Induction and disappearance of thymine dimers in human skin exposed to UVB radiation: flow cytometric measurements in replicating and nonreplicating epidermal cells

We have earlier reported on determining UV-induced DNA damage in murine epidermal cell suspensions by flow cytometric analysis of the fluorescence from a fluorescein isothiocyanate-labeled antibody (H3) directed against thymine dimers (T<>T). Here we present an optimization of the technique for analysis of epidermal cell suspensions from 4 mm biopsies from human skin. Cells with different DNA contents can easily be distinguished in flow cytometry by the intensity of DNA-specific 7-amino-actinomycin D fluorescence. Genuine G2-M-phase cells can further be distinguished from cell doublets by pulse-shape discrimination. Thus, T<>T levels in individual cells with different DNA contents (i.e. Go-G1, S or G2-M phases) can be determined after in vivo exposure of human skin to environmentally relevant UVB (280-315 nm) doses. (author)