Pathophysiological mechanisms of hepatic stellate cells activation in liver fibrosis

Liver fibrosis is a complex pathological process controlled by a variety of cells, mediators and signaling pathways. Hepatic stellate cells play a central role in the development of liver fibrosis. In chronic liver disease, hepatic stellate cells undergo dramatic phenotypic activation and acquire fibrogenic properties. This review focuses on the pathophysiological mechanisms of hepatic stellate cells activation in liver fibrosis. They enter the cell cycle under the influence of various triggers. The “Initiation” phase of hepatic stellate cells activation overlaps and continues with the “Perpetuation” phase, which is characterized by a pronounced inflammatory and fibrogenic reaction. This is followed by a resolution phase if the injury subsides. Knowledge of these pathophysiological mechanisms paved the way for drugs aimed at preventing the development and progression of liver fibrosis. In this respect, impairments in intracellular signaling, epigenetic changes and cellular stress response can be the targets of therapy where the goal is to deactivate hepatic stellate cells. Potential antifibrotic therapy may focus on inducing hepatic stellate cells to return to an inactive state through cellular aging, apoptosis, and/or clearance by immune cells, and serve as potential antifibrotic therapy. It is especially important to prevent the formation of liver cirrhosis since the only radical approach to its treatment is liver transplantation which can be performed in only a limited number of countries.     

大鼠肝星状细胞分离纯化方法的改进

目的 研究肝损伤后细胞基质的沉积及纤维化形成机制,建立一种经济、简便、可靠的分离大鼠肝星状细胞(HSC)的方法.方法 用链霉蛋白酶和胶原酶灌流大鼠肝脏,Optiprep密度梯度离心分离HSC,并进行体外培养.结果 细胞得率为5.0×107/鼠,活率和纯度分别为98%、96%.结论 该方法简便、实用、稳定、可靠,为进一步研究HSC与肝纤维化的关系,尤其是细胞水平及分子生物学水平的研究奠定了基础.     

靶向性血小板衍生生长因子siRNA对肝星状细胞增殖的影响

目的探讨小干扰RNA（siRNA）降低血小板衍生生长因子B链（PDGF-B）基因对肝星状细胞（HSCs）增殖与细胞外基质表达的影响。方法构建PDGF-B靶向siRNA重组表达质粒pSilencer3.l-Hlhygro-PDGF-B siR-NA,将重组质粒转染HSCs细胞,噻唑蓝（MTT）法测定转染后12 h、24 h、36 h、48 h、60 h的增殖抑制率;半定量逆转录聚合酶链反应（RT-PCR）与免疫印迹检测转染后36 h HSCs细胞PDGF-B表达。放免法检测HSCs细胞株上清液中透明质酸和Ⅲ型前胶原的表达。结果经酶切鉴定和测序结果证实PDGF-B靶向siRNA重组表达载体构建成功,转染重组质粒36 h后,PDGF-B siRNA-1、siRNA-2、siRNA-3干预组的HSCs增殖抑制率明显高于对照质粒转染组（34.04%、14.89%、25.53%VS 3.19%;均P〈0.01～0.05）;RT-PCR和免疫印迹显示：各siRNA表达质粒阳性HSCs细胞PDGF-B mRNA和蛋白表达明显降低,与空脂质体组及对照质粒组比较,差异具有统计学意义（均P〈0.05）,放免法显示：siRNAs干预组HSCs细胞透明质酸和Ⅲ型前胶原表达明显降低,与空脂质体组及对照质粒组比较,差异具有统计学意义（均P〈0.05）。结论靶向PDGF-B链的siRNA可降低HSCs的PDGF-B基因表达,具有抑制HSCs增殖和分泌细胞外基质的能力。     

肝纤维化中肝星状细胞和肌纤维母细胞的形态学观察

目的：观察肌纤维母细胞和肝星状细胞在人慢性乙型病毒性肝炎肝纤维化过程中的作用。方法：对69例肝穿刺活检组织标本行HE、Masson三色及Sweet网织纤维的染色，按照2000年新的病毒性肝炎病理分级分期标准，进行炎症活动度和纤维化程度评定，应用免疫组织化学方法，观察平滑肌肌动蛋白（α-SMA）、vimentin、结蛋白（desmin)在肝星状细胞、肌纤维母细胞的表达。结果：在慢性肝炎肝纤维化过程中α－SMA阳性细胞不仅仅是肝星状细胞的活化。结论：在人的慢性肝炎肝纤维化过程中，并不排除肝星状细胞所起的作用，但随着肝组织炎症损伤的修复，以肌纤维母细胞为代表的间叶细胞在纤维化过程中可能起主要作用。     

