Boards, Advisory Committees, Professional Organizations


  • Member, ASPS/PSF Researcher Education Subcommittee (2018 - Present)
  • Member, American Society for Peripheral Nerve (2018 - Present)
  • Member, ASPS Residents Council (2018 - Present)
  • Member, Plastic Surgery Research Council Technology Committee (2018 - Present)
  • Member, CSPS Scientific Program Committee (2017 - 2018)
  • Member, Plastic Surgery Research Council (2014 - Present)
  • Member, Association of Academic Surgeons (2012 - Present)
  • Member, The Royal College of Surgeons of England (2011 - Present)

Professional Education


  • MBBS, King's College London School of Medicine, Medicine (2008)
  • DPMSA, The Worshipful Society of Apothecaries, Philosophy of Medicine (2009)
  • MSc, Imperial College London, Surgical Technology (2011)
  • Certificate, Stanford Graduate School of Business, Ignite Program in Innovation and Entrepreneurship (2013)

Research & Scholarship

Current Research and Scholarly Interests


My research focuses on signaling networks and cell populations governing regeneration and fibrosis in various biological settings, including foreign body reaction at the peripheral nerve / electrode interface.

Lab Affiliations


Publications

All Publications


  • Deferoxamine enhances the regenerative potential of diabetic Adipose Derived Stem Cells. Journal of plastic, reconstructive & aesthetic surgery : JPRAS Hopfner, U., Maan, Z. N., Hu, M. S., Aitzetmuller, M. M., Zaussinger, M., Kirsch, M., Machens, H., Duscher, D. 2020

    Abstract

    INTRODUCTION: Diabetes mellitus remains a significant public health problem, consuming over $400 billion every year. While Diabetes itself can be controlled effectively, impaired wound healing still occurs frequently in diabetic patients. Adipose-derived mesenchymal stem cells (ASCs) provide an especially appealing source for diabetic wound cell therapy. With autologous approaches, the functionality of ASCs largely underlie patient-dependent factors. Diabetes is a significant diminishing factor of MSC functionality. Here, we explore a novel strategy to enhance diabetic ASC functionality through deferoxamine (DFO) preconditioning.MATERIAL AND METHODS: Human diabetic ASCs have been preconditioned with 150 M and 300 M DFO in vitro and analyzed for regenerative cytokine expression. Murine diabetic ASCs have been preconditioned with 150 M DFO examined for their in vitro and in vivo vasculogenic capacity in Matrigel assays. Additionally, a diabetic murine wound healing model has been performed to assess the regenerative capacity of preconditioned cells.RESULTS: DFO preconditioning enhances the VEGF expression of human diabetic ASCs through hypoxia-inducible factor upregulation. The use of 150 M of DFO was an optimal concentration to induce regenerative effects. The vasculogenic potential of preconditioned diabetic ASCs is significantly greater in vitro and in vivo. The enhanced regenerative functionality of DFO preconditioned ASCs was further confirmed in a model of diabetic murine wound healing.CONCLUSION: These results demonstrate that DFO significantly induced the upregulation of hypoxia-inducible factor-1 alpha and VEGF in diabetic ASCs and showed efficacy in the treatment of diabetes-associated deficits of wound healing. The favorable status of DFO as a small molecule drug approved since decades for multiple indications makes this approach highly translatable.

    View details for DOI 10.1016/j.bjps.2020.02.045

    View details for PubMedID 32418841

  • Molecular Mechanisms of Hair Growth and Regeneration: Current Understanding and Novel Paradigms. Dermatology (Basel, Switzerland) Houschyar, K. S., Borrelli, M. R., Tapking, C., Popp, D., Puladi, B., Ooms, M., Chelliah, M. P., Rein, S., Pforringer, D., Thor, D., Reumuth, G., Wallner, C., Branski, L. K., Siemers, F., Grieb, G., Lehnhardt, M., Yazdi, A. S., Maan, Z. N., Duscher, D. 2020: 1–10

    Abstract

    Hair is a defining feature of mammals and has critical functions, including protection, production of sebum, apocrine sweat and pheromones, social and sexual interactions, thermoregulation, and provision of stem cells for skin homeostasis, regeneration, and repair. The hair follicle (HF) is considered a "mini-organ," consisting of intricate and well-organized structures which originate from HF stem and progenitor cells. Dermal papilla cells are the main components of the mesenchymal compartments in the hair bulb and are instrumental in generating signals to regulate the behavior of neighboring epithelial cells during the hair cycle. Mesenchymal-epithelial interactions within the dermal papilla niche drive HF embryonic development as well as the postnatal hair growth and regeneration cycle. This review summarizes the current understanding of HF development, repair, and regeneration, with special focus on cell signaling pathways governing these processes. In particular, we discuss emerging paradigms of molecular signaling governing the dermal papilla-epithelial cellular interactions during hair growth and maintenance and the recent progress made towards tissue engineering of human hair follicles.

    View details for DOI 10.1159/000506155

    View details for PubMedID 32163945

  • Burns: modified metabolism and the nuances of nutrition therapy. Journal of wound care Houschyar, M., Borrelli, M. R., Tapking, C., Maan, Z. N., Rein, S., Chelliah, M. P., Sheckter, C. C., Duscher, D., Branski, L. K., Wallner, C., Behr, B., Lehnhardt, M., Siemers, F., Houschyar, K. S. 2020; 29 (3): 184–91

    Abstract

    OBJECTIVE: To review the effects of burn injury on nutritional requirements and how this can best be supported in a healthcare setting.METHOD: A literature search for articles discussing nutrition and/or metabolism following burn injury was carried out. PubMed, Embase and Web of Science databases were searched using the key search terms 'nutrition' OR 'metabolism' AND 'burn injury' OR 'burns'. There was no limitation on the year of publication.RESULTS: A total of nine articles met the inclusion criteria, the contents of which are discussed in this manuscript.CONCLUSION: Thermal injury elicits the greatest metabolic response, among all traumatic events, in critically ill patients. In order to ensure burn patients can meet the demands of their increased metabolic rate and energy expenditure, adequate nutritional support is essential. Burn injury results in a unique pathophysiology, involving alterations in endocrine, inflammatory, metabolic and immune pathways and nutritional support needed during the inpatient stay varies depending on burn severity and idiosyncratic patient physiologic parameters.

    View details for DOI 10.12968/jowc.2020.29.3.184

    View details for PubMedID 32160092

  • Innovation in Plastic Surgery: A Call for Re-Emergence of the Surgeon-Scientist. Plastic and reconstructive surgery Oliver, J. D., Hu, A. C., Maan, Z. N., Hu, M. S. 2020

    View details for DOI 10.1097/PRS.0000000000006694

    View details for PubMedID 31977979

  • A single-center blinded randomized clinical trial to evaluate the anti-aging effects of a novel HSF™-based skin care formulation. Journal of cosmetic dermatology Duscher, D., Maan, Z. N., Hu, M. S., Thor, D. 2020

    Abstract

    Similar to chronic wounds, skin aging is characterized by dysfunction of key cellular regulatory pathways. The hypoxia-inducible factor-1 alpha (HIF-1α) pathway was linked to both conditions. Recent evidence suggests that modulating this pathway can rejuvenate aged fibroblasts and improve skin regeneration. Here, we describe the application of a novel HIF stimulating factor (HSF™)-based formulation for skin rejuvenation.Over a period of 6 weeks using a split-face study design, the effects on skin surface profile, skin moisture, and transepidermal water loss were determined in 32 female subjects (mean age 54, range 32-67 years) by Fast Optical in vivo Topometry of Human Skin (FOITSHD ), Corneometer, and Tewameter measurements. In addition, a photo documentation was performed for assessment by an expert panel and a survey regarding subject satisfaction was conducted.No negative skin reactions of dermatological relevance were documented for the test product. A significant reduction in skin roughness could be demonstrated. The clinical evaluation of the images using a validated method confirmed significant improvement of wrinkles, in particular of fine wrinkles, lip wrinkles, and crow's feet. A significant skin moisturizing effect was detected while skin barrier function was preserved. The HSF™-based skin care formulation resulted in a self-reported 94% satisfaction rate.With no negative skin reactions and highly significant effects on skin roughness, wrinkles, and moisturization, the HSF™-based skin care formulation achieved very satisfying outcomes in this clinical trial. Given the favorable results, this approach represents a promising innovation in aesthetic and regenerative medicine.

    View details for DOI 10.1111/jocd.13356

    View details for PubMedID 32306525

  • Macrophage Subpopulation Dynamics Shift following Intravenous Infusion of Mesenchymal Stromal Cells. Molecular therapy : the journal of the American Society of Gene Therapy Kosaric, N., Srifa, W., Bonham, C. A., Kiwanuka, H., Chen, K., Kuehlmann, B. A., Maan, Z. N., Noishiki, C., Porteus, M. H., Longaker, M. T., Gurtner, G. C. 2020

    Abstract

    Intravenous infusion of mesenchymal stromal cells (MSCs) is thought to be a viable treatment for numerous disorders. Although the intrinsic immunosuppressive ability of MSCs has been credited for this therapeutic effect, their exact impact on endogenous tissue-resident cells following delivery has not been clearly characterized. Moreover, multiple studies have reported pulmonary sequestration of MSCs upon intravenous delivery. Despite substantial efforts to improve MSC homing, it remains unclear whether MSC migration to the site of injury is necessary to achieve a therapeutic effect. Using a murine excisional wound healing model, we offer an explanation of how sequestered MSCs improve healing through their systemic impact on macrophage subpopulations. We demonstrate that infusion of MSCs leads to pulmonary entrapment followed by rapid clearance, but also significantly accelerates wound closure. Using single-cell RNA sequencing of the wound, we show that following MSC delivery, innate immune cells, particularly macrophages, exhibit distinctive transcriptional changes. We identify the appearance of a pro-angiogenic CD9+ macrophage subpopulation, whose induction is mediated by several proteins secreted by MSCs, including COL6A1, PRG4, and TGFB3. Our findings suggest that MSCs do not need to act locally to induce broad changes in the immune system and ultimately treat disease.

    View details for DOI 10.1016/j.ymthe.2020.05.022

    View details for PubMedID 32531238

  • Cryopreserved human skin allografts promote angiogenesis and dermal regeneration in a murine model. International wound journal Henn, D., Chen, K., Maan, Z. N., Greco, A. H., Moortgat Illouz, S. E., Bonham, C. A., Barrera, J. A., Trotsyuk, A. A., Padmanabhan, J., Momeni, A., Wan, D. C., Nguyen, D., Januszyk, M., Gurtner, G. C. 2020

    Abstract

    Cryopreserved human skin allografts (CHSAs) are used for the coverage of major burns when donor sites for autografts are insufficiently available and have clinically shown beneficial effects on chronic non-healing wounds. However, the biologic mechanisms behind the regenerative properties of CHSA remain elusive. Furthermore, the impact of cryopreservation on the immunogenicity of CHSA has not been thoroughly investigated and raised concerns with regard to their clinical application. To investigate the importance and fate of living cells, we compared cryopreserved CHSA with human acellular dermal matrix (ADM) grafts in which living cells had been removed by chemical processing. Both grafts were subcutaneously implanted into C57BL/6 mice and explanted after 1, 3, 7, and 28 days (n = 5 per group). A sham surgery where no graft was implanted served as a control. Transmission electron microscopy (TEM) and flow cytometry were used to characterise the ultrastructure and cells within CHSA before implantation. Immunofluorescent staining of tissue sections was used to determine the immune reaction against the implanted grafts, the rate of apoptotic cells, and vascularisation as well as collagen content of the overlaying murine dermis. Digital quantification of collagen fibre alignment on tissue sections was used to quantify the degree of fibrosis within the murine dermis. A substantial population of live human cells with intact organelles was identified in CHSA prior to implantation. Subcutaneous pockets with implanted xenografts or ADMs healed without clinically apparent rejection and with a similar cellular immune response. CHSA implantation largely preserved the cellularity of the overlying murine dermis, whereas ADM was associated with a significantly higher rate of cellular apoptosis, identified by cleaved caspase-3 staining, and a stronger dendritic cell infiltration of the murine dermis. CHSA was found to induce a local angiogenic response, leading to significantly more vascularisation of the murine dermis compared with ADM and sham surgery on day 7. By day 28, aggregate collagen-1 content within the murine dermis was greater following CHSA implantation compared with ADM. Collagen fibre alignment of the murine dermis, correlating with the degree of fibrosis, was significantly greater in the ADM group, whereas CHSA maintained the characteristic basket weave pattern of the native murine dermis. Our data indicate that CHSAs promote angiogenesis and collagen-1 production without eliciting a significant fibrotic response in a xenograft model. These findings may provide insight into the beneficial effects clinically observed after treatment of chronic wounds and burns with CHSA.

    View details for DOI 10.1111/iwj.13349

    View details for PubMedID 32227459

  • Plastic Surgery Research: A Means to an End? Plastic and reconstructive surgery Oliver, J. D., Hu, A. C., Maan, Z. N., Hu, M. S. 2020; 145 (4): 890e–892e

    View details for DOI 10.1097/PRS.0000000000006693

    View details for PubMedID 32221266

  • Innovation in Plastic Surgery: A Call for Re-Emergence of the Surgeon-Scientist. Plastic and reconstructive surgery Oliver, J. D., Hu, A. C., Maan, Z. N., Hu, M. S. 2020; 145 (4): 892e

    View details for DOI 10.1097/PRS.0000000000006694

    View details for PubMedID 32221267

  • Plastic Surgery Research: A Means to an End? Plastic and reconstructive surgery Oliver, J. D., Hu, A. C., Maan, Z. N., Hu, M. S. 2020

    View details for DOI 10.1097/PRS.0000000000006693

    View details for PubMedID 31977976

  • The association of burn patient volume with patient safety indicators and mortalityin the US. Burns : journal of the International Society for Burn Injuries Sheckter, C. C., Pham, C., Rochlin, D., Maan, Z. N., Karanas, Y., Curtin, C. 2019

    Abstract

    INTRODUCTION: Clinical volume has been associated with rate of complications and mortality for various conditions and procedures. We aim to analyze the relationship between annual hospital burn admission, patient safety indicators (PSI), line infections, and inpatient mortality. We hypothesize that high facility volume will correlate with better outcomes.METHODS: All burn admissions with complete data for total body surface area (TBSA) and depth were extracted from the Nationwide Inpatient Sample from 2002-2011. Predictor variables included age, gender, comorbidities, %TBSA, burn depth, and inhalation injury. Surgically relevant PSIs were drawn from the Healthcare Cost & Utilization Project and included: sepsis, venous thromboembolic disease, hemorrhage, pneumonia, and wound complications. Outcomes were analyzed with regression models.RESULTS: Of the 57,468 encounters included, 3.1% died, 6.3% experienced >1 PSI event, and 0.3% experienced a catheter-associated urinary tract infections or central line associated blood stream infections. The most frequent PSI was pneumonia followed by sepsis and VTE. Annual hospital burn admission volume was independently associated with decreased odds of mortality (OR 0.99, 95% CI 0.99-0.99, p<0.001) and PSIs (OR 0.99, 95% CI 0.99-0.99, p=0.031). There was no significant correlation with line infections. In both mortality and PSI models, age, %TBSA, inhalation injuries, and Elixhauser comorbidity score were significantly associated with adverse outcomes (p<0.05).CONCLUSION: There was a significant association between higher hospital volume and decreased likelihood of patient safety indicators and mortality. There was no observed relationship with line infections. These findings could inform future verification policies of US burn centers.

    View details for DOI 10.1016/j.burns.2019.11.009

    View details for PubMedID 31843281

  • Digit Tip Regeneration Relies on Germ Layer Restricted Wnt and Hedgehog Signaling Maan, Z. N., Januszyk, M., Rinkevich, Y., Weissman, I., Gurtner, G. ELSEVIER SCIENCE INC. 2019: S220–S221
  • Homelessness and Inpatient Burn Outcomes in the United States JOURNAL OF BURN CARE & RESEARCH Kiwanuka, H., Maan, Z. N., Rochlin, D., Curtin, C., Karanas, Y., Sheckter, C. C. 2019; 40 (5): 633–38
  • Optimising management of self-inflicted burns: a retrospective review. Journal of wound care Houschyar, K. S., Tapking, C., Duscher, D., Maan, Z. N., Sheckter, C. C., Rein, S., Chelliah, M. P., Nietzschmann, I., Weissenberg, K., Reumuth, G., Schulz, T., Branski, L. K., Siemers, F. 2019; 28 (6): 317–22

    Abstract

    OBJECTIVE: Self-inflicted burns typically result in extensive injuries requiring intensive care and attention in a specialised burn unit. Burn units should be familiar with the optimal management of self-inflicted burns, including the psychological and psychiatric treatment. This paper describes the experiences of managing these challenging injuries in a German burn centre.METHODS: A retrospective review of patients with self-inflicted burns admitted to the burn centre between 2000 and 2017. Demographics, details of injury, presence of psychiatric disorder, clinical course, operative management and patient outcomes were recorded and compared with a control group without self-inflicted burns. Outcome measures included graft take rate, complications and need for further surgery.RESULTS: There were a total of 2055 burn patient admissions, with 17 cases (0.8%) of self-inflicted burns. The mean age was 36±11 years with an mean percentage total body surface area (%TBSA) burned of 43.5±22.5% which was not significantly different from the control group (p=0.184). Schizophrenia and personality disorder were the most common diagnoses in the self-inflicted burns patients (n=11; 65%). Of these, four had sustained previous self-inflicted burns. Length of hospital stay was significantly longer in the self-inflicted burn group than in the control group (49.0±16.7 days, respectively, p=0.002).CONCLUSION: Attempted suicide by self-inflicted burns represents <1% of burn admissions. This population demonstrates a high incidence of prior psychiatric disorders. Successful treatment includes multidisciplinary management of acute medical, surgical, and psychiatric care.

