Matrix metalloproteinases (MMPs) are a family of at least 20 structurally related, zinc-containing enzymes that have the ability to breakdown connective tissue. MMP-9 is also known as gelatinase B and 92kDa gelatinase. MMP-9, along with MMP-2, belongs to the gelatinase group of MMP�s which have three repeats of a type II fibronectin domain inserted in the catalytic domain. MMP-9 has shown direct and indirect substrate specificity to collagens IV, V, X and XIV, gelatin, elastin, proteoglycans, plasminogen, aggrecan, galectin-3, entactin, fibrillin, fibrin, IL-1beta, amyloid beta peptide and myelin basic protein. 1-15