Bio

Clinical Focus


  • Pediatric Surgery

Academic Appointments


Professional Education


  • Fellowship: Children's Mercy Hospital Surgical Critical Care Fellowship (2020) MO
  • Fellowship: Childrens Mercy Hospital Pediatric Surgery Fellowship (2019) MO
  • Board Certification: American Board of Surgery, General Surgery (2017)
  • Residency: Stanford University General Surgery Residency (2017) CA
  • Internship: Saint Joseph Mercy Ann Arbor General Surgery Residency (2010) MI
  • Medical Education: University of Minnesota School of Medicine Registrar (2008) MN

Publications

All Publications


  • Cerebral Fat Embolism in a Trauma Patient with Captured Imaging of Echogenic Emboli in the Inferior Vena Cava JOURNAL OF MEDICAL ULTRASOUND Wang, N. N., Panda, N., Hyun, J. S., Barounis, D., Weiser, T. G. 2016; 24 (4): 162–65
  • Salvage of a failed open gastrocutaneous fistula repair with an endoscopic over-the-scope clip JOURNAL OF PEDIATRIC SURGERY CASE REPORTS Jaramillo, J., Hyun, J., Abrajano, C., Koppolu, R., Chao, S., Hartman, G., Wall, J. 2016; 8: 40–41
  • Studies in Fat Grafting: Part I. Effects of Injection Technique on In Vitro Fat Viability and In Vivo Volume Retention PLASTIC AND RECONSTRUCTIVE SURGERY Chung, M. T., Paik, K. J., Atashroo, D. A., Hyun, J. S., McArdle, A., Senarath-Yapa, K., Zielins, E. R., Tevlin, R., Duldulao, C., Hu, M. S., Walmsley, G. G., Parisi-Amon, A., Momeni, A., Rimsa, J. R., Commons, G. W., Gurtner, G. C., Wan, D. C., Longaker, M. T. 2014; 134 (1): 29-38

    Abstract

    Fat grafting has become increasingly popular for the correction of soft tissue deficits at many sites throughout the body. Long-term outcomes, however, depend on delivery of fat in the least traumatic fashion to optimize viability of the transplanted tissue. In this study, we compare the biologic properties of fat following injection using two methods.Lipoaspiration samples were obtained from five female donors and cellular viability, proliferation, and lipolysis were evaluated following injection using either a modified Coleman technique or an automated, low shear device. Comparisons were made to minimally processed, uninjected fat. Volume retention was also measured over twelve weeks following injection of fat under the scalp of immunodeficient mice using either the modified Coleman technique or the Adipose Tissue Injector. Finally, fat grafts were analyzed histologically.Fat viability and cellular proliferation were both significantly greater with the Adipose Tissue Injector relative to injection with the modified Coleman technique. In contrast, significantly less lipolysis was noted using the automated device. In vivo fat volume retention was significantly greater than with the modified Coleman technique at 4, 6, 8, and 12 week time points. This corresponded with significantly greater histological scores for healthy fat and lower scores for injury following injection with the device.Biological properties of injected tissues reflect how disruptive and harmful techniques for placement of fat may be, and our in vitro and in vivo data both support the use of the automated, low shear devices compared to the modified Coleman technique.

    View details for DOI 10.1097/PRS.0000000000000290

    View details for Web of Science ID 000338116400042

  • Induced pluripotent stem cells in regenerative medicine and disease modeling. Current stem cell research & therapy Walmsley, G. G., Hyun, J., McArdle, A., Senarath-Yapa, K., Hu, M. S., Chung, M. T., Wong, V. W., Longaker, M. T., Wan, D. C. 2014; 9 (2): 73-81

    Abstract

    In 2006, Dr. Yamanaka created the induced pluripotent stem cell (iPSC) by reprogramming adult fibroblasts back to an immature, pluripotent state. Effectively bypassing the ethical constraints of human embryonic stem cells, iPSCs have expanded the horizons of regenerative medicine by offering a means to derive autologous patient-matched cells and tissues for clinical transplantation. However, persisting safety concerns must be addressed prior to their widespread clinical application. In this review, we discuss the history of iPSCs, derivation strategies, and current research involving gene therapy and disease modeling. We review the potential of iPSCs for improving a range of cell-based therapies and obstacles to their clinical implementation.

    View details for PubMedID 24359141

  • Isolation of human adipose-derived stromal cells using laser-assisted liposuction and their therapeutic potential in regenerative medicine. Stem cells translational medicine Chung, M. T., Zimmermann, A. S., Paik, K. J., Morrison, S. D., Hyun, J. S., Lo, D. D., McArdle, A., Montoro, D. T., Walmsley, G. G., Senarath-Yapa, K., Sorkin, M., Rennert, R., Chen, H., Chung, A. S., Vistnes, D., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2013; 2 (10): 808-817

    Abstract

    Harvesting adipose-derived stromal cells (ASCs) for tissue engineering is frequently done through liposuction. However, several different techniques exist. Although third-generation ultrasound-assisted liposuction has been shown to not have a negative effect on ASCs, the impact of laser-assisted liposuction on the quality and differentiation potential of ASCs has not been studied. Therefore, ASCs were harvested from laser-assisted lipoaspirate and suction-assisted lipoaspirate. Next, in vitro parameters of cell yield, cell viability and proliferation, surface marker phenotype, osteogenic differentiation, and adipogenic differentiation were performed. Finally, in vivo bone formation was assessed using a critical-sized cranial defect in athymic nude mice. Although ASCs isolated from suction-assisted lipoaspirate and laser-assisted lipoaspirate both successfully underwent osteogenic and adipogenic differentiation, the cell yield, viability, proliferation, and frequency of ASCs (CD34(+)CD31(-)CD45(-)) in the stromal vascular fraction were all significantly less with laser-assisted liposuction in vitro (p < .05). In vivo, quantification of osseous healing by micro-computed tomography revealed significantly more healing with ASCs isolated from suction-assisted lipoaspirate relative to laser-assisted lipoaspirate at the 4-, 6-, and 8-week time points (p < .05). Therefore, as laser-assisted liposuction appears to negatively impact the biology of ASCs, cell harvest using suction-assisted liposuction is preferable for tissue-engineering purposes.

    View details for DOI 10.5966/sctm.2012-0183

    View details for PubMedID 24018794

    View details for PubMedCentralID PMC3785265

  • Molecular analysis and differentiation capacity of adipose-derived stem cells from lymphedema tissue. Plastic and reconstructive surgery Levi, B., Glotzbach, J. P., Sorkin, M., Hyun, J., Januszyk, M., Wan, D. C., Li, S., Nelson, E. R., Longaker, M. T., Gurtner, G. C. 2013; 132 (3): 580-589

    Abstract

    Many breast cancer patients are plagued by the disabling complication of upper limb lymphedema after axillary surgery. Conservative treatments using massage and compression therapy do not offer a lasting relief, as they fail to address the chronic transformation of edema into excess adipose tissue. Liposuction to address the adipose nature of the lymphedema has provided an opportunity for a detailed analysis of the stromal fraction of lymphedema-associated fat to clarify the molecular mechanisms for this adipogenic transformation.Adipose-derived stem cells were harvested from human lipoaspirate of the upper extremity from age-matched patients with lymphedema (n = 3) or subcutaneous adipose tissue from control patients undergoing cosmetic procedures (n = 3). Immediately after harvest, adipose-derived stem cells were analyzed using single-cell transcriptional profiling techniques. Osteogenic, adipogenic, and vasculogenic gene expression and differentiation were assessed by quantitative real-time polymerase chain reaction and standard in vitro differentiation assays.Differential transcriptional clusters of adipose-derived stem cells were found between lymphedema and subcutaneous fat. Interestingly, lymphedema-associated stem cells had a much higher adipogenic gene expression and enhanced ability to undergo adipogenic differentiation. Conversely, they had lower vasculogenic gene expression and diminished capability to form tubules in vitro, whereas the osteogenic differentiation capacity was not significantly altered.Adipose-derived stem cells from extremities affected by lymphedema appear to exhibit transcriptional profiles similar to those of abdominal adipose-derived stem cells; however, their adipogenic differentiation potential is strongly increased and their vasculogenic capacity is compromised. These results suggest that the underlying pathophysiology of lymphedema drives adipose-derived stem cells toward adipogenic differentiation.

    View details for DOI 10.1097/PRS.0b013e31829ace13

    View details for PubMedID 23985633

  • Enhancing in vivo survival of adipose-derived stromal cells through bcl-2 overexpression using a minicircle vector. Stem cells translational medicine Hyun, J., Grova, M., Nejadnik, H., Lo, D., Morrison, S., Montoro, D., Chung, M., Zimmermann, A., Walmsley, G. G., Lee, M., Daldrup-Link, H., Wan, D. C., Longaker, M. T. 2013; 2 (9): 690-702

    Abstract

    Tissue regeneration using progenitor cell-based therapy has the potential to aid in the healing of a diverse range of pathologies, ranging from short-gut syndrome to spinal cord lesions. However, there are numerous hurdles to be overcome prior to the widespread application of these cells in the clinical setting. One of the primary barriers to effective stem cell therapy is the hostile environment that progenitor cells encounter in the clinical injury wound setting. In order to promote cellular survival, stem cell differentiation, and participation in tissue regeneration, relevant cells and delivery scaffolds must be paired with strategies to prevent cell death to ensure that these cells can survive to form de novo tissue. The Bcl-2 protein is a prosurvival member of a family of proteins that regulate the mitochondrial pathway of apoptosis. Using several strategies to overexpress the Bcl-2 protein, we demonstrated a decrease in the mediators of apoptosis in vitro and in vivo. This was shown through the use of two different clinical tissue repair models. Cells overexpressing Bcl-2 not only survived within the wound environment at a statistically significantly higher rate than control cells, but also increased tissue regeneration. Finally, we used a nonintegrating minicircle technology to achieve this in a potentially clinically applicable strategy for stem cell therapy.

