Background: Granulosa cells (GCs) play key roles in oocyte maturation by providing required estradiol (E2). Since the presence of immature oocytes has been reported in cases with polycystic ovary syndrome (PCOS), in this study, the levels of mitochondrial membrane transporter proteins involved in E2 synthesis were determined. E2 concentration and parameters of oxidative status were also measured in follicular fluids of PCOS women.
Methods: Forty-three women with PCOS and 43 healthy women who were candidates for IVF procedure due to their husbands' infertility were enrolled in this case-control study. The gene expression and protein levels of mitochondrial translocator protein (TSPO) and voltage-dependent anion channel 1 (VDAC1) were determined in GCs using RT-qPCR and immunocytochemistry assay, respectively. E2 level was measured with electrochemiluminescence, whereas total cholesterol, total antioxidant capacity (TAC), total oxidant status (TOS), and malondialdehyde (MDA) were determined using colorimetric methods in follicular fluids. Data were analyzed using unpaired t-test or Mann-Whitney U test, and Spearman's correlation coefficient.
Results: VDAC1 and TSPO were significantly lower in mRNA (p<0.05) and protein levels (p<0.001) of PCOS patients. PCOS patients had lower cholesterol, estradiol, and TAC levels, and higher TOS and MDA contents. E2 level had direct correlation with VDAC1, TSPO, and TAC while it was negatively correlated with TOS, oxidative stress index (OSI), and MDA (p<0.001). Higher E2 levels were associated with higher numbers of high-quality oocytes and conceived embryos (p<0.001).
Conclusion: Decreased E2 levels and increased oxidative stress in the follicular fluid may be the cause of immature oocytes in PCOS cases.
Keywords: Estradiol; Granulosa cells; Oxidative stress; Polycystic ovary syndrome; TSPO protein; Voltage-dependent anion channel 1.
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