Sensitivity of intestinal fibroblasts to TNF-related apoptosis-inducing ligand-mediated apoptosis in Crohn's disease.

OBJECTIVE

Strictures and fistulas are common complications of Crohn's disease (CD). Collagen deposit and fibroblast proliferation can contribute to their development. Tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) binds two pro-apoptotic (TRAIL-R1, TRAIL-R2) and three anti-apoptotic (TRAIL-R3, TRAIL-R4, osteoprotegerin (OPG)) receptors. The aim of this work was to study TRAIL expression and the effects on intestinal fibroblasts (IFs) in CD.

MATERIAL AND METHODS

Intestinal samples from 25 CD (with or without fibrostenosing areas) and 38 control patients (with or without inflammation) were used. TRAIL, TRAIL R2 and TRAIL R3 expression in the intestine and in human IFs was studied by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and immunostaining in IF and intestinal samples. TRAIL-induced IF cell death was studied in the presence or absence of OPG and cytokines. Western blots for poly ADP-ribose polymerase (PARP) and caspase-8 were performed to confirm apoptosis in IFs.

RESULTS

Transcripts for TRAIL and its receptors were confirmed in the intestine. Immunostaining showed intestinal expression of TRAIL, TRAIL-R2 and TRAIL-R3 in fibroblasts, immune cells and epithelial cells, mainly in fibrostenosing areas. TRAIL-R3 mRNA expression was lower in IFs from fibrostenosing CD. The sensitivity of IFs to TRAIL-mediated apoptosis was higher in the fibrostenosing areas of CD. The effect of TRAIL was decreased by IL-6 and its soluble receptor and almost completely reversed by OPG in the CD patients involved.

CONCLUSIONS

TRAIL is expressed in the intestine and influences fibroblast survival. Variations in TRAIL expression and in TRAIL-mediated apoptosis could be involved in the tissue remodelling associated with CD.