髓源性抑制细胞对肝星状细胞的作用及机制研究

The activation and proliferation of hepatic stellate cells (HSC) is a central part in the development of liver fibrosis. Inhibition of HSC proliferation and induction of HSC apoptosis is the key to the treatment of liver fibrosis. It is reported that myeloid derived suppressor cells (MDSCs) have anti-liver-fibrosis effect. Our preliminary results also suggest that increased expression of MDSCs in patients with liver fibrosis, and MDSCs may promote HSC apoptosis, thus reduce or even reverse liver fibrosis. MDSC can release nitric oxide (NO) through inducible nitric oxide synthase (iNOS). Some literatures confirm that iNOS has a significant anti-fibrosis effect, promote the apoptosis of HSC by releasing NO, transfer NO to HSC by nanoparticles which can be used to treat liver fibrosis. In order to further clarify and explain the role and mechanisms of MDSCs on HSC, we use clinical specimens, analyze the correlation between MDSCs and liver fibrosis, separate MDSCs and HSC from liver tissue, in three aspects of cell, tissue and animal to clarify whether MDSCs release NO through iNOS to promote apoptosis and inhibit proliferation of activated HSC, thus exert anti-fibrosis effect. This study has important theoretical and practical significance and provides a new target for the treatment of liver fibrosis.

肝星状细胞（HSC）的活化和增殖是肝纤维化发生发展的中心环节，抑制HSC增殖、诱导HSC凋亡是治疗肝纤维化的关键。文献报道，髓源性抑制细胞（MDSCs）具有抗肝纤维化作用。我们预实验结果提示肝纤维化患者MDSCs表达增加，MDSCs可能促进HSC凋亡，从而减轻甚至逆转肝纤维化。MDSCs能够通过诱导型一氧化氮合酶（iNOS）释放一氧化氮（NO），一些文献证实iNOS具有显著的抗肝纤维化作用，释放的NO触发HSC凋亡，经纳米颗粒传递NO到HSC可以治疗肝纤维化。为了进一步明确并阐述MDSCs对于HSC的作用及相关机制，我们利用临床标本，分析MDSCs表达与肝纤维化的相关性，从肝组织分离MDSCs和HSC，在细胞、组织和动物三个层面来阐明MDSCs是否通过iNOS释放NO促进活化HSC凋亡、抑制HSC增殖，从而发挥抗纤维化作用。本研究具有重要的理论和实际意义，为肝纤维化的治疗提供新的靶点。

肝纤维化是多种病因所致的慢性肝损伤后的一种过度创伤修复反应，是慢性肝病转化为肝硬化和肝功能衰竭的必经阶段和共同病理基础。迄今为止临床上尚缺乏特异性针对肝纤维化的有效逆转或阻止其进展的药物。近年来，髓源性抑制细胞（MDSCs）受到广泛关注。它是一群具有强大免疫调控功能的髓系细胞群，通过多种机制参与机体的免疫应答，影响疾病的发生和发展。MDSCs在肿瘤免疫逃逸中存在“消极”作用，却在肝纤维化的发生发展中发挥着潜在的“积极”作用。我们通过收集临床标本，并与临床资料结合，发现粒细胞型MDSCs（G-MDSCs）在慢性乙型肝炎患者中表达增加，与肝纤维化（Fibroscan）存在负相关。通过BALB/C小鼠，CCL4腹腔注射进行肝纤维化造模，G-MDSCs尾静脉注射，及anti-Gr-1腹腔注射中和G-MDSCs等实验，证实G-MDSCs具有抗肝纤维化作用，可能通过PI3K-Akt通路实现。我们的结果具有重要的临床意义，除了解释了肝纤维化的发生机制，也为肝纤维化的治疗提供新的视角，有重要的临床应用价值。