Academic Appointments

All Publications

  • Modeling Secondary Iron Overload Cardiomyopathy with Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes. Cell reports Rhee, J. W., Yi, H. n., Thomas, D. n., Lam, C. K., Belbachir, N. n., Tian, L. n., Qin, X. n., Malisa, J. n., Lau, E. n., Paik, D. T., Kim, Y. n., Choi, B. S., Sayed, N. n., Sallam, K. n., Liao, R. n., Wu, J. C. 2020; 32 (2): 107886


    Excessive iron accumulation in the heart causes iron overload cardiomyopathy (IOC), which initially presents as diastolic dysfunction and arrhythmia but progresses to systolic dysfunction and end-stage heart failure when left untreated. However, the mechanisms of iron-related cardiac injury and how iron accumulates in human cardiomyocytes are not well understood. Herein, using human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs), we model IOC and screen for drugs to rescue the iron overload phenotypes. Human iPSC-CMs under excess iron exposure recapitulate early-stage IOC, including oxidative stress, arrhythmia, and contractile dysfunction. We find that iron-induced changes in calcium kinetics play a critical role in dysregulation of CM functions. We identify that ebselen, a selective divalent metal transporter 1 (DMT1) inhibitor and antioxidant, could prevent the observed iron overload phenotypes, supporting the role of DMT1 in iron uptake into the human myocardium. These results suggest that ebselen may be a potential preventive and therapeutic agent for treating patients with secondary iron overload.

    View details for DOI 10.1016/j.celrep.2020.107886

    View details for PubMedID 32668256

  • Levitating Cells to Sort the Fit and the Fat. Advanced biosystems Puluca, N. n., Durmus, N. G., Lee, S. n., Belbachir, N. n., Galdos, F. X., Ogut, M. G., Gupta, R. n., Hirano, K. I., Krane, M. n., Lange, R. n., Wu, J. C., Wu, S. M., Demirci, U. n. 2020: e1900300


    Density is a core material property and varies between different cell types, mainly based on differences in their lipid content. Sorting based on density enables various biomedical applications such as multi-omics in precision medicine and regenerative repair in medicine. However, a significant challenge is sorting cells of the same type based on density differences. Here, a new method for real-time monitoring and sorting of single cells based on their inherent levitation profiles driven by their lipid content is reported. As a model system, human-induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs) from a patient with neutral lipid storage disease (NLSD) due to loss of function of adipose triglyceride lipase (ATGL) resulting in abnormal lipid storage in cardiac muscle are used. This levitation-based strategy detects subpopulations within ATGL-deficient hiPSC-CMs with heterogenous lipid content, equilibrating at different levitation heights due to small density differences. In addition, sorting of these differentially levitating subpopulations are monitored in real time. Using this approach, sorted healthy and diseased hiPSC-CMs maintain viability and function. Pixel-tracking technologies show differences in contraction between NLSD and healthy hiPSC-CMs. Overall, this is a unique approach to separate diseased cell populations based on their intracellular lipid content that cannot be achieved using traditional flow cytometry techniques.

    View details for DOI 10.1002/adbi.201900300

    View details for PubMedID 32352239

  • Effects of Cryopreservation on Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Assessing Drug Safety Response Profiles. Stem cell reports Zhang, J. Z., Belbachir, N. n., Zhang, T. n., Liu, Y. n., Shrestha, R. n., Wu, J. C. 2020


    Burgeoning applications of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) in disease modeling, regenerative medicine, and drug screening have broadened the usage of hiPSC-CMs and entailed their long-term storage. Cryopreservation is the most common approach to store hiPSC-CMs. However, the effects of cryopreservation and recovery on hiPSC-CMs remain poorly understood. Here, we characterized the transcriptome, electro-mechanical function, and drug response of fresh hiPSC-CMs without cryopreservation and recovered hiPSC-CMs from cryopreservation. We found that recovered hiPSC-CMs showed upregulation of cell cycle genes, similar or reduced contractility, Ca2+ transients, and field potential duration. When subjected to treatment of drugs that affect electrophysiological properties, recovered hiPSC-CMs showed an altered drug response and enhanced propensity for drug-induced cardiac arrhythmic events. In conclusion, fresh and recovered hiPSC-CMs do not always show comparable molecular and physiological properties. When cryopreserved hiPSC-CMs are used for assessing drug-induced cardiac liabilities, the altered drug sensitivity needs to be considered.

