Minimal contribution of IPR2 in cardiac differentiation and derived ventricular-like myocytes from human embryonic stem cells.

Type 2 inositol 1,4,5-trisphosphate receptor (IPR2) regulates the intracellular Ca release from endoplasmic reticulum in human embryonic stem cells (hESCs), cardiovascular progenitor cells (CVPCs), and mammalian cardiomyocytes. However, the role of IPR2 in human cardiac development is unknown and its function in mammalian cardiomyocytes is controversial. hESC-derived cardiomyocytes have unique merits in disease modeling, cell therapy, and drug screening. Therefore, understanding the role of IPR2 in the generation and function of human cardiomyocytes would be valuable for the application of hESC-derived cardiomyocytes. In the current study, we investigated the role of IPR2 in the differentiation of hESCs to cardiomyocytes and in the hESC-derived cardiomyocytes. By using IPR2 knockout (IPR2KO) hESCs, we showed that IPR2KO did not affect the self-renewal of hESCs as well as the differentiation ability of hESCs into CVPCs and cardiomyocytes. Furthermore, we demonstrated the ventricular-like myocyte characteristics of hESC-derived cardiomyocytes. Under the α-adrenergic stimulation by phenylephrine (10 μmol/L), the amplitude and maximum rate of depolarization of action potential (AP) were slightly affected in the IPR2KO hESC-derived cardiomyocytes at differentiation day 90, whereas the other parameters of APs and the Ca transients did not show significant changes compared with these in the wide-type ones. These results demonstrate that IPR2 has minimal contribution to the differentiation and function of human cardiomyocytes derived from hESCs, thus provide the new knowledge to the function of IPR2 in the generation of human cardiac lineage cells and in the early cardiomyocytes.