Impact of a supernumerary X-chromosome on testicular somatic cell function

Klinefelter综合征（KS; 47，XXY）是男性中最常见的性染色体畸变，导致性腺功能减退和不育，并常规用雄激素治疗。高达50%的患者存在残余精子发生，这可能会被睾酮（T）给药破坏。睾丸体细胞也受到影响：存在间质细胞（LC）增生，尽管睾丸内T水平正常，但血清T水平不足。睾丸血管化受损可能导致内分泌失调。XXY Sertoli细胞（SC）为分化的生殖细胞（GC）提供了一个小生境和支持，导致了局部精子发生，但它们的生理学受到这种疾病的影响。管周肌样细胞（PMC）在功能上也很重要，但它们在KS睾丸变性中的作用可能被低估。我们的首要目标是描绘一个多余的X染色体存在的睾丸体细胞功能。KS影响患者全身，我们将使用我们的41 XXY* 小鼠模型检查这种影响。我们从数百名患者和对照组中收集了临床数据、DNA和睾丸活检，从而能够从模型中翻译结果。即使升高的促黄体生成激素（LH）水平也是刺激不足的，可能是由于大LH分子的睾丸转运受阻。我们推测，LH受体（LHR）激动剂刺激可改善LH作用，增强类固醇反应，使血清T正常化。先前，处理了来自XXY* 小鼠和对照的分离的LC：我们发现i）激动剂具有高度活性，并且ii）XXY* LC响应更强。我们在小鼠41，XXY* 睾丸器官培养物中证实了这一点，表明激动剂可以恢复内分泌信号传导，这是一个在体外（人睾丸组织）和体内（41，XXY* 小鼠）受到挑战的假设。预期的结果可以使一种新的治疗刺激内源性T的生产和保护局灶性精子发生。单细胞RNA测序（scRNAseq）表明SC参与KS睾丸变性。PMC在维持局灶性精子发生和加速纤维化中发挥作用。我们假设，PMC和SC的条件受到影响，导致在一个褪色的“机会之窗”，以促进残余精子发生。我们将通过睾丸内移植eGFP小鼠的供体GC、模拟局灶性精子发生、scRNAseq转录组学方法和随后的生物信息学评估来挑战这一点。检测到的候选者将在来自具有局灶性精子发生的患者的睾丸活检中的蛋白质水平上进行翻译和验证。我们将在生殖生命的不同阶段分析PMC和SC，以及是否存在体细胞- GC相互作用。我们将深入了解染色体畸变对睾丸体细胞功能的影响，并获得临床高度相关的数据，用于开发KS的改进疗法。

Klinefelter syndrome (KS; 47,XXY) is the most frequent sex chromosomal aberration in men causing hypogonadism and infertility and is routinely treated with androgens. Up to 50% of patients show remnant spermatogenesis, which might be destroyed by testosterone (T) administration.The somatic testicular cells are also affected: Leydig cell (LC) hyperplasia is present and although intratesticular T levels are normal, serum T levels are insufficient. Impaired testicular vascularization is likely contributing to the endocrine disbalance. XXY Sertoli cells (SC) offer a niche and support for differentiating germ cells (GC), resulting in focal spermatogenesis but their physiology is affected by the disorder. Peritubular myoid cells (PMCs) are also functionally important but their role in the testicular degeneration in KS is likely underestimated. Our overarching aim is to delineate the testicular somatic cell function in the presence of a supernumerary X chromosome. KS affects the patients systemically and we will examine such effects using our 41 XXY* mouse model. We collected clinical data, DNA and testicular biopsies from several hundred patients and controls, enabling translation of results from the model. Even elevated Luteinising Hormone (LH) levels are stimulatory insufficient, likely due to hampered testicular transport of the large LH molecule. We hypothesize that LH receptor (LHR) stimulation by an agonist could improve LH action, enhance steroid response and normalize serum T. Previously, isolated LCs from XXY* mice and controls were treated: We found that i) the agonist is highly active and ii) XXY* LCs responded stronger. We confirmed this in murine 41,XXY* testicular organ culture indicating that the agonist can restore the endocrine signaling, a hypothesis to be challenged in vitro (human testicular tissues) and in vivo (41,XXY* mice). The expected results can enable a new treatment stimulating endogenous T production and protecting focal spermatogenesis. Single cell RNA sequencing (scRNAseq) indicated SCs to be involved in testis degeneration in KS. PMCs play a role in the maintenance of focal spermatogenesis and accelerated fibrosis. We hypothesize that PMCs and SCs are affected by the condition, resulting in a fading “window of opportunity” to foster remnant spermatogenesis. We will challenge this by intratesticular transplantation of donor GCs from eGFP mice, mimicking focal spermatogenesis, scRNAseq transcriptomic approaches, and subsequent bioinformatics assessment. The detected candidates will be translated and validated at the protein level in testis biopsies from patients with focal spermatogenesis. We will analyze PMCs and SCs during different phases of reproductive life and with regard to present or absent somatic – GC interactions. We will gain insights on chromosomal aberration effects on testicular somatic cell function and clinically highly relevant data for the development of improved therapies for KS.