Morphological changes in astrocytes of aging mice fed normal or caloric restricted diets

Abstract

Astrocyte hypertrophy, associated with neuronal degeneration, has been reported in aging rat hippocampus. Dietary restriction throughout life (restriction of calories without decrease in essential nutrients) increases average and maximal lifespans in rodents. In the present study, the effect of caloric restriction on age-related changes in the maximal diameters of mouse astrocytes was measured. Specific pathogen free C57BL6 mice maintained on either ad libitum (NIH 31 rodent diet) or restricted (60% ad libitum with vitamin supplementation) diets, ages 0.6 (weaning), 6, 19, and 24 months were obtained from the NCTR aging rodent facility in Jefferson, AK. Their brains were stained by a modified Golgi method and astrocyte diameters were determined with a Zeiss Videoplan image analyzer. Astrocytes in the hippocampus and dentate gyrus of ad libitum-fed mice were of similar diameter from 6 to 24 months of age, and were larger than those of weanlings. However, astrocytes were significantly smaller in the hippocampus and dentate gyrus of caloric restricted mice at 19 and 24 months, suggesting the prevention or reversal of age-related astroglial enlargement. Astroglia were also significantly smaller in the frontal and parietal cortices of caloric-restricted mice at six months of age than those of ad libitum-fed mice. At older ages, however, no significant differences were seen between the two groups. This finding may indicate a delay in neocortical astrocyte development by caloric restriction.