All Publications

  • Purification of Pluripotent Stem Cell-Derived Cardiomyocytes Using CRISPR/Cas9-Mediated Integration of Fluorescent Reporters. Methods in molecular biology (Clifton, N.J.) Galdos, F. X., Darsha, A. K., Paige, S. L., Wu, S. M. 2021; 2158: 223–40

    Abstract

    Human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes have become critically important for the detailed study of cardiac development, disease modeling, and drug screening. However, directed differentiation of hiPSCs into cardiomyocytes often results in mixed populations of cardiomyocytes and other cell types, which may confound experiments that require pure populations of cardiomyocytes. Here, we detail the use of a CRISPR/Cas9 genome editing strategy to develop cardiomyocyte-specific reporters that allow for the isolation of hiPSC-derived cardiomyocytes and chamber-specific myocytes. Moreover, we describe a cardiac differentiation protocol to derive cardiomyocytes from hiPSCs, as well as a strategy to use fluorescence-activated cell sorting to isolate pure populations of fluorescently labeled cardiomyocytes for downstream applications.

    View details for DOI 10.1007/978-1-0716-0668-1_17

    View details for PubMedID 32857377

  • Intrinsic Endocardial Defects Contribute to Hypoplastic Left Heart Syndrome. Cell stem cell Miao, Y., Tian, L., Martin, M., Paige, S. L., Galdos, F. X., Li, J., Klein, A., Zhang, H., Ma, N., Wei, Y., Stewart, M., Lee, S., Moonen, J., Zhang, B., Grossfeld, P., Mital, S., Chitayat, D., Wu, J. C., Rabinovitch, M., Nelson, T. J., Nie, S., Wu, S. M., Gu, M. 2020

    Abstract

    Hypoplastic left heart syndrome (HLHS) is a complex congenital heart disease characterized by abnormalities in the left ventricle, associated valves, and ascending aorta. Studies have shown intrinsic myocardial defects but do not sufficiently explain developmental defects in the endocardial-derived cardiac valve, septum, and vasculature. Here, we identify a developmentally impaired endocardial population in HLHS through single-cell RNA profiling of hiPSC-derived endocardium and human fetal heart tissue with an underdeveloped left ventricle. Intrinsic endocardial defects contribute to abnormal endothelial-to-mesenchymal transition, NOTCH signaling, and extracellular matrix organization, key factors in valve formation. Endocardial abnormalities cause reduced cardiomyocyte proliferation and maturation by disrupting fibronectin-integrin signaling, consistent with recently described de novo HLHS mutations associated with abnormal endocardial gene and fibronectin regulation. Together, these results reveal a critical role for endocardium in HLHS etiology and provide a rationale for considering endocardial function in regenerative strategies.

    View details for DOI 10.1016/j.stem.2020.07.015

    View details for PubMedID 32810435

  • Wnt Activation and Reduced Cell-Cell Contact Synergistically Induce Massive Expansion of Functional Human iPSC-Derived Cardiomyocytes. Cell stem cell Buikema, J. W., Lee, S., Goodyer, W. R., Maas, R. G., Chirikian, O., Li, G., Miao, Y., Paige, S. L., Lee, D., Wu, H., Paik, D. T., Rhee, S., Tian, L., Galdos, F. X., Puluca, N., Beyersdorf, B., Hu, J., Beck, A., Venkamatran, S., Swami, S., Wijnker, P., Schuldt, M., Dorsch, L. M., van Mil, A., Red-Horse, K., Wu, J. Y., Geisen, C., Hesse, M., Serpooshan, V., Jovinge, S., Fleischmann, B. K., Doevendans, P. A., van der Velden, J., Garcia, K. C., Wu, J. C., Sluijter, J. P., Wu, S. M. 2020; 27 (1): 50–63.e5

    Abstract

    Modulating signaling pathways including Wnt and Hippo can induce cardiomyocyte proliferation in vivo. Applying these signaling modulators to human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) in vitro can expand CMs modestly (<5-fold). Here, we demonstrate massive expansion of hiPSC-CMs in vitro (i.e., 100- to 250-fold) by glycogen synthase kinase-3β (GSK-3β) inhibition using CHIR99021 and concurrent removal of cell-cell contact. We show that GSK-3β inhibition suppresses CM maturation, while contact removal prevents CMs from cell cycle exit. Remarkably, contact removal enabled 10 to 25 times greater expansion beyond GSK-3β inhibition alone. Mechanistically, persistent CM proliferation required both LEF/TCF activity and AKT phosphorylation but was independent from yes-associated protein (YAP) signaling. Engineered heart tissues from expanded hiPSC-CMs showed comparable contractility to those from unexpanded hiPSC-CMs, demonstrating uncompromised cellular functionality after expansion. In summary, we uncovered a molecular interplay that enables massive hiPSC-CM expansion for large-scale drug screening and tissue engineering applications.

