Bio

Honors & Awards


  • Medical Fellows Award, Howard Hughes Medical Institute (2014-15)
  • Western Regional Representative, Howard Hughes Medical Institute (2014-15)
  • Medical Scholars Award, Stanford (2014-15)

Education & Certifications


  • Bachelor of Arts, Harvard University, Psychology (2011)

Publications

Journal Articles


  • Smoothened Inhibitors in Sonic Hedgehog Subgroup Medulloblastoma Journal of Clinical Oncology Ransohoff, K. J., Sarin, K. Y., Tang, J. Y. 2015

    View details for DOI 10.1200/JCO.2015.62.2225

  • Costimulation-Adhesion Blockade Is Superior to Cyclosporine A and Prednisone Immunosuppressive Therapy for Preventing Rejection of Differentiated Human Embryonic Stem Cells Following Transplantation STEM CELLS Huber, B. C., Ransohoff, J. D., Ransohoff, K. J., Riegler, J., Ebert, A., Kodo, K., Gong, Y., Sanchez-Freire, V., Dey, D., Kooreman, N. G., Diecke, S., Zhang, W. Y., Odegaard, J., Hu, S., Gold, J. D., Robbins, R. C., Wu, J. C. 2013; 31 (11): 2354-2363

    Abstract

    Rationale: Human embryonic stem cell (hESC) derivatives are attractive candidates for therapeutic use. The engraftment and survival of hESC derivatives as xenografts or allografts require effective immunosuppression to prevent immune cell infiltration and graft destruction. Objective: To test the hypothesis that a short-course, dual-agent regimen of two costimulation-adhesion blockade agents can induce better engraftment of hESC derivatives compared to current immunosuppressive agents. Methods and Results: We transduced hESCs with a double fusion reporter gene construct expressing firefly luciferase (Fluc) and enhanced green fluorescent protein, and differentiated these cells to endothelial cells (hESC-ECs). Reporter gene expression enabled longitudinal assessment of cell engraftment by bioluminescence imaging. Costimulation-adhesion therapy resulted in superior hESC-EC and mouse EC engraftment compared to cyclosporine therapy in a hind limb model. Costimulation-adhesion therapy also promoted robust hESC-EC and hESC-derived cardiomyocyte survival in an ischemic myocardial injury model. Improved hESC-EC engraftment had a cardioprotective effect after myocardial injury, as assessed by magnetic resonance imaging. Mechanistically, costimulation-adhesion therapy is associated with systemic and intragraft upregulation of T-cell immunoglobulin and mucin domain 3 (TIM3) and a reduced proinflammatory cytokine profile. Conclusions: Costimulation-adhesion therapy is a superior alternative to current clinical immunosuppressive strategies for preventing the post-transplant rejection of hESC derivatives. By extending the window for cellular engraftment, costimulation-adhesion therapy enhances functional preservation following ischemic injury. This regimen may function through a TIM3-dependent mechanism. Stem Cells 2013;31:2354-2363.

    View details for DOI 10.1002/stem.1501

    View details for Web of Science ID 000327025600007

  • MicroRNA-302 Increases Reprogramming Efficiency via Repression of NR2F2 STEM CELLS Hu, S., Wilson, K. D., Ghosh, Z., Han, L., Wang, Y., Lan, F., Ransohoff, K. J., Burridge, P., Wu, J. C. 2013; 31 (2): 259-268

    Abstract

    MicroRNAs (miRNAs) have emerged as critical regulators of gene expression through translational inhibition and RNA decay and have been implicated in the regulation of cellular differentiation, proliferation, angiogenesis, and apoptosis. In this study, we analyzed global miRNA and mRNA microarrays to predict novel miRNA-mRNA interactions in human embryonic stem cells and induced pluripotent stem cells (iPSCs). In particular, we demonstrate a regulatory feedback loop between the miR-302 cluster and two transcription factors, NR2F2 and OCT4. Our data show high expression of miR-302 and OCT4 in pluripotent cells, while NR2F2 is expressed exclusively in differentiated cells. Target analysis predicts that NR2F2 is a direct target of miR-302, which we experimentally confirm by reporter luciferase assays and real-time polymerase chain reaction. We also demonstrate that NR2F2 directly inhibits the activity of the OCT4 promoter and thus diminishes the positive feedback loop between OCT4 and miR-302. Importantly, higher reprogramming efficiencies were obtained when we reprogrammed human adipose-derived stem cells into iPSCs using four factors (KLF4, C-MYC, OCT4, and SOX2) plus miR-302 (this reprogramming cocktail is hereafter referred to as "KMOS3") when compared to using four factors ("KMOS"). Furthermore, shRNA knockdown of NR2F2 mimics the over-expression of miR-302 by also enhancing reprogramming efficiency. Interestingly, we were unable to generate iPSCs from miR-302a/b/c/d alone, which is in contrast to previous publications that have reported that miR-302 by itself can reprogram human skin cancer cells and human hair follicle cells. Taken together, these findings demonstrate that miR-302 inhibits NR2F2 and promotes pluripotency through indirect positive regulation of OCT4. This feedback loop represents an important new mechanism for understanding and inducing pluripotency in somatic cells.

