Viral, T Cell, and Cytokine Determinants of Hepatic Stellate Cell Activation

在美国和欧洲，慢性丙型肝炎病毒(HCV)感染已成为肝脏相关发病率和死亡率的主要原因。慢性丙型肝炎进展为晚期肝纤维化，最后发展为肝硬变，是肝功能衰竭和原发性肝癌发展的关键预测因素。然而，在平均20年的感染后，只有20%-30%的患者发展为肝硬变，而其他患者进展较慢或根本没有进展。肝星状细胞和肌成纤维细胞是肝纤维化的效应细胞，在进展过程中导致细胞外基质成分过度沉积，似乎对纤维化的反应一致。 刺激物。相反，丙型肝炎病毒感染的肝细胞和宿主对丙型肝炎病毒的免疫应答似乎是决定肝星状细胞和肌成纤维细胞(统称为肝星状细胞)激活状态的主要因素，很可能是通过释放促纤维化因子来实现的。此外，病毒的基因型和变异体(准种)可间接(通过与免疫系统的相互作用)或直接(通过感染的肝细胞内的改变)刺激肝星状细胞的激活，从而促进纤维化的形成和发展。此外，诸如肝脏脂肪变性和氧化应激增强等公认的丙型肝炎进展辅助因素的机制作用在很大程度上还没有被探索。为了模拟肝星状细胞的细胞外环境，我们将使用来自丙型肝炎病毒复制的肝细胞系以及来自进展缓慢和快速的患者的CD4+，CD8+和NK T细胞亚群的条件培养液来检验这样的假设：1.复制丙型肝炎病毒的肝细胞系释放促纤维化因子，驱动肝星状细胞的激活，以及 这样释放的一个主要的促纤维化因子是TGFbeta1。2.不同的丙型肝炎病毒(1b型vs.2b型)和某些准种(定义为重要序列区域的突变，即核心、NS4B和NS5A)在复制子细胞或核心、NS4B/NS5A转染的肝细胞中诱导不同水平的促纤维化因子。3.丙型肝炎病毒诱导的肝细胞脂质代谢改变和氧化应激导致转化生长因子-β1等促纤维化因子的释放增加。4.慢性丙型肝炎患者慢性丙型肝炎关键炎症细胞(CD4+、CD8+和NK T细胞)释放的细胞因子谱在进展快与慢的患者中更易纤维化，并确定这些T细胞亚群释放的关键纤维化因子。 更好地了解丙型肝炎病毒在肝脏中诱导的纤维化反应，以及它与其他外在和内在的促纤维化触发因素和途径的合作或相互作用，将有助于更好地了解丙型肝炎病毒肝病的进展，并为慢性丙型肝炎量身定做新的抗肝纤维化治疗方法。

Chronic hepatitis C virus (HCV) infection has become a major cause of liver related morbidity and mortality in the USA and Europe. Progression of chronic hepatitis C to advanced liver fibrosis and finally cirrhosis is the key predictor of liver failure and the development of primary liver cancer. However, cirrhosis develops in only 20-30% of patients after a mean of 20 years of infection, while others progress more slowly or not at all. Hepatic stellate cells and myofibroblasts, the effector cells of liver fibrosis that are responsible for excess deposition of extracellular matrix components during progression, seem to respond uniformly to fibrogenic stimuli. On the contrary, HCV infected hepatocytes and the host's immune response to HCV appear to be major factors that determine the activation state of hepatic stellate cells and myofibroblasts (collectively termed hepatic stellate cells), most likely via release of profibrogenic factors. In addition, viral genotype and variants (quasispecies) may indirectly (via interaction with the immune system) or directly (via alterations within the infected hepatocytes) stimulate hepatic stellate cell activation and thus fibrogenesis and progression. Furthermore, the mechanistic role of well established cofactors of progression in HCV liver disease, such as hepatic steatosis and enhanced oxidative stress is largely unexplored. To mimic the extracellular environment of hepatic stellate cells, we will use conditioned media from a spectrum of HCV replicating hepatocytic cell lines and from CD4+, CD8+ and NK T cell subsets derived from slow and rapid progressor patients to test the hypothesis that 1. hepatocytic cell lines with replicating HCV release profibrogenic factors that drive activation of hepatic stellate cells, and that a major profibrogenic factor thus released is TGFbeta1. 2. different HCV genotypes (type 1b vs. 2b) and certain quasispecies, defined as mutations in sequence regions of importance, namely in Core, NS4B and NS5A, elicit different levels of profibrogenic factors in the replicon cells or in Core, NS4B/NS5A transfected hepatocytic cells. 3. HCV induced hepatocyte alterations in lipid metabolism and oxidative stress lead to enhanced release of TGF-beta1 and other profibrogenic factors. 4. the cytokine profile released by key inflammatory cells in chronic HCV infection (CD4+, CD8+ and NK T cells) is more fibrogenic in patients with rapid vs. slow progression, and identify the key fibrogenic factors released by these T cell subsets. It is expected that a better understanding of the HCV-induced fibrogenic response in the liver and its cooperation or interaction with other extrinsic and intrinsic profibrogenic triggers and pathways will lead to a better understanding of HCV liver disease progression and to novel antifibrotic treatments tailored to chronic hepatitis C.