Regulation Of Hepatic Stellate Cell Activation And Proliferation And Collagen Synthesis By Protease Activated Receptors And Role Of Protease Receptors In Liver Fibrosis

Cirrhosis is a scarring process that includes components of both increased fibrogenesis and wound contraction. liver fibrosis is a pathologic histology foundation of cirrhosis, concentration of extracellular matrix (ECM) is key feature of liver fibrosis, and then liver proceed remodeling and scarring . Hepatic stellate cells (HSC) are increasingly being recognized as the key players in liver fibrogenesis. In chronic liver disease and injury of liver, HSC acquire an activated phenotype, which includes increased proliferation, contractility, and the ability to release collagen along with chemotaxis and cytokine. It is commonly accepted that the activation of HSC is a core pathogenetic event in fibrogenesis and also is a final common pathway in fibrogenesis of various chronic liver diseases.Even though expression of thrombin and trypase is increased in cirrhosis patients and exposure of HSC to thrombin and trypase triggers a number of effector functions, including proliferation, contraction, and collagen synthesis. It is known that protease activated receptor-1(PAR1) is an activity acceptor of thrombin and protease activated receptor-2(PAR2 ) is an activity acceptor of trypase. The functional relevance of G-protein-coupled receptor, protease activated receptor-1(PAR1) and protease activated receptor-2(PAR2 ),in modulating HSC activity and proliferation and collagen deposition is unknown.In this study, In vitro studies were performed on primary cultures of HSC , Rat HSC were isolated from SD rats according to a modification of the technique of Friedman, and in vivo studies were performed on liver tissue of rats that had undergone bile duct ligation (BDL).Expression of mRNA for PAR1 and PAR2 were examined by reverse transcription polymerase chain reaction (RT-PCR) and receptor protein examined by Westerm blotting and immuocytochemistry, observated characteristic cell shape, and examined expression of -smooth muscle actin ( -SMA),Desmin, mRNA and protein for type I collagen and type III collagen.Results and conlusions were presented as follows:1. According to a modification of the technique of Friedman, the yield of HSC was about 3.6×107 per liver of 350-400 grams rat, viability of cells was more than 96% and purity of HSC was more than 95%. This modified procedure for isolation and culturing HSC from the rat liver was an effective method of study the role of HSC in hepatic fibrosis.2. During culture on coated plastic or glass dishes rat HSC underwent phenotypic modulation and transdifferentiated from a resting phenotype within early days into a activated phenotype with typical collagenoblas shape with 10-14days after seeding. On cultured rat HSC,vitamin A autofluorescence and lipid droplet were decrease gradually or lost following HSC activation, but a-SMA, Desmin, and I/IIIcollagen protein expressions were also increased.3. The animal model of hepatic fibrosis by undergone BDL was an ideal method of study pathogenesis and prevention and cure of hepatic fibrosis , because its process was simple and short, and hepatic fibrosis was lasting.4. Expression of mRNA and receptor protein for PAR1 and PAR2 could be detected and was increased gradually on primary cultures of HSCs after seeding and on liver tissue of rats undergone BDL.5. Expression ofα-SMA and mRNA and protein for I/III collagen could be detected and was increased gradually on primary cultures of HSCs after seeding and on liver tissue of rats undergone BDL. The expressiong ofα-SMA and I/III collagen was concordance with expression of PAR1 and PAR2. So it hinted that PAR1 and PAR2 related with the activation of HSC and collagen deposition. PAR1 and PAR2 might touch or aggravate liver fibrogenesis.6. Exposure of HSC to thrombin, trypase and active peptide of PAR1 and PAR2 could trigger HSC activation, proliferation, expression of type I/III collagen and production of Monocyte chemotactic protein-1(MCP-1). So it hinted that not only PAR1 and PAR2 might touch or promote liver fibrogenesis,but also might induce inflammatory reaction and aggravate liver tissue.7. To decrease the level of thrombin and trypase and inhibit the activity of peptide of PAR1 and PAR2 could restrain HSC activation, proliferation, expression of type I/III collagen and production of MCP-1 caused by PAR1 and PAR2, accordingly relieve or prevent liver fibrogenesis and inflammatory reaction.