Role of activin, inhibin and follistatin in the pathogenesis of bovine cystic ovarian disease

Abstract

Cystic ovarian disease (COD) is an important cause of infertility in dairy cattle. Although many researchers have focused their works on the endocrine changes related with this disease, there is evidence that intra-ovarian components play an important role in follicular persistence. Activin, inhibin, and follistatin participate as intraovarian regulatory molecules involved in follicular cell proliferation, differentiation, steroidogenesis, oocyte maturation and corpus luteum function. Given the importance of these factors in folliculogenesis, we examined the expression and immunolocalization of activin-inhibin-follistatin system in control ovaries under estrous synchronized, adrenocorticotropin hormone (ACTH)-induced heifers and spontaneous COD cows, as well as inhibin-B levels in serum and follicular fluid. We found an increased expression of βA-subunit corresponding to activin-A/inhibin-A; α-subunit corresponding to inhibin; and follistatin in granulosa cells of spontaneous and ACTH-induced follicular cysts by immunohistochemistry. In contrast, a diminished concentration of inhibin-B was found in the follicular fluid of spontaneous cysts. These results, together with other previously obtained, indicate that there exist an altered expression of components of the activin-inhibin-follistatin system that could lead to the imbalance between pro and anti-apoptotic factors, proliferation/apoptosis and steroidogenesis. The imbalance in such important factors and processes could be responsible for the follicular persistence and endocrine changes that contribute to the pathogenesis of the bovine COD.