CHARACTERIZATION OF THE MAJOR MATRIX DEGRADING METALLOPROTEINASE OF HUMAN CORNEAL STROMA - EVIDENCE FOR AN ENZYME-INHIBITOR COMPLEX

The human cornea is an avascular, highly organized tissue with the unique property of transparency. While the extracellular matrices of this tissue are composed of a variety of collagen types, proteoglycans and glycoproteins, little is known of the normal degradation and remodeling of these components. We examined the capacity of organ cultured human ocular tissues to produce and secrete metalloproteinases, a family of related enzymes capable of digesting a variety of extracellular matrices. We demonstrated that while enzymatic activities similar to type I collagenase and stromelysin are produced, the predominant activities of the corneal stroma and keratocyte cultures are a 68-kDa gelatinase. In our hands, this enzyme does not appear to be induced significantly by phorbol esters in vitro. In addition, this enzyme appears to be secreted as a complex with a 21-kDa protein that functions as an enzymatic inhibitor. Moreover, the keratocytes also produce a 28-kDa inhibitor which has similar properties to tissue inhibitor of metalloproteinase (TIMP). © 1991.