    View details for DOI 10.12968/jowc.2019.28.6.317

    View details for PubMedID 31166860

  • Homelessness and Inpatient Burn Outcomes in the United States. Journal of burn care & research : official publication of the American Burn Association Kiwanuka, H., Maan, Z., Rochlin, D., Curtin, C., Karanas, Y., Sheckter, C. C. 2019

    Abstract

    INTRODUCTION: Burn injuries are common in the homeless population. Little is known regarding whether homeless patients experience different outcomes when admitted for burns. We aim to 1) characterize the admitted homeless burn population, and 2) investigate differences in inpatient outcomes between the homeless and non-homeless populations.METHODS: A retrospective cohort study was performed utilizing the Nationwide Inpatient Sample. Adult patients with complete data for burn characteristics were extracted. Variables included demographic, burn, and facility characteristics. Homelessness was identified with International Classification of Disease 9th edition codes. Outcomes were modeled with regression analysis and included length of stay, total operations, charges, disposition, and patient safety indicators.RESULTS: 43,872 encounters were included of which 0.76% were homeless. Homeless encounters were more likely to be male (p<0.001) and Medicaid-insured (p<0.001). Flame and frostbite injuries were more likely (p<0.001), and the mean %TBSA was smaller (15.0 versus 16.8, p<0.001). After adjustment, homeless patients had greater lengths of stay (11.5 vs. 9.6, p=0.046), greater charges ($73,597 vs. $66,909, p=0.030), fewer operations (p=0.016), and three times higher likelihood leaving against medical advice (p=0.002). There was no difference in patient safety indicators or mortality.CONCLUSION: Homeless burn admissions represent a unique cohort that carries a higher comorbidity burden and experiences longer lengths of stay with greater difficulty in disposition. Ironically, these patients accumulate more charges with limited means to pay. Even though no differences were observed in patient safety indicators or mortality, further research is needed to understand how the challenges within this population affect their recovery.

    View details for PubMedID 30938433

  • Age-associated intracellular superoxide dismutase deficiency potentiates dermal fibroblast dysfunction during wound healing EXPERIMENTAL DERMATOLOGY Fujiwara, T., Dohi, T., Maan, Z. N., Rustad, K. C., Kwon, S., Padmanabhan, J., Whittam, A. J., Suga, H., Duscher, D., Rodrigues, M., Gurtner, G. C. 2019; 28 (4): 485–92

    View details for DOI 10.1111/exd.13404

    View details for Web of Science ID 000468323100023

  • In Vivo Models for the Study of Fibrosis ADVANCES IN WOUND CARE Padnnanabhan, J., Maan, Z. N., Kwon, S., Kosaraju, R., Bonham, C. A., Gurtner, G. C. 2019
  • Small molecule inhibition of dipeptidyl peptidase-4 enhances bone marrow progenitor cell function and angiogenesis in diabetic wounds TRANSLATIONAL RESEARCH Whittam, A. J., Maan, Z. N., Duscher, D., Barrera, J. A., Hu, M. S., Fischer, L. H., Khong, S., Kwon, S., Wong, V. W., Walmsley, G. G., Giacco, F., Januszyk, M., Brownlee, M., Longaker, M. T., Gurtner, G. C. 2019; 205: 51–63
  • Wounds Inhibit Tumor Growth In Vivo. Annals of surgery Hu, M. S., Maan, Z. N., Leavitt, T., Hong, W. X., Rennert, R. C., Marshall, C. D., Borrelli, M. R., Zhu, T. N., Esquivel, M., Zimmermann, A., McArdle, A., Chung, M. T., Foster, D. S., Jones, R. E., Gurtner, G. C., Giaccia, A. J., Lorenz, H. P., Weissman, I. L., Longaker, M. T. 2019

    Abstract

    OBJECTIVE: The aim of this study was to determine the interaction of full thickness excisional wounds and tumors in vivo.SUMMARY OF BACKGROUND DATA: Tumors have been described as wounds that do not heal due to similarities in stromal composition. On the basis of observations of slowed tumor growth after ulceration, we hypothesized that full thickness excisional wounds would inhibit tumor progression in vivo.METHODS: To determine the interaction of tumors and wounds, we developed a tumor xenograft/allograft (human head and neck squamous cell carcinoma SAS/mouse breast carcinoma 4T1) wound mouse model. We examined tumor growth with varying temporospatial placement of tumors and wounds or ischemic flap. In addition, we developed a tumor/wound parabiosis model to understand the ability of tumors and wounds to recruit circulating progenitor cells.RESULTS: Tumor growth inhibition by full thickness excisional wounds was dose-dependent, maintained by sequential wounding, and relative to distance. This effect was recapitulated by placement of an ischemic flap directly adjacent to a xenograft tumor. Using a parabiosis model, we demonstrated that a healing wound was able to recruit significantly more circulating progenitor cells than a growing tumor. Tumor inhibition by wound was unaffected by presence of an immune response in an immunocompetent model using a mammary carcinoma. Utilizing functional proteomics, we identified 100 proteins differentially expressed in tumors and wounds.CONCLUSION: Full thickness excisional wounds have the ability to inhibit tumor growth in vivo. Further research may provide an exact mechanism for this remarkable finding and new advances in wound healing and tumor biology.

    View details for PubMedID 30829705

  • Increasing ambulatory treatment of pediatric minor burns-The emerging paradigm for burn care in children Sheckter, C. C., Kiwanuka, H., Maan, Z., Pirrotta, E., Curtin, C., Wang, N. E. ELSEVIER SCI LTD. 2019: 165–72
  • Five Years Experience With Meek Grafting in the Management of Extensive Burns in an Adult Burn Center PLASTIC SURGERY Houschyar, K., Tapking, C., Nietzschmann, I., Rein, S., Weissenberg, K., Chelliah, M., Duscher, D., Maan, Z., Philipps, H., Sheckter, C., Reichelt, B., Branski, L., Siemers, F. 2019; 27 (1): 44–48

    Abstract

    In extensive burn injuries with lack of donor sites for skin grafting, the Meek technique of skin expansion can be an efficient and effective method in covering extensive wounds. The aim of this retrospective study was to present our experience with the Meek technique of grafting.We performed a retrospective analysis of patients from our burn center who underwent Meek grafting between 2012 and 2016. Demographics, burn details, clinical course, operative management, and outcomes were collected and analyzed from patient records and operative notes. Outcome measures, including graft take rate, complications and need for further surgery, were recorded.Twelve patients had Meek grafting. The average age was 38 years (range: 15-66). The average percent total body surface area burned was 54.3% (range: 31%-77%). Eighty-three percent of grafted areas healed well, and no regrafting was necessary. In the remaining 17%, infection and hematoma were the leading cause of graft failure.Meek grafting constitutes a rapid and efficient surgical approach for the skin coverage of extensive full-thickness burn injuries with limited autograft donor sites.

    View details for PubMedID 30854361

  • Digit Tip Injuries: Current Treatment and Future Regenerative Paradigms STEM CELLS INTERNATIONAL Miller, T. J., Deptula, P. L., Buncke, G. M., Maan, Z. N. 2019; 2019
  • Wnt Pathway in Bone Repair and Regeneration - What Do We Know So Far FRONTIERS IN CELL AND DEVELOPMENTAL BIOLOGY Houschyar, K. S., Tapking, C., Borrelli, M. R., Popp, D., Duscher, D., Maan, Z. N., Chelliah, M. P., Li, J., Harati, K., Wallner, C., Rein, S., Pfoerringer, D., Reumuth, G., Grieb, G., Mouraret, S., Dadras, M., Wagner, J. M., Cha, J. Y., Siemers, F., Lehnhardt, M., Behr, B. 2019; 6: 170

    Abstract

    Wnt signaling plays a central regulatory role across a remarkably diverse range of functions during embryonic development, including those involved in the formation of bone and cartilage. Wnt signaling continues to play a critical role in adult osteogenic differentiation of mesenchymal stem cells. Disruptions in this highly-conserved and complex system leads to various pathological conditions, including impaired bone healing, autoimmune diseases and malignant degeneration. For reconstructive surgeons, critically sized skeletal defects represent a major challenge. These are frequently associated with significant morbidity in both the recipient and donor sites. The Wnt pathway is an attractive therapeutic target with the potential to directly modulate stem cells responsible for skeletal tissue regeneration and promote bone growth, suggesting that Wnt factors could be used to promote bone healing after trauma. This review summarizes our current understanding of the essential role of the Wnt pathway in bone regeneration and repair.

    View details for PubMedID 30666305

  • Cognitive Independence In Plastic Surgery Training: the Value of Professional Development. Plastic and reconstructive surgery Sheckter, C. C., Maan, Z. N., Chang, J. 2019

    View details for PubMedID 31021905

  • In Vivo Models for the Study of Fibrosis. Advances in wound care Padmanabhan, J., Maan, Z. N., Kwon, S. H., Kosaraju, R., Bonham, C. A., Gurtner, G. C. 2019; 8 (12): 645–54

    Abstract

    Significance: Fibrosis and scar formation pose a substantial physiological and psychological burden on patients and a significant public health burden on the economy, estimated to be up to $12 billion a year. Fibrosis research is heavily reliant on in vivo models, but variations in animal models and differences between animal and human fibrosis necessitates careful selection of animal models to study fibrosis. There is also an increased need for improved animal models that recapitulate human pathophysiology. Recent Advances: Several murine and porcine models, including xenograft, drug-induced fibrosis, and mechanical load-induced fibrosis, for different types of fibrotic disease have been described in the literature. Recent findings have underscored the importance of mechanical forces in the pathophysiology of scarring. Critical Issues: Differences in skin, properties of subcutaneous tissue, and modes of fibrotic healing in animal models and humans provide challenges toward investigating fibrosis with in vivo models. While porcine models are typically better suited to study cutaneous fibrosis, murine models are preferred because of the ease of handling and availability of transgenic strains. Future Directions: There is a critical need to develop novel murine models that recapitulate the mechanical cues influencing fibrosis in humans, significantly increasing the translational value of fibrosis research. We advocate a translational pipeline that begins in mouse models with modified biomechanical environments for foundational molecular and cellular research before validation in porcine models that closely mimic the human condition.

    View details for DOI 10.1089/wound.2018.0909

    View details for PubMedID 31827979

    View details for PubMedCentralID PMC6904938

  • Digit Tip Injuries: Current Treatment and Future Regenerative Paradigms. Stem cells international Miller, T. J., Deptula, P. L., Buncke, G. M., Maan, Z. N. 2019; 2019: 9619080

    Abstract

    Over the past several decades there has been a profound increase in the understanding of tissue regeneration, driven largely by the observance of the tremendous regenerative capacity in lower order life forms, such as hydra and urodeles. However, it is known that humans and other mammals retain the ability to regenerate the distal phalanges of the digits after amputation. Despite the increased knowledge base on model organisms regarding regenerative paradigms, there is a lack of application of regenerative medicine techniques in clinical practice in regard to digit tip injury. Here, we review the current understanding of digit tip regeneration and discuss gaps that remain in translating regenerative medicine into clinical treatment of digit amputation.

    View details for PubMedID 30805012

  • Optimization of transdermal deferoxamine leads to enhanced efficacy in healing skin wounds. Journal of controlled release : official journal of the Controlled Release Society Duscher, D., Trotsyuk, A. A., Maan, Z. N., Kwon, S. H., Rodrigues, M., Engel, K., Stern-Buchbinder, Z. A., Bonham, C. A., Whittam, A. J., Barrera, J., Hu, M. S., Inayathullah, M., Rajadas, J., Gurtner, G. C. 2019

    Abstract

    Chronic wounds remain a significant burden to both the healthcare system and individual patients, indicating an urgent need for new interventions. Deferoxamine (DFO), an iron-chelating agent clinically used to treat iron toxicity, has been shown to reduce oxidative stress and increase hypoxia-inducible factor-1 alpha (HIF-1α) activation, thereby promoting neovascularization and enhancing regeneration in chronic wounds. However due to its short half-life and adverse side effects associated with systemic absorption, there is a pressing need for targeted DFO delivery. We recently published a preclinical proof of concept drug delivery system (TDDS) which showed that transdermally applied DFO is effective in improving chronic wound healing. Here we present an enhanced TDDS (eTDDS) comprised exclusively of FDA-compliant constituents to optimize drug release and expedite clinical translation. We evaluate the eTDDS to the original TDDS and compare this with other commonly used delivery methods including DFO drip-on and polymer spray applications. The eTDDS displayed excellent physicochemical characteristics and markedly improved DFO delivery into human skin when compared to other topical application techniques. We demonstrate an accelerated wound healing response with the eTDDS treatment resulting in significantly increased wound vascularity, dermal thickness, collagen deposition and tensile strength. Together, these findings highlight the immediate clinical potential of DFO eTDDS to treating diabetic wounds. Further, the topical drug delivery platform has important implications for targeted pharmacologic therapy of a wide range of cutaneous diseases.

    View details for DOI 10.1016/j.jconrel.2019.07.009

    View details for PubMedID 31299261

  • Cognitive Independence in Plastic Surgery Training: The Value of Professional Development. Plastic and reconstructive surgery Sheckter, C. C., Maan, Z. N., Chang, J. 2019; 144 (1): 153e–154e

    View details for DOI 10.1097/PRS.0000000000005762

    View details for PubMedID 31246858

  • Trends and inpatient outcomes for palliative care services in major burn patients: A 10-year analysis of the nationwide inpatient sample BURNS Sheckter, C. C., Hung, K. S., Rochlin, D., Maan, Z., Karanas, Y., Curtin, C. 2018; 44 (8): 1903–9
  • Small molecule inhibition of dipeptidyl peptidase-4 enhances bone marrow progenitor cell function and angiogenesis in diabetic wounds. Translational research : the journal of laboratory and clinical medicine Whittam, A. J., Maan, Z. N., Duscher, D., Barrera, J. A., Hu, M. S., Fischer, L. H., Khong, S., Kwon, S. H., Wong, V. W., Walmsley, G. G., Giacco, F., Januszyk, M., Brownlee, M., Longaker, M. T., Gurtner, G. C. 2018

    Abstract

    In diabetes, stromal cell-derived factor-1 (SDF-1) expression and progenitor cell recruitment are reduced. Dipeptidyl peptidase-4 (DPP-4) inhibits SDF-1 expression and progenitor cell recruitment. Here we examined the impact of the DPP-4 inhibitor, MK0626, on progenitor cell kinetics in the context of wound healing. Wildtype (WT) murine fibroblasts cultured under high-glucose to reproduce a diabetic microenvironment were exposed to MK0626, glipizide, or no treatment, and SDF-1 expression was measured with ELISA. Diabetic mice received MK0626, glipizide, or no treatment for 6 weeks and then were wounded. Immunohistochemistry was used to quantify neovascularization and SDF-1 expression. Gene expression was measured at the RNA and protein level using quantitative polymerase chain reaction and ELISA, respectively. Flow cytometry was used to characterize bone marrow-derived mesenchymal progenitor cell (BM-MPC) population recruitment to wounds. BM-MPC gene expression was assayed using microfluidic single cell analysis. WT murine fibroblasts exposed to MK0626 demonstrated increased SDF-1 expression. MK0626 treatment significantly accelerated wound healing and increased wound vascularity, SDF-1 expression, and dermal thickness in diabetic wounds. MK0626 treatment increased the number of BM-MPCs present in bone marrow and in diabetic wounds. MK0626 had no effect on BM-MPC population dynamics. BM-MPCs harvested from MK0626-treated mice exhibited increased chemotaxis in response to SDF-1 when compared to diabetic controls. Treatment with a DPP-4 inhibitor significantly improved wound healing, angiogenesis, and endogenous progenitor cell recruitment in the setting of diabetes.

    View details for PubMedID 30452888

  • Single Stage Repair of #30 Facial Cleft with Bone Morphogenic Protein PLASTIC AND RECONSTRUCTIVE SURGERY-GLOBAL OPEN Sheckter, C. C., Mittermiller, P., Hung, K., Maan, Z., Rochlin, D., Menard, R. M. 2018; 6 (11)
  • Increasing ambulatory treatment of pediatric minor burns-The emerging paradigm for burn care in children. Burns : journal of the International Society for Burn Injuries Sheckter, C. C., Kiwanuka, H., Maan, Z., Pirrotta, E., Curtin, C., Wang, N. E. 2018

    Abstract

    INTRODUCTION: Innovations in topical burn treatment along with a drive toward value-based care are steering burn care to the outpatient setting. Little is known regarding what characteristics predict outpatient treatment of pediatric minor burns and whether there is a temporal trend toward this treatment paradigm.METHODS: A retrospective cohort study was performed using California's Office of Statewide Health Planning and Development linked emergency department and inpatient database (2005-2013). All patients under 18years of age with a primary burn diagnosis were extracted. Using patient and facility level variables, we used regression modeling to evaluate predictors of outpatient burn treatment and temporal trends.RESULTS: There were 16,480 pediatric minor burn encounters during the period. 56.4% were male, 85.3% had <10% total body surface area (TBSA), 76.3% were scald or contact, and 77.3% were at deepest depth 2nd degree. Multiple variables predicted an increased likelihood of discharge home including older age(p<0.001), smaller TBSA(p<0.001), and superficial/partial thickness burns(<0.001). Children of Hispanic and Black race were less likely to be discharged home compared to White and Asian peers(p=<0.001). On Poisson modeling, the incidence rate ratio over the 9-year period for home discharge was 1.004 (95% CI 1.001-1.008, p=0.032).CONCLUSION: Older patients and those with more superficial burns were more likely to be treated as outpatients. Black and non-white Hispanic race was associated with inpatient admission. There is a growing trend toward ambulatory treatment of minor burns in the pediatric population. Further research is needed to assess whether outpatient treatment of pediatric minor burns results in greater readmissions.