Targeted inhibition of platelet-derived growth factor receptor-beta subunit in hepatic stellate cells ameliorates hepatic fibrosis in rats

The activation of hepatic stellate cells (HSCs) is the key event of the pathogenesis of hepatic fibrosis. Platelet-derived growth factor (PDGF) is the most potent mitogen for HSCs, and PDGF receptor-beta subunit (PDGFR-beta) is required for the proliferation of HSCs induced by PDGF. In this study, a high gene-silencing-efficacy PDGFR-beta small interference RNA (siRNA) was synthesized that could suppress the PDGFR-beta expression and inhibit the activation and proliferation but could not induce the apoptosis of HSCs in vitro. To avoid the side effect of nonspecific interference of PDGFR-beta, we constructed an HSCs-specific short hairpin RNA (shRNA) expression plasmid in which PDGFR-beta shRNA was driven by a glial fibrillary acidic protein (GFAP) promoter. The double-staining immunofluorescence examination indicated that GFAP promoter could target the transgene expression into HSCs in carbon tetrachloride induced acute injured rat's liver and bile duct ligation (BDL)-induced chronic injured rat's liver. Furthermore, HSCs-specific PDGFR-beta shRNA could relieve liver injury and hepatic fibrosis in the rat's model induced by BDL. This study demonstrates that PDGFR-beta siRNA may be presented as an antifibrogenic agent. The application of HSCs-specific RNA interference induced by the GFAP promoter might supply a new powerful tool for cell-specific gene therapy of hepatic fibrogenesis.     

血吸虫病肝纤维化小鼠中肝星状细胞迁移功能改变的实验研究

目的探讨影响日本血吸虫病肝纤维化小鼠肝组织中肝星状细胞(HSCs)迁移运动功能变化的相关因素。方法 SPF级6⁸周龄Balb/c小鼠16只,随机分为模型组(8只)和对照组(8只),以血吸虫尾蚴腹部贴附法建立感染模型,正常组予以生理盐水代替。于感染后8周末处理小鼠,取部分肝组织石蜡包埋,进行病理学评估,免疫荧光染色检测HSCs(α-SMA,红光)运动蛋白Fascin(绿光)的表达;另取部分肝组织,采用Real-time PCR方法检测迁移诱导因子转化生长因子β1(TGF-β1)、血小板源性生长因子(PDGF)以及单核细胞趋化因子1(MCP-1)的表达以及HSCs运动蛋白α-SMA、Fascin的表达。结果 8周末时,模型组小鼠肝组织中已形成明显肝纤维化。模型组小鼠肝组织中TGF-β1、PDGF以及MCP-1的基因表达水平分别是对照组的30倍、14倍及14倍,差异具有统计学意义(P=0.033、P=0.039以及P=0.037);同时,模型组中HSCs运动相关蛋白α-SMA和Fascin的基因表达水平分别是对照组的9倍和5倍,差异具有统计学意义(P=0.004、P=0.018);荧光共聚焦结果提示,模型组小鼠肝组织中α-SMA(红色)和Fascin(绿色)表达部位一致,集中在虫卵周围肝纤维化区域,较对照组二者表达明显增加,且红绿光分布多重叠。结论诱导HSCs运动迁移的因子表达增加和HSCs自身的运动相关蛋白表达增加均有利于HSCs运动迁移能力增强。     

阻断Wnt/β-catenin信号通路对肝星状细胞活化的影响

目的：探讨活化的肝星状细胞（hepatic stellate cell，HSC）内是否存在功能性Wnt／β-catenin信号通路的激活，以及阻断该信号通路对HSC活化的影响。方法：免疫细胞化学染色检测β-catenin在HSC-T6细胞内的表达。通过转染T细胞因子（T-cell factor，TCF）依赖的荧光素酶报告质粒（pTOPFLASH）测定HSC-T6细胞内的Wnt／β-catenin信号。将TCF的显性负性突变体（dominant negative TCF，dnTCF）表达质粒转染HSC-T6阻断Wnt／β-catenin信号的转导．用Western blot法检测α-平滑肌肌动蛋白（α-SMA）及Ⅰ型胶原表达变化。结果：HSC-T6细胞的核内有β-catenin的表达，转染pTOPFLASH的细胞荧光素酶活性显著高于对照组（P〈0．01）。与对照组相比，转染dnTCF的HSC-T6细胞α-SMA及Ⅰ型胶原表达均显著下降（P〈0．05）。结论：活化的HSC中存在Wnt／β-catenin信号通路的激活．阻断该信号通路可抑制HSC的活化。     

