Mullerian-inhibiting substance inhibits cytochrome P450 aromatase activity in human granulosa lutein cell culture

Objective: To investigate the effects of Mullerian-inhibiting substance (MIS) on cytochrome P450 aromatase(CYP19) gene expression in cultured human granulosa lutein cells (GLC). Design: In vitro primary cell culture study. Setting: Academic research laboratory and hospital-based fertility center. Patient(s): Eight, normo-ovulatory patients undergoing IVF procedures due to male factor or tubal infertility. Intervention(s): Serum and follicular fluid (FF) collected and stored at -80 degrees C until assayed. Granulosa lutein cells were harvested from follicular aspirates obtained during oocyte retrieval and cultured for 7 days with media in the presence or absence of MIS (10 ng/mL) or FSH 0.2 IU/mL. Main Outcome Measure(s): Serum and FF levels of E-2 and MIS, and E-2 production by GLC in culture. Levels of CYP19 mRNA in cultured GLC were determined by quantitative polymerase chain reaction (PCR) and CYP19 protein by Western blot. Statistical comparison used ANOVA and post hoc Tukey tests. Result(s): Follicle-stimulating hormone significantly increased E-2; production in cultured GLC compared with control. The increase in E, production is associated with higher levels of CYP19 mRNA and protein in GLC. The presence (if MIS significantly inhibited FSH-induced E-2 production, with concomitant reduction in CYP19mRNA and protein levels. Conclusion(s): Mullerian-inhibiting substance inhibits FSH augmentation of CYP19 enzyme activity and CYP19 gene expression in GLC. These findings may help to explain the association of high MIS levels and low FF E-2 levels reported in women with polycystic ovary syndrome (PCOS).