    View details for PubMedID 30236815

  • Trends and inpatient outcomes for palliative care services in major burn patients: A 10-year analysis of the nationwide inpatient sample. Burns : journal of the International Society for Burn Injuries Sheckter, C. C., Hung, K., Rochlin, D., Maan, Z., Karanas, Y., Curtin, C. 2018

    Abstract

    INTRODUCTION: Despite advances in critical care and the surgical management of major burns, highly moribund patients are unlikely to survive. Little is known regarding the utilization and effects of palliative care services in this population.METHODS: All major burn hospitalizations were identified within the Nationwide Inpatient Sample. Patients were characterized by burn, demographic, facility, and diseases factors. Palliative care services were identified with International Classification Disease 9th edition code V6.67. Temporal trends were assessed with Poisson modeling. Inpatient mortality and death without surgical intervention were assessed with logistic regression. Outcomes were stratified by modified Baux scores.RESULTS: 7424 major burns were included; 1.9% received palliative care services. Patients receiving palliation had a mean age of 63.6 years (SD 19.6), mean total body surface area of 62.2% (SD 24.9%), and mean modified Baux score of 127.1 (SD 26.7). Adjusting for covariates, the incidence rate ratio was 1.42 over the 10-year period (95% CI, 1.31-1.54, p<0.001). Independent predictors of palliative consultations included older age, larger burns, deeper burns, and higher Elixhauser comorbidity score. Among patients with modified Baux scores between 100-153, those receiving palliative care services were significantly more likely to die without surgery, OR 3.24 (95% CI 1.13-10.39, p=0.029), with no significant difference in mortality, OR 11.72 (95% CI 0.87-22.57, p=0.051) CONCLUSION AND RELEVANCE: Palliative care services were increasingly used during the study period. Palliative care services in highly moribund burn patients do not impact survival and may decrease the likelihood of surgical intervention in select patients.

    View details for PubMedID 30115531

  • Role of Wnt signaling during inflammation and sepsis: A review of the literature INTERNATIONAL JOURNAL OF ARTIFICIAL ORGANS Houschyar, K., Chelliah, M. P., Rein, S., Maan, Z. N., Weissenberg, K., Duscher, D., Branski, L. K., Siemers, F. 2018; 41 (5): 247–53

    Abstract

    Despite the development of modern intensive care and new antimicrobial agents, the mortality of patients with severe sepsis and septic shock remains high. Systemic inflammation is a consequence of activation of the innate immune system. It is characterized by the intravascular release of proinflammatory cytokines and other vasoactive mediators, with concurrent activation of innate immune cells. The Wnt signaling pathway plays a critical role in the development of multicellular organisms. Abnormal Wnt signaling has been associated with many human diseases, ranging from inflammation and degenerative diseases to cancer. This article reviews the accumulating evidence that the Wnt signaling pathway plays a distinct role in inflammation and sepsis.

    View details for PubMedID 29562813

  • Pathway Analysis of Gene Expression in Murine Fetal and Adult Wounds ADVANCES IN WOUND CARE Hu, M. S., Hong, W., Januszyk, M., Walmsley, G. G., Luan, A., Maan, Z. N., Moshrefi, S., Tevlin, R., Wan, D. C., Gurtner, G. C., Longaker, M. T., Lorenz, H. 2018
  • An Improved Humanized Mouse Model for Excisional Wound Healing Using Double Transgenic Mice ADVANCES IN WOUND CARE Hu, M. S., Cheng, J., Borrelli, M. R., Leavitt, T., Walmsley, G. G., Zielins, E. R., Hong, W., Cheung, A. M., Duscher, D., Maan, Z. N., Irizarry, D. M., Stephan, B., Parsa, F., Wan, D. C., Gurtner, G. C., Lorenz, H., Longaker, M. T. 2018; 7 (1): 11–17

    Abstract

    Objective: Splinting full-thickness cutaneous wounds in mice has allowed for a humanized model of wound healing. Delineating the epithelial edge and assessing time to closure of these healing wounds via macroscopic visualization have remained a challenge. Approach: Double transgenic mice were created by crossbreeding K14-Cre and ROSAmT/mG reporter mice. Full-thickness excisional wounds were created in K14-Cre/ROSAmT/mG mice (n = 5) and imaged using both normal and fluorescent light on the day of surgery, and every other postoperative day (POD) until wound healing was complete. Ten blinded observers analyzed a series of images from a single representative healing wound, taken using normal or fluorescent light, to decide the POD when healing was complete. K14-Cre/ROSAmT/mG mice (n = 4) were subsequently sacrificed at the four potential days of rated wound closure to accurately determine the histological point of wound closure using microscopic fluorescence imaging. Results: Average time to wound closure was rated significantly longer in the wound series images taken using normal light, compared with fluorescent light (mean POD 13.6 vs. 11.6, *p = 0.008). Fluorescence imaging of histological samples indicated that reepithelialization was complete at 12 days postwounding. Innovation: We describe a novel technique, using double transgenic mice K14-Cre/ROSAmT/mG and fluorescence imaging, to more accurately determine the healing time of wounds in mice upon macroscopic evaluation. Conclusion: The accuracy by which wound healing can be macroscopically determined in vivo in mouse models of wound healing is significantly enhanced using K14-Cre/ROSAmT/mG double transgenic mice and fluorescence imaging.

    View details for PubMedID 29344430

  • Fibrin Glue Enhances Adipose-Derived Stromal Cell Cytokine Secretion and Survival Conferring Accelerated Diabetic Wound Healing. Stem cells international Hopfner, U., Aitzetmueller, M. M., Neßbach, P., Hu, M. S., Machens, H. G., Maan, Z. N., Duscher, D. 2018; 2018: 1353085

    Abstract

    Although chronic wounds are a major personal and economic burden, treatment options are still limited. Among those options, adipose-derived stromal cell- (ASC-) based therapies rank as a promising approach but are restricted by the harsh wound environment. Here we use a commercially available fibrin glue to provide a deliverable niche for ASCs in chronic wounds.To investigate the in vitro effect of fibrin glue, cultivation experiments were performed and key cytokines for regeneration were quantified. By using an established murine chronic diabetic wound-healing model, we evaluated the influence of fibrin glue spray seeding on cell survival (In Vivo Imaging System, IVIS), wound healing (wound closure kinetics), and neovascularization of healed wounds (CD31 immunohistochemistry).Fibrin glue seeding leads to a significantly enhanced secretion of key cytokines (SDF-1, bFGF, and MMP-2) of human ASCs in vitro. IVIS imaging showed a significantly prolonged murine ASC survival in diabetic wounds and significantly accelerated complete wound closure in the fibrin glue seeded group. CD31 immunohistochemistry revealed significantly more neovascularization in healed wounds treated with ASCs spray seeded in fibrin glue vs. ASC injected into the wound bed.Although several vehicles have shown to successfully act as cell carrier systems in preclinical trials, regulatory issues have prohibited clinical usage for chronic wounds. By demonstrating the ability of fibrin glue to act as a carrier vehicle for ASCs, while simultaneously enhancing cellular regenerative function and viability, this study is a proponent of clinical translation for ASC-based therapies.

    View details for PubMedID 30662467

  • Pathway Analysis of Gene Expression in Murine Fetal and Adult Wounds. Advances in wound care Hu, M. S., Hong, W. X., Januszyk, M., Walmsley, G. G., Luan, A., Maan, Z. N., Moshrefi, S., Tevlin, R., Wan, D. C., Gurtner, G. C., Longaker, M. T., Lorenz, H. P. 2018; 7 (8): 262–75

    Abstract

    Objective: In early gestation, fetal wounds heal without fibrosis in a process resembling regeneration. Elucidating this remarkable mechanism can result in tremendous benefits to prevent scarring. Fetal mouse cutaneous wounds before embryonic day (E)18 heal without scar. Herein, we analyze expression profiles of fetal and postnatal wounds utilizing updated gene annotations and pathway analysis to further delineate between repair and regeneration. Approach: Dorsal wounds from time-dated pregnant BALB/c mouse fetuses and adult mice at various time points were collected. Total RNA was isolated and microarray analysis was performed using chips with 42,000 genes. Significance analysis of microarrays was utilized to select genes with >2-fold expression differences with a false discovery rate of <2. Enrichment analysis was performed on significant genes to identify differentially expressed pathways. Results: Our analysis identified 471 differentially expressed genes in fetal versus adult wounds following injury. Utilizing enrichment analysis of significant genes, we identified the top 20 signaling pathways that were upregulated and downregulated at 1 and 12 h after injury. At 24 h after injury, we discovered 18 signaling pathways upregulated in adult wounds and 11 pathways upregulated in fetal wounds. Innovation: These novel target genes and pathways may reveal repair mechanisms of the early fetus that promote regeneration over fibrosis. Conclusion: Our microarray analysis recognizes hundreds of possible genes as candidates for regulators of scarless versus scarring wound repair. Enrichment analysis reveals 109 signaling pathways related to fetal scarless wound healing.

    View details for PubMedID 30087802

  • Fibrin Glue Enhances Adipose-Derived Stromal Cell Cytokine Secretion and Survival Conferring Accelerated Diabetic Wound Healing STEM CELLS INTERNATIONAL Hopfner, U., Aitzetmueller, M. M., Nessbach, P., Hu, M. S., Machens, H., Maan, Z. N., Duscher, D. 2018
  • Single Stage Repair of #30 Facial Cleft with Bone Morphogenic Protein. Plastic and reconstructive surgery. Global open Sheckter, C. C., Mittermiller, P., Hung, K., Maan, Z., Rochlin, D., Menard, R. M. 2018; 6 (11): e1937

    Abstract

    Tessier #30 clefts (median mandibular clefts) represent a spectrum of deformities ranging from a minor cleft in the lower lip to complete clefts of the mandible involving the tongue, lower lip, hyoid bone, thyroid cartilages, and manubrium. Various techniques have been used to address these problems; the most common procedure involving 2 stages: an initial correction of the soft tissue followed by closure of the mandibular cleft at a later date using bone grafting. This approach was subsequently reduced to a single operation, but still required harvesting of autologous bone graft. Here, we describe a modified single-stage operation using human recombinant bone morphogenic protein, avoiding bone graft harvest and allowing for simultaneous treatment of bone and soft tissue.

    View details for PubMedID 30881779

    View details for PubMedCentralID PMC6414095

  • Ultrasound-assisted liposuction provides a source for functional adipose-derived stromal cells CYTOTHERAPY Duscher, D., Maan, Z. N., Luan, A., Aitzetmueller, M. M., Brett, E. A., Atashroo, D., Whittam, A. J., Hu, M. S., Walmsley, G. G., Houschyar, K. S., Schilling, A. F., Machens, H., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2017; 19 (12): 1491–1500

    Abstract

    Regenerative medicine employs human mesenchymal stromal cells (MSCs) for their multi-lineage plasticity and their pro-regenerative cytokine secretome. Adipose-derived mesenchymal stromal cells (ASCs) are concentrated in fat tissue, and the ease of harvest via liposuction makes them a particularly interesting cell source. However, there are various liposuction methods, and few have been assessed regarding their impact on ASC functionality. Here we study the impact of the two most popular ultrasound-assisted liposuction (UAL) devices currently in clinical use, VASER (Solta Medical) and Lysonix 3000 (Mentor) on ASCs.After lipoaspirate harvest and processing, we sorted for ASCs using fluorescent-assisted cell sorting based on an established surface marker profile (CD34+CD31-CD45-). ASC yield, viability, osteogenic and adipogenic differentiation capacity and in vivo regenerative performance were assessed.Both UAL samples demonstrated equivalent ASC yield and viability. VASER UAL ASCs showed higher osteogenic and adipogenic marker expression, but a comparable differentiation capacity was observed. Soft tissue healing and neovascularization were significantly enhanced via both UAL-derived ASCs in vivo, and there was no significant difference between the cell therapy groups.Taken together, our data suggest that UAL allows safe and efficient harvesting of the mesenchymal stromal cellular fraction of adipose tissue and that cells harvested via this approach are suitable for cell therapy and tissue engineering applications.

    View details for PubMedID 28917626

    View details for PubMedCentralID PMC5723208

  • Continuous hemoadsorption with a cytokine adsorber during sepsis - a review of the literature. International journal of artificial organs Houschyar, K. S., Pyles, M. N., Rein, S., Nietzschmann, I., Duscher, D., Maan, Z. N., Weissenberg, K., Philipps, H. M., Strauss, C., Reichelt, B., Siemers, F. 2017; 40 (5): 205-211

    Abstract

    Sepsis is a well-recognized healthcare issue worldwide, ultimately resulting in significant mortality, morbidity and resource utilization during and after critical illness. In its most severe form, sepsis causes multi-organ dysfunction that produces a state of critical illness characterized by severe immune dysfunction and catabolism. Sepsis induces the activation of complement factor via 3 pathways and the release of inflammatory cytokines such as tumor necrosis factor alpha (TNF-α) and interleukin-1beta (IL-1β), resulting in a systemic inflammatory response. The inflammatory cytokines and nitric oxide release induced by sepsis decrease systemic vascular resistance, resulting in profound hypotension. The combination of hypotension and microvascular occlusion results in tissue ischemia and ultimately leads to multiple organ failure. Several clinical and experimental studies have reported that treatment using adsorption of cytokines is beneficial during endotoxemia and sepsis. This review article analyzes the efficacy of CytoSorb® adsorber in reducing the inflammatory response during sepsis. The CytoSorb® adsorber is known to have excellent adsorption rates for inflammatory cytokines such as IL-1β, IL-6, IL-8, IL-10, and TNF-α. Studies have demonstrated that treatment with cytokine adsorbing columns has beneficial effects on the survival rate and inflammatory responses in animal septic models. Additionally, several cases have been reported in which treatment with cytokine adsorbing columns is very effective in hemodynamic stabilization and in preventing organ failure in critically ill patients. Although further investigations and clinical trials are needed, treatment with cytokine adsorbing columns may play an important role in the treatment of sepsis in the near future.

    View details for DOI 10.5301/ijao.5000591

    View details for PubMedID 28525674

  • Reverse Radial Forearm Flap. Plastic and reconstructive surgery. Global open Maan, Z. N., Legrand, A., Long, C., Chang, J. C. 2017; 5 (4)

    Abstract

    Supplemental Digital Content is available in the text.

    View details for DOI 10.1097/GOX.0000000000001287

    View details for PubMedID 28507856

    View details for PubMedCentralID PMC5426875

  • Comparison of the Hydroxylase Inhibitor Dimethyloxalylglycine and the Iron Chelator Deferoxamine in Diabetic and Aged Wound Healing. Plastic and reconstructive surgery Duscher, D., Januszyk, M., Maan, Z. N., Whittam, A. J., Hu, M. S., Walmsley, G. G., Dong, Y., Khong, S. M., Longaker, M. T., Gurtner, G. C. 2017; 139 (3): 695e-706e

    Abstract

    A hallmark of diabetes mellitus is the breakdown of almost every reparative process in the human body, leading to critical impairments of wound healing. Stabilization and activity of the transcription factor hypoxia-inducible factor (HIF)-1α is impaired in diabetes, leading to deficits in new blood vessel formation in response to injury. In this article, the authors compare the effectiveness of two promising small-molecule therapeutics, the hydroxylase inhibitor dimethyloxalylglycine and the iron chelator deferoxamine, for attenuating diabetes-associated deficits in cutaneous wound healing by enhancing HIF-1α activation.HIF-1α stabilization, phosphorylation, and transactivation were measured in murine fibroblasts cultured under normoxic or hypoxic and low-glucose or high-glucose conditions following treatment with deferoxamine or dimethyloxalylglycine. In addition, diabetic wound healing and neovascularization were evaluated in db/db mice treated with topical solutions of either deferoxamine or dimethyloxalylglycine, and the efficacy of these molecules was also compared in aged mice.The authors show that deferoxamine stabilizes HIF-1α expression and improves HIF-1α transactivity in hypoxic and hyperglycemic states in vitro, whereas the effects of dimethyloxalylglycine are significantly blunted under hyperglycemic hypoxic conditions. In vivo, both dimethyloxalylglycine and deferoxamine enhance wound healing and vascularity in aged mice, but only deferoxamine universally augmented wound healing and neovascularization in the setting of both advanced age and diabetes.This first direct comparison of deferoxamine and dimethyloxalylglycine in the treatment of impaired wound healing suggests significant therapeutic potential for topical deferoxamine treatment in ischemic and diabetic disease.

    View details for DOI 10.1097/PRS.0000000000003072

    View details for PubMedID 28234841

    View details for PubMedCentralID PMC5327844

  • Pharmacological rescue of diabetic skeletal stem cell niches. Science translational medicine Tevlin, R., Seo, E. Y., Marecic, O., McArdle, A., Tong, X., Zimdahl, B., Malkovskiy, A., Sinha, R., Gulati, G., Li, X., Wearda, T., Morganti, R., Lopez, M., Ransom, R. C., Duldulao, C. R., Rodrigues, M., Nguyen, A., Januszyk, M., Maan, Z., Paik, K., Yapa, K., Rajadas, J., Wan, D. C., Gurtner, G. C., Snyder, M., Beachy, P. A., Yang, F., Goodman, S. B., Weissman, I. L., Chan, C. K., Longaker, M. T. 2017; 9 (372)

    Abstract

    Diabetes mellitus (DM) is a metabolic disease frequently associated with impaired bone healing. Despite its increasing prevalence worldwide, the molecular etiology of DM-linked skeletal complications remains poorly defined. Using advanced stem cell characterization techniques, we analyzed intrinsic and extrinsic determinants of mouse skeletal stem cell (mSSC) function to identify specific mSSC niche-related abnormalities that could impair skeletal repair in diabetic (Db) mice. We discovered that high serum concentrations of tumor necrosis factor-α directly repressed the expression of Indian hedgehog (Ihh) in mSSCs and in their downstream skeletogenic progenitors in Db mice. When hedgehog signaling was inhibited during fracture repair, injury-induced mSSC expansion was suppressed, resulting in impaired healing. We reversed this deficiency by precise delivery of purified Ihh to the fracture site via a specially formulated, slow-release hydrogel. In the presence of exogenous Ihh, the injury-induced expansion and osteogenic potential of mSSCs were restored, culminating in the rescue of Db bone healing. Our results present a feasible strategy for precise treatment of molecular aberrations in stem and progenitor cell populations to correct skeletal manifestations of systemic disease.

