VEGF-C信号通路调控人精原干细胞自我更新的作用与分子机制

The understanding of self-renewal of spermatogonial stem cells（SSC）is the core foundation to uncover the pathogenesis of male infertility. So far, very little is known about the process. Our previous RNA-Seq studies had predicted a series of novel genes to regulate SSC proliferation and self-renewal, and found that VEGF-C and its receptors possessed specific temporal and spatial expression characteristics. Further studies demonstrated that VEGF-C promoted mouse SSC proliferation in vitro. VEGF-C had recently been in focus for stem cell biology due to its critical roles in stem cells regulations and organs fate determination. However, its functions in spermatogenesis had been unknown. To this end, we will conduct this important project with the following aims: i) to identify the cellular locations and differential expression patterns of VEGF-C and its receptors in various male germ cells and Sertoli cells in human testis; ii) to explore the roles of VEGF-C signaling in mediating the self-renewal of human SSC; and iii) to uncover whether the AKT and ERK1/2 signaling transduction pathways are associated with the regulatory roles of VEGF-C in controlling human SSC self-renewal. This study is of great significance, because it could provide experimental evidence to underlie the mechanisms of spermatogenesis studies, uncovering novel genes and signaling mechanism regulating human spermatogenesis, and it may offer new targets for the diagnosis and treatment of male infertility.

人类精原干细胞(SSC) 自我更新的分子机制，是揭示男性不育发病机理的核心理论基础，但目前知之甚少。在前期转录组学研究中，课题组预测并验证了一系列人SSC特异表达且调控其增殖和自我更新的新基因，尤其证明血管内皮生长因子C （VEGF-C）及其受体在人精子发生过程中有特异时空表达特征，体外实验表明VEGF-C能够促进小鼠SSC增殖。VEGF-C调控干细胞命运与器官再生的研究不断受到关注，但其与精子发生相关研究从未见报道。本项目拟开展以下研究： 1）明确VEGF-C及其受体在人睾丸组织各种生殖细胞和支持细胞的定位与差异表达特征；2）探讨VEGF-C信号通路对人SSC自我更新的调控功能；3）揭示VEGF-C调控人SSC自我更新的AKT与ERK1/2信号转导机制。本研究将为阐明人类精子发生的调控机制提供实验依据，为男性不育的诊断与治疗提供新的理论基础与分子靶标。

人类精原细胞增殖与凋亡的分子机制，是揭示男性不育发病机理的核心理论基础，但目前知之甚少。在前期转录组学研究中，课题组发现血管内皮生长因子C （VEGFC）及其受体在人精子发生过程中有特异时空表达特征，体外实验表明VEGFC能够促进小鼠精原细胞增殖，但其与精子发生相关研究从未见报道。在本项目的资助下，本课题组进一步开展了下述工作：1）利用单细胞转录组测序技术分析了VEGFC及其受体在人睾丸组织各种细胞的定位与差异表达特征，并利用免疫组化进行了蛋白水平验证；2）在体外研究中证明，VEGFC信号可以激活MAPK和AKT，上调Cyclin D1蛋白，从而促进精原细胞的增殖并抑制其凋亡；3）发现在BPA(bisphenol A)这一典型环境污染物存在的情况下， VEGFC能够通过NRP2-BMI1通路保护精原干细胞；4）为解决VEGFC蛋白难以有效到达生精小管管腔内作用于SSC，课题组构建了VEGFC缓释纳米颗粒，通过输出小管注射给药的方式成功使化疗后生精衰竭小鼠恢复精子发生。综上所述，本项目揭示了VEGFC调控精原细胞增殖与凋亡平衡的分子机制，优化了精原细胞的体外培养与诱导分化的实验体系，最终为治疗生精衰竭导致的非梗阻性无精子症提供理论基础与实验依据。