Non-cardiomyocytes influence the electrophysiological maturation of human embryonic stem cell-derived cardiomyocytes during differentiation.

Various types of cardiomyocytes undergo changes in automaticity and electrical properties during fetal heart development. Human embryonic stem cell-derived cardiomyocytes (hESC-CMs), like fetal cardiomyocytes, are electrophysiologically immature and exhibit automaticity. We used hESC-CMs to investigate developmental changes in mechanisms of automaticity and to determine whether electrophysiological maturation is driven by an intrinsic developmental clock and/or is regulated by interactions with non-cardiomyocytes in embryoid bodies (EBs). We isolated pure populations of hESC-CMs from EBs by lentivirus-engineered Puromycin resistance at various stages of differentiation. Using pharmacological agents, calcium (Ca2+) imaging, and intracellular recording techniques, we found that intracellular Ca2+-cycling mechanisms developed early and contributed to dominant automaticity throughout hESC-CM differentiation. Sarcolemmal ion channels evolved later upon further differentiation within EBs and played an increasin...