M2 macrophages activate WNT signaling pathway in epithelial cells: relevance in ulcerative colitis

PLoS One. 2013 Oct 22;8(10):e78128. doi: 10.1371/journal.pone.0078128. eCollection 2013.


Macrophages, which exhibit great plasticity, are important components of the inflamed tissue and constitute an essential element of regenerative responses. Epithelial Wnt signalling is involved in mechanisms of proliferation and differentiation and expression of Wnt ligands by macrophages has been reported. We aim to determine whether the macrophage phenotype determines the expression of Wnt ligands, the influence of the macrophage phenotype in epithelial activation of Wnt signalling and the relevance of this pathway in ulcerative colitis. Human monocyte-derived macrophages and U937-derived macrophages were polarized towards M1 or M2 phenotypes and the expression of Wnt1 and Wnt3a was analyzed by qPCR. The effects of macrophages and the role of Wnt1 were analyzed on the expression of β-catenin, Tcf-4, c-Myc and markers of cell differentiation in a co-culture system with Caco-2 cells. Immunohistochemical staining of CD68, CD206, CD86, Wnt1, β-catenin and c-Myc were evaluated in the damaged and non-damaged mucosa of patients with UC. We also determined the mRNA expression of Lgr5 and c-Myc by qPCR and protein levels of β-catenin by western blot. Results show that M2, and no M1, activated the Wnt signaling pathway in co-culture epithelial cells through Wnt1 which impaired enterocyte differentiation. A significant increase in the number of CD206+ macrophages was observed in the damaged mucosa of chronic vs newly diagnosed patients. CD206 immunostaining co-localized with Wnt1 in the mucosa and these cells were associated with activation of canonical Wnt signalling pathway in epithelial cells and diminution of alkaline phosphatase activity. Our results show that M2 macrophages, and not M1, activate Wnt signalling pathways and decrease enterocyte differentiation in co-cultured epithelial cells. In the mucosa of UC patients, M2 macrophages increase with chronicity and are associated with activation of epithelial Wnt signalling and diminution in enterocyte differentiation.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, CD / immunology
  • Antigens, CD / metabolism
  • Caco-2 Cells
  • Cell Differentiation / immunology
  • Colitis, Ulcerative / immunology
  • Colitis, Ulcerative / metabolism*
  • Colitis, Ulcerative / pathology
  • Enterocytes / immunology
  • Enterocytes / metabolism*
  • Enterocytes / pathology
  • Female
  • Humans
  • Macrophages / immunology
  • Macrophages / metabolism*
  • Macrophages / pathology
  • Male
  • Proto-Oncogene Proteins c-myc / immunology
  • Proto-Oncogene Proteins c-myc / metabolism
  • U937 Cells
  • Wnt Signaling Pathway*
  • Wnt1 Protein / immunology
  • Wnt1 Protein / metabolism
  • Wnt3A Protein / immunology
  • Wnt3A Protein / metabolism
  • beta Catenin / immunology
  • beta Catenin / metabolism


  • Antigens, CD
  • MYC protein, human
  • Proto-Oncogene Proteins c-myc
  • WNT1 protein, human
  • WNT3A protein, human
  • Wnt1 Protein
  • Wnt3A Protein
  • beta Catenin

Grants and funding

This work was supported by Ministerio de Ciencia e Innovación [grants number SAF2010-20231 and SAF2010-16030], Ministerio de Sanidad y Consumo [grant number PI11/00327], CIBERehd [grant number CB06/04/0071] and Generalitat Valenciana [grant number PROMETEO/2010/060].