    View details for DOI 10.1126/scitranslmed.aag2809

    View details for PubMedID 28077677

  • Pharmacological rescue of diabetic skeletal stem cell niches SCIENCE TRANSLATIONAL MEDICINE Tevlin, R., Seo, E., Marecic, O., McArdle, A., Tong, X., Zimdahl, B., Malkovskiy, A., Sinha, R., Gulati, G., Li, X., Wearda, T., Morganti, R., Lopez, M., Ransom, R. C., Duldulao, C. R., Rodrigues, M., Nguyen, A., Januszyk, M., Maan, Z., Paik, K., Yapa, K., Rajadas, J., Wan, D. C., Gurtner, G. C., Snyder, M., Beachy, P. A., Yang, F., Goodman, S. B., Weissman, I. L., Chan, C. F., Longaker, M. T. 2017; 9 (372)
  • Delivery of monocyte lineage cells in a biomimetic scaffold enhances tissue repair. JCI insight Hu, M. S., Walmsley, G. G., Barnes, L. A., Weiskopf, K., Rennert, R. C., Duscher, D., Januszyk, M., Maan, Z. N., Hong, W. X., Cheung, A. T., Leavitt, T., Marshall, C. D., Ransom, R. C., Malhotra, S., Moore, A. L., Rajadas, J., Lorenz, H. P., Weissman, I. L., Gurtner, G. C., Longaker, M. T. 2017; 2 (19)

    Abstract

    The monocyte lineage is essential to normal wound healing. Macrophage inhibition or knockout in mice results in impaired wound healing through reduced neovascularization, granulation tissue formation, and reepithelialization. Numerous studies have either depleted macrophages or reduced their activity in the context of wound healing. Here, we demonstrate that by increasing the number of macrophages or monocytes in the wound site above physiologic levels via pullulan-collagen composite dermal hydrogel scaffold delivery, the rate of wound healing can be significantly accelerated in both wild-type and diabetic mice, with no adverse effect on the quality of repair. Macrophages transplanted onto wounds differentiate into M1 and M2 phenotypes of different proportions at various time points, ultimately increasing angiogenesis. Given that monocytes can be readily isolated from peripheral blood without in vitro manipulation, these findings hold promise for translational medicine aimed at accelerating wound healing across a broad spectrum of diseases.

    View details for PubMedID 28978794

  • Age-Associated Intracellular Superoxide Dismutase Deficiency Potentiates Dermal Fibroblast Dysfunction During Wound Healing. Experimental dermatology Fujiwara, T., Dohi, T., Maan, Z. N., Rustad, K. C., Kwon, S. H., Padmanabhan, J., Whittam, A. J., Suga, H., Duscher, D., Rodrigues, M., Gurtner, G. C. 2017

    Abstract

    Reactive oxygen species (ROS) impair wound healing through destructive oxidation of intracellular proteins, lipids, and nucleic acids. Intracellular superoxide dismutase (SOD1) regulates ROS levels and plays a critical role in tissue homeostasis. Recent evidence suggests that age-associated wound healing impairments may partially result from decreased SOD1 expression. We investigated the mechanistic basis by which increased oxidative stress links to age-associated impaired wound healing. Fibroblasts were isolated from unwounded skin of young and aged mice, and myofibroblast differentiation was assessed by measuring α-smooth muscle actin and collagen gel contraction. Excisional wounds were created on young and aged mice to study the healing rate, ROS levels, and SOD1 expression. A mechanistic link between oxidative stress and fibroblast function was explored by assessing the TGF-β1 signaling pathway components in young and aged mice. Age-related wounds displayed reduced myofibroblast differentiation and delayed wound healing, consistent with a decrease in the in vitro capacity for fibroblast-myofibroblast transition following oxidative stress. Young fibroblasts with normal SOD1 expression exhibited increased phosphorylation of ERK in response to elevated ROS. In contrast, aged fibroblasts with reduced SOD1 expression displayed a reduced capacity to modulate intracellular ROS. Collectively, age-associated wound healing impairments are associated with fibroblast dysfunction that is likely the result of decreased SOD1 expression and subsequent dysregulation of intracellular ROS. Strategies targeting these mechanisms may suggest a new therapeutic approach in the treatment of chronic non-healing wounds in the aged population. This article is protected by copyright. All rights reserved.

    View details for PubMedID 28677217

  • The Role of Focal Adhesion Kinase in Keratinocyte Fibrogenic Gene Expression. International journal of molecular sciences Januszyk, M., Kwon, S. H., Wong, V. W., Padmanabhan, J., Maan, Z. N., Whittam, A. J., Major, M. R., Gurtner, G. C. 2017; 18 (9)

    Abstract

    Abnormal skin scarring causes functional impairment, psychological stress, and high socioeconomic cost. Evidence shows that altered mechanotransduction pathways have been linked to both inflammation and fibrosis, and that focal adhesion kinase (FAK) is a key mediator of these processes. We investigated the importance of keratinocyte FAK at the single cell level in key fibrogenic pathways critical for scar formation. Keratinocytes were isolated from wildtype and keratinocyte-specific FAK-deleted mice, cultured, and sorted into single cells. Keratinocytes were evaluated using a microfluidic-based platform for high-resolution transcriptional analysis. Partitive clustering, gene enrichment analysis, and network modeling were applied to characterize the significance of FAK on regulating keratinocyte subpopulations and fibrogenic pathways important for scar formation. Considerable transcriptional heterogeneity was observed within the keratinocyte populations. FAK-deleted keratinocytes demonstrated increased expression of genes integral to mechanotransduction and extracellular matrix production, including Igtbl, Mmpla, and Col4a1. Transcriptional activities upon FAK deletion were not identical across all single keratinocytes, resulting in higher frequency of a minor subpopulation characterized by a matrix-remodeling profile compared to wildtype keratinocyte population. The importance of keratinocyte FAK signaling gene expression was revealed. A minor subpopulation of keratinocytes characterized by a matrix-modulating profile may be a keratinocyte subset important for mechanotransduction and scar formation.

    View details for PubMedID 28880199

    View details for PubMedCentralID PMC5618564

  • Engrailed-1 Identifies the Fibroblast Lineage Responsible for the Transition from Fetal Scarless to Adult Scarring Cutaneous Wound Repair Hu, M. S., Walmsley, G. G., Maan, Z. N., Sinha, R., Leavitt, T., Marshall, C. D., Weissman, I. L., Gurtner, G. C., Longaker, M. T., Lorenz, H. ELSEVIER SCIENCE INC. 2016: S96–S97
  • Multiple Subsets of Brain Tumor Initiating Cells Coexist in Glioblastoma STEM CELLS Rennert, R. C., Achrol, A. S., Januszyk, M., Kahn, S. A., Liu, T. T., Liu, Y., Sahoo, D., Rodrigues, M., Maan, Z. N., Wong, V. W., Cheshier, S. H., Chang, S. D., Steinberg, G. K., Harsh, G. R., Gurtner, G. C. 2016; 34 (6): 1702-1707

    Abstract

    Brain tumor-initiating cells (BTICs) are self-renewing multipotent cells critical for tumor maintenance and growth. Using single-cell microfluidic profiling, we identified multiple subpopulations of BTICs co-existing in human glioblastoma, characterized by distinct surface marker expression and single-cell molecular profiles relating to distinct bulk tissue molecular subtypes. These data suggest BTIC subpopulation heterogeneity as an underlying source of intra-tumoral bulk tissue molecular heterogeneity, and will support future studies into BTIC subpopulation-specific therapies. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1002/stem.2359

    View details for Web of Science ID 000378089500025

    View details for PubMedID 26991945

  • Microfluidic single-cell transcriptional analysis rationally identifies novel surface marker profiles to enhance cell-based therapies NATURE COMMUNICATIONS Rennert, R. C., Januszyk, M., Sorkin, M., Rodrigues, M., Maan, Z. N., Duscher, D., Whittam, A. J., Kosaraju, R., Chung, M. T., Paik, K., Li, A. Y., Findlay, M., Glotzbach, J. P., Butte, A. J., Gurtner, G. C. 2016; 7

    Abstract

    Current progenitor cell therapies have only modest efficacy, which has limited their clinical adoption. This may be the result of a cellular heterogeneity that decreases the number of functional progenitors delivered to diseased tissue, and prevents correction of underlying pathologic cell population disruptions. Here, we develop a high-resolution method of identifying phenotypically distinct progenitor cell subpopulations via single-cell transcriptional analysis and advanced bioinformatics. When combined with high-throughput cell surface marker screening, this approach facilitates the rational selection of surface markers for prospective isolation of cell subpopulations with desired transcriptional profiles. We establish the usefulness of this platform in costly and highly morbid diabetic wounds by identifying a subpopulation of progenitor cells that is dysfunctional in the diabetic state, and normalizes diabetic wound healing rates following allogeneic application. We believe this work presents a logical framework for the development of targeted cell therapies that can be customized to any clinical application.

    View details for DOI 10.1038/ncomms11945

    View details for Web of Science ID 000379085200001

    View details for PubMedID 27324848

  • Suction assisted liposuction does not impair the regenerative potential of adipose derived stem cells JOURNAL OF TRANSLATIONAL MEDICINE Duscher, D., Luan, A., Rennert, R. C., Atashroo, D., Maan, Z. N., Brett, E. A., Whittam, A. J., Ho, N., Lin, M., Hu, M. S., Walmsley, G. G., Wenny, R., Schmidt, M., Schilling, A. F., Machens, H., Huemer, G. M., Wan, D. C., Longaker, M. T., Gurtner, G. C. 2016; 14

    Abstract

    Adipose-derived stem cells (ASCs) have been identified as a population of multipotent cells with promising applications in tissue engineering and regenerative medicine. ASCs are abundant in fat tissue, which can be safely harvested through the minimally invasive procedure of liposuction. However, there exist a variety of different harvesting methods, with unclear impact on ASC regenerative potential. The aim of this study was thus to compare the functionality of ASCs derived from the common technique of suction-assisted lipoaspiration (SAL) versus resection.Human adipose tissue was obtained from paired abdominoplasty and SAL samples from three female donors, and was processed to isolate the stromal vascular fraction. Fluorescence-activated cell sorting was used to determine ASC yield, and cell viability was assayed. Adipogenic and osteogenic differentiation capacity were assessed in vitro using phenotypic staining and quantification of gene expression. Finally, ASCs were applied in an in vivo model of tissue repair to evaluate their regenerative potential.SAL specimens provided significantly fewer ASCs when compared to excised fat tissue, however, with equivalent viability. SAL-derived ASCs demonstrated greater expression of the adipogenic markers FABP-4 and LPL, although this did not result in a difference in adipogenic differentiation. There were no differences detected in osteogenic differentiation capacity as measured by alkaline phosphatase, mineralization or osteogenic gene expression. Both SAL- and resection-derived ASCs enhanced significantly cutaneous healing and vascularization in vivo, with no significant difference between the two groups.SAL provides viable ASCs with full capacity for multi-lineage differentiation and tissue regeneration, and is an effective method of obtaining ASCs for cell-based therapies.

    View details for DOI 10.1186/s12967-016-0881-1

    View details for Web of Science ID 000375475200004

    View details for PubMedID 27153799

    View details for PubMedCentralID PMC4859988

  • High-Resolution Microfluidic Single-Cell Transcriptional Profiling Reveals Clinically Relevant Subtypes among Human Stem Cell Populations Commonly Utilized in Cell-Based Therapies FRONTIERS IN NEUROLOGY Rennert, R. C., Schaefer, R., Bliss, T., Januszyk, M., Sorkin, M., Achrol, A. S., Rodrigues, M., Maan, Z. N., Kluba, T., Steinberg, G. K., Gurtner, G. C. 2016; 7

    Abstract

    Stem cell therapies can promote neural repair and regeneration, yet controversy regarding optimal cell source and mechanism of action has slowed clinical translation, potentially due to undefined cellular heterogeneity. Single-cell resolution is needed to identify clinically relevant subpopulations with the highest therapeutic relevance. We combine single-cell microfluidic analysis with advanced computational modeling to study for the first time two common sources for cell-based therapies, human NSCs and MSCs. This methodology has the potential to logically inform cell source decisions for any clinical application.

    View details for DOI 10.3389/fneur.2016.00041

    View details for Web of Science ID 000372534400001

    View details for PubMedCentralID PMC4801858

  • Extracellular superoxide dismutase deficiency impairs wound healing in advanced age by reducing neovascularization and fibroblast function EXPERIMENTAL DERMATOLOGY Fujiwara, T., Duscher, D., Rustad, K. C., Kosaraju, R., Rodrigues, M., Whittam, A. J., Januszyk, M., Maan, Z. N., Gurtner, G. C. 2016; 25 (3): 206-211

    Abstract

    Advanced age is characterized by impairments in wound healing, and evidence is accumulating that this may be due in part to a concomitant increase in oxidative stress. Extended exposure to reactive oxygen species (ROS) is thought to lead to cellular dysfunction and organismal death via the destructive oxidation of intra-cellular proteins, lipids and nucleic acids. Extracellular superoxide dismutase (ecSOD/SOD3) is a prime antioxidant enzyme in the extracellular space that eliminates ROS. Here, we demonstrate that reduced SOD3 levels contribute to healing impairments in aged mice. These impairments include delayed wound closure, reduced neovascularization, impaired fibroblast proliferation and increased neutrophil recruitment. We further establish that SOD3 KO and aged fibroblasts both display reduced production of TGF-β1, leading to decreased differentiation of fibroblasts into myofibroblasts. Taken together, these results suggest that wound healing impairments in ageing are associated with increased levels of ROS, decreased SOD3 expression and impaired extracellular oxidative stress regulation. Our results identify SOD3 as a possible target to correct age-related cellular dysfunction in wound healing.

    View details for DOI 10.1111/exd.12909

    View details for Web of Science ID 000373072800285

  • Sutureless Microsurgical Anastomosis Using an Optimized Thermoreversible Intravascular Poloxamer Stent. Plastic and reconstructive surgery Davis, C. R., Rappleye, C. T., Than, P. A., Rodrigues, M., Findlay, M. W., Bishop, S. N., Whitmore, A. J., Maan, Z. N., McGoldrick, R. B., Grobbelaar, A. O., Gurtner, G. C. 2016; 137 (2): 546-556

    Abstract

    Sutureless microvascular anastomosis has great translational potential to simplify microvascular surgery, shorten operative times, and improve clinical outcomes. The authors developed a transient thermoreversible microvascular stent using a poloxamer to maintain vessel lumen patency before application of commercially available adhesives to seal the anastomosis instead of sutures. Despite technical success, human application necessitates bovine serum albumin removal from existing formulations; rapid poloxamer transition between states; and increased stiffness for reliable, reproducible, and precise microvascular approximation.Two commercially available poloxamers were used in this study (P407 and P188). After removing bovine serum albumin, each poloxamer was tested at varying concentrations either alone or in combination to determine the optimal preparation for sutureless microvascular anastomosis. Transition temperature and formulation stiffness were tested in vitro by rheometry, with the most promising combinations tested in an established in vivo model.Increasing poloxamer concentration resulted in an increase in stiffness and decrease in transition temperature. Pure P188 without bovine serum albumin, dissolved in phosphate-buffered saline to a 45% concentration, demonstrated desirable rheologic behavior, with precise gel transition and increased gel stiffness compared with our previous formulation of 17% P407 (96 kPa versus 10 kPa). These characteristics were optimal for microsurgical intravascular use, offering surgical precision and control between liquid and solid states, depending on the surgically controlled local temperature.Use of 45% P188 without bovine serum albumin demonstrated optimal rheologic and translational properties as a microvascular stent for sutureless anastomosis. Rapid transition, increased stiffness, and safety profile demonstrate safe translational application for human clinical trials.

    View details for DOI 10.1097/01.prs.0000475774.37267.3f

    View details for PubMedID 26818289

  • Challenges and Opportunities in Drug Delivery for Wound Healing. Advances in wound care Whittam, A. J., Maan, Z. N., Duscher, D., Wong, V. W., Barrera, J. A., Januszyk, M., Gurtner, G. C. 2016; 5 (2): 79-88

    Abstract

    Significance: Chronic wounds remain a significant public health problem. Alterations in normal physiological processes caused by aging or diabetes lead to impaired tissue repair and the development of chronic and nonhealing wounds. Understanding the unique features of the wound environment will be required to develop new therapeutics that impact these disabling conditions. New drug-delivery systems (DDSs) may enhance current and future therapies for this challenging clinical problem. Recent Advances: Historically, physical barriers and biological degradation limited the efficacy of DDSs in wound healing. In aiming at improving and optimizing drug delivery, recent data suggest that combinations of delivery mechanisms, such as hydrogels, small molecules, RNA interference (RNAi), as well as growth factor and stem cell-based therapies (biologics), could offer exciting new opportunities for improving tissue repair. Critical Issues: The lack of effective therapeutic approaches to combat the significant disability associated with chronic wounds has become an area of increasing clinical concern. However, the unique challenges of the wound environment have limited the development of effective therapeutic options for clinical use. Future Directions: New platforms presented in this review may provide clinicians and scientists with an improved understanding of the alternatives for drug delivery in wound care, which may facilitate the development of new therapeutic approaches for patients.

    View details for PubMedID 26862465

  • Adipose-Derived Stem Cell-Seeded Hydrogels Increase Endogenous Progenitor Cell Recruitment and Neovascularization in Wounds TISSUE ENGINEERING PART A Kosaraju, R., Rennert, R. C., Maan, Z. N., Duscher, D., Barrera, J., Whittam, A. J., Januszyk, M., Rajadas, J., Rodrigues, M., Gurtner, G. C. 2016; 22 (3-4): 295-305

    Abstract

    Adipose-derived mesenchymal stem cells (ASCs) are appealing for cell-based wound therapies because of their accessibility and ease of harvest, but their utility is limited by poor cell survival within the harsh wound microenvironment. In prior work, our laboratory has demonstrated that seeding ASCs within a soft pullulan-collagen hydrogel enhances ASC survival and improves wound healing. To more fully understand the mechanism of this therapy, we examined whether ASC-seeded hydrogels were able to modulate the recruitment and/or functionality of endogenous progenitor cells. Employing a parabiosis model and fluorescence-activated cell sorting analysis, we demonstrate that application of ASC-seeded hydrogels to wounds, when compared with injected ASCs or a noncell control, increased the recruitment of provascular circulating bone marrow-derived mesenchymal progenitor cells (BM-MPCs). BM-MPCs comprised 23.0% of recruited circulating progenitor cells in wounds treated with ASC-seeded hydrogels versus 8.4% and 2.1% in those treated with controls, p < 0.05. Exploring the potential for functional modulation of BM-MPCs, we demonstrate a statistically significant increase in BM-MPC migration, proliferation, and tubulization when exposed to hydrogel-seeded ASC-conditioned medium versus control ASC-conditioned medium (73.8% vs. 51.4% scratch assay closure; 9.1% vs. 1.4% proliferation rate; 10.2 vs. 5.5 tubules/HPF; p < 0.05 for all assays). BM-MPC expression of genes related to cell stemness and angiogenesis was also significantly increased following exposure to hydrogel-seeded ASC-conditioned medium (p < 0.05). These data suggest that ASC-seeded hydrogels improve both progenitor cell recruitment and functionality to effect greater neovascularization.

