Role of heme-oxygenase-1 in biology of cardiomyocytes derived from human induced pluripotent stem cells

Heme oxygenase-1 (HO-1, encoded byHMOX1) is a cytoprotective enzyme degradingheme into CO, $Fe^{2+}$, and biliverdin. HO-1 was demonstrated to affect cardiac differentiation of murinepluripotent stem cells (PSCs), regulate the metabolism of murine adult cardiomyocytes, and influenceregeneration of infarcted myocardium in mice. However, the enzyme’s effect on human cardiogenesisand human cardiomyocytes’ electromechanical properties has not been described so far. Thus, thisstudy aimed to investigate the role of HO-1 in the differentiation of human induced pluripotentstem cells (hiPSCs) into hiPSC-derived cardiomyocytes (hiPSC-CMs). hiPSCs were generated fromhuman fibroblasts and peripheral blood mononuclear cells using Sendai vectors and subjected toCRISPR/Cas9-mediatedHMOX1knock-out. After confirming lack of HO-1 expression on the proteinlevel, isogenic control and HO-1-deficient hiPSCs were differentiated into hiPSC-CMs. No differencesin differentiation efficiency and hiPSC-CMs metabolism were observed in both cell types. The globaltranscriptomic analysis revealed, on the other hand, alterations in electrophysiological pathways inhiPSC-CMs devoid of HO-1, which also demonstrated increased size. Functional consequences inchanges in expression of ion channels genes were then confirmed by patch-clamp analysis. To the bestof our knowledge, this is the first report demonstrating the link between HO-1 and electrophysiologyin human cardiomyocytes