A roadmap for the characterization of energy metabolism in human cardiomyocytes derived from induced pluripotent stem cells

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) are an increasingly employed model in cardiac research and drug discovery. A significant limitation with respect to clinical translation is their immature structural and functional phenotype. Cellular metabolism plays an integral role in determining phenotype but the metabolic profile of hiPSC-CM during maturation is poorly characterized. In this study we employ a combination of methods including extracellular flux and 13 C-glucose flux analyses to study the metabolic profile of hiPSC-CM over a 12 week maturation period. Results show a progressive remodeling of pathways involved in energy metabolism and substrate utilization. The oxidative capacity of hiPSC-CM and particularly their ability to utilize fatty acids increased with time. In parallel, relative glucose oxidation was reduced while glutamine oxidation was maintained at similar levels. Anaerobic glycolysis as assessed by lactate production was maintained throughout the 12 week period but with significant alterations in proximal glycolytic enzymes such as hexokinase and phosphofructokinase. We also observed a progressive maturation of mitochondrial oxidative capacity at comparable levels of mitochondrial content between timepoints. The time-dependent restructuring of the hiPSC-CM metabolic profile indicates their potential to overcome the lack of full maturation previously reported and enhance their applicability for pharmacological studies and cardiac disease modeling.