    View details for DOI 10.1089/ten.tea.2015.0277

    View details for Web of Science ID 000369987900012

    View details for PubMedID 26871860

    View details for PubMedCentralID PMC4779321

  • Ultrasound-Assisted Liposuction Does Not Compromise the Regenerative Potential of Adipose-Derived Stem Cells. Stem cells translational medicine Duscher, D., Atashroo, D., Maan, Z. N., Luan, A., Brett, E. A., Barrera, J., Khong, S. M., Zielins, E. R., Whittam, A. J., Hu, M. S., Walmsley, G. G., Pollhammer, M. S., Schmidt, M., Schilling, A. F., Machens, H., Huemer, G. M., Wan, D. C., Longaker, M. T., Gurtner, G. C. 2016; 5 (2): 248-257

    Abstract

    Human mesenchymal stem cells (MSCs) have recently become a focus of regenerative medicine, both for their multilineage differentiation capacity and their excretion of proregenerative cytokines. Adipose-derived mesenchymal stem cells (ASCs) are of particular interest because of their abundance in fat tissue and the ease of harvest via liposuction. However, little is known about the impact of different liposuction methods on the functionality of ASCs. Here we evaluate the regenerative abilities of ASCs harvested via a third-generation ultrasound-assisted liposuction (UAL) device versus ASCs obtained via standard suction-assisted lipoaspiration (SAL). Lipoaspirates were sorted using fluorescent assisted cell sorting based on an established surface-marker profile (CD34+/CD31-/CD45-), to obtain viable ASCs. Yield and viability were compared and the differentiation capacities of the ASCs were assessed. Finally, the regenerative potential of ASCs was examined using an in vivo model of tissue regeneration. UAL- and SAL-derived samples demonstrated equivalent ASC yield and viability, and UAL ASCs were not impaired in their osteogenic, adipogenic, or chondrogenic differentiation capacity. Equally, quantitative real-time polymerase chain reaction showed comparable expression of most osteogenic, adipogenic, and key regenerative genes between both ASC groups. Cutaneous regeneration and neovascularization were significantly enhanced in mice treated with ASCs obtained by either UAL or SAL compared with controls, but there were no significant differences in healing between cell-therapy groups. We conclude that UAL is a successful method of obtaining fully functional ASCs for regenerative medicine purposes. Cells harvested with this alternative approach to liposuction are suitable for cell therapy and tissue engineering applications. Significance: Adipose-derived mesenchymal stem cells (ASCs) are an appealing source of therapeutic progenitor cells because of their multipotency, diverse cytokine profile, and ease of harvest via liposuction. Alternative approaches to classical suction-assisted liposuction are gaining popularity; however, little evidence exists regarding the impact of different liposuction methods on the regenerative functionality of ASCs. Human ASC characteristics and regenerative capacity were assessed when harvested via ultrasound-assisted (UAL) versus standard suction-assisted liposuction. ASCs obtained via UAL were of equal quality when directly compared with the current gold standard harvest method. UAL is an adjunctive source of fully functional mesenchymal stem cells for applications in basic research and clinical therapy.

    View details for DOI 10.5966/sctm.2015-0064

    View details for PubMedID 26702129

    View details for PubMedCentralID PMC4729547

  • Surveillance of Stem Cell Fate and Function: A System for Assessing Cell Survival and Collagen Expression In Situ TISSUE ENGINEERING PART A Walmsley, G. G., Senarath-Yapa, K., Wearda, T. L., Menon, S., Hu, M. S., Duscher, D., Maan, Z. N., Tsai, J. M., Zielins, E. R., Weissman, I. L., Gurtner, G. C., Lorenz, H. P., Longaker, M. T. 2016; 22 (1-2): 31-40

    Abstract

    Cell-based therapy is an emerging paradigm in skeletal regenerative medicine. However, the primary means by which transplanted cells contribute to bone repair and regeneration remain controversial. To gain an insight into the mechanisms of how both transplanted and endogenous cells mediate skeletal healing, we used a transgenic mouse strain expressing both the topaz variant of green fluorescent protein under the control of the collagen, type I, alpha 1 promoter/enhancer sequence (Col1a1(GFP)) and membrane-bound tomato red fluorescent protein constitutively in all cell types (R26(mTmG)). A comparison of healing in parietal versus frontal calvarial defects in these mice revealed that frontal osteoblasts express Col1a1 to a greater degree than parietal osteoblasts. Furthermore, the scaffold-based application of adipose-derived stromal cells (ASCs), bone marrow-derived mesenchymal stem cells (BM-MSCs), and osteoblasts derived from these mice to critical-sized calvarial defects allowed for investigation of cell survival and function following transplantation. We found that ASCs led to significantly faster rates of bone healing in comparison to BM-MSCs and osteoblasts. ASCs displayed both increased survival and increased Col1a1 expression compared to BM-MSCs and osteoblasts following calvarial defect transplantation, which may explain their superior regenerative capacity in the context of bone healing. Using this novel reporter system, we were able to elucidate how cell-based therapies impact bone healing and identify ASCs as an attractive candidate for cell-based skeletal regenerative therapy. These insights potentially influence stem cell selection in translational clinical trials evaluating cell-based therapeutics for osseous repair and regeneration.

    View details for DOI 10.1089/ten.tea.2015.0221

    View details for Web of Science ID 000368520300005

    View details for PubMedCentralID PMC4741228

  • Stem Cells in Wound Healing: The Future of Regenerative Medicine? A Mini-Review. Gerontology Duscher, D., Barrera, J., Wong, V. W., Maan, Z. N., Whittam, A. J., Januszyk, M., Gurtner, G. C. 2016; 62 (2): 216-225

    Abstract

    The increased risk of disease and decreased capacity to respond to tissue insult in the setting of aging results from complex changes in homeostatic mechanisms, including the regulation of oxidative stress and cellular heterogeneity. In aged skin, the healing capacity is markedly diminished resulting in a high risk for chronic wounds. Stem cell-based therapies have the potential to enhance cutaneous regeneration, largely through trophic and paracrine activity. Candidate cell populations for therapeutic application include adult mesenchymal stem cells, embryonic stem cells and induced pluripotent stem cells. Autologous cell-based approaches are ideal to minimize immune rejection but may be limited by the declining cellular function associated with aging. One strategy to overcome age-related impairments in various stem cell populations is to identify and enrich with functionally superior stem cell subsets via single cell transcriptomics. Another approach is to optimize cell delivery to the harsh environment of aged wounds via scaffold-based cell applications to enhance engraftment and paracrine activity of therapeutic stem cells. In this review, we shed light on challenges and recent advances surrounding stem cell therapies for wound healing and discuss limitations for their clinical adoption.

    View details for DOI 10.1159/000381877

    View details for PubMedID 26045256

  • Short Hairpin RNA Silencing of PHD-2 Improves Neovascularization and Functional Outcomes in Diabetic Wounds and Ischemic Limbs. PloS one Paik, K. J., Maan, Z. N., Zielins, E. R., Duscher, D., Whittam, A. J., Morrison, S. D., Brett, E. A., Ransom, R. C., Hu, M. S., Wu, J. C., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2016; 11 (3)

    Abstract

    The transcription factor hypoxia-inducible factor 1-alpha (HIF-1α) is responsible for the downstream expression of over 60 genes that regulate cell survival and metabolism in hypoxic conditions as well as those that enhance angiogenesis to alleviate hypoxia. However, under normoxic conditions, HIF-1α is hydroxylated by prolyl hydroxylase 2, and subsequently degraded, with a biological half-life of less than five minutes. Here we investigated the therapeutic potential of inhibiting HIF-1α degradation through short hairpin RNA silencing of PHD-2 in the setting of diabetic wounds and limb ischemia. Treatment of diabetic mouse fibroblasts with shPHD-2 in vitro resulted in decreased levels of PHD-2 transcript demonstrated by qRT-PCR, higher levels of HIF-1α as measured by western blot, and higher expression of the downstream angiogenic genes SDF-1 and VEGFα, as measured by qRT-PCR. In vivo, shPHD-2 accelerated healing of full thickness excisional wounds in diabetic mice compared to shScr control, (14.33 ± 0.45 days vs. 19 ± 0.33 days) and was associated with an increased vascular density. Delivery of shPHD-2 also resulted in improved perfusion of ischemic hind limbs compared to shScr, prevention of distal digit tip necrosis, and increased survival of muscle tissue. Knockdown of PHD-2 through shRNA treatment has the potential to stimulate angiogenesis through overexpression of HIF-1α and upregulation of pro-angiogenic genes downstream of HIF-1α, and may represent a viable, non-viral approach to gene therapy for ischemia related applications.

    View details for DOI 10.1371/journal.pone.0150927

    View details for PubMedID 26967994

    View details for PubMedCentralID PMC4788284

  • Murine Dermal Fibroblast Isolation by FACS JOVE-JOURNAL OF VISUALIZED EXPERIMENTS Walmsley, G. G., Maan, Z. N., Hu, M. S., Atashroo, D. A., Whittam, A. J., Duscher, D., Tevlin, R., Marecic, O., Lorenz, H. P., Gurtner, G. C., Longaker, M. T. 2016

    Abstract

    Fibroblasts are the principle cell type responsible for secreting extracellular matrix and are a critical component of many organs and tissues. Fibroblast physiology and pathology underlie a spectrum of clinical entities, including fibroses in multiple organs, hypertrophic scarring following burns, loss of cardiac function following ischemia, and the formation of cancer stroma. However, fibroblasts remain a poorly characterized type of cell, largely due to their inherent heterogeneity. Existing methods for the isolation of fibroblasts require time in cell culture that profoundly influences cell phenotype and behavior. Consequently, many studies investigating fibroblast biology rely upon in vitro manipulation and do not accurately capture fibroblast behavior in vivo. To overcome this problem, we developed a FACS-based protocol for the isolation of fibroblasts from the dorsal skin of adult mice that does not require cell culture, thereby preserving the physiologic transcriptional and proteomic profile of each cell. Our strategy allows for exclusion of non-mesenchymal lineages via a lineage negative gate (Lin(-)) rather than a positive selection strategy to avoid pre-selection or enrichment of a subpopulation of fibroblasts expressing specific surface markers and be as inclusive as possible across this heterogeneous cell type.

    View details for DOI 10.3791/53430

    View details for Web of Science ID 000368577400023

    View details for PubMedCentralID PMC4781205

  • The Role of Current Techniques and Concepts in Peripheral Nerve Repair. Plastic surgery international Houschyar, K. S., Momeni, A., Pyles, M. N., Cha, J. Y., Maan, Z. N., Duscher, D., Jew, O. S., Siemers, F., van Schoonhoven, J. 2016; 2016: 4175293-?

    Abstract

    Patients with peripheral nerve injuries, especially severe injury, often face poor nerve regeneration and incomplete functional recovery, even after surgical nerve repair. This review summarizes treatment options of peripheral nerve injuries with current techniques and concepts and reviews developments in research and clinical application of these therapies.

    View details for DOI 10.1155/2016/4175293

    View details for PubMedID 26904282

    View details for PubMedCentralID PMC4745297

  • Fibroblast-Specific Deletion of Hypoxia Inducible Factor-1 Critically Impairs Murine Cutaneous Neovascularization and Wound Healing PLASTIC AND RECONSTRUCTIVE SURGERY Duscher, D., Maan, Z. N., Whittam, A. J., Sorkin, M., Hu, M. S., Walmsley, G. G., Baker, H., Fischer, L. H., Januszyk, M., Wong, V. W., Gurtner, G. C. 2015; 136 (5): 1004-1013

    Abstract

    Diabetes and aging are known risk factors for impaired neovascularization in response to ischemic insult, resulting in chronic wounds, and poor outcomes following myocardial infarction and cerebrovascular injury. Hypoxia-inducible factor (HIF)-1α, has been identified as a critical regulator of the response to ischemic injury and is dysfunctional in diabetic and elderly patients. To better understand the role of this master hypoxia regulator within cutaneous tissue, the authors generated and evaluated a fibroblast-specific HIF-1α knockout mouse model.The authors generated floxed HIF-1 mice (HIF-1) by introducing loxP sites around exon 1 of the HIF-1 allele in C57BL/6J mice. Fibroblast-restricted HIF-1α knockout (FbKO) mice were generated by breeding our HIF-1 with tamoxifen-inducible Col1a2-Cre mice (Col1a2-CreER). HIF-1α knockout was evaluated on a DNA, RNA, and protein level. Knockout and wild-type mice were subjected to ischemic flap and wound healing models, and CD31 immunohistochemistry was performed to assess vascularity of healed wounds.Quantitative real-time polymerase chain reaction of FbKO skin demonstrated significantly reduced Hif1 and Vegfa expression compared with wild-type. This finding was confirmed at the protein level (p < 0.05). HIF-1α knockout mice showed significantly impaired revascularization of ischemic tissue and wound closure and vascularity (p < 0.05).Loss of HIF-1α from fibroblasts results in delayed wound healing, reduced wound vascularity, and significant impairment in the ischemic neovascular response. These findings provide new insight into the importance of cell-specific responses to hypoxia during cutaneous neovascularization.

    View details for Web of Science ID 000364092800001

    View details for PubMedID 26505703

  • Medical leech therapy in plastic reconstructive surgery. Wiener medizinische Wochenschrift Houschyar, K. S., Momeni, A., Maan, Z. N., Pyles, M. N., Jew, O. S., Strathe, M., Michalsen, A. 2015; 165 (19-20): 419-425

    Abstract

    The use of Hirudo medicinalis in clinical practice has increased in recent years. The primary indication in plastic surgery has traditionally been venous congestion. However, other reported clinical applications were in varicose veins, thrombophlebitis, and osteoarthritis. In this review, we summarize recent data elucidating the role that medicinal leeches play in the field of plastic surgery.

    View details for DOI 10.1007/s10354-015-0382-5

    View details for PubMedID 26297126

  • Melanoma Progression Depends on CXCL12 Expression by Host Endothelium Maan, Z. N., Hu, M. S., Whittam, A., Fischer, L. H., Duscher, D., Walmsley, G. G., Januszyk, M., Whitmore, A. J., Longaker, M. T., Gurtner, G. C. ELSEVIER SCIENCE INC. 2015: S116
  • Delivery of Macrophages in a Biomimetic Scaffold Accelerates Diabetic Wound Healing Through Enhanced Angiogenesis Walmsley, G. G., Hu, M. S., Duscher, D., Januszyk, M., Maan, Z. N., Senarath-Yapa, K., Tevlin, R., Zielins, E. R., Gurtner, G. C., Longaker, M. T. ELSEVIER SCIENCE INC. 2015: S113–S114
  • Adipose-Derived Stem Cells Improve Engraftment of Full-Thickness Skin Grafts by Increasing Angiogenesis Hu, M. S., Hong, W., Maan, Z. N., Hu, M., Zimmermann, A. S., Walmsley, G. G., Chung, M., Lorenz, H., Longaker, M. T. ELSEVIER SCIENCE INC. 2015: S112
  • Wounds outcompete tumors for neovascularization Hu, M. S., Maan, Z. N., Hong, W., Walmsley, G. G., Rennert, R. C., Atashroo, D., Gurtner, G. C., Giaccia, A. J., Lorenz, H., Longaker, M. T. ELSEVIER SCIENCE INC. 2015: E124
  • Gigantic LCFA-SCIP Mosaic Flap for Upper Extremity Reconstruction. Plastic and reconstructive surgery. Global open Pollhammer, M. S., Duscher, D., Maan, Z. N., Schmidt, M., Huemer, G. M. 2015; 3 (9)

    View details for DOI 10.1097/GOX.0000000000000463

    View details for PubMedID 26495219

    View details for PubMedCentralID PMC4596431

  • High-Throughput Screening of Surface Marker Expression on Undifferentiated and Differentiated Human Adipose-Derived Stromal Cells TISSUE ENGINEERING PART A Walmsley, G. G., Atashroo, D. A., Maan, Z. N., Hu, M. S., Zielins, E. R., Tsai, J. M., Duscher, D., Paik, K., Tevlin, R., Marecic, O., Wan, D. C., Gurtner, G. C., Longaker, M. T. 2015; 21 (15-16): 2281-2291

    Abstract

    Adipose tissue contains an abundant source of multipotent mesenchymal cells termed "adipose-derived stromal cells" (ASCs) that hold potential for regenerative medicine. However, the heterogeneity inherent to ASCs harvested using standard methodologies remains largely undefined, particularly in regards to differences across donors. Identifying the subpopulations of ASCs predisposed toward differentiation along distinct lineages holds value for improving graft survival, predictability, and efficiency. Human ASCs (hASCs) from three different donors were independently isolated by density-based centrifugation from adipose tissue and maintained in culture or differentiated along either adipogenic or osteogenic lineages using differentiation media. Undifferentiated and differentiated hASCs were then analyzed for the presence of 242 human surface markers by flow cytometry analysis. By comprehensively characterizing the surface marker profile of undifferentiated hASCs using flow cytometry, we gained novel insights into the heterogeneity underlying protein expression on the surface of cultured undifferentiated hASCs across different donors. Comparison of the surface marker profile of undifferentiated hASCs with hASCs that have undergone osteogenic or adipogenic differentiation allowed for the identification of surface markers that were upregulated and downregulated by osteogenic or adipogenic differentiation. Osteogenic differentiation induced upregulation of CD164 and downregulation of CD49a, CD49b, CD49c, CD49d, CD55, CD58, CD105, and CD166 while adipogenic differentiation induced upregulation of CD36, CD40, CD146, CD164, and CD271 and downregulation of CD49b, CD49c, CD49d, CD71, CD105, and CD166. These results lend support to the notion that hASCs isolated using standard methodologies represent a heterogeneous population and serve as a foundation for future studies seeking to maximize their regenerative potential through fluorescence-activated cell sorting-based selection before therapy.

