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OP20. TNF and MDP induce epithelial-to-mesenchymal transition in human intestinal cells: Implications for the pathogenesis of Crohn's disease-associated fistulae and the use of anti‑TNF antibodies

M. Scharl1, S. Frei1, T. Pesch1, S. Kellermeier1, A. Weber2, E. Jehle3, G. Rogler1

1University Hospital Zürich, Clinic for Gastroenterology and Hepatology, Zurich, Switzerland; 2University Hospital Zürich, Department of Pathology, Zürich, Switzerland; 3Oberschwaben-Klinik, Department of Surgery, Ravensburg, Germany

Background: A common clinical complication of Crohn's disease (CD) are fistulae. Current treatment options include anti-TNF-antibodies and antibiotics. We have previously shown that epithelial to mesenchymal transition (EMT) plays a crucial role in the pathogenesis of CD fistulae. Here, we investigated a possible role for TNF and the bacterial wall component, muramyl-dipeptide (MDP) in the pathogenesis of CD-associated fistulae.

Methods: We analyzed 7 intestinal fistulae from 7 CD patients by immunohistochemistry (IHC) for Ets‑1 and dickkopf-homolog‑1 (DKK‑1). Primary human intestinal colonic lamina propria fibroblasts (CLPF) were isolated from CD patients with or without fistulising disease. mRNA levels were assessed by real-time PCR in CLPF or HT29 intestinal epithelial cells (IEC). Knock-down of Ets‑1 was induced by siRNA.

Results: By IHC, we found strong staining of Ets‑1 transcription factor and the Wnt-inhibitor, DKK‑1, in TC covering fistula tracts. TNF induced mRNA expression of Ets‑1 transcription factor in HT29-IEC (24 h, p < 0.01) and in CLPF from CD patients with fistulising (n = 4, p < 0.001; 24 h). This effect could be fully prevented by administration of an anti-TNF-antibody. TNF also induced mRNA levels of β6-integrin in HT29-IEC (72 h, p < 0.01). This effect was absent in Ets-1-deficient cells (24 h, p < 0.05) and could be effectively blocked by administration of anti‑TNF antibodies (p < 0.01). Interestingly, TNF decreased DKK‑1 mRNA levels in HT29 IEC (p < 0.05), but increased it in fistula CLPF. These effects were also sensitive to anti‑TNF treatment. In HT29-IEC, TNF induced mRNA levels of TNF (p < 0.001) and TGF β (p < 0.001), but not of IL‑13, SNAIL1 or SLUG by treatment for 24 h. In CLPF derived from CD patients, TNF-induced expression of β6-integrin (p < 0.05) and secretion of TGF β (p < 0.05) and IL‑8 (p < 0.01) could be significantly blocked by anti‑TNF treatment. Of note, the bacterial wall component, MDP, induced mRNA levels of Ets‑1 (p < 0.05), DKK‑1 (p < 0.05), TGF β (0.001), IL‑13 (p < 0.001), SNAIL1 (p < 0.05) and β6-integrin (p < 0.001) in HT29-IEC and fistula CLPF by treatment for 24 h.

Conclusions: TNF and MDP induce the expression of genes associated with EMT and invasive cell growth in IEC and fistula CLPF, whereby TNF-induced effects can be effectively blocked by anti‑TNF treatment. These findings indicate that TNF and bacterial components could synergize to induce EMT in IEC and, subsequently, cell invasion of EMT-cells, what finally leads to the development of fistulae during CD course.