    View details for DOI 10.5966/sctm.2013-0035

    View details for PubMedID 23934910

  • Enhancing stem cell survival in vivo for tissue repair BIOTECHNOLOGY ADVANCES Hyun, J. S., Tran, M. C., Wong, V. W., Chung, M. T., Lo, D. D., Montoro, D. T., Wan, D. C., Longaker, M. T. 2013; 31 (5): 736-743

    Abstract

    The ability to use progenitor cells for regenerative medicine remains an evolving but elusive clinical goal. A serious obstacle towards widespread use of stem cells for tissue regeneration is the challenges that face these cells when they are placed in vivo into a wound for therapy. These environments are hypoxic, acidic, and have an upregulation of inflammatory mediators creating a region that is hostile towards cellular survival. Within this environment, the majority of progenitor cells undergo apoptosis prior to participating in lineage differentiation and cellular integration. In order to maximize the clinical utility of stem cells, strategies must be employed to increase the cell's ability to survive in vivo through manipulation of both the stem cell and the surrounding environment. This review focuses on current advances and techniques being used to increase in vivo stem cell survival for the purpose of tissue regeneration.

    View details for DOI 10.1016/j.biotechadv.2012.11.003

    View details for Web of Science ID 000322058900019

    View details for PubMedID 23153460

  • CD90 (Thy-1)-Positive Selection Enhances Osteogenic Capacity of Human Adipose-Derived Stromal Cells TISSUE ENGINEERING PART A Chung, M. T., Liu, C., Hyun, J. S., Lo, D. D., Montoro, D. T., Hasegawa, M., Li, S., Sorkin, M., Rennert, R., Keeney, M., Yang, F., Quarto, N., Longaker, M. T., Wan, D. C. 2013; 19 (7-8): 989-997

    Abstract

    Stem cell-based bone tissue engineering with adipose-derived stromal cells (ASCs) has shown great promise for revolutionizing treatment of large bone deficits. However, there is still a lack of consensus on cell surface markers identifying osteoprogenitors. Fluorescence-activated cell sorting has identified a subpopulation of CD105(low) cells with enhanced osteogenic differentiation. The purpose of the present study was to compare the ability of CD90 (Thy-1) to identify osteoprogenitors relative to CD(105).Unsorted cells, CD90(+), CD90(-), CD105(high), and CD105(low) cells were treated with an osteogenic differentiation medium. For evaluation of in vitro osteogenesis, alkaline phosphatase (ALP) staining and alizarin red staining were performed at 7 days and 14 days, respectively. RNA was harvested after 7 and 14 days of differentiation, and osteogenic gene expression was examined by quantitative real-time polymerase chain reaction. For evaluation of in vivo osteogenesis, critical-sized (4-mm) calvarial defects in nude mice were treated with the hydroxyapatite-poly(lactic-co-glycolic acid) scaffold seeded with the above-mentioned subpopulations. Healing was followed using micro-CT scans for 8 weeks. Calvaria were harvested at 8 weeks postoperatively, and sections were stained with Movat's Pentachrome.Transcriptional analysis revealed that the CD90(+) subpopulation was enriched for a more osteogenic subtype relative to the CD105(low) subpopulation. Staining at day 7 for ALP was greatest in the CD90(+) cells, followed by the CD105(low) cells. Staining at day 14 for alizarin red demonstrated the greatest amount of mineralized extracellular matrix in the CD90(+) cells, again followed by the CD105(low) cells. Quantification of in vivo healing at 2, 4, 6, and 8weeks postoperatively demonstrated increased bone formation in defects treated with CD90(+) ASCs relative to all other groups. On Movat's Pentachrome-stained sections, defects treated with CD90(+) cells showed the most robust bony regeneration. Defects treated with CD90(-) cells, CD105(high) cells, and CD105(low) cells demonstrated some bone formation, but to a lesser degree when compared with the CD90(+) group.While CD105(low) cells have previously been shown to possess an enhanced osteogenic potential, we found that CD90(+) cells are more capable of forming bone both in vitro and in vivo. These data therefore suggest that CD90 may be a more effective marker than CD105 to isolate a highly osteogenic subpopulation for bone tissue engineering.

