Small bowel fibrosis and systemic inflammatory response after ileocolonic anastomosis in IL-10 null mice

Knockout Genes in Bowel Anastomoses: A Systematic Review of Literature Outcomes

BACKGROUND

The intestinal wound healing process is a complex event of three overlapping phases: exudative, proliferative, and remodeling. Although some mechanisms have been extensively described, the intestinal healing process is still not fully understood. There are some similarities but also some differences compared to other tissues. The aim of this systematic review was to summarize all studies with knockout (KO) experimental models in bowel anastomoses, underline any recent knowledge, and clarify further the cellular and molecular mechanisms of the intestinal healing process. A systematic review protocol was performed.

MATERIALS AND METHODS

Medline, EMBASE, and Scopus were comprehensively searched.

RESULTS

a total of eight studies were included. The silenced genes included interleukin-10, the four-and-one-half LIM domain-containing protein 2 (FHL2), cyclooxygenase-2 (COX-2), annexin A1 (ANXA-1), thrombin-activatable fibrinolysis inhibitor (TAFI), and heparin-binding epidermal growth factor (HB-EGF) gene. Surgically, an end-to-end bowel anastomosis was performed in the majority of the studies. Increased inflammatory cell infiltration in the anastomotic site was found in IL-10-, annexin-A1-, and TAFI-deficient mice compared to controls. COX-1 deficiency showed decreased angiogenesis at the anastomotic site. Administration of prostaglandin E2 in COX-2-deficient mice partially improved anastomotic leak rates, while treatment of ANXA1 KO mice with Ac2-26 nanoparticles reduced colitis activity and increased weight recovery following surgery.

CONCLUSIONS

our findings provide new insights into improving intestinal wound healing by amplifying the aforementioned genes using appropriate gene therapies. Further research is required to clarify further the cellular and micromolecular mechanisms of intestinal healing.

Prebiotic Supplementation Following Ileocecal Resection in a Murine Model is Associated With a Loss of Microbial Diversity and Increased Inflammation

BACKGROUND

Individuals with Crohn's disease frequently require ileocecal resection (ICR), and inflammation often recurs in the neoterminal ileum following surgery. Fructooligosaccharide (FOS) is a fermentable prebiotic that stimulates the growth of bifidobacteria and may promote anti-inflammatory activity. The aim of this study was to determine if supplementation of a postICR diet with FOS in a mouse model would be effective in stimulating the growth of bifidobacteria and reducing systemic and local inflammation.

METHODS

ICR was performed in IL10-/- mice (129S1/SvlmJ) with colitis. Following surgery, nonICR control and ICR mice were fed a chow diet ± 10% FOS for 28 days. Serum, colon, and terminal ileum (TI) were analyzed for cytokine expression by MesoScale discovery platform. DNA extracted from stool was analyzed using 16s rRNA sequencing and qPCR. Expression of occludin and ZO1 was assessed using qPCR. Short-chain fatty acid (SCFA) concentrations were assessed using gas chromatography.

RESULTS

ICR led to increased systemic inflammation (P < 0.05) and a significant decline in fecal microbial diversity (P < 0.05). Mice on the FOS diet had a greater reduction in microbial diversity and also had worsened inflammation as evidenced by increased serum IL-6 (P < 0.05) and colonic IFNγ and TNFα (P < 0.05). Expression of occludin and ZO1 were significantly reduced in FOS-supplemented mice. There was a correlation between loss of diversity and the bifidogenic effectiveness of FOS (r = -0.61, P < 0.05).

CONCLUSIONS

FOS-supplementation of a postICR diet resulted in a decrease in fecal bacterial diversity, reduction in barrier function, and increased gut inflammation.

Triptolide exerts protective effects against fibrosis following ileocolonic anastomosis by mechanisms involving the miR-16-1/HSP70 pathway in IL-10-deficient mice

Surgeries, particularly ileocecal resection (ICR), are often required in the treatment of Crohn's disease (CD). However, recurrences are common for patients who undergo ICR, and anastomotic fibrosis is the main cause of re-operation. The present study aimed to investigate the therapeutic effects of triptolide (TPL) in ameliorating fibrosis following ileocolonic anastomosis. A model of IL-10^−/− mice undergoing ICR was used to study post surgical inflammation and fibrosis of anastomosis. For this purpsose, interleukin (IL)-10^−/− mice were randomly divided into 3 groups as follows: the control group, the saline-treated group subjected to ICR (ST-ICR) and the TPL-treated group subjected to ICR (TT-ICR). Wild-type (WT) mice of matching ages were assigned to the WT group. The effects of TPL treatment on ileocolonic anastomosis were determined by histopathological evaluation, western blot analysis and ELISA. The analysis of the effects of TPL treatment on microRNA-16-1 (miR-16-1) and heat shock protein 70 (HSP70) expression was carried out by RT-qPCR and western blot analysis. Compared with the control group, significantly higher inflammation scores following anastomosis were observed in the ST-ICR group (P<0.05), although reversion was observed in the TT-ICR group, which was consistent with changes in the area of CD₄⁺ cell infiltration. The elevated fibrosis scores and the overexpression of procollagen I and III in the ST-ICR group were all inhibited by TPL. With an increase in the severity of inflammation and fibrosis, the levels of IL-6, tumor necrosis factor-α (TNF-α) and transforming growth factor-β1 (TGF-β1) increased; however, a significant decrease in these levels was observed following treatment with TPL (P<0.05). The results of RT-qPCR revealed that the upregulated miR-16-1 levels in the ST-ICR group were significantly reduced by TPL. HSP70, which can be inhibited by miR-16-1, ameliorates anastomotic inflammation and fibrosis. Thus, the present study demonstrates that TPL exerts a protective effect against fibrosis following anastomosis in CD. The miR-16-1/HSP70 signaling pathway, which can be regulated by TPL, may thus represent a novel therapeutic option in CD that deserves further investigation.

Fecal Microbial Transplant After Ileocolic Resection Reduces Ileitis but Restores Colitis in IL-10-/- Mice

BACKGROUND

Ileocolic resection (ICR) is frequently performed for Crohn's disease; however, disease commonly recurs early in the neoterminal ileum. The aim of this study was to use the IL-10(-/-) mouse to determine the effects of ICR on gut microbiome and immune function and if postoperative fecal microbial transplant (FMT) would improve disease.

METHODS

ICR was performed in 129S1/SvlmJ IL10(-/-) mice followed by FMT using stool from wild-type mice. Sham-transplant mice received their own stool. Stool samples were collected on day 0, day 13 (after ICR), and day 27 (after FMT) for whole metagenome shot-gun sequencing. Mucosal-associated bacteria were quantified with quantitative PCR and visualized by fluorescent in situ hybridization. Tissue cytokines were measured with multiplex arrays and mononuclear phagocyte populations by flow cytometry.

RESULTS

Surgery induced microbial functional and taxonomic shifts, decreased diversity, and depleted Bacteroidia and Clostridia. ICR mice had reduced colitis but worse ileitis with bacterial overgrowth, increased translocation, and reduction in tissue macrophages. FMT prevented ileitis but restored colitis and allowed for a bloom of γ-proteobacteria. In the colon, ICR and sham transplant were associated with recruitment of tolerogenic dendritic cells, whereas FMT shifted these immune cell subsets to control profiles along with increasing cytokine levels.

CONCLUSIONS

This study suggests that surgical-induced immune dysfunction and microbial dysbiosis with impaired clearance may be the underlying cause of the early ulcerations found in the ileum of patients with Crohn's disease after ICR. FMT has an immunostimulatory effect on the postoperative intestine, which was beneficial in preventing ileitis, but detrimental in restoring colonic injury after surgery.

