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* = Presenting author

P097 MicroRNA23a is overexpressed in the colonic epithelium in Crohn’s disease

R. Felwick*1, G. Dingley1, T. Sanchez-Elsner1, J. Collins1, F. Cummings2

1University of Southampton, Clinical and Experimental Sciences, Southampton, United Kingdom, 2University Hospital Southampton, Gastroenterology, Southampton, United Kingdom

Background

The intestine is lined by a layer of epithelial cells. These form a selectively permeable barrier to luminal antigens and are vital in the innate immune regulation of the gut barrier. Responses are tightly controlled but become dysregulated in Crohn’s disease (CD), leading to increased intestinal permeability, inflammation, and diarrhoea. MicroRNAs are small non-coding RNA molecules, which repress protein translation. Change in microRNA expression has been implicated in pathogenesis of inflammatory bowel disease. However, detailed information concerning epithelial cell–specific expression of microRNA in CD is lacking, as current published studies focused on analysis of whole endoscopic biopsies. The aim of this study was to assay epithelial cell–specific expression of selected microRNA in CD, focusing on putative roles in epithelial barrier and innate immune regulation.

Methods

Colonic biopsies were collected under ethical approval, from 16 consenting patients with severe active CD and 10 healthy donors. Using laser capture microdissection (LCM), epithelial areas were isolated from biopsy sections. RT-qPCR was used to quantify expression of selected microRNAs (29a 29b 29c, 429, 19a, 19b, 23a, 24, and 27a). Protein expression and distribution was characterised immunohistochemically on serial sections. Binding of up-regulated microRNAs to their predicted mRNA targets was confirmed with luciferase reporter assays.

Results

Expression of microRNA 23a was found to be significantly up regulated in the colonic epithelium of CD patients compared with healthy controls. There was a positive correlation with increased stool frequency and Harvey–Bradshaw Index score. Bioinformatic analysis predicted that microRNA 23a could target the 3’UTR of mRNA encoding tumour necrosis factor-alpha inhibitory protein 3 (TNFAIP3), a cytosolic protein which negatively regulates NFκB signalling and deubiquitinates occludin to stabilise it in the tight junction. Luciferase reporter assays, utilising the 3’ UTR of TNFAIP3, confirmed that miRNA23a repressed translation in transfected epithelial cells. Immunohistochemical staining of TNFAIP3 showed a sub-apical, epithelial cell junction distribution, which was reduced or lost in adjacent CD sections, correlating inversely with microRNA 23a levels.

Conclusion

Increased microRNA23a in CD correlated with clinical severity, loss of TNFAIP3 at cell junctions, and increased stool frequency, a physical manifestation of gut barrier disruption. These novel data suggest that microRNA23a disrupts regulation of NFκB and gut barrier homeostasis, thus amplifying tumour necrosis factor-alpha responses and inflammation in Crohn’s disease.