Effect of mechanical stretching stimulation on maturation of human iPS cell-derived cardiomyocytes co-cultured with human gingival fibroblasts

In the realm of regenerative medicine, despite the various techniques available for inducing the differentiation of induced pluripotent stem (iPS) cells into cardiomyocytes, there remains a need to enhance the maturation of the cardiomyocytes. This study aimed to improve the differentiation and subsequent maturation of iPS-derived cardiomyocytes (iPS-CMs) by incorporating mechanical stretching. Human iPS cells were co-cultured with human gingival fibroblasts (HGF) on a polydimethylsiloxane (PDMS) stretch chamber, where mechanical stretching stimulation was applied during the induction of cardiomyocyte differentiation. The maturation of iPS-CMs was assessed using qRT-PCR, immunocytochemistry, transmission electron microscopy, calcium imaging and contractility comparisons. Results indicated significantly elevated gene expression levels of cardiomyocyte markers (cTnT) and the mesodermal marker (Nkx2.5) in the stretch group compared to the control group. Fluorescent immunocytochemical staining revealed the presence of cardiac marker proteins (cTnT and MYL2) in both groups, with higher protein expression in the stretch group. Additionally, structural maturation of iPS-CMs in the stretch group was notably better than in the control group. A significant increase in the contractility and calcium cycle of iPS-CMs was observed in the stretch group. These findings demonstrate that mechanical stretching stimulation enhances the maturation of iPS-CMs co-cultured with HGF.