    View details for DOI 10.1016/j.stemcr.2020.11.010

    View details for PubMedID 33338435

  • Identifying the Transcriptome Signature of Calcium Channel Blocker in Human iPSC-Derived Cardiomyocytes Lam, C., Tian Lei, Belbachir, N., Wnorowski, A., Shrestha, R., Ma Ning, Kitani, T., Rhee, J. W., Wu, J. C. LIPPINCOTT WILLIAMS & WILKINS. 2019
  • Identifying the Transcriptome Signatures of Calcium Channel Blockers in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes CIRCULATION RESEARCH Lam, C., Tian, L., Belbachir, N., Wnorowski, A., Shrestha, R., Ma, N., Kitani, T., Rhee, J., Wu, J. C. 2019; 125 (2): 212–22
  • RRAD mutation causes electrical and cytoskeletal defects in cardiomyocytes derived from a familial case of Brugada syndrome. European heart journal Belbachir, N., Portero, V., Al Sayed, Z. R., Gourraud, J., Dilasser, F., Jesel, L., Guo, H., Wu, H., Gaborit, N., Guilluy, C., Girardeau, A., Bonnaud, S., Simonet, F., Karakachoff, M., Pattier, S., Scott, C., Burel, S., Marionneau, C., Chariau, C., Gaignerie, A., David, L., Genin, E., Deleuze, J., Dina, C., Sauzeau, V., Loirand, G., Baro, I., Schott, J., Probst, V., Wu, J. C., Redon, R., Charpentier, F., Le Scouarnec, S. 2019


    AIMS: The Brugada syndrome (BrS) is an inherited cardiac disorder predisposing to ventricular arrhythmias. Despite considerable efforts, its genetic basis and cellular mechanisms remain largely unknown. The objective of this study was to identify a new susceptibility gene for BrS through familial investigation.METHODS AND RESULTS: Whole-exome sequencing performed in a three-generation pedigree with five affected members allowed the identification of one rare non-synonymous substitution (p.R211H) in RRAD, the gene encoding the RAD GTPase, carried by all affected members of the family. Three additional rare missense variants were found in 3/186 unrelated index cases. We detected higher levels of RRAD transcripts in subepicardium than in subendocardium in human heart, and in the right ventricle outflow tract compared to the other cardiac compartments in mice. The p.R211H variant was then subjected to electrophysiological and structural investigations in human cardiomyocytes derived from induced pluripotent stem cells (iPSC-CMs). Cardiomyocytes derived from induced pluripotent stem cells from two affected family members exhibited reduced action potential upstroke velocity, prolonged action potentials and increased incidence of early afterdepolarizations, with decreased Na+ peak current amplitude and increased Na+ persistent current amplitude, as well as abnormal distribution of actin and less focal adhesions, compared with intra-familial control iPSC-CMs Insertion of p.R211H-RRAD variant in control iPSCs by genome editing confirmed these results. In addition, iPSC-CMs from affected patients exhibited a decreased L-type Ca2+ current amplitude.CONCLUSION: This study identified a potential new BrS-susceptibility gene, RRAD. Cardiomyocytes derived from induced pluripotent stem cells expressing RRAD variant recapitulated single-cell electrophysiological features of BrS, including altered Na+ current, as well as cytoskeleton disturbances.

    View details for DOI 10.1093/eurheartj/ehz308

    View details for PubMedID 31114854

  • Identifying the Transcriptome Signatures of Calcium Channel Blockers in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes. Circulation research Lam, C. K., Tian, L. n., Belbachir, N. n., Shrestha, R. n., Ma, N. n., Kitani, T. n., Rhee, J. W., Wnorowski, A. n., Wu, J. C. 2019


    Calcium channel blockers (CCBs) are an important class of drugs in managing cardiovascular diseases. Patients usually rely on these medications for the remainder of their lives after diagnosis. Although the acute pharmacological actions of CCBs in the hearts are well-defined, little is known about the drug-specific effects on human cardiomyocyte transcriptomes and physiological alterations after long-term exposure.This study aimed to simulate chronic CCB treatment and to examine both the functional and transcriptomic changes in human cardiomyocytes.We differentiated cardiomyocytes and generated engineered heart tissues from three human induced pluripotent stem cell (iPSC) lines and exposed them to four different CCBs-nifedipine, amlodipine, diltiazem, and verapamil-at their physiological serum concentrations for two weeks. Without inducing cell death and damage to myofilament structure, CCBs elicited line-specific inhibition on calcium kinetics and contractility. While all four CCBs exerted similar inhibition on calcium kinetics, verapamil applied the strongest inhibition on cardiomyocyte contractile function. By profiling cardiomyocyte transcriptome after CCB treatment, we identified little overlap in their transcriptome signatures. Verapamil is the only inhibitor that reduced the expression of contraction-related genes, such as myosin heavy chain and troponin I, consistent with its depressive effects on contractile function. The reduction of these contraction related genes may also explain the responsiveness of HCM patients to verapamil in managing left ventricular outflow tract obstruction.This is the first study to identify the transcriptome signatures of different CCBs in human cardiomyocytes. The distinct gene expression patterns suggest that although the four inhibitors act on the same target, they may have distinct effects on normal cardiac cell physiology.

    View details for PubMedID 31079550