肝血窦内皮细胞可塑性对肝脏组织稳态的调控作用、机制和对肝纤维化的影响

Liver sinusoidal endothelial cells (LSECs) maintain hepatic microcirculation on one hand, and regulate hepatocytes, hepatic stellate cells and hepatic macrophages (Kupffer cells) on the other, therefore serve as a hub in maintaining liver homeostasis. However the molecular mechanisms controlling LSEC stability and communications with other hepatic cells have not been elucidated. In our recent study, by using gene-modified mouse models to specifically block or activate Notch signaling in endothelial cells, we have found that Notch signaling regulates not only the dedifferentiation (capillarization), transdifferentiation (EndMT) and senescence of LSECs, but also the proliferation, differentiation and apoptosis of hepatocytes and liver nonparenchymal cells through altered angiocrine factors, leading to disrupted liver homeostasis. However, whether various differentiation states of LSECs participate in maintaining liver homeostasis and the underlying molecular mechanisms have not been completely unveiled. In the current project, we will ① through establishing the transcriptome including non-coding RNA profiles of LSECs that have been accomplished, to reveal the molecular mechanisms for Notch signaling to regulate the dedifferentiation, transdifferentiation and senescence of LSECs; ② to unveil the influences of LSEC with different status on the proliferation, differentiation and function of hepatocytes and other liver non-parenchymal cells; ③ to elucidate the molecular mechanisms for LSECs with different status to regulate hepatocytes and other liver non-parenchymal cells, focusing on their angiocrine and exosome-mediated effects; and ④ to investigate the effects and molecular mechanisms for LSECs with different status in the pathogenesis of hepatic homeostasis-related human diseases such as liver fibrosis. These studies will establish an LSEC-centered cellular and molecular network for the maintenance of liver homeostasis, and provide new insights into the pathological mechanisms of related human diseases to set up new targets and strategies for their precision intervention.

肝血窦内皮细胞(LSEC)不仅维持肝脏微循环，还通过旁分泌调控肝细胞、肝星形细胞和肝巨噬细胞等，是肝脏稳态维持的关键结点。我们最近发现，在内皮细胞中通过条件性基因敲除阻断/激活Notch信号，可影响LSEC去分化(毛细血管化)、转分化和老化，同时改变其旁分泌谱进而影响肝脏稳态。那么，LSEC的不同分化状态对肝脏稳态有何不同影响？其分子机制如何？本项目拟：①在已完成转录组分析的基础上，阐明Notch信号调控LSEC可塑性的分子机制；②揭示LSEC不同分化状态对肝细胞和肝非实质细胞的增殖、分化和功能状态的影响；③分析不同分化状态的LSEC影响肝稳态的分子机制，尤其是其旁分泌谱和外泌体改变；④深入探讨LSEC不同分化状态通过肝稳态失衡调控肝纤维化的作用和分子机制。本研究不仅将在分子调控和细胞通讯层面建立基于内皮细胞的肝稳态维持网络，还可加深对相关疾病机制的认识并为其精准干预提供靶点和策略。

肝脏是最大的实体器官和代谢中枢，其组织结构包括肝细胞和肝血窦内皮细胞（LSEC）、肝脏巨噬细胞、肝星形细胞。LSEC在解剖上与各肝脏细胞亚群接触，在功能上维持肝脏微循环，并通过旁分泌调控其他肝脏细胞亚群，是肝脏稳态的关键结点。本项目以Notch信号通路为切入点，探讨LSEC命运可塑性的分子机制；揭示LSEC . 不同分化状态对肝脏细胞亚群的增殖分化和功能状态的影响及其分子机制；深入探讨LSEC不同分化状态通过肝稳态失衡调控肝纤维化的作用和意义。.项目从三个方面完成了预定的研究内容。首先，全面揭示了在成年小鼠内皮细胞中诱导Notch信号激活/阻断后，LSEC可塑性的改变；证实细胞因子、血流剪切力等因素促进LSEC的Notch信号活化，而Notch活化推动LSEC命运的序贯转变，包括去分化（毛细血管化）、转分化（内皮间充质转变）和老化；这些细胞命运转变可以参与肝血窦的生理性重构，但也可改变LSEC的细胞因子、细胞外基质分子、黏附分子等旁分泌谱而损伤肝细胞稳态。在分子机制上，eNOS-sGC通路介导了大部分Notch信号对LSEC的调控作用。第二，探讨了Notch信号上下游分子对内皮细胞的调控和机制。证实SPEN通过pRNA调控核糖体生物合成，进而调控内皮细胞增殖和功能；发现TMEM215感受血流剪切力变化、通过线粒体-内质网膜结合调控内皮细胞生存和血管重塑的作用和机制；证实Notch信号通过一组miRNAs调控MYC，进而调控内皮细胞增殖和动脉化。第三，证实Notch信号调控LSEC转分化为间充质样细胞直接参与肝纤维化中细胞外基质的沉积，阻断LSEC的Notch信号，可以有效降低动物模型的肝纤维化水平，尤其是肝小叶内细胞外基质的沉积，促进肝细胞的增殖和肝功的恢复。本项目在分子调控和细胞间通讯层面完善了基于LSEC的肝稳态网络，加深了对相关肝病机制的认识，为其精准干预提供了靶点和策略。