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Inflammation-induced endothelial-to-mesenchymal transition: a novel mechanism of intestinal fibrosis.

ABSTRACT: In addition to mesenchymal cells, endothelial cells may contribute to fibrosis through the process of endothelial-to-mesenchymal transition (EndoMT). We investigated whether human intestinal microvascular endothelial cells (HIMEC) undergo EndoMT and contribute to fibrosis in human and experimental inflammatory bowel disease (IBD). HIMEC were exposed to TGF-?1, IL-1?, and TNF-? or supernatants of lamina propria mononuclear cells (LPMC) and evaluated for morphological, phenotypic, and functional changes compatible with EndoMT. Genomic analysis was used to identify transcription factors involved in the transformation process. Evidence of in situ and in vivo EndoMT was sought in inflamed human and murine intestine. The combination of TGF-?1, IL-1? and TNF-?, or activated LPMC supernatants induced morphological and phenotypic changes consistent with EndoMT with a dominant effect by IL-1. These changes persisted after removal of the inducing agents and were accompanied by functional loss of acetylated LDL-uptake and migratory capacity, and acquisition of de novo collagen synthesis capacity. Sp1 appeared to be the main transcriptional regulator of EndoMT. EndoMT was detected in microvessels of inflammatory bowel disease (IBD) mucosa and experimental colonic fibrosis of Tie2-green fluorescent protein (GFP) reporter-expressing mice. In conclusion, chronic inflammation induces transdifferentiation of intestinal mucosal microvascular cells into mesenchymal cells, suggesting that the intestinal microvasculature contributes to IBD-associated fibrosis through the novel process of EndoMT.

SUBMITTER: Rieder F

PROVIDER: S-EPMC3204019 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature

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Inflammation-induced endothelial-to-mesenchymal transition: a novel mechanism of intestinal fibrosis.

Rieder Florian F Kessler Sean P SP West Gail A GA Bhilocha Shardul S de la Motte Carol C Sadler Tammy M TM Gopalan Banu B Stylianou Eleni E Fiocchi Claudio C

The American journal of pathology 20110921 5

In addition to mesenchymal cells, endothelial cells may contribute to fibrosis through the process of endothelial-to-mesenchymal transition (EndoMT). We investigated whether human intestinal microvascular endothelial cells (HIMEC) undergo EndoMT and contribute to fibrosis in human and experimental inflammatory bowel disease (IBD). HIMEC were exposed to TGF-β1, IL-1β, and TNF-α or supernatants of lamina propria mononuclear cells (LPMC) and evaluated for morphological, phenotypic, and functional c ...[more]

PMID: 21945322

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Project description:Intraflagellar transport protein 88 (Ift88) is required for ciliogenesis and shear stress-induced dissolution of cilia in embryonic endothelial cells coincides with endothelial-to-mesenchymal transition (EndMT) in the developing heart. EndMT is also suggested to underlie heart and lung fibrosis, however, the mechanism linking endothelial Ift88, its effect on EndMT and organ fibrosis remains mainly unexplored. We silenced Ift88 in endothelial cells (ECs) in vitro and generated endothelial cell-specific Ift88-knockout mice (Ift88endo) in vivo to evaluate EndMT and its contribution towards organ fibrosis, respectively. Ift88-silencing in ECs led to mesenchymal cells-like changes in endothelial cells. The expression level of the endothelial markers (CD31, Tie-2 and VE-cadherin) were significantly reduced with a concomitant increase in the expression level of mesenchymal markers (αSMA, N-Cadherin and FSP-1) in Ift88-silenced ECs. Increased EndMT was associated with increased expression of profibrotic Collagen I expression and increased proliferation in Ift88-silenced ECs. Loss of Ift88 in ECs was further associated with increased expression of Sonic Hedgehog signaling effectors. In vivo, endothelial cells isolated from the heart and lung of Ift88endo mice demonstrated loss of Ift88 expression in the endothelium. The Ift88endo mice were born in expected Mendelian ratios without any adverse cardiac phenotypes at baseline. Cardiac and pulmonary endothelial cells isolated from the Ift88endo mice demonstrated signs of EndMT and bleomycin treatment exacerbated pulmonary fibrosis in Ift88endo mice. Pressure overload stress in the form of aortic banding did not reveal a significant difference in cardiac fibrosis between Ift88endo mice and control mice. Our findings demonstrate a novel association between endothelial cilia with EndMT and cell proliferation and also show that loss of endothelial cilia-associated increase in EndMT contributes specifically towards pulmonary fibrosis.

Project description:Background and aimsRecent 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.MethodsColonic 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.ResultsHigh 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-β1/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.ConclusionsTL1A 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.

Project description:Macroautophagy/autophagy plays a vital role in the homeostasis of diverse cell types. Vascular endothelial cells contribute to vascular health and play a unique role in vascular biology. Here, we demonstrated that autophagy defects in endothelial cells induced IL6 (interleukin 6)-dependent endothelial-to-mesenchymal transition (EndMT) and organ fibrosis with metabolic defects in mice. Inhibition of autophagy, either by a specific inhibitor or small interfering RNA (siRNA) for ATG5 (autophagy related 5), in human microvascular endothelial cells (HMVECs) induced EndMT. The IL6 level was significantly higher in ATG5 siRNA-transfected HMVECs culture medium compared with the control HMVECs culture medium, and neutralization of IL6 by a specific antibody completely inhibited EndMT in ATG5 siRNA-transfected HMVECs. Similar to the in vitro data, endothelial-specific atg5 knockout mice (Atg5 Endo; Cdh5-Cre Atg5 flox/flox mice) displayed both EndMT-associated kidney and heart fibrosis when compared to littermate controls. The plasma level of IL6 was higher in Atg5 Endo compared to that of control mice, and fibrosis was accelerated in Atg5 Endo treated with a HFD; neutralization of IL6 by a specific antibody inhibited EndMT and fibrosis in HFD-fed Atg5 Endo associated with the amelioration of metabolic defects. These results revealed the essential role of autophagy in endothelial cell integrity and revealed that the disruption of endothelial autophagy could lead to significant pathological IL6-dependent EndMT and organ fibrosis. Abbreviations: 3-MA: 3-methyladenine; ATG5: autophagy related 5; EndMT: endothelial-to-mesenchymal transition; HES: hematoxylin and eosin stain; HFD: high-fat diet; HMVECs: human microvascular endothelial cells; IFNG: interferon gamma; IL6: interleukin 6; MTS: Masson's trichrome staining; NFD: normal-fat diet; siRNA: small interfering RNA; SMAD3: SMAD family member 3; TGFB: transforming growth factor β; TNF: tumor necrosis factor; VEGFA: vascular endothelial growth factor A.

Dataset Information

Inflammation-induced endothelial-to-mesenchymal transition: a novel mechanism of intestinal fibrosis.

Publications

Inflammation-induced endothelial-to-mesenchymal transition: a novel mechanism of intestinal fibrosis.

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