肝星状细胞的活化与肝纤维化

肝纤维化是机体对损伤的一种修复作用，即使可以应用基因或其他疗法彻底消除纤维化，但机体对抑制或消除纤维化后将产生何种反应及后果尚难预测。肝星状细胞（hepatic stellate cells，HSC）是引起肝纤维化的主要细胞，对HSC与其活化型一肌成纤维细胞（myofibroblast，MF）在肝损伤中作用的研究已颇为深入，而HSC激活在肝纤维化发生、发展中的作用甚为重要。     

肝星状细胞活化的功能改变

肝星状细胞活化是一个形态、功能等改变的复杂过程。肝星状细胞活化的功能改变与肝纤维化形成关系密切。本综述了近年来肝星状细胞活化功能改变的有关研究。     

肝星状细胞活化的细胞学基础

肝纤维化是指各种致病因素所致的肝脏内纤维结缔组织增生,其特点是大量细胞外基质在窦周间隙沉积。而肝星状细胞是肝纤维化细胞外基质的主要细胞［１］,在肝纤维化的形成中起关键作用［２］,肝星状细胞活化已成为肝纤维化基础研究的热点。本文综述了肝星状细胞活化有关的细胞学研究。1 肝星状细胞活化的概念　目前,肝星状细胞活化尚无一个确切的定义。但一些资料描述了它的特征：肝星状细胞活化以粗面内质网增加、维生素A脂滴减少、细胞周胶原增多为特征［３］;肝损伤过程中肝星状细胞进行一个以细胞增殖和纤维生成增加为特征的活化过…     

肝星状细胞活化的分子生物学机制研究进展

肝纤维化的实质是细胞外基质的过度沉积。活化的肝星状细胞是肝内细胞外基质的主要来源。在各种致肝纤维化因素的作用下,肝星状细胞从富含维生素A的静息细胞表型转变为具有增殖性、分泌性的肌成纤维细胞表型。肝星状细胞活化以及活化后如何维持其致纤维化的特征,需要进一步去研究和探讨,以期找到更多的治疗肝纤维化的方法和策略。这里主要将肝星状细胞的活化及其分子生物学机制作一综述。     

活化肝星状细胞的信号传导

肝纤维化是肝脏对各种急慢性肝损伤的疤痕修复反应的结果,是各种慢性肝病向肝硬化进展的共同环节,其最主要的特征是以胶原为主的细胞外基质(ECM)的生成与降解失衡,在肝脏中的过度沉积.活化的肝星状细胞(HSC)是肝纤维化发生时ECM的主要来源.HSC持续激活后增殖、迁移和表型转化,成为肌成纤维样细胞,是肝纤维化发生和发展的核心环节.活化HSC具有如下特点:(1)合成和分泌间质胶原等各种ECM;(2)自分泌产生致纤维化细胞因子如转化生长因子(TGF)β I;(3)释放胶原酶抑制物组织金属蛋白酶抑制剂(TIMP);(4)分泌趋化因子及其他炎症性细胞因子;(5)具有细胞收缩特性;(6)合成基质金属蛋白酶(MMP),使ECM降解异常;(7)对凋亡刺激的耐受性等.     

影响肝星状细胞活化的因素

肝纤维化是指各种致病因素所致的肝脏内纤维结缔组织增生，其特点是大量细胞外基质(extracellular matrix，ECM)在窦周间隙沉积。而肝星状细胞(hepatic stellate cells，HSC)是肝纤维化细胞外基质的丰要来源细胞，在肝纤维化的形成中起关键作用，HSC活化已成为肝纤维化基础研究的热点。     

肝星状细胞活化与细胞周期调控

肝星状细胞活化是肝纤维化形成的中心环节,目前尚未能完全阐明其复杂机制,近年研究发现该过程与细胞周期调控紊乱有密切关系。现对近年来 HSC活化和肝纤维化时 HSC细胞周期调控研究作一综述。     

肝星状细胞活化的启动、维持和调控

肝纤维化的形成是一个多因素、多细胞参与的复杂过程，肝星状细胞（HSC）的活化是其中的中心环节。PDGF、TGFβ、RA、PPAR及ROS等均参与了HSC活化过程的调节。     

阻断Wnt/β-catenin信号通路对活化肝星状细胞凋亡的影响

HSC的活化是肝纤维化的中心环节,参与HSC活化的多种因素如生长因子、细胞因子、氧化应激产物等,需通过HSC细胞内的信号转导才能发挥作用。Wnt／β-catenin信号通路是调控细胞生长、增殖和凋亡的关键通路,在胚胎发育和肿瘤发生中起着重要作用。近年来发现该信号通路与肺及肾纤维化的形成密切相关。     

Requirement of CCL17 for CCR7- and CXCR4-dependent migration of cutaneous dendritic cells

