Bio

Honors & Awards


  • Graduate Research Fellowship, National Science Foundation (2014-2017)
  • Manuscript Award, Stanford Cardiovascular Institute (2014)
  • Graduate Student Travel Grant, Stanford Biosciences Office of Graduate Education (2014, 2015)
  • Predoctoral Graduate Research Fellowship, American Heart Association (2013-2015)

Education & Certifications


  • Certificate, Stanford Graduate School of Business, Stanford Ignite (2014)
  • Bachelor of Science, Duke University, Biology (2012)

Service, Volunteer and Community Work


  • Program Assistant, Stanford Summer Research Program (SSRP) (6/1/2013 - Present)

    Location

    Stanford University

Research & Scholarship

Current Research and Scholarly Interests


My research focuses on the molecular mechanisms driving cardiovascular development, disease, and regeneration. I am interested in basic cardiomyocyte biology, utilizing induced pluripotent stem cells for the in-vitro modeling of cardiovascular disorders, and using stem cell-derived cardiomyocytes for high-throughput drug screening/discovery.

Lab Affiliations


Publications

Journal Articles


  • Human induced pluripotent stem cell-derived cardiomyocytes as an in vitro model for coxsackievirus b3-induced myocarditis and antiviral drug screening platform. Circulation research Sharma, A., Marceau, C., Hamaguchi, R., Burridge, P. W., Rajarajan, K., Churko, J. M., Wu, H., Sallam, K. I., Matsa, E., Sturzu, A. C., Che, Y., Ebert, A., Diecke, S., Liang, P., Red-Horse, K., Carette, J. E., Wu, S. M., Wu, J. C. 2014; 115 (6): 556-566

    Abstract

    Rationale: Viral myocarditis is a life-threatening illness that may lead to heart failure or cardiac arrhythmias. A major causative agent for viral myocarditis is the B3 strain of coxsackievirus, a positive-sense RNA enterovirus. However, human cardiac tissues are difficult to procure in sufficient enough quantities for studying the mechanisms of cardiac-specific viral infection. Objective: This study examined whether human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) could be used to model the pathogenic processes of coxsackievirus-induced viral myocarditis and to screen antiviral therapeutics for efficacy. Methods and Results: Human iPSC-CMs were infected with a luciferase-expressing coxsackievirus B3 strain (CVB3-Luc). Brightfield microscopy, immunofluorescence, and calcium imaging were utilized to characterize virally-infected hiPSC-CMs for alterations in cellular morphology and calcium handling. Viral proliferation in hiPSC-CMs was quantified using bioluminescence imaging. Antiviral compounds including interferon beta 1 (IFNβ1), ribavirin, pyrrolidine dithiocarbamate, and fluoxetine were tested for their capacity to abrogate CVB3-Luc proliferation in hiPSC-CMs in vitro. The ability of these compounds to reduce CVB3-Luc proliferation in hiPSC-CMs was consistent with reported drug effects in previous studies. Mechanistic analyses via gene expression profiling of hiPSC-CMs infected with CVB3-Luc revealed an activation of viral RNA and protein clearance pathways after IFNβ1 treatment. Conclusions: This study demonstrates that hiPSC-CMs express the coxsackievirus and adenovirus receptor, are susceptible to coxsackievirus infection, and can be used to predict antiviral drug efficacy. Our results suggest that the hiPSC-CM/CVB3-Luc assay is a sensitive platform that can screen novel antiviral therapeutics for their effectiveness in a high-throughput fashion.

    View details for DOI 10.1161/CIRCRESAHA.115.303810

    View details for PubMedID 25015077

  • Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Cardiovascular Disease Modeling and Drug Screening Stem Cell Research & Therapy Sharma, A., Wu, J. C., Wu, S. M. 2013

    View details for DOI 10.1186/scrt380

  • Modeling Cardiovascular Diseases with Patient-Specific Human Pluripotent Stem Cell-Derived Cardiomyocytes. Methods in molecular biology (Clifton, N.J.) Burridge, P. W., Diecke, S., Matsa, E., Sharma, A., Wu, H., Wu, J. C. 2015

    Abstract

    The generation of cardiomyocytes from human induced pluripotent stem cells (hiPSCs) provides a source of cells that accurately recapitulate the human cardiac pathophysiology. The application of these cells allows for modeling of cardiovascular diseases, providing a novel understanding of human disease mechanisms and assessment of therapies. Here, we describe a stepwise protocol developed in our laboratory for the generation of hiPSCs from patients with a specific disease phenotype, long-term hiPSC culture and cryopreservation, differentiation of hiPSCs to cardiomyocytes, and assessment of disease phenotypes. Our protocol combines a number of innovative tools that include a codon-optimized mini intronic plasmid (CoMiP), chemically defined culture conditions to achieve high efficiencies of reprogramming and differentiation, and calcium imaging for assessment of cardiomyocyte phenotypes. Thus, this protocol provides a complete guide to use a patient cohort on a testable cardiomyocyte platform for pharmacological drug assessment.

    View details for DOI 10.1007/7651_2015_196

    View details for PubMedID 25690476

  • The Fetal Mammalian Heart Generates a Robust Compensatory Response to Cell Loss. Circulation Sturzu, A. C., Rajarajan, K., Passer, D., Plonowska, K., Riley, A., Tan, T. C., Sharma, A., Xu, A. F., Engels, M. C., Feistritzer, R., Li, G., Selig, M. K., Geissler, R., Robertson, K. D., Scherrer-Crosbie, M., Domian, I. J., Wu, S. M. 2015

    Abstract

    -Heart development is tightly regulated by signaling events acting upon a defined number of progenitor and differentiated cardiac cells. While loss-of-function of these signaling pathways leads to congenital malformation, the consequences of cardiac progenitor cell (CPC) or embryonic cardiomyocyte loss are less clear. In this study, we tested the hypothesis that embryonic mouse hearts exhibit a robust mechanism for regeneration following extensive cell loss.-By combining a conditional cell ablation approach with a novel blastocyst complementation strategy, we generated murine embryos that exhibit a full spectrum of CPC or cardiomyocyte ablation. Remarkably, ablation of up to 60% of CPCs at embryonic day 7.5 was well-tolerated and permitted embryo survival. Ablation of embryonic cardiomyocytes to a similar degree (50-60%) at embryonic day 9.0 could be fully rescued by residual myocytes with no obvious adult cardiac functional deficit. In both ablation models, an increase in cardiomyocyte proliferation rate was detected and accounted for at least some of the rapid recovery of myocardial cellularity and heart size.-Our study defines the threshold for cell loss in the embryonic mammalian heart and reveals a robust cardiomyocyte compensatory response that sustains normal fetal development.

    View details for DOI 10.1161/CIRCULATIONAHA.114.011490

    View details for PubMedID 25995316

  • Derivation of Highly Purified Cardiomyocytes from Human Induced Pluripotent Stem Cells Using Small Molecule-modulated Differentiation and Subsequent Glucose Starvation. Journal of visualized experiments : JoVE Sharma, A., Li, G., Rajarajan, K., Hamaguchi, R., Burridge, P. W., Wu, S. M. 2015

    Abstract

    Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have become an important cell source to address the lack of primary cardiomyocytes available for basic research and translational applications. To differentiate hiPSCs into cardiomyocytes, various protocols including embryoid body (EB)-based differentiation and growth factor induction have been developed. However, these protocols are inefficient and highly variable in their ability to generate purified cardiomyocytes. Recently, a small molecule-based protocol utilizing modulation of Wnt/β-Catenin signaling was shown to promote cardiac differentiation with high efficiency. With this protocol, greater than 50%-60% of differentiated cells were cardiac troponin-positive cardiomyocytes were consistently observed. To further increase cardiomyocyte purity, the differentiated cells were subjected to glucose starvation to specifically eliminate non-cardiomyocytes based on the metabolic differences between cardiomyocytes and non-cardiomyocytes. Using this selection strategy, we consistently obtained a greater than 30% increase in the ratio of cardiomyocytes to non-cardiomyocytes in a population of differentiated cells. These highly purified cardiomyocytes should enhance the reliability of results from human iPSC-based in vitro disease modeling studies and drug screening assays.

    View details for DOI 10.3791/52628

    View details for PubMedID 25867738

  • Novel codon-optimized mini-intronic plasmid for efficient, inexpensive, and xeno-free induction of pluripotency. Scientific reports Diecke, S., Lu, J., Lee, J., Termglinchan, V., Kooreman, N. G., Burridge, P. W., Ebert, A. D., Churko, J. M., Sharma, A., Kay, M. A., Wu, J. C. 2015; 5: 8081-?

    Abstract

    The development of human induced pluripotent stem cell (iPSC) technology has revolutionized the regenerative medicine field. This technology provides a powerful tool for disease modeling and drug screening approaches. To circumvent the risk of random integration into the host genome caused by retroviruses, non-integrating reprogramming methods have been developed. However, these techniques are relatively inefficient or expensive. The mini-intronic plasmid (MIP) is an alternative, robust transgene expression vector for reprogramming. Here we developed a single plasmid reprogramming system which carries codon-optimized (Co) sequences of the canonical reprogramming factors (Oct4, Klf4, Sox2, and c-Myc) and short hairpin RNA against p53 ("4-in-1 CoMiP"). We have derived human and mouse iPSC lines from fibroblasts by performing a single transfection. Either independently or together with an additional vector encoding for LIN28, NANOG, and GFP, we were also able to reprogram blood-derived peripheral blood mononuclear cells (PBMCs) into iPSCs. Taken together, the CoMiP system offers a new highly efficient, integration-free, easy to use, and inexpensive methodology for reprogramming. Furthermore, the CoMIP construct is color-labeled, free of any antibiotic selection cassettes, and independent of the requirement for expression of the Epstein-Barr Virus nuclear antigen (EBNA), making it particularly beneficial for future applications in regenerative medicine.

    View details for DOI 10.1038/srep08081

    View details for PubMedID 25628230

  • Insulin-like growth factor promotes cardiac lineage induction in vitro by selective expansion of early mesoderm. Stem cells Engels, M. C., Rajarajan, K., Feistritzer, R., Sharma, A., Nielsen, U. B., Schalij, M. J., de Vries, A. A., Pijnappels, D. A., Wu, S. M. 2014; 32 (6): 1493-1502

    Abstract

    A thorough understanding of the developmental signals that direct pluripotent stem cells (PSCs) towards a cardiac fate is essential for translational applications in disease modeling and therapy. We screened a panel of 44 cytokines/signaling molecules for their ability to enhance Nkx2.5(+) cardiac progenitor cell (CPC) formation during in vitro embryonic stem cell (ESC) differentiation. Treatment of murine ESCs with insulin or insulin-like growth factors (IGF1/2) during early differentiation increased mesodermal cell proliferation and, consequently, CPC formation. Furthermore, we show that downstream mediators of IGF signaling (e.g. phospho-Akt and mTOR) are required for this effect. These data support a novel role for IGF family ligands to expand the developing mesoderm and promote cardiac differentiation. Insulin or IGF treatment could provide an effective strategy to increase the PSC-based generation of CPCs and cardiomyocytes for applications in regenerative medicine. Stem Cells 2014.

    View details for DOI 10.1002/stem.1660

    View details for PubMedID 24496962

  • Screening drug-induced arrhythmia [corrected] using human induced pluripotent stem cell-derived cardiomyocytes and low-impedance microelectrode arrays. Circulation Navarrete, E. G., Liang, P., Lan, F., Sanchez-Freire, V., Simmons, C., Gong, T., Sharma, A., Burridge, P. W., Patlolla, B., Lee, A. S., Wu, H., Beygui, R. E., Wu, S. M., Robbins, R. C., Bers, D. M., Wu, J. C. 2013; 128 (11): S3-13

