Honors & Awards

  • Introduction to Academic Radiology for Scientists (ITARSc), Radiological Society of North America (RSNA) (2017)
  • Travel award, World Molecular Imaging Conference (2017)
  • Travel award, Radiological Society of North America (RSNA) (2016)
  • Trainee Research Prize, Radiological Society of North America (RSNA) (2014)
  • Travel award, World Molecular Imaging Conference (WMIC) (2014)
  • NAIRS research award, North American Iranian Radiological Society (2014)
  • Travel award, CMC-Stanford Joint Symposium on Molecular Imaging (2014)
  • Travel award, World Molecular Imaging Conference (WMIC) (2013)
  • Trainee Research Prize, Radiological Society of North America (RSNA) (2012)
  • Travel award, World Molecular Imaging Conference (WMIC) (2012)
  • Travel award, International Cartilage Repair Society (ICRS) (2010)
  • Scholarship award, National University of Singapore School of Medicine (SoM) (2009 and 2010)
  • Travel award, International Cartilage Repair Society (ICRS) (2009)
  • Scholarship award, Agency for Science, Technology and Research (A*STAR) (2007 and 2008)

Education & Certifications

  • Research Scientist, Stanford University, Radiology / Molecular Imaging
  • Research Associate, Stanford University, Radiology / Molecular Imaging (2016)
  • Postdoctoral Fellowship, Stanford University, Radiology / Molecular Imaging (2016)
  • PhD, National University of Singapore, Tissue Engineering (2013)
  • Medical Internship, Isfahan University of Medical Sciences, (transitional internship) (2005)
  • MD, Isfahan University of Medical Sciences, Medicine (2005)


All Publications

  • Tracking Cell Transplants in Femoral Osteonecrosis with Magnetic Resonance Imaging: A Proof of Concept Study in Patients. Clinical cancer research : an official journal of the American Association for Cancer Research Theruvath, A. J., Nejadnik, H., Muehe, A. M., Gassert, F., Lacayo, N. J., Goodman, S. B., Daldrup-Link, H. E. 2018


    PURPOSE: Osteonecrosis (ON) is a devastating complication of high dose corticosteroid therapy in cancer patients. Core decompression for prevention of bone collapse has been recently combined with the delivery of autologous concentrated bone marrow aspirates. The purpose of our study was to develop an imaging test for the detection of transplanted bone marrow cells in ON lesions.EXPERIMENTAL DESIGN: In a prospective proof-of-concept clinical trial (NCT02893293), we performed serial MR imaging studies of nine hip joints of seven ON patients before and after core decompression. 24-48hours prior to the surgery, we injected ferumoxytol nanoparticles intravenously to label cells in normal bone marrow with iron oxides. During the surgery, iron labeled bone marrow cells were aspirated from the iliac crest, concentrated and then injected into the decompression track. Following surgery, patients received follow-up MRI up to 6 months after bone marrow cell transplantation.RESULTS: Iron labeled cells could be detected in the access canal by a dark (negative) signal on T2*-weighted MR images. T2* relaxation times of iron labeled cell transplants were significantly lower compared to unlabeled cell transplants of control patients who were not injected with ferumoxytol (P = 0.02). Clinical outcomes of patients who received ferumoxytol-labeled or unlabeled cell transplants were not significantly different (P = 1), suggesting that the added ferumoxytol administration did not negatively affect bone repair.CONCLUSIONS: This immediately clinically applicable imaging test could become a powerful new tool to monitor the effect of therapeutic cells on bone repair outcomes after corticosteroid-induced osteonecrosis.

    View details for DOI 10.1158/1078-0432.CCR-18-1687

    View details for PubMedID 30224340

  • Ferumoxytol Can Be Used for Quantitative Magnetic Particle Imaging of Transplanted Stem Cells. Molecular imaging and biology : MIB : the official publication of the Academy of Molecular Imaging Nejadnik, H., Pandit, P., Lenkov, O., Lahiji, A. P., Yerneni, K., Daldrup-Link, H. E. 2018


    PURPOSE: To evaluate, if clinically translatable ferumoxytol nanoparticles can be used for in vivo detection and quantification of stem cell transplants with magnetic particle imaging (MPI).PROCEDURES: Mesenchymal stem cells (MSCs) were labeled with ferumoxytol or ferucarbotran and underwent MPI, magnetic resonance imaging (MRI), Prussian blue staining, and inductively coupled plasma (ICP) spectrometry. Unlabeled, ferumoxytol, and ferucarbotran-labeled MSCs were implanted in calvarial defects of eight mice and underwent MPI, MRI, and histopathology. The iron concentration calculated according to the MPI signal intensity and T2 relaxation times of the three different groups were compared using an analysis of variance (ANOVA) with Bonferroni correction, and a p<0.05.RESULTS: Compared to unlabeled controls, ferumoxytol- and ferucarbotran-labeled MSC showed significantly increased iron content, MPI signal and MRI signal. The ferumoxytol MPI signal was approximately 4* weaker compared to ferucarbotran at equimolar concentrations (p=0.0003) and approximately 1.5* weaker for labeled cells when using optimized labeling protocols (p=0.002). In vivo, the MPI signal of ferumoxytol-labeled MSC decreased significantly between day 1 and day 14 (p=0.0124). This was confirmed by histopathology where we observed a decrease in Prussian blue stain of MSCs at the transplant site. The MRI signal of the same transplants did not change significantly during this observation period (p=0.93).CONCLUSION: Ferumoxytol nanoparticles can be used for in vivo detection of stem cell transplants with MPI and provide quantitative information not attainable with MRI.

