Role of the extracellular matrix in the degradation of connective tissue.

Cell-matrix interactions have an important impact on regulating connective tissue degradation during physiological and pathological processes, e.g., development, wound healing and tissue remodeling and tumor invasion and metastasis. Connective tissue breakdown is initiated by a specific class of enzymes, the matrix metalloproteinases, which include the type I collagenases, the type IV collagenases/gelatinases and the stromelysins and which vary with respect to their substrate specificities. The activity of the metalloproteinases is regulated by de novo synthesis of the proenzymes, the activation of the zymogens and by the presence of the inhibitors, TIMPs. This tight control is required in order to guarantee normal functioning of connective tissue.