The production of haploid gametes through meiosis is central to the principle of sexual reproduction. The genetic diversity is further enhanced by exchange of genetic material between homologous chromosomes by the crossover mechanism. This mechanism not only requires correct pairing of homologous chromosomes but also efficient repair of the induced DNA double-strand breaks. Oocytes have evolved a unique quality control system that eliminates cells if chromosomes do not correctly align or if DNA repair is not possible. Central to this monitoring system that is conserved from nematodes and fruit fly to humans is the p53 protein family, and in vertebrates in particular p63. In mammals, oocytes are stored for a long time in the prophase of meiosis I which, in humans, can last more than 50 years. During the entire time of this arrest phase, the DNA damage checkpoint remains active. The treatment of female cancer patients with DNA damaging irradiation or chemotherapeutics activates this checkpoint and results in elimination of the oocyte pool causing premature menopause and infertility. Here, we review the molecular mechanisms of this quality control system and discuss potential therapeutic intervention for the preservation of the oocyte pool during chemotherapy.

Cryopreservation of ovarian tissue is one feasible option to preserve female fertility prior to cancer treatment. The slow freezing protocol represents the current standard approach, while vitrification has been suggested as a promising alternative. This paper reports the follow-up and first successful delivery after retransplantation of vitrified, rapid warmed ovarian tissue in Europe. After the patient received a diagnosis of breast cancer, ovarian tissue was removed laparoscopically and sent via overnight transportation to University Hospital Bonn for vitrification on site. The patient was treated with chemotherapy, leading to ovarian failure. After 2 years, retransplantation of the vitrified, rapid warmed tissue was conducted on site. Two months after grafting, the patient reported regular menstrual cycles. After 1 further month a clinical pregnancy occurred, which ended in a spontaneous abortion at the 8th week of pregnancy. Six months after grafting, another naturally conceived pregnancy was determined, resulting in the birth of a healthy boy 14 months after retransplantation of the ovarian tissue. Complementing the successful deliveries reported by the groups of Suzuki (Japan) and Silber (USA) regarding vitrified tissue, the current results confirm the high potential of this cryopreservation method in a clinical routine setting as an alternative approach to the widespread slow freezing method.

Background: Cytotoxic treatments such as chemo- and radiotherapy and immune therapies are required in cancer diseases. These therapies have the potential to cure patients but may also have an impact on gonadal function and, therefore, on fertility. Consequently, fertility preservation treatments such as freezing of gametes and gonadal tissue might be required. However, as detailed data about the necessity to perform fertility preservation treatment are very limited, this study was designed to fill this data gap. Objective: Primary objective of this study is to analyze the impact of cancer therapies and chemotherapies on the ovarian reserve and sperm quality. Secondary objectives are to analyze the (1) impact of cancer therapies and chemotherapies on other fertility parameters and (2) probability of undergoing fertility preservation treatments in relation to specific cancer diseases and treatment protocols and the probability to use the frozen gametes and gonadal tissue to achieve pregnancies. Methods: First, previously published studies on the gonadotoxicity of chemo- and radiotherapies among patients with cancer will be systematically analyzed. Second, a prospective cohort study set up by approximately 70 centers in Germany, Switzerland, and Austria will collect the following data: ovarian function by analyzing anti-Müllerian hormone (AMH) concentrations and testicular function by analyzing sperm parameters and total testosterone immediately before and around 1 year after gonadotoxic therapies (short-term fertility). A follow-up of these fertility parameters, including history of conceptions, will be performed 5 and 10 years after gonadotoxic therapies (long-term fertility). Additionally, the proportion of patients undergoing fertility-preserving procedures, their satisfaction with these procedures, and the amount of gametes and gonadal tissue and the children achieved by using the frozen material will be analyzed. Third, the data will be merged to create the internet-based data platform FertiTOX. The platform will be structured in accordance with the ICD (International Classification of Diseases) classification of cancer diseases and will be easily be accessible using a specific App. Results: Several funding bodies have funded this study. Ten systematic reviews are in progress and the first one has been accepted for publication. All Swiss and many German and Austrian ethics committees have provided their approval for the prospective cohort study. The study registry has been set up, and a study website has been created. In total, 50 infertility centers have already been prepared for data collection, which started on December 1, 2023. Conclusions: The study can be expected to bridge the data gap regarding the gonadotoxicity of cancer therapies to better counsel patients about their infertility risk and their need to undergo fertility preservation procedures. Initial data are expected to be uploaded on the FertiTOX platform in 2026. Trial Registration: ClinicalTrials.gov NCT05885048; https://clinicaltrials.gov/study/NCT05885048 International Registered Report Identifier (IRRID): DERR1-10.2196/51145

Background: The standard procedure most frequently used for ovarian tissue cryopreservation (OTC) is slow freezing, while vitrification has been proposed as promising alternative and has built an impressive catalog of success in fertility laboratories regarding cryopreservation of oocytes and embryos. Methods: We developed and evaluated a high-throughput protocol for vitrification of human ovarian tissue suitable for clinical processing. Follicular viability was assessed via calcein staining prior and after cryopreservation analyzing ovarian tissue of a cohort of 30 patients. Results: We found no significant differences regarding follicular viability between slow frozen and vitrified cortex tissue samples 24 h after thawing and rapid warming. Follicular viability of thawed and rapid warmed samples was not significantly different in comparison to fresh samples, indicating high proportions of follicular survival rates with both methods. Conclusions: High-throughput vitrification is a promising option in a clinical setting. More research is required to determine the status of other tissue-specific quality indicators potentially influencing on autotransplantation.