Gene expression and localization of 20α-hydroxysteroid dehydrogenase (HSD) in reproductive tissues during early pregnancy of cattle

The enzyme 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSD) catalyzes the conversion of progesterone to its inactive form, 20a-hydroxyprogesterone, and this enzyme has an important role in the regulation of luteal function in mammals. It has previously been determined that the 20 alpha-HSD gene is primarily expressed by large luteal cells during the late stage of the estrous cycle. In the present study, the amounts of mRNA were determined in cultured cells of the corpus luteum (CL) cells. The localization of 20 alpha-HSD was also determined in ovaries, placenta, and endometrium during early pregnancy. The amount of 20 alpha-HSD mRNA in cultured luteal cells increased with time and by treatment with the luteolysis agent prostaglandin F-2 alpha (PGF(2)alpha). Immunofluorescence assays detected increased protein in cultured luteal cells. The 20 alpha-HSD mRNA and protein were present in the ovaries, placenta, and endometrium on Days 30, 60, and 90 of pregnancy. In particular, gene expression was much greater in the ovary than in the placenta and endometrium. Immuno-histochemical analysis indicated that bovine 20 alpha-HSD was primarily localized in ovarian large luteal cells, placental cytotrophoblast villus, and glandular epithelial cells of the endometrium during early pregnancy. Furthermore, in situ analyses demonstrated colocalization of 20 alpha-HSD mRNA and protein. Taken together, results of the present study indicate that 20 alpha-HSD mRNA and protein are co-localized in large luteal cells, the placenta, and the endometrium during early pregnancy, suggesting that 20 alpha-HSD regulates mechanisms involved in the maintenance of early pregnancy. (C) 2014 Elsevier B.V. All rights reserved.