Increased presence of eosinophilic granulocytes expressing transforming growth factor-beta(1) in collagenous colitis

Background: Collagenous colitis is a disease characterized by chronic water y diarrhea, and on microscopic examination of colonic tissue, a typical thi ckening of the subepithelial collagen layer is seen. The etiology and patho physiology behind this disease state are largely unknown. Methods: We have used in situ hybridization and immunohistochemistry to study the expression of transforming growth factor (TGF) -beta(1), a growth factor with the cap acity to cause accumulation of collagen in tissues, in collagenous colitis. Colonic pinch biopsy specimens from a total of 34 patients were investigat ed: 17 patients with collagenous colitis and 17 controls. Results: In patie nts with collagenous colitis there was increased expression of the TGF-beta (1) gene compared with controls, as visualized by in situ hybridization. Th e vast majority of the TGF-beta(1)-expressing cells were eosinophils, bath in collagenous colitis and controls, but there were also scattered fibrobla stic and histiocytic stromal cells. Immunohistochemistry showed the presenc e of TGF-beta(1), mainly in eosinophils, in the colonic mucosa. Morphometri c quantification showed 603 +/- 192 eosinophils/mm(2), (mean +/- standard e rror of the mean) in the colonic mucosa of patients with collagenous coliti s compared with 30 +/- 7 eosinophils/mm(2) in the controls. Conclusions: Th e present results suggest that eosinophils expressing TGF-beta(1) may be of pathophysiologic importance in the connective tissue remodeling seen in co llagenous colitis.