Expression and Regulation of Tissue Inhibitor of Metalloproteinase-1 and Matrix Metalloproteinases by Intestinal Myofibroblasts in Inflammatory Bowel Disease

Intestinal fibrosis and strictures frequently occur in Crohn's disease but not ulcerative colitis. We have recently shown that, compared to myofibroblasts obtained from normal and ulcerative colitis tissue, myofibroblasts isolated from fibrotic Crohn's disease mucosal samples express significantly lower amounts of transforming growth factor (TGF)-β3, but the expression of TGF-β2 was significantly greater. We now report that in myofibroblast cultures established from fibrotic Crohn's disease mucosal samples there is significantly higher constitutive expression of tissue inhibitor of metalloproteinase (TIMP)-1 compared to similar cells isolated from normal or ulcerative colitis tissue. Myofibroblasts derived from normal mucosa and from mucosa affected by ulcerative colitis or Crohn's disease also expressed matrix metalloproteinase (MMP)-1, MMP-2, and MMP-3 but did not express MMP-9. Recombinant (r) TGF-β1 and rTGF-β2, but not rTGF-β3, induced expression of TIMP-1 in normal intestinal myofibroblasts. These studies illustrate a potential mechanism by which differential expression of isoforms of TGF-β may lead to excessive deposition of extracellular matrix and stricture formation via TIMP-1-mediated inhibition of MMP activity.