Portal and Parenchymal Alterations of the Liver in Idiopathic Portal Hypertension: A Histological and Immunochemical Study
ABSTRACT Idiopathic portal hypertension (IPH) is characterized by presinusoidal portal hypertension owing to the intrahepatic, presinusoidal portal venous block, whereas the primary cause and initial vascular lesions(s) remain only speculative. In this study, a total of 97 IPH livers were histopathologically and immunohistochemically examined, placing emphasis on hepatic parenchymal fibrosis and atrophy as well as on portal tract fibrosis. Alcoholic cirrhosis and normal livers were used as controls. When compared with normal livers, the expression of connective tissue growth factor (CTGF) in periductal mononuclear cells was significant. Matrix metalloproteinase (MMP)9-positive mononuclear cells were fewer in number in the portal tract of IPH liver, when compared with alcoholic cirrhosis. These findings suggest a possible pathogenesis of collagen and elastin deposition because of increased CTGF expression and decreased MMP-9 expression in portal tracts of IPH. Sinusoidal dilatation associated with hepatocellular atrophy and apoptosis occurred frequently, but focally in 20% of the IPH cases. These changes were most often found in hyperplastic hepatocellular areas and in the perivenular areas of hepatic lobules. In these areas, pericellular fibrosis and thin fibrous septa were also frequently seen. In these fibrotic areas, there were deposited not only collagen fibers, but also elastic fibers, in which alpha-smooth muscle actin-positive sinusoidal cells, reflecting activated hepatic stellate cells, were frequently detected. It is possible that in IPH cases, continuing portal venous blood insufficiency may be responsible for hepatic parenchymal damage, which may be followed by hepatocellular apoptotic dropout and then by hepatic parenchymal atrophy and fibrosis.
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- "Collagen a1(I) mRNA and collagen a2(I) mRNA were increased, on average, several hundred fold, as well as mRNAs encoding type V and type VIII collagens. Table 3 shows the most downregulated genes, of which MMP9 was previously reported to be downregulated in activated HSCs in vivo . To verify the microarray data we assessed the expression of the selected genes by RT-PCR. "
ABSTRACT: Liver fibrosis is characterized by accumulation of extracellular matrix proteins synthesized by activated hepatic stellate cells (HSCs). To understand molecular mechanisms of HSCs activation a comprehensive comparison of gene expression between quiescent and activated HSCs is needed. Using DNA microarrays we compared expression of 31,100 genes between quiescent rat HSCs and culture activated rat HSCs. Expression of the components of Wnt signaling was analyzed in HSCs and fibrotic livers by RT-PCR. Activation of beta-catenin was analyzed by Western blot. Nine hundred genes were upregulated more than 4.6-fold and 500 genes were downregulated more than 5.7-fold in activated HSCs. The upregulated genes included Wnt receptor frizzled 2, ligands Wnt4 and Wnt5, which was confirmed in fibrotic livers. Expression of the target genes of Wnt signaling was increased from 5- to 70-fold. Phosphorylation and nuclear translocation of beta-catenin were unchanged, indicating activation of the noncanonical Wnt pathway. Highly upregulated expression of Wnt5a and its receptor frizzled 2 implicates this pathway in differentiation of quiescent HSCs into myofibroblasts. Activation of Wnt signaling pathway in HSCs and in animal models of liver fibrosis has not been described previously, suggesting an important role of Wnt signaling in development of liver fibrosis.Journal of Hepatology 10/2006; 45(3):401-9. DOI:10.1016/j.jhep.2006.03.016 · 11.34 Impact Factor
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ABSTRACT: Connective tissue growth factor (CTGF/CCN2) is a highly profibrogenic molecule which is overexpressed in many fibrotic lesions, including those of the liver. CTGF/CCN2 is transcriptionally activated by transforming growth factor-beta (TGF-beta) and appears to mediate some of the extracellular matrix (ECM)-inducing properties that have been previously attributed to TGF-beta. CTGF/CCN2 and TGF-beta stimulate connective tissue cell proliferation and ECM synthesis in vitro and exhibit shared fibrogenic and angiogenic properties in vivo. In fibrotic liver, CTGF/CCN2 mRNA and protein are produced by fibroblasts, myofibroblasts, hepatic stellate cells (HSCs), endothelial cells, and bile duct epithelial cells. CTGF/CCN2 is also produced at high levels in hepatocytes during cytochrome P-4502E1-mediated ethanol oxidation. CTGF/CCN2 expression in cultured HSCs is enhanced following their activation or stimulation by TGF-beta while exogenous CTGF/CCN2 is able to promote HSC adhesion, proliferation, locomotion, and collagen production. Collectively, these data suggest that during initiating or downstream fibrogenic events in the liver, production of CTGF/CCN2 is regulated primarily by TGF-beta in one or more cell types and that CTGF/CCN2 plays important roles in HSC activation and progression of fibrosis. This article reviews the data that support the importance of CTGF/CCN2 in hepatic fibrosis and highlights the concept that CTGF/CCN2 may represent a new therapeutic target in this disease.Hepatology Research 05/2003; 26(1). DOI:10.1016/S1386-6346(03)00115-3 · 2.74 Impact Factor
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ABSTRACT: Connective tissue growth factor (CTGF) is a cysteine-rich, extracellular matrix-associated heparin-binding protein implicated in a variety of fibrotic disorders. CTGF is initially synthesized as a mosaic protein containing four discrete structural modules (CTGF(1-4)) but this is susceptible to proteolytic cleavage yielding isoforms comprising modules 3 and 4 (CTGF(3-4)) or module 4 alone (CTGF(4)). In this study, we show that cultured rat hepatic stellate cells (HSCs) produce CTGF(1-4) and CTGF(3-4) following treatment with transforming growth factor-beta and that CTGF is a cell adhesion factor for activated HSCs. Low density lipoprotein receptor-associated protein (LRP) is a receptor for CTGF(1-4) or CTGF(3-4), but not CTGF(4), whereas cell surface heparan sulfate proteoglycans (HSPGs) are binding sites for all CTGF isoforms. Prior occupancy of LRP with other LRP ligands, receptor associated protein, anti-LRP, or a thrombospondin type I peptide (TEWSACSKTCG) resulted in a 50% decrease in the adhesion of activated HSCs to CTGF(1-4) or CTGF(3-4) whereas there was no effect on CTGF(4)-mediated adhesion. Co-incubation of CTGF with heparin or perturbation of cell surface HSPGs with heparinase or sodium chlorate completely blocked adhesion of activated HSCs to all CTGF isoforms. Freshly isolated HSCs demonstrated only weak binding to CTGF but strong binding to fibronectin. Thus HSC adhesion is at least partially promoted by CTGF through its binding to LRP, a process that is heparin-dependent. CTGF-LRP interactions are likely mediated by module 3 and CTGF-heparin interactions occur principally in module 4, although additional motifs may account for the heparin-dependency of LRP binding. These data show that LRP and HSPGs are utilized by HSCs for binding to CTGF and suggest that these cell surface molecules may be involved in mediating CTGF activity or adhesive signaling during the activation process.Hepatology Research 12/2003; 27(3):214-220. DOI:10.1016/S1386-6346(03)00241-9 · 2.74 Impact Factor