Abstract

Recently attention has been focused on the biology of transforming growth factor-beta1 (TGF-beta1). TGF-beta1, a potent regulator of cell proliferation, stimulates the proliferation of many cell types of mesenchymal origin and inhibits the growth of many epithelial cells. But its cellular distribution and temporal expression remain unknown. The aim of this study was to investigate immunohistochemically the cellular distribution and temporal expression of TGF-beta1 during rat hepatic fibrosis induced by dimethylnitrosamine (DMN). At an early stage of liver fibrosis, there was evidence of multiple centrilobular hemorrhagic necrosis with parenchymal lobular collapse, and at a late stage, there was septal fibrosis with micronodule formation of the parenchyme. TGF-beta1 peptide was first expressed in centrilobular clusters of macrophage which were surrounded by many TGF-beta1 negative fat-storing cells (FSCs). Along with the progression of fibrosis, the TGF-beta1 peptide was expressed in the alpha-smooth muscle actin positive FSCs and also in some peripherally located hepatocytes of micronodules. Serum IFN-gamma was detected in the serum 2 weeks after an initial administration of DMN had reached the peak level at the 4th week and then markedly decreased at the 5th week. We think that TGF-beta1 peptide is produced by macrophages influenced by soluble IFN-gamma, and is expressed in the -smooth muscle actin positive mesenchymal cells and regenerating hepatocytes, and that this cytokine may have an important role in the synthesis of the extracellular matrix and in the regulation of hepatocytic regeneration.

• Keywords: Liver fibrosis;Dimethylnitrosamine;Rat;TGF-beta1;IFN-gamma