上皮-间叶转化在肝纤维化发病中的作用研究进展

上皮-间叶转化（EMT）是一个发生在胚胎时期的生理过程。研究发现,一旦肝脏发生损伤,其损伤部位的上皮样细胞,如肝星状细胞（HSC）,可通过EMT转变为肌成纤维样细胞（MFLC）,同时诱导细胞外基质（ECM）降解/合成功能失调。最近研究表明,肝脏上皮源性细胞（如肝细胞、胆管细胞和肝卵圆细胞）也可通过EMT转化为MFLC,深入研究EMT的分子调控机制可能成为肝纤维化治疗的新靶点。现将EMT在肝纤维化发病中的作用研究进展综述如下。     

上皮间质转化相关信号通路在肝纤维化中作用的研究进展

肝脏细胞上皮间质转化(EMT)是指在慢性肝损伤的微环境下上皮细胞失去原有特性而获得成纤维细胞典型特征的病理过程。EMT最终将导致肝纤维化。多种信号因子和多条信号通路参与EMT过程,研究表明,这些通路之间并不是独立存在的,相互之间存在紧密联系。近年来,靶向治疗已经成为肝纤维化治疗的研究热点之一,信号通路的研究为肝纤维化的靶向治疗提供了重要依据。     

炎症在肝纤维化中的作用

慢性肝损伤引起的炎症反应是肝纤维化发生发展的主要病理因素。在肝纤维化发展的过程中,大量炎症信号被激活,促使肝星状细胞向肌成纤维细胞转化,最终导致肝脏中细胞外基质的大量分泌和沉积,形成瘢痕组织。本文综述了肝星状细胞、Kupffer细胞、炎症小体、炎症信号通路等在肝纤维化过程中的作用,以对临床诊断和治疗提供参考。     

Hippo/YAP参与肝纤维化发生发展的作用机制

多种病因引起肝脏微环境的破坏而致肝组织结构功能丧失,启动肝纤维化进程,主要以肝星状细胞(HSC)活化为肌成纤维细胞,分泌大量以胶原为主的细胞外基质(ECM)为特征表现。虽然目前对抗肝纤维化机制的研究已有很多,但仍缺乏有效的靶点药物应用于临床,近年来关于抗肝纤维化的研究多集中在肝纤维化进展期的干预,而忽略了早期肝纤维化的具体机制如何。最近关于Hippo信号在肝纤维化中的研究逐渐增多,集中于核心转录因子Yes相关蛋白(YAP)在早期活化HSC中的表达,及该通路调控HSC的状态,本文主要介绍了Hippo/YAP通路参与调控肝纤维化早期及进展期的作用,简述了调控核心因子YAP的稳定表达与核转位可逆转肝纤维化的潜在作用,表明了该通路可为临床治疗提供新的方向及靶点。     

上皮-间叶转化在肝纤维化中调控机制研究进展

肝纤维化是各种不同病因慢性肝损伤疾病的共同病理转归,其发生机制目前仍未十分明确。近年研究发现,肝脏细胞如肝星状细胞、肝细胞、胆管细胞和肝卵圆细胞等均能发生上皮-间叶转化(EMT),成为肌成纤维样细胞参与肝纤维化发生。TGF-β/Smad、Hedgehog、MAPK、磷脂酰肌醇3-激蛋白激酶B等途径的信号通路激活是EMT发生的重要正向调节机制,抑制这些信号途径能逆转EMT,改善肝纤维化。深入研究EMT的分子调控机制可能成为肝纤维化治疗的新靶标。     

RhoA在肝纤维化发生与发展中的作用

肝纤维化是由各种慢性肝损害所导致的病理过程,主要表现为大量的细胞外基质沉积或瘢痕形成.肝星状细胞(hepatic stellate cells,HSCs)以及门脉成纤维细胞(portal fibroblasts,PFs)向肌成纤维细胞(myofibroblasts)转化,是生成细胞外基质的关键步骤.RhoA主要功能是调控细胞骨架,参与了HSCs/PFs活化的调节,具有明显的促纤维化作用.本文就该信号通路在肝纤维化发生、发展中作用的研究进展作一综述.     

炎症性肠病肠壁纤维化机制研究进展

肠壁纤维化是炎症性肠病(IBD)常见的晚期并发症,其是一个慢性进展性过程,特点为细胞外基质(ECM)的过度沉积,导致肠壁增厚、肠腔狭窄。肠壁纤维化的形成机制尚不十分清楚,可能涉及慢性炎症与间质细胞(成纤维细胞、肌成纤维细胞)、上皮细胞与内皮细胞的转化(通过EMT和EndoMT)、多种细胞因子之间的相互作用等。对肠壁纤维化的细胞和分子机制的研究可为寻找新的IBD治疗方案提供思路。     

