Abstract
During mouse heart development, ventricular endocardial cells give rise to the coronary arteries by angiogenesis. Myocardially-derived vascular endothelial growth factor-a (Vegfa) regulates embryonic coronary angiogenesis through vascular endothelial growth factor-receptor 2 (Vegfr2) expressed in the endocardium. In this study, we investigated the role of endocardially-produced soluble Vegfr1 (sVegfr1) in the coronary angiogenesis. We deleted sVegfr1 in the endocardium of the developing mouse heart and found that this deletion resulted in a precocious formation of coronary plexuses. Using an ex vivo coronary angiogenesis assay, we showed that the Vegfr1-null ventricular endocardial cells underwent excessive angiogenesis and generated extensive endothelial tubular networks. We also revealed by qPCR analysis that expression of genes involved in the Vegf-Notch pathway was augmented in the Vegfr1-null hearts. We further showed that inhibition of Notch signaling blocked the formation of coronary plexuses by the ventricular endocardial cells. These results establish that Vegfr1 produced in the endocardium negatively regulates embryonic coronary angiogenesis, possibly by limiting the Vegf-Notch signaling.
Highlights
The embryonic heart consists of the endocardium, myocardium and epicardium
Vegfr1 Produced in the Endocardium is Required for Normal Coronary Plexus Formation
We have recently shown that the myocardial vascular endothelial growth factor-a (Vegfa) to endocardial vascular endothelial growth factor-receptor 2 (Vegfr2) signaling is essential for embryonic coronary angiogenesis by the progenitor cells within the endocardium to form the coronary arteries [33]
Summary
The embryonic heart consists of the endocardium, myocardium and epicardium. The endocardium is the inner epithelial cell layer of the heart and the epicardium is the outer epithelial layer; in between is the myocardium consisting of the cardiomyocytes. The progenitor cells within the epicardium differentiate into the coronary vascular smooth muscle cells through epithelial to mesenchymal transition [9,10,11,12,13,14]. Different from the epicardium, the endocardium is derived from the vascular progenitor cells within the cardiogenic mesoderm [18,19,20,21]. These progenitor cells undergo vasculogenesis to form an endocardial tube that separates the inner surface of the myocardium from the primitive heart chamber [22]
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