    View details for DOI 10.1089/ten.tea.2012.0370

    View details for PubMedID 23216074

  • Micro-Computed Tomography Evaluation of Human Fat Grafts in Nude Mice TISSUE ENGINEERING PART C-METHODS Chung, M. T., Hyun, J. S., Lo, D. D., Montoro, D. T., Hasegawa, M., Levi, B., Januszyk, M., Longaker, M. T., Wan, D. C. 2013; 19 (3): 227-232

    Abstract

    Although autologous fat grafting has revolutionized the field of soft tissue reconstruction and augmentation, long-term maintenance of fat grafts is unpredictable. Recent studies have reported survival rates of fat grafts to vary anywhere between 10% and 80% over time. The present study evaluated the long-term viability of human fat grafts in a murine model using a novel imaging technique allowing for in vivo volumetric analysis.Human fat grafts were prepared from lipoaspirate samples using the Coleman technique. Fat was injected subcutaneously into the scalp of 10 adult Crl:NU-Foxn1(nu) CD-1 male mice. Micro-computed tomography (CT) was performed immediately following injection and then weekly thereafter. Fat volume was rendered by reconstructing a three-dimensional (3D) surface through cubic-spline interpolation. Specimens were also harvested at various time points and sections were prepared and stained with hematoxylin and eosin (H&E), for macrophages using CD68 and for the cannabinoid receptor 1 (CB1). Finally, samples were explanted at 8- and 12-week time points to validate calculated micro-CT volumes.Weekly CT scanning demonstrated progressive volume loss over the time course. However, volumetric analysis at the 8- and 12-week time points stabilized, showing an average of 62.2% and 60.9% survival, respectively. Gross analysis showed the fat graft to be healthy and vascularized. H&E analysis and staining for CD68 showed minimal inflammatory reaction with viable adipocytes. Immunohistochemical staining with anti-human CB1 antibodies confirmed human origin of the adipocytes.Studies assessing the fate of autologous fat grafts in animals have focused on nonimaging modalities, including histological and biochemical analyses, which require euthanasia of the animals. In this study, we have demonstrated the ability to employ micro-CT for 3D reconstruction and volumetric analysis of human fat grafts in a mouse model. Importantly, this model provides a platform for subsequent study of fat manipulation and soft tissue engineering.

    View details for DOI 10.1089/ten.tec.2012.0371

    View details for Web of Science ID 000314179900006

    View details for PubMedID 22916732

    View details for PubMedCentralID PMC3557441

  • The Seed and the Soil Optimizing Stem Cells and Their Environment for Tissue Regeneration ANNALS OF PLASTIC SURGERY Hyun, J. S., Montoro, D. T., Lo, D. D., Flynn, R. A., Wong, V., Chung, M. T., Longaker, M. T., Wan, D. C. 2013; 70 (2): 235-239

    Abstract

    The potential for stem cells to serve as cellular building blocks for reconstruction of complex defects has prompted significant enthusiasm in the field of regenerative medicine. Clinical application, however, is still limited, as implantation of cells into hostile wound environments may greatly hinder their tissue forming capacity. To circumvent this obstacle, novel approaches have been developed to manipulate both the stem cell itself and its surrounding environmental niche. By understanding this paradigm of seed and soil optimization, innovative strategies may thus be developed to harness the true promise of stem cells for tissue regeneration.

    View details for DOI 10.1097/SAP.0b013e31826a18fb

    View details for Web of Science ID 000313964300024

    View details for PubMedID 23295233

  • Adipose-derived Stromal Cells Overexpressing Vascular Endothelial Growth Factor Accelerate Mouse Excisional Wound Healing MOLECULAR THERAPY Nauta, A., Seidel, C., Deveza, L., Montoro, D., Grova, M., Ko, S. H., Hyun, J., Gurtner, G. C., Longaker, M. T., Yang, F. 2013; 21 (2): 445-455

    Abstract

    Angiogenesis is essential to wound repair, and vascular endothelial growth factor (VEGF) is a potent factor to stimulate angiogenesis. Here, we examine the potential of VEGF-overexpressing adipose-derived stromal cells (ASCs) for accelerating wound healing using nonviral, biodegradable polymeric vectors. Mouse ASCs were transfected with DNA plasmid encoding VEGF or green fluorescent protein (GFP) using biodegradable poly (β-amino) esters (PBAE). Cells transfected using Lipofectamine 2000, a commercially available transfection reagent, were included as controls. ASCs transfected using PBAEs showed enhanced transfection efficiency and 12-15-fold higher VEGF production compared with cells transfected using Lipofectamine 2000 (*P < 0.05). When transplanted into a mouse wild-type excisional wound model, VEGF-overexpressing ASCs led to significantly accelerated wound healing, with full wound closure observed at 8 days compared to 10-12 days in groups treated with ASCs alone or saline control (*P < 0.05). Histology and polarized microscopy showed increased collagen deposition and more mature collagen fibers in the dermis of wound beds treated using PBAE/VEGF-modified ASCs than ASCs alone. Our results demonstrate the efficacy of using nonviral-engineered ASCs to accelerate wound healing, which may provide an alternative therapy for treating many diseases in which wound healing is impaired.

