title: The role for dickkopf-homolog-1 in the pathogenesis of Crohn's disease-associated fistulae.
abstract: BACKGROUND
  One of the most challenging conditions in Crohn's disease (CD) patients is the treatment of perianal fistulae. We have recently shown that epithelial-to-mesenchymal transition (EMT) plays a crucial role during CD-fistulae development. Dickkopf-homolog 1 (DKK-1) is known to play a key role during EMT. Here, we investigated a role for DKK-1 in the pathogenesis of CD-associated fistulae.
  
  
  METHODS
  Dkk-1 protein expression in CD-fistula specimens were investigated by immunohistochemistry. Colonic lamina propria fibroblasts (CLPF) were obtained from either non-IBD control patients or patients with fistulizing CD. HT-29 intestinal epithelial cells (IEC) were either grown as monolayers or spheroids. Cells were treated with either TNF-α, TGF-β or IL-13. Knock-down of DKK-1 or β-Catenin was induced in HT-29-IEC by siRNA technique. mRNA expression was determined by real-time-PCR.
  
  
  RESULTS
  Dkk-1 protein was specifically expressed in transitional cells lining the fistula tracts. TGF-β induced DKK-1 mRNA expression in HT-29-IEC, but decreased it in fistula CLPF. On a functional level, DKK-1 knock-down prevented TGF-β-induced IL-13 mRNA expression in HT-29-IEC. Further, loss of β-Catenin was accompanied by reduced levels of DKK-1 and, again, IL-13 in IEC in response to TGF-β. In turn, treatment of HT-29-IEC as well as fistula CLPF with IL-13 resulted in decreased levels of DKK-1 mRNA. Treatment with TNF-α or the bacterial wall component, muramyl-dipeptide, decreased DKK-1 mRNA levels in HT-29-IEC, but enhanced it in fistula CLPF.
  
  
  CONCLUSIONS
  We demonstrate that DKK-1 is strongly expressed in cells lining the CD-fistula tracts and regulates factors involved in EMT initiation. These data provide evidence for a role of DKK-1 in the pathogenesis of CD-associated perianal fistulae.
authors.affiliation: Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Sandra Michaela
authors.initials: SM
authors.lastname: Frei
authors.forename: Colette
authors.initials: C
authors.lastname: Hemsley
authors.forename: Theresa
authors.initials: T
authors.lastname: Pesch
authors.forename: Silvia
authors.initials: S
authors.lastname: Lang
authors.forename: Achim
authors.initials: A
authors.lastname: Weber
authors.forename: Ekkehard
authors.initials: E
authors.lastname: Jehle
authors.forename: Anne
authors.initials: A
authors.lastname: Rühl
authors.forename: Michael
authors.initials: M
authors.lastname: Fried
authors.forename: Gerhard
authors.initials: G
authors.lastname: Rogler
authors.forename: Michael
authors.initials: M
authors.lastname: Scharl
mesh_terms: D003424:Crohn Disease / Q000150:complications / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D058750:Epithelial-Mesenchymal Transition; D005347:Fibroblasts / Q000378:metabolism; D005402:Fistula / Q000150:complications / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D019073:HT29 Cells; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000235:genetics*; D009092:Mucous Membrane / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000096:biosynthesis; D014409:Tumor Necrosis Factor-alpha / Q000008:administration & dosage
chemical_list: C501126:DKK1 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha