Is apoptosis associated with cataract formation in humans?

Purpose. Recently, Li et al. (J. Cell Biol. 130:169-181, 1995) reported that lens epithelial specimens from cataract patients had a high percentage of apoptotic cells (4 to 41%), while non-cataractous, donor lens epithelia had negligible levels of apoptosis. Lens epithelial cells are known to have a low level of proliferation. It is not evident, therefore, how the large number of dying cells reported by Li et al. could be replaced. We examined epithelia from cataract patients and eye bank eyes for evidence of apoptosis. Methods. Capsulorhexis specimens were obtained at surgery and fixed immediately or transferred to the laboratory in CO₂-independent tissue culture medium. Lenses from donor eyes were photographed and epithelial whole mounts prepared. Epithelia were stained by standard histological means or with the Oncor Apoptag kit. Results. Epithelial cells in capsulorhexis specimens typically had round nuclei of uniform size with no evidence of apoptotic nuclear fragments. In the surgical specimens examined to date, few or no nuclei were stained with the Apoptag reagents. Likewise, lens epithelial cells from eye bank eyes typically had normal morphology whether they were overlying cortical opacities or transparent lens fibers. Little evidence of apoptosis was detected in any region of these epithelial whole mounts. We are examining additional specimens and will attempt to determine whether the nuclear damage detected by Li et al. could have occurred in the epithelial cells after cataract surgery. Conclusions. Apoptosis and extensive lens epithelial cell loss do not appear to precede or be associated with age-related cataract formation.