Notch信号通路在维持肝血窦内皮细胞稳态中的作用机制研究

The change of liver sinusoidal endothelial cell (SEC) structure and function was involved in varieties of hepatic diseases and liver injuries. SEC homeostasis played a very important role in regulating liver structure and function. Previously, people thought SEC majorly originated from resident proliferation. However recently, we found specific SEC progenitor cells (SPC) also particiated into SEC turnover. Besides, we previously reported disruption of Notch/RBP-J signaling pathway, stimulated systematic endothelial cell (including SEC) related angiogenesis; resulted in abnormality of liver sinusoids; and regulated bone marrow derived endothelial progenitor cell mobilization and recruitment during liver regeneration. Thus, Notch/RBP-J pathway played essential role in regulating liver sinusoid structure and function. In this project, based on previous findings, we planed to explore how Notch/RBP-J pathway regulates SEC proliferation, apoptosis, differentiation and function, and the role of SPC in maintenance of SEC homeostasis. Whether some other signaling pathways crosstalked with Notch were involved in SEC homeostasis regulation will also be investigated in this project. Hopefully, we may finally find a brand new target to cope with hepatic diseases.

肝脏疾病及损伤多伴有肝血窦内皮细胞（SEC）结构和功能的改变，SEC 稳态对于维持正常肝脏结构和生理功能具有重要意义。以往认为SEC 主要来自原位增殖。课题组近期发现SEC 特异的祖细胞- - SPC，也参与SEC 的稳态维持，论文发表在J Clin Invest。课题组前期发现，阻断Notch/RBP-J 信号可致SEC 增殖，肝血窦结构异常改变，以及肝再生进程中骨髓内皮祖细胞动员、归巢的改变。因此，Notch/RBP-J 通路对于维系肝血窦的正常结构和功能具有重要作用，但Notch 信号对SPC 的调控及与SEC 的关系仍不清楚。本课题拟在前期研究基础上，深入探讨Notch/RBP-J 信号对SEC 增殖、凋亡、分化、功能和对其干、祖细胞调控的细胞生物学基础，阐明Notch/RBP-J 信号调控SEC 结构和功能稳态的分子机制及其与其他信号途径的相互作用，从而为肝病的治疗和干预提供新靶点。

肝血窦内皮细胞在调控肝脏稳态和疾病发生中具有重要作用。在本项目研究中，我们利用内皮特异性Notch信号过表达的小鼠模型，发现在内皮特异性Notch激活后，会造成肝脏稳态的破坏。Notch的活化还会导致肝血窦内皮细胞窗孔消失、基底膜增加，基因谱表达分析提示出现肝血窦内皮细胞的毛细血管化即去分化。同时，内皮特异性Notch信号过表达，还会加重四氯化碳诱导的肝脏纤维化。Notch活化可以阻断eNOS-sGC信号通路，利用sGC激活剂YC-1可以成功挽救Notch过表达后肝血窦内皮细胞的去分化状态。此外，内皮特异性Notch过表达还重塑了肝血窦内皮细胞的旁分泌谱系，通过下调Wnt2a、Wnt9b和HGF抑制肝细胞增殖，阻碍肝再生进程。Notch对Wnt2a和Wnt9b的调控同样依赖于eNOS-sGC通路，利用YC-1激活剂可以恢复Wnt2a的表达并挽救肝细胞增殖的障碍。总之，内皮特异性Notch信号激活会通过eNOS-sGC信号途径导致肝血窦内皮细胞去分化和肝纤维化的加重，同时改变肝血窦内皮细胞的旁分泌谱系而影响肝细胞增殖和肝再生。