MMP9 and inflammatory bowel disease: The intestinal stromal cells, including fibroblasts, myofibroblasts, pericytes, endothelial cells, and smooth muscle cells, have been shown in human colonic myofibroblasts and in IBD patients to secrete MMP-2 during the activation of inflammatory processes and after a stimulation by MMP-1, MMP-3 and MMP-9 [21,22,23].