Interexperimental and interindividual variations of DNA repair capacities after UV-B and UV-C irradiations of human keratinocytes and fibroblasts.

DNA repair plays a central role in the cellular response to UV. In this work we have studied the response of skin cells (i.e. fibroblasts and keratinocytes) from the same or from different individuals after both ultraviolet-B (UV-B) and ultraviolet-C (UV-C) irradiations using the comet assay to characterize the specific cellular response to UV-induced DNA damage. Cells were irradiated with increasing doses of UV-B or UV-C. To study the UV dose dependency of initial steps of DNA repair, namely recognition and incision at DNA damage level, the comet assay was performed, under alkaline conditions, 60 min after UV irradiation to allow detection of DNA strand breaks. Comparative analysis of tail moment values after UV exposure of cells from the same or from different individuals showed interexperimental and interindividual variations, implying that repeated assays are necessary to characterize the individual DNA repair capacity. With increasing doses of UV in keratinocytes, a plateau was rapidly reached after irradiation, whereas in fibroblasts a linear dose-effect relationship was observed. These interindividual variations associated with cellular specificity in DNA response may be of significance in skin cell and individual susceptibility toward UV-induced carcinogenesis.