Ontogenic development of cardiomyocytes derived from transgene-free human induced pluripotent stem cells and its homology with human heart

Aim: Reprogramming of somatic cells utilizing viral free methods provide a remarkable method to generate human induced pluripotent stem cells (hiPSCs) for regenerative medicine. In this study, we evaluate developmental ontogeny of cardiomyocytes following induced differentiation of hiPSCs.

Main methods: Fibroblasts were reprogrammed with episomal vectors to generate hiPSC and were subsequently differentiated to cardiomyocytes. Ontogenic development of cardiomyocytes was studied by real-time PCR.

Key findings: Human iPSCs derived from episomal based vectors maintain classical pluripotency markers, generate teratomas and spontaneously differentiate into three germ layers in vitro. Cardiomyogenic induction of these hiPSCs efficiently generated cardiomyocytes. Ontogenic gene expression studies demonstrated that differentiation of cardiomyocytes was initiated by increased expression of mesodermal markers, followed by early cardiac committed markers, structural and ion channel genes. Furthermore, our correlation analysis of gene expression studies with human heart demonstrated that pivotal structural genes like cardiac troponin, actinin, myosin light chain maintained a high correlation with ion channel genes indicating coordinated activation of cardiac transcriptional machinery. Finally, microelectrode recordings show that these cardiomyocytes could respond aptly to pharmacologically active drugs. Cardiomyocytes showed a chronotropic response to isoproterenol, reduced Na(+) influx with quinidine, prolongation of beating rate corrected field potential duration (cFPD) with E-4031 and reduced beating frequency and shortened cFPD with verapamil.

Significance: Our study shows that viral free hiPSCs efficiently differentiate into cardiomyocytes with cardiac-specific molecular, structural, and functional properties that recapitulate developmental ontogeny of cardiogenesis. These results, coupled with the potential to generate patient-specific hiPSC lines hold great promise for the development of in vitro platform for drug pharmacogenomics; disease modeling and regenerative medicine.