Vitrification and xenografting of human ovarian tissue

Objective: To assess the efficiency of two vitrification protocols to cryopreserve human preantral follicles with the use of a xenografting model. Design: Pilot study. Setting: Gynecology research unit in a university hospital. Patient(s): Ovarian biopsies were obtained from seven women aged 30-41 years. Intervention(s): Ovarian tissue fragments were subjected to one of three cryopreservation protocols (slow freezing, vitrification protocol 1, and vitrification protocol 2) and xenografted for 1 week to nude mice. Main Outcome Measure(s): The number of morphologically normal follicles after cryopreservation and grafting and fibrotic surface area were determined by histologic analysis. Apoptosis was assessed by the TUNEL method. Morphometric analysis of TUNEL-positive surface area also was performed. Follicle proliferation was evaluated by immunohistochemistry. Result(s): After xenografting, a difference was observed between the cryopreservation procedures applied. According to TUNEL analysis, both vitrification protocols showed better preservation of preantral follicles than the conventional freezing method. Moreover, histologic evaluation showed a significantly higher proportion of primordial follicles in vitrified (protocol 2)-warmed ovarian tissue than in frozen-thawed tissue. The proportion of growing follicles and fibrotic surface area was similar in all groups. Conclusion(s): Vitrification procedures appeared to preserve not only the morphology and survival of preantral follicles after 1 week of xenografting, but also their ability to resume folliculogenesis. In addition, vitrification protocol 2 had a positive impact on the quiescent state of primordial follicles after xenografting. (Fertil Steril (R) 2012;98: 1291-8. (C) 2012 by American Society for Reproductive Medicine.)