Abstract P038: Cardiomyocyte Proliferating Chemicals: Activation of Proliferation of ESC/iPSC-Derived Cardiomyocytes

Abstract

Cardiomyocytes derived from embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are promising cell sources for cardiac regeneration. Previously, we established a novel systematic cardiovascular cell induction system with mouse ESCs and iPSCs. ESC/iPSC-derived cardiomyocytes rarely proliferate after differentiation, similar to neonatal and adult cardiomyocytes. Cardiomyocyte proliferation is highly restricted and the regulating machineries of proliferation and growth arrest of cardiomyocytes are long-standing mysteries of cell biology. In order to establish cardiac regenerative medicine, it is critical to dissect and manipulate the machineries involved. Here we devised a novel approach using small molecules in an attempt to unravel the mystery and to manipulate ESC/iPSC-derived cardiomyocyte proliferation. We screened a chemical library containing well-established kinase inhibitors with high content screen to enhance mouse ESC-derived cardiomyocyte proliferation, and identified two novel chemical groups, extracellular signal-regulated kinase activators and Ca2+/calmodulin-dependent protein kinase II inhibitors, and two previously reported chemical groups, glycogen synthase kinase-3 inhibitors and a p38 mitogen-activated protein kinase inhibitior. Each chemical increased actual cardiomyocyte cell numbers two- to three-fold compared to control. An optimal combination of these chemicals strongly enhanced proliferation of ESC-derived cardiomyocytes and ESCM number was reached up to 14-fold. Expanded cells retained various functional and structural features of cardiomyocytes. These chemicals are robustly effective on cardiomyocytes from various sources including human iPSCs. Efficient combination of stem cell and chemical biology demonstrated a novel molecular mechanism of cardiomyocyte proliferation and offered a critical technological basis for cardiac regeneration.