Vitrification altered αV and β3 integrin expression in mouse oocytes in a maturation stage-dependent manner

Integrin αVβ3 has been implicated in oocyte membrane organization and sperm-oocyte interaction. This study investigated the effects of vitrification on post-warming survival and on the surface expression of integrin αV and β3 subunits in mouse oocytes at the germinal vesicle (GV) and metaphase II (MII) stages.

A total of 400 oocytes were collected from NMRI mice and allocated into four equal groups: non-vitrified GV, vitrified GV, non-vitrified MII, and vitrified MII (n = 100 per group). Vitrification was performed using the Cryotop method, followed by one month of storage in liquid nitrogen at - 196 °C. Post-warming survival was assessed morphologically. Integrin αV and β3 expression was evaluated at the protein level by immunocytochemistry and at the transcript level by quantitative real-time reverse-transcription PCR (RT-qPCR).

Vitrification did not significantly affect post-warming survival rates in GV or MII oocytes compared with their non-vitrified counterparts (90% vs. 88%, P > 0.05). Immunocytochemical analysis demonstrated that both αV and β3 surface protein expression was significantly higher in MII oocytes than in GV oocytes, irrespective of vitrification status. Vitrification significantly reduced αV and β3 protein expression in MII oocytes compared with non-vitrified MII oocytes (P < 0.05 and P < 0.001, respectively), whereas reductions in GV oocytes were not statistically significant (P > 0.05). Quantitative RT-PCR broadly corroborated these findings: non-vitrified MII oocytes exhibited the highest transcript levels for both subunits, and β3 mRNA was significantly decreased in vitrified MII oocytes (P < 0.05). Although αV transcript levels showed a downward trend following vitrification, these reductions did not reach statistical significance in either stage (P > 0.05).

Despite preserving post-warming morphological survival, vitrification induced significant alterations in αV and β3 integrin expression in a maturation stage-dependent manner, with MII oocytes being disproportionately affected. These findings suggest that molecular analysis of membrane-associated proteins may provide information complementary to morphological criteria when assessing oocyte quality following cryopreservation.