    View details for DOI 10.1007/s11307-018-1276-x

    View details for PubMedID 30194566

  • Association of Tumor [18F]FDG Activity and Diffusion Restriction with Clinical Outcomes of Rhabdomyosarcomas. Molecular imaging and biology : MIB : the official publication of the Academy of Molecular Imaging Pourmehdi Lahiji, A., Jackson, T., Nejadnik, H., von Eyben, R., Rubin, D., Spunt, S. L., Quon, A., Daldrup-Link, H. 2018


    PURPOSE: To evaluate whether the extent of restricted diffusion and 2-deoxy-2-[18F] fluoro-D-glucose ([18F]FDG) uptake of pediatric rhabdomyosarcomas (RMS) on positron emission tomography (PET)/magnetic resonance (MR) images provides prognostic information.PROCEDURE: In a retrospective, IRB-approved study, we evaluated [18F]FDG PET/CT and diffusion-weighted (DW) MR imaging studies of 21 children and adolescents (age 1-20years) with RMS of the head and neck. [18F]FDG PET and DW MR scans at the time of the initial tumor diagnosis were fused using MIM software. Quantitative measures of the tumor mass with restricted diffusion, [18F]FDG hypermetabolism, or both were dichotomized at the median and tested for significance using Gray's test. Data were analyzed using a survival analysis and competing risk model with death as the competing risk.RESULTS: [18F]FDG PET/MR images demonstrated a mismatch between tumor areas with increased [18F]FDG uptake and restricted diffusion. The DWI, PET, and DWI+PET tumor volumes were dichotomized at their median values, 23.7, 16.4, and 9.5cm3, respectively, and were used to estimate survival. DWI, PET, and DWI+PET overlap tumor volumes above the cutoff values were associated with tumor recurrence, regardless of post therapy COG stage (p=0.007, p=0.04, and p=0.07, respectively).CONCLUSION: The extent of restricted diffusion within RMS and overlap of hypermetabolism plus restricted diffusion predict unfavorable clinical outcomes.

    View details for DOI 10.1007/s11307-018-1272-1

    View details for PubMedID 30187233

  • Tumor Formation of Adult Stem Cell Transplants in Rodent Arthritic Joints. Molecular imaging and biology : MIB : the official publication of the Academy of Molecular Imaging Chapelin, F., Khurana, A., Moneeb, M., Gray Hazard, F. K., Chan, C. F., Nejadnik, H., Gratzinger, D., Messing, S., Erdmann, J., Gaur, A., Daldrup-Link, H. E. 2018


    While imaging matrix-associated stem cell transplants aimed for cartilage repair in a rodent arthritis model, we noticed that some transplants formed locally destructive tumors. The purpose of this study was to determine the cause for this tumor formation in order to avoid this complication for future transplants.Adipose-derived stem cells (ADSC) isolated from subcutaneous adipose tissue were implanted into 24 osteochondral defects of the distal femur in ten athymic rats and two immunocompetent control rats. All transplants underwent serial magnetic resonance imaging (MRI) up to 6 weeks post-transplantation to monitor joint defect repair. Nine transplants showed an increasing size over time that caused local bone destruction (group 1), while 11 transplants in athymic rats (group 2) and 4 transplants in immunocompetent rats did not. We compared the ADSC implant size and growth rate on MR images, macroscopic features, histopathologic features, surface markers, and karyotypes of these presumed neoplastic transplants with non-neoplastic ADSC transplants.Implants in group 1 showed a significantly increased two-dimensional area at week 2 (p = 0.0092), 4 (p = 0.003), and 6 (p = 0.0205) compared to week 0, as determined by MRI. Histopathological correlations confirmed neoplastic features in group 1 with significantly increased size, cellularity, mitoses, and cytological atypia compared to group 2. Six transplants in group 1 were identified as malignant chondrosarcomas and three transplants as fibromyxoid sarcomas. Transplants in group 2 and immunocompetent controls exhibited normal cartilage features. Both groups showed a normal ADSC phenotype; however, neoplastic ADSC demonstrated a mixed population of diploid and tetraploid cells without genetic imbalance.ADSC transplants can form tumors in vivo. Preventive actions to avoid in vivo tumor formations may include karyotyping of culture-expanded ADSC before transplantation. In addition, serial imaging of ADSC transplants in vivo may enable early detection of abnormally proliferating cell transplants.

    View details for DOI 10.1007/s11307-018-1218-7

    View details for PubMedID 29869062

  • Ferumoxytol-based Dual-modality Imaging Probe for Detection of Stem Cell Transplant Rejection. Nanotheranostics Li, K., Chan, C. T., Nejadnik, H., Lenkov, O. D., Wolterman, C., Paulmurugan, R., Yang, H., Gambhir, S. S., Daldrup-Link, H. E. 2018; 2 (4): 306–19


    Purpose: Stem cell transplants are an effective approach to repair large bone defects. However, comprehensive techniques to monitor the fate of transplanted stem cells in vivo are lacking. Such strategies would enable corrective interventions at an early stage and greatly benefit the development of more successful tissue regeneration approaches. In this study, we designed and synthesized a dual-modality imaging probe (Feru-AFC) that can simultaneously localize transplanted stem cells and diagnose immune rejection-induced apoptosis at an early stage in vivo. Methods: We used a customized caspase-3 cleavable peptide-dye conjugate to modify the surface of clinically approved ferumoxytol nanoparticles (NPs) to generate the dual-modality imaging probe with fluorescence "light-up" feature. We labeled both mouse mesenchymal stem cells (mMSCs, matched) and pig mesenchymal stem cells (pMSCs, mismatched) with the probe and transplanted the labeled cells with biocompatible scaffold at the calvarial defects in mice. We then employed intravital microscopy (IVM) and magnetic resonance imaging (MRI) to investigate the localization, engraftment, and viability of matched and mismatched stem cells, followed by histological analyses to evaluate the results obtained from in vivo studies. Results: The Feru-AFC NPs showed good cellular uptake efficiency in the presence of lipofectin without cytotoxicity to mMSCs and pMSCs. The fluorescence of Feru-AFC NPs was turned on inside apoptotic cells due to the cleavage of peptide by activated caspase-3 and subsequent release of fluorescence dye molecules. Upon transplantation at the calvarial defects in mice, the intense fluorescence from the cleaved Feru-AFC NPs in apoptotic pMSCs was observed with a concomitant decrease in the overall cell number from days 1 to 6. In contrast, the Feru-AFC NP-treated mMSCs exhibited minimum fluorescence and the cell number also remained similar. Furthermore, in vivo MRI of the Feru-AFC NP-treated mMSC and pMSCs transplants could clearly indicate the localization of matched and mismatched cells, respectively. Conclusions: We successfully developed a dual-modality imaging probe for evaluation of the localization and viability of transplanted stem cells in mouse calvarial defects. Using ferumoxytol NPs as the platform, our Feru-AFC NPs are superparamagnetic and display a fluorescence "light-up" signature upon exposure to activated caspase-3. The results show that the probe is a promising tool for long-term stem cell tracking through MRI and early diagnosis of immune rejection-induced apoptosis through longitudinal fluorescence imaging.

