Human pluripotent stem cell (hPSC)-derived progenies (ChIP-Seq)

The in vitro culture of human cardiac progenitor cells remains a major challenge in biomedicine. The molecular identity of hPSC-derived cardiac progenies and mechanisms controlling their proliferation and differentiation remain unclear. Here, we show that chromatin remodeling and WNT pathway modulation by chemical inhibitors (IQ-1 and CHIR, respectively) synergistically enables stabilization of human cardiac progenitors (SCPs), in a process of transcriptional uncoupling. SCPs are characterized by ISL1pos/KI-67pos/NKX2-5neg expression and are maintained in a quiescent state in the presence of the inhibitors. Upon compound removal, cell autonomous NKX2-5 upregulation hallmarks the recoupling to the cardiomyogenic program, whilst directed differentiation generates endothelial and smooth muscle cells. Chip-sequencing revealed a narrowly defined open chromatin state in SCPs and, when combined with single cell transcriptome analyses, showed a yet unreported Cardiac Neural Crest Cells (CNCCs) footprint. Enforced expression of the oncogene c-MYC could notably not overcome SCPs proliferative quiescence but disrupted the cell autonomous cardiomyogenic potential instead. In contrast, Retinoic Acid (RA) stimulates SCPs proliferation and further supports cells’ phenotypic homogeneity. We consequently show that our in vitro established treatment with IQ1 can also retain ISL1pos cardiac progenies in vivo in a dose and stage specific manner during zebrafish heart development. Due to its chemically defined and reversible nature, our approach provides an unprecedented opportunity to dissect the key mechanisms in cardiac progenitor cell biology, providing a new tool for the advancement of human heart regeneration.