Whiley Penny A F, Nathaniel Benedict, Stanton Peter G, Hobbs Robin M, Loveland Kate L
Centre for Reproductive Health, Hudson Institute of Medical Research, Clayton, VIC, Australia.
Department of Molecular and Translational Sciences, School of Clinical Sciences, Monash University, Clayton, VIC, Australia.
Front Cell Dev Biol. 2023 Jul 26;11:1237273. doi: 10.3389/fcell.2023.1237273. eCollection 2023.
Adult male fertility depends on spermatogonial stem cells (SSCs) which undergo either self-renewal or differentiation in response to microenvironmental signals. Activin A acts on Sertoli and Leydig cells to regulate key aspects of testis development and function throughout life, including steroid production. Recognising that activin A levels are elevated in many pathophysiological conditions, this study investigates effects of this growth factor on the niche that determines spermatogonial fate. Although activin A can promote differentiation of isolated spermatogonia , its impacts on SSC and spermatogonial function are unknown. To assess this, we examined testes of KO mice, which feature elevated activin A levels and bioactivity, and develop gonadal stromal cell tumours as adults. The GFRA1+ SSC-enriched population was more abundant and proliferative in KO compared to wildtype controls, suggesting that chronic elevation of activin A promotes a niche which supports SSC self-renewal. Intriguingly, clusters of GFRA1+/EOMES+/LIN28A- cells, resembling a primitive SSC subset, were frequently observed in tubules adjacent to tumour regions. Transcriptional analyses of KO tumours, tubules adjacent to tumours, and tubules distant from tumour regions revealed disrupted gene expression in each KO group increased in parallel with tumour proximity. Modest transcriptional changes were documented in KO tubules with complete spermatogenesis. Importantly, tumours displaying upregulation of activin responsive genes were also enriched for factors that promote SSC self-renewal, including , , and , indicating the tumours generate a supportive microenvironment for SSCs. Tumour cells featured some characteristics of adult Sertoli cells but lacked consistent SOX9 expression and exhibited an enhanced steroidogenic phenotype, which could arise from maintenance or acquisition of a fetal cell identity or acquisition of another somatic phenotype. Tumour regions were also heavily infiltrated with endothelial, peritubular myoid and immune cells, which may contribute to adjacent SSC support. Our data show for the first time that chronically elevated activin A affects SSC fate . The discovery that testis stromal tumours in the KO mouse create a microenvironment that supports SSC self-renewal but not differentiation offers a strategy for identifying pathways that improve spermatogonial propagation .
成年雄性生育能力依赖于精原干细胞（SSCs），精原干细胞会根据微环境信号进行自我更新或分化。激活素A作用于支持细胞和间质细胞，以调节睾丸发育和整个生命过程中的功能的关键方面，包括类固醇生成。认识到激活素A水平在许多病理生理条件下会升高，本研究调查了这种生长因子对决定精原细胞命运的微环境的影响。虽然激活素A可以促进分离的精原细胞的分化，但其对精原干细胞和精原细胞功能的影响尚不清楚。为了评估这一点，我们检查了基因敲除（KO）小鼠的睾丸，这些小鼠的激活素A水平和生物活性升高，成年后会发生性腺基质细胞瘤。与野生型对照相比，基因敲除小鼠中富含GFRA1 +精原干细胞的群体更加丰富且增殖能力更强，这表明激活素A的长期升高促进了一个支持精原干细胞自我更新的微环境。有趣的是，在肿瘤区域附近的小管中经常观察到GFRA1 + / EOMES + / LIN28A-细胞簇，类似于原始的精原干细胞亚群。对基因敲除肿瘤、肿瘤附近的小管和远离肿瘤区域的小管进行转录分析发现，每个基因敲除组中基因表达的破坏与肿瘤接近程度平行增加。在具有完整精子发生的基因敲除小管中记录到适度的转录变化。重要的是，显示激活素反应基因上调的肿瘤也富含促进精原干细胞自我更新的因子，包括、和，这表明肿瘤为精原干细胞产生了一个支持性的微环境。肿瘤细胞具有成年支持细胞的一些特征，但缺乏一致的SOX9表达，并表现出增强的类固醇生成表型，这可能源于维持或获得胎儿细胞身份或获得另一种体细胞表型。肿瘤区域也有大量内皮细胞、管周肌样细胞和免疫细胞浸润，这可能有助于支持相邻的精原干细胞。我们的数据首次表明，长期升高的激活素A会影响精原干细胞的命运。基因敲除小鼠的睾丸基质肿瘤创造了一个支持精原干细胞自我更新但不支持分化的微环境，这一发现为确定改善精原细胞增殖的途径提供了一种策略。
