Background
Ovulation is a tightly coordinated process in which the ovarian follicle undergoes rapid tissue remodelling to release a mature oocyte (1, 2). Intrafollicular signals control these morphological changes(1); however, despite its importance to fertility, the precise molecular mechanisms governing follicle rupture remain incompletely understood. This study utilised an ex vivo follicle culture model to visualise the ovulation process and investigate the roles of steroid receptor signalling, prostaglandin transport and mechanotransduction-associated pathways in ovulation.
Methods
Antral follicles were isolated from ovaries of 23–28-day-old mice and cultured ex vivo with follicle-stimulating hormone for 24 h, then with human chorionic gonadotropin to trigger ovulation, visualised 12–15 h later.
Pharmacological and genetic approaches investigated the progesterone receptor (PGR), glucocorticoid receptor (GR), prostaglandin transporter (PGT/SLCO2A1), and YAP-associated signalling. Each experiment measured 20–40 follicles per treatment. Ovulation rates were analysed using Fisher's exact test, and continuous variables using t-tests or ANOVA.
Results
Genetic ablation of PGR or inhibition with ulipristal acetate abolished ovulation (p < 0.0001), confirming the essential role of PGR signalling in follicle rupture. Interestingly, GR antagonism with CORT125281 reduced ovulation by ~40% (p = 0.003), indicating a previously unknown contributory role for GR signalling during ovulation.
Inhibition of PGT/SLCO2A1 reduced follicle rupture, with 100µM DIDS producing an 89% reduction in ovulation (p < 0.0001). Histological analysis revealed persistence of unruptured follicle morphology, while hyaluronan-binding protein staining remained detectable, suggesting prostaglandin transport regulates extracellular matrix remodelling rather than hyaluronan production.
Inhibition of YAP/TEAD signalling with Verteporfin (3 µM) or CA3 (1 µM) reduced ovulation by 85% (p < 0.0001) and 30% (p = 0.0276), respectively, indicating that mechanosensitive signalling plays a role in follicle rupture.
Conclusion
These findings demonstrate that ovulation requires coordinated steroid receptor signalling, prostaglandin transport and migration-associated cytoskeletal remodelling, identifying potential therapeutic targets for ovulatory disorders and contraception.