Clinical Observation And Experimental Research Of Determining The Level Of Insulin-like Factor-1 In Crohn’s Disease

Part 1 Clinical observation of determining the level of insulin-like factor-1 in Crohn’s diseaseBackground: Intestinal fibrosis is the most common and severe complication of inflammatory bowel disease. Stricture development in Crohn’s disease is transmural and culminates in excessive extracellular matrix(ECM) initiated by chronic inflammation and wound healing deposition in each layer of the intestinal wall, eventually narrowing of the intestinal lumen. Insulin-like growth factor-1(IGF-1) is a member of Insulin-like growth factor systems, which is an important profibrotic cytokine. Overexpression of IGF-1 can stimulate intestinal fibroblast proliferation, differentiation and synthesis of collagens, playing an important role in the process of organ fibrosis. Matrix metalloproteinase-2, 9(MMP-2, 9) are members of the MMPs family, mainly involved in the degradation of collagen IV in cell basement membrane. Collagens are the major structural proteins of extracellular matrix, overexpression of which is closely associated with fibrosis disease. Due to the characteristics of recurrence and disability, prevention of intestinal fibrosis has been an emphasis on clinical research.Objective: To explore the clinical correlation between insulin-like growth factor-1 and CD by determining plasma IGF-1 level in CD patients and provide theoretical basis for prevention of intestinal fibrosis.Methods: Applying the Montreal Classification to a cohort of Crohn’s disease patients, ELISA assay was used to measure the levels of IGF-1 and matrix metalloproteinase-2, 9(MMP-2, 9) in 70 CD patients and 10 healthy controls.Results: Compared with healthy controls, the plasma level of IGF-1 in CD patients wasdecreased significantly(5.76μg/L±3.22μg/L vs. 8.82μg/L±3.35μg/L, P<0.01);the levels of MMP-2, MMP-9 and collagen I were increased significantly, all with statistical significance(6.34μg/L±1.39μg/L vs. 2.99μg/L±1.23μg/L; 6.94μg/L±2.05μg/L vs. 4.14μg/L±1.43μg/L; 4.22μg/L±2.61μg/L vs. 2.29μg/L±1.41μg/L, respectively; P<0.05); the level of collagen III was increase non-significantly( 14.55μg/L±5.48μg/L vs. 13.80μg/L±3.40μg/L, P>0.05). According to the biological behavior, the level of plasma IGF-1 was further decreased in stricturing CD than non-stricturing, non-penetrating and penetrating behavior, but with no statistical significance(5.31±2.24μg/L vs. 5.72±3.38μg/L; 5.31±2.24μg/L vs. 5.52±2.33μg/L, respectively; P>0.05). Compared with stricturing CD, the level of MMP-2 increased in penetrating CD significantly(8.26μg/L±0.94μg/L vs. 5.63μg/L±0.91μg/L, P<0.01). According to the disease location, the level of MMP-9 increased in ileum than in colon and ileocolon, with statistical significance( 7.56μg/L±2.23μg/L vs. 5.00μg/L±0.76μg/L; 7.56μg/L±2.23μg/L vs. 6.46μg/L±0.91μg/L, respectively; P<0.01)。Conclusion: The plasma IGF-1 level of CD patients significantly decreased than healthy controls, which further decreased in stricturing CD and associated with its specific biological behavior. IGF-1 may be involved in the pathogenesis of intestinal fibrosis in CD.Part 2 Experimental research on determining the level of insulin-like factor-1 in rats induced by TNBSBackground:Crohn’s disease(CD) is a non-specific granulomatous disease of digestive tract. Etiology and pathogenesis are unclear, with the main clinical manifestation of abdominal pain, diarrhea and intestinal obstruction. Intestinal fibrosis is a chronic clinical course, manifested by progressive narrowing of the intestinal lumen and obstruction eventually. Up to 80% of all patients suffering from CD undergo surgery at least once during the course of their disease because of the complications of intestinal obstruction or fistula. Due to the characteristics of recurrence and disability, prevention of intestinal fibrosis has been an emphasis on clinical research. Insulin-like growth factor-1 is an important growth factor in body, and previous researches showed that IGF-1 is closely associated with organ fibrosis. Matrix metalloproteinase-2, 9 are members of matrix metalloproteinases family, which degrade the extracellular matrix and avoid excessive collagen deposition and fibrosis. Collagens are the major components of extracellular matrix, and type I and type III collagen are the main collagens in the intestine, excessive expression will cause the thickening of bowel wall, scarring and luminal stricture.Objective: To explore the level variation of IGF-1 in the rats with TNBS/ethanol-induced colitis model during the intestinal fibrosis and provide theoretical basis for prevention of intestinal fibrosis.Methods: 1. CD model was established in rats with intracolonic administration of 2, 4, 6-trinitrobenzene sulphonic acid(TNBS). Rats in the control group were given an enema of the same volume of normal saline instead of TNBS. 2. Sixteen healthy male SD rats were randomly divided into 2 groups(n=8): normal control group, model group. 3. Colitis and intestinal inflammation scores in rats included disease activity index(DAI), colonic mucosal damage index(CDMI), histopathological index(HI), fibrosisscoring and myeloperoxidase(MPO) detection. 4. The levels of IGF-1, MMP-2, MMP-9, collagen I and collagen III were determined by enzyme-linked immunosorbent assay(ELISA), using immunohistochemical method to detect the expression of IGF-1 in intestinal mucosa of rats with colitis.Results: Compared with the normal group, TNBS-induced colitis rats all manifested severe weight loss associated with abnormal stools, diarrhea, and hematochezia. DAI, CMDI, HI, fibrosis score, MPO activity and the levels of IGF-1, MMP-2, MMP-9, collagen I and collagen III in colon tissues increased significantly(P <0.01), and expression of IGF-1 in intestinal mucosa increased.Conclusion: Intestinal mucosal inflammation and fibrosis occurred in rats induced by TNBS, the underlying mechanisms were that the inflammation of the colonic mucosa injury caused by the MMP-2, MMP-9, suggesting that IGF-1 was involved in the process of intestinal fibrosis.