Protecting spermatogonial stem cells from chemotherapy-induced damage for fertility preservation in childhood cancer

近几十年来，儿童癌症发病率急剧增加（自1960年以来为38%），目前每500名成年人中就有1人（英国约35000人）是儿童癌症的幸存者。发病率的增加，加上治愈率的显著提高（>80%的5年生存率），导致年轻人经历癌症治疗的后续健康影响的增加。确保这一新的和不断扩大的患者群体的长期健康是儿科肿瘤学临床需求的最紧迫领域之一。不孕症发生在大多数接受大剂量化疗的男性中，化疗药物被称为烷化剂。烷化剂通常用于儿童癌症，越来越多地用于非恶性疾病的干细胞移植。与男性的情况不同，精液冷冻保存不是保持这些男孩生育能力的一种选择，因为他们的睾丸在童年时期无法制造精子。因此，目前还没有确定的临床选择，以防止不育的青春期前男孩接受化疗。在接受癌症治疗的儿童中，生育能力的保持取决于睾丸中精原干细胞（SSC）的存活。这些干细胞将在青春期后在男性体内产生精子。在接受癌症治疗的儿童中保存生育能力的实验方法可以包括在患者接受治疗之前对睾丸进行活检并将其储存以供将来用于恢复生育能力，尽管迄今为止还没有开发出使用这种方法恢复生育能力的方法。此外，这需要进行侵入性手术，可能有重新引入恶性细胞的风险，并可能需要人工生殖技术来恢复生育能力。因此，制定在化疗期间保护睾丸的策略将是癌症儿童临床护理的一个重大进步。该项目的目的是了解更多关于青春期前人类睾丸中的SSCs以及它们如何受到化疗的影响。我们将确定化疗药物如何进入SSC以及如何导致细胞死亡。还将确定化疗后SSC人群随时间恢复的可能性。在建立了使SSC对化疗敏感的机制之后，我们将开发和测试可以保护SSC并使它们在化疗中存活的药物。这些药物可能在化疗时给予患者，以保留未来的生育能力。我们已经开发了实验方法，使我们能够测试化疗暴露对青春期前人类睾丸的影响，使用从接受癌症治疗前的癌症男孩中获得的组织。我们可以联合收割机将化疗暴露与来自广泛的已知和新开发的药物中的额外药物相结合，以确定那些保护SSC免受化疗损伤的药物。这种“化学保护”剂的鉴定将被用于未来的临床试验，旨在保护癌症儿童的生育能力。我们预计，这个项目将是一个重要的一步，朝着发展的治疗，将保持生育能力的男孩接受化疗治疗。

Childhood cancer rates have increased dramatically (38% since 1960) over recent decades and currently 1 in 500 adults (~35000 in UK) is a survivor of childhood cancer. The increasing incidence, coupled with remarkable improvements in cure rates (>80% 5-year survival), have resulted in an increase in young adults experiencing subsequent health effects of their cancer treatment. Ensuring long-term health of this new and expanding patient cohort is one of the most pressing areas of clinical need in paediatric oncology. Infertility occurs in the majority of males receiving high-dose chemotherapy with drugs known as alkylating agents. Alkylating agents are used commonly in childhood cancer and increasingly for stem cell transplant in non-malignant disorders. Unlike the situation in men, semen cryopreservation is not an option to preserve fertility in these boys as their testicles are not capable of making sperm in childhood. As a result, there is currently no established clinical option to prevent infertility in prepubertal boys receiving chemotherapy. Preservation of fertility in children receiving cancer treatment is dependent on survival of the spermatogonial stem cells (SSC) in the testicle. These stem cells will generate sperm in males after puberty. Experimental approaches for fertility preservation in children undergoing cancer treatment could include taking a biopsy of the testicle before the patient receives their treatment and storing it for future use to restore fertility, although no methods to restore fertility using this approach have been developed so far. In addition, this requires invasive surgery, may carry a risk of re-introducing malignant cells and may require artificial reproductive techniques to restore fertility. Therefore, developing strategies to protect the testicles during chemotherapy treatment would represent a major advance for the clinical care of children with cancer. The aim of this project is to understand more about the SSCs in the prepubertal human testicle and how they are affected by chemotherapy. We will determine how the chemotherapy agents enter the SSC and how this causes the cell to die. The potential for recovery of the SSC population over time following chemotherapy treatment will also be determined. Having established the mechanisms that make SSC sensitive to chemotherapy, we will develop and test drugs that can protect the SSC and allow them to survive chemotherapy. These drugs could potentially be given to the patient at the time of their chemotherapy to preserve future fertility. We have developed experimental approaches that allow us to test the effects of chemotherapy exposure on the prepubertal human testicle using tissue obtained from boys with cancer prior to receiving cancer treatment. We can combine the exposure to chemotherapy with an additional drug from a wide-range of known and newly developed drugs to identify those that protect the SSC from the chemotherapy damage. Identification of such 'chemo-protective' agents would then be taken forward into future clinical trials aimed at preserving fertility in children with cancer. We anticipate that this project will be an important step towards development of treatments that will preserve fertility in boys receiving chemotherapy treatment.