Chemokines are known to regulate the steady-state and inflammatory migration of cutaneous dendritic cells (DCs). The β-chemokine CCL17, a ligand of CCR4, is inducibly expressed in a subset of DCs and is strongly up-regulated in atopic diseases. Using an atopic dermatitis model, we show that CCL17-deficient mice develop acanthosis as WT mice, whereas dermal inflammation, T helper 2-type cytokine production, and the allergen-specific humoral immune response are significantly decreased. Notably, CCL17-deficient mice retained Langerhans cells (LCs) in the lesional skin after chronic allergen exposure, whereas most LCs emigrated from the epidermis of allergen-treated WT controls into draining lymph nodes (LNs). Moreover, CCL17-deficient LCs showed impaired emigration from the skin after exposure to a contact sensitizer. In contrast, the absence of CCR4 had no effect on cutaneous DC migration and development of atopic dermatitis symptoms. As an explanation for the major migratory defect of CCL17-deficient DCs in vivo, we demonstrate impaired mobility of CCL17-deficient DCs to CCL19/21 in 3D in vitro migration assays and a blockade of intracellular calcium release in response to CCR7 ligands. In addition, responsiveness of CCL17-deficient DCs to CXCL12 was impaired as well. We demonstrate that the inducible chemokine CCL17 sensitizes DCs for CCR7- and CXCR4-dependent migration to LN-associated homeostatic chemokines under inflammatory conditions and thus plays an important role in cutaneous DC migration.     

Inhibition of hepatic stellate cells proliferation by mesenchymal stem cells and the possible mechanisms

Aim: During fibrosis, hepatic stellate cells (HSCs) undergo a complex activation process characterized by increased proliferation and extracellular matrix deposition. Previous studies have suggested that mesenchymal stem cells (MSCs) may ameliorate fibrogenesis and represent a promising strategy for cell therapy. However, the underlying mechanisms are not fully understood. Methods: Hepatic stellate cells were treated with or without MSCs. Then cell proliferation and cell cycle were analyzed. Production of soluble factors by MSCs and its relation with cell proliferation suppression was evaluated by transwell co‐culture and RNA interference. Effects of MSCs on the gene expression of collagen were also evaluated. Results: MSCs induced G₀/G₁ arrest of HSCs growth partly through secreting soluble factors TGF‐β3 and HGF, which resulted in up‐regulation of p21^Cip1 and p27^Kip1 expression and down‐regulation of cyclinD1. MSCs inhibited the phosphorylation of extracellular signal‐regulated kinase (ERK) 1/2 and reduced gene expression of collagen type I and III. MSCs did not reverse the proliferation and collagen type I gene expression of HSCs provoked by PDGF. Conclusions: The growth inhibition of HSCs induced by MSCs through an arrest in the G₀/G₁ phase of the cell cycle is partially mediated by secretion of TGF‐β3 and HGF. MSCs inhibit HSCs activation through decreasing phosphorylation of extracellular signal‐regulated kinase (ERK) 1/2. These results further support MSCs may be used as a novel therapy for treating fibrotic diseases in human.     

Histological evaluation of intracapsular venous invasion for discrimination between portal and hepatic venous invasion in hepatocellular carcinoma

Background and Aim:  Histological criteria for intracapsular venous invasion (IVI) that would allow its discrimination between portal and hepatic venous invasion in hepatocellular carcinoma (HCC) have not been established.
Methods:  We evaluated IVI immunohistochemically to discriminate between portal and hepatic venous invasion in 89 resected specimens from patients with HCC. IVI was defined as the microscopic involvement of the vessels within the fibrous capsule of HCC. The hepatic venous system was subdivided into the central vein and the sublobular/hepatic vein. Immunohistochemical analysis with the D2-40 monoclonal antibody revealed lymphatic vessels.
Results:  In non-neoplastic liver tissues, the portal veins ( n  = 4355) were accompanied by lymphatic vessels (99.7%), bile ductules (100%) and arteries (96%), whereas the central veins ( n  = 3932) and sublobular/hepatic veins ( n  = 662) were rarely accompanied by lymphatic vessels (0% and 17%, respectively) and bile ductules (12% and 33%, respectively). In total, 29 IVI foci were detected; three foci were clearly visible within vessels that contained a distinct layer of connective tissue fibers, signifying sublobular/hepatic venous invasion. As the remaining 26 foci were accompanied by lymphatic vessels (26/26 [100%]), bile ductules (21/26 [81%]) and arteries (10/26 [38%]), these foci were considered to reflect intracapsular portal venous invasion rather than venous invasion of the central vein. Intracapsular portal venous invasion was significantly associated with extratumoral portal venous invasion ( P  < 0.001).
Conclusions:  D2-40 immunoreactivity for the histological evaluation of IVI in HCC allows discrimination between portal and hepatic venous invasion for cases in which portal venous invasion predominates.     

Predictors of hepatic venous trunk invasion and prognostic factors in patients with hepatocellular carcinomas that had come into contact with the trunk of major hepatic veins

Purpose

In this study, we tried to identify the preoperative predictors of hepatic venous trunk invasion and the prognostic factors in patients with hepatocellular carcinoma (HCC) that had come into contact with the trunk of a major hepatic vein over a distance of 1.0?cm or more.

