Smad expression of hepatic stellate cells in liver cirrhosis in vivo and hepatic stellate cell line in vitro

Abstract

Smad expressions, signaling mediators of transforming growth factor-beta (TGF-beta) superfamily of cytokines, were investigated in paraffin-embedded tissue sections of liver cirrhosis due to the hepatitis C virus infection and in the hepatic stellate cell (HSC) line in vitro. Smad 2/3, 4 and 7 was expressed in the nucleus of the HSC in the cirrhotic liver, while the expression was weak in the non-cirrhotic liver. TGF-beta1 expression in the HSC of the cirrhotic liver was strong, while the expression was weak in the non-cirrhotic liver. In situ hybridization also demonstrated the Smad signalings in the HSC of the cirrhotic liver, which confirmed the results of the Smad expressions by immunohistochemistry. The HSC line showed a cytoplasmic and a weak nuclear expression of Smads without TGF-beta1 stimulation, while these cells showed a strong Smad expression in the nucleus by TGF-beta1 stimulation. Immunocytochemical assay demonstrated that the TGF-beta1 stimulation induced the increase of the Smad expressions and the decrease of the autocrine TGF-beta1 in the HSC line. In situ hybridization assay also demonstrated an increase of the Smad mRNA signalings by TGF-beta1 stimulation in vitro. These observations suggest that the Smad expressions increase in the nucleus of the HSC in the cirrhotic liver and that the TGF-beta1 stimulation induces the Smad expression.