Localization and expression of follicle-stimulating hormone receptor gene in buffalo (Bubalus bubalis) pre-antral follicles.

Follicle-stimulating hormone (FSH) stimulates antral follicles to grow, but its role in earlier stages (pre-antral) of follicle development, if any, is obscure. Aim of this study was to study the expression of follicle-stimulating hormone receptor (FSHR) gene in different sizes of pre-antral follicles (PFs) (<150, 200, 250, 300, 350, 400 μm) and to find out an optimum dose of FSH for better growth, development and steroidogenesis of PFs in vitro. Buffalo ovaries were collected from a local abattoir, and PFs were isolated by mechanical method. A semi-quantitative RT-PCR amplification strategy was used for mRNA expression, while FSHR protein was localized by immunohistochemistry. Isolated pre-antral follicles (80-85 μm) were cultured in TCM-199 supplemented with 10% foetal bovine serum, 1% ITS and 30 ng/ml EGF served as control medium. Addition of three different doses of FSH (0.5, 1.0, 2.0 μg/ml) in control medium was considered as treatment groups. A single 2.184-kb receptor mRNA transcript was present in all sizes (<150-400 μm) of follicles. Follicle-stimulating hormone receptor was also localized immunohistochemically in granulosa cells of all sizes of follicles. Survival and growth rate of follicles significantly (p<0.05) increased following supplementation of FSH at a concentration of 1.0 μg/ml and the culture medium also showed a significantly (p<0.05) greater accumulation of oestradiol and progesterone. In conclusion, FSHR is expressed in all sizes of PFs and in vitro survival, growth and steroidogenesis of follicles are optimally stimulated by 1.0 μg/ml FSH. These findings demonstrate that FSH has an important role during the recruitment, growth and development of buffalo ovarian PFs.