Importance of TLR9-IL23-IL17 axis in inflammatory bowel disease development: Gene expression profiling study

Mucosal gene expression have not been fully enlightened in inflammatory bowel disease (IBD). Aim of this study was to define IL23A, IL17A, IL17F and TLR9 expression in different IBD phenotypes. Evaluation of mRNA levels was performed in paired non-inflamed and inflamed mucosal biopsies of newly diagnosed 50 Crohn's disease (CD) and 54 ulcerative colitis (UC) patients by quantitative real-time PCR analysis. IL17A and IL17F expression levels were significantly increased in inflamed IBD mucosa. Inflamed CD ileal and UC mucosa showed increased IL23A, while only inflamed CD ileal samples showed increased TLR9 mRNA level. Correlation between analysed mRNAs levels and endoscopic and clinical disease activity were found in UC, but only with clinical activity in CD. Both CD and UC presented expression of Th17-associated genes. Nevertheless, expression profiles between different disease forms varies which should be taken into account for future research and therapeutics strategies. •Upregulated IL17A and IL17F expression was demonstrated in inflamed IBD mucosa.•Upregulated TLR9 and IL23A expression was observed for inflamed CD ileum.•Upregulated IL23A expression was found in inflamed UC colon.•Analysed mRNA levels correlated with clinical and endoscopic disease activity scores.•Analysed mRNA levels in non-inflamed gut mucosa may indicate severe IBD course.