Reduction of fibrogenesis by selective delivery of a Rho kinase inhibitor to hepatic stellate cells in mice

One of the pathways activated during liver fibrosis is the Rho kinase pathway, which regulates activation, migration, and contraction of hepatic stellate cells (HSC). Inhibition of this kinase by the Rho kinase inhibitor Y27632 [(+)-(R)-trans- 4-(1-aminoethyl)-N-(4-pyridyl)cyclohexanecarboxamide dihydrochloride] has been shown to reduce fibrosis in animal models. However, kinase expression is ubiquitous, so any inhibitor may affect many cell types. We hypothesize that cell-specific delivery of a kinase inhibitor will be beneficial. Therefore, we conjugated Y27632 to the carrier mannose-6-phosphate (M6P) human serum albumin (HSA), which is taken up specifically in activated HSC through the M6P/insulin-like growth factor II receptor. This conjugate decreased protein expression of phosphorylated myosin light chain 2 (pMLC2) and vinculin, downstream of Rho kinase, in activated primary HSC and decreased the migration and contraction of HSC. In an ex vivo model, free Y27632 decreased contractility of rat aortas, whereas the Y27-conjugate did not, showing that the Y27-conjugate does not affect nontarget tissue. In chronic CCl(4)-induced liver fibrosis, both free drug and conjugate reduced HSC activation; however, only the Y27-conjugate significantly reduced collagen deposition. Treatment with the Y27-conjugate, but not with free drug, reduced pMLC2 expression in livers 24 h after injection, demonstrating prolonged inhibition of the Rho kinase pathway. The Rho kinase inhibitor Y27632 can be specifically targeted to HSC using M6PHSA, decreasing its effects in nontarget tissues. The targeted drug effectively reduced fibrotic parameters in vivo via the inhibition of the Rho kinase pathway.     

GFAP启动子介导EGFP靶向肝星状细胞治疗肝纤维化的价值探索

目的探索体内特异性靶向肝星状细胞(HSC)治疗肝纤维化的技术方法。方法建立四氯化碳诱导的小鼠肝纤维化模型,构建胶质纤维酸性蛋白(GFAP)启动子调控增强绿色荧光蛋白(EGFP)表达载体,采用尾静脉高压注射方法将EGFP表达裸质粒转染到纤维化小鼠的肝脏。荧光显微镜观察EGFP在肝脏的表达及免疫荧光共定位,观测EGFP与HSC标志蛋白(DESMIN)和α-平滑肌肌动蛋白(α-SMA)的共定位。结果 EGFP与DESMIN和α-SMA共定位说明EGFP主要在HSC中表达,GFAP启动子能够调控外源基因在体内靶向HSC。结论 GFAP启动子介导体内靶向HSC,治疗肝纤维化策略具有临床应用的潜力。     

干扰素α-2a与肝纤维化大鼠肝星状细胞的凋亡

背景：干扰素α-2a改善肝纤维化的机制直到目前仍尚未阐明。目的：进一步验证干扰素α-2a对C14诱导大鼠肝纤维化模型中肝星状细胞凋亡的影响。方法：建立CC14诱导肝纤维化模型,健康SD雌性大鼠50只,采用随机对照原则将SD大鼠分成5组,即生理盐水对照组、纤维化模型组、6×10^4U／kg干扰素α-2a干预组、12×10^4U／kg干扰素α-2a干预组及6×10^4U／kg干扰素α-2a对照组。造模8周时取肝组织标本,分别进行肝纤维化指标检测;RT-PCR分析肝组织bcl-2、bax的表达;免疫组织化学染色用a平滑肌肌动蛋白对活化的肝星状细胞进行标记。结果与结论：肝组织病理形态显示CC14诱导肝纤维化成功建立,表现为纤维化模型组汇管区周围纤维化明显,有芒状纤维和纤维间隔形成,各干扰素α-2a干预组肝纤维化有不同程度缓解。纤维化模型组有大量a平滑肌肌动蛋白阳性表达,6×10^4U／kg干扰素α-2a干预组a平滑肌肌动蛋白阳性表达较纤维化模型组减少,12×10^4U／kg干扰素α-2a干预组更少,6×10^4U／kg干扰素α-2a对照组未见a平滑肌肌动蛋白阳性表达。结果提示干扰素α-2a能下调CC14诱导肝纤维化bcl-2的表达,及上调bax的表达。提示干扰素α-2a阻断CC14诱导肝纤维化机制存在通过调节bcl-2、bax的表达,诱导肝星状细胞凋亡途径,该调节作用可能与干扰素α-2a剂量相关。     

