The role of testicular peritubular cells in human testicular ageing

与年龄相关的人类睾丸形态和功能变化包括内分泌功能降低和精子发生受损。潜在的机制尚不清楚，但建造精管壁的细胞可能起作用。在衰老和体视学研究过程中，小管壁发生纤维化变化，提示睾丸小管周围细胞（TPCs）数量减少。重要的是，与其他人类睾丸细胞相比，人类TPCs （HTPCs）可用于细胞研究，并且不断发展的见解将其确定为人类睾丸中的核心角色。特别是，它们通过分泌因子参与睾丸中的旁分泌相互作用，并可能有助于精子发生过程/精子干细胞生态位。它们负责精子在睾丸内的运输，并可能为间质细胞群提供前体。我们对HTPCs的初步研究表明，在培养中繁殖时，它们会老化。细胞复制性衰老，即分裂能力降低，伴随着细胞大小的增加，β -半乳糖苷酶（ß-Gal）的表达和雄激素受体水平的降低，表明htpc功能和产物的其他未知变化。我们假设这也发生在人类和长寿的非人类灵长类动物身上。htpc老化的结果可能共同导致男性睾丸功能的年龄相关性下降。建议通过HTPCs的研究和非人类灵长类动物模型的使用来探索睾丸衰老的机制。因此，为了验证我们的假设，我们计划(1)使用衰老前和衰老的htpc进行一系列研究。衰老细胞的细胞和分子特征包括一个全面的分泌组谱，以定义衰老相关的分泌表型（SASP），并分析体外衰老的后果。分泌因子改变的作用将在细胞培养研究中探讨。功能分析包括收缩性分析和检查平滑肌标记以及干细胞特征。(2)将对年轻成人和老年健康的非人类灵长类动物（普通狨猴（Callithrix jacchus）和恒河猴（Macaca mulatta））的睾丸样本进行互补的体外和原位研究。这些可翻译的动物模型在很大程度上排除了混杂的健康问题，并使我们能够区分与年龄和疾病相关的睾丸变化，这在人类中是不完全可能的。包括全转录组分析和睾丸形态的研究，将通过对青壮年和老年Callithrix jacchus的分离ptc的研究来补充。我们期望我们项目的结果将阐明睾丸老化的机制。所获得的见解可能会导致新的方法来拦截睾丸老化的后果。

Age-associated morphological and functional changes of the human testis include reduced endocrine functions and impaired spermatogenesis. The underlying mechanisms are not well known, but the cells building the walls of seminiferous tubules may play a role. Hints of an involvement come from the fibrotic changes that occur in the tubular wall during ageing and stereological studies, which indicate that these testicular peritubular cells (TPCs) decrease in numbers. Importantly, in contrast to other human testicular cells, human TPCs (HTPCs) are accessible for cellular studies and the evolving insights identify them as a central player in the human testis. In particular, via secreted factors they participate in paracrine interactions in the testis and may contribute to the process of spermatogenesis /the spermatogonial stem cell niche. They are responsible for intratesticular transport of sperm and may provide precursors for the Leydig cell population. Our preliminary studies in HTPCs show that when propagated in culture, they age. Cellular replicative senescence, i.e. reduced ability to divide, is accompanied by increases in cell size, expression of beta-galactosidase (ß-Gal) and reduced levels of androgen receptors, indicative of other unknown changes in HTPC-functions and products. We hypothesize that this also occurs in vivo in man and in long-lived non-human primates. Consequences of HTPC-ageing collectively may contribute to the age-associated decline of testicular functions in man. The study of HTPCs and the use of translational non-human primate animal models are suggested to explore mechanisms of testicular ageing. Thus, to test our hypothesis we plan (1) a series of studies using pre-senescent and senescent HTPCs. Cellular and molecular characterization of senescent cells include a comprehensive secretome profile to define the senescence-associated secretory phenotype (SASP) and to analyze consequences of in vitro ageing. Actions of altered secretory factors will be explored in cell culture studies. Functional assays include contractility assays and examination of smooth muscle markers as well as stem cell characteristics. (2) Complementary in vitro and in situ studies in testicular samples from young adult and old, yet healthy non-human primates (Common marmoset monkey (Callithrix jacchus) and Rhesus monkey (Macaca mulatta)) will be performed. These translational animal models largely rule out confounding health-issues and allow us to discriminate between age- and illness-associated changes of the testis, which is not entirely possible in humans. Studies involving whole transcriptome analyses, and testicular morphology, will be complemented by the study of isolated PTCs from young adult and old Callithrix jacchus. We anticipate that the results of our project will elucidate mechanisms of testicular ageing. The insights gained may lead to novel approaches to intercept testicular consequences of ageing.