整合素β1家族参与心肌纤维化发生的关键细胞事件:进展与契机

心肌纤维化是以成纤维细胞分泌的胶原蛋白等细胞外基质过度沉积为特征的心血管疾病晚期表现。整合素β1作为一种跨膜黏附分子,在"成纤维细胞-细胞外基质"之间进行力学信号和生化信号的双向转导,传递着促进纤维化和保护心肌组织的双重信息,进而影响成纤维细胞增殖、分化、迁移、分泌等导致心肌纤维化的关键性细胞事件。现就整合素β1及其相关蛋白在上述细胞事件中发挥的信号传递机制做一综述,并探讨以整合素β1及其相关蛋白为靶标的心肌纤维化治疗契机。     

肝星状细胞活化的关键路径

肝星状细胞（HSC）为肝纤维发生发展中心环节,活化状态HSC的凋亡是纤维化的关键特征。HSC激活转变为肌成纤维细胞（MFC）表型,收缩、增生,分泌胶原蛋白和其他细胞外基质（ECM）参与肝内结构的重建,通过集成信号网络调节ECM的沉积从而促进纤维化或者修复损伤。肝纤维化进展和逆转都需要特定信号通路,了解其在肝损伤中如何互动和演变对揭示肝纤维发生发展的复杂机制尤为关键。     

Sestrin2在不同疾病纤维化过程中的作用研究进展

<正>成纤维细胞的过度增殖和大量细胞外基质的沉积是纤维化的主要病理特征,Sestrin2(Sesn2)是高度保守的应激反应蛋白Sestrin家族的一员,具有抗氧化活性。最近研究发现Sesn2在诸多器官纤维化发生发展过程中起到重要调节作用。本文就Sesn2在肺脏、肝脏、肾脏、心脏等常见器官纤维化中的作用及其可能的分子机制做一综述,以期为抗纤维化治疗提供新的分子靶点。1纤维化概述纤维化是以成纤维细胞过度增殖和大量细胞外基质     

Therapeutic strategies against TGF-beta signaling pathway in hepatic fibrosis.

Hepatic fibrosis is the common wound-healing response to chronic liver injury. In this process, activation of hepatic stellate cells is characteristic of cell proliferation and migration, production of collagen and other extracellular matrix (ECM) molecules, and contraction after transforming into myofibroblasts. It has been shown that the fibrogenic process is prominently regulated by transforming growth factor-beta1 (TGF-beta1) and that the specific blockade of TGF-beta1/Smad3 signaling may therapeutically intervene the fibrosis of various tissues. In this review, we attempt to integrate recent advances in the understanding of the mechanisms underlying TGF-beta1/Smad3 pathway modulation of ECM gene expression in the context of liver fibrosis, discuss intervention strategies targeting the blockade of related signal pathways, and look into novel ways to the safe and efficacious prevention and treatment of hepatic fibrosis.     

Recent advancement of molecular mechanisms of liver fibrosis

Liver fibrosis occurs in response to any etiology of chronic liver injury including hepatitis B and C, alcohol consumption, fatty liver disease, cholestasis, and autoimmune hepatitis. Hepatic stellate cells (HSCs) are the primary source of activated myofibroblasts that produce extracellular matrix (ECM) in the liver. Various inflammatory and fibrogenic pathways contribute to the activation of HSCs. Recent studies also discovered that liver fibrosis is reversible and activated HSCs can revert to quiescent HSCs when causative agents are removed. Although the basic research for liver fibrosis has progressed remarkably, sensitive and specific biomarkers as non‐invasive diagnostic tools, and effective anti‐fibrotic agents have not been developed yet. This review highlights the recent advances in cellular and molecular mechanisms of liver fibrosis, especially focusing on origin of myofibroblasts, inflammatory signaling, autophagy, cellular senescence, HSC inactivation, angiogenesis, and reversibility of liver fibrosis.     

Transforming growth factor-beta and hepatocyte transdifferentiation in liver fibrogenesis

Currently, hepatic stellate cells (HSC) are thought to be the major fibrotic precursor cells that transdifferentiate to fibrogenic, extracellular matrix producing myofibroblasts in inflammatory liver tissue upon transforming growth factor-beta (TGF-beta) signaling, whereas hepatocytes are thought to respond with apoptosis to this cytokine. Starting out from in vitro experiments with primary hepatocyte cultures and immortalized AML-12 cells, TGF-beta signaling in this cell type was assessed and apoptosis was found to be only a minor effect. Instead, hepatocytes undergo epithelial mesenchymal transition (EMT), a physiological process in embryogenesis and of relevance for cancerous cell transformation. In injured liver, however, this process contributes to the promotion of fibrosis. Already after a few days of culture, hepatocytes lose their epithelial honeycomb-like shape towards a fibroblast-like phenotype. We could demonstrate by microarray analysis that stimulation of hepatocytes with TGF-beta regulates the expression of genes involved in EMT and fibrosis. Among these were, for example, Snail, a known mediator of EMT, and connective tissue growth factor (CTGF), a strong inducer of fibrosis. In a mouse model, hepatocyte-specific overexpression of Smad7 was able to blunt a fibrogenic response after CCl(4) intoxication. These results emphasize the dynamic nature of liver fibrosis, challenge the paradigm of HSC as a crucial source of liver myofibroblasts and hint towards a prominent role for hepatocytes in liver fibrogenesis.     

