OR25-1 Bilateral and Unilateral Malformations of Male Reproductive Tracts in Mice with Androgen Receptor Gene Deletion in the Mesenchyme

Abstract

Abstract Congenital unilateral defects of male reproductive tracts have been documented in men, suggesting the potential left-right asymmetry in male reproductive tract development. However, classic textbooks of endocrinology have been teaching us that the development of the paired male reproductive tract is governed by the universal action of the androgen receptor (Ar). During sexual differentiation, testis-derived androgens activate the Ar to promote the stabilization of the bilateral Wolffian ducts, the progenitor for the male reproductive tract. The Wolffian ducts then differentiate into the paired male reproductive tract organs, which include the epididymes, vas deferentes, and seminal vesicles. The Ar is expressed both in the epithelium and mesenchyme of the male reproductive tract during fetal development. Landmark tissue recombinant studies and the observation of normal morphology in the epithelium-specific Ar knockout mouse all support the notion that Ar action in the mesenchyme dictates the morphogenesis of the male reproductive tract. However, no genetic study has been performed to investigate the consequence of the loss of mesenchymal Ar on male reproductive tract development. To test the functional significance of the mesenchymal Ar, we designed a mesenchyme-specific Ar knockout mouse model (ARcKO) to ablate Ar specifically in the mesenchyme prior to the initiation of sexual differentiation. We performed immunohistochemistry of AR to confirm that Ar expression was absent in the mesenchyme while epithelial Ar remained intact in this ARcKO model. Based on the widely accepted notion that mesenchymal Ar regulates epithelial morphogenesis of the male reproductive tract, we expected to see abnormal patterning of the male reproductive tract. Indeed, the epididymis lost its characteristic coiling and became cystic. However, 40% of the 23 collected ARcKO males displayed these abnormalities on both horns; 43% and 17% displayed these abnormal phenotype solely on the left and right horn, respectively. This surprising observation might result from asynchronous activities of Cre on the left and right horns. However, when the Cre was crossed with a reporter (tdTomato), we observed comparable reporter expression on both horns at the onset of sexual differentiation of reproductive tracts. These observations suggest that the developmental programs in the morphogenesis of the left and right male reproductive tracts are asymmetrical and there could be a compensation mechanism for the loss of mesenchymal AR. We are currently in the process of comparing the left and the right horns in Ar knockout male mice to determine any biased signaling. Taken together, our study provides a unique model for not only studying congenital defects of male reproductive tracts but also for investigating the potential asymmetry in the masculinization program. Presentation: Monday, June 13, 2022 11:00 a.m. - 11:15 a.m.