De-differentiation and Proliferation of Artery Endothelial Cells Drive Coronary Collateral Development

Collateral arteries act as natural bypasses which re-route blood flow to ischemic regions and facilitate tissue regeneration. In an injured heart, neonatal artery endothelial cells orchestrate a systematic series of cellular events, which includes their outward migration, proliferation, and coalescence into fully functional collateral arteries. This process, called Artery Reassembly, aids complete cardiac regeneration in neonatal hearts, but is absent in adults. The reason for this age-dependent disparity in artery cell response is completely unknown. In this study, we investigated if regenerative potential of coronary arteries, like in cardiomyocytes, is dictated by their ability to de-differentiate. We performed single cell RNA sequencing of coronary endothelial cells and identified differences in molecular profiles of neonatal and adult endothelial cells. Neonates show significant increase in actively cycling artery cells that expressed prominent de-differentiation markers. Using both, in silico pathway analyses and in vivo experiments, we show that cell cycle re-entry of pre-existing artery cells, subsequent collateral artery formation and cardiac function is dependent on arterial VegfR2. This sub-population of de-differentiated and proliferating artery cells is absent in non-regenerative P7 or adult hearts. Together, our data indicate that adult artery endothelial cells fail to drive collateral artery development due to their limited ability to de-differentiate and proliferate.