P008 Targeting of TSLP by miR-31 may play an important role in mucosal healing, in ulcerative colitis.
S. Whiteoak*1, 2, A. Claridge1, 3, T. Sanchez-Elsner*1, J. F. Cummings2
1University of Southampton, Clinical and Experimental Sciences, Southampton, United Kingdom, 2University of Southampton, Department of Gastroenterology, Southampton, United Kingdom, 3Great Western Hospitals NHS Foundation Trust, Department of Gastroenterology, Swindon, United Kingdom
The immunological response in UC is characterised by cytokines secreted during a TH2 type response. Thus here increased levels of IL5 and IL13 are seen. MicroRNAs (miR) are short nucleotide strands of RNA which function by modifying post transcriptional gene expression by inhibiting the translation of mRNA. Bioinformatic searches and our own qPCR correlations in active UC tissue have shown that miR31 targets genes within the IL13 dependant pathway. TSLP is predicted to be one such target of miR31 that plays an important role in the IL13 dependant pathway. TSLP is a cytokine that is critical in TH2 type inflammation.
Using RT-qPCR, we determined the expression of miR31 and TSLP in the biopsy samples of 72 patients with moderate to severe UC before and after treatment with Tralokinumab (Tk), an antiIL13 monoclonal antibody, used in a clinical trial setting. We went on to evaluate the TSLP protein and mRNA levels in active UC, inactive UC, and normal mucosa, by performing ELISA and qPCR on both whole biopsy specimens and isolated T-cell fractions from mucosal biopsies. This mechanism of TSLP targeting by miR31 was then proved by performing Dual Luciferase Assays on clones in HeLa cells.
miR31 showed significant increased expression in active tissue compared with inactive tissue. The pretreatment levels of miR31 predict clinical remission and mucosal healing, in these patients. The reduction in miR31 in active mucosa that undergoes mucosal healing is confined to the patients who are treated with Tk. TSLP expression is significantly increased in the mucosa of UC that has undergone mucosal healing by treatment with Tk. TSLP protein concentration is reduced in the biopsies of active and inactive UC compared with healthy controls. TSLP protein and mRNA is decreased in the isolated T-cell fractions of biopsies from active UC compared with healthy controls. There is an inverse relationship between the expression of miR31 and TSLP mRNA. There is a 70% reduction in luciferase activity in TSLP clones transfected with miR31.
There is no doubt that UC is a complex disease that has yet to be explained by a single unifying theory. In our analysis, miR31 showed potential as a biomarker to predict whether clinical response or mucosal healing could be achieved with Tk. The increased expression of miR31 in UC actively decreases the expression of TSLP. The finding of decreased TSLP expression in UC is important because it provides a mechanism for several disordered features of UC such as; the disordered response to luminal antigens, and the breakdown of regulation of the epithelial barrier. Understanding the role of TSLP in acquired immunity and regulation of T-cell responses could provide possible new therapeutic options.
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