Sex-specific regulation of collagen I and III expression by 17-Estradiol in cardiac fibroblasts: role of estrogen receptors

Aims Sex differences in cardiac fibrosis point to the regulatory role of 17-Estradiol (E2) in cardiac fibroblasts (CF). We, therefore, asked whether male and female CF in rodent and human models are differentially susceptible to E2, and whether this is related to sex-specific activation of estrogen receptor alpha (ER) and beta (ER). Methods and results In female rat CF (rCF), 24h E2-treatment (10(-8)M) led to a significant down-regulation of collagen I and III expression, whereas both collagens were up-regulated in male rCF. E2-induced sex-specific collagen regulation was also detected in human CF, indicating that this regulation is conserved across species. Using specific ER- and ER-agonists (10(-7)M) for 24h, we identified ER as repressive and ER as inducing factor in female and male rCF, respectively. In addition, E2-induced ER phosphorylation at Ser118 only in female rCF, whereas Ser105 phosphorylation of ER was exclusively found in male rCF. Further, in female rCF we found both ER bound to the collagen I and III promoters using chromatin immunoprecipitation assays. In contrast, in male rCF only ER bound to both promoters. In engineered connective tissues (ECT) from rCF, collagen I and III mRNA were down-regulated in female ECT and up-regulated in male ECT by E2. This was accompanied by an impaired condensation of female ECT, whereas male ECT showed an increased condensation and stiffness upon E2-treatment, analysed by rheological measurements. Finally, we confirmed the E2-effect on both collagens in an in vivo mouse model with ovariectomy for E2 depletion, E2 substitution, and pressure overload by transverse aortic constriction. Conclusion The mechanism underlying the sex-specific regulation of collagen I and III in the heart appears to involve E2-mediated differential ER and ER signaling in CFs.