Thawing fertility: a view of ovarian tissue cryopreservation processes and review of ovarian transplant research

Individuals with a disease or treatment that will increase their risk of premature gonadal insufficiency may opt to undergo fertility preservation. Those who are post-pubertal can often cryopreserve gametes, sperm or eggs, to expand their biological family using assisted reproductive technologies. Ovarian tissue cryopreservation (OTC) and testicular tissue cryopreservation may be an option for individuals who are unable to utilize standard fertility preservation techniques. The development of OTC was critical for many patients, including prepubertal children with ovaries that do not yet produce eggs, adolescents who make few good quality eggs and adult women with ovaries who cannot undergo ovarian stimulation. The only option to restore fertility and hormone production following OTC is through ovarian tissue transplantation (OTT). OTC and OTT have been successful for some patients. While OTC is no longer considered experimental by the American Society of Reproductive Medicine, the process is far from standardized. Significant research needs to be done, especially at the point of OTT, to improve the success and longevity of the ovarian tissue function. This article lists the main steps from surgical procurement of the ovarian tissue to transplantation and restoration of function. Our pediatric hospital program has had to decide which options in procurement, processing, cryopreservation and warming will be used in our clinical lab. The options and limitations within the research and analyses are briefly discussed. Literature focusing on techniques to improve OTT effectiveness and longevity was reviewed. OTT studies that performed xenograft experiments after pretreatment of the tissue graft by a ligand or drug, treatment of host, or encapsulation of the ovarian tissue were identified. The intended effects of the treatments include increasing vascularization, reducing apoptosis and directing activation or suppression of primordial follicles. Robust research in this area must continue with rigorous analyses to make strides for improving fertility preservation and restoration options for patients.