Introduction UC is thought to be characterised by a TH-2 predominant immune response. MicroRNAs (miRNA) are short 19–23 nucleotide long strands of single-stranded RNA which modify post transcriptional gene expression by degrading or inhibiting translation of mRNA. miR31 and miR155 are miRNA that directly and indirectly target genes in the IL-13 dependant pathway.

Confounding factors in current IBD miRNA studies include disease activity and medication. The specific function of miRNAs in UC, how they might be influenced by medications, and potential clinical utility is yet to be investigated.

In this study we aim to investigate how the expression of a number of miRNA and mRNA is influenced by medications and then explore these findings further using a human ex-vivo culture system.

Method Sigmoid biopsies from 40 patients with untreated active and inactive UC, normal controls, and patients treated with 5-ASA, Azathioprine, Infliximab and Adalimumab were frozen in liquid nitrogen. RT-qPCR was performed to analyse the relative expression of miRNA and mRNA.

An ex vivomodel was designed. 6 biopsies were taken from 8 patients with active untreated UC, with a Mayo score of 6 or greater. Biopsies were placed in tissue culture media in 6 separate wells with either no treatment, 5-ASA, 6-TG, Infliximab, or Adalimumab, were incubated for 24hrs at 37^oC. RT-qPCR was performed to assess expression of miR31 and miR155 and mRNA of CCL18 and SOCS1 that are important in the TH-2 pathway.

Results miR31 and miR155 expression was increased in patients with untreated active and inactive UC compared to normal mucosa. CCL18 expression was also increased in untreated active disease compared to inactive and normal mucosa. Azathioprine reduced miR31, miR155 and CCL18 expression to levels seen in quiescent disease. Infliximab treatment reduced miR155, and CCL18 expression to that of inactive disease, which was not seen in Adalimumab. Anti-TNFs did not reduce miR31 expression to the level of untreated inactive disease. 5ASAs had no impact on expression of the miRNA nor mRNA studied.

Ex vivotreated samples confirmed down regulation of miR31 was confined to 6-TG and not seen in anti-TNF treatment, and that CCL18 expression is also reduced by 6-TG and Infliximab, but not Adalimumab.

Conclusion Our data confirmed that miR31 miR155 and CCL18 are increased in active UC compared to normal mucosa and inactive disease. We demonstrate that thiopurine therapy reduces expression of miR31 and CCl18 in contrast to anti-TNF agents.

This model may have utility in increasing understanding of the mechanisms of action of IBD medications. It highlights the importance of controlling for medication when analysing miRNA expression in whole tissue biopsies.

Disclosure of interest None Declared.