Vitrification of baboon ovarian tissue: will vitrification replace conventional freezing for ovarian tissue cryopreservation?

Objective: The aim of this study was to evaluate the efficacy of a vitrification protocol developed by our group to cryopreserve ovarian tissue. For this, we used ovaries from non-human primates in order to have an animal model close to the clinical setting. Materials and methods: Ovarian biopsies from five adult baboons were vitrified, warmed and autografted. After five months, follicle survival, growth and function were assessed. The quality of stromal tissue and influence of the vitrification procedure on the cooling rate were also evaluated. Results: Our results showed that after vitrification, warming and grafting, follicles were able to grow and maintain their function, as illustrated by Ki67, anti-Müllerian hormone and growth differentiation factor-9 immunostainings. Corpora lutea were also observed, evidencing successful ovulation in all animals. Stromal tissue quality did not appear to be negatively affected by our cryopreservation procedure, as demonstrated by vascularization and proportions of fibrotic areas, which were similar to those found in fresh ungrafted ovarian tissue. Conclusion: Our results indicate that baboon ovarian tissue can be successfully cryopreserved using our vitrification protocol. However, before applying this technique in a clinical setting, we need to validate it by obtaining pregnancies.