Cryopreservation and xenotransplantation of human ovarian tissue: an ultrastructural study

ObjectiveTo analyze the ultrastructure of human ovarian follicles after cryopreservation and short-term xenografting.DesignProspective experimental study.SettingAcademic gynecology and anatomy research units.Patient(s)Ovarian cortical biopsy specimens were obtained from 13 patients.Intervention(s)Each ovarian biopsy specimen was dissected into pieces of 1 mm3 and divided into three groups: [1] fresh tissue, [2] frozen-thawed tissue, and [3] frozen-thawed tissue xenografted onto the peritoneum of nude mice for 3 weeks.Main Outcome Measure(s)Follicular ultrastructure was assessed by light and transmission electron microscopy in [1] fresh, [2] frozen, and [3] frozen-grafted tissue.Result(s)Thirty-five ovarian follicles were analyzed by light and transmission electron microscopy. Twenty-five primordial and primary ovarian follicles were found. Most of them exhibited ultrastructurally well preserved features (fresh [N = 8/10], frozen [N = 7/10], and frozen-grafted [N = 4/5] tissue). Ten secondary follicles were present in xenografts. By transmission electron microscopy, all the healthy-looking secondary follicles (70%) were shown to contain intact oocytes, with features typical of earlier developmental stages, surrounded by several layers of follicular cells.Conclusion(s)The present study demonstrates, for the first time, that cryopreservation and xenotransplantation do not appear to greatly affect human primordial/primary follicle ultrastructure. Interestingly, in frozen-thawed xenografts, secondary human ovarian follicles presented a well preserved ultrastructure, but asynchrony between oocyte and granulosa cell development was detected. The possible causes for this asynchrony are discussed.