Summary The immature characteristics and metabolic phenotypes of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) restrict their applications for disease modeling, drug discovery, and cell-based therapy. Leveraging on the metabolic shifts from glycolysis to fatty acid oxidation as CMs mature, a human hexokinase1-GFP metabolic reporter cell line (H7 HK1-GFP) was generated to facilitate the isolation of fetal or more matured hPSC-CMs. RNA sequencing of fetal versus more matured CMs uncovered a potential role of interferon-signaling pathway in regulating CM maturation. Indeed, IFN-γ-treated CMs resulted in an upregulation of the JAK-STAT pathway, which was found to be associated with increased expression of CM maturation genes, shift from MYH6 to MYH7 expression, and improved sarcomeric structure. Functionally, IFN-γ-treated CMs exhibited a more matured electrophysiological profile, such as increased calcium dynamics and action potential upstroke velocity, demonstrated through calcium imaging and MEA. Expectedly, the functional improvements were nullified with a JAK-STAT inhibitor, ruxolitinib.
Highlights • RNA-seq revealed upregulation of IFN-signaling pathways during CM maturation • IFN-γ-treated PSC-derived fetal CMs display increased MYH7:MYH6 ratio • IFN-γ-treated PSC-derived fetal CMs exhibited improved electrophysiological profile
In this article, Soh and colleagues utilize a metabolic reporter to identify a novel role of JAK-STAT signaling in hPSC-CM maturation. IFN-γ treatment activates the JAK-STAT pathway and upregulates STAT1 expression in hPSC-derived fetal CMs, thereby enhancing the expression of CM maturation genes including MYH7, which subsequently resulted in improved sarcomeric structure, and a relatively more matured electrophysiological profile in vitro.