Inflammation-related differences in mucosa-associated microbiota and intestinal barrier function in colonic Crohn's disease.

Crohn's disease (CD), characterized by discontinuous intestinal injury and inflammation, has been associated with changes in luminal microbial composition and impaired barrier function. The relationships between visual features of intestinal injury, permeability, and the mucosa-associated microbiota are unclear. Individuals undergoing routine colonoscopy (controls) and patients with CD were evaluated by clinical parameters and confocal laser scanning endomicroscopic colonoscopy (CLE). Patients with CD were categorized as either CD with no injury (CD-NI) or CD with injury (CD-I). Colonic biopsies were taken from adjacent matched sites in all individuals, and CLE images from these sites were analyzed for vascular permeability. Microbial composition was evaluated by 16S rRNA gene sequencing of the V3 region, and the mycome was identified through internal transcribed spacer 2 sequencing. Subgroup analyses were performed for histology, paracellular permeability (Ussing chamber), and encroachment of bacteria (fluorescent in situ hybridization). CD-I patients showed an altered microbial community compared with both controls and CD-NI patients, with enrichment in Escherichia and a decrease in Firmicutes, including Lachnospira, Faecalibacterium, and Blautia. In CD-I patients, bacterial encroachment to host epithelial cells was greater in sites of injury than in matched biopsy sites. Biopsies from sites of injury also demonstrated greater vascular and paracellular permeability. Overall, CD-I patients showed an altered mucosal microbial community compared with CD-NI patients and controls. Matched biopsy samples in CD-I patients revealed that sites of injury, identified endoscopically, are characterized by increased encroachment of bacteria to host epithelial cells, associated with increased paracellular and vascular permeability, which may drive inflammation in CD. NEW & NOTEWORTHY Patients with Crohn's disease (CD) with areas of colonic injury have an altered microbial community compared with patients who have no endoscopic evidence of injury or active disease. Although matched biopsies from patients with colonic injury show no differences in the mucosa-associated microbiota, injured sites are associated with increased permeability and increased encroachment. Our results support the notion that dysbiotic communities within patients with colonic injury cause or permit disruption of the mucosal and endothelial layers in CD.

New Role of Nod Proteins in Regulation of Intestinal Goblet Cell Response in the Context of Innate Host Defense in an Enteric Parasite Infection.

Mucins secreted by intestinal goblet cells are considered an important component of innate defense in a number of enteric infections, including many parasitic infections, but also likely provide protection against the gut microbiota. Nod proteins are intracellular receptors that play key roles in innate immune response and inflammation. Here, we investigated the role of Nod proteins in regulation of intestinal goblet cell response in naive mice and mice infected with the enteric parasite Trichuris muris. We observed significantly fewer periodic acid-Schiff (PAS)-stained intestinal goblet cells and less mucin (Muc2) in Nod1 and Nod2 double-knockout (Nod DKO) mice after T. muris infection than in wild-type (WT) mice. Expulsion of parasites from the intestine was significantly delayed in Nod DKO mice. Treatment of naive WT mice with Nod1 and Nod2 agonists simultaneously increased numbers of PAS-stained goblet cells and Muc2-expressing cells, whereas treatment with Nod1 or Nod2 separately had no significant effect. Stimulation of mucin-secreting LS174T cells with Nod1 and Nod2 agonists upregulated core 3 ß1,3-N-acetylglucosaminyltransferase (C3GnT; an important enzyme in mucin synthesis) and MUC2. We also observed lower numbers of PAS-stained goblet cells and less Muc2 in germfree mice. Treatment with Nod1 and Nod2 agonists enhanced the production of PAS-stained goblet cells and Muc2 in germfree mice. These data provide novel information on the role of Nod proteins in goblet cell response and Muc2 production in relation to intestinal innate defense.