Altered factor VII activating protease expression in murine hepatic fibrosis and its influence on hepatic stellate cells

Abstract

Background: Platelet-derived growth factor-BB (PDGF-BB) is a profibrotic factor in liver fibrosis through its ability to stimulate hepatic stellate cells (HSC). The liver-derived serine protease factor VII activating protease (FSAP) regulates the activities of PDGF-BB in a cell-specific manner. Aims: Our aim was to determine the influence of FSAP on the activation of HSC and to analyse the regulation of FSAP in hepatic fibrogenesis. Methods: The effect of FSAP on PDGF-stimulated p42/p44 mitogen-activated protein kinase (MAPK) activation in primary rat HSC was determined by Western blotting. Migration and proliferation of HSC was evaluated in Boyden chamber experiments and 3H-thymidine incorporation assays respectively. Expression of FSAP was analysed in a CCl4 mouse model of liver fibrosis by Western blot, quantitative real-time polymerase chain reaction and immunohistochemistry. Results: FSAP inhibited PDGF-BB-stimulated p42/p44 MAPK phosphorylation, proliferation and migration of HSC. FSAP mRNA expression level was increased 3 h after CCl4 application and decreased after 18h and, in established fibrosis, after chronic CCl4 administration. In parallel, there was a decrease in the circulating FSAP protein in chronic fibrosis. Concurrently, the homogenous hepatic expression pattern of FSAP was disturbed. Immunohistochemistry revealed a decrease of FSAP in hepatocytes in inflammatory and fibrotic lesions. Conclusions: Our results demonstrate an inhibitory effect of FSAP on PDGF-mediated activation of HSC. In addition, FSAP expression is transiently increased in acute-phase reaction but decreased during chronic fibrogenesis, which in turn may influence PDGF-BB availability and myofibroblast activity. © 2009 John Wiley & Sons A/S.