Abstract P3104: Sex Differences In Vasodilation In Embryonic Coronary Arteries

Abstract

Sex differences exist in circulatory system and the onset of cardiovascular diseases. These differences have been thought to be due to the vasoprotective effects of estrogen. However, there are also sex differences at the early stages of life, such as the survival rate of extremely preterm infants. The mechanisms in which those sex differences are formed at first remain to be elucidated. Therefore, we analyzed the mechanism of sex differences using fetal mouse hearts. In this study, embryonic day 17.5 mice were used to understand sex differences in cardiovascular system just before they are born. First, for morpho-functional analysis of coronary arteries, hearts were removed from embryonic day 17.5 mice, and angiography was performed using nano-particle ink. The ink was injected from the aorta at a constant pressure to visualize the morphology of coronary arteries. We found a significant sex difference in coronary artery diameters. Male coronary arteries were larger under physiological conditions, on the other hand, female coronary arteries were more dilated in the presence of the NO-donor NOC7 and the ROCK inhibitor Y27632. In addition, the same tendency was observed in sections of mouse hearts at embryonic day 17.5. These findings suggest that female’s coronary arteries are more contractile than males. Next, embryonic day 17.5 mouse hearts were dissociated, then sorted with FACS to obtain endothelial cells for bulk RNA-seq and single-cell RNA-seq. Cells were clustered based on the expression of 8 sex-differential genes to identify the sex of each cell. In line with the result of coronary visualization, Gene Set Enrichment Analysis showed the gene set of smooth muscle cell contraction was upregulated in males. Furthermore, cell-cell communication analysis showed that male endothelin signals were modestly stronger in endothelial cells and smooth muscle cells. These data support our previous observation that male left coronary arteries have a larger diameter but are less reactive to vasodilators, because they may have greater contractile function. In conclusion, this study suggests that functional and morphological sex differences already exist at embryonic day 17.5.