MicroRNA23a Overexpression in Crohn's Disease Targets Tumour Necrosis Factor Alpha Inhibitor Protein 3, Increasing Sensitivity to TNF and Modifying the Epithelial Barrier.

BACKGROUND AND AIMS: Mucosal healing is important in Crohn's disease therapies. Epithelial homeostasis becomes dysregulated in Crohn's, with increased permeability, inflammation, and diarrhoea. MicroRNAs are small non-coding RNAs that regulate gene expression and show changes in inflammatory bowel disease. Tumour necrosis factor alpha [TNFα] inhibitor protein 3 is raised in Crohn's and regulates TNFα-mediated activation of NFκB. We investigated TNFα regulation by microRNA in Crohn's disease [CD], and studied effects on epithelial permeability and inflammation. METHODS: Colonic epithelium from CD and healthy donor biopsies was isolated using laser capture microdissection, and microRNA was quantified. Tumour necrosis factor alpha inhibitor protein 3 was characterised immunohistochemically on serial sections. Expression effect of microRNA was confirmed with luciferase reporter assays. Functional barrier permeability studies and innate cytokine release were investigated with cell and explant culture studies. RESULTS: MicroRNA23a levels significantly increased in colonic Crohn's epithelium compared with healthy epithelium. Luciferase reporter assays in transfected epithelial cells confirmed that microRNA23a repressed expression via the 3' untranslated region of tumour necrosis factor alpha inhibitor protein 3 mRNA, coinciding with increased NFκB-mediated transcription. Immunohistochemical staining of TNFAIP3 protein in colonic biopsies was reduced or absent in adjacent Crohn's sections, correlating inversely with microRNA23a levels and encompassing some intercohort variation. Overexpression of microRNA23a increased epithelial barrier permeability in a colonic epithelial model and increased inflammatory cytokine release in cultured explant biopsies, mimicking Crohn's disease characteristics. CONCLUSIONS: MicroRNA23a overexpression in colonic Crohn's epithelium represses tumour necrosis factor alpha inhibitor protein 3, enhancing sensitivity to TNFα, with increased intestinal permeability and cytokine release.

Biological therapy for the treatment of prepouch ileitis: a retrospective observational study from three centers.

AIM: Prepouch ileitis (PPI) is inflammation of the ileum proximal to an ileoanal pouch, usually associated with pouchitis. The treatment of PPI as a specific entity has been poorly studied, but it is generally treated concurrently with pouchitis. This to our knowledge is the largest study to explore the efficacy of biologics for the specific treatment of PPI. METHODS: This was a retrospective observational study reporting outcomes following biological treatment in patients with PPI across three centers. Data were collected between January 2004 and February 2018 from two centers in the UK and one center in Italy. Outcomes included the continued presence of PPI following biologic therapy, pouch failure defined by the need for an ileostomy, and remission of PPI defined by the absence of any prepouch inflammation on endoscopic assessment within a year of biologic therapy. RESULTS: There were 29 patients in our cohort. On last endoscopic follow-up, 20/29 still had endoscopic evidence of PPI, seven had achieved endoscopic remission and avoided an ileostomy, and two had no endoscopic follow-up. In our cohort 11 patients had an ileostomy after a median time from starting a biologic of 25 months (range 14-91). CONCLUSION: Biologics fail to induce endoscopic remission of PPI in the majority of patients. Just under one-third patients with PPI coexistent with pouchitis can achieve endoscopic remission with biologics. In a large proportion of patients with PPI, surgery may be required despite biologic use.