Genetic Background Defines the Regulation of Postnatal Cardiac Growth by 17 beta-Estradiol Through a beta-Catenin Mechanism

Estrogen regulates several biological processes in health and disease. Specifically, estrogen exerts antihypertrophic effects in the diseased heart. However, its role in the healthy heart remains elusive. Our initial aim was to identify the effects of 17 beta-estradiol (E2) on cardiac morphology and global gene expression in the healthy mouse heart. Two-month-old C57BL/6J mice were ovariectomized and treated with E2 or vehicle for 3 months. We report that E2 induced physiological hypertrophic growth in the healthy C57BL/6J mouse heart characterized by an increase in nuclear beta-catenin. Hypothesizing that beta-catenin mediates these effects of E2, we employed a model of cardiac beta-catenin deletion. Our surprising finding is that E2 had the opposite effects in wild-type littermates, which were actually on the C57BL/6N background. Notably, E2 exerted no significant effect in hearts of mice with depleted beta-catenin. We further demonstrate an E2-dependent increase in glycogen synthase kinase 3 beta (GSK3 beta) phosphorylation and endosomal markers in C57BL/6J but not C57BL/6N mice. Together, these findings indicate an E2-driven inhibition of GSK3 beta and consequent activation of beta-catenin in C57BL/6J mice, whereas the opposite occurs in C57BL/6N mice. In conclusion, E2 exerts divergent effects on postnatal cardiac growth in mice with distinct genetic backgrounds modulating members of the GSK3 beta/beta-catenin cascade.