SUN-LB41 The Role of Androgen Receptors in Female Mouse X-Zone Loss During Aging and Pregnancy

Introduction: Sex differences are prevalent in the risk and manifestation of numerous human diseases as well as in the response to most therapeutic interventions. While marked sexual dimorphism is observed in the development, homeostasis and most diseases of the adrenal cortex, the impact of these differences on adrenal function remains poorly understood. Sex differences include the timing of adrenal fetal zone (X-zone) regression, which occurs during male mouse puberty but only after pregnancy or advanced age in females. The mechanisms driving regression, particularly in females, are unknown. A potential regulator of adrenal sexual dimorphism and X-zone regression is androgen exposure. Through adrenocortical-specific deletion of the androgen receptor (AR), we tested the hypothesis that androgen signaling is responsible for X-zone post-pubertal regression in male mice and post-pregnancy/aging related regression in female mice. Methods: Adrenocortical-targeted Ar deletion was accomplished by crossing heterozygous aldosterone synthase-Cre mice to mice with a floxed exon 2 of Ar (AR(ΔAdr)). Mice were sacrificed at 25 or 50 weeks of age and compared to AR(f/f) littermates (controls). Adrenals were processed for histology (H&E), immunofluorescence (IF) and whole adrenal mRNA RT-PCR to detect AR and X-zone specific markers Akr1c18 (20αHSD) and Pik3c2g. Results: In all mice, Ar mRNA expression was significantly decreased in AR(ΔAdr) mice compared to control littermates. As expected, 25 week control females had higher expression of Akr1c18 (6740-fold) and Pik3c2g (198-fold) compared to 25 week control males. 25 week AR(ΔAdr) males retained expression of Akr1c18 (20864-fold) and Pik3c2g (2802-fold) compared to controls, and also exhibited positive 20αHSD staining, confirming X-zone retention. 50 week control females exhibited histologic loss of the X-zone with negligible expression of Akr1c18 and Pik3c2g compared with 25 week control females. However, 50 week female AR(ΔAdr) mice exhibited a histologic X-zone retention and concomitant high expression of X-zone genes (Akr1c18 67-fold, Pik3c2g 75-fold) compared to female control littermates. Furthermore, 20αHSD IF demonstrated undetectable levels in controls and positive staining in AR(ΔAdr), indicating that age-associated X-zone loss may be AR-mediated. Post-pregnant 25 week control mice had ~99% lower expression of both X-zone markers compared to virgin female controls. Post-pregnant AR(ΔAdr) mice displayed higher expression of Akr1c18 (19-fold) and Pik3c2g (5-fold) compared to post-pregnant controls, though neither group had detectable 20αHSD by IF. Conclusion: Our findings indicate that AR signaling not only causes post-pubertal X-zone loss in males, but also plays a major role in the loss of the X-zone observed in aged female mice. Conversely, AR signaling may only play a minor role in X-zone regression following pregnancy.