Effect of growth differentiation factor-9 (GDF-9) on the progression of buffalo follicles in vitrified-warmed ovarian tissues.

To improve the reproductive performance of water buffalo to level can satisfy our needs, the mechanisms controlling ovarian follicular growth and development should be thoroughly investigated. Therefore, in this study, the expressions of growth differentiation factor-9 (GDF-9) in buffalo ovaries were examined by immunohistochemistry, and the effects of GDF-9 treatment on follicle progression were investigated using a buffalo ovary organ culture system. Frozen-thawed buffalo ovarian follicles within slices of ovarian cortical tissue were cultured for 14 days in the presence or absence of GDF-9. After culture, ovarian slices were fixed, sectioned and stained. The follicles were morphologically analysed and counted. Expression pattern of GDF-9 was detected in oocytes from primordial follicles onwards, besides, also presented in granulosa cells. Moreover, GDF-9 was detected in mural granulosa cells and theca cells of pre-antral follicles. In antral follicles, cumulus cells and theca cells displayed positive expression of GDF-9. In corpora lutea, GDF-9 was expressed in both granulosa and theca lutein cells. After in vitro culture, there was no difference in the number of primordial follicles between cultured plus GDF-9 and cultured control that indicated the GDF-9 treatment has no effect on the primordial to primary follicle transition. GDF-9 treatment caused a significant decrease in the number of primary and secondary follicles compared with controls accompanied with a significant increase in pre-antral and antral follicles. These results suggest that a larger number of primary and secondary follicles were stimulated to progress to later developmental stages when treated with GDF-9. Vitrification/warming of buffalo ovarian tissue had a little remarkable effect, in contrast to culturing for 14 days, on the expression of GDF-9. In conclusion, treatment with GDF-9 was found to promote progression of primary follicle that could provide an alternative approach to stimulate early follicle development and to improve therapies for the most common infertility problem in buffaloes (ovarian inactivity).