肝血窦内皮细胞衰老对肝脏组织稳态和损伤修复的调控作用及机制研究

Cell senescence is closely linked to a variety of human diseases. Fatty liver, viral hepatitis, liver fibrosis, hepatocellular carcinoma and other liver diseases are accompanied by the senescence of liver cells. Liver sinusoidal endothelial cells (LSECs), the largest non-parenchymal subpopulation of the liver cell, are important effector cells for the maintenance of liver homeostasis and regulation of liver wound-healing（Duan JL etal, Hepatology, 2018, Epub）. In our recent study, we have found that SA-β-gal-positive senescent LSEC can be detected in the liver tissue of normal and liver injured mice. what role does this group of senescent LSEC play in the maintenance of liver homeostasis and regulation of liver wound-healing? How is its molecular mechanism? still not clear. In the current project, we seek to explore the contribution of senescence LSEC in liver homeostasis and liver wound-healing using the endothelium-oriented modification model, and explore the molecular regulation mechanism of endothelial-specific Notch signaling on its behavioral function. Thus providing an important theoretical basis for the supplement and perfection of the liver injury repair mechanism, and the diagnosis and treatment of aging-related liver diseases.

细胞衰老与多种人类疾病有密切关联。脂肪肝、病毒性肝炎、肝纤维化、肝细胞癌等肝脏疾病都伴随有肝脏细胞的衰老。肝血窦内皮细胞（LSEC）作为肝脏最大的非实质细胞亚群，是肝脏稳态维持和损伤修复调控的重要效应细胞（Duan JL etal, Hepatology, 2018, Epub）。我们前期研究发现，在正常和肝损伤小鼠的肝脏组织中，都可检测到SA-β-gal阳性的衰老LSEC，这群衰老的LSEC在肝脏稳态维持和损伤修复中发挥怎样的作用？其分子机制如何？尚不清楚。本课题拟利用内皮细胞特异性基因修饰小鼠模型，研究衰老LSEC在维持肝脏稳态和修复肝损伤中的细胞作用基础，并探讨内皮特异性Notch信号对其行为功能的分子调控机制。从而为肝脏损伤修复机制的补充完善及衰老相关肝脏疾病的诊断治疗提供重要理论依据。

肝脏是人体再生能力最强的实体器官，部分肝切除后剩余肝脏可恢复至原肝大小和重量。但肝再生晚期的血管重塑和肝功能恢复的调控机制尚不明确。Notch信号是血管发育、血管稳态维持和血管形成中的顶端细胞选择、周细胞募集调控的关键信号。我们提出Notch信号是否调控肝再生晚期的肝窦重塑？针对这一科学问题，我们利用内皮特异性Notch 信号激活（Cdh5-CreERT2 × Rosa26-STOPfloxed-N1ICD）小鼠，表型分析发现Notch信号激活会造成LSEC衰老，SA-β-gal活性和SASP表达显著升高。在部分肝切除小鼠模型中，我们发现在肝切除术后第14天肝窦重塑不完整、肝脏灌注障碍进而改变血流剪切力，血流剪切力参与内皮细胞分化、凋亡、增殖、老化等，申请人发现流体剪切力改变通过eNOS/NO信号通路诱导LSEC衰老，SA-β-gal活性及衰老相关分泌表型（Senescence Associated Secretory Phenotype, SASP）表达显著上调。Notch激活加剧肝再生晚期的细胞衰老，进而造成细胞增殖能力下降炎症增加，最终导致肝再生障碍。分子检测发现Notch信号可通过其下游靶基因Hes1直接抑制sirtuin 1的转录水平，进而影响p21和p16等衰老标志分子的表达，从而诱导LSEC衰老阻碍肝再生。另外，我们发现阻断Notch信号或过表达sirtuin 1可减少细胞衰老、促进肝细胞增殖和改善肝血窦重塑，进而促进肝再生。我们提出以衰老细胞为靶点，通过减少衰老细胞来改善肝损伤修复，为肝脏疾病治疗提供了新的思路和方向。