    Abstract

    Drug-induced arrhythmia is one of the most common causes of drug development failure and withdrawal from market. This study tested whether human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) combined with a low-impedance microelectrode array (MEA) system could improve on industry-standard preclinical cardiotoxicity screening methods, identify the effects of well-characterized drugs, and elucidate underlying risk factors for drug-induced arrhythmia. hiPSC-CMs may be advantageous over immortalized cell lines because they possess similar functional characteristics as primary human cardiomyocytes and can be generated in unlimited quantities.Pharmacological responses of beating embryoid bodies exposed to a comprehensive panel of drugs at 65 to 95 days postinduction were determined. Responses of hiPSC-CMs to drugs were qualitatively and quantitatively consistent with the reported drug effects in literature. Torsadogenic hERG blockers, such as sotalol and quinidine, produced statistically and physiologically significant effects, consistent with patch-clamp studies, on human embryonic stem cell-derived cardiomyocytes hESC-CMs. False-negative and false-positive hERG blockers were identified accurately. Consistent with published studies using animal models, early afterdepolarizations and ectopic beats were observed in 33% and 40% of embryoid bodies treated with sotalol and quinidine, respectively, compared with negligible early afterdepolarizations and ectopic beats in untreated controls.We found that drug-induced arrhythmias can be recapitulated in hiPSC-CMs and documented with low impedance MEA. Our data indicate that the MEA/hiPSC-CM assay is a sensitive, robust, and efficient platform for testing drug effectiveness and for arrhythmia screening. This system may hold great potential for reducing drug development costs and may provide significant advantages over current industry standard assays that use immortalized cell lines or animal models.

    View details for DOI 10.1161/CIRCULATIONAHA.112.000570

    View details for PubMedID 24030418

  • Autophagy - the friendly fire in endothelial cell regeneration. Focus on "Autophagy in endothelial progenitor cells is cytoprotective in hypoxic conditions" AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY Sharma, A., Wu, S. M. 2013; 304 (7): C614-C616

    View details for DOI 10.1152/ajpcell.00046.2013

    View details for Web of Science ID 000316995700003

    View details for PubMedID 23407881

  • Of fish and men: clonal lineage analysis identifies divergence in myocardial development. Circulation research Sharma, A., Wu, S. M. 2013; 112 (4): 583-585

    View details for DOI 10.1161/CIRCRESAHA.113.300964

    View details for PubMedID 23410876

  • Endoglin regulates PI3-kinase/Akt trafficking and signaling to alter endothelial capillary stability during angiogenesis MOLECULAR BIOLOGY OF THE CELL Lee, N. Y., Golzio, C., Gatza, C. E., Sharma, A., Katsanis, N., Blobe, G. C. 2012; 23 (13): 2412-2423

    Abstract

    Endoglin (CD105) is an endothelial-specific transforming growth factor ? (TGF-?) coreceptor essential for angiogenesis and vascular homeostasis. Although endoglin dysfunction contributes to numerous vascular conditions, the mechanism of endoglin action remains poorly understood. Here we report a novel mechanism in which endoglin and G?-interacting protein C-terminus-interacting protein (GIPC)-mediated trafficking of phosphatidylinositol 3-kinase (PI3K) regulates endothelial signaling and function. We demonstrate that endoglin interacts with the PI3K subunits p110? and p85 via GIPC to recruit and activate PI3K and Akt at the cell membrane. Opposing ligand-induced effects are observed in which TGF-?1 attenuates, whereas bone morphogenetic protein-9 enhances, endoglin/GIPC-mediated membrane scaffolding of PI3K and Akt to alter endothelial capillary tube stability in vitro. Moreover, we employ the first transgenic zebrafish model for endoglin to demonstrate that GIPC is a critical component of endoglin function during developmental angiogenesis in vivo. These studies define a novel non-Smad function for endoglin and GIPC in regulating endothelial cell function during angiogenesis.

    View details for DOI 10.1091/mbc.E11-12-0993

    View details for Web of Science ID 000306287400003

    View details for PubMedID 22593212

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