调节性T细胞通过调节MMP/TIMP平衡参与维持肝纤维化状态的机制

Liver fibrosis is the final common pathway of majority chronic liver disease, and the ideal treatment is lack now, the main reason is incomplete understanding of the related to the occurrence and development mechanism. Regulatory T cells (Tregs) mediates immune tolerance, and enhanced Tregs are expressed in patients with liver fibrosis due to various reasons, however, its specific role in liver fibrosis is few reported. In our preliminary study, when depleting Tregs in mice with liver fibrosis, the degree of fibrosis was reduced, and accompanied by down-regulation of TIMP1. Therefore, we believe Tregs are involved in the maintenance of liver fibeosis, and further proposed hypothesis: the up-regulated Tregs influenced the balance of MMP/TIMP secreted by hepatic stellate cells (HSCs), and inhibited MMPs by up-regulating TIMPs to reduce the collagen degradation, maintain the state of liver fibrosis. The project from the perspective of liver immune and fibrinolytic mechanism, focused on the mechanism of fibrolysis by depleting Tregs and the influence on MMPs and TIMPs in liver fibrosis mice, by means of MMP knockout and TIMP blocking, and primary co-culture of Tregs and HSCs to address the possible mechanisms of Tregs involved in maintaining liver fibrosis.

肝纤维化是多数慢性肝病的最后共同途径，目前缺乏较理想的治疗手段，主要原因是对其发生发展的相关机制认识不全面。调节性T细胞（Tregs）介导免疫耐受，多种原因所致的肝纤维化均伴有Tregs升高，但其在肝纤维化中扮演的角色和机制鲜有报道。我们研究发现：降低肝纤维化小鼠体内Tregs水平，其纤维化程度减轻，并伴有TIMP1下调。因此我们认为Tregs参与肝纤维化状态的维持，并进一步提出假说：Tregs的升高可能影响肝星状细胞（HSCs）分泌MMPs/TIMPs平衡，通过上调TIMPs抑制MMPs活性，减少胶原降解，维持肝纤维化。本项目从肝脏免疫角度和纤维溶解机制入手，以肝纤维化小鼠模型为基础联合MMP基因敲除和TIMP封闭技术，观察下调 Tregs后肝纤维化的变化和对MMPs和TIMPs的影响，并结合Treg与HSCs 共培养的细胞实验，明确Treg参与维持肝纤维化状态的可能机制。

肝纤维化是多数慢性肝病的最后共同途径，目前缺乏较理想的治疗手段，主要原因是对其发生发展的相关机制认识不全面。调节性T细胞（Tregs）介导免疫耐受，多种原因所致的肝纤维化均伴有Tregs升高，但其在肝纤维化中扮演的角色和机制鲜有报道。我们的研究针对这一问题，采用抗体封闭技术降低肝纤维化小鼠体内Tregs水平，发现其纤维化程度减轻，并伴有MMPs/TIMPs平衡向MMP方向移动。由于肝内星状细胞（HSCs）是分泌MMP和TIMP的主要细胞，因此我们将小鼠肝内的Tregs和HSCs分离并进行原代共培养，发现上清中MMP9和TIMP1的含量明显高于单独培养的HSCs，尤其是TIMP1增加明显，表明Tregs可以促进MMP9和TIMP1的分泌。当用TGF-β抗体孵育后，共培养系统中TIMP1下降明显。因此，我们认为肝纤维中增加的Tregs通过分泌大量的TGF-β，上调TIMPs抑制MMPs活性，影响HSCs分泌的MMPs/TIMPs平衡,减少胶原降解，维持肝纤维化状态，甚至加重发展为肝硬化。本研究从动物整体水平和细胞水平，证明了Tregs参与维持肝纤维化的作用和可能的机制，增加了我们对肝纤维化的形成原因的认识，为治疗提供新的思路和实验依据。