ASSESSING THE EFFECT OF PREOVULATORY AGING ON OOCYTE QUALITY

WETTEN PA; KLINSKY LAHOZ OG; ROMANI JE; MICHAUT MA

San Juan

Congreso; XLI Reunión Científica Anual de la Sociedad de Biología de Cuyo; 2023

Sociedad de Biología de Cuyo

Women increasingly turn to fertility clinics in their quest to overcome reproductive challenges. It is common practice in these institutions to use GnRH analogs to prevent premature luteinizing hormone (LH) surges in women undergoing assisted reproductive technology (ART) treatments. This procedure delays ovulation and consequently leads to pre-ovulatory oocyte aging (PreOA). Given that it is widely acknowledged that oocyte quality plays a significant role in determining the developmental potential of embryos following fertilization, it is plausible that ART treatments that cause delayed ovulation could impact the quality and competence of oocytes. This study aimed to evaluate the effect of PreOA on features that contribute to oocyte quality. Hormonal stimulation using a GnRH analog was applied to CF1 female mice to prevent premature ovulation, leading to the development of a PreOA model. For the control conditions, female CF1 mice were hormonally stimulated without the GnRH analog. Examination of oocyte quality focused on the assessment of mitochondrial membrane potential (MMP), ATP levels, the presence of reactive oxygen species (ROS), and acidic compartments in living cells using confocal microscopy. Results showed that MMP was diminished in pre-ovulatory aged oocytes compared to control cells. However, no significant differences in ATP levels were observed. ROS levels were increased in oocytes with pre-ovulatory aging with respect to control oocytes. When acidic compartments were studied using monodansylcadaverin, the results showed a significant increase in the fluorescence signal compared with control oocytes. Considering the importance of cortical granules in the fertilization process, we analyzed the localization of cortical granules in fixed cells stained with the specific fluorescent lectin, LCA. Surprisingly, while control oocytes showed normal CG localization in the cortical region of oocytes, mislocalized CG were found in the cytoplasm of pre-ovulatory aged oocytes. These results indicate that pre-ovulatory oocyte aging alters oocyte quality to the detriment of the success of reproductive-assisted techniques.