    View details for DOI 10.7150/ntno.26389

    View details for PubMedID 29977742

    View details for PubMedCentralID PMC6030766

  • Next-generation superparamagnetic iron oxide nanoparticles for cancer theranostics. Drug discovery today Li, K., Nejadnik, H., Daldrup-Link, H. E. 2017


    Superparamagnetic iron oxide (SPIO) nanoparticles have been intensively studied for the development of contrast agents in MRI[SB1] . First-generation SPIO nanoparticles had diagnostic capabilities only, whereas a new generation of SPIO nanoparticle has multifunctional characteristics for combined therapeutic and diagnostic applications. These theranostic nanoparticles hold great potential for image-guided cancer therapies. In particular, polymer-coated theranostic SPIO nanoparticles have enjoyed increasing attention as a result of good biocompatibility, biodegradability and versatile functionality endowed by polymeric matrices. This review provides an overview of recently developed polymer-coated multifunctional SPIO nanoparticles for cancer theranostics and discusses current challenges and future perspectives.

    View details for DOI 10.1016/j.drudis.2017.04.008

    View details for PubMedID 28454771

  • Detection of Stem Cell Transplant Rejection with Ferumoxytol MR Imaging: Correlation of MR Imaging Findings with Those at Intravital Microscopy. Radiology Daldrup-Link, H. E., Chan, C., Lenkov, O., Taghavigarmestani, S., Nazekati, T., Nejadnik, H., Chapelin, F., Khurana, A., Tong, X., Yang, F., Pisani, L., Longaker, M., Gambhir, S. S. 2017: 161139-?


    Purpose To determine whether endogenous labeling of macrophages with clinically applicable nanoparticles enables noninvasive detection of innate immune responses to stem cell transplants with magnetic resonance (MR) imaging. Materials and Methods Work with human stem cells was approved by the institutional review board and the stem cell research oversight committee, and animal experiments were approved by the administrative panel on laboratory animal care. Nine immunocompetent Sprague-Dawley rats received intravenous injection of ferumoxytol, and 18 Jax C57BL/6-Tg (Csf1r-EGFP-NGFR/FKBP1A/TNFRSF6) 2Bck/J mice received rhodamine-conjugated ferumoxytol. Then, 48 hours later, immune-matched or mismatched stem cells were implanted into osteochondral defects of the knee joints of experimental rats and calvarial defects of Jax mice. All animals underwent serial MR imaging and intravital microscopy (IVM) up to 4 weeks after surgery. Macrophages of Jax C57BL/6-Tg (Csf1r-EGFP-NGFR/FKBP1A/TNFRSF6) 2Bck/J mice express enhanced green fluorescent protein (GFP), which enables in vivo correlation of ferumoxytol enhancement at MR imaging with macrophage quantities at IVM. All quantitative data were compared between experimental groups by using a mixed linear model and t tests. Results Immune-mismatched stem cell implants demonstrated stronger ferumoxytol enhancement than did matched stem cell implants. At 4 weeks, T2 values of mismatched implants were significantly lower than those of matched implants in osteochondral defects of female rats (mean, 10.72 msec for human stem cells and 11.55 msec for male rat stem cells vs 15.45 msec for sex-matched rat stem cells; P = .02 and P = .04, respectively) and calvarial defects of recipient mice (mean, 21.7 msec vs 27.1 msec, respectively; P = .0444). This corresponded to increased recruitment of enhanced GFP- and rhodamine-ferumoxytol-positive macrophages into stem cell transplants, as visualized with IVM and histopathologic examination. Conclusion Endogenous labeling of macrophages with ferumoxytol enables noninvasive detection of innate immune responses to stem cell transplants with MR imaging. (©) RSNA, 2017 Online supplemental material is available for this article.

    View details for DOI 10.1148/radiol.2017161139

    View details for PubMedID 28128708

  • The Protein Corona around Nanoparticles Facilitates Stem Cell Labeling for Clinical MR Imaging. Radiology Nejadnik, H., Taghavi-Garmestani, S. M., Madsen, S. J., Li, K., Zanganeh, S., Yang, P., Mahmoudi, M., Daldrup-Link, H. E. 2017: 170130


    Purpose To evaluate if the formation of a protein corona around ferumoxytol nanoparticles can facilitate stem cell labeling for in vivo tracking with magnetic resonance (MR) imaging. Materials and Methods Ferumoxytol was incubated in media containing human serum (group 1), fetal bovine serum (group 2), StemPro medium (group 3), protamine (group 4), and protamine plus heparin (group 5). Formation of a protein corona was characterized by means of dynamic light scattering, ζ potential, and liquid chromatography-mass spectrometry. Iron uptake was evaluated with 3,3'-diaminobenzidine-Prussian blue staining, lysosomal staining, and inductively coupled plasma spectrometry. To evaluate the effect of a protein corona on stem cell labeling, human mesenchymal stem cells (hMSCs) were labeled with the above formulations, implanted into pig knee specimens, and investigated with T2-weighted fast spin-echo and multiecho spin-echo sequences on a 3.0-T MR imaging unit. Data in different groups were compared by using a Kruskal-Wallis test. Results Compared with bare nanoparticles, all experimental groups showed significantly increased negative ζ values (from -37 to less than -10; P = .008). Nanoparticles in groups 1-3 showed an increased size because of the formation of a protein corona. hMSCs labeled with group 1-5 media showed significantly shortened T2 relaxation times compared with unlabeled control cells (P = .0012). hMSCs labeled with group 3 and 5 media had the highest iron uptake after cells labeled with group 1 medium. After implantation into pig knees, hMSCs labeled with group 1 medium showed significantly shorter T2 relaxation times than hMSCs labeled with group 2-5 media (P = .0022). Conclusion The protein corona around ferumoxytol nanoparticles can facilitate stem cell labeling for clinical cell tracking with MR imaging. (©) RSNA, 2017 Online supplemental material is available for this article.

