Expression of mitochondrial transcription factor A in granulosa cells: implications for oocyte maturation and in vitro fertilization outcomes

Objective: In vitro fertilization-embryo transfer (IVF-ET) is a widely used treatment for infertility, with oocyte maturation and quality having a significant impact on oocyte fertilization, embryo development, and fetal growth. Mitochondrial transcription factor A (TFAM) is essential for maintaining the mitochondrial oxidative respiratory chain and supplying energy for oocyte development, fertilization, and embryonic development. In this study, we aimed to examine TFAM expression in women undergoing IVF-ET and assess its impact on the IVF outcomes.

Methods: We recruited 85 women who underwent IVF-ET treatment for infertility. On the date of egg collection, granulosa cells were extracted from the clear follicular fluid of the first mature egg using ultrasound-guided needle aspiration. The collected granulosa cells served three purposes: (1) detecting TFAM gene expression in granulosa cells via immunocytochemistry, (2) determining TFAM mRNA expression using reverse transcription-PCR (RT-PCR), and (3) measuring TFAM protein expression through western blotting.

Result: Based on the results, we found that TFAM was localized and expressed in the cytoplasm of granulosa cells, whereas no expression was detected in the nucleus. Granulosa cells exhibited a linear correlation between TFAM mRNA and TFAM protein expression. The study participants were divided into three groups using the ternary method based on relative TFAM mRNA expression thresholds of 33% and 76%: the low-expression group (n = 30), the moderate-expression group (n = 27), and the high-expression group (n = 28). When compared to the other two groups, the moderate expression group exhibited a significantly higher egg utilization rate, 2 pronucleus rate, fertilization rate, and clinical pregnancy rate (P < 0.05).

Conclusion: TFAM was detected in the cytoplasm of human ovarian granulosa cells. Women with moderate TFAM expression demonstrate enhanced outcomes in IVF.