Freezing, thawing, and autograft of ovarian fragments in sheep: preliminary experiments and histologic assessment

Objective: To evaluate the effects of freezing and thawing on the histologic changes in ovarian fragments from sheep and to determine the feasibility of ovarian autografts. Design: Histologic evaluation of follicles that survived after freezing at −196°C for 2 weeks. Histologic evaluation of ovarian fragments 6 months after the autografts. Setting: Laboratoire de Zootechnie, Ecole National Véterinaire, Marcy l’Etoile, France. Animal(s): Six ewes aged 6 months to 1 year. Intervention(s): Cortical fragments were prepared from the right ovary of 6 lambs and were grafted immediately to the contralateral ovarian hilus or were cooled slowly to −196°C in medium containing dimethyl sulfoxide for 2 weeks. The autografts were recovered 6 months later. Result(s): Histologic examination of ovarian slices after freezing showed no destruction of primordial, primary, secondary, or cavitary follicles. The ovarian autograft showed good recovery of the macroscopic and microscopic ovarian structure. After autografting, histologic examination revealed primordial to cavitary follicles. Conclusion(s): Freezing of ovarian fragments is possible without damaging the follicles. Ovarian autografts showed good recovery of ovarian structure.