分泌因子FSTL1介导间充质干细胞抗肝纤维化的调控新机制

Liver cirrhosis is the final pathological result of various chronic liver diseases. Mesenchymal stromal cell (MSC) therapies have been considered and shown to have potential in preventing progression to end-stage liver disease. However,the underlying mechanisms are far from being clarified. Recent studies have found hepatic stellate cells-based hepatic microenvironment is critical for MSCs directional migration and its anti-fibrotic function. TGF-β/BMP signaling may regulate this process. Our group previously found FSTL1, a TGF-β1 induced profibrotic glycoprotein, is significantly elevated in advanced versus early fibrosis stages patients. Meanwhile, our primary data indicate serum FSTL1 before stem cell transplantation is a potential correlation factor on the treatment effect. In MSCs therapy model, FSTL1 could participate in regulating MSCs migration and anti-fibrotic ability. We hypothesize that FSTL1 mediate cell-cell interaction between HSCs and MSCs and participate in the migration and anti-fibrotic function of MSCs. Using Fstl1 reporter mice and Fstl1 conditional knockout mice, in vivo cell lineage tracing and microscopic imaging techniques, this proposal is going to investigate Fstl1 cell lineage and the role of FSTL1 in facilitating MSCs migration during liver fibrosis; to further clarify the molecular mechanisms of FSTL1 in regulating anti-fibrotic ability. This study will improve the understanding of the molecular mechanisms and provide theoretical and experimental basic for MSCs therapy and its clinical use.

肝硬化是慢性肝病持续进展的共同病理表现，间充质干细胞（MSCs）移植极具治疗前景，但机制未明。新近发现，以肝星状细胞（HSCs）为核心的肝脏微环境可能是MSCs定向迁移、发挥效能的关键；TGF-β/BMP信号可能调控该过程。前期研究表明，FSTL1是TGF-β1诱导的促纤维化因子，其表达水平与肝纤维化程度呈正相关；FSTL1增高有利于临床干细胞移植后的治疗应答，治疗模型证实FSTL1可促进MSCs迁移、抗纤维化能力。我们推测，FSTL1可能介导了HSCs和MSCs相互作用，参与MSCs迁移、抗纤维化调控。本课题将利用Fstl1报告小鼠、条件敲除小鼠，结合谱系追踪、双光子活体成像技术，明确FSTL1的细胞来源及HSCs表达的FSTL1对MSCs肝脏定植的影响，研究FSTL1介导MSCs抗纤维化的分子机制，为阐明肝脏微环境影响MSCs抗纤维化的作用机理、提升MSCs疗效提供理论依据和实验基础。

肝硬化（liver cirrhosis）是由多种病因诱发的慢性肝病的终末期表现。间充质干细胞（mesenchymal stem cells，MSCs）作为最有可能替代肝移植的临床治疗手段，被广泛应用于抗纤维化基础研究和临床实验。尽管，MSCs移植在终末期肝纤维化的临床实验中有较显著治疗效果，但机制不清、疗效存在一定的个体差异性。静息状态下，MSCs并不具备免疫抑制、损伤修复的功能，这一特点提示MSCs 所处微环境对其疗效发挥起关键作用。最新研究结果提示，肝纤维化进展过程中以肝星状细胞为核心的复杂的肝脏局部微环境可能是影响间充质干细胞定向迁移、抗纤维化的关键因素。卵泡抑素样蛋白（Follistatin-like 1, FSTL1）是TGF-b1诱导的胞外分泌糖蛋白，多项研究表明FSTL1与肝纤维化进程密切相关；前期预实验结果发现，FSTL1水平影响肝硬化患者干细胞移植后的疗效；在肝纤维化的肝组织中主要由活化的星状细胞分泌。本项目主要研究了肝脏微环境中FSTL1水平对MSCs抗纤维化疗效的影响，进一步探究了FSTL1对MSCs免疫调节和定向迁移的影响和分子机制。经过研究，我们发现肝纤维化微环境中高水平FSTL1有利用MSCs发挥抗纤维化作用：一方面，FSTL1通过转录激活JAK/STAT1/IDO1信号轴，促进MSCs发挥免疫调节作用，抑制促炎型巨噬细胞的活性和数量，促进抑炎型巨噬细胞的活性和数量；另一方面，FSTL1可以通过转录激活JAK/STAT3/CXCR4信号轴，促进MSCs的定向迁移，增加干细胞在肝脏的定植来增强干细胞的抗纤维化作用。本项目的研究结果为阐明肝脏微环境影响MSCs 抗纤维化的作用机理、提升MSCs疗效、改良干细胞产品提供了重要的理论依据和实验基础。