Age-dependent changes in spontaneous frequency of micronucleated erythrocytes in bone marrow and DNA damage in peripheral blood of Swiss mice.

Age-dependent changes in chromosomal damage in bone marrow - a self-proliferating tissue - in the form of spontaneously occurring micronucleated erythrocytes, and DNA damage in peripheral blood were examined in male and female Swiss mice. In the erythrocyte population in the bone marrow, polychromatic (immature) erythrocytes showed a significant increase in the frequency of micronuclei as a function of age of the mice (1-20 months). The increase in micronucleus frequency was less in normochromatic (mature) erythrocytes. The female mice showed a higher frequency of micronuclei than the male mice in all the age groups examined. However, the female to male ratio of micronucleus frequencies in total erythrocytes as well as in polychromatic erythrocytes decreased with age. DNA damage, measured as tail moment in the single-cell gel electrophoresis in peripheral blood of different age groups of mice (1, 6, 12 and 18 months) showed a gradual increase with age. Female mice showed more DNA damage than 1-month and 18-month-old male mice. In conclusion, these results show that there is an accumulation of genetic damage in bone marrow and DNA damage in peripheral blood of mice during ageing, and that females show more alterations than males.