Five mouse models with known alterations of resistance to oxidative damage were compared by
slit lamp examination for the presence and degree of advancement of age-related
cataract in young adult and old animals along with wild type controls. A group of young and old normal C57BL/6Jax mice were examined first to constitute a standard, and they were found to exhibit age-related
cataract development. Following this, four models on the C57BL/6 background with imposed genetic alterations affecting
anti-oxidant enzyme presence or activity, and one outbred model in which a deletion blocked the
growth hormone/IGF-1 axis, were similarly examined. There was no evidence of foetal or juvenile
cataract development in any of these models, and an age-related severity for
lens opacities was shown between young adult and old mice in all groups. Model 1, mice null for the
anti-oxidant gene
glutathione peroxidase-1 (GPX1) had significantly advanced
cataracts in older mice vs. same age controls. In mouse model 2 hemizygous knockout of SOD2 (MnSOD) did not affect age-related
cataract development. In model 3 combining the GPX1 and SOD2 deficiencies in the same animal did not advance
cataract development beyond that of the GPX1 null alone. In model 4 the addition of
anti-oxidant protection in the lens by transfection of human
catalase targeted only to the mitochondria resulted in a significant delay in
cataract development. The 5th model,
growth hormone receptor knockout (GHR-/-) mice, also demonstrated a significant reduction in age-related
cataract development, as well as
dwarfism. These findings, in general, support the oxidative theory of age-related
cataract development. The exception, the partial deletion of SOD2 in the hemizygous KO model, probably did not represent a sufficiently severe deprivation of
anti-oxidant protection to produce pathologic changes in the lens.