    View details for DOI 10.1148/radiol.2017170130

    View details for PubMedID 29091749

  • Iron oxide nanoparticles inhibit tumour growth by inducing pro-inflammatory macrophage polarization in tumour tissues. Nature nanotechnology Zanganeh, S., Hutter, G., Spitler, R., Lenkov, O., Mahmoudi, M., Shaw, A., Pajarinen, J. S., Nejadnik, H., Goodman, S., Moseley, M., Coussens, L. M., Daldrup-Link, H. E. 2016; 11 (11): 986-994


    Until now, the Food and Drug Administration (FDA)-approved iron supplement ferumoxytol and other iron oxide nanoparticles have been used for treating iron deficiency, as contrast agents for magnetic resonance imaging and as drug carriers. Here, we show an intrinsic therapeutic effect of ferumoxytol on the growth of early mammary cancers, and lung cancer metastases in liver and lungs. In vitro, adenocarcinoma cells co-incubated with ferumoxytol and macrophages showed increased caspase-3 activity. Macrophages exposed to ferumoxytol displayed increased mRNA associated with pro-inflammatory Th1-type responses. In vivo, ferumoxytol significantly inhibited growth of subcutaneous adenocarcinomas in mice. In addition, intravenous ferumoxytol treatment before intravenous tumour cell challenge prevented development of liver metastasis. Fluorescence-activated cell sorting (FACS) and histopathology studies showed that the observed tumour growth inhibition was accompanied by increased presence of pro-inflammatory M1 macrophages in the tumour tissues. Our results suggest that ferumoxytol could be applied 'off label' to protect the liver from metastatic seeds and potentiate macrophage-modulating cancer immunotherapies.

    View details for DOI 10.1038/nnano.2016.168

    View details for PubMedID 27668795

  • Macrophage phagocytosis alters the MRI signal of ferumoxytol-labeled mesenchymal stromal cells in cartilage defects SCIENTIFIC REPORTS Nejadnik, H., Lenkov, O., Gassert, F., Fretwell, D., Lam, I., Daldrup-Link, H. E. 2016; 6


    Human mesenchymal stem cells (hMSCs) are a promising tool for cartilage regeneration in arthritic joints. hMSC labeling with iron oxide nanoparticles enables non-invasive in vivo monitoring of transplanted cells in cartilage defects with MR imaging. Since graft failure leads to macrophage phagocytosis of apoptotic cells, we evaluated in vitro and in vivo whether nanoparticle-labeled hMSCs show distinct MR signal characteristics before and after phagocytosis by macrophages. We found that apoptotic nanoparticle-labeled hMSCs were phagocytosed by macrophages while viable nanoparticle-labeled hMSCs were not. Serial MRI scans of hMSC transplants in arthritic joints of recipient rats showed that the iron signal of apoptotic, nanoparticle-labeled hMSCs engulfed by macrophages disappeared faster compared to viable hMSCs. This corresponded to poor cartilage repair outcomes of the apoptotic hMSC transplants. Therefore, rapid decline of iron MRI signal at the transplant site can indicate cell death and predict incomplete defect repair weeks later. Currently, hMSC graft failure can be only diagnosed by lack of cartilage defect repair several months after cell transplantation. The described imaging signs can diagnose hMSC transplant failure more readily, which could enable timely re-interventions and avoid unnecessary follow up studies of lost transplants.

    View details for DOI 10.1038/srep25897

    View details for Web of Science ID 000375769300001

    View details for PubMedID 27174199

  • Improved Approach for Chondrogenic Differentiation of Human Induced Pluripotent Stem Cells STEM CELL REVIEWS AND REPORTS Nejadnik, H., Diecke, S., Lenkov, O. D., Chapelin, F., Donig, J., Tong, X., Derugin, N., Chan, R. C., Gaur, A., Yang, F., Wu, J. C., Daldrup-Link, H. E. 2015; 11 (2): 242-253


    Human induced pluripotent stem cells (hiPSCs) have demonstrated great potential for hyaline cartilage regeneration. However, current approaches for chondrogenic differentiation of hiPSCs are complicated and inefficient primarily due to intermediate embryoid body formation, which is required to generate endodermal, ectodermal, and mesodermal cell lineages. We report a new, straightforward and highly efficient approach for chondrogenic differentiation of hiPSCs, which avoids embryoid body formation. We differentiated hiPSCs directly into mesenchymal stem /stromal cells (MSC) and chondrocytes. hiPSC-MSC-derived chondrocytes showed significantly increased Col2A1, GAG, and SOX9 gene expression compared to hiPSC-MSCs. Following transplantation of hiPSC-MSC and hiPSC-MSC-derived chondrocytes into osteochondral defects of arthritic joints of athymic rats, magnetic resonance imaging studies showed gradual engraftment, and histological correlations demonstrated hyaline cartilage matrix production. Results present an efficient and clinically translatable approach for cartilage tissue regeneration via patient-derived hiPSCs, which could improve cartilage regeneration outcomes in arthritic joints.