    View details for DOI 10.1016/j.stem.2020.06.001

    View details for PubMedID 32619518

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

    Abstract

    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

  • Single-Cell Delineation of Who's on First and Second Heart Fields During Development CIRCULATION RESEARCH Galdos, F. X., Wu, S. M. 2019; 125 (4): 411–13

    View details for DOI 10.1161/CIRCRESAHA.119.315576

    View details for Web of Science ID 000478066400010

  • Single-Cell Delineation of Who's on First and Second Heart Fields During Development. Circulation research Galdos, F. X., Wu, S. M. 2019; 125 (4): 411–13

    View details for DOI 10.1161/CIRCRESAHA.119.315576

    View details for PubMedID 31518166

  • Apolipoprotein E is a pancreatic extracellular factor that maintains mature β-cell gene expression. PloS one Mahmoud, A. I., Galdos, F. X., Dinan, K. A., Jedrychowski, M. P., Davis, J. C., Vujic, A., Rachmin, I., Shigley, C., Pancoast, J. R., Lee, S., Hollister-Lock, J., MacGillivray, C. M., Gygi, S. P., Melton, D. A., Weir, G. C., Lee, R. T. 2018; 13 (10): e0204595

    Abstract

    The in vivo microenvironment of tissues provides myriad unique signals to cells. Thus, following isolation, many cell types change in culture, often preserving some but not all of their in vivo characteristics in culture. At least some of the in vivo microenvironment may be mimicked by providing specific cues to cultured cells. Here, we show that after isolation and during maintenance in culture, adherent rat islets reduce expression of key β-cell transcription factors necessary for β-cell function and that soluble pancreatic decellularized matrix (DCM) can enhance β-cell gene expression. Following chromatographic fractionation of pancreatic DCM, we performed proteomics to identify soluble factors that can maintain β-cell stability and function. We identified Apolipoprotein E (ApoE) as an extracellular protein that significantly increased the expression of key β-cell genes. The ApoE effect on beta cells was mediated at least in part through the JAK/STAT signaling pathway. Together, these results reveal a role for ApoE as an extracellular factor that can maintain the mature β-cell gene expression profile.

    View details for DOI 10.1371/journal.pone.0204595

    View details for PubMedID 30303984

    View details for PubMedCentralID PMC6179231

  • Cardiac Regeneration Lessons From Development CIRCULATION RESEARCH Galdos, F. X., Guo, Y., Paige, S. L., VanDusen, N. J., Wu, S. M., Pu, W. T. 2017; 120 (6): 941-959

    Abstract

    Palliative surgery for congenital heart disease has allowed patients with previously lethal heart malformations to survive and, in most cases, to thrive. However, these procedures often place pressure and volume loads on the heart, and over time, these chronic loads can cause heart failure. Current therapeutic options for initial surgery and chronic heart failure that results from failed palliation are limited, in part, by the mammalian heart's low inherent capacity to form new cardiomyocytes. Surmounting the heart regeneration barrier would transform the treatment of congenital, as well as acquired, heart disease and likewise would enable development of personalized, in vitro cardiac disease models. Although these remain distant goals, studies of heart development are illuminating the path forward and suggest unique opportunities for heart regeneration, particularly in fetal and neonatal periods. Here, we review major lessons from heart development that inform current and future studies directed at enhancing cardiac regeneration.

    View details for DOI 10.1161/CIRCRESAHA.116.309040

    View details for Web of Science ID 000397330700007

    View details for PubMedID 28302741

  • Nkx2.5+ Cardiomyoblasts Contribute to Cardiomyogenesis in the Neonatal Heart. Scientific reports Serpooshan, V., Liu, Y. H., Buikema, J. W., Galdos, F. X., Chirikian, O., Paige, S., Venkatraman, S., Kumar, A., Rawnsley, D. R., Huang, X., Pijnappels, D. A., Wu, S. M. 2017; 7 (1): 12590

    Abstract

    During normal lifespan, the mammalian heart undergoes limited renewal of cardiomyocytes. While the exact mechanism for this renewal remains unclear, two possibilities have been proposed: differentiated myocyte replication and progenitor/immature cell differentiation. This study aimed to characterize a population of cardiomyocyte precursors in the neonatal heart and to determine their requirement for cardiac development. By tracking the expression of an embryonic Nkx2.5 cardiac enhancer, we identified cardiomyoblasts capable of differentiation into striated cardiomyocytes in vitro. Genome-wide expression profile of neonatal Nkx2.5+ cardiomyoblasts showed the absence of sarcomeric gene and the presence of cardiac transcription factors. To determine the lineage contribution of the Nkx2.5+ cardiomyoblasts, we generated a doxycycline suppressible Cre transgenic mouse under the regulation of the Nkx2.5 enhancer and showed that neonatal Nkx2.5+ cardiomyoblasts mature into cardiomyocytes in vivo. Ablation of neonatal cardiomyoblasts resulted in ventricular hypertrophy and dilation, supporting a functional requirement of the Nkx2.5+ cardiomyoblasts. This study provides direct lineage tracing evidence that a cardiomyoblast population contributes to cardiogenesis in the neonatal heart. The cell population identified here may serve as a promising therapeutic for pediatric cardiac regeneration.

    View details for PubMedID 28974782