Abstract

Single-cell Transcriptome and Epigenomic Reprogramming of Adult Cardiomyocyte-dedifferentiated Cardiac Progenitor Cells

Charles Wang, Director & Professor, Loma Linda University

It has been believed that mammalian adult cardiomyocytes (ACMs) are terminally differentiated and are unable to proliferate. Recently, using a bi-transgenic mouse model and an in vitro culture system, we demonstrated that adult mouse cardiomyoctyes were able to dedifferentiate into cardiac progenitor-like cells (CPCs). In addition, implantation of CPCs into infarcted mouse myocardium improves cardiac function with augmented left ventricular ejection fraction. However, little is known about the molecular basis of their intrinsic cellular plasticity. Here we integrate whole-genome single-cell transcriptome and comprehensive high-throughput arrays for relative methylation (CHARM)-based DNA methylation analyses to unravel the molecular mechanisms underlying the focused, spontaneous dedifferentiation of mouse ACMs which gave rise to CPCs. Compared to parental cardiomyocytes, dedifferentiated myocyte-derived CPCs display epigenomic reprogramming with many differentially-methylated regions, both hypermethylated and hypomethylated, across the entire genome. Correlated well with the methylome, our single-cell level transcriptomic data showed that the genes encoding cardiac structure and function proteins are remarkably down-regulated in CPCs, while those for cell cycle, proliferation, and stemness are significantly up-regulated. We observed an inverse correlation between global DNA methylation and transcriptomic gene expression. The overlapping genes that are differentially-expressed and differentially-methylated are members of signaling networks underlying the reversal of cardiac hypertrophy, loss of cardiac maturation, cell cycle reactivation, and metabolic changes in CPCs.  Our study demonstrates that the cellular plasticity of mammalian cardiomyocytes is orchestrated by epigenomic programming and transcriptomic alteration. Cardiac epigenome may be a target for promoting the unmet cardiac regeneration in injured hearts.