Attenuation of Mineralocorticoid Receptor Signaling Promotes Vascular Recovery from Hind Limb Ischemia in a Sex Specific Manner

Abstract

Peripheral arterial disease (PAD) is a growing concern affecting 8.5 million Americans annually and contributing to both fatal and non‐fatal cardiovascular ischemic events. Importantly, available evidence indicates that women experience higher rates of occlusion, reintervention, and mortality than males, however, mechanisms underlying these sex differences remain unclear. Recent evidence has revealed sex‐specific deleterious effects of mineralocorticoid receptor (MR) signaling in a variety of cardiovascular conditions including vascular inflammation and endothelial dysfunction, which have been implicated in PAD. Whether MR signaling differentially impairs microvascular adaptations in males and females following an ischemic insult, however, has not been examined. Accordingly, we evaluated the hypothesis that attenuation of MR signaling promotes microvascular compensation and perfusion recovery following hind limb ischemia (HLI) to a greater extent in females than in males involving enhanced capillary neovascularization and augmented outward remodeling of existing collaterals. Male and female C57BL/6J mice (10–12 weeks old) underwent unilateral femoral artery ligation and excision to induce HLI after implantation of pellets containing either placebo or the MR antagonist spironolactone (20mg/kg/day, sc). The contralateral leg underwent sham surgery with no ligation or excision. Hind limb perfusion was serially assessed for 28 days with laser Doppler imaging. At 28 days post occlusion, the hind limb vasculature was perfusion fixed following maximal dilation and perfused with bismuth for assessment of collateral morphology by micro‐CT imaging. These studies were complemented with immunohistochemistry and angiogenic assay experiments. Additional preliminary HLI experiments were conducted in male mice with endothelial cell‐specific MR (EC MR) deletion. Systemic inhibition of MR signaling enhanced recovery of hind limb perfusion in female, not male, mice. This effect of MR blockade was associated with greater outward collateral remodeling in females compared to males. Interestingly, spironolactone similarly increased skeletal muscle capillary density in both hind limbs of males and females consistent with impairment of VEGF‐stimulated capillary sprouting by the MR agonist aldosterone in an aortic angiogenesis assay. Finally, preliminary studies revealed enhanced recovery of hind limb perfusion in male mice with EC MR deletion and that EC MR deletion enhanced aortic capillary sprouting in vitro. Taken together, these data suggest that MR signaling limits the microvascular response to ischemia and that enhanced perfusion recovery following MR blockade in females involves greater collateral expansion compared to males. Significant vascular cell‐specificity of MR signaling underlying these responses may contribute to these sex differences and warrant further investigation.Support or Funding InformationFunded by HL136386, HL095590, and HL088105.