Follicle-Stimulating Hormone and Transforming Growth Factor ��1 Regulation of Mitochondrial Biogenesis in Rat Ovarian Granulosa Cells

• Main Authors: Chi-ling Chiang, 江季霖
• Other Authors: Jiuan-Jiuan Hwang
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/35471052744372354963

碩士 === 國立陽明大學 === 生理學研究所 === 96 === Pituitary follicle-stimulating hormone (FSH) is the dominant regulator that stimulates steroidogenesis in ovarian granulosa cells, and transforming growth factor ��1 (TGF��1) enhances FSH action. The initial step of steroidogenesis, conversion of cholesterol to pregnenolone is catalyzed by mitochondrial cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc). Also, P450scc enzyme catalysis requires NADPH from pentose phosphate pathway. Therefore, this study was aimed to investigate if the FSH and TGF��1-stimulated steroidogenic activity correlates with mitochondrial bioactivity in rat ovarian granulosa cells. This includes the study of mitochondrial biogenesis, and cellular localization of P450scc in relation to mitochondrial oxidative activity in rat granulosa cells. Interestingly, we observed that TGF��1�bFSH increased the level of mitochondrial DNA (mtDNA) as indicated by the increase of mitochondrial NADH dehydrogenase (ND1). Additionally, TGF��1�bFSH increased the level of mitochondrial proteins encoded by mtDNA (cytochrome c oxidase subunit 1, COX1) and nuclear DNA (cytochrome c, Cyt c). Furthermore, TGF��1�bFSH upregulated a master regulator of mitochondrial biogenesis, PGC-1��. Together, these results suggest TGF��1 and FSH may stimulate mitochondrial biogenesis in rat ovarian granulosa cells. We next investigated the cellular localization of P450scc enzyme and its relation to mitochondrial oxidative activity in rat ovarian granulosa cells. Using confocal microscopy, we found that FSH+TGF��1 treatment increased P450scc immunostaining activity, and the immunostaining is well colocalized with the MitoTracker Red CMXRos staining activity. This suggests that mitochondrial steroidogenic activity may coincide with mitochondrial oxidative activity. In conclusion, our present study suggests (1) TGF��1 enhanced FSH-stimulated steroidogenesis in rat ovarian granulosa cells may partly be mediated through TGF��1-induced mitochondrial biogenesis, and (2) the steroidogenic activity may likely initiate at mitochondria with well oxidative activity.