The role for dickkopf-homolog-1 in the pathogenesis of Crohn's disease-associated fistulae

PLoS One. 2013 Nov 8;8(11):e78882. doi: 10.1371/journal.pone.0078882. eCollection 2013.

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.

Discussion: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Crohn Disease / complications
  • Crohn Disease / genetics
  • Crohn Disease / metabolism*
  • Epithelial Cells / metabolism
  • Epithelial Cells / pathology
  • Epithelial-Mesenchymal Transition
  • Fibroblasts / metabolism
  • Fistula / complications
  • Fistula / genetics
  • Fistula / metabolism*
  • Gene Knockdown Techniques
  • HT29 Cells
  • Humans
  • Intercellular Signaling Peptides and Proteins / biosynthesis
  • Intercellular Signaling Peptides and Proteins / genetics*
  • Mucous Membrane / metabolism
  • Mucous Membrane / pathology
  • RNA, Messenger / biosynthesis
  • Tumor Necrosis Factor-alpha / administration & dosage

Substances

  • DKK1 protein, human
  • Intercellular Signaling Peptides and Proteins
  • RNA, Messenger
  • Tumor Necrosis Factor-alpha

Grant support

This research was supported by a grant from Fonds zur Förderung des akademischen Nachwuchses (FAN) of the Zürcher Universitätsverein (ZUNIV) to MS, a research grant from the Swiss Philanthropy Foundation to MS and GR, a research credit from the University of Zurich to MS, research grants from the Swiss National Science Foundation (SNF) to MS (grant number 314730–146204), GR (grant number 310030–120312) and the Swiss IBD Cohort (grant number 3347CO-108792) and by research grants from the Zurich Center for Integrative Human Physiology (ZIHP) of the University of Zurich to MS and GR. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.