Platelet C5aR1 mediates sex-specific ischemia-driven revascularization through estradiol-dependent CXCL4 release
BackgroundSex-specific differences in cardiovascular diseases remain incompletely understood at the molecular level. ObjectivesHere, we investigated the role of the platelet complement receptor C5aR1 as a sex-specific critical mediator of revascularization following hindlimb ischemia. MethodsIschemia-driven revascularization was analyzed in the hind limb ischemia (HLI) model using wild type (WT) and complement receptor-deficient male and female mice, and involved mechanisms were analyzed in platelets and megakaryocyte-shed platelets ex vivo. ResultsIn WT mice, ischemic tissue exhibited robust complement activation with C3b and C5a accumulation that correlated strongly with deposition of the anti-angiogenic factor CXCL4 (PF4). Mechanistically, C5a stimulation of platelets triggered CXCL4 secretion, and female animals with a platelet-specific deletion of C5aR1 (using PF4-Cre-C5aR1fl/fl mice) showed a significantly delayed revascularization. Female mice exhibited substantially lower platelet C5aR1 expression, and C5a-induced CXCL4 secretion was virtually abolished compared to male animals. The sex-specific difference in tissue CXCL4 deposition was not present any more in the absence of C5aR1 from platelets. We observed that megakaryocytes, which give rise to platelets, express estradiol receptors. Importantly, estradiol stimulation of megakaryocytes suppressed C5aR1 expression during pro-platelet formation, uncovering a hormone-dependent regulatory mechanism. ConclusionsThe here described estradiol-C5aR1-CXCL4 axis provides a molecular explanation for sex-specific differences in ischemic revascularization known from patient studies. Our findings establish a novel and unexpected mechanistic link between sex hormones, a complement-platelet crosstalk and the angiogenic response to ischemia with potential clinical implications for sex-specific personalized therapeutic strategies.