Androgen Receptors in the Human Oocyte

Objective: Androgens play a critical role in female reproduction. Two major receptors, the classical androgen receptor (AR)and solute carrier family 39 member 9 (SLC39A9), regulate androgen function in animal studies. Mouse AR knockout studies show impaired follicular development, fewer ovulated oocytes, and diminished fertilization rates. Zebrafish SLC39A9 knockout studies show impaired oocyte germinal vesicle break down, meiotic resumption, and early embryogenesis. However, the presence of these receptors in human oocytes has not been studied. The purpose of this study is to investigate the presence and localization of AR and SLC39A9 in human oocytes. Design: Laboratory study Materials and Methods: Discarded deidentified oocytes were obtained with consent from participants undergoing in vitro fertilization, as approved by the Old Dominion University Institutional Review Board. Oocytes were fixed in 4% paraformaldehyde, incubated with primary and labeled secondary antibodies, and mounted on slides using mounting medium with DAPI. Oocytes were imaged using the BioTek Cytation C10 Confocal Imaging Reader. Human granulosa cells and sperm that were bound to the zona pellucida were used as both negative and positive controls since previous studies have demonstrated the presence of AR and SLC39A9 on these cells. Results: A total of 60 oocytes were stained from 19 different participants with a mean age of 34.1 years (range 22 – 42). Of the 33 oocytes stained for SLC39A9, 100% displayed SLC39A9 in the cytoplasm. Of the 17 MII oocytes stained for SLC39A9, 6 (35.3%) displayed SLC39A9 in the polar body. AR staining was performed on 24 oocytes, with 100% displaying AR in the cytoplasm. Of the 9 MII oocytes stained for AR, only 1 (11.1%) displayed AR in the polar body. Conclusions: SLC39A9 and AR are both present in the cytoplasm of human oocytes at the GV, M1, and M2 stages of maturity, without polarity to the polar body or nucleus. This is expected for AR, which is typically located in the cytoplasm when not bound with androgens. However, SLC39A9 is a transmembrane protein and typically found on the plasma membrane, and not commonly within the cytoplasm. Ongoing studies focus on the subcellular localization of each protein, with the goal of providing insight into the function of oocyte AR and SLC39A9 in human fertility.