Methods
After grafting, follicle survival, growth and function and also the quality of stromal tissue were assessed histologically and by immunohistochemistry. The influence of the vitrification procedure on the cooling rate was evaluated by a computer model. Main
Results
After vitrification, warming and long-term grafting, follicles were able to grow and maintain their function, as illustrated by Ki67, anti-Müllerian hormone (AMH) and growth differentiation factor-9 (GDF-9) immunostaining. Corpora lutea were also observed, evidencing successful ovulation in all the 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. Limitations, reasons for caution: Despite our promising findings, before applying this technique in a clinical setting, we need to validate it by achieving pregnancies. Wider implications of the findings: In addition to encouraging results obtained with our vitrification procedure for non-human ovarian tissue, this study also showed, for the first time, expression of AMH and GDF-9 in ovarian follicles. Study funding/competing interest(s): This study was supported by grants from the Fonds National de la Recherche Scientifique de Belgique (grant Télévie No. 7.4507.10, grant 3.4.590.08 awarded to Marie-Madeleine Dolmans), Fonds Spéciaux de Recherche, Fondation St Luc, Foundation Against Cancer, and Department of Mechanical Engineering at Louisiana State University (support to Ram Devireddy), and donations from Mr Pietro Ferrero, Baron Frère and Viscount Philippe de Spoelberch. None of the authors has any competing interests to declare.