Abstract
In vitro maturation (IVM) of oocytes remains suboptimal due to oxidative stress and disrupted cumulus-oocyte communication. Oocyte-derived factors (ODFs) are key mediators of this crosstalk and crucial for oocyte competence. Here, we provide systematic evidence that ephrin-A5 (EFNA5) is an oocyte-derived membrane ligand capable of regulating oocyte quality during IVM. Cross-species transcriptomic analysis revealed that EFNA5 is stably enriched in mammalian oocytes but markedly reduced in in vitro-matured oocytes compared with in vivo counterparts. Using the ovine IVM model, supplementation with recombinant EFNA5 significantly improved blastocyst formation, increased total cell numbers, and reduced apoptosis. Mechanistically, EFNA5 promoted cumulus-oocyte complex expansion, reduced reactive oxygen species accumulation, activated NRF2-dependent antioxidant signaling, and suppressed NF-κB-driven inflammation. RNA-seq and functional validation further confirmed that EFNA5 enhanced redox homeostasis and decreased DNA damage, collectively improving oocyte developmental potential. These findings establish EFNA5 as a novel and conserved ODF that alleviates oxidative and inflammatory stress to enhance oocyte quality and embryo development, providing mechanistic insight and a potential strategy for improving assisted reproductive technologies.