Abstract Body: Introduction:
Myocardial Infarction (MI) is the number one cause of death in the United States. The heart undergoes severe trauma during MI, which results in the death of cardiac cells. Although the cardiac tissue cannot regenerate on its own, regenerative medicine approaches involving cell transplantation have been shown to improve the cardiac function. Among different cell types, human induced pluripotent stem cell-derived cardiac progenitor cells (hiPSCs) have been shown to have the ability to proliferate and differentiate into cardiac lineage cells and therefore, are a promising source for myocardial repair. Here, we characterized two distinct populations of hiPSC-CPCs and assessed their differentiation potential.

Methods:
We compared hiPSC-CPCs differentiated using the small molecule, isoxazole-9 (ISX-9), ISX9-hiPSC-CPCs with the commercially acquired iCell hiPSC-CPCs (Fujifilm Cellular Dynamics Int.). The expression of different cardiac lineage markers were assessed via immunostaining, qPCR and flow cytometry. Furthermore, we assessed the proliferation of the cells using immunostaining and XTT assays. We also evaluated their in vitro differentiation to cardiomyocytes, via immunostaining and qPCR analysis.

Results:
Our studies showed similar expression of different cardiac progentior markers (Nkx2.5, GATA4, KFL-4, ISL-1, BRY-T, MESP-1, MYH-6, CTnT) in the two hiPSC-CPC populations. However, while the iCell hiPSC-CPCs predominantly expressed the cell surface marker KDR, the ISX-9-hiPSC-CPCs predominantly expressed SSEA-1. The iCell-hiPSC-CPCs showed higher proliferation rates when compared to the ISX-9-hiPSC-CPCs. However, >95% of both the cell populations expressed the proliferation marker, ki67. Finally, the while both the CPC populations could differentiate into cardiomyocytes (cTNT⁺), only a few of these differentiated cardiomyocytes showed spontaneous contractility in vitro.

Conclusion:
In our study, we have compared and characterized two distinct populations of hiPSC-CPCs to identify a promising candidate for myocardial regeneration therapies.