Background Anti-cancer therapy is often a cause of premature ovarian insufficiency and infertility since the ovarian follicle reserve is extremely sensitive to the effects of chemotherapy and radiotherapy. While oocyte, embryo and ovarian cortex cryopreservation can help some women with cancer-induced infertility achieve pregnancy, the development of effective methods to protect ovarian function during chemotherapy would be a significant advantage. Objective and rationale This paper critically discusses the different damaging effects of the most common chemotherapeutic compounds on the ovary, in particular, the ovarian follicles and the molecular pathways that lead to that damage. The mechanisms through which fertility-protective agents might prevent chemotherapy drug-induced follicle loss are then reviewed. Search methods Articles published in English were searched on PubMed up to March 2019 using the following terms: ovary, fertility preservation, chemotherapy, follicle death, adjuvant therapy, cyclophosphamide, cisplatin, doxorubicin. Inclusion and exclusion criteria were applied to the analysis of the protective agents. Outcomes Recent studies reveal how chemotherapeutic drugs can affect the different cellular components of the ovary, causing rapid depletion of the ovarian follicular reserve. The three most commonly used drugs, cyclophosphamide, cisplatin and doxorubicin, cause premature ovarian insufficiency by inducing death and/or accelerated activation of primordial follicles and increased atresia of growing follicles. They also cause an increase in damage to blood vessels and the stromal compartment and increment inflammation. In the past 20 years, many compounds have been investigated as potential protective agents to counteract these adverse effects. The interactions of recently described fertility-protective agents with these damage pathways are discussed. Wider implications Understanding the mechanisms underlying the action of chemotherapy compounds on the various components of the ovary is essential for the development of efficient and targeted pharmacological therapies that could protect and prolong female fertility. While there are increasing preclinical investigations of potential fertility preserving adjuvants, there remains a lack of approaches that are being developed and tested clinically.

It is likely that different chemotherapeutic drugs act through a range of mechanisms and on different target cells. More research into the cellular mechanisms underpinning chemotherapy-induced follicle loss could lead to the generation of treatments specifically designed to prevent POF.

Infertility represents a major clinical problem and 50% of cases are attributable to the male partner. Testicular function is temperature dependent, and in both man and mouse the position of the testes in the scrotum ensures that they are kept at between 2 and 8 8C below core body temperature. We used a mouse model to investigate the impact of a single, transient, mild, scrotal heat stress (38, 40 or 42 8C for 30 min) on testicular function, sperm DNA integrity and embryo survival. We detected temperature-dependent changes in testicular architecture, number of apoptotic cells and a significant reduction in testis weight 7 and 14 days after heat stress at 42 8C. We report for the first time that DNA strand breaks (g-H2AX-positive foci) were present in spermatocytes recovered from testes subjected to 40 or 42 8C. Fertility of heat-stressed males was tested 23-28 d after treatment (sperm at this time would have been spermatocytes at time of heating). Paternal heat stress at 42 8C resulted in reduced pregnancy rate, placental weight and litter size; pregnancies from the 40 8C group had increased resorptions at e14.5. Abnormalities in embryonic development were detected at e3.5 and in vitro fertilisation with sperm recovered 16 h or 23 d after scrotal stress at 42 8C revealed a block in development between the 4-cell and blastocyst stages. This study has provided evidence of temperature-dependent effects on germ cell DNA integrity and highlighted the importance of an intact paternal genome for normal embryo development. Reproduction (2008) 136 73-84

Preservation of gonadal function,is an important priority for the longterm health of cancer survivors of both sexes and all ages at treatment.. The loss of an opportunity for fertility is a prime concern in both male and female cancer survivors, however the endocrine consequences of gonadal damage are also central to longterm health and wellbeing. Some fertility preservation techniques, such as semen and embryo cryopreservation for the adult man and woman respectively, are established and successful and the recent development of oocyte vitrification has greatly improved the potential to cryopreserve unfertilised oocytes from women. Despite being recommended for all pubertal males, sperm banking is not universally practised in Paediatric Oncology centres, and there are very few 'adolescentfriendly' facilities. All approaches to fertility preservation have particular challenges in children and teenagers, including ethical, practical and scientific issues. For the young female, cryopreservation of ovarian cortical tissue with later replacement has now resulted in at least 35 live births, but is still regarded as experimental in most countries. For prepubertal males, testicular biopsy cryopreservation is offered in some centres, but it is unclear how that tissue might be used in the future, and to date there is no evidence that fertility can be restored. For both sexes these approaches require an invasive procedure, and there is an uncertain risk of tissue contamination in haematological and other malignancies. Decision making for all these approaches requires an assessment of the individual's risk of loss of fertility, and is being made at a time of emotional distress. The development of this field requires better provision of information for patients and their medical teams as well as improvements in service provision, to match technical and scientific advances. Search strategy and selection criteriaWe searched Medline between Jan 1, 1990, and Sept 1, 2014, for reports published in English using the search terms "fertility preservation", "cancer", "childhood cancer", "gonadotoxic", and "cancer treatment" in several disjunctive and conjunctive combinations. We mainly selected publications in English from the past 5 years, but did not exclude older, significant publications. We also checked the reference lists of articles identified by this search strategy.

A model culture system has been developed whereby individual, primary ovarian mouse follicles can be grown in vitro to the Graafian stage in the normal physiological time course, and then ovulated in response to luteinizing hormone. We report here on the successful fertilization and subsequent embryo development of the oocytes from such follicles. This is the first time that oocytes from in-vitro matured whole follicles have been fertilized and shown to produce viable offspring in host animals. The study demonstrates that the culture system mimics physiological conditions for normal follicle development.