    View details for DOI 10.1038/mt.2012.234

    View details for Web of Science ID 000314434600021

    View details for PubMedID 23164936

    View details for PubMedCentralID PMC3594010

  • STEM CELL-BASED BIOENGINEERING OF CRANIOFACIAL BONE STEM CELLS IN CRANIOFACIAL DEVELOPMENT AND REGENERATION Lo, D. D., Montoro, D. T., Grova, M., Hyun, J. S., Chung, M. T., Wan, D. C., Longaker, M. T., Huang, G. T., Thesleff 2013: 379–94
  • In vivo directed differentiation of pluripotent stem cells for skeletal regeneration PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Levi, B., Hyun, J. S., Montoro, D. T., Lo, D. D., Chan, C. K., Hu, S., Sun, N., Lee, M., Grova, M., Connolly, A. J., Wu, J. C., Gurtner, G. C., Weissman, I. L., Wan, D. C., Longaker, M. T. 2012; 109 (50): 20379-20384

    Abstract

    Pluripotent cells represent a powerful tool for tissue regeneration, but their clinical utility is limited by their propensity to form teratomas. Little is known about their interaction with the surrounding niche following implantation and how this may be applied to promote survival and functional engraftment. In this study, we evaluated the ability of an osteogenic microniche consisting of a hydroxyapatite-coated, bone morphogenetic protein-2-releasing poly-L-lactic acid scaffold placed within the context of a macroenvironmental skeletal defect to guide in vivo differentiation of both embryonic and induced pluripotent stem cells. In this setting, we found de novo bone formation and participation by implanted cells in skeletal regeneration without the formation of a teratoma. This finding suggests that local cues from both the implanted scaffold/cell micro- and surrounding macroniche may act in concert to promote cellular survival and the in vivo acquisition of a terminal cell fate, thereby allowing for functional engraftment of pluripotent cells into regenerating tissue.

    View details for DOI 10.1073/pnas.1218052109

    View details for PubMedID 23169671

  • Femtosecond plasma mediated laser ablation has advantages over mechanical osteotomy of cranial bone LASERS IN SURGERY AND MEDICINE Lo, D. D., Mackanos, M. A., Chung, M. T., Hyun, J. S., Montoro, D. T., Grova, M., Liu, C., Wang, J., Palanker, D., Connolly, A. J., Longaker, M. T., Contag, C. H., Wan, D. C. 2012; 44 (10): 805-814

    Abstract

    Although mechanical osteotomies are frequently made on the craniofacial skeleton, collateral thermal, and mechanical trauma to adjacent bone tissue causes cell death and may delay healing. The present study evaluated the use of plasma-mediated laser ablation using a femtosecond laser to circumvent thermal damage and improve bone regeneration.Critical-size circular calvarial defects were created with a trephine drill bit or with a Ti:Sapphire femtosecond pulsed laser. Healing was followed using micro-CT scans for 8 weeks. Calvaria were also harvested at various time points for histological analysis. Finally, scanning electron microscopy was used to analyze the microstructure of bone tissue treated with the Ti:Sapphire laser, and compared to that treated with the trephine bur.Laser-created defects healed significantly faster than those created mechanically at 2, 4, and 6 weeks post-surgery. However, at 8 weeks post-surgery, there was no significant difference. In the drill osteotomy treatment group, empty osteocyte lacunae were seen to extend 699 ± 27 µm away from the edge of the defect. In marked contrast, empty osteocyte lacunae were seen to extend only 182 ± 22 µm away from the edge of the laser-created craters. Significantly less ossification and formation of irregular woven bone was noted on histological analysis for drill defects.We demonstrate accelerated bone healing after femtosecond laser ablation in a calvarial defect model compared to traditional mechanical drilling techniques. Improved rates of early regeneration make plasma-mediated ablation of the craniofacial skeleton advantageous for applications to osteotomy.

    View details for DOI 10.1002/lsm.22098

    View details for Web of Science ID 000312941600004

    View details for PubMedID 23184427

  • Pierre Robin sequence and Treacher Collins hypoplastic mandible comparison using three-dimensional morphometric analysis. journal of craniofacial surgery Chung, M. T., Levi, B., Hyun, J. S., Lo, D. D., Montoro, D. T., Lisiecki, J., Bradley, J. P., Buchman, S. R., Longaker, M. T., Wan, D. C. 2012; 23 (7): 1959-1963

    Abstract

    Pierre Robin sequence and Treacher Collins syndrome are both associated with mandibular hypoplasia. It has been hypothesized, however, that the mandible may be differentially affected. The purpose of this study was to therefore compare mandibular morphology in children with Pierre Robin sequence with children with Treacher Collins syndrome using three-dimensional analysis of computed tomographic scans. A retrospective analysis was performed identifying children with Pierre Robin sequence and Treacher Collins syndrome undergoing computed tomography. Three-dimensional reconstruction was performed, and ramus height, mandibular body length, and gonial angle were measured. These were then compared with those in control children with normal mandibles and with the clinical norms corrected for age and sex based on previously published measurements. Mandibular body length was found to be significantly shorter for children with Pierre Robin sequence, whereas ramus height was significantly shorter for children with Treacher Collins syndrome. This resulted in distinctly different ramus height-mandibular body length ratios. In addition, the gonial angle was more obtuse in both the Pierre Robin sequence and Treacher Collins syndrome groups compared with the controls. Three-dimensional mandibular morphometric analysis in patients with Pierre Robin sequence and Treacher Collins syndrome thus revealed distinctly different patterns of mandibular hypoplasia relative to normal controls. These findings underscore distinct considerations that must be made in surgical planning for reconstruction.

