Abstract 079: Estrogen Receptor beta Regulation Of miRNA Expression In The Heart - A Hint For Sex Differences In Hypertrophy

Sex differences (SD) in cardiovascular diseases are described and have been attributed to the effects of sex hormones, such as estrogen (E2). Our previous studies in a mouse model of pressure overload revealed SD in fibrosis and apoptosis related genes that were abolished in estrogen receptor β deficient (ERβ-/-) mice. Other studies focus on miRNA regulation by E2, but little is known about sex-specific regulation of miRNAs in heart diseases. We hypothesize that E2 and ERβ are regulators of miRNA expression in the heart potentially contributing to the molecular mechanism of SD observed in cardiovascular diseases. This project aims to identify SD in the expression of miRNAs in a 9-week transverse aortic constriction (TAC) model and the possible role of E2 and ERβ in their regulation in the heart. A Targetscan analysis of 80 sex-specific dysregulated genes in hypertrophy allowed identifying 157 different miRNAs that could target them. Based on their expression in the heart we selected 60 miRNAs for quantification by qRT-PCR. In WT mice, 23 miRNAs showed SD in their expression in hypertrophy, all of them showing a higher expression in males than in females. All these significant SD were abolished in ERβ-/- mice. A direct comparison of some of these miRNAs in WT and ERβ-/- female animals identified nine miRNAs significantly higher expressed in the knock-out animals (let-7e, miR-106b, miR-130a, miR-133a, miR-20a, miR-24, miR-27b, miR-29a and miR-378). In vitro studies performed using a female cardiomyocyte cell line (AC16) showed a down-regulation of eight of these miRNAs after a 48h treatment with E2, being the exception miR-133a. The latter showed however a down-regulation after 48h treatment with an ERβ specific agonist, as well as let-7e, miR-106b, miR-130a, miR-20a, miR-24, miR-27b and miR-29a. The effect of treatment with ERα was only visible as a down-regulation of miR-24, miR-29a and miR-378. The potential of these miRNAs having targets in the same pathway and acting in a synergistic way is still under investigation. ERβ is for the first time identified as a major regulator of miRNA expression in the heart. It may play an important role in determining SD in cardiac hypertrophy, being responsible for the inhibition of miRNA expression in the female heart.