Normal mouse and rat strains as models for age-related cataract and the effect of caloric restriction on its development.

The purpose of this study was to determine: (1) which of the commonly used strains of laboratory rats and mice provide good models for human age-related cataract, and (2) whether long term caloric restriction, a regimen that prolongs both median and maximum life span in rodents, would also delay the time of appearance of this age-related pathology. Three strains of mice and two rat strains commonly used in laboratory work and maintained on either ad libitum (AL) or calorically restricted (CR) diets in the National Institutes of Aging and Diet Restriction colony were examined by slit lamp for age-related cataracts at four or more time points during their life spans. These strains were Brown Norway and Fischer 344 rats, and C57BL/6, (C57BL6 x DBA/2)F1 and (C57BL/6 x C3H)F1 mice. None of these strains develop congenital cataracts. Various stages of cataract were found in the great majority of these animals in old age. In both rat strains and one mouse strain the cataracts occurred after mid-life, were most advanced late in life, and were similar in locations and appearance to those in humans. In the two mouse strains in which some cataracts appeared as early as 10-14 months of age, previously identified genetic defects affecting the eye were probably involved in the early appearances. CR extended life spain in all five rat and mouse strains and also delayed both the time of first appearances and the subsequent increase in cataract severity over time in the four dark-eyed strains. CR did not delay cataract formation in the single albino rat strain studied. In summation: (1) commonly used strains of laboratory rats and mice that are free of congenital or early appearing cataracts due to genetic defects would appear to serve as appropriate models for human age-related cataract, (2) caloric restriction (CR) provides a protective effect, delaying development of cataracts in the dark-eyed mouse and rat strains, while also extending their life spans, (3) CR did not delay the development of lens damage in the nonpigmented eye of the single albino strain studied, although it extended life span.