    View details for DOI 10.1002/stem.1278

    View details for Web of Science ID 000314873000006

  • In Vivo Functional and Transcriptional Profiling of Bone Marrow Stem Cells After Transplantation Into Ischemic Myocardium ARTERIOSCLEROSIS THROMBOSIS AND VASCULAR BIOLOGY Sheikh, A. Y., Huber, B. C., Narsinh, K. H., Spin, J. M., van der Bogt, K., de Almeida, P. E., Ransohoff, K. J., Kraft, D. L., Fajardo, G., Ardigo, D., Ransohoff, J., Bernstein, D., Fischbein, M. P., Robbins, R. C., Wu, J. C. 2012; 32 (1): 92-102

    Abstract

    Clinical trials of bone marrow-derived stem cell therapy for the heart have yielded variable results. The basic mechanism(s) that underlies their potential efficacy remains unknown. In the present study, we evaluated the survival kinetics, transcriptional response, and functional outcome of intramyocardial bone marrow mononuclear cell (BMMC) transplantation for cardiac repair in a murine myocardial infarction model.We used bioluminescence imaging and high-throughput transcriptional profiling to evaluate the in vivo survival kinetics and gene expression changes of transplanted BMMCs after their engraftment into ischemic myocardium. Our results demonstrate short-lived survival of cells following transplant, with less than 1% of cells surviving by 6 weeks posttransplantation. Moreover, transcriptomic analysis of BMMCs revealed nonspecific upregulation of various cell regulatory genes, with a marked downregulation of cell differentiation and maturation pathways. BMMC therapy caused limited improvement of heart function as assessed by echocardiography, invasive hemodynamics, and positron emission tomography. Histological evaluation of cell fate further confirmed findings of the in vivo cell tracking and transcriptomic analysis.Collectively, these data suggest that BMMC therapy, in its present iteration, may be less efficacious than once thought. Additional refinement of existing cell delivery protocols should be considered to induce better therapeutic efficacy.

    View details for DOI 10.1161/ATVBAHA.111.238618

    View details for Web of Science ID 000298288700014

    View details for PubMedID 22034515

  • Micro-CT for Characterization of Murine CV Disease Models JACC-CARDIOVASCULAR IMAGING Sheikh, A. Y., van der Bogt, K. E., Doyle, T. C., Sheikh, M. K., Ransohoff, K. J., Ali, Z. A., Palmer, O. P., Robbins, R. C., Fischbein, M. P., Wu, J. C. 2010; 3 (7): 783-785

    View details for DOI 10.1016/j.jcmg.2010.01.012

    View details for Web of Science ID 000281626700015

    View details for PubMedID 20633858

  • Advances in cardiovascular molecular imaging for tracking stem cell therapy THROMBOSIS AND HAEMOSTASIS Ransohoff, K. J., Wu, J. C. 2010; 104 (1): 13-22

    Abstract

    The high mortality rate associated with cardiovascular disease is partially due to the lack of proliferative cells in the heart. Without adequate repair following myocardial infarction, progressive dilation can lead to heart failure. Stem cell therapies present one promising option for treating cardiovascular disease, though the specific mechanisms by which they benefit the heart remain unclear. Before stem cell therapies can be used safely in human populations, their biology must be investigated using innovative technologies such as multi-modality molecular imaging. The present review will discuss the basic principles, labelling techniques, clinical applications, and drawbacks associated with four major modalities: radionuclide imaging, magnetic resonance imaging, bioluminescence imaging, and fluorescence imaging.

    View details for DOI 10.1160/TH09-08-0530

    View details for Web of Science ID 000280298300004

    View details for PubMedID 20458434

  • Poor Functional Recovery After Transplantation of Diabetic Bone Marrow Stem Cells in Ischemic Myocardium JOURNAL OF HEART AND LUNG TRANSPLANTATION Govaert, J. A., Swijnenburg, R., Schrepfer, S., Xie, X., van der Bogt, K. E., Hoyt, G., Stein, W., Ransohoff, K. J., Robbins, R. C., Wu, J. C. 2009; 28 (11): 1158-1165

    Abstract

    Autologous bone marrow mononuclear cell (BMMC) therapy has shown promise for improving cardiac function after myocardial infarction. The efficiency of such therapy for diabetic patients remains unknown.BMMCs were harvested from type 2 diabetic male BKS.Cg-m+/+Lepr(db)/J mice or C57BLKS/J (non-diabetic control) mice and were isolated using Ficoll-based separation. Cell characterization was performed by flow cytometry. Cell viability was determined by apoptosis and proliferation assays. Female BKS.Cg-m+/+Lepr(db)/J mice underwent left anterior descending artery ligation and were randomized into 3 groups receiving 2.5 x 10(6) diabetic BMMCs (n = 8), 2.5 x 10(6) control BMMCs (n = 8), or phosphate-buffered saline (n = 6). At Week 5, cardiac function was assessed with echocardiography and invasive hemodynamic measurements. Post-mortem cell survival was quantified by TaqMan real-time transcription polymerase chain reaction (RT-PCR) for the male Sry gene.BKS.Cg-m+/+Lepr(db)/J BMMCs showed a significantly lower mononuclear fraction and a significantly lower proliferation rate compared with C57BLKS/J BMMCs. Fractional shorting (40.1% +/- 1.2% vs 30.3% +/- 1.9%; p = 0.001) and cardiac output (4,166 +/- 393 vs 2,246 +/- 462 microl/min; p = 0.016) significantly improved for mice treated with control BMMCs injection compared with those treated with diabetic BMMCs, respectively. This difference could not be attributed to difference in cell engraftment because TaqMan RT-PCR showed no significant difference in cell survival in infarcted hearts between the 2 groups.Diabetic BMMCs are significantly impaired in their ability to improve cardiac function after myocardial infarction compared with control BMMCs. These findings could have significant clinical implication regarding autologous BMMC therapy in diabetic patients.

