title: Downregulation of the Wnt antagonist Dkk2 links the loss of Sept4 and myofibroblastic transformation of hepatic stellate cells.
abstract: OBJECTIVE
  Sept4, a subunit of the septin cytoskeleton specifically expressed in quiescent hepatic stellate cells (HSCs), is downregulated through transdifferentiation to fibrogenic and contractile myofibroblastic cells. Since Sept4(-/-)mice are prone to liver fibrosis, we aimed to identify the unknown molecular network underlying liver fibrosis by probing the association between loss of Sept4 and accelerated transdifferentiation of HSCs.
  
  
  METHODS
  We compared the transcriptomes of Sept4(+/+) and Sept4(-/-) HSCs undergoing transdifferentiation by DNA microarray and quantitative reverse transcription polymerase chain reaction (RT-PCR) analysis. Because Dickkopf2 (Dkk2) gene expression is reduced in Sept4(-/-) HSCs, we tested whether supplementing Dkk2 could suppress myofibroblastic transformation of Sept4(-/-) HSCs. We tested the involvement of the canonical Wnt pathway in this process by using a lymphoid enhancer-binding factor/transcription factor-luciferase reporter assay.
  
  
  RESULTS
  We observed consistent upregulation of Dkk2 in primary cultured HSCs and in a carbon tetrachloride liver fibrosis in mice, which was decreased in the absence of Sept4. Supplementation with Dkk2 suppressed the induction of pro-fibrotic genes (α-smooth muscle actin and 2 collagen genes) and induced an anti-fibrotic gene (Smad7) in Sept4(-/-) HSCs. In human liver specimens with inflammation and fibrosis, Dkk2 immunoreactivity appeared to be positively correlated with the degree of fibrotic changes.
  
  
  CONCLUSIONS
  Pro-fibrotic transformation of HSCs through the loss of Sept4 is, in part, due to reduced expression of Dkk2 and its homologues, and the resulting disinhibition of the canonical Wnt pathway.
authors.affiliation: Department of Surgery, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606 8507, Japan. atsukoya@kuhp.kyoto-u.ac.jp
authors.forename: Atsuko
authors.initials: A
authors.lastname: Yanagida
authors.forename: Keiko
authors.initials: K
authors.lastname: Iwaisako
authors.forename: Etsuro
authors.initials: E
authors.lastname: Hatano
authors.forename: Kojiro
authors.initials: K
authors.lastname: Taura
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Sato
authors.forename: Masato
authors.initials: M
authors.lastname: Narita
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Nagata
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Asechi
authors.forename: Shinji
authors.initials: S
authors.lastname: Uemoto
authors.forename: Makoto
authors.initials: M
authors.lastname: Kinoshita
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D002251:Carbon Tetrachloride / Q000633:toxicity; D002478:Cells, Cultured; D020869:Gene Expression Profiling; D055166:Hepatic Stellate Cells / Q000378:metabolism / Q000473:pathology*; D006505:Hepatitis / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D007249:Inflammation / Q000378:metabolism / Q000473:pathology*; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008103:Liver Cirrhosis / Q000378:metabolism / Q000473:pathology*; D008156:Luciferases / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D058628:Myofibroblasts / Q000378:metabolism / Q000473:pathology*; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D058112:Septins / Q000502:physiology*; D015398:Signal Transduction; D051153:Wnt Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D015415:Biomarkers; C405060:Dkk2 protein, mouse; D036341:Intercellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D051153:Wnt Proteins; D002251:Carbon Tetrachloride; D008156:Luciferases; C115474:Sept4 protein, mouse; D058112:Septins