EXTRACELLULAR-MATRIX COMPOSITION AND GENE-EXPRESSION IN COLLAGENOUS COLITIS

Background & Aims: Collagenous colitis is a rare diarrheal disease of unknown pathophysiology that is histologically defined by subepithelia l bandlike structures. The objective of this study was to elucidate th e biochemical composition and the origin of the bandlike structures in collagenous colitis. Methods: Immunohistochemical and in situ hybridi zation analyses were performed on endoscopic specimens using specific antibodies and riboprobes for collagen types I, III, IV, and VI and fo r the glycoprotein tenascin. Results: in collagenous colitis, the muco sal matrix with the exception of the bands retained a normal architect ure and extracellular matrix composition. The bands stained most promi nently for type VI collagen and tenascin. Less abundant staining for b oth proteins was also found in the subepithelial matrix of the normal mucosa. In situ hybridization showed no significant increase in collag en type VI messenger RNA expression in cells around and entrapped in t he bands in collagenous colitis compared with normal specimens. Conclu sions: The results support the suggestion that collagenous colitis is a localized alteration of the extracellular matrix, which involves the pericryptal-subepithelial myofibroblast sheath. The data suggest that reduced matrix degradation and not overactivation of matrix synthesis may be the reason for the subepithelial accumulation of matrix protei ns.