Increased distribution of collagen type III and reduced expression of matrix metalloproteinase 1 in patients with diverticular disease.

Diverticular disease is an increasingly common clinical problem especially in Western industrialized countries, but the mechanism by which the disease develops remains unclear. Based on studies showing a structural change in the colonic wall in these patients, we examined whether there are any disorders concerning the collagen metabolism in patients with diverticular disease. Samples of colonic tissue from 13 patients with diverticulitis were compared to 14 controls. We performed a Sirius red test for the overall collagen content and immunohistochemical studies facing differentiation between collagen type I and type III and the expression of matrix metalloproteinases 1 and 13. In the bowel sections of patients with diverticulitis there were decreased levels of mature collagen type I (1.37+/- 0.32 vs. 1.59 +/- 0.31) and increased levels of collagen type III (1.61+/- 0.32 vs. 1.42 +/- 0.42), with a resulting lower collagen ratio I/III. The expression of MMP-I was reduced significantly in the diverticulitis group (4.83 +/- 0.92 vs. 6.02 +/- 1.98) while expression of MMP-13 did not differ significantly between the two groups (1.03 +/- 0.11 vs. 1.04 +/- 0.12). Our findings support the theory of structural changes in the colonic wall as one of the major pathogenic factors in the development of diverticular disease. Further studies must focus on the complex interactions of several extracellular matrix components.