Residual skin injury after repeated irradiation: differences observed using healing, macrocolony, and microcolony endpoints.

Abstract

Following three repeated tolerance doses to mouse tail skin, residual injury was characterized by a 35% reduction in the iso-effective dose compared to age-matched controls, using healing or macrocolony endpoints. In contrast, the reduction was only 9%, measured using microcolony formation. The colony data showed that the reduction was a constant dose, not a dose-modifying effect. The residual injury is interpreted as due to a reduced density of microcolony-forming cells in the epidermis, and these are less capable of macrocolony formation and hence of re-epithelialization in the repeatedly-irradiated epidermis.