ZnT 9 Involvement in Estradiol-Modulated Zinc Homeostasis of the Human Follicular Microenvironment

Female subfertility has been a growing concern for reproductive health. Assisted reproductive technologies make pregnancy possible, but the outcome rate is still suboptimal. Zinc is an essential factor for fertility and development. Zinc levels in follicular fluids were measured by electrochemical method, and we found that zinc in the follicular fluids was related to high-quality embryo rate (R = 0.39, p = 0.01). Basal estradiol levels and estradiol levels on the day of HCG injection were negatively correlated with zinc concentrations in the follicular fluid (R =  - 0.53, p < 0.001; R =  - 0.32, p < 0.05), and estradiol promoted ZnT 9 protein expression in cumulus granulosa cells in vitro and in vivo. When the zinc level was at 3.63-3.85 μg/mL, follicular fluid samples had the highest SOD activity. Therefore, zinc played an important role in improving oocyte development by increasing antioxidant capacity. Our results suggested that estradiol affected zinc homeostasis in follicles by controlling the expression of ZnT 9, which in turn influenced the potential of oocytes to develop into good-quality embryos. This study to provide tangible improvements to patient outcomes will make it a focus of both scientific and translational efforts in the future.