    View details for DOI 10.1097/SCS.0b013e318258bcf1

    View details for PubMedID 23154353

    View details for PubMedCentralID PMC3544559

  • Models of cranial suture biology. journal of craniofacial surgery Grova, M., Lo, D. D., Montoro, D., Hyun, J. S., Chung, M. T., Wan, D. C., Longaker, M. T. 2012; 23 (7): 1954-1958

    Abstract

    Craniosynostosis is a common congenital defect caused by premature fusion of cranial sutures. The severe morphologic abnormalities and cognitive deficits resulting from craniosynostosis and the potential morbidity of surgical correction espouse the need for a deeper understanding of the complex etiology for this condition. Work in animal models for the past 20 years has been pivotal in advancing our understanding of normal suture biology and elucidating pathologic disease mechanisms. This article provides an overview of milestone studies in suture development, embryonic origins, and signaling mechanisms from an array of animal models including transgenic mice, rats, rabbits, fetal sheep, zebrafish, and frogs. This work contributes to an ongoing effort toward continued development of novel treatment strategies.

    View details for DOI 10.1097/SCS.0b013e318258ba53

    View details for PubMedID 23154351

  • Models of Cranial Suture Biology JOURNAL OF CRANIOFACIAL SURGERY Grova, M., Lo, D. D., Montoro, D., Hyun, J. S., Chung, M. T., Wan, D. C., Longaker, M. T. 2012; 23: 1954-1958

    Abstract

    Craniosynostosis is a common congenital defect caused by premature fusion of cranial sutures. The severe morphologic abnormalities and cognitive deficits resulting from craniosynostosis and the potential morbidity of surgical correction espouse the need for a deeper understanding of the complex etiology for this condition. Work in animal models for the past 20 years has been pivotal in advancing our understanding of normal suture biology and elucidating pathologic disease mechanisms. This article provides an overview of milestone studies in suture development, embryonic origins, and signaling mechanisms from an array of animal models including transgenic mice, rats, rabbits, fetal sheep, zebrafish, and frogs. This work contributes to an ongoing effort toward continued development of novel treatment strategies.

    View details for DOI 10.1097/SCS.0b013e318258ba53

    View details for Web of Science ID 000209481500006

  • Pierre Robin Sequence and Treacher Collins Hypoplastic Mandible Comparison Using Three-Dimensional Morphometric Analysis JOURNAL OF CRANIOFACIAL SURGERY Chung, M. T., Levi, B., Hyun, J. S., Lo, D. D., Montoro, D. T., Lisiecki, J., Bradley, J. P., Buchman, S. R., Longaker, M. T., Wan, D. C. 2012; 23: 1959-1963

    Abstract

    Pierre Robin sequence and Treacher Collins syndrome are both associated with mandibular hypoplasia. It has been hypothesized, however, that the mandible may be differentially affected. The purpose of this study was to therefore compare mandibular morphology in children with Pierre Robin sequence with children with Treacher Collins syndrome using three-dimensional analysis of computed tomographic scans. A retrospective analysis was performed identifying children with Pierre Robin sequence and Treacher Collins syndrome undergoing computed tomography. Three-dimensional reconstruction was performed, and ramus height, mandibular body length, and gonial angle were measured. These were then compared with those in control children with normal mandibles and with the clinical norms corrected for age and sex based on previously published measurements. Mandibular body length was found to be significantly shorter for children with Pierre Robin sequence, whereas ramus height was significantly shorter for children with Treacher Collins syndrome. This resulted in distinctly different ramus height-mandibular body length ratios. In addition, the gonial angle was more obtuse in both the Pierre Robin sequence and Treacher Collins syndrome groups compared with the controls. Three-dimensional mandibular morphometric analysis in patients with Pierre Robin sequence and Treacher Collins syndrome thus revealed distinctly different patterns of mandibular hypoplasia relative to normal controls. These findings underscore distinct considerations that must be made in surgical planning for reconstruction.

    View details for DOI 10.1097/SCS.0b013e318258bcf1

    View details for Web of Science ID 000209481500007

    View details for PubMedCentralID PMC3544559

  • Repair of a Critical-sized Calvarial Defect Model Using Adipose-derived Stromal Cells Harvested from Lipoaspirate JOVE-JOURNAL OF VISUALIZED EXPERIMENTS Lo, D. D., Hyun, J. S., Chung, M. T., Montoro, D. T., Zimmermann, A., Grova, M. M., Lee, M., Wan, D. C., Longaker, M. T. 2012

    View details for DOI 10.3791/4221

    View details for Web of Science ID 000209225700022

  • Rethinking the Blastema PLASTIC AND RECONSTRUCTIVE SURGERY Hyun, J. S., Chung, M. T., Wong, V. W., Montoro, D., Longaker, M. T., Wan, D. C. 2012; 129 (5): 1097-1103

    Abstract

    The phenomenon of tissue regeneration has been well documented across many species. Although some possess the capacity to completely restore an entire amputated limb, others are limited to just the distal digit tip. Initiation of limb regeneration has been described to start with the formation of a blastema, the composition of which has long been thought to consist of undifferentiated pluripotent cells derived through the process of dedifferentiation. Competing theories have been proposed, however, including cellular contributions through transdifferentiation and tissue-specific stem cells. Recent studies have now begun to shed light on this controversy, demonstrating tissue resident stem cells to be an evolutionarily conserved measure for limb regeneration.

