<scp>HSP</scp> 90 Is Required for Meiotic Resumption and Spindle Formation in Porcine Oocytes

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone that is expressed in response to stress conditions. HSP90 has been found to be involved in the activation of proteins related to cell division and female reproduction. However, its specific role in porcine oocyte maturation, particularly in cytoskeletal formation, remains unclear. In this study, geldanamycin (GA) was used to inhibit HSP90 activity by binding to its adenosine triphosphate (ATP) binding site. Porcine oocytes surrounded by cumulus cells were cultured in TCM-199 medium for 44 h, with varying concentrations of GA (0.1, 0.5, 1 and 2 μM). It was observed that oocyte maturation significantly decreased when treated with a concentration of 0.5 μM or higher, leading to an increase in oocytes arrested at the germinal vesicle and metaphase I (MI) stage. The expression levels of Cyclin-dependent kinase 1, p-Aurora C (Thr198), p-AKT (Ser473) and p-PLK1 (Thr210) decreased during the MI stage, whereas Polo-like kinase 1 remained consistent with the control group. Additionally, abnormal spindle formation was increased, with abnormalities including aberrant poles, misaligned chromosomes and failure to reach the proximity of the cell membrane. Moreover, examination of mature oocytes at the metaphase II (MII) stage revealed that GA treatment induced a decrease in BCL-2 phosphorylation at the Ser70 site and an increase at the Thr56 site. This led to the release of Cytochrome c from the mitochondria and upregulation of Caspase 3 expression. In conclusion, HSP90 is essential for proper meiotic maturation in porcine oocytes by playing critical roles in meiotic resumption and spindle formation.