Sex differences in the time course and mechanisms of vascular and cardiac aging in mice: role of the smooth muscle cell mineralocorticoid receptor.

Aging is associated with heart and vascular dysfunction that contributes to cardiovascular disease (CVD) risk. Clinical data support a sexual dimorphism in the time course of aging-associated CVD. However, the mechanisms driving sex differences in cardiovascular aging and whether they can be modeled in mice has not been explored. Mineralocorticoid receptors (MR) regulate blood pressure and we previously demonstrated in male mice that MR expression increases in aging mouse vessels and smooth muscle cell-specific MR deletion (SMC-MR-KO) protects from cardiovascular aging. This study characterizes sex differences in murine cardiovascular aging and the associated sex-specific role of SMC-MR. Aortic stiffness, measured by pulse wave velocity, increased from 3 to 12 months of age in males but not until 18 months in females. The timing of the rise in aortic stiffening correlated with the timing of increased aortic MR expression and aortic stiffness did not increase with age in SMC-MR-KO mice of both sexes. Vascular fibrosis increased at 12 months in males and later at 18-months in females; however, fibrosis was attenuated by SMC-MR-KO in males only. In resistance vessels, angiotensin type 1 receptor (AT1R)-mediated vasoconstriction also increased at 12-months in males and 18-months in females. AngII-induced vasoconstriction was decreased in SMC-MR-KO only in males in association with decreased AT1R expression. Cardiac systolic function declined in males and females by 18-months of age, which was prevented by SMC-MR-KO specifically in females. Cardiac perivascular fibrosis increased with age in both sexes accompanied by sex-specific changes in the expression levels of MR-regulated pro-fibrotic genes.