Androgen receptor is widely expressed in bovine placentomes and up-regulated during differentiation of bovine trophoblast giant cells

Abstract

ObjectivesIn cattle no biological role has been definitely identified for placental estrogens and progesterone. However, in the bovine trophoblast androgens may also be produced and have local effects. Thus, the aims of this study were to identify androgen receptor (AR) expressing cells and to monitor testosterone tissue concentrations in bovine placentomes throughout gestation. MethodsPlacental AR expression was characterized at the mRNA and protein level applying conventional and real-time RT-qPCR, western blot and immunohistochemistry. Testosterone was measured by radioimmunoassay. ResultsAR-mRNA was qualitatively detected from day 50 of gestation until term. Mean relative gene expression levels were constant between day 100 and late gestation. A slight non-significant increase was observed in the prepartal period. With immunohistochemistry distinct nuclear signals were predominantly observed in invasive trophoblast giant cells (TGC) from day 80 until term. In mature TGC of the trophoblast, immature TGC and uninucleated trophoblast cells, stromal cells of the chorionic villi, caruncular epithelial and stromal cells immunoreactive score values were low at early and midgestation but increased significantly (p < 0.01) during late gestation and remained high until parturition. With western blot in placentomal tissue a specific band of approximately 110 kDa was detected as it was the case in epididymis used as a positive control. Testosterone concentrations increased from 0.70 ± 0.29 pmol/g wet tissue between days 60–220 to 4.22 ± 1.29 pmol/g during late gestation (p < 0.001). DiscussionThe results are consistent with androgens as active products of bovine placental steroidogenesis. The substantial up-regulation of AR expression during TGC differentiation suggests that androgens may be related to this process.