Clearance of activated stellate cells for hepatic fibrosis regression: Molecular basis and translational potential

Hepatic fibrosis, characterized by abnormal accumulation of extracellular matrix (ECM), is a common pathological process of many chronic liver diseases. A growing number of studies have shown that the activation of hepatic stellate cells (HSCs) plays an important role in the pathogenesis of hepatic fibrosis. Inhibiting the activation of HSCs and accelerating the clearance of activated HSCs may be effective strategies for resolution of hepatic fibrosis. Therefore, understanding the underlying mechanisms of clearance of activated HSCs and the therapeutic implications is an active subject of research. Studies have shown that apoptosis, immune clearance, phenotype reversion and senescence are involved in clearance of activated HSCs. In this review, we will discuss the mechanisms of clearance of activated HSCs and their potential in resolution of hepatic fibrosis.     

肝组织应变参数无创性诊断肝纤维化的可行性研究

目的介绍一种由肝组织二维灰阶超声视频分析获得的应变参数,并评价其诊断慢性乙型肝炎肝纤维化的可行性。方法 27例慢性乙型肝炎患者(慢性肝病组)及8例肝右叶囊肿患者(对照组)纳入本研究,采集每位患者平静呼吸时剑突下肝组织纵切面上的二维灰阶超声视频,分析视频获得肝组织的最大累积呼吸应变值(MARS)。以肝组织活检诊断的肝纤维化病理分期作为诊断标准,应用受试者特征曲线(ROC)评价MARS诊断慢性乙型肝炎肝损害的价值。结果对照组与慢性肝病组的MARS值分别为(29.44±10.44)%及(16.70±6.60)%。经独立样本t检验,前者明显高于后者(P=0.008)。以MARS诊断肝纤维化S≥S1及S=S4,ROC曲线下面积分别为0.889及0.741。结论基于灰阶超声视频分析的MARS可以无创性诊断肝纤维化,是一种新颖、经济及可行的方法。     

Increased ADAMTS-13 proteolytic activity in rat hepatic stellate cells upon activation in vitro and in vivo

INTRODUCTION: ADAMTS-13 is a member of A Disintegrin And Metalloprotease with ThromboSpondin type 1 repeats (ADAMTS) family, primarily synthesized in hepatic stellate cells (HSCs), one of the major cell types transdifferentiating into myofibroblasts during liver fibrosis. However, the association between ADAMTS-13 expression and HSC activation or liver fibrosis is not known. METHODS: In this study, we determined the ADAMTS-13 mRNA, protein, and activity in isolated primary HSCs upon activation on a plastic dish and in liver after administration of carbon tetrachloride (CCl(4)) in rats. RESULTS: We showed that ADAMTS-13 antigen and proteolytic activity in the activated rat HSCs were dramatically increased, whereas ADAMTS-13 mRNA in these cells was only minimally altered. Similarly, the ADAMTS-13 antigen and proteolytic activity in rat liver after CCl(4) injury were also significantly increased, whereas the ADAMTS-13 mRNAs in these liver tissues were only slightly increased compared with normal. Surprisingly, despite the dramatic up-regulation of ADAMTS-13 protein synthesis in the activated HSCs after CCl(4) administration, the plasma levels of ADAMTS-13 protease in rats did not increase concordantly. CONCLUSION: We conclude that the up-regulation of ADAMTS-13 protein expression in rat HSCs during activation in vitro and in vivo suggests the possibility of ADAMTS-13 proteolysis, an important part of function of the activated HSCs, perhaps through modulation of liver regeneration or formation of liver fibrosis after various injuries. The data also suggest the minimal contribution of the activated HSCs in regulation of plasma levels of ADAMTS-13 protease.     