    View details for DOI 10.1089/ten.tea.2015.0039

    View details for Web of Science ID 000359812700014

    View details for PubMedID 26020286

    View details for PubMedCentralID PMC4529076

  • En1 fibroblasts and melanoma MELANOMA MANAGEMENT Walmsley, G. G., Hu, M. S., Maan, Z. N., Rinkevich, Y., Weissman, I. L., Longaker, M. T. 2015; 2 (3): 191–92

    View details for DOI 10.2217/MMT.15.23

    View details for Web of Science ID 000218588700001

  • Wnt signaling induces epithelial differentiation during cutaneous wound healing. Organogenesis Houschyar, K. S., Momeni, A., Pyles, M. N., Maan, Z. N., Whittam, A. J., Siemers, F. 2015; 11 (3): 95-104

    Abstract

    Cutaneous wound repair in adult mammals typically does not regenerate original dermal architecture. Skin that has undergone repair following injury is not identical to intact uninjured skin. This disparity may be caused by differences in the mechanisms that regulate postnatal cutaneous wound repair compared to embryonic skin development and thus we seek a deeper understanding of the role that Wnt signaling plays in the mechanisms of skin repair in both fetal and adult wounds. The influence of secreted Wnt signaling proteins in tissue homeostasis has galvanized efforts to identify small molecules that target Wnt-mediated cellular responses. Wnt signaling is activated by wounding and participates in every subsequent stage of the healing process from the control of inflammation and programmed cell death, to the mobilization of stem cell reservoirs within the wound site. Endogenous Wnt signaling augmentation represents an attractive option to aid in the restoration of cutaneous wounds, as the complex mechanisms of the Wnt pathway have been increasingly investigated over the years. In this review, we summarize recent data elucidating the roles that Wnt signaling plays in cutaneous wound healing process.

    View details for DOI 10.1080/15476278.2015.1086052

    View details for PubMedID 26309090

    View details for PubMedCentralID PMC4879891

  • What Makes a Plastic Surgery Residency Program Attractive? An Applicant's Perspective PLASTIC AND RECONSTRUCTIVE SURGERY Atashroo, D. A., Luan, A., Vyas, K. S., Zielins, E. R., Maan, Z., Duscher, D., Walmsley, G. G., Lynch, M. P., Davenport, D. L., Wan, D. C., Longaker, M. T., Vasconez, H. C. 2015; 136 (1): 189-196

    Abstract

    Plastic surgery is among the most competitive specialties in medicine, but little is known about the attributes of programs that are most attractive to successful applicants. This study aimed to understand and provide insights regarding program characteristics that are most influential to students when ranking plastic surgery programs.An anonymous online survey was conducted with newly matched plastic surgery residents for the integrated and combined Match in 2012 and 2013. Subjects were queried regarding their demographics, qualifications, application experiences, and motivations for residency program selection.A total of 92 of 245 matched plastic surgery residents (38 percent) responded to the survey. The perception of resident happiness was the most positive factor influencing program ranking, followed by high operative volume, faculty mentorship, and strong research infrastructure. Perception of a program as "malignant" was the most negative attribute. Applicants with Step 1 scores greater than 245 received significantly more interviews (p =0.001) and considered resident benefits less important (p < 0.05), but geographic location more important (p =0.005). Applicants who published more than two articles also received more interviews (p =0.001) and ranked a strong research infrastructure and program reputation as significantly more important (p < 0.05). Forty-two percent of applicants completed an away rotation at the program with which they matched, and these applicants were more likely to match at their number one ranked program (p = 0.001).Plastic surgery applicants have differing preferences regarding the ideal training program, but some attributes resonate. These trends can guide programs for improvement in attracting the best applicants.

    View details for DOI 10.1097/PRS.0000000000001365

    View details for Web of Science ID 000357097900001

    View details for PubMedID 26111321

  • Studies in Fat Grafting: Part V. Cell-Assisted Lipotransfer to Enhance Fat Graft Retention Is Dose Dependent PLASTIC AND RECONSTRUCTIVE SURGERY Paik, K. J., Zielins, E. R., Atashroo, D. A., Maan, Z. N., Duscher, D., Luan, A., Walmsley, G. G., Momeni, A., Vistnes, S., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2015; 136 (1): 67-75

    Abstract

    Cell-assisted lipotransfer has shown much promise as a technique for improving fat graft take. However, the concentration of stromal vascular fraction cells required to optimally enhance fat graft retention remains unknown.Human lipoaspirate was processed for both fat transfer and harvest of stromal vascular fraction cells. Cells were then mixed back with fat at varying concentrations ranging from 10,000 to 10 million cells per 200 μl of fat. Fat graft volume retention was assessed by means of computed tomographic scanning over 8 weeks, and then fat grafts were explanted and compared histologically for overall architecture and vascularity.Maximum fat graft retention was seen at a concentration of 10,000 cells per 200 μl of fat. The addition of higher number of cells negatively impacted fat graft retention, with supplementation of 10 million cells producing the lowest final volumes, lower than fat alone. Interestingly, fat grafts supplemented with 10,000 cells showed significantly increased vascularity and decreased inflammation, whereas fat grafts supplemented with 10 million cells showed significant lipodegeneration compared with fat alone: The authors' study demonstrates dose dependence in the number of stromal vascular fraction cells that can be added to a fat graft to enhance retention. Although cell-assisted lipotransfer may help promote graft survival, this effect may need to be balanced with the increased metabolic load of added cells that may compete with adipocytes for nutrients during the postgraft period.

    View details for DOI 10.1097/PRS.0000000000001367

    View details for Web of Science ID 000357096300002

    View details for PubMedID 25829158

    View details for PubMedCentralID PMC4483157

  • Injuries to Appendage Extremities and Digit Tips: A Clinical and Cellular Update DEVELOPMENTAL DYNAMICS Rinkevich, Y., Maan, Z. N., Walmsley, G. G., Sen, S. K. 2015; 244 (5): 641-650

    Abstract

    The regrowth of amputated appendage extremities and the distal tips of digits represent models of tissue regeneration in multiple vertebrate taxa. In humans, digit tip injuries, including traumatic amputation and crush injuries, are among the most common type of injury to the human hand. Despite clinical reports demonstrating natural regeneration of appendages in lower vertebrates and human digits, current treatment options are suboptimal, and are complicated by the anatomical complexities and functions of the different tissues within the digits.In light of these challenges, we focus on recent advancements in understanding appendage regeneration from model organisms. We pay special attention to the cellular programs underlying appendage regeneration, where cumulative data from salamanders, fish, frogs, and mice indicate that regeneration occurs by the actions of lineage-restricted precursors. We focus on pathologic states and the interdependency that exists, in both humans and animal models, between the nail organ and the peripheral nerves for successful regeneration.The increased understanding of regeneration in animal models may open new opportunities for basic and translational research aimed at understanding the mechanisms that support limb regeneration, as well as amelioration of limb abnormalities and pathologies.

    View details for DOI 10.1002/dvdy.24265

    View details for Web of Science ID 000353953600002

    View details for PubMedID 25715837

  • Identification and isolation of a dermal lineage with intrinsic fibrogenic potential SCIENCE Rinkevich, Y., Walmsley, G. G., Hu, M. S., Maan, Z. N., Newman, A. M., Drukker, M., Januszyk, M., Krampitz, G. W., Gurtner, G. C., Lorenz, H. P., Weissman, I. L., Longaker, M. T. 2015; 348 (6232): 302-?

    Abstract

    Dermal fibroblasts represent a heterogeneous population of cells with diverse features that remain largely undefined. We reveal the presence of at least two fibroblast lineages in murine dorsal skin. Lineage tracing and transplantation assays demonstrate that a single fibroblast lineage is responsible for the bulk of connective tissue deposition during embryonic development, cutaneous wound healing, radiation fibrosis, and cancer stroma formation. Lineage-specific cell ablation leads to diminished connective tissue deposition in wounds and reduces melanoma growth. Using flow cytometry, we identify CD26/DPP4 as a surface marker that allows isolation of this lineage. Small molecule-based inhibition of CD26/DPP4 enzymatic activity during wound healing results in diminished cutaneous scarring. Identification and isolation of these lineages hold promise for translational medicine aimed at in vivo modulation of fibrogenic behavior.

    View details for DOI 10.1126/science.aaa2151

    View details for Web of Science ID 000352999000034

    View details for PubMedCentralID PMC5088503

  • Skin fibrosis. Identification and isolation of a dermal lineage with intrinsic fibrogenic potential. Science Rinkevich, Y., Walmsley, G. G., Hu, M. S., Maan, Z. N., Newman, A. M., Drukker, M., Januszyk, M., Krampitz, G. W., Gurtner, G. C., Lorenz, H. P., Weissman, I. L., Longaker, M. T. 2015; 348 (6232)

    Abstract

    Dermal fibroblasts represent a heterogeneous population of cells with diverse features that remain largely undefined. We reveal the presence of at least two fibroblast lineages in murine dorsal skin. Lineage tracing and transplantation assays demonstrate that a single fibroblast lineage is responsible for the bulk of connective tissue deposition during embryonic development, cutaneous wound healing, radiation fibrosis, and cancer stroma formation. Lineage-specific cell ablation leads to diminished connective tissue deposition in wounds and reduces melanoma growth. Using flow cytometry, we identify CD26/DPP4 as a surface marker that allows isolation of this lineage. Small molecule-based inhibition of CD26/DPP4 enzymatic activity during wound healing results in diminished cutaneous scarring. Identification and isolation of these lineages hold promise for translational medicine aimed at in vivo modulation of fibrogenic behavior.

    View details for DOI 10.1126/science.aaa2151

    View details for PubMedID 25883361

    View details for PubMedCentralID PMC5088503

  • Scarless wound healing: chasing the holy grail. Plastic and reconstructive surgery Walmsley, G. G., Maan, Z. N., Wong, V. W., Duscher, D., Hu, M. S., Zielins, E. R., Wearda, T., Muhonen, E., McArdle, A., Tevlin, R., Atashroo, D. A., Senarath-Yapa, K., Lorenz, H. P., Gurtner, G. C., Longaker, M. T. 2015; 135 (3): 907-917

    Abstract

    Over 100 million patients acquire scars in the industrialized world each year, primarily as a result of elective operations. Although undefined, the global incidence of scarring is even larger, extending to significant numbers of burn and other trauma-related wounds. Scars have the potential to exert a profound psychological and physical impact on the individual. Beyond aesthetic considerations and potential disfigurement, scarring can result in restriction of movement and reduced quality of life. The formation of a scar following skin injury is a consequence of wound healing occurring through reparative rather than regenerative mechanisms. In this article, the authors review the basic stages of wound healing; differences between adult and fetal wound healing; various mechanical, genetic, and pharmacologic strategies to reduce scarring; and the biology of skin stem/progenitor cells that may hold the key to scarless regeneration.

    View details for DOI 10.1097/PRS.0000000000000972

    View details for PubMedID 25719706

  • Live Fibroblast Harvest Reveals Surface Marker Shift In Vitro TISSUE ENGINEERING PART C-METHODS Walmsley, G. G., Rinkevich, Y., Hu, M. S., Montoro, D. T., Lo, D. D., McArdle, A., Maan, Z. N., Morrison, S. D., Duscher, D., Whittam, A. J., Wong, V. W., Weissman, I. L., Gurtner, G. C., Longaker, M. T. 2015; 21 (3): 314-321

    Abstract

    Current methods for the isolation of fibroblasts require extended ex vivo manipulation in cell culture. As a consequence, prior studies investigating fibroblast biology may fail to adequately represent cellular phenotypes in vivo. To overcome this problem, we describe a detailed protocol for the isolation of fibroblasts from the dorsal dermis of adult mice that bypasses the need for cell culture, thereby preserving the physiological, transcriptional, and proteomic profiles of each cell. Using the described protocol we characterized the transcriptional programs and the surface expression of 176 CD markers in cultured versus uncultured fibroblasts. The differential expression patterns we observed highlight the importance of a live harvest for investigations of fibroblast biology.

    View details for DOI 10.1089/ten.tec.2014.0118

    View details for Web of Science ID 000350043400009

    View details for PubMedID 25275778

    View details for PubMedCentralID PMC4346232

  • Cell recruitment by amnion chorion grafts promotes neovascularization JOURNAL OF SURGICAL RESEARCH Maan, Z. N., Rennert, R. C., Koob, T. J., Januszyk, M., Li, W. W., Gurtner, G. C. 2015; 193 (2): 953-962

    Abstract

    Nonhealing wounds are a significant health burden. Stem and progenitor cells can accelerate wound repair and regeneration. Human amniotic membrane has demonstrated efficacy in promoting wound healing, though the underlying mechanisms remain unknown. A dehydrated human amnion chorion membrane (dHACM) was tested for its ability to recruit hematopoietic progenitor cells to a surgically implanted graft in a murine model of cutaneous ischemia.dHACM was subcutaneously implanted under elevated skin (ischemic stimulus) in either wild-type mice or mice surgically parabiosed to green fluorescent protein (GFP) + reporter mice. A control acellular dermal matrix, elevated skin without an implant, and normal unwounded skin were used as controls. Wound tissue was harvested and processed for histology and flow cytometric analysis.Implanted dHACMs recruited significantly more progenitor cells compared with controls (*P < 0.05) and displayed in vivo SDF-1 expression with incorporation of CD34 + progenitor cells within the matrix. Parabiosis modeling confirmed the circulatory origin of recruited cells, which coexpressed progenitor cell markers and were localized to foci of neovascularization within implanted matrices.In summary, dHACM effectively recruits circulating progenitor cells, likely because of stromal derived factor 1 (SDF-1) expression. The recruited cells express markers of "stemness" and localize to sites of neovascularization, providing a partial mechanism for the clinical efficacy of human amniotic membrane in the treatment of chronic wounds.

    View details for DOI 10.1016/j.jss.2014.08.045

    View details for Web of Science ID 000346244300056

    View details for PubMedID 25266600

  • Exercise induces stromal cell-derived factor-1a-mediated release of endothelial progenitor cells with increased vasculogenic function. Plastic and reconstructive surgery Chang, E., Paterno, J., Duscher, D., Maan, Z. N., Chen, J. S., Januszyk, M., Rodrigues, M., Rennert, R. C., Bishop, S., Whitmore, A. J., Whittam, A. J., Longaker, M. T., Gurtner, G. C. 2015; 135 (2): 340e-50e

    Abstract

    Endothelial progenitor cells have been shown to traffic to and incorporate into ischemic tissues, where they participate in new blood vessel formation, a process termed vasculogenesis. Previous investigation has demonstrated that endothelial progenitor cells appear to mobilize from bone marrow to the peripheral circulation after exercise. In this study, the authors investigate potential etiologic factors driving this mobilization and investigate whether the mobilized endothelial progenitor cells are the same as those present at baseline.Healthy volunteers (n = 5) performed a monitored 30-minute run to maintain a heart rate greater than 140 beats/min. Venous blood samples were collected before, 10 minutes after, and 24 hours after exercise. Endothelial progenitor cells were isolated and evaluated.Plasma levels of stromal cell-derived factor-1α significantly increased nearly two-fold immediately after exercise, with a nearly four-fold increase in circulating endothelial progenitor cells 24 hours later. The endothelial progenitor cells isolated following exercise demonstrated increased colony formation, proliferation, differentiation, and secretion of angiogenic cytokines. Postexercise endothelial progenitor cells also exhibited a more robust response to hypoxic stimulation.Exercise appears to mobilize endothelial progenitor cells and augment their function by means of stromal cell-derived factor 1α-dependent signaling. The population of endothelial progenitor cells mobilized following exercise is primed for vasculogenesis with increased capacity for proliferation, differentiation, secretion of cytokines, and responsiveness to hypoxia. Given the evidence demonstrating positive regenerative effects of exercise, this may be one possible mechanism for its benefits.

    View details for DOI 10.1097/PRS.0000000000000917

    View details for PubMedID 25626819

  • Transdermal deferoxamine prevents pressure-induced diabetic ulcers. Proceedings of the National Academy of Sciences of the United States of America Duscher, D., Neofytou, E., Wong, V. W., Maan, Z. N., Rennert, R. C., Inayathullah, M., Januszyk, M., Rodrigues, M., Malkovskiy, A. V., Whitmore, A. J., Walmsley, G. G., Galvez, M. G., Whittam, A. J., Brownlee, M., Rajadas, J., Gurtner, G. C. 2015; 112 (1): 94-99

    Abstract

    There is a high mortality in patients with diabetes and severe pressure ulcers. For example, chronic pressure sores of the heels often lead to limb loss in diabetic patients. A major factor underlying this is reduced neovascularization caused by impaired activity of the transcription factor hypoxia inducible factor-1 alpha (HIF-1α). In diabetes, HIF-1α function is compromised by a high glucose-induced and reactive oxygen species-mediated modification of its coactivator p300, leading to impaired HIF-1α transactivation. We examined whether local enhancement of HIF-1α activity would improve diabetic wound healing and minimize the severity of diabetic ulcers. To improve HIF-1α activity we designed a transdermal drug delivery system (TDDS) containing the FDA-approved small molecule deferoxamine (DFO), an iron chelator that increases HIF-1α transactivation in diabetes by preventing iron-catalyzed reactive oxygen stress. Applying this TDDS to a pressure-induced ulcer model in diabetic mice, we found that transdermal delivery of DFO significantly improved wound healing. Unexpectedly, prophylactic application of this transdermal delivery system also prevented diabetic ulcer formation. DFO-treated wounds demonstrated increased collagen density, improved neovascularization, and reduction of free radical formation, leading to decreased cell death. These findings suggest that transdermal delivery of DFO provides a targeted means to both prevent ulcer formation and accelerate diabetic wound healing with the potential for rapid clinical translation.

