Quantification of Mucosal Activity from Colonoscopy Reports via the Simplified Endoscopic Mucosal Assessment for Crohn's Disease.

BACKGROUND: Endoscopic mucosal healing is the gold standard for evaluating Crohn's disease (CD) treatment efficacy. Standard endoscopic indices are not routinely used in clinical practice, limiting the quality of retrospective research. A method for retrospectively quantifying mucosal activity from documentation is needed. We evaluated the simplified endoscopic mucosal assessment for CD (SEMA-CD) to determine if it can accurately quantify mucosal severity recorded in colonoscopy reports. METHODS: Pediatric patients with CD underwent colonoscopy that was video recorded and evaluated via Simple Endoscopic Score for CD (SES-CD) and SEMA-CD by central readers. Corresponding colonoscopy reports were de-identified. Central readers blinded to clinical history and video scoring were randomly assigned colonoscopy reports with and without images. The SEMA-CD was scored for each report. Correlation with video SES-CD and SEMA-CD were assessed with Spearman rho, inter-rater, and intrarater reliability with kappa statistics. RESULTS: Fifty-seven colonoscopy reports were read a total of 347 times. The simplified endoscopic mucosal assessment for CD without images correlated with both SES-CD and SEMA-CD from videos (rho = 0.82, P < .0001 for each). The addition of images provided similar correlation. Inter-rater and intrarater reliability were 0.93 and 0.92, respectively. CONCLUSIONS: The SEMA-CD applied to retrospective evaluation of colonoscopy reports accurately and reproducibly correlates with SES-CD and SEMA-CD of colonoscopy videos. The SEMA-CD for evaluating colonoscopy reports will enable quantifying mucosal healing in retrospective research. Having objective outcome data will enable higher-quality research to be conducted across multicenter collaboratives and in clinical registries. External validation is needed.

Dietary L-serine confers a competitive fitness advantage to Enterobacteriaceae in the inflamed gut.

Metabolic reprogramming is associated with the adaptation of host cells to the disease environment, such as inflammation and cancer. However, little is known about microbial metabolic reprogramming or the role it plays in regulating the fitness of commensal and pathogenic bacteria in the gut. Here, we report that intestinal inflammation reprograms the metabolic pathways of Enterobacteriaceae, such as Escherichia coli LF82, in the gut to adapt to the inflammatory environment. We found that E. coli LF82 shifts its metabolism to catabolize L-serine in the inflamed gut in order to maximize its growth potential. However, L-serine catabolism has a minimal effect on its fitness in the healthy gut. In fact, the absence of genes involved in L-serine utilization reduces the competitive fitness of E. coli LF82 and Citrobacter rodentium only during inflammation. The concentration of luminal L-serine is largely dependent on dietary intake. Accordingly, withholding amino acids from the diet markedly reduces their availability in the gut lumen. Hence, inflammation-induced blooms of E. coli LF82 are significantly blunted when amino acids-particularly L-serine-are removed from the diet. Thus, the ability to catabolize L-serine increases bacterial fitness and provides Enterobacteriaceae with a growth advantage against competitors in the inflamed gut.

IL-10 produced by macrophages regulates epithelial integrity in the small intestine.

Macrophages (Mϕs) are known to be major producers of the anti-inflammatory cytokine interleukin-10 (IL-10) in the intestine, thus playing an important role in maintaining gastrointestinal homeostasis. Mϕs that reside in the small intestine (SI) have been previously shown to be regulated by dietary antigens, while colonic Mϕs are regulated by the microbiota. However, the role which resident Mϕs play in SI homeostasis has not yet been fully elucidated. Here, we show that SI Mϕs regulate the integrity of the epithelial barrier via secretion of IL-10. We used an animal model of non-steroidal anti-inflammatory drug (NSAID)-induced SI epithelial injury to show that IL-10 is mainly produced by MHCII+ CD64+ Ly6Clow Mϕs early in injury and that it is involved in the restoration of the epithelial barrier. We found that a lack of IL-10, particularly its secretion by Mϕs, compromised the recovery of SI epithelial barrier. IL-10 production by MHCII+ CD64+ Ly6Clow Mϕs in the SI is not regulated by the gut microbiota, hence depletion of the microbiota did not influence epithelial regeneration in the SI. Collectively, these results highlight the critical role IL-10-producing Mϕs play in recovery from intestinal epithelial injury induced by NSAID.

