Effects of transforming growth factor β1 on steroidogenesis of feline granulosa cells cultured in vitro

Context Little is known about the hormonal regulation of feline ovarian granulosa cell proliferation and steroidogenesis. Aims To determine if transforming growth factor β1 (TGFB1), activin, epidermal growth factor (EGF), follicle stimulating hormone (FSH), luteinizing hormone (LH), melatonin, and insulin-like growth factor 1 (IGF1) regulate granulosa cell steroidogenesis and proliferation in cats, three experiments were conducted in winter season. Methods Granulosa cells were isolated and treated in vitro with various hormones in serum-free medium for 48 h after an initial 48 h plating in 10% fetal calf serum. Key results Treatment with IGF1 and FSH increased (P < 0.05) estradiol production by 2.3- and 1.33-fold, respectively. In contrast, TGFB1 blocked (P < 0.05) IGF1-induced estradiol production and inhibited FSH-induced estradiol production by 60%. Combined with FSH or FSH plus IGF1, TGFB1 inhibited (P < 0.05) cell proliferation, whereas TGFB1 increased progesterone production by 2.8-fold in the presence of FSH plus IGF1. EGF decreased (P < 0.05) FSH plus IGF1-induced estradiol production by 89% but did not affect progesterone production or cell numbers. Activin did not affect (P > 0.10) cell numbers or steroidogenesis in the presence of FSH plus IGF1. Melatonin and LH decreased (P < 0.05) estradiol production 53% and 59%, respectively, without affecting progesterone production or cell proliferation. Conclusions The present study has identified TGFB1 as a major regulator of feline ovarian function, in addition to EGF, IGF1, melatonin, LH and FSH. Implications These studies will provide useful information for future development of fertility control in feline species.