Human embryonic stem cells (hESCs) is a potential unlimited ex vivo source of ventricular (V) cardiomyocytes (CMs), but hESC-VCMs and their engineered tissues display immature traits. In adult VCMs, sarcolemmal (sarc) and mitochondrial (mito) ATP-sensitive potassium (K ATP) channels play crucial roles in excitability and cardioprotection. In this study, we aim to investigate the biological roles and use of sarcK ATP and mitoK ATP in hESC-VCM. We showed that SarcI K, ATP in single hESC-VCMs was dormant under baseline conditions, but became markedly activated by cyanide (CN) or the known opener P1075 with a current density that was ∼8-fold smaller than adult; These effects were reversible upon washout or the addition of GLI or HMR1098. Interestingly, sarcI K, ATP displayed a ∼3-fold increase after treatment with hypoxia (5% O 2). MitoI K, ATP was absent in hESC-VCMs. However, the thyroid hormone T3 up-regulated mitoI K, ATP, conferring diazoxide protective effect on T3-treated hESC-VCMs. When assessed using a multi-cellular engineered 3D ventricular cardiac micro-tissue (hvCMT) system, T3 substantially enhanced the developed tension by 3-folds. Diazoxide also attenuated the decrease in contractility induced by simulated ischemia (1% O 2). We conclude that hypoxia and T3 enhance the functionality of hESC-VCMs and their engineered tissues by selectively acting on sarc and mitoI K, ATP.
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