    View details for DOI 10.1007/s12015-014-9581-5

    View details for Web of Science ID 000353149700004

    View details for PubMedID 25578634

  • Magnetic resonance imaging of stem cell apoptosis in arthritic joints with a caspase activatable contrast agent. ACS nano Nejadnik, H., Ye, D., Lenkov, O. D., Donig, J. S., Martin, J. E., Castillo, R., Derugin, N., Sennino, B., Rao, J., Daldrup-Link, H. 2015; 9 (2): 1150-1160


    About 43 million individuals in the U.S. encounter cartilage injuries due to trauma or osteoarthritis, leading to joint pain and functional disability. Matrix-associated stem cell implants (MASI) represent a promising approach for repair of cartilage defects. However, limited survival of MASI creates a significant bottleneck for successful cartilage regeneration outcomes and functional reconstitution. We report an approach for noninvasive detection of stem cell apoptosis with magnetic resonance imaging (MRI), based on a caspase-3-sensitive nanoaggregation MRI probe (C-SNAM). C-SNAM self-assembles into nanoparticles after hydrolysis by caspase-3, leading to 90% amplification of (1)H MR signal and prolonged in vivo retention. Following intra-articular injection, C-SNAM causes significant MR signal enhancement in apoptotic MASI compared to viable MASI. Our results indicate that C-SNAM functions as an imaging probe for stem cell apoptosis in MASI. This concept could be applied to a broad range of cell transplants and target sites.

    View details for DOI 10.1021/nn504494c

    View details for PubMedID 25597243

  • MR Imaging of Stem Cell Transplants in Arthritic Joints. Journal of stem cell research & therapy Daldrup-Link, H. E., Nejadnik, H. 2014; 4 (2): 165-?


    About 43 million individuals in the US currently suffer from disabilities due to arthritis. Cartilage defects are the major source of pain in the affected joints. Current treatments, whilst alleviating some of the clinical symptoms, prove insufficient to cure the underlying irreversible cartilage loss. Stem cells represent a unique source for restoration of cartilage defects. Pre-clinical and clinical trials are currently pursued to investigate the potential of various types of stem cells and stem cell derived chondrocytes to repair arthritic joints. A major challenge with all stem cell-mediated tissue regeneration approaches is death of the transplanted cells with clearance by the immune system. Our current inability to diagnose successful or unsuccessful engraftment of transplanted cells non-invasively in vivo represents a major bottleneck for the development of successful stem cell therapies. A large variety of non-invasive Magnetic Resonance (MR) imaging techniques have been developed over the last decade, which enable sensitive in vivo detection of Matrix Associated Stem Cell Implants (MASI) and early diagnosis of related complications. While initially focused on successfully harvesting cellular MR imaging approaches with easily applicable SuperParamagnetic Iron Oxide Nanoparticles (SPIO), our team began to observe details that will facilitate clinical translation. We therefore started a broader effort to define a comprehensive set of novel, clinically applicable imaging approaches for stem cell transplants in patients. We established immediately clinically applicable nanoparticle labeling techniques for tracking stem cell transplants with MR imaging; we have evaluated the long term MR signal effects of iron oxide nanoparticle labeled MASI in vivo; and we have defined distinct signal characteristics of labeled viable and apoptotic MASI. This review article will provide an overview over these efforts and discuss important implications for clinical translation.

    View details for PubMedID 25068075

  • Ferumoxytol: a new, clinically applicable label for stem-cell tracking in arthritic joints with MRI. Nanomedicine Khurana, A., Nejadnik, H., Chapelin, F., Lenkov, O., Gawande, R., Lee, S., Gupta, S. N., Aflakian, N., Derugin, N., Messing, S., Lin, G., Lue, T. F., Pisani, L., Daldrup-Link, H. E. 2013; 8 (12): 1969-1983


    Aim: To develop a clinically applicable MRI technique for tracking stem cells in matrix-associated stem-cell implants, using the US FDA-approved iron supplement ferumoxytol. Materials & methods: Ferumoxytol-labeling of adipose-derived stem cells (ADSCs) was optimized in vitro. A total of 11 rats with osteochondral defects of both femurs were implanted with ferumoxytol- or ferumoxides-labeled or unlabeled ADSCs, and underwent MRI up to 4 weeks post matrix-associated stem-cell implant. The signal-to-noise ratio of different matrix-associated stem-cell implant was compared with t-tests and correlated with histopathology. Results: An incubation concentration of 500 µg iron/ml ferumoxytol and 10 µg/ml protamine sulfate led to significant cellular iron uptake, T2 signal effects and unimpaired ADSC viability. In vivo, ferumoxytol- and ferumoxides-labeled ADSCs demonstrated significantly lower signal-to-noise ratio values compared with unlabeled controls (p < 0.01). Histopathology confirmed engraftment of labeled ADSCs, with slow dilution of the iron label over time. Conclusion: Ferumoxytol can be used for in vivo tracking of stem cells with MRI. Original submitted 28 February 2012; Revised submitted 8 November 2012.

    View details for DOI 10.2217/nnm.12.198

    View details for PubMedID 23534832

  • Iron Administration before Stem Cell Harvest Enables MR Imaging Tracking after Transplantation. Radiology Khurana, A., Chapelin, F., Beck, G., Lenkov, O. D., Donig, J., Nejadnik, H., Messing, S., Derugin, N., Chan, R. C., Gaur, A., Sennino, B., McDonald, D. M., Kempen, P. J., Tikhomirov, G. A., Rao, J., Daldrup-Link, H. E. 2013; 269 (1): 186-197


    Purpose:To determine whether intravenous ferumoxytol can be used to effectively label mesenchymal stem cells (MSCs) in vivo and can be used for tracking of stem cell transplants.Materials and Methods:This study was approved by the institutional animal care and use committee. Sprague-Dawley rats (6-8 weeks old) were injected with ferumoxytol 48 hours prior to extraction of MSCs from bone marrow. Ferumoxytol uptake by these MSCs was evaluated with fluorescence, confocal, and electron microscopy and compared with results of traditional ex vivo-labeling procedures. The in vivo-labeled cells were subsequently transplanted in osteochondral defects of 14 knees of seven athymic rats and were evaluated with magnetic resonance (MR) imaging up to 4 weeks after transplantation. T2 relaxation times of in vivo-labeled MSC transplants and unlabeled control transplants were compared by using t tests. MR data were correlated with histopathologic results.Results:In vivo-labeled MSCs demonstrated significantly higher ferumoxytol uptake compared with ex vivo-labeled cells. With electron microscopy, iron oxide nanoparticles were localized in secondary lysosomes. In vivo-labeled cells demonstrated significant T2 shortening effects in vitro and in vivo when they were compared with unlabeled control cells (T2 in vivo, 15.4 vs 24.4 msec; P < .05) and could be tracked in osteochondral defects for 4 weeks. Histologic examination confirmed the presence of iron in labeled transplants and defect remodeling.Conclusion:Intravenous ferumoxytol can be used to effectively label MSCs in vivo and can be used for tracking of stem cell transplants with MR imaging. This method eliminates risks of contamination and biologic alteration of MSCs associated with ex vivo-labeling procedures.© RSNA, 2013Supplemental material:

    View details for DOI 10.1148/radiol.13130858

    View details for PubMedID 23850832

  • 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


    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

  • Magnetic resonance imaging and tracking of stem cells. Methods in molecular biology (Clifton, N.J.) Nejadnik, H., Castillo, R., Daldrup-Link, H. E. 2013; 1052: 1-10


    To date, several stem cell labeling protocols have been developed, contributing to a fast growing and promising field of stem cell imaging by MRI (magnetic resonance imaging). Most of these methods utilize iron oxide nanoparticles (MION, SPIO, USPIO, VSIOP) for cell labeling, which provide negative (dark) signal effects on T2-weighted MR images. The following protocol describes stem cell labeling techniques with commercially available gadolinium chelates, which provide positive contrast on T1-weighted MR images, which can be advantageous for specific applications.

    View details for DOI 10.1007/7651_2013_16

    View details for PubMedID 23743862

  • MR Imaging Features of Gadofluorine-Labeled Matrix-Associated Stem Cell Implants in Cartilage Defects PLOS ONE Nejadnik, H., Henning, T. D., Thuy Do, T., Sutton, E. J., Baehner, F., Horvai, A., Sennino, B., McDonald, D., Meier, R., Misselwitz, B., Link, T. M., Daldrup-Link, H. E. 2012; 7 (12)
  • Intravenous Ferumoxytol Allows Noninvasive MR Imaging Monitoring of Macrophage Migration into Stem Cell Transplants RADIOLOGY Khurana, A., Nejadnik, H., Gawande, R., Lin, G., Lee, S., Messing, S., Castaneda, R., Derugin, N., Pisani, L., Lue, T. F., Daldrup-Link, H. E. 2012; 264 (3): 803-811


    To develop a clinically applicable imaging technique for monitoring differential migration of macrophages into viable and apoptotic matrix-associated stem cell implants (MASIs) in arthritic knee joints.With institutional animal care and use committee approval, six athymic rats were injected with intravenous ferumoxytol (0.5 mmol iron per kilogram of body weight) to preload macrophages of the reticuloendothelial system with iron oxide nanoparticles. Forty-eight hours later, all animals received MASIs of viable adipose-derived stem cells (ADSCs) in an osteochondral defect of the right femur and mitomycin-pretreated apoptotic ADSCs in an osteochondral defect of the left femur. One additional control animal each received intravenous ferumoxytol and bilateral scaffold-only implants (without cells) or bilateral MASIs without prior ferumoxytol injection. All knees were imaged with a 7.0-T magnetic resonance (MR) imaging unit with T2-weighted fast spin-echo sequences immediately after, as well as 2 and 4 weeks after, matrix-associated stem cell implantation. Signal-to-noise ratios (SNRs) of viable and apoptotic MASIs were compared by using a linear mixed-effects model. MR imaging data were correlated with histopathologic findings.All ADSC implants showed a slowly decreasing T2 signal over 4 weeks after matrix-associated stem cell implantation. SNRs decreased significantly over time for the apoptotic implants (SNRs on the day of matrix-associated stem cell implantation, 2 weeks after the procedure, and 4 weeks after the procedure were 16.9, 10.9, and 6.7, respectively; P = .0004) but not for the viable implants (SNRs on the day of matrix-associated stem cell implantation, 2 weeks after the procedure, and 4 weeks after the procedure were 17.7, 16.2, and 15.7, respectively; P = .2218). At 4 weeks after matrix-associated stem cell implantation, SNRs of apoptotic ADSCs were significantly lower than those of viable ADSCs (mean, 6.7 vs 15.7; P = .0013). This corresponded to differential migration of iron-loaded macrophages into MASIs.Iron oxide loading of macrophages in the reticuloendothelial system by means of intravenous ferumoxytol injection can be utilized to monitor differential migration of bone marrow macrophages into viable and apoptotic MASIs in a rat model.

    View details for DOI 10.1148/radiol.12112393

    View details for Web of Science ID 000308645500022

    View details for PubMedID 22820731

    View details for PubMedCentralID PMC3426856

  • Engineering stem cells for treatment of osteochondral defects SKELETAL RADIOLOGY Nejadnik, H., Daldrup-Link, H. E. 2012; 41 (1): 1-4

    View details for DOI 10.1007/s00256-011-1272-6

    View details for Web of Science ID 000297543700001

    View details for PubMedID 22072236

  • Somatic Differentiation and MR Imaging of Magnetically Labeled Human Embryonic Stem Cells CELL TRANSPLANTATION Nejadnik, H., Henning, T. D., Castaneda, R. T., Boddington, S., Taubert, S., Jha, P., Tavri, S., Golovko, D., Ackerman, L., Meier, R., Daldrup-Link, H. E. 2012; 21 (12): 2555-2567


