LENS EPITHELIAL-CELL APOPTOSIS APPEARS TO BE A COMMON CELLULAR BASIS FOR NON-CONGENITAL CATARACT DEVELOPMENT IN HUMANS AND ANIMALS

Cataract is a major ocular disease that causes blindness in many devel oping countries of the world. It is well established that various fact ors such as oxidative stress, UV, and other toxic agents can induce bo th in vivo and in vitro cataract formation. However, a common cellular basis for this induction has not been previously recognized. The pres ent study of lens epithelial cell viability suggests such a general me chanism. When lens epithelial cells from a group of 20 cataract patien ts 12 to 94 years old were analyzed by terminal deoxynucleotidyl trans ferase (TdT) labeling and DNA fragmentation assays, it was found that all of these patients had apoptotic epithelial cells ranging from 4.4 to 41.8%. By contrast, in eight normal human lenses of comparable age, very few apoptotic epithelial cells were observed. We suggest that ca taract patients may have deficient defense systems against factors suc h as oxidative stress and UV at the onset of the disease. Such stress can trigger lens epithelial cell apoptosis that then may initiate cata ract development. To test this hypothesis, it is also demonstrated her e that hydrogen peroxide at concentrations previously found in some ca taract patients induces both lens epithelial cell apoptosis and cortic al opacity. Moreover, the temporal and spatial distribution of induced apoptotic lens epithelial cells precedes development of lens opacific ation. These results suggest that lens epithelial cell apoptosis may b e a common cellular basis for initiation of noncongenital cataract for mation.