Inter-individual and inter-cell type variation in residual DNA damage after in vivo irradiation of human skin.

Purpose: The aim of this study was to compare inter-individual and inter-cell type variation in DNA double-strand break (DSB) repair following in vivo irradiation of human skin.

Materials And Methods: Duplicate 4mm core biopsies of irradiated and unirradiated skin were collected from 35 patients 24h after 4Gy exposure using 6MeV electrons. Residual DSB were quantified by scoring 53BP1 foci in dermal fibroblasts, endothelial cells, superficial keratinocytes and basal epidermal cells.

Results: Coefficients of inter-individual variation for levels of residual foci 24h after in vivo irradiation of skin were 39.9% in dermal fibroblasts, 44.3% in endothelial cells, 32.9% in superficial keratinocytes and 46.4% in basal epidermal cells (p<0.001, ANOVA). In contrast, the coefficient of inter-cell type variation for residual foci levels was only 11.3% in human skin between the different epidermal and dermal cells (p=0.034, ANOVA). Foci levels between the different skin cell types were correlated (Pearson's R=0.855-0.955, p<0.001).

Conclusions: Patient-specific factors appear to be more important than cell type-specific factors in determining residual foci levels following in vivo irradiation of human skin.