Endocardium Minimally Contributes to Coronary Endothelium in the Embryonic Ventricular Free Walls

Abstract

Rationale: There is persistent uncertainty regarding the developmental origins of coronary vessels, with 2 principal sources suggested as ventricular endocardium or sinus venosus (SV). These 2 proposed origins implicate fundamentally distinct mechanisms of vessel formation. Resolution of this controversy is critical for deciphering the programs that result in the formation of coronary vessels and has implications for research on therapeutic angiogenesis. Objective: To resolve the controversy over the developmental origin of coronary vessels. Methods and Results: We first generated nuclear factor of activated T cells (Nfatc1)-Cre and Nfatc1-Dre lineage tracers for endocardium labeling. We found that Nfatc1 recombinases also label a significant portion of SV endothelial cells in addition to endocardium. Therefore, restricted endocardial lineage tracing requires a specific marker that distinguishes endocardium from SV. By single-cell gene expression analysis, we identified a novel endocardial gene natriuretic peptide receptor 3 (Npr3). Npr3 is expressed in the entirety of the endocardium but not in the SV. Genetic lineage tracing based on Npr3-CreER showed that endocardium contributes to a minority of coronary vessels in the free walls of embryonic heart. Intersectional genetic lineage tracing experiments demonstrated that endocardium minimally contributes to coronary endothelium in the embryonic ventricular free walls. Conclusions: Our study suggested that SV, but not endocardium, is the major origin for coronary endothelium in the embryonic ventricular free walls. This work thus resolves the recent controversy over the developmental origin of coronary endothelium, providing the basis for studying coronary vessel formation and regeneration after injury.

Preexisting endothelial cells mediate cardiac neovascularization after injury

“…Elucidating the sources for neovascularization after cardiac injury would provide impor- of the Col1a2 gene, following endogenous Col1a2 by the self-cleaving peptide 2A sequence. For the Pdgfra-DreER allele, a cDNA encoding DreER T2 recombinase was inserted after the translational stop codon of the Pdgfra gene, as previously described (48). All mice were maintained on an ICR/C57BL6/J-mixed background.…”

Towards Consensus on Coronary Vessel Development

“…In this issue of Circulation Research, Zhang et al 14 report on their study that further clarifies the origins of mammalian coronary ECs. In this elegant study, Zhang et al 14 used engineered mouse lines to genetically label ventricular endocardial or sinus venosus cells in the embryonic mouse heart to determine the source of coronary arterial ECs.…”

“…The recent studies by Zhou and colleagues 13,14 on the origins of coronary ECs have, in addition to using state-of-the-art genetic, imaging, and molecular techniques, have also provided detailed quantification in their lineage tracings. This is essential for determining the relative contributions of different embryonic sources to different parts of the coronary vascular system.…”

Analysis of the Role of Crim1 in Heart Development

“…Zhang and colleagues have confirmed, by employing the use of multiple transgenic mouse lines, that the sinus venosus is indeed a major contributor to myocardial endothelial cells (Zhang, Pu et al 2016). Tian and colleagues have suggested that subepicardial cells that originate from the sinus venosus give rise to both arterial and venous endothelial cells (Tian, Hu et al 2013).…”

“…A small population of these cells, by de-differentiation, also form coronary artery endothelial cells (Red-Horse, ), though Wu and colleagues suggest that the major source for coronary arterial endothelial cells appears to be the endocardium (Wu, Zhang et al 2012). However, it has most recently been confirmed in an elegant study that employed genetic labelling and lineage tracing using a number of transgenic mouse lines that a large population of intramyocardial endothelial cells derives from the sinus venosus in the developing mouse heart, and that the endocardium contributes only minimally to coronary arterial endothelial cells (Zhang, Pu et al 2016).…”