Phenotypic change and accumulation of smooth muscle cells in strictures in Crohn's disease: relevance to local angiotensin II system.

BACKGROUND: Intestinal stricture lesions in Crohn's disease are characterized as submucosal fibromuscular accumulation. There has been a controversy about whether the fibrogenic cells in stricture lesions in Crohn's disease originate from a smooth muscle cell or a fibroblast lineage. In the present study, we aimed to elucidate: (1) the origin of the fibrogenic cells in stricture lesions; and (2) the roles of the local angiotensin II system, including mast cell chymase, in stricture formation. METHODS: Methanol-Carnoy's-fixed colonic tissues, obtained from the stricture sites of 18 patients with Crohn's disease, were analyzed by immunostaining for vimentin, smooth muscle actin (1A4 and CGA7), angiotensin II type-1 receptor, angiotensin II-converting enzyme, and mast cell tryptase and chymase. As controls, unaffected (normal) portions of 11 colonic tumor specimens were also investigated. RESULTS: Submucosal fibromuscular accumulation was seen in every stricture lesion. The majority of mesenchymal cells accumulated in the stricture lesions were moderately differentiated intestinal smooth muscle cells [vimentin(+), 1A4(+), and CGA7(+)]. Moreover, occasional intestinal smooth muscle cells in the muscular layers, adjacent to the site of the submucosal fibromuscular response, showed distinct positivity for vimentin, indicating phenotypic modulation toward an immature, or dedifferentiated state. These smooth muscle cells accumulated in the stricture lesions were positive for angiotensin II type-1 receptor. Abundant chymase-positive mast cells were distributed in these lesions. CONCLUSIONS: These results suggest that the proliferation and migration of moderately differentiated intestinal smooth muscle cells from the muscular layers are the major pathological mechanisms in stricture formation in Crohn's disease, and the angiotensin II system is involved in this process.

Expression of LYVE-1 in sinusoidal endothelium is reduced in chronically inflamed human livers.

BACKGROUND: LYVE-1, a specific marker of lymphatics, is expressed in hepatic sinusoidal endothelium. A previous study revealed that LYVE-1 expression in sinusoidal endothelium was reduced in cirrhosis. However, it is still obscure how LYVE-1 expression in sinusoidal endothelium was reduced during the disease progression. To elucidate whether there were relationships among LYVE-1 attenuation, sinusoidal capillarization, and disease progression, we performed immunohistochemical investigations based on frozen human livers. METHODS: Frozen liver sections of chronic hepatitis (n = 8), cirrhosis (n = 13), and normal/control liver (n = 10) were examined by immunostaining for lymphatic endothelial markers (LYVE-1 and D2-40) and vascular endothelial markers (CD31 and von Willebrand factor). Computer-aided morphometry was applied to obtain objective data. The diseased liver tissues were also examined ultrastructurally. RESULTS: In controls, sinusoidal endothelium was positive for LYVE-1 and CD31, but negative for D2-40 and von Willebrand factor. In chronic hepatitis and cirrhosis, LYVE-1 expression in sinusoidal endothelium was attenuated, especially in areas adjacent to active inflammatory or fibrotic lesions, while von Willebrand factor was reciprocally expressed in sinusoidal endothelium. The morphometric analyses revealed that LYVE-1 positivity in sinusoidal endothelium was significantly (P < 0.0001) decreased in chronic hepatitis and cirrhosis compared to controls and was negatively correlated (Rs = -0.72, P < 0.0001) to von Willebrand factor positivity. Furthermore, LYVE-1 positivity was negatively correlated to inflammatory grade (Rs = -0.51, P = 0.021) and fibrosis severity (Rs = -0.46, P = 0.038). Sinusoidal endothelium in the diseased livers showing LYVE-1 attenuation had lost fenestrations. CONCLUSIONS: These findings indicated that LYVE-1 attenuation in sinusoidal endothelium was one of the manifestations of capillarization, and was associated with hepatic disease progression.

Expression of perilipin and adipophilin in nonalcoholic fatty liver disease; relevance to oxidative injury and hepatocyte ballooning.

AIMS: Perilipin and adipophilin, PAT family proteins, play important roles in lipid metabolism. Although nonalcoholic fatty liver disease (NAFLD) is initiated by hepatocyte lipidation, little is known about the relationship between these proteins and hepatocellular injury. We investigated the expressions of perilipin and adipophilin and their relation to inflammation, fibrosis, hepatocellular ballooning, and oxidized phosphatidylcholine (oxPC) localization in human NAFLD. METHODS AND RESULTS: Liver biopsies of nonalcoholic steatohepatitis (NASH, n=39) or simple steatosis (n=9) were studied by immunohistochemical techniques using anti-perilipin, anti-adipophilin and anti-oxPC antibodies. The severity of liver damage was histologically assessed by the Brunt system and NAFLD activity score (NAS). Enlarged hepatocytes usually containing Mallory-Denk bodies were defined as ballooned. Perilipin and adipophilin were detected on the rim of lipid droplets in both NASH and simple steatosis. Perilipin was more evident in larger lipid droplets while adipophilin expression was frequent in lipid droplets of ballooned hepatocytes. The frequency of adipophilin-positive ballooned hepatocytes was correlated to inflammation (Rs=0.72, p<0.0001), fibrosis (Rs=0.46, p=0.005), NAS (Rs=0.47, p=0.004) and oxPC-positive ballooned hepatocytes (Rs=0.35, p=0.033). CONCLUSIONS: Expression patterns of perilipin and adipophilin in NASH livers varied with the size of lipid droplets. In partiew or, adipophilin expression in ballooned hepatocytes was closely associated with oxidative damage.

Enhanced expressions of endothelin-converting enzyme and endothelin receptors in human colonic tissues of Crohn's disease.

Endothelin-1, a powerful vasoconstrictor, forms the endothelin system together with endothelin-converting enzyme and endothelin type A and type B receptors. These endothelin system components are considered to participate in inflammatory and wound healing responses. Previous reports have suggested a role for the endothelin-1 in the pathology of Crohn's disease. In the present study, we immunohistochemically investigated the expressions of the endothelin system components in affected human intestinal tissues of Crohn's disease. Eighteen surgical specimens of colonic tissue obtained from patients with Crohn's disease and 12 normal colonic tissues as controls were examined. Frozen tissue sections cut from the samples were subjected to the immunohistochemical single and double staining. The endothelin system components were expressed mainly in the muscular layers and blood vessels. In diseased colonic tissues, inflammatory infiltration and fibrotic tissue reactions with marked smooth muscle cell proliferation were frequently seen, and were closely associated with increased expressions of the endothelin system components. These results strongly suggest that endothelin-converting enzyme and endothelin type A and type B receptors collectively play a role in the inflammatory and fibrogenic processes of Crohn's disease. Especially, submucosal smooth muscle proliferation, a histological hallmark of strictures, may be attributable to the upregulated endothelin system.