Flagellin-mediated activation of IL-33-ST2 signaling by a pathobiont promotes intestinal fibrosis.

Intestinal fibrosis is a severe complication in patients with Crohn's disease (CD). Unfortunately, the trigger leading to the development of intestinal fibrosis in the context of CD remains elusive. Here, we show that colonization by a CD-associated pathobiont adherent-invasive Escherichia coli (AIEC) promotes the development of intestinal fibrosis. Exogenously inoculated AIEC strain LF82 and commensal E. coli HS were gradually eradicated from the intestine in healthy mice. In Salmonella- or dextran sodium sulfate-induced colitis models, AIEC exploited inflammation and stably colonize the gut. Consequently, persistent colonization by AIEC LF82 led to substantial fibrosis. In contrast, commensal E. coli HS was unable to derive a growth advantage from inflammation, thereby failing to colonize the inflamed intestine or promote intestinal fibrosis. AIEC colonization potentiated the expression of the IL-33 receptor ST2 in the intestinal epithelium, which is crucial for the development of intestinal fibrosis. The induction of ST2 by AIEC LF82 was mediated by flagellin, as the ΔfliC mutant failed to induce ST2. These observations provide novel insights into pathobiont-driven intestinal fibrosis and can lead to the development of novel therapeutic approaches for the treatment of intestinal fibrosis in the context of CD that target AIEC and/or its downstream IL-33-ST2 signaling.

Regional control of regulatory immune cells in the intestine.

PURPOSE OF REVIEW: The intestine contains the largest compartment of immune regulatory cells which include T regulatory cells and IL-10 producing macrophages. These cell populations serve to restrain unnecessary immune responses of the intestine, which may lead to the pathogenesis of Crohn's disease or food allergy. RECENT FINDINGS: This review discusses the recent findings pertaining to the functional regulation of these cells which may provide insight into novel therapies. Both T regulatory cells and macrophages are regulated in microbiota-dependent and microbiota-independent manners, i.e., dietary antigens. Often, this is specific to regional specialization and environment in small intestine vs. colon. SUMMARY: These immune regulatory cells are largely regulated by microbiota in the colon, whereas in the small intestine, the microbiota has less affect, as seen in germ-free mice studies. Targeting these cells in their specific compartments may direct future treatment modalities for inflammatory bowel disease as ulcerative colitis and Crohn's are vastly different diseases.

The Role of Dietary Nutrients in Inflammatory Bowel Disease.

Inflammatory bowel disease (IBD) is a chronic and relapsing inflammatory disease of the gastrointestinal tract. Although the precise etiology of IBD remains incompletely understood, accumulating evidence suggests that various environmental factors, including dietary nutrients, contribute to its pathogenesis. Dietary nutrients are known to have an impact on host physiology and diseases. The interactions between dietary nutrients and intestinal immunity are complex. Dietary nutrients directly regulate the immuno-modulatory function of gut-resident immune cells. Likewise, dietary nutrients shape the composition of the gut microbiota. Therefore, a well-balanced diet is crucial for good health. In contrast, the relationships among dietary nutrients, host immunity and/or the gut microbiota may be perturbed in the context of IBD. Genetic predispositions and gut dysbiosis may affect the utilization of dietary nutrients. Moreover, the metabolism of nutrients in host cells and the gut microbiota may be altered by intestinal inflammation, thereby increasing or decreasing the demand for certain nutrients necessary for the maintenance of immune and microbial homeostasis. Herein, we review the current knowledge of the role dietary nutrients play in the development and the treatment of IBD, focusing on the interplay among dietary nutrients, the gut microbiota and host immune cells. We also discuss alterations in the nutritional metabolism of the gut microbiota and host cells in IBD that can influence the outcome of nutritional intervention. A better understanding of the diet-host-microbiota interactions may lead to new therapeutic approaches for the treatment of IBD.