title: Matricellular protein CCN1 promotes regression of liver fibrosis through induction of cellular senescence in hepatic myofibroblasts.
abstract: Liver fibrosis occurs as a wound-healing response to chronic hepatic injuries irrespective of the underlying etiology and may progress to life-threatening cirrhosis. Here we show that CCN1, a matricellular protein of the CCN (CYR61/CTGF/NOV) family, is accumulated in hepatocytes of human cirrhotic livers. CCN1 is not required for liver development or regeneration, since these processes are normal in mice with hepatocyte-specific Ccn1 deletion. However, Ccn1 expression is upregulated upon liver injuries and functions to inhibit liver fibrogenesis induced by either carbon tetrachloride intoxication or bile duct ligation and promote fibrosis regression. CCN1 acts by triggering cellular senescence in activated hepatic stellate cells and portal fibroblasts by engaging integrin α6β1 to induce reactive oxygen species accumulation through the RAC1-NADPH oxidase 1 enzyme complex, whereupon the senescent cells express an antifibrosis genetic program. Mice with hepatocyte-specific Ccn1 deletion suffer exacerbated fibrosis with a concomitant deficit in cellular senescence, whereas overexpression of hepatic Ccn1 reduces liver fibrosis with enhanced senescence. Furthermore, tail vein delivery of purified CCN1 protein accelerates fibrosis regression in mice with established fibrosis. These findings reveal a novel integrin-dependent mechanism of fibrosis resolution in chronic liver injury and identify the CCN1 signaling pathway as a potential target for therapeutic intervention.
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, IL, USA.
authors.forename: Ki-Hyun
authors.initials: KH
authors.lastname: Kim
authors.forename: Chih-Chiun
authors.initials: CC
authors.lastname: Chen
authors.forename: Ricardo I
authors.initials: RI
authors.lastname: Monzon
authors.forename: Lester F
authors.initials: LF
authors.lastname: Lau
mesh_terms: D000818:Animals; D001665:Binding Sites; D002251:Carbon Tetrachloride; D002478:Cells, Cultured; D016922:Cellular Senescence; D002779:Cholestasis / Q000150:complications; D055515:Cysteine-Rich Protein 61 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D005260:Female; D055166:Hepatic Stellate Cells / Q000378:metabolism / Q000502:physiology; D006801:Humans; D039121:Integrin alpha6beta1 / Q000378:metabolism; D008099:Liver / Q000473:pathology; D008103:Liver Cirrhosis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D058628:Myofibroblasts / Q000378:metabolism* / Q000502:physiology; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D000074624:NADPH Oxidase 1; D009479:Neuropeptides / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D046888:Tissue Array Analysis; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D020830:rac1 GTP-Binding Protein
chemical_list: C491850:CCN1 protein, mouse; D055515:Cysteine-Rich Protein 61; D039121:Integrin alpha6beta1; D009479:Neuropeptides; C484602:Rac1 protein, mouse; D017382:Reactive Oxygen Species; D002251:Carbon Tetrachloride; D009247:NADH, NADPH Oxidoreductases; D000074624:NADPH Oxidase 1; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein