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Role of Altered Expression of miR-146a, miR-155, and miR-122 in Pediatric Patients with Inflammatory Bowel Disease

Background:Evidence suggests the central role of tumor necrosis factor (TNF)-&agr; in the pathomechanism of inflammatory bowel disease (IBD); however, its effect on epigenetic factors, including small non-coding microRNAs (miRs), is less known. Our present aim was the comparative investigation of the expression of TNF-&agr; and immune response–related miRs in children with Crohn's disease (CD) and ulcerative colitis (UC). Methods:Fresh-frozen (FF) and formalin-fixed, paraffin-embedded (FFPE) biopsies were used to analyze the expression of miR-146a, -155, -122, and TNF-&agr; by real-time reverse transcription polymerase chain reaction in macroscopically inflamed (CD: 12 FFPE and 24 FF; UC: 10 FF) and intact (CD: 12 FFPE; 14 FF) colonic biopsies of children with IBD and controls (16 FFPE; 23 FF). The expression of miR-146a, -155, and -122 was also determined in TNF-&agr;–treated HT-29 colonic epithelial cells. Results:Increased expression of TNF-&agr; was observed in the colonic mucosa of children with CD and UC in comparison with controls. Expression of miR-146a and -155 was higher in the inflamed mucosa of children with CD and UC than in the intact mucosa. Expression of miR-122 elevated in the macroscopically intact colonic regions of CD compared with controls and patients with UC. In HT-29 cells, TNF-&agr; treatment increased the expression of miR-146a and -155, but not that of miR-122. Conclusions:Our results showed altered expression of miR-146a, -155, and -122 in the colonic mucosa of children with IBD and in TNF-&agr;–treated colonic epithelial cells. Our data suggest the TNF-&agr;–related involvement of these miRs in the pathogenesis of IBD.