Abstract 8: Reprogramming of Adult Mammalian Cardiomyocytes Towards Proliferation and Regeneration Through Comparative Analyses of Epicardial and Myocardial Cells

Abstract

Heart development and regeneration require an elegant balance of cell proliferation and differentiation. In both adult zebrafish and neonatal mouse cardiac regeneration, new cardiomyocytes are shown to originate from pre-existing cardiomyocytes through de-differentiation of mature cells to the immature progenitor cell state, with developmental gene program reactivation and cell cycle reentry. Interestingly, after adult mammalian cardiac injury, both cardiac muscle cells and the epicardial cells that envelope the heart reinitiate developmental gene programs. However, adult epicardial cells are able to proliferate following injury but adult cardiomyocytes are not capable. We investigated the genetic circuitry of mouse epicardial cells and myocardial cells in different developmental stages and in response to injury. Such comparative analyses revealed a group of ~50 candidate genes that may be responsible for the permanent cell cycle arrest of cardiomyocytes. We generated adenoviruses that express these candidate genes individually, and demonstrated that the mixed viral pool possessed a robust activity to promote proliferation of adult mouse cardiomyocytes. Our comparative approach and functional screens may lead to identification of the dormant genetic circuitry in adult mammalian heart that can be reactivated to drive robust cardiomyocyte proliferation and regeneration.