DNA repair response in human epidermal keratinocytes from donors of different age.

We have compared the excision-repair and growth properties of epidermal keratinocytes from humans of different ages. Keratinocytes isolated from newborn and adult abdominal skin at autopsy were cultured on collagen gels. Repair replication was assayed by the 5-bromodeoxyuridine density-labeling method following ultraviolet (UV) irradiation (254 nm) of the cultures. The keratinocytes from newborn donors proliferated more rapidly and attained a higher concentration at confluence than did those from aged donors. Semiconservative DNA replication was inhibited by UV radiation to an equal extent in cell cultures from newborns and adults. After a UV dose of 13 J/m2, the time course of DNA repair was similar for the respective cultures. Furthermore, there were no significant differences in the time course of repair for keratinocytes in the proliferative or the plateau phase of growth. The dose-response curves for repair replication in cells from both young and old donors maximized at about 50 J/m2 but the attenuation in repair at higher doses appeared somewhat greater in cells from older donors. We conclude that no significant age-related differences exist in the rate and extent of the repair-replication response of human epidermal keratinocytes to UV-radiation damage in DNA. However, it remains to be determined whether other cellular recovery responses to damaged DNA are also relatively unrelated to age.