Retinal Dysfunction and Progressive Retinal Cell Death in SOD1-Deficient Mice

The superoxide dismutase (SOD) family is a major antioxidant system, and deficiency of Cu,Zn-superoxide dismutase (SOD1) in mice leads to many different phenotypes that resemble accelerated aging. The purpose of this study was to examine the morphology and physiology of the sensory retina in Sod1−/− mice. The amplitudes of the a- and b-waves of electroretinograms elicited by stimuli of different intensity were reduced in senescent Sod1−/− mice, and this reduction in amplitude was more pronounced with increasing age. Retinal morphometric analyses showed a reduced number of nuclei in both the inner nuclear cell layer and outer nuclear cell layer. Electron microscopy revealed swollen cells and degenerated mitochondria in the inner nuclear cell and outer nuclear cell layer of senescent Sod1−/− mice indicating necrotic cell death. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling revealed no significant differences in the number of apoptotic cells between Sod1−/− and wild-type mice, and activated caspase-3 could not be detected in the retina of Sod1−/− mice. In addition to the age-related macular degeneration-like phenotypes previously reported, Sod1−/− mice also present progressive retinal degeneration. Our results indicate that Sod1−/− mice may be a good model system in which to study the mechanism of reactive oxygen species-mediated retinal degeneration.