P088 Loss of intestinal Desmoglein 2 promotes chemically and pathogenic induced colitis
A. Gross*1, L. Pack1, S. Kant2, C. Krusche2, G. Sellge1, C. Trautwein1, R. Leube2, P. Strnad1
1University Hospital Aachen, Medicine III, Aachen, Germany, 2University Hospital Aachen, Institute of Molecular and Cellular Anatomy, Aachen, Germany
To protect the organism against luminal pathogens while enabling selective uptake of nutrients, intestinal epithelia contain the apical junctional complex (AJC) consisting of tight junctions, adherens junctions, and desmosomes. Desmosomes constitute the least investigated AJC component and are composed of transmembrane cadherins of the desmoglein (Dsg) and desmocollin (Dsc) type that are associated through the intracellular plaque proteins plakoglobin, plakophilin, and desmoplakin to the cytoplasmic keratin intermediate filament cytoskeleton. Dsg2 and Dsc2 are the major desmosomal cadherins of intestinal epithelia. They have been implicated in the regulation of epithelial cell proliferation and tumourigenesis.
Given that constitutive Dsg2 knockouts are embryonal lethal, we generated intestine-specific, conditional Villin-Cre DSG2 knockouts (DSG2Δint/Δint) and evaluated their phenotype with histological/immunological staining, immunoblotting, and electron microscopy. Gavage with FITC-dextran and BrdU administration was used to assess intestinal permeability and cell proliferation, respectively. Organoids were isolated from small intestine and cultured for 6 days. Colitis was induced by treatment with 1.6% dextran sodium sulfate (DSS) or gavage-mediated infection with 1 x 109 Citrobacter rodentium. Intestinal inflammation was evaluated via RT-polymerase chain reaction (PCR) and via myeloperoxidase quantification.
DSG2Δint/Δint mice displayed a robust knockdown of intestinal Dsg2 and a profound alteration of the remaining desmosomal components with up regulation of Dsc2 and a decrease in plakoglobin and desmoplakin while overall histology was inconspicuous. Under basal condition, DSG2Δint/Δint mice were phenotypically normal but had somewhat increased intestinal permeability, greater desmosome gap width, and a faster cell migration towards the apical tip. No obvious differences in development of intestinal organoids were seen. Short-term DSS treatment led to a marked increase in epithelial permeability, an epithelial cell loss. After long-term DSS, they suffered from significantly higher weight loss (p = 0.0001), colon shortening (p = 0.0002), stronger epithelial inflammation, and higher bacterial translocation into mesenteric lymph nodes. Further, 14 days after infection with Citrobacter rodentium, DSG2Δint/Δint mice displayed significantly stronger crypt hyperplasia and elevated levels of proinflammatory/bacterial response genes Interleukin-22/RegIIIβ.
Our results identify Dsg2 as an essential component of intestinal desmosomes, whose loss results in increased intestinal permeability and a susceptibility to different forms of epithelial injury.