Matrix metalloproteinases as mediators of primary and secondary cataracts

The matrix metalloproteinases (MMPs) are a family of endopeptidases involved in numerous remodeling and fibrotic disorders. Although MMPs have been shown to play important roles in regenerative and disease processes in many parts of the eye, including the cornea, retina and trabecular meshwork, the role of MMPs in the normal and cataractous lens has only recently been studied. These investigations have shown that multiple MMPs are expressed in the lens and their expression is altered in a number of cataract phenotypes. However, anterior subcapsular cataract and posterior capsular opacification, cataracts of a fibrotic nature, show a particular involvement of MMPs. This review will highlight recent findings that suggest a causative role for MMPs in these fibrotic cataract phenotypes.