Very little is currently known regarding the underlying mechanisms involved in the etiology of intestinal strictures in chronic inflammatory bowel disease. The deposition of extracellular matrix components, especially collagens, is thought to play an important role in the etiology of intestinal strictures. The main goal of this study was therefore to investigate the collagen metabolism in patients with inflammatory bowel disease using the in situ hybridization technique. We determined de novo synthesis of the (pro)-collagen mRNA transcripts alpha 1I, alpha 1III, alpha 1IV, alpha 2V as well as the collagen degrading enzyme mRNA transcripts collagenase type I and IV in Crohn's disease and ulcerative colitis and compared the rate of expression semiquantitatively to healthy controls. We found a significant increase of all (pro)-collagen transcripts tested in Crohn's disease and ulcerative colitis as compared to healthy control tissues, indicating an increased de novo synthesis of all collagens in both inflammatory bowel diseases. However, we observed a significant difference in the expression of the collagenase mRNA transcripts between Crohn's disease and ulcerative colitis. Compared to healthy control subjects we were unable to detect a significant difference in the expression of collagenase type I and IV in Crohn's disease; in contrast, we observed a significant increase in the rate of expression for the collagenases in ulcerative colitis as compared to controls or biopsies from patients with Crohn's disease.(ABSTRACT TRUNCATED AT 250 WORDS)