    View details for DOI 10.1097/PRS.0b013e31824a2c49

    View details for Web of Science ID 000303497300059

    View details for PubMedID 22544093

  • Stem Cells: Update and Impact on Craniofacial Surgery JOURNAL OF CRANIOFACIAL SURGERY Levi, B., Glotzbach, J. P., Wong, V. W., Nelson, E. R., Hyun, J., Wan, D. C., Gurtner, G. C., Longaker, M. T. 2012; 23 (1): 319-322

    View details for DOI 10.1097/SCS.0b013e318241dbaf

    View details for Web of Science ID 000300234900099

    View details for PubMedID 22337434

    View details for PubMedCentralID PMC3282019

  • Enhancement of Human Adipose-Derived Stromal Cell Angiogenesis through Knockdown of a BMP-2 Inhibitor PLASTIC AND RECONSTRUCTIVE SURGERY Levi, B., Nelson, E. R., Hyun, J. S., Glotzbach, J. P., Li, S., Nauta, A., Montoro, D. T., Lee, M., Commons, G. C., Hu, S., Wu, J. C., Gurtner, G. C., Longaker, M. T. 2012; 129 (1): 53-66

    Abstract

    Previous studies have demonstrated the role of noggin, a bone morphogenetic protein-2 inhibitor, in vascular development and angiogenesis. The authors hypothesized that noggin suppression in human adipose-derived stromal cells would enhance vascular endothelial growth factor secretion and angiogenesis in vitro and in vivo to a greater extent than bone morphogenetic protein-2 alone.Human adipose-derived stromal cells were isolated from human lipoaspirate (n = 6) noggin was knocked down using lentiviral techniques. Knockdown was confirmed and angiogenesis was assessed by tubule formation and quantitative real-time polymerase chain reaction. Cells were seeded onto scaffolds and implanted into a 4-mm critical size calvarial defect. In vivo angiogenic signaling was assessed by immunofluorescence and immunohistochemistry.Human adipose-derived stromal cells with noggin suppression secreted significantly higher amounts of angiogenic proteins, expressed higher levels of angiogenic genes, and formed more tubules in vitro. In vivo, calvarial defects seeded with noggin shRNA human adipose-derived stromal cells exhibited a significantly higher number of vessels in the defect site than controls by immunohistochemistry (p < 0.05). In addition, bone morphogenetic protein-2-releasing scaffolds significantly enhanced vascular signaling in the defect site.Human adipose-derived stromal cells demonstrate significant increases in angiogenesis in vitro and in vivo with both noggin suppression and BMP-2 supplementation. By creating a cell with noggin suppressed and by using a scaffold with increased bone morphogenetic protein-2 signaling, a more angiogenic niche can be created.

    View details for DOI 10.1097/PRS.0b013e3182361ff5

    View details for PubMedID 21915082

  • Cranial Suture Biology: From Pathways to Patient Care JOURNAL OF CRANIOFACIAL SURGERY Levi, B., Wan, D. C., Wong, V. W., Nelson, E., Hyun, J., Longaker, M. T. 2012; 23 (1): 13-19

    Abstract

    Craniosynostosis describes the premature pathologic partial or complete fusion of 1 or more of the cranial sutures. Over the past few decades, research on craniosynostosis has progressed from gross description of deformities to an understanding of some of the molecular etiologies behind premature suture fusion. Studies on patients with syndromic craniosynostosis have resulted in the identification of several genes, molecular events, and deformational forces involved in abnormal growth and development of the cranial vault. Conservation of craniofacial development and sequence homology between humans and other species have also led to insightful discoveries in cranial suture development. In this review, we discuss the development of the cranial vault and explain the basic science behind craniosynostosis in humans as well as in animal models and how these studies may lead to future advances in craniosynostosis treatments.

