Cellular Mechanisms of Chemotherapy-induced Male Infertility: Stem Cell or Niche?

描述（由申请人提供）： 精原干细胞（SSCs）是精子发生的基础，可用于治疗某些男性不育症。癌症和其他非恶性疾病的高剂量化疗治疗可能导致无精子症，这可能是由于SSC池的耗尽。如果是这种情况，并且睾丸环境（SSC生态位）在功能上是完整的，那么SSC移植可能构成用于恢复男性癌症幸存者生育能力的基于细胞的疗法。从理论上讲，SSCs可以通过活检分离并在癌症治疗前冷冻保存，然后在治愈后重新引入睾丸以再生精子发生。这种方法的原理已经在几种动物模型中得到了证实，包括我们实验室在灵长类动物中的最新进展。因此，很容易推测SSC移植可能会转化为人类生育诊所。这种选择可能特别适合尚未产生精子的青春期前男孩，他们没有选择来保持未来的生育能力。考虑到这一点，世界各地的几个学术中心，包括我们在匹兹堡的生育力保存计划，正在为男孩冷冻保存睾丸组织，以期将来可以使用SSC来恢复生育力。迫切需要临床前研究来证明SSC移植在与人体解剖学和生理学以及目标青春期前患者人群相关的模型中的可行性。在本申请中，我们将用临床相关的高剂量烷化剂化疗方案（BuCy 2）治疗青春期前恒河猴，该方案预计会导致无精子症。非人灵长类动物和人类睾丸中的SSC池由Adark和Apale精原细胞组成，但这些形态学上不同的精原细胞亚型的相对再生潜力尚不清楚。在目标1中，我们将评估和比较Adark和Apale精原细胞的干细胞特性，这将影响操纵这些细胞用于治疗目的的策略。目的2将检查BuCy 2对青春期前睾丸的干细胞库和体细胞/内分泌环境（干细胞生态位）的影响。目标3将模拟青春期前患者的临床情况， 造血干细胞移植前BuCy 2预处理导致无精子症的高风险。在该模型中，我们将从冷冻/解冻的睾丸细胞中进行自体SSC移植。目标1和2中产生的基础知识可能导致新的SSC富集和小生境治疗策略，这些策略将应用于目标3，以增强内源性或移植的SSC的精子发生。

DESCRIPTION (provided by applicant): Spermatogonial stem cells (SSCs) are at the foundation of spermatogenesis and may have application for treating some cases of male infertility. High dose chemotherapy treatments for cancer and other non-malignant conditions can cause azoospermia, which may be due to a depletion of the SSC pool. If that is the case and the testicular environment (SSC niche) is functionally intact, then SSC transplantation may constitute a cell based therapy for restoring fertility in male cancer survivors. Theoretically, SSCs can be isolated via biopsy and cryopreserved prior to cancer treatment and then reintroduced into the testis after cure to regenerate spermatogenesis. The proof in principle for this approach is already established in several animal models, including recent progress from our lab in primates. Therefore, it is tempting to speculate that SSC transplantation might be translated to the human fertility clinic. This option may be particularly appropriate for prepubert boys who are not yet producing sperm and have no options to preserve their future fertility. With this in mind, several academic centers around the world, including our Fertility Preservation Program in Pittsburgh, are cryopreserving testicular tissues for boys in anticipation that SSCs can be used in the future to restore fertility. Pre-clinical studies are critically needed to demonstrate the feasibility of SSC transplantation in a model that is relevant to human anatomy and physiology as well as the target prepubertal patient population. In this application, we will treat prepubertal rhesus macaques with a clinically relevant high-dose alkylating chemotherapy regimen (BuCy2) that is expected to cause azoospermia. The SSC pool in nonhuman primate and human testes is comprised of Adark and Apale spermatogonia, but the relative regenerative potential of these morphologically distinct spermatogonial subtypes are not known. In Aim 1 we will evaluate and compare the stem cell properties of Adark and Apale spermatogonia, which will impact strategies to manipulate these cells for therapeutic purposes. Aims 2 will examine the effects of BuCy2 on the stem cell pool and somatic/endocrine environment (stem cell niche) of prepubertal testes. Aim 3 will model the clinical scenario of the prepubertal patient that is at high risk for azoospermia due to BuCy2 conditioning prior to hematopoietic stem cell transplantation. In that model, we will perform autologous SSC transplantation from frozen/thawed testicular cells. Fundamental knowledge generated in aims 1 and 2 could lead to novel SSC enrichment and niche therapy strategies that will be applied in Aim 3 to enhance spermatogenesis from endogenous or transplanted SSCs.