LAUSR

&NA; Intestinal subepithelial myofibroblasts (SEMFs) exert a profibrotic role in Crohn's disease (CD). Tumor necrosis factor‐like cytokine 1A (TL1A) and its receptors, death‐domain receptor 3 (DR3) and decoy receptor 3 (DcR3), are mucosal factors with significant involvement in experimental inflammation and CD. We aimed to determine the regulation of expression of this system of proteins in SEMFs and intestinal epithelial cells. The relative amount of mRNA transcripts for TL1A, DR3, and DcR3 was measured by real‐time reverse transcription polymerase chain reaction in cultured primary SEMFs, colonic myofibroblast cell line 18CO, and epithelial cell line HT29. Protein expression was determined by immunofluorescence. The effect of various proinflammatory stimuli in mRNA and protein expression was studied. TL1A mRNA and protein expression in primary SEMFs (and 18CO cells) was significantly upregulated after stimulation with interleukin 1‐alpha and/or tumor necrosis factor alpha (TNF‐&agr;) (32‐ to 44‐fold increase, P < 0.05 vs unstimulated). Following stimulation with interleukin 1‐alpha + TNF‐&agr; + IFN‐&ggr;, HT‐29 cells highly expressed DR3 (4.1‐fold over unstimulated, P = 0.008) and DcR3 (56‐fold, P = 0.009) and secreted soluble factors that led to induction of TL1A mRNA in primary SEMFs (28‐fold, P = 0.008). Activated epithelial cells significantly upregulated IL‐8 expression in response to stimulation with recombinant TL1A. Supernatants from mucosal cultures of patients with CD were able to stimulate the expression of TL1A in cultured primary SEMFs, in comparison to supernatants from healthy controls (3.8‐fold increase, P < 0.05) or culture media alone (P < 0.05). In conclusion, we found that proinflammatory cytokines are important regulators of the expression of TL1A in SEMFs and of its receptors in intestinal epithelial cells. Our results raise the possibility for involvement of TL1A/DR3/DR3‐mediated mechanisms in epithelial‐mesenchymal interactions and the development of inflammation‐induced intestinal fibrosis in CD.