    Magnetic resonance (MR) imaging of superparamagnetic iron oxide (SPIO)-labeled stem cells offers a noninvasive evaluation of stem cell engraftment in host organs. Excessive cellular iron load from SPIO labeling, however, impairs stem cell differentiation. The purpose of this study was to magnetically label human embryonic stem cells (hESCs) via a reduced exposure protocol that maintains a significant MR signal and no significant impairment to cellular pluripotency or differentiation potential. hESCs were labeled by simple incubation with Food and Drug Administration-approved ferumoxides, using concentrations of 50- 200 µg Fe/ml and incubation times of 3-24 h. The most reduced exposure labeling protocol that still provided a significant MR signal comparable to accepted labeling protocols was selected for subsequent studies. Labeled hESCs were compared to unlabeled controls for differences in pluripotency as studied by fluorescence staining for SSEA-1, SSEA-4, TRA-60, and TRA-81 and in differentiation capacity as studied by quantitative real-time PCR for hOCT4, hACTC1, hSOX1, and hAFP after differentiation into embryoid bodies (EBs). Subsequent MR and microscopy imaging were performed to evaluate for cellular iron distribution and long-term persistence of the label. An incubation concentration of 50 µg Fe/ml and incubation time of 3 h demonstrated a significantly reduced exposure protocol that yielded an intracellular iron uptake of 4.50 ± 0.27 pg, an iron content comparable to currently accepted SPIO labeling protocols. Labeled and unlabeled hESCs showed no difference in pluripotency or differentiation capacity. Ferumoxide-labeled hESCs demonstrated persistent MR contrast effects as embryoid bodies for 21 days. Electron microscopy confirmed persistent lysosomal storage of iron oxide particles in EBs up to 9 days, while additional microscopy visualization confirmed the iron distribution within single and multiple EBs. Labeling hESCs with ferumoxides by this tailored protocol reduces exposure of cells to the labeling agent while allowing for long-term visualization with MR imaging and the retention of cellular pluripotency and differentiation potential.

    View details for DOI 10.3727/096368912X653156

    View details for Web of Science ID 000315001400002

    View details for PubMedID 22862886

  • MR imaging features of gadofluorine-labeled matrix-associated stem cell implants in cartilage defects. PloS one Nejadnik, H., Henning, T. D., Do, T., Sutton, E. J., Baehner, F., Horvai, A., Sennino, B., McDonald, D., Meier, R., Misselwitz, B., Link, T. M., Daldrup-Link, H. E. 2012; 7 (12)


    The purpose of our study was to assess the chondrogenic potential and the MR signal effects of GadofluorineM-Cy labeled matrix associated stem cell implants (MASI) in pig knee specimen.Human mesenchymal stem cells (hMSCs) were labeled with the micelle-based contrast agent GadofluorineM-Cy. Ferucarbotran-labeled hMSCs, non-labeled hMSCs and scaffold only served as controls. Chondrogenic differentiation was induced and gene expression and histologic evaluation were performed. The proportions of spindle-shaped vs. round cells of chondrogenic pellets were compared between experimental groups using the Fisher's exact test. Labeled and unlabeled hMSCs and chondrocytes in scaffolds were implanted into cartilage defects of porcine femoral condyles and underwent MR imaging with T1- and T2-weighted SE and GE sequences. Contrast-to-noise ratios (CNR) between implants and adjacent cartilage were determined and analyzed for significant differences between different experimental groups using the Kruskal-Wallis test. Significance was assigned for p<0.017, considering a Bonferroni correction for multiple comparisons.Collagen type II gene expression levels were not significantly different between different groups (p>0.017). However, hMSC differentiation into chondrocytes was superior for unlabeled and GadofluorineM-Cy-labeled cells compared with Ferucarbotran-labeled cells, as evidenced by a significantly higher proportion of spindle cells in chondrogenic pellets (p<0.05). GadofluorineM-Cy-labeled hMSCs and chondrocytes showed a positive signal effect on T1-weighted images and a negative signal effect on T2-weighted images while Ferucarbotran-labeled cells provided a negative signal effect on all sequences. CNR data for both GadofluorineM-Cy-labeled and Ferucarbotran-labeled hMSCs were significantly different compared to unlabeled control cells on T1-weighted SE and T2*-weighted MR images (p<0.017).hMSCs can be labeled by simple incubation with GadofluorineM-Cy. The labeled cells provide significant MR signal effects and less impaired chondrogenesis compared to Ferucarbotran-labeled hMSCs. Thus, GadoflurineM-Cy might represent an alternative MR cell marker to Ferucarbotran, which is not distributed any more in Europe or North America.

    View details for DOI 10.1371/journal.pone.0049971

    View details for PubMedID 23251354

  • MR tracking of macrophage migration into matrix assosciated stem cell transplants via an indirect clinically applicable labeling technique Investigative Radiology Khurana A, Nejadnik H, Castaneda R, Gawande R, Derugin N, Pisani L, Daldrup-Link HE. 2011; 46 (11): 740
  • Vitamin D status of 6- to 7-year-old children living in Isfahan, Iran. Endokrynologia Polska Ardestani, P. M., Salek, M., Keshteli, A. H., Nejadnik, H., Amini, M., Hosseini, S. M., Rafati, H., Kelishadi, R., Hashemipour, M. 2010; 61 (4): 377-382


    Vitamin D is essential for the maintenance of good health, and vitamin D deficiency has been reported from many countries, including those with a lot of sunshine. This study was conducted to evaluate the vitamin D status in healthy 6- to 7-year-old children in Isfahan, Iran.Five hundred and thirteen healthy children were enrolled. Serum PTH and 25-hydroxyvitamin D (25-OHD) were measured. Dietary vitamin D intake, duration of daily sunlight exposure, and percentage of exposed body surface area were determined. 25-OHD levels < 20 ng/mL and < 10 ng/mL were defined as mild and severe vitamin D deficiency, respectively. The ROC curve was utilized to obtain a local cut-off point of vitamin D deficiency.25-OHD was < 20 ng/mL in 3% and < 33 ng/mL (local cut-off point of vitamin D deficiency) in 26% of subjects. Duration of sunlight exposure and daily intake of vitamin D had significant effects on serum level of vitamin D.A high prevalence of vitamin D deficiency in Isfahan children was observed in this study. Improvements in duration of sunlight exposure and daily intake of vitamin D can prevent vitamin D deficiency in these children.