Histologic features predicting postoperative Crohn's disease recurrence

Recurrence of Crohn's disease (CD) after ileal or colonic resection is common. Many studies have tried to identify predictors of postoperative recurrence (POR) in CD. A wide range of histologic features have been identified, but for most of them, the literature provided conflicting data. In last years, several studies have suggested that histologic findings including inflammatory changes within the enteric nervous system of the resection margin may be associated with CD recurrence. Herein, after briefly summarizing pathophysiology of POR, we review all histological features that have been studied so far: granulomas, histologic appearance at the margin of resection, plexitis, lymphatic vessel density in proximal margin of resection, and morphological analysis of Paneth cells. Granulomas and chronic inflammation at the margin of resection do not seem to predict POR in CD. Active disease at the margin of resection, plexitis, lymphatic vessels density, morphological analysis of Paneth cells may predict POR. Most of these histological features await replication in independent studies. Available evidence indicates that histological findings may be taken into account when developing strategies aimed at preventing postoperative CD recurrence.

Change and significance of IL-8, IL-4, and IL-10 in the pathogenesis of terminal Ileitis in SD rat

The objective of the study is to explore change and significance of IL-8, IL-4 and IL-10 in the pathogenesis of terminal Ileitis in SD rat. 60 male SD rats were divided into model group, suture group, and control group equally. The rats subjected to ileum-cecum side-to-side anastomosis in terminal ileum in model group, suture in terminal ileum in suture group, and the control group accepted no special treatment. The terminal ileum tissue which was 1-3 cm from anastomotic stoma was collected at 2 and 8 weeks after surgery in each group. The pathological slice was observed under microscope, and PCR was applied to detect the expression of IL-4, IL-8, and IL-10 at different times. Pathological result showed that neutrophils significantly increased in model group and suture group at 2nd week, showing acute inflammatory reaction; model group showed chronic inflammation at 8th week. The change of IL-8, IL-4, and IL-10 expression level at 2 weeks after surgery: The IL-8 expression level of SD rat terminal ileum tissue in model group was significantly higher than in control and suture groups (P < 0.01), and it was higher in suture group compared to control group (P < 0.01); the expression level of IL-4 in control group was higher than model and suture groups (P < 0.05); there was no statistical significance between model group and suture group (P = 0.363); the expression level of IL-10 in control group was higher than in model and suture groups (P < 0.01), and it was higher in suture group compared to model group (P < 0.01). The change of IL-8, IL-4, IL-10 expression level at 8 weeks after surgery: The expression level of IL-8 significantly decreased in model group, and there was no significantly difference between three groups (P > 0.05); the expression level of IL-4 was higher in model group and suture group compared to 2nd week; there was no significance between three groups (P < 0.05); the expression of IL-10 was higher in model group compared to 2nd week (P < 0.01), it was lower than control group and suture group (P < 0.01); there was no significant difference between suture group and control group (P > 0.05). The chronic terminal ileum model could be successfully established by ileum-cecum side-to-side anastomosis in terminal ileum in SD rats; IL-8 can induce the inflammatory reaction in terminal ileitis and chemokines aggregation and mediate inflammatory reaction by mediating other inflammatory factors; as a proinflammatory cytokine, IL-8 can inhibit IL-10; IL-10 and IL-4 can inhibit the inflammatory reaction of terminal ileum.

Murine ileocolic bowel resection with primary anastomosis

Intestinal resections are frequently required for treatment of diseases involving the gastrointestinal tract, with Crohn's disease and colon cancer being two common examples. Despite the frequency of these procedures, a significant knowledge gap remains in describing the inherent effects of intestinal resection on host physiology and disease pathophysiology. This article provides detailed instructions for an ileocolic resection with primary end-to-end anastomosis in mice, as well as essential aspects of peri-operative care to maximize post-operative success. When followed closely, this procedure yields a 95% long-term survival rate, no failure to thrive, and minimizes post-operative complications of bowel obstruction and anastomotic leak. The technical challenges of performing the procedure in mice are a barrier to its wide spread use in research. The skills described in this article can be acquired without previous surgical experience. Once mastered, the murine ileocolic resection procedure will provide a reproducible tool for studying the effects of intestinal resection in models of human disease.