诱导活化肝星状细胞凋亡主要信号通路的研究进展

肝纤维化是各种病因引起的肝脏慢性进行性的病理过程,肝纤维化时细胞外基质(ECM)合成大于降解导致ECM在肝内大量沉积。肝星状细胞(HSC)的激活、转化并产生分泌大量ECM是肝纤维化形成的关键环节。而通过诱导活化的HSC发生凋亡是逆转肝纤维化的重要手段之一。就主要的凋亡信号通路:死亡受体通路、线粒体通路、内质网通路、神经生长因子通路进行一一阐述。指出了对活化HSC的凋亡途径进行选择性的药物干预有望发挥抗肝纤维化的作用。     

Hypoxia stimulates hepatocyte epithelial to mesenchymal transition by hypoxia‐inducible factor and transforming growth factor‐β‐dependent mechanisms

Background/Aims: During development of liver fibrosis, an important source of myofibroblasts is hepatocytes, which differentiate into myofibroblasts by epithelial to mesenchymal transition (EMT). In epithelial tumours and kidney fibrosis, hypoxia, through activation of hypoxia‐inducible factors (HIFs), is an important stimulus of EMT. Our recent studies demonstrated that HIF‐1α is important for the development of liver fibrosis. Accordingly, the hypothesis was tested that hypoxia stimulates hepatocyte EMT by a HIF‐dependent mechanism. Methods: Primary mouse hepatocytes were exposed to room air or 1% oxygen and EMT evaluated. In addition, bile duct ligations (BDLs) were performed in control and HIF‐1α‐deficient mice and EMT quantified. Results: Exposure of hepatocytes to 1% oxygen increased expression of α‐smooth muscle actin, vimentin, Snail and fibroblast‐specific protein‐1 (FSP‐1). Levels of E‐cadherin and zona occludens‐1 were decreased. Upregulation of FSP‐1 and Snail by hypoxia was completely prevented in HIF‐1β‐deficient hepatocytes and by pretreatment with SB431542, a transforming growth factor‐β (TGF‐β) receptor inhibitor. HIFs promoted TGF‐β‐dependent EMT by stimulating activation of latent TGF‐β1. To determine whether HIF‐1α contributes to EMT in the liver during the development of fibrosis, control and HIF‐1α‐deficient mice were subjected to BDL. FSP‐1 was increased to a greater extent in the livers of control mice when compared with HIF‐1α‐deficient mice. Conclusions: Results from these studies demonstrate that hypoxia stimulates hepatocyte EMT by a HIF and TGF‐β‐dependent mechanism. Furthermore, these studies suggest that HIF‐1α is important for EMT in the liver during the development of fibrosis.     

促纤维化因子在肝纤维化发生中的作用研究进展

肝纤维化是多种病因所致的慢性肝损伤的一种创伤愈合反应,持续的炎症与纤维形成最终导致肝硬化。肝星状细胞（HSC）是肝纤维化的主要生成细胞,肝脏内细胞外基质（ECM）的过度沉积是其主要功能。各种促纤维化因子如血管紧张素-II（AngII）、血小板衍生生长因子（PDGF）、血管内皮生长因子（VEGF）、转化生长因子-β（TGF-β）、瘦素、结缔组织因子等可与HSC表面上相应的受体结合,并激活相应的信号通路,进而导致HSC的激活、增殖,ECM过度沉积,引起肝纤维化形成。因此,了解各种促纤维化因子与肝纤维化的关系,可为抗纤维化的科学研究及临床治疗提供理论依据。     

Liver fibrogenesis and the role of hepatic stellate cells: New insights and prospects for therapy

Hepatic fibrosis is a wound-healing response to chronic liver injury, which if persistent leads to cirrhosis and liver failure. Exciting progress has been made in understanding the mechanisms of hepatic fibrosis. Major advances include: (i) characterization of the components of extracellular matrix (ECM) in normal and fibrotic liver; (ii) identification of hepatic stellate cells as the primary source of ECM in liver fibrosis; (iii) elucidation of key cytokines, their cellular sources, modes of regulation, and signalling pathways involved in liver fibrogenesis; (iv) characterization of key matrix proteases and their inhibitors; (v) identification of apoptotic mediators in stellate cells and exploration of their roles during the resolution of liver injury. These advances have helped delineate a more comprehensive picture of liver fibrosis in which the central event is the activation of stellate cells, a transformation from quiescent vitamin A-rich cells to proliferative, fibrogenic and contractile myofibroblasts. The progress in understanding fibrogenic mechanisms brings the development of effective therapies closer to reality. In the future, targeting of stellate cells and fibrogenic mediators will be a mainstay of antifibrotic therapy. Points of therapeutic intervention may include: (i) removing the injurious stimuli; (ii) suppressing hepatic inflammation; (iii) down-regulating stellate cell activation; and (iv) promoting matrix degradation. The future prospects for effective antifibrotic treatment are more promising than ever for the millions of patients with chronic liver disease worldwide.