Abstract 310: Vascular Endothelial Growth Factor and Endothelial Nitric Oxide Synthase-mediated Regulation of Cardiomyocyte Proliferation During Development in Humans and Mice
Our previous studies in early mouse embryonic development (E8.2) showing that vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) are expressed in embryonic endothelial cells, but not in embryonic cardiomyocytes, together with the findings by others indicating that NO is required for cardiomyocyte proliferation in mice, led us to investigate the relevancy of the VEGF/eNOS signaling pathway during cardiovascular development. First, wild type and NOS3 knockout mouse embryos between E8.0 and E17.0 were stained with antibodies against smooth muscle α-actin, phospho-histone H3 (PH3), VEGFR2 and PECAM, markers of cardiomyocytes, proliferating, progenitor and endothelial cells, respectively. Our confocal analysis showed hearts of E8.0 NOS3 nulls develop normally. However, E8.5 and E9.5 NOS3 nulls have reduced cardiomyocyte proliferation and impaired heart development. As consequence, hearts of E17 NOS3 nulls were approximately 20% smaller compared to wildtype hearts. To translate our findings to humans, we stained human heart specimens with antibodies against VEGFR2, eNOS, PH3 and sarcomeric α-actinin. Confocal analyses showed for the first time that VEGFR2 is highly expressed in the perinuclear region of human cardiomyocytes of a young donor. They also showed a correlation between eNOS expression and cardiomyocyte proliferation in humans. Consequently, we developed an in vitro three-dimensional co-culture model of human endothelial cells, cardiomyocytes and fibroblasts: “human cardiac tissue spheroids” (HCTSs). Our data showed that laminin and collagen type IV synthesis is increased in VEGF-treated HCTSs generated using CMs from an older donor compared to untreated cultures, suggesting a role for VEGF and eNOS in postnatal human heart development. In conclusion, our data showed that VEGF and eNOS play a similar role in mediating cardiomyocytes proliferation and heart regeneration in both mice and humans. Current studies are focusing on evaluating molecular targets of the VEGF/eNOS signalling pathway in human proliferating cardiomyocytes, which may have significant therapeutical impact for stem cell differentiation, and prevention of cardiovascular complications such as myocardial infarction.
Author Disclosures: C. Gentile: None. C.Y. Chuang: None. C.J. Drake: None. M.J. Davies: None.
- © 2015 by American Heart Association, Inc.