    View details for PubMedID 20806182

  • Autologous Bone Marrow-Derived Mesenchymal Stem Cells Versus Autologous Chondrocyte Implantation An Observational Cohort Study AMERICAN JOURNAL OF SPORTS MEDICINE Nejadnik, H., Hui, J. H., Choong, E. P., Tai, B., Lee, E. H. 2010; 38 (6): 1110-1116


    First-generation autologous chondrocyte implantation has limitations, and introducing new effective cell sources can improve cartilage repair.This study was conducted to compare the clinical outcomes of patients treated with first-generation autologous chondrocyte implantation to patients treated with autologous bone marrow-derived mesenchymal stem cells (BMSCs).Cohort study; Level of evidence, 3.Seventy-two matched (lesion site and age) patients underwent cartilage repair using chondrocytes (n = 36) or BMSCs (n = 36). Clinical outcomes were measured before operation and 3, 6, 9, 12, 18, and 24 months after operation using the International Cartilage Repair Society (ICRS) Cartilage Injury Evaluation Package, which included questions from the Short-Form Health Survey, International Knee Documentation Committee (IKDC) subjective knee evaluation form, Lysholm knee scale, and Tegner activity level scale.There was significant improvement in the patients' quality of life (physical and mental components of the Short Form-36 questionnaire included in the ICRS package) after cartilage repair in both groups (autologous chondrocyte implantation and BMSCs). However, there was no difference between the BMSC and the autologous chondrocyte implantation group in terms of clinical outcomes except for Physical Role Functioning, with a greater improvement over time in the BMSC group (P = .044 for interaction effect). The IKDC subjective knee evaluation (P = .861), Lysholm (P = .627), and Tegner (P = .200) scores did not show any significant difference between groups over time. However, in general, men showed significantly better improvements than women. Patients younger than 45 years of age scored significantly better than patients older than 45 years in the autologous chondrocyte implantation group, but age did not make a difference in outcomes in the BMSC group.Using BMSCs in cartilage repair is as effective as chondrocytes for articular cartilage repair. In addition, it required 1 less knee surgery, reduced costs, and minimized donor-site morbidity.

    View details for DOI 10.1177/0363546509359067

    View details for Web of Science ID 000278062200004

    View details for PubMedID 20392971

  • Vitamin D status of 6-to 7-year-old children living in Isfahan, Iran ENDOKRYNOLOGIA POLSKA Ardestani, P. M., Salek, M., Keshteli, A. H., Nejadnik, H., Amini, M., Hosseini, S. M., Rafati, H., Kelishadi, R., Hashemipour, M. 2010; 61 (4): 377-381
  • Cavernous angioma: a clinical study of 35 cases with review of the literature NEUROLOGICAL RESEARCH Ebrahimi, A., Etemadifar, M., Ardestani, P. M., Maghzi, A. H., Jaffe, S., Nejadnik, H. 2009; 31 (8): 785-793


    Cavernous angioma is a vascular malformation which can be found in any region within the central nervous system.There are few clinical and demographic cavernous angioma studies with large sample sizes. Therefore, the present study was designed to provide further information on the clinical and demographic characteristics of cavernous angioma using a relatively large sample of Persian patients.Patients with cavernous angioma were recruited from the outpatient neurology clinics in Isfahan, Iran, from October 2003 to October 2006.In all cases, the diagnosis of cavernous angioma was based on brain magnetic resonance imaging. There were 35 patients (female/male: 17 : 18) identified with cavernous angioma. The mean age at presentation was 28.8 years. Initial manifestations included seizures in 16, headache in 11 and intracranial hemorrhage in eight patients. During follow-up, all patients experienced seizures and 19 developed headaches. Depression, vertigo, nausea, vomiting, disequilibrium, loss of consciousness and sensorimotor symptoms were also observed.Some of the findings of the present study were in accordance with previous studies. However, more of our patients with positive family history had solitary rather than multiple lesions, and more of our patients had generalized tonic-clonic seizures rather than partial seizures. Moreover, our data demonstrated that if there is a history of cavernous angioma with intracranial hemorrhage in family members, the presenting cavernous angioma patient is more prone to intracranial hemorrhage.

    View details for DOI 10.1179/016164109X12445505689445

    View details for Web of Science ID 000269131700003

    View details for PubMedID 19723446

  • Vitamin D deficiency among pregnant women and their newborns in Isfahan, Iran EXPERIMENTAL AND CLINICAL ENDOCRINOLOGY & DIABETES Salek, M., Hashemipour, M., Aminorroaya, A., Gheiratmand, A., Kelishadi, R., Ardestani, P. M., Nejadnik, H., Amini, M., Zolfaghari, B. 2008; 116 (6): 352-356


    Vitamin D deficiency is one of the major health problems and unexpectedly has a high prevalence in sunny countries (e.g. Middle East). In this study we determined the prevalence of vitamin D deficiency in pregnant women and their newborns in Isfahan, a sunny city in Iran.In a cross-sectional study, 88 newborns born in Beheshty hospital, affiliated to Isfahan University of Medical Sciences (August-September, 2005) and their mothers were studied. Their data were collected by questionnaires and blood sampling was done to measure serum alkaline phosphatase (ALP), calcium, phosphorus, 25 (OH) vitamin D and parathormone (PTH). Vitamin D deficiency defined as levels of 25 (OH) D < 20 and < 12.5 ng/ml for mothers and newborns, respectively and local cut-offs defined as levels in which mean serum PTH started to increase.The prevalence of vitamin D deficiency according to 25 (OH) D < 20 ng/ml in mothers and < 12.5 ng/ml in newborns was 5.7% and 4.5%, respectively. According to local cut-offs (35 ng/ml for mothers and 26 ng/ml for newborns) 26.1% of mothers and 53.4% of newborns were vitamin D deficient.According to local definition, vitamin D deficiency is a health problem in pregnant women and their newborns in this sunny city.

    View details for DOI 10.1055/s-2008-1042403

    View details for Web of Science ID 000257245900008

    View details for PubMedID 18700279

  • Effect of lime juice consumption on urine pH value SAUDI MEDICAL JOURNAL Mazdak, H., Ardestani, P. M., Nejadnik, H. 2006; 27 (12): 1923-1924

    View details for Web of Science ID 000244073200030

    View details for PubMedID 17143381