Lanlan Fang1, Hsun-Ming Chang, Jung-Chien Cheng, Peter C K Leung, Ying-Pu Sun. 1. Reproductive Medical Center (L.F., Y.-P.S.), The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China 450052; and Department of Obstetrics and Gynaecology (H.-M.C., J.-C.C., P.C.K.L.), Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4.
Abstract
CONTEXT: Regulation of progesterone production in granulosa cells is important for normal reproductive functions. Steroidogenic acute regulatory protein (StAR) is recognized as the key regulatory protein involved in the rate-limiting step of steroidogenesis. TGF-β1 protein is detected in human follicular fluid, and TGF-β1 and its receptors are expressed in human granulosa cells. However, the functional role of TGF-β1 in the regulation of StAR expression and progesterone production in human granulosa cells remains unknown. OBJECTIVE: Our objective was to investigate the effects of TGF-β1 on StAR expression and progesterone production in human granulosa cells. DESIGN AND SETTING: SVOG cells are human granulosa cells that were obtained from women undergoing in vitro fertilization and immortalized with SV40 large T antigen. SVOG cells were used to investigate the effects of TGF-β1 on StAR expression and progesterone production at an academic research center. MAIN OUTCOME MEASURES: Levels of mRNA and protein were examined by RT-qPCR and western blotting, respectively. The accumulation levels of progesterone were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: TGF-β1 treatment downregulated StAR expression and decreased progesterone production. The suppressive effects of TGF-β1 on StAR expression and progesterone production were abolished by the inhibition of TGF-β type I receptor. In addition, treatment with TGF-β1 activated the Smad2/3 and ERK1/2 signaling pathways. The inhibition of the Smad3 and ERK1/2 signaling pathways attenuated the TGF-β1-induced downregulation of StAR expression and progesterone production. CONCLUSION: TGF-β1 downregulated StAR expression and decreased progesterone production by activating the Smad3 and ERK1/2 signaling pathways in human granulosa cells.
CONTEXT: Regulation of progesterone production in granulosa cells is important for normal reproductive functions. Steroidogenic acute regulatory protein (StAR) is recognized as the key regulatory protein involved in the rate-limiting step of steroidogenesis. TGF-β1 protein is detected in human follicular fluid, and TGF-β1 and its receptors are expressed in human granulosa cells. However, the functional role of TGF-β1 in the regulation of StAR expression and progesterone production in human granulosa cells remains unknown. OBJECTIVE: Our objective was to investigate the effects of TGF-β1 on StAR expression and progesterone production in human granulosa cells. DESIGN AND SETTING: SVOG cells are human granulosa cells that were obtained from women undergoing in vitro fertilization and immortalized with SV40 large T antigen. SVOG cells were used to investigate the effects of TGF-β1 on StAR expression and progesterone production at an academic research center. MAIN OUTCOME MEASURES: Levels of mRNA and protein were examined by RT-qPCR and western blotting, respectively. The accumulation levels of progesterone were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: TGF-β1 treatment downregulated StAR expression and decreased progesterone production. The suppressive effects of TGF-β1 on StAR expression and progesterone production were abolished by the inhibition of TGF-β type I receptor. In addition, treatment with TGF-β1 activated the Smad2/3 and ERK1/2 signaling pathways. The inhibition of the Smad3 and ERK1/2 signaling pathways attenuated the TGF-β1-induced downregulation of StAR expression and progesterone production. CONCLUSION: TGF-β1 downregulated StAR expression and decreased progesterone production by activating the Smad3 and ERK1/2 signaling pathways in human granulosa cells.