    View details for DOI 10.1016/j.healun.2009.06.018

    View details for Web of Science ID 000271795900007

    View details for PubMedID 19782602

  • Comparison of different adult stem cell types for treatment of myocardial ischemia CIRCULATION van der Bogt, K. E., Sheikh, A. Y., Schrepfer, S., Hoyt, G., Cao, F., Ransohoff, K. J., Swijnenburg, R., Pearl, J., Lee, A., Fischbein, M., Contag, C. H., Robbins, R. C., Wu, J. C. 2008; 118 (14): S121-U166

    Abstract

    A comparative analysis of the efficacy of different cell candidates for the treatment of heart disease remains to be described. This study is designed to evaluate the therapeutic efficacy of 4 cell types in a murine model of myocardial infarction.Bone marrow mononuclear cells (MN), mesenchymal stem cells (MSC), skeletal myoblasts (SkMb), and fibroblasts (Fibro) expressing firefly luciferase (Fluc) and green fluorescence protein (GFP) were characterized by flow cytometry, bioluminescence imaging (BLI), and luminometry. Female FVB mice (n=70) underwent LAD ligation and intramyocardially received one cell type (5x10(5)) or PBS. Cell survival was measured by BLI and by TaqMan PCR. Cardiac function was assessed by echocardiography and invasive hemodynamic measurements. Fluc expression correlated with cell number in all groups (r(2)>0.93). In vivo BLI revealed acute donor cell death of MSC, SkMb, and Fibro within 3 weeks after transplantation. By contrast, cardiac signals were still present after 6 weeks in the MN group, as confirmed by TaqMan PCR (P<0.01). Echocardiography showed significant preservation of fractional shortening in the MN group compared to controls (P<0.05). Measurements of left ventricular end-systolic/diastolic volumes revealed that the least amount of ventricular dilatation occurred in the MN group (P<0.05). Histology confirmed the presence of MN, although there was no evidence of transdifferentiation by donor MN into cardiomyocytes.This is the first study to show that compared to MSC, SkMB, and Fibro, MN exhibit a more favorable survival pattern, which translates into a more robust preservation of cardiac function.

    View details for DOI 10.1161/CIRCULATIONAHA.107.759480

    View details for Web of Science ID 000259648600018

    View details for PubMedID 18824743

  • Immunosuppressive therapy mitigates immunological rejection of human embryonic stem cell xenografts PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Swijnenburg, R., Schrepfer, S., Govaert, J. A., Cao, F., Ransohoff, K., Sheikh, A. Y., Haddad, M., Connolly, A. J., Davis, M. M., Robbins, R. C., Wu, J. C. 2008; 105 (35): 12991-12996

    Abstract

    Given their self-renewing and pluripotent capabilities, human embryonic stem cells (hESCs) are well poised as a cellular source for tissue regeneration therapy. However, the host immune response against transplanted hESCs is not well characterized. In fact, controversy remains as to whether hESCs have immune-privileged properties. To address this issue, we used in vivo bioluminescent imaging to track the fate of transplanted hESCs stably transduced with a double-fusion reporter gene consisting of firefly luciferase and enhanced GFP. We show that survival after transplant is significantly limited in immunocompetent as opposed to immunodeficient mice. Repeated transplantation of hESCs into immunocompetent hosts results in accelerated hESC death, suggesting an adaptive donor-specific immune response. Our data demonstrate that transplanted hESCs trigger robust cellular and humoral immune responses, resulting in intragraft infiltration of inflammatory cells and subsequent hESC rejection. Moreover, we have found CD4(+) T cells to be an important modulator of hESC immune-mediated rejection. Finally, we show that immunosuppressive drug regimens can mitigate the anti-hESC immune response and that a regimen of combined tacrolimus and sirolimus therapies significantly prolongs survival of hESCs for up to 28 days. Taken together, these data suggest that hESCs are immunogenic, trigger both cellular and humoral-mediated pathways, and, as a result, are rapidly rejected in xenogeneic hosts. This process can be mitigated by a combined immunosuppressive regimen as assessed by molecular imaging approaches.

    View details for DOI 10.1073/pnas.0805802105

    View details for Web of Science ID 000259343000067

    View details for PubMedID 18728188

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