Intramyocardial Sprouting Tip Cells Specify Coronary Arterialization

The elaborate patterning of coronary arteries critically supports the high metabolic activity of the beating heart. How coronary endothelial cells coordinate hierarchical vascular remodeling and achieve arteriovenous specification remains largely unknown. Understanding the molecular and cellular cues that pattern coronary arteries is crucial to develop innovative therapeutic strategies that restore functional perfusion within the ischemic heart. Single-cell transcriptomics were used to delineate heterogeneous transcriptional states of the developing and mature coronary endothelium with a focus on sprouting endothelium and arterial cell specification. We discovered that a tip-cell-to-artery specification mechanism drives arterialization of the intramyocardial plexus and endocardial tunnels throughout life. We also identified non-overlapping intramyocardial and subepicardial tip cell populations with differential gene expression profiles and regulatory pathways, suggesting that differential sprouting programs govern the formation and specification of the venous and arterial coronary plexus.