Abstract
TNF-like Weak Inducer of Apoptosis (TWEAK) and Fn14 are TNF superfamily members that were reported to be elevated in colonic samples of UC patients. However, the precise role of TWEAK/Fn14 in intestinal inflammation is still not fully elucidated. The aim of this study was to determine the effects of genetic deletion of TWEAK/Fn14 in a model of CD-like ileitis (SAMP mice) as well as to analyze their levels in IBD patients compared to healthy controls (HC).
Ileal biopsies were collected from IBD and HC patients and analyzed for TWEAK/Fn14 expression by qPCR and immunohistochemistry (IHC). Severity of ileitis was evaluated at 10, 20 and 30 weeks of age in SAMPxFn14-/- mice and WT littermates by a histological scoring system. Stereomicroscopy was used to assess the percentage of injured ileal mucosa.
Intestinal mRNA expression of Fn14 and TWEAK was significantly upregulated in CD patients with active inflammation by 5.1-fold and 5.9-fold, respectively, (p<0.05, n=15/group) compared to UC and HC. These results were confirmed by Western blot analysis, showing increased protein levels of TWEAK/Fn14 in CD samples compared to UC and HC. IHC showed increased staining of TWEAK in CD biopsies compared to UC and HC. Histological scoring showed that SAMPxFn14-/- mice had decreased disease severity compared to WT littermates (4.18 ± 1.55vs.10.40 ± 1.01; p<0.02, n≥10/group) at 20 weeks, (11.23 ± 4.27vs.16.30 ± 2.16; p<0.02, n≥10/group) at 30 weeks, but not at 10 weeks of age (5.78 ± 0.59 vs. 6.43 ± 0.33; p=ns, n≥18/group). Stereomicroscopic analysis of ilea confirmed the histological results. The weight percentage of mesenteric lymph nodes was diminished in SAMPxFn14-/- mice (0.140 ± 0.0844 vs. 0.282 ± 0.0835; p<0.05, n≥6/group).
Our data indicate that Fn14 expression is increased in human CD and that Fn14 activation mediates intestinal inflammation in experimental ileitis; hence, blockade of Fn14 may serve as an innovative treatment for patients with IBD.
