Effect and Mechanism of TL1A Expression on Epithelial-Mesenchymal Transition during Chronic Colitis-Related Intestinal Fibrosis.

BACKGROUND AND AIMS: Recent evidences reveal that epithelial to mesenchymal transition (EMT) exacerbates the process of intestinal fibrosis. Tumor necrosis factor-like ligand 1A (TL1A) is a member of the tumor necrosis family (TNF), which can take part in the development of colonic inflammation and fibrosis by regulating immune response or inflammatory factors. The purpose of this study was to elucidate the possible contribution of TL1A in onset and progression of intestinal inflammation and fibrosis through EMT. METHODS: Colonic specimens were obtained from patients with inflammatory bowel disease (IBD) and control individuals. The expression levels of TL1A and EMT-related markers in intestinal tissues were evaluated. Furthermore, the human colorectal adenocarcinoma cell line, HT-29, was stimulated with TL1A, anti-TL1A antibody, or BMP-7 to assess EMT process. In addition, transgenic mice expressing high levels of TL1A in lymphoid cells were used to further investigate the mechanism of TL1A in intestinal fibrosis. RESULTS: High levels of TL1A expression were detected in the intestinal specimens of patients with ulcerative colitis and Crohn's disease and were negatively associated with the expression of an epithelial marker (E-cadherin), while it was positively associated with the expression of interstitial markers (FSP1 and α-SMA). Transgenic mice with high expression of TL1A were more sensitive to dextran sodium sulfate and exhibited severe intestinal inflammation and fibrosis. Additionally, the TGF-ß1/Smad3 pathway may be involved in TL1A-induced EMT, and the expression of IL-13 and EMT-related transcriptional molecules (e.g., ZEB1 and Snail1) was increased in the intestinal specimens of the transgenic mice. Furthermore, TL1A-induced EMT can be influenced by anti-TL1A antibody or BMP-7 in vitro. CONCLUSIONS: TL1A participates in the formation and process of EMT in intestinal fibrosis. This new knowledge enables us to better understand the pathogenesis of intestinal fibrosis and identify new therapeutic targets for its treatment.

Role and mechanism of tumor necrosis factor ligand-related molecule 1A in chronic experimental colitis associated intestinal fibrosis / 中华消化杂志

Objective To explore the role and mechanism of tumor necrosis factor ligand -related molecule 1A (TL1A) in chronic experimental colitis associated intestinal fibrosis .Methods The model of chronic experimental colitis-associated intestinal fibrosis was induced by dextran sodium sulfate (DSS).The mice with high TL1A (L-Tg) expression in lymphoid cells and wild -type mice with the same genetic background were divided into wild type control group, wild type DSS group, transgenic control group and transgenic DSS group.The changes of body mass, length of colon, disease activity index (DAI) and colonic pathological score were compared among different groups .The degree of colonic inflammation was evaluated by Hematoxylin -Eosin (H-E) staining.The degree of intestinal fibrosis was assessed by Masson staining and Sirius red staining .The expression of vimentin, αsmooth muscle actin ( α-SMA), type Ⅰ collagen, Ⅲ collagen and transforming growth factor-β1 ( TGF-β1 ) /Smad3 in colon tissue was examined by immunohistochemistry .T test was performed for statistical analysis.Results The body mass of the transgenic DSS group decreased by (9.6 ± 1.8)％, which was more than wild-type DSS group (6.2 ±1.3)％, the difference was statistically significant (t =3.751, P <0.01).The DAI score and colonic pathological score of transgenic DSS group were both higher than those of wild-type DSS group (7.33 ±0.58 vs.6.00 ±1.00, and 14.00 ±1.05 vs.11.75 ±0.50, respectively), and the differences were statistically significant (t =2.818 and 4.739, both P <0.05).The results of Masson staining and Sirius red staining showed aggravation of intestinal fibrosis .The results of immunohistochemical staining showed that the cumulative positive absorbance values of vimentin , α-SMA, TGF-β1 and Smad3 of wild-type DSS group were lower than those of transgenic DSS group (0.650 ±0.050 vs. 0.800 ±0.020, 0.390 ±0.040 vs.0.600 ±0.040, 0.550 ±0.040 vs.0.730 ±0.040, 0.590 ±0.020 vs. 0.830 ±0.040), and the differences were statistically significant (t =6.823, 9.093, 7.794 and 10.390, all P <0.01).Conclusion TL1A may promote the proliferation and activation of fibroblasts through TGF -β1 /Smad3 pathway, leading to the genesis and development of experimental colitis associated intestinal fibrosis .