JBRA Assist. Reprod. 2025;29(Suppl 1):29-29
POSTER PRESENTATION
doi: 10.5935/1518-0557.20250083
1IECH - Fertility Center, Monterrey, Nuevo León, Mexico
Objective: To evaluate whether reducing exposure time to cryoprotectants using an ultra-rapid vitrification protocol affects oocyte survival and maturation competence compared to a standard vitrification protocol. Oocyte vitrification has become a fundamental component of assisted reproductive technologies (ART), offering flexibility for both donor and patient cycles, fertility preservation, and cumulative pregnancy strategies. The standard vitrification protocol, although effective, involves prolonged exposure to cryoprotectants, which may increase the risk of osmotic and chemical toxicity, potentially compromising oocyte quality. Recent innovations have focused on minimizing cryoprotectant exposure time to reduce these risks. An ultra-rapid vitrification protocol aims to shorten the equilibration phase and total protocol duration, theoretically decreasing cryoinjury while maintaining or improving oocyte viability and maturation competence.
Methods: A prospective, experimental, and correlational study was conducted at the IECH-Fertility Center between September 2023 and March 2024. Discarded donated sibling oocytes were included and randomly assigned to one of two protocols:
• Ultra-rapid vitrification group: Equilibration solution (ES) for 1 minute and vitrification solution (VS) for 1 minute. Warming was performed using thawing solution (TS) for 1 minute and washing solution (WS) for 1 minute.
• Standard vitrification group: ES for 12 minutes and VS for 1 minute. Warming involved TS for 1 minute, dilution solution (DS) for 3 minutes, and WS for 5 minutes.
Survival was assessed post-warming based on morphological integrity. Maturation competence was evaluated 24 hours after warming, classifying oocytes as germinal vesicle (GV), metaphase I (MI), or metaphase II (MII). Descriptive statistics were reported as medians and interquartile ranges (IQR) or percentages, as appropriate. Comparisons between groups were performed using the Kruskal-Wallis and Chi-square tests. Statistical significance was defined as p<0.05.
Results: A total of 306 oocytes were analyzed, with 100 assigned to the ultra-rapid group and 206 to the standard group. The median donor age was 23 years (IQR = 4) in the ultra-rapid group and 22 years (IQR = 3) in the standard group (p<0.0006). Survival rates post-warming were 97% in the ultra-rapid group and 93% in the standard group, with no statistically significant difference (p=0.1944). At 24 hours, oocyte nuclear maturation in the ultra-rapid group was as follows:
• MII: 49 oocytes (100%)
• MI: 24 oocytes (54%)
• GV: 27 oocytes (33%)
Note: Percentages are based on the total number of surviving oocytes in each maturation stage category.
Conclusion: The preliminary results suggest that the ultra-rapid vitrification protocol (PUR-V) yields comparable survival and nuclear maturation outcomes to the standard protocol. The reduction in cryoprotectant exposure time does not appear to compromise oocyte viability and may offer additional advantages in workflow efficiency and reduced protocol duration. These findings support the feasibility of implementing PUR-V in clinical settings, particularly in high-throughput oocyte banking for both donor and autologous cycles. Further studies with larger sample sizes and embryo developmental follow-up are warranted to confirm the clinical utility and safety of this approach.