Peritoneal Fluid Modulates Redox Balance and RNA Integrity in Mouse Oocytes: Insights into Endometriosis-Related Oxidative Stress

Reactive oxygen species (ROS) are vital for oocyte development, yet the redox state of peritoneal fluid may differ between health and disease. This study investigates the effects of peritoneal fluid from women with and without endometriosis on mouse oocytes' redox status and RNA oxidation. Peritoneal fluid samples were collected during laparoscopy from women enrolled in an ethically approved case-control study. Stimulated C57BL6 mouse germinal vesicle oocytes were microinjected with RNA transcribed from a Grx1-roGFP2 construct and imaged to assess redox changes. Further oocytes were incubated in standard media, H₂O₂, or 20% peritoneal fluid, fixed, and immunostained for 8-OHG to evaluate RNA oxidative damage. Oocytes exposed to endometriosis-affected peritoneal fluid showed significantly less redox reduction (mean change 0.07, <i>p</i> < 0.001) compared to fluid from unaffected women (mean change 0.17, <i>p</i> < 0.001), suggesting impaired antioxidant capacity. Those treated with fluid from women without endometriosis showed a more significant reduction (mean ratio change 0.17, <i>p</i> < 0.001). RNA damage was higher in oocytes incubated in fluid from women with infertility compared to pelvic pain (<i>p</i> < 0.001). These findings suggest an altered oxidative environment of peritoneal fluid in endometriosis may contribute to impaired oocyte quality, highlighting a potential mechanism of infertility in affected women.