Received June 06, 2021
Accepted January 30, 2022

Objective: To compare oocyte survival and meiotic spindle normality between vitrified-warmed oocytes in a mouse assay using the novel prototype Tvitri-4 medium (T4) or a standard commercial kit supplied by Ingámed (ING). Methods: C57BL/6 female mice 8-12 weeks were submitted to superovulation with pregnant mare’s serum gonadotropin and human chorionic gonadotropin (hCG) for obtaining of in vivo matured oocytes. The oocytes were randomly distributed in: CTR-control (fresh oocytes), ING and in T4. After warming and recovery culture, were assessed to survival rate (SR) and both meiotic spindle morphology and chromosome alignment of each oocyte fixed and analysis by confocal microscopy. Results: A total of 354 mature oocytes were vitrified in ING (n = 178) and T4 (n = 176). Oocyte SR were not statistically different (p = 0.08) between ING (145/178, 81.5%) and T4 (154/176, 87.5%). Regarding meiotic normality, there were no significant changes in the proportion of oocytes with normal meiotic spindle morphology and chromosome structure between ING (52,2%) and T4 (63.4%) after warming (RR: 0.95, 95% CI: 0.92-1.607). When the meiotic normality was assessed using the CTR group as reference no significant differences were observed between T4 (63.4%) and CTR (70.5%) (RR: 0.95, 95% CI: 0.72-1.12). And the percentage in ING (52.2%) was different of the CTR group (RR: 0.95, 95% CI: 0.57-0.97). Conclusion: The novel prototype Tvitri-4 medium was efficient in preserve SR and meiotic spindle normality of oocytes and, with further verification, may be able to replace commercially available media in future clinical applications.