Sex- and estrogen-dependent regulation of a miRNA network in the healthy and hypertrophied heart

Background: In pressure overload, profibrotic gene expression and cardiac fibrosis are more pronounced in males than in females. Sex-specific and estrogen-dependent regulation of microRNAs (miRNAs), such as miR-21, may be a potential mechanism leading to sex differences in fibrosis. Objectives: To analyze the influence of sex, estrogen, and estrogen receptor beta (ER beta) on the expression of miR-21 and to identify additional miRNAs potentially involved in sex-specific pressure overload-induced cardiac remodeling. Methods: The sex-specific regulation of fibrosis-related miRNAs was analyzed in male and female wild type and ER beta-deficient mice after transverse aortic constriction (TAC), in rat fibroblasts, and in a cardiomyocyte-like cell line. Results: We report the sex-specific expression of functionally-related miR-21, -24, -27a, -27b, 106a, -106b and the regulation of their expression by estrogen in a sex-specific manner. These effects were abolished in ER beta-deficient mice. We demonstrate the presence of common functional target sites for these miRNAs on three repressors of the mitogen-activated protein kinase signaling pathway, i.e. Rasa1, Rasa2 and Spry1, which may all lead to cardiac fibrosis. As expected, transfection with miRNA mimics targeting these repressors induced ERK1/2 phosphorylation. Conclusions: Estrogen regulates a network of miRNAs in a sex-specific manner via ER beta. Our data suggest that the sex-specific expression of these miRNAs may be related to sex differences in fibrosis after pressure overload. (C) 2013 Elsevier Ireland Ltd. All rights reserved.