    View details for DOI 10.1073/pnas.1413445112

    View details for PubMedID 25535360

  • Evaluating the Effect of Cell Culture on Gene Expression in Primary Tissue Samples Using Microfluidic-Based Single Cell Transcriptional Analysis. Microarrays (Basel, Switzerland) Januszyk, M., Rennert, R. C., Sorkin, M., Maan, Z. N., Wong, L. K., Whittam, A. J., Whitmore, A., Duscher, D., Gurtner, G. C. 2015; 4 (4): 540-550

    Abstract

    Significant transcriptional heterogeneity is an inherent property of complex tissues such as tumors and healing wounds. Traditional methods of high-throughput analysis rely on pooling gene expression data from hundreds of thousands of cells and reporting a population-wide average that is unable to capture differences within distinct cell subsets. Recent advances in microfluidic technology have permitted the development of large-scale single cell analytic methods that overcome this limitation. The increased granularity afforded by such approaches allows us to answer the critical question of whether expansion in cell culture significantly alters the transcriptional characteristics of cells isolated from primary tissue. Here we examine an established population of human adipose-derived stem cells (ASCs) using a novel, microfluidic-based method for high-throughput transcriptional interrogation, coupled with advanced bioinformatic analysis, to evaluate the dynamics of single cell gene expression among primary, passage 0, and passage 1 stem cells. We find significant differences in the transcriptional profiles of cells from each group, as well as a considerable shift in subpopulation dynamics as those subgroups better able to adhere and proliferate under these culture conditions gradually emerge as dominant. Taken together, these findings reinforce the importance of using primary or very early passage cells in future studies.

    View details for DOI 10.3390/microarrays4040540

    View details for PubMedID 27600239

    View details for PubMedCentralID PMC4996408

  • En1 fibroblasts and melanoma. Melanoma management Walmsley, G. G., Hu, M. S., Maan, Z. N., Rinkevich, Y., Weissman, I. L., Longaker, M. T. 2015; 2 (3): 191–92

    View details for PubMedID 30190847

  • A mouse fetal skin model of scarless wound repair. Journal of visualized experiments : JoVE Walmsley, G. G., Hu, M. S., Hong, W. X., Maan, Z. N., Lorenz, H. P., Longaker, M. T. 2015: 52297-?

    Abstract

    Early in utero, but not in postnatal life, cutaneous wounds undergo regeneration and heal without formation of a scar. Scarless fetal wound healing occurs across species but is age dependent. The transition from a scarless to scarring phenotype occurs in the third trimester of pregnancy in humans and around embryonic day 18 (E18) in mice. However, this varies with the size of the wound with larger defects generating a scar at an earlier gestational age. The emergence of lineage tracing and other genetic tools in the mouse has opened promising new avenues for investigation of fetal scarless wound healing. However, given the inherently high rates of morbidity and premature uterine contraction associated with fetal surgery, investigations of fetal scarless wound healing in vivo require a precise and reproducible surgical model. Here we detail a reliable model of fetal scarless wound healing in the dorsum of E16.5 (scarless) and E18.5 (scarring) mouse embryos.

    View details for DOI 10.3791/52297

    View details for PubMedID 25650841

  • Stem Cell-Based Therapeutics to Improve Wound Healing. Plastic surgery international Hu, M. S., Leavitt, T., Malhotra, S., Duscher, D., Pollhammer, M. S., Walmsley, G. G., Maan, Z. N., Cheung, A. T., Schmidt, M., Huemer, G. M., Longaker, M. T., Lorenz, H. P. 2015; 2015: 383581-?

    Abstract

    Issues surrounding wound healing have garnered deep scientific interest as well as booming financial markets invested in novel wound therapies. Much progress has been made in the field, but it is unsurprising to find that recent successes reveal new challenges to be addressed. With regard to wound healing, large tissue deficits, recalcitrant wounds, and pathological scar formation remain but a few of our most pressing challenges. Stem cell-based therapies have been heralded as a promising means by which to surpass current limitations in wound management. The wide differentiation potential of stem cells allows for the possibility of restoring lost or damaged tissue, while their ability to immunomodulate the wound bed from afar suggests that their clinical applications need not be restricted to direct tissue formation. The clinical utility of stem cells has been demonstrated across dozens of clinical trials in chronic wound therapy, but there is hope that other aspects of wound care will inherit similar benefit. Scientific inquiry into stem cell-based wound therapy abounds in research labs around the world. While their clinical applications remain in their infancy, the heavy investment in their potential makes it a worthwhile subject to review for plastic surgeons, in terms of both their current and future applications.

    View details for DOI 10.1155/2015/383581

    View details for PubMedID 26649195

    View details for PubMedCentralID PMC4663003

  • A mouse fetal skin model of scarless wound repair. Journal of visualized experiments : JoVE Walmsley, G. G., Hu, M. S., Hong, W. X., Maan, Z. N., Lorenz, H. P., Longaker, M. T. 2015

    View details for DOI 10.3791/52297

    View details for PubMedID 25650841

  • Burns ITU admissions: Length of stay in specific levels of care for adult and paediatric patients BURNS Maan, Z. N., Frew, Q., Din, A. H., Unluer, Z., Smailes, S., Philp, B., El-Muttardi, N., Dziewulski, P. 2014; 40 (8): 1458-1462

    Abstract

    Prediction of total length of stay (LOS) for burns patients based on the total burn surface area (TBSA) is well accepted. Total LOS is a poor measure of resource consumption. Our aim was to determine the LOS in specific levels of care to better inform resource allocation. We performed a retrospective review of LOS in intensive treatment unit (ITU), burns high dependency unit (HDU) and burns low dependency unit (LDU) for all patients requiring ITU admission in a regional burns service from 2003 to 2011. During this period, our unit has admitted 1312 paediatric and 1445 adult patients to our Burns ITU. In both groups, ITU comprised 20% of the total LOS (mean 0.23±0.02 [adult] and 0.22±0.02 [paediatric] days per %burn). In adults, 33% of LOS was in HDU (0.52±0.06 days per %burn) and 48% (0.68±0.06 days per %burn) in LDU, while in children, 15% of LOS was in HDU (0.19±0.03 days per %burn) and 65% in LDU (0.70±0.06 days per %burn). When considering Burns ITU admissions, resource allocation ought to be planned according to expected LOS in specific levels of care rather than total LOS. The largest proportion of stay is in low dependency, likely due to social issues.

    View details for DOI 10.1016/j.burns.2014.07.026

    View details for Web of Science ID 000345364400007

  • Aging disrupts cell subpopulation dynamics and diminishes the function of mesenchymal stem cells SCIENTIFIC REPORTS Duscher, D., Rennert, R. C., Januszyk, M., Anghel, E., Maan, Z. N., Whittam, A. J., Perez, M. G., Kosaraju, R., Hu, M. S., Walmsley, G. G., Atashroo, D., Khong, S., Butte, A. J., Gurtner, G. C. 2014; 4

    Abstract

    Advanced age is associated with an increased risk of vascular morbidity, attributable in part to impairments in new blood vessel formation. Mesenchymal stem cells (MSCs) have previously been shown to play an important role in neovascularization and deficiencies in these cells have been described in aged patients. Here we utilize single cell transcriptional analysis to determine the effect of aging on MSC population dynamics. We identify an age-related depletion of a subpopulation of MSCs characterized by a pro-vascular transcriptional profile. Supporting this finding, we demonstrate that aged MSCs are also significantly compromised in their ability to support vascular network formation in vitro and in vivo. Finally, aged MSCs are unable to rescue age-associated impairments in cutaneous wound healing. Taken together, these data suggest that age-related changes in MSC population dynamics result in impaired therapeutic potential of aged progenitor cells. These findings have critical implications for therapeutic cell source decisions (autologous versus allogeneic) and indicate the necessity of strategies to improve functionality of aged MSCs.

    View details for DOI 10.1038/srep07144

    View details for Web of Science ID 000346178900001

    View details for PubMedID 25413454

    View details for PubMedCentralID PMC4239576

  • Diabetes irreversibly depletes bone marrow-derived mesenchymal progenitor cell subpopulations. Diabetes Januszyk, M., Sorkin, M., Glotzbach, J. P., Vial, I. N., Maan, Z. N., Rennert, R. C., Duscher, D., Thangarajah, H., Longaker, M. T., Butte, A. J., Gurtner, G. C. 2014; 63 (9): 3047-3056

    Abstract

    Diabetic vascular pathology is largely attributable to impairments in tissue recovery from hypoxia. Circulating progenitor cells have been postulated to play a role in ischemic recovery and deficiencies in these cells have been well described in diabetic patients. Here, we examine bone marrow-derived mesenchymal progenitor cells (BM-MPCs) that have previously been shown to be important for new blood vessel formation, and demonstrate significant deficits in the context of diabetes. Further, we determine that this dysfunction is attributable to intrinsic defects in diabetic BM-MPCs that are not correctable by restoring glucose homeostasis. We identify two transcriptionally distinct subpopulations that are selectively depleted by both type 1 and type 2 diabetes, and these subpopulations have pro-vasculogenic expression profiles, suggesting that they are vascular progenitor cells. These results suggest that the clinically observed deficits in progenitor cells may be attributable to selective and irreversible depletion of progenitor cell subsets in patients with diabetes.

    View details for DOI 10.2337/db13-1366

    View details for PubMedID 24740572

  • Transdermal Drug Delivery of Deferoxamine Accelerates Healing and Improves Quality of Diabetic Wounds Duscher, D., Maan, Z. N., Whittam, A. J., Rodrigues, M., Whitmore, A. J., Davis, C. R., Walmsley, G. G., Hu, M. S., Rajadas, J., Gurtner, G. C. ELSEVIER SCIENCE INC. 2014: S134–S135
  • Impaired Angiogenesis: A Critical Contributor to Problematic Fracture Healing in Diabetes Tevlin, R., Mc Ardle, A., Senarath-Yapa, K., Rodrigues, M., Maan, Z. N., Li, S., Chan, C. K., Brunski, J., Gurtner, G. C. ELSEVIER SCIENCE INC. 2014: S83
  • Identification and Targeted Inhibition of a Fibroblast Lineage Responsible for Skin Scarring and Cancer Stroma Walmsley, G. G., Rinkevich, Y., Hu, M. S., Montoro, D. T., McArdle, A., Zielins, E. R., Maan, Z. N., Lorenz, H., Weissman, I. L., Longaker, M. T. ELSEVIER SCIENCE INC. 2014: S84–S85
  • Reduced Regenerative Capacity of Aged Adipose Derived Stem Cells is Caused by Alterations of Cell Subpopulation Dynamics Duscher, D., Rennert, R. C., Januszyk, M., Maan, Z. N., Whittam, A. J., Hu, M. S., Walmsley, G. G., Atashroo, D., Longaker, M. T., Gurtner, G. C. ELSEVIER SCIENCE INC. 2014: S136
  • Endothelial Cell Derived Stromal-Derived Factor-1 (SDF-1) Regulates Neovascularization and Fibroblast Physiology in Response to Ischemia Maan, Z. N., Whittam, A. J., Duscher, D., Hu, M. S., Rennert, R. C., Fischer, L. H., Walmsley, G. G., Whitmore, A. J., Longaker, M. T., Gurtner, G. C. ELSEVIER SCIENCE INC. 2014: S82
  • Noncontact, low-frequency ultrasound therapy enhances neovascularization and wound healing in diabetic mice. Plastic and reconstructive surgery Maan, Z. N., Januszyk, M., Rennert, R. C., Duscher, D., Rodrigues, M., Fujiwara, T., Ho, N., Whitmore, A., Hu, M. S., Longaker, M. T., Gurtner, G. C. 2014; 134 (3): 402e-11e

    Abstract

    Chronic wounds are a major source of morbidity for patients and represent a significant health burden. Implementing noninvasive techniques that accelerate healing of these wounds would provide great benefit. Ultrasound appears to be an effective modality for the treatment of chronic wounds in humans. MIST Therapy is a noncontact, low-frequency ultrasound treatment delivered through a saline mist. A variety of mechanisms have been proposed to explain the efficacy of ultrasound therapy, but the underlying molecular and cellular pathways impacted by this technique remain unclear. The in vivo effect of noncontact, low-frequency ultrasound was therefore examined in a humanized excisional wound model.The treatment group received noncontact, low-frequency ultrasound therapy three times per week, whereas the control group received a standard dressing change. Wounds were photographed at regular intervals to calculate healing kinetics. Wound tissue was harvested and processed for histology, quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay.The MIST group demonstrated significantly accelerated wound healing, with 17.3 days to wound closure compared with 24 days in the controls (p < 0.05). This improvement became evident by day 9, with healing evidenced by significantly decreased mean wound area relative to original size (68 percent versus 80 percent; p < 0.01). Expression of markers of neovascularization (stromal cell-derived factor 1, vascular endothelial growth factor, and CD31) was also increased in the wound beds of noncontact, low-frequency ultrasound-treated mice compared with controls.Noncontact, low-frequency ultrasound treatment improves neovascularization and wound closure rates in excisional wounds for diabetic mice, likely because of the stimulated release of angiogenic factors.

    View details for DOI 10.1097/PRS.0000000000000467

    View details for PubMedID 25158717

  • Gene expression in fetal murine keratinocytes and fibroblasts JOURNAL OF SURGICAL RESEARCH Hu, M. S., Januszyk, M., Hong, W. X., Walmsley, G. G., Zielins, E. R., Atashroo, D. A., Maan, Z. N., McArdle, A., Takanishi, D. M., Gurtner, G. C., Longaker, M. T., Lorenz, H. P. 2014; 190 (1): 344-357

    Abstract

    Early fetuses heal wounds without the formation of a scar. Many studies have attempted to explain this remarkable phenomenon. However, the exact mechanism remains unknown. Herein, we examine the predominant cell types of the epidermis and dermis-the keratinocyte and fibroblast-during different stages of fetal development to better understand the changes that lead to scarring wound repair versus regeneration.Keratinocytes and fibroblasts were harvested and cultured from the dorsal skin of time-dated BALB/c fetuses. Total RNA was isolated and microarray analysis was performed using chips with 42,000 genes. Significance analysis of microarrays was used to select genes with >2-fold expression differences with a false discovery rate <2. Enrichment analysis was performed on significant genes to identify differentially expressed pathways.By comparing the gene expression profile of keratinocytes from E16 versus E18 fetuses, we identified 24 genes that were downregulated at E16. Analysis of E16 and E18 fibroblasts revealed 522 differentially expressed genes. Enrichment analysis showed the top 20 signaling pathways that were downregulated in E16 keratinocytes and upregulated or downregulated in E16 fibroblasts.Our data reveal 546 differentially expressed genes in keratinocytes and fibroblasts between the scarless and scarring transition. In addition, a total of 60 signaling pathways have been identified to be either upregulated or downregulated in these cell types. The genes and pathways recognized by our study may prove to be essential targets that may discriminate between fetal wound regeneration and adult wound repair.

    View details for DOI 10.1016/j.jss.2014.02.030

    View details for Web of Science ID 000338444700051

  • Tissue engineering and regenerative repair in wound healing. Annals of biomedical engineering Hu, M. S., Maan, Z. N., Wu, J., Rennert, R. C., Hong, W. X., Lai, T. S., Cheung, A. T., Walmsley, G. G., Chung, M. T., McArdle, A., Longaker, M. T., Lorenz, H. P. 2014; 42 (7): 1494-1507

    Abstract

    Wound healing is a highly evolved defense mechanism against infection and further injury. It is a complex process involving multiple cell types and biological pathways. Mammalian adult cutaneous wound healing is mediated by a fibroproliferative response leading to scar formation. In contrast, early to mid-gestational fetal cutaneous wound healing is more akin to regeneration and occurs without scar formation. This early observation has led to extensive research seeking to unlock the mechanism underlying fetal scarless regenerative repair. Building upon recent advances in biomaterials and stem cell applications, tissue engineering approaches are working towards a recapitulation of this phenomenon. In this review, we describe the elements that distinguish fetal scarless and adult scarring wound healing, and discuss current trends in tissue engineering aimed at achieving scarless tissue regeneration.

    View details for DOI 10.1007/s10439-014-1010-z

    View details for PubMedID 24788648

  • Mechanotransduction and fibrosis JOURNAL OF BIOMECHANICS Duscher, D., Maan, Z. N., Wong, V. W., Rennert, R. C., Januszyk, M., Rodrigues, M., Hu, M., Whitmore, A. J., Whittam, A. J., Longaker, M. T., Gurtner, G. C. 2014; 47 (9): 1997-2005

    Abstract

    Scarring and tissue fibrosis represent a significant source of morbidity in the United States. Despite considerable research focused on elucidating the mechanisms underlying cutaneous scar formation, effective clinical therapies are still in the early stages of development. A thorough understanding of the various signaling pathways involved is essential to formulate strategies to combat fibrosis and scarring. While initial efforts focused primarily on the biochemical mechanisms involved in scar formation, more recent research has revealed a central role for mechanical forces in modulating these pathways. Mechanotransduction, which refers to the mechanisms by which mechanical forces are converted to biochemical stimuli, has been closely linked to inflammation and fibrosis and is believed to play a critical role in scarring. This review provides an overview of our current understanding of the mechanisms underlying scar formation, with an emphasis on the relationship between mechanotransduction pathways and their therapeutic implications.

    View details for DOI 10.1016/j.jbiomech.2014.03.031

    View details for Web of Science ID 000338621900009

  • Diabetes impairs the angiogenic potential of adipose-derived stem cells by selectively depleting cellular subpopulations STEM CELL RESEARCH & THERAPY Rennert, R. C., Sorkin, M., Januszyk, M., Duscher, D., Kosaraju, R., Chung, M. T., Lennon, J., Radiya-Dixit, A., Raghvendra, S., Maan, Z. N., Hu, M. S., Rajadas, J., Rodrigues, M., Gurtner, G. C. 2014; 5

    Abstract

    Pathophysiologic changes associated with diabetes impair new blood vessel formation and wound healing. Mesenchymal stem cells derived from adipose tissue (ASCs) have been used clinically to promote healing, although it remains unclear whether diabetes impairs their functional and therapeutic capacity.In this study, we examined the impact of diabetes on the murine ASC niche, as well as on the potential of isolated cells to promote neovascularization in vitro and in vivo. A novel single cell analytical approach was used to interrogate ASC heterogeneity and subpopulation dynamics in this pathologic setting.Our results demonstrate that diabetes alters the ASC niche in situ, and that diabetic ASCs are compromised in their ability to establish a vascular network both in vitro and in vivo. Moreover, these diabetic cells were ineffective in promoting soft tissue neovascularization and wound healing. Single cell transcriptional analysis identified a subpopulation of cells which was diminished in both type 1 and type 2 models of diabetes. These cells were characterized by the high expression of genes known to be important for new blood vessel growth.Perturbations in specific cellular subpopulations, visible only on a single cell level, represent a previously unreported mechanism for the dysfunction of diabetic ASCs. These data suggest that the utility of autologous ASCs for cell-based therapies in diabetic patients may be limited, and that interventions to improve cell function before application are warranted.