Methods

Forty patients who had such HCCs resected were entered into this study and predictors of hepatic venous trunk invasion and prognostic factors were evaluated by univariate and multivariate analyses.

Results and Conclusions

A combined resection of the HCC and the venous trunk was performed in 29 patients. Hepatic venous trunk invasion was observed in 12 patients, including 2 with inferior vena cava tumor thrombus. A stepwise logistic regression analysis indicated that tumors larger than or equal to 7?cm in diameter and tumors showing a poorly differentiated histological grade were independent predictors of hepatic venous trunk invasion. The survival of patients without venous trunk invasion was significantly better than that for patients with venous trunk invasion (P = 0.048). A univariate analysis revealed that Child–Pugh classification B (P = 0.002), a high des-γ-carboxy prothrombin concentration (≧400?mAU/ml, P = 0.023), a large HCC (≧5.0?cm in diameter, P = 0.002), the presence of portal vein invasion (P < 0.001), the presence of venous trunk invasion (P = 0.048), the presence of intrahepatic metastasis (P < 0.001), and poorly differentiated HCC (P = 0.006) correlated with a worse overall survival after hepatic resection. In a multivariate analysis, however, only the presence of intrahepatic metastasis (P = 0.037, relative risk 8.25) was an independent predictor of poor overall survival.

Conclusions

Large tumors (≥7?cm in diameter) and poorly differentiated HCCs were more likely to be associated with hepatic venous trunk invasion and intrahepatic metastasis was an independent prognostic factor in patients with HCC that had come into contact with the trunk of a major hepatic vein.

     

Activated hepatic stellate cells participate in liver fibrosis in a patient with transfusional iron overload

We describe liver fibrosis caused by iron overload after a long history of blood transfusion in a patient with chronic renal failure. Pertinent laboratory data were: serum (s)-Fe 148 μg/dl; unsaturated iron binding capacity (UIBC) 14 μg/dl; s-ferritin 9350 ng/ml; human leukocyte antigen (HLA) A2, A24, B39, B55, Cw1, Cw7. Computed tomography revealed a high density in the liver, and laparoscopy revealed a brown liver. Liver histology showed bridging fibrosis from portal tracts. A heavy iron deposit was seen in Kupffer cells as well as in hepatocytes surrounded by fibrosis around the portal tracts. Immunocytochemistry revealed α-smooth muscle actin in many stellate cells distributed along the fibrotic area, and electron microscopy revealed infiltrating myofibroblastic stellate cells coexisting with collagen fibers around degenerated hepatocytes containing iron deposits. The findings are consistent with the notion that stellate cells play an important role in liver fibrogenesis in both genetic and transfusional iron overload hemochromatosis. Received Aug. 15, 1997; accepted Feb. 27, 1998     

肝星状细胞在肝细胞癌形成和发展中的作用

肿瘤的发生、侵袭及转移是长久以来备受关注的问题,肿瘤细胞与其周围基质物质的关系作为其中的关键因素愈加收到重视,肝星状细胞(HSC)作为肝癌微环境中的重要组成部分,在"炎症-肝纤维化/肝硬化-肿瘤"这一发生发展过程中充当了重要的介质。介绍了HSC的来源及其活化过程,并进一步阐述HSC自身与其分泌的多种细胞因子在肝细胞癌增殖、迁移、侵袭过程中对机体免疫反应发挥的作用。认为HSC不仅是肿瘤生长的"温床",也为肿瘤抵御了免疫系统的追踪和清除。因此在单一抗肿瘤治疗无法取得明显效果时,对于肝癌微环境的多方位治疗成为值得探讨的方案。     

Hepatic stellate cells and extracellular matrix in hepatocellular carcinoma: more complicated than ever

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide and the third leading cause of cancer death. Recent epidemiological data indicate that the mortality rate of HCC will double over the next decades in the USA and Europe. Liver cancer progresses in a large percentage of cases during the clinical course of chronic fibro‐inflammatory liver diseases leading to cirrhosis. Therefore, HCC development is regarded as the result of different environmental risk factors each involving different genetic, epigenetic‐ and chromosomal alterations and gene mutations. During tumour progression, the malignant hepatocytes and the activated hepatic stellate cells are accompanied by cancer‐associated fibroblasts, myofibroblasts and immune cells generally called tumour stromal cells. This new and dynamic milieu further enhances the responsiveness of tumour cells towards soluble mediators secreted by tumour stromal cells, thus directly affecting the malignant hepatocytes. This results in altered molecular pathways with cell proliferation as the most important mechanism of liver cancer progression. Given this contextual complexity, it is of utmost importance to characterize the molecular pathogenesis of HCC, and to identify the dominant pathways/drivers and aberrant signalling pathways. This will allow an effective therapy for HCC that should combine strategies affecting both cancer and the tumour stromal cells. This review provides an overview of the recent challenges and issues regarding hepatic stellate cells, extracellular matrix dynamics, liver fibrosis/cirrhosis and therapy, tumour microenvironment and HCC.