Targeted delivery of AAV‐transduced mesenchymal stromal cells to hepatic tissue for ex vivo gene therapy

Adeno‐associated virus (AAV)‐mediated gene therapy holds great promise if challenges related to vector neutralization by pre‐existing antibodies are circumvented. The use of autologous or allogeneic cells to shield the vector might offer the possibility of successful gene transfer in such a situation. In the present study, we evaluated the feasibility of AAV‐transduced mesenchymal stromal cells (MSCs) as a vehicle for hepatic gene transfer in a murine liver injury model. In our initial studies to determine the most suitable vector, we observed that AAV1 (91%) and AAV6 (72%) serotypes are highly efficient in transducing MSCs. Subsequently, we generated a transient liver injury model to analyse the efficacy of MSCs homing to the liver, as well as their hepatic gene transfer efficiency; our data show that administration of acetaminophen (500 mg/kg) served as a cue for the homing of MSCs to the liver. Furthermore, sex‐mismatched transplantation of AAV1‐infected MSCs demonstrated a 3.5‐fold (day 7) and 2.2‐fold (day 28) higher hepatic gene transfer efficiency. To further corroborate this, we estimated the donor cell Y chromosome copies in the liver of recipient female mice. Our data revealed a 12.7‐fold increase in average genome copies of male MSCs in the livers of recipient mice with injury compared to control, 60 days after transplantation. However, in vivo administration of AAV‐transduced MSCs in the presence of neutralization antibodies (intravenous immunoglobulin, IVIG) was not beneficial. This is possibly due to the clearance of transplanted MSCs by circulating IVIG and underscores the need to develop suitable in vivo models to study such a mode of gene transfer. Copyright © 2015 John Wiley & Sons, Ltd.     

sEVs from tonsil-derived mesenchymal stromal cells alleviate activation of hepatic stellate cells and liver fibrosis through miR-486-5p

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Targeted delivery of antisense oligodeoxynucleotides to folate receptor-overexpressing tumor cells.

A major problem in exploring the full potential of antisense ODN is the lack of a safe and efficient delivery system. In this study a new method has been developed that is highly efficient in encapsulating ODN inside folate receptor (FR)-targeted lipid vesicles. ODN formulated in these vesicles were efficiently protected from degradation by nucleases compared to free ODN. Folate efficiently mediated intracellular delivery of ODN to KB tumor cells that overexpress FR. Delivery of EGFR antisense ODN via FR-targeted lipid vesicles resulted in a significant down-regulation of EGFR expression in KB cells and cell growth inhibition, far more efficient than that with free ODN or ODN encapsulated in ligand-free lipid vesicles. Intracellular delivery of EGFR antisense ODN also sensitized KB cells to doxorubicin (DOX) treatment. Thus targeted delivery of ODN via this novel lipid vector may have potential in treating tumors that overexpress FR.     

实时弹性成像定量诊断脂肪肝患者肝纤维化程度的研究

目的探讨实时弹性成像(RTE)技术定量诊断肝纤维化的价值。方法应用RTE定量分析技术对86例新疆地区中、重度脂肪肝患者进行肝脏超声检查(S0,n=18、S1,n=18、S2,n=20、S3,n=10、S4,n=20),通过自带分析软件得到12个弹性参数,并与肝纤维化病理分级结果对比分析。结果应变均值(MEAN)、蓝色领域%(AREA%)及弹性指数(LF)与肝纤维化程度高度相关,相关系数分别为-0.677(P0.05)、0.662(P0.05)及0.637(P0.05);分别绘制ROC曲线判断其诊断肝纤维化分期的准确性,并得出区分肝纤维化分期的截断值,MEAN、%AREA及LF在S0、S1、S2、S3期时ROC曲线下面积分别为0.896、0.839、0.823、0.875(MEAN);0.890、0.844、0.822、0.783(%AREA);0.892、0.844、0.838、0.853(LF)。MEAN、%AREA、LF在区分S0、S1、S2期时的截断值分别为102.60、88.20、86.30(MEAN);31.26、38.86、40.28(%AREA);3.10、3.20、3.87(LF)。结论 RTE在定量诊断肝纤维化中有一定的临床应用价值。