Ovarian tissue cryopreservation protocols remain unstandardized for women and prepubertal girls facing gonadotoxic cancer therapiesNo universal standard exists yet for freezing ovaries before cancer treatment

BackgroundCryopreservation is widely used across the life sciences to enable long-term storage of living cells and tissues for research or later clinical use. Its core principle is the arrest of biological activity at extremely low temperatures. Ovarian tissue cryopreservation (OTC) has become an important fertility-preserving option for women and prepubertal girls facing gonadotoxic cancer therapies.Objective and rationaleThis review summarizes the history of OTC and provides an overview of current procedures and their relevance for fertility preservation. It outlines key principles of cryopreservation, including different techniques, cryoprotective agents, molecular mechanisms, recent achievements, remaining challenges, and future perspectives. Although OTC is clinically established, protocols remain variable and require further optimization to improve tissue and follicle viability. Differences in media composition, cryoprotectants, slow freezing vs. vitrification, and thawing or warming procedures—along with ongoing debate over which technique is superior—highlight the need for research toward a standardized approach.Search methodsPubMed and MEDLINE were searched for literature published before June 2025 using the keywords cryopreservation, ovarian tissue cryopreservation (OTC), vitrification, slow freezing, nanowarming, whole organ freezing, cryoprotective agents. Reference lists were screened back to 1993. Only English-language publications were included.OutcomesThe literature review shows that no universally standardized OTC protocols exist for slow freezing or vitrification. Although both methods are routinely applied worldwide, differences in crucial steps may affect tissue quality and clinical outcomes. Thawing and warming, also essential for tissue viability, is not standardized. These findings emphasize the need for continued optimization. Research on whole-organ freezing and nanowarming is also progressing. Nanowarming aims to enable uniform warming of larger, more complex tissues, with two promising technologies—electromagnetic warming and photothermal heating—currently evaluated in animal models.Wider implicationsAs oncological treatments advance and more young female cancer patients survive, the demand for effective and standardized OTC procedures continues to grow. OTC remains the preferred fertility-preservation method for patients unable to undergo ovarian stimulation or for prepubertal girls. This review outlines current methods, highlights advances in nanowarming and whole-organ cryopreservation, and provides future perspectives for improving OTC and related technologies.