Spermatogonial stem cells (SSCs) are a rare group of cells in the testis that undergo self-renewal and complex sequences of differentiation to initiate and sustain spermatogenesis, to ensure the continuity of sperm production throughout adulthood. The difficulty of unequivocal identification of SSCs and complexity of replicating their differentiation properties in vitro have prompted the introduction of novel in vivo models such as germ cell transplantation (GCT), testis tissue xenografting (TTX), and testis cell aggregate implantation (TCAI). Owing to these unique animal models, our ability to study and manipulate SSCs has dramatically increased, which complements the availability of other advanced assisted reproductive technologies and various genome editing tools. These animal models can advance our knowledge of SSCs, testis tissue morphogenesis and development, germ-somatic cell interactions, and mechanisms that control spermatogenesis. Equally important, these animal models can have a wide range of experimental and potential clinical applications in fertility preservation of prepubertal cancer patients, and genetic conservation of endangered species. Moreover, these models allow experimentations that are otherwise difficult or impossible to be performed directly in the target species. Examples include proof-of-principle manipulation of germ cells for correction of genetic disorders or investigation of potential toxicants or new drugs on human testis formation or function. The primary focus of this review is to highlight the importance, methodology, current and potential future applications, as well as limitations of using these novel animal models in the study and manipulation of male germline stem cells.

中文翻译：

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使用动物模型研究和操作精原干细胞

精原干细胞 (SSC) 是睾丸中的一组罕见细胞，它们经历自我更新和复杂的分化序列以启动和维持精子发生，以确保整个成年期精子生产的连续性。明确鉴定 SSC 的难度和体外复制其分化特性的复杂性促使引入了新的体内模型，如生殖细胞移植 (GCT)、睾丸组织异种移植 (TTX) 和睾丸细胞聚集体植入 (TCAI)。由于这些独特的动物模型，我们研究和操纵 SSC 的能力显着提高，这补充了其他先进辅助生殖技术和各种基因组编辑工具的可用性。这些动物模型可以增进我们对 SSC 的了解，睾丸组织形态发生和发育、生殖-体细胞相互作用以及控制精子发生的机制。同样重要的是，这些动物模型在青春期前癌症患者的生育力保存和濒危物种的遗传保护方面具有广泛的实验和潜在的临床应用。此外，这些模型允许直接在目标物种中进行难以或不可能的实验。例子包括对生殖细胞进行原理验证操作以纠正遗传疾病或研究潜在毒物或新药对人类睾丸形成或功能的影响。本次审查的主要重点是强调重要性、方法论、当前和潜在的未来应用，