    View details for DOI 10.1097/SCS.0b013e318240c6c0

    View details for Web of Science ID 000300234900033

    View details for PubMedID 22337368

  • Nonintegrating Knockdown and Customized Scaffold Design Enhances Human Adipose-Derived Stem Cells in Skeletal Repair STEM CELLS Levi, B., Hyun, J. S., Nelson, E. R., Li, S., Montoro, D. T., Wan, D. C., Jia, F. J., Glotzbach, J. C., James, A. W., Lee, M., Huang, M., Quarto, N., Gurtner, G. C., Wu, J. C., Longaker, M. T. 2011; 29 (12): 2018-2029

    Abstract

    An urgent need exists in clinical medicine for suitable alternatives to available techniques for bone tissue repair. Human adipose-derived stem cells (hASCs) represent a readily available, autogenous cell source with well-documented in vivo osteogenic potential. In this article, we manipulated Noggin expression levels in hASCs using lentiviral and nonintegrating minicircle short hairpin ribonucleic acid (shRNA) methodologies in vitro and in vivo to enhance hASC osteogenesis. Human ASCs with Noggin knockdown showed significantly increased bone morphogenetic protein (BMP) signaling and osteogenic differentiation both in vitro and in vivo, and when placed onto a BMP-releasing scaffold embedded with lentiviral Noggin shRNA particles, hASCs more rapidly healed mouse calvarial defects. This study therefore suggests that genetic targeting of hASCs combined with custom scaffold design can optimize hASCs for skeletal regenerative medicine.

    View details for DOI 10.1002/stem.757

    View details for PubMedID 21997852

  • CD105 Protein Depletion Enhances Human Adipose-derived Stromal Cell Osteogenesis through Reduction of Transforming Growth Factor beta 1 (TGF-beta 1) Signaling JOURNAL OF BIOLOGICAL CHEMISTRY Levi, B., Wan, D. C., Glotzbach, J. P., Hyun, J., Januszyk, M., Montoro, D., Sorkin, M., James, A. W., Nelson, E. R., Li, S., Quarto, N., Lee, M., Gurtner, G. C., Longaker, M. T. 2011; 286 (45): 39497-39509

    Abstract

    Clinically available sources of bone for repair and reconstruction are limited by the accessibility of autologous grafts, infectious risks of cadaveric materials, and durability of synthetic substitutes. Cell-based approaches for skeletal regeneration can potentially fill this need, and adipose tissue represents a promising source for development of such therapies. Here, we enriched for an osteogenic subpopulation of cells derived from human subcutaneous adipose tissue utilizing microfluidic-based single cell transcriptional analysis and fluorescence-activated cell sorting (FACS). Statistical analysis of single cell transcriptional profiles demonstrated that low expression of endoglin (CD105) correlated with a subgroup of adipose-derived cells with increased osteogenic gene expression. FACS-sorted CD105(low) cells demonstrated significantly enhanced in vitro osteogenic differentiation and in vivo bone regeneration when compared with either CD105(high) or unsorted cells. Evaluation of the endoglin pathway suggested that enhanced osteogenesis among CD105(low) adipose-derived cells is likely due to identification of a subpopulation with lower TGF-β1/Smad2 signaling. These findings thus highlight a potential avenue to promote osteogenesis in adipose-derived mesenchymal cells for skeletal regeneration.

    View details for DOI 10.1074/jbc.M111.256529

    View details for PubMedID 21949130

  • Dura Mater Stimulates Human Adipose-Derived Stromal Cells to Undergo Bone Formation in Mouse Calvarial Defects STEM CELLS Levi, B., Nelson, E. R., Li, S., James, A. W., Hyun, J. S., Montoro, D. T., Lee, M., Glotzbach, J. P., Commons, G. W., Longaker, M. T. 2011; 29 (8): 1241-1255

    Abstract

    Human adipose-derived stromal cells (hASCs) have a proven capacity to aid in osseous repair of calvarial defects. However, the bone defect microenvironment necessary for osseous healing is not fully understood. In this study, we postulated that the cell-cell interaction between engrafted ASCs and host dura mater (DM) cells is critical for the healing of calvarial defects. hASCs were engrafted into critical sized calvarial mouse defects. The DM-hASC interaction was manipulated surgically by DM removal or by insertion of a semipermeable or nonpermeable membrane between DM and hASCs. Radiographic, histologic, and gene expression analyses were performed. Next, the hASC-DM interaction is assessed by conditioned media (CM) and coculture assays. Finally, bone morphogenetic protein (BMP) signaling from DM was investigated in vivo using novel BMP-2 and anti-BMP-2/4 slow releasing scaffolds. With intact DM, osseous healing occurs both from host DM and engrafted hASCs. Interference with the DM-hASC interaction dramatically reduced calvarial healing with abrogated BMP-2-Smad-1/5 signaling. Using CM and coculture assays, mouse DM cells stimulated hASC osteogenesis via BMP signaling. Through in vivo manipulation of the BMP-2 pathway, we found that BMP-2 plays an important role in DM stimulation of hASC osteogenesis in the context of calvarial bone healing. BMP-2 supplementation to a defect with disrupted DM allowed for bone formation in a nonhealing defect. DM is an osteogenic cell type that both participates in and stimulates osseous healing in a hASC-engrafted calvarial defect. Furthermore, DM-derived BMP-2 paracrine stimulation appears to play a key role for hASC mediated repair.

    View details for DOI 10.1002/stem.670

    View details for Web of Science ID 000293133900009

    View details for PubMedID 21656608

    View details for PubMedCentralID PMC4353733

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