Nonhuman primate (NHP) models are more predictive than rodent models for developing induced pluripotent stem cell (iPSC)-based cell therapy, but robust and reproducible NHP iPSC-cardiomyocyte differentiation protocols are lacking for cardiomyopathies research. We developed a method to differentiate integration-free rhesus macaque iPSCs (RhiPSCs) into cardiomyocytes with >85% purity in 10 days, using fully chemically defined conditions. To enable visualization of intracellular calcium flux in beating cardiomyocytes, we used CRISPR/Cas9 to stably knock-in genetically encoded calcium indicators at the rhesus AAVS1 safe harbor locus. Rhesus cardiomyocytes derived by our stepwise differentiation method express signature cardiac markers and show normal electrochemical coupling. They are responsive to cardiorelevant drugs and can be successfully engrafted in a mouse myocardial infarction model. Our approach provides a powerful tool for generation of NHP iPSC-derived cardiomyocytes amenable to utilization in basic research and preclinical studies, including in vivo tissue regeneration models and drug screening.

Techniques that enable longitudinal tracking of cell fate after myocardial delivery are imperative for optimizing the efficacy of cell-based cardiac therapies. However, these approaches have been underutilized in preclinical models and clinical trials, and there is considerable demand for site-specific strategies achieving long-term expression of reporter genes compatible with safe noninvasive imaging. In this study, the rhesus sodium/iodide symporter (NIS) gene was incorporated into rhesus macaque induced pluripotent stem cells (RhiPSCs) via CRISPR/Cas9. Cardiomyocytes derived from NIS-RhiPSCs (NIS-RhiPSC-CMs) exhibited overall similar morphological and electrophysiological characteristics compared to parental control RhiPSC-CMs at baseline and with exposure to physiological levels of sodium iodide. Mice were injected intramyocardially with 2 million NIS-RhiPSC-CMs immediately following myocardial infarction, and serial positron emission tomography/computed tomography was performed with 18 F-tetrafluoroborate to monitor transplanted cells in vivo. NIS-RhiPSC-CMs could be detected until study conclusion at 8 to 10 weeks postinjection. This NIS-based molecular imaging platform, with optimal safety and sensitivity characteristics, is primed for translation into large-animal preclinical models and clinical trials.

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