Abstract 19039: Type 1 and 3 Inositol 1,4,5-Trisphosphate Receptors in the Endothelium are Required for Angiogenesis during Embryonic Vascular Development
Intracellular calcium is a crucial signaling molecule in cardiomyocyte physiology and gene expression, however its function in cardiovascular development remains to be elucidated. Inositol 1, 4, 5-trisphosphate receptor (IP3R) is an intracellular calcium release channel located on the endo/sarcoplasmic reticulum and/or the nuclear membrane in various types of cells. We previously showed that three subtypes of IP3R (IP3R1, 2 and 3) were expressed from early stage of embryogenesis using in situ hybridization and immunohistochemistry, and that IP3R1 and 2 double knockout (DKO) mice exhibited defect of morphogenesis of atrioventricular endocardial cushion and ventricular wall although single knockout mice of each subtype grow normally. In addition the real-time PCR analysis with total RNA extracted from sorted cells showed that the expression sites of IP3R1 and 3 were partially overlapping in the early-stage embryonic blood vessels: IP3R1 was expressed dominantly in the CD31-positive yolk sac vascular cells, assumed as endothelial cells at embryonic day (E) 9.5; IP3R3 was expressed both in the CD31-positive and CD31-negative yolk sac vascular cells, assumed as endothelial and mural cells at E9.5, suggesting their redundant function in the endothelium during vascular development. These data led us to generate and analyze IP3R1 and 3 DKO (1/3 DKO) mice. 1/3 DKO mice died around E11.0, showing growth retardation. 1/3 DKO embryos exhibited defects in vasculature, including honeycomb appearance of yolk sac vessels, extra irregular branches of intersomitic vessels, narrowing of dorsal arteries and elongation defects of embryonic vessels in the labyrinth layers of the placenta at E9.25. The expression levels of the markers of angiogenesis, e.g. Angiopoietin-1, Semaphorin 3C/3E and Plexin D1 were markedly downregulated in 1/3DKO at E9.5 although the markers of vasculogenesis, including PECAM, Flk1 and VE-Cadherin, were expressed at comparable level to the wildtype. An IP3R inhibitor, 2-APB, significantly inhibited tube formation- and migration-activities of HUVEC in vitro. Our results suggest that the endothelial IP3R1 and 3 may play redundant roles for signaling pathways in the angiogenesis during embryonic and extraembryonic vascular development.
- © 2010 by American Heart Association, Inc.