    View details for DOI 10.1186/scrt468

    View details for Web of Science ID 000338465500001

  • Abstract 140: identification, characterization, and prospective isolation of a fibroblast lineage contributing to dermal development, cutaneous scarring, radiation fibrosis, and cancer stroma. Plastic and reconstructive surgery Walmsley, G. G., Rinkevich, Y., Hu, M. S., McArdle, A., Maan, Z. N., Lorenz, H. P., Weissman, I. L., Longaker, M. T. 2014; 133 (3): 157-?

    View details for DOI 10.1097/01.prs.0000444968.20280.4d

    View details for PubMedID 25942251

  • Abstract 10: Global and Endothelial Cell Specific Deletion of SDF-1 Results in Delayed Wound Healing. Plastic and reconstructive surgery Maan, Z. N., Ho, N., Rennert, R. C., Duscher, D., Sorkin, M., Rodrigues, M., Chen, J., Vial, I. N., Januszyk, M., Findlay, M., Hu, M., Walmsley, G., Longaker, M. T., Gurtner, G. C. 2014; 133 (3): 20-?

    View details for DOI 10.1097/01.prs.0000444963.66915.ba

    View details for PubMedID 25942121

  • Abstract 135: improved engraftment of autologous skin grafts in diabetic mice with adipose-derived stem cells. Plastic and reconstructive surgery Hu, M., Hong, W. X., Senarath-Yapa, K., Zimmermann, A., Chung, M., Esquivel, M., McArdle, A., Walmsley, G., Maan, Z., Garza, R., Lorenz, H. P., Longaker, M. 2014; 133 (3): 151-?

    View details for DOI 10.1097/01.prs.0000444962.89785.8e

    View details for PubMedID 25942246

  • Abstract 8: SDF-1 Regulates Adipose Niche Homeostasis and Adipose Derived Stromal Cell Function. Plastic and reconstructive surgery Maan, Z. N., Rennert, R. C., Duscher, D., Januszyk, M., Paik, K., Chung, M. T., Paik, K., Fujiwara, T., Rodrigues, M., Ho, N., Baker, H., Perez, M., Hu, M., Sorkin, M., Longaker, M. T., Gurtner, G. C. 2014; 133 (3): 15-16

    View details for DOI 10.1097/01.prs.0000444941.23852.ce

    View details for PubMedID 25942119

  • Abstract 15: Characterization of the Endothelial Progenitor Cell from Adult Tissue using Vav/Cre RFP-GFP Murine Model and Single Cell Microfluidics. Plastic and reconstructive surgery Rodrigues, M., Rennert, R. C., Bishop, S., Januszyk, M., Maan, Z., Sorkin, M., Duscher, D., Gurtner, G. C. 2014; 133 (3): 25-?

    View details for DOI 10.1097/01.prs.0000445018.79483.78

    View details for PubMedID 25942126

  • Wound healing: an update REGENERATIVE MEDICINE Zielins, E. R., Atashroo, D. A., Maan, Z. N., Duscher, D., Walmsley, G. G., Marecic, O., Hu, M., Senarath-Yapa, K., McArdle, A., Tevlin, R., Wearda, T., Paik, K. J., Duldulao, C., Hong, W. X., Gurtner, G. C., Longaker, M. T. 2014; 9 (6): 817-830

    Abstract

    Wounds, both chronic and acute, continue to be a tremendous socioeconomic burden. As such, technologies drawn from many disciplines within science and engineering are constantly being incorporated into innovative wound healing therapies. While many of these therapies are experimental, they have resulted in new insights into the pathophysiology of wound healing, and in turn the development of more specialized treatments for both normal and abnormal wound healing states. Herein, we review some of the emerging technologies that are currently being developed to aid and improve wound healing after cutaneous injury.

    View details for DOI 10.2217/RME.14.54

    View details for Web of Science ID 000345620600012

  • Mechanotransduction and fibrosis. Journal of biomechanics Duscher, D., Maan, Z. N., Wong, V. W., Rennert, R. C., Januszyk, M., Rodrigues, M., Hu, M., Whitmore, A. J., Whittam, A. J., Longaker, M. T., Gurtner, G. C. 2014

    Abstract

    Scarring and tissue fibrosis represent a significant source of morbidity in the United States. Despite considerable research focused on elucidating the mechanisms underlying cutaneous scar formation, effective clinical therapies are still in the early stages of development. A thorough understanding of the various signaling pathways involved is essential to formulate strategies to combat fibrosis and scarring. While initial efforts focused primarily on the biochemical mechanisms involved in scar formation, more recent research has revealed a central role for mechanical forces in modulating these pathways. Mechanotransduction, which refers to the mechanisms by which mechanical forces are converted to biochemical stimuli, has been closely linked to inflammation and fibrosis and is believed to play a critical role in scarring. This review provides an overview of our current understanding of the mechanisms underlying scar formation, with an emphasis on the relationship between mechanotransduction pathways and their therapeutic implications.

    View details for PubMedID 24709567

  • Gene expression in fetal murine keratinocytes and fibroblasts. The Journal of surgical research Hu, M. S., Januszyk, M., Hong, W. X., Walmsley, G. G., Zielins, E. R., Atashroo, D. A., Maan, Z. N., McArdle, A., Takanishi, D. M., Gurtner, G. C., Longaker, M. T., Lorenz, H. P. 2014

    Abstract

    Early fetuses heal wounds without the formation of a scar. Many studies have attempted to explain this remarkable phenomenon. However, the exact mechanism remains unknown. Herein, we examine the predominant cell types of the epidermis and dermis-the keratinocyte and fibroblast-during different stages of fetal development to better understand the changes that lead to scarring wound repair versus regeneration.Keratinocytes and fibroblasts were harvested and cultured from the dorsal skin of time-dated BALB/c fetuses. Total RNA was isolated and microarray analysis was performed using chips with 42,000 genes. Significance analysis of microarrays was used to select genes with >2-fold expression differences with a false discovery rate <2. Enrichment analysis was performed on significant genes to identify differentially expressed pathways.By comparing the gene expression profile of keratinocytes from E16 versus E18 fetuses, we identified 24 genes that were downregulated at E16. Analysis of E16 and E18 fibroblasts revealed 522 differentially expressed genes. Enrichment analysis showed the top 20 signaling pathways that were downregulated in E16 keratinocytes and upregulated or downregulated in E16 fibroblasts.Our data reveal 546 differentially expressed genes in keratinocytes and fibroblasts between the scarless and scarring transition. In addition, a total of 60 signaling pathways have been identified to be either upregulated or downregulated in these cell types. The genes and pathways recognized by our study may prove to be essential targets that may discriminate between fetal wound regeneration and adult wound repair.

    View details for PubMedID 24726057

  • Understanding regulatory pathways of neovascularization in diabetes. Expert review of endocrinology & metabolism Maan, Z. N., Rodrigues, M., Rennert, R. C., Whitmore, A., Duscher, D., Januszyk, M., Hu, M., Whittam, A. J., Davis, C. R., Gurtner, G. C. 2014; 9 (5): 487–501

    Abstract

    Diabetes mellitus and its associated comorbidities represent a significant health burden worldwide. Vascular dysfunction is the major contributory factor in the development of these comorbidities, which include impaired wound healing, cardiovascular disease and proliferative diabetic retinopathy. While the etiology of abnormal neovascularization in diabetes is complex and paradoxical, the dysregulation of the varied processes contributing to the vascular response are due in large part to the effects of hyperglycemia. In this review, we explore the mechanisms by which hyperglycemia disrupts chemokine expression and function, including the critical hypoxia inducible factor-1 axis. We place particular emphasis on the therapeutic potential of strategies addressing these pathways; as such targeted approaches may one day help alleviate the healthcare burden of diabetic sequelae.

    View details for PubMedID 30736211

  • Aging disrupts cell subpopulation dynamics and diminishes the function of mesenchymal stem cells. Scientific reports Duscher, D., Rennert, R. C., Januszyk, M., Anghel, E., Maan, Z. N., Whittam, A. J., Perez, M. G., Kosaraju, R., Hu, M. S., Walmsley, G. G., Atashroo, D., Khong, S., Butte, A. J., Gurtner, G. C. 2014; 4: 7144-?

    Abstract

    Advanced age is associated with an increased risk of vascular morbidity, attributable in part to impairments in new blood vessel formation. Mesenchymal stem cells (MSCs) have previously been shown to play an important role in neovascularization and deficiencies in these cells have been described in aged patients. Here we utilize single cell transcriptional analysis to determine the effect of aging on MSC population dynamics. We identify an age-related depletion of a subpopulation of MSCs characterized by a pro-vascular transcriptional profile. Supporting this finding, we demonstrate that aged MSCs are also significantly compromised in their ability to support vascular network formation in vitro and in vivo. Finally, aged MSCs are unable to rescue age-associated impairments in cutaneous wound healing. Taken together, these data suggest that age-related changes in MSC population dynamics result in impaired therapeutic potential of aged progenitor cells. These findings have critical implications for therapeutic cell source decisions (autologous versus allogeneic) and indicate the necessity of strategies to improve functionality of aged MSCs.

    View details for DOI 10.1038/srep07144

    View details for PubMedID 25413454

  • Wound healing: an update. Regenerative medicine Zielins, E. R., Atashroo, D. A., Maan, Z. N., Duscher, D., Walmsley, G. G., Hu, M., Senarath-Yapa, K., McArdle, A., Tevlin, R., Wearda, T., Paik, K. J., Duldulao, C., Hong, W. X., Gurtner, G. C., Longaker, M. T. 2014; 9 (6): 817-830

    Abstract

    Wounds, both chronic and acute, continue to be a tremendous socioeconomic burden. As such, technologies drawn from many disciplines within science and engineering are constantly being incorporated into innovative wound healing therapies. While many of these therapies are experimental, they have resulted in new insights into the pathophysiology of wound healing, and in turn the development of more specialized treatments for both normal and abnormal wound healing states. Herein, we review some of the emerging technologies that are currently being developed to aid and improve wound healing after cutaneous injury.

    View details for DOI 10.2217/rme.14.54

    View details for PubMedID 25431917

  • Burns ITU admissions: length of stay in specific levels of care for adult and paediatric patients. Burns : journal of the International Society for Burn Injuries Maan, Z. N., Frew, Q., Din, A. H., Unluer, Z., Smailes, S., Philp, B., El-Muttardi, N., Dziewulski, P. 2014; 40 (8): 1458–62

    Abstract

    Prediction of total length of stay (LOS) for burns patients based on the total burn surface area (TBSA) is well accepted. Total LOS is a poor measure of resource consumption. Our aim was to determine the LOS in specific levels of care to better inform resource allocation. We performed a retrospective review of LOS in intensive treatment unit (ITU), burns high dependency unit (HDU) and burns low dependency unit (LDU) for all patients requiring ITU admission in a regional burns service from 2003 to 2011. During this period, our unit has admitted 1312 paediatric and 1445 adult patients to our Burns ITU. In both groups, ITU comprised 20% of the total LOS (mean 0.23±0.02 [adult] and 0.22±0.02 [paediatric] days per %burn). In adults, 33% of LOS was in HDU (0.52±0.06 days per %burn) and 48% (0.68±0.06 days per %burn) in LDU, while in children, 15% of LOS was in HDU (0.19±0.03 days per %burn) and 65% in LDU (0.70±0.06 days per %burn). When considering Burns ITU admissions, resource allocation ought to be planned according to expected LOS in specific levels of care rather than total LOS. The largest proportion of stay is in low dependency, likely due to social issues.

    View details for PubMedID 25155115

  • Epidermal or dermal specific knockout of PHD-2 enhances wound healing and minimizes ischemic injury. PloS one Zimmermann, A. S., Morrison, S. D., Hu, M. S., Li, S., Nauta, A., Sorkin, M., Meyer, N. P., Walmsley, G. G., Maan, Z. N., Chan, D. A., Gurtner, G. C., Giaccia, A. J., Longaker, M. T. 2014; 9 (4)

    Abstract

    Hypoxia-inducible factor (HIF)-1α, part of the heterodimeric transcription factor that mediates the cellular response to hypoxia, is critical for the expression of multiple angiogenic growth factors, cell motility, and the recruitment of endothelial progenitor cells. Inhibition of the oxygen-dependent negative regulator of HIF-1α, prolyl hydroxylase domain-2 (PHD-2), leads to increased HIF-1α and mimics various cellular and physiological responses to hypoxia. The roles of PHD-2 in the epidermis and dermis have not been clearly defined in wound healing.Epidermal and dermal specific PHD-2 knockout (KO) mice were developed in a C57BL/6J (wild type) background by crossing homozygous floxed PHD-2 mice with heterozygous K14-Cre mice and heterozygous Col1A2-Cre-ER mice to get homozygous floxed PHD-2/heterozygous K14-Cre and homozygous floxed PHD-2/heterozygous floxed Col1A2-Cre-ER mice, respectively. Ten to twelve-week-old PHD-2 KO and wild type (WT) mice were subjected to wounding and ischemic pedicle flap model. The amount of healing was grossly quantified with ImageJ software. Western blot and qRT-PCR was run on protein and RNA from primary cells cultured in vitro.qRT-PCR demonstrated a significant decrease of PHD-2 in keratinocytes and fibroblasts derived from tissue specific KO mice relative to control mice (*p<0.05). Western blot analysis showed a significant increase in HIF-1α and VEGF protein levels in PHD-2 KO mice relative to control mice (*p<0.05). PHD-2 KO mice showed significantly accelerated wound closure relative to WT (*p<0.05). When ischemia was analyzed at day nine post-surgery in a flap model, the PHD-2 tissue specific knockout mice showed significantly more viable flaps than WT (*p<0.05).PHD-2 plays a significant role in the rates of wound healing and response to ischemic insult in mice. Further exploration shows PHD-2 KO increases cellular levels of HIF-1α and this increase leads to the transcription of downstream angiogenic factors such as VEGF.

    View details for DOI 10.1371/journal.pone.0093373

    View details for PubMedID 24695462

    View details for PubMedCentralID PMC3973687

  • Understanding regulatory pathways of neovascularization in diabetes EXPERT REVIEW OF ENDOCRINOLOGY & METABOLISM Maan, Z. N., Rodrigues, M., Rennert, R. C., Whitmore, A., Duscher, D., Januszyk, M., Hu, M., Whittam, A. J., Davis, C. R., Gurtner, G. C. 2014; 9 (5): 487–501
  • Sutureless Microvascular Anastomosis for Clinical Application Using Poloxamer 188 as an Optimal Transient Thermoreversible Stent Journal of the American College of Surgeons Davis, C. R., Rappleye, T. C., Than, P., Whitmore, A., Maan, Z. N., Rodrigues, M., Bishop, S., Gurtner, G. C. 2014; 219 (3): S89
  • Epidermal or Dermal Specific Knockout of PHD-2 Enhances Wound Healing and Minimizes Ischemic Injury. PloS one Zimmermann, A. S., Morrison, S. D., Hu, M. S., Li, S., Nauta, A., Sorkin, M., Meyer, N. P., Walmsley, G. G., Maan, Z. N., Chan, D. A., Gurtner, G. C., Giaccia, A. J., Longaker, M. T. 2014; 9 (4)

    View details for DOI 10.1371/journal.pone.0093373

    View details for PubMedID 24695462

  • Biological therapies for the treatment of cutaneous wounds: Phase III and launched therapies EXPERT OPINION ON BIOLOGICAL THERAPY Rennert, R. C., Rodrigues, M., Wong, V. W., Duscher, D., Hu, M., Maan, Z., Sorkin, M., Gurtner, G. C., Longaker, M. T. 2013; 13 (11): 1523-1541

    Abstract

    Normal wound healing mechanisms can be overwhelmed in the setting of complex acute and chronic tissue injury. Biological therapies are designed to augment and/or restore the body's natural wound healing abilities. There are a variety of available and emerging technologies utilizing this approach that have demonstrated the ability to augment wound healing.In this review, the clinical data on launched and emerging biological therapies for wound healing applications are summarized. The methodologies discussed include biological skin equivalents, growth factors/small molecules and stem cell-based therapies.While many products possess convincing clinical data demonstrating their efficacy in comparison to standard treatment options, more robust, controlled studies are needed to determine the relative value among established and emerging biological therapies. Future bioengineering and stem cell-based approaches are of particular interest due to the simultaneous correction of multiple deficiencies present in the nonhealing wound.

    View details for DOI 10.1517/14712598.2013.842972

    View details for Web of Science ID 000325712100007

    View details for PubMedID 24093722

  • Biological therapies for the treatment of cutaneous wounds: phase III and launched therapies. Expert opinion on biological therapy Rennert, R. C., Rodrigues, M., Wong, V. W., Duscher, D., Hu, M., Maan, Z., Sorkin, M., Gurtner, G. C., Longaker, M. T. 2013; 13 (11): 1523-1541

    Abstract

    Normal wound healing mechanisms can be overwhelmed in the setting of complex acute and chronic tissue injury. Biological therapies are designed to augment and/or restore the body's natural wound healing abilities. There are a variety of available and emerging technologies utilizing this approach that have demonstrated the ability to augment wound healing.In this review, the clinical data on launched and emerging biological therapies for wound healing applications are summarized. The methodologies discussed include biological skin equivalents, growth factors/small molecules and stem cell-based therapies.While many products possess convincing clinical data demonstrating their efficacy in comparison to standard treatment options, more robust, controlled studies are needed to determine the relative value among established and emerging biological therapies. Future bioengineering and stem cell-based approaches are of particular interest due to the simultaneous correction of multiple deficiencies present in the nonhealing wound.

    View details for DOI 10.1517/14712598.2013.842972

    View details for PubMedID 24093722

  • NextGen Speaks SCIENCE Maan, Z. N. 2013; 341 (6141): 29

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