[Tumor necrosis factor alpha regulates the proliferative activity and differentiated function of granulosa cells: in vitro study with a porcine model].

Ovarian folliculogenesis is a dynamic process during which follicles undergo growth and differentiation. It is now evident that various growth factors interact with FSH to modify follicular growth and function. In the present study, the effects of tumor necrosis factor alpha (TNF alpha) on the proliferative potential and steroidogenic ability of granulosa cells were examined in vitro as a function of follicular growth by using a porcine model. Porcine granulosa cells obtained from small (1-2mm), medium (3-5mm) and large (6-12 mm) follicles were cultured under serum-free conditions in the presence or absence of FSH (100 ng/ml) and IGF-1 (100 ng/ml), with or without various concentrations of TNF alpha. The proliferative activity of cultured granulosa cells was assessed by immunocytochemical techniques with a monoclonal antibody to proliferating cell nuclear antigen (PCNA) and by [3H]-thymidine uptake, while differentiated functions of granulosa cells were assessed by determining the ability to secrete progesterone and 17 beta-estradiol. The addition of FSH and IGF-I augmented the proliferative activity and steroidogenic ability of cultured granulosa cells. The increases in proliferative activity and steroidogenic ability caused by treatment with FSH and IGF-I were significantly reduced by the concomitant treatment with TNF alpha in culture of granulosa cells. The inhibitory effect of TNF alpha on the proliferative activity was prominent in small follicle granulosa cells, whereas the inhibitory effect of TNF alpha on estradiol secretion was very strong in large follicle granulosa cells. The inhibitory effect of TNF alpha on progesterone secretion was apparent regardless of the stage of follicular growth. These results suggest TNF alpha participation in regulating the proliferation and differentiation of granulosa cells. In appears that the biological action of TNF alpha on granulosa cells may shift from the inhibition of proliferative activity in immature follicles to the inhibition of differentiated function in mature follicles during the course of follicular growth.