MEASUREMENT OF RADIATION-INDUCED DNA DOUBLE-STRAND BREAKS IN HUMAN-DIPLOID FIBROBLASTS FROM KELOID AND NORMAL SKIN BY SINGLE-CELL GEL-ELECTROPHORESIS

Cell culture experiments recently have shown that different population s of fibroblasts may exist in keloid patients. Moreover, several studi es have strongly suggested heterogeneity in cell response of skin fibr oblasts in the same individual. The purpose of this study was to evalu ate the radiation sensitivity of skin fibroblasts from keloid and norm al skin. Single-cell gel electrophoresis was employed in detecting amo unts of DNA double-strand breaks generated in individual fibroblasts p rimarily cultured from normal skin and from keloid tissue after variou s doses of r-irradiation (0, 25, 50, and 100 Gy aerobically) from a Cs -137 radiation generator. For the repair study, cells were incubated a t 37 degrees C for 0 and 15 minutes and 1 and 2 hours after irradiatio n. Following neutral lysis and electrophoresis, DNA double-strand brea ks were then detected by propidium iodide staining and determined by f luorescence microscope and quantitative image analysis. No significant difference in the extent of DNA double strand breaks in fibroblasts f rom normal skin or keloid after various doses of irradiation was obser ved. However, the residual DNA double-strand breaks remaining after va rious periods of incubation were demonstrated to be significantly incr eased in fibroblasts from keloid (p < 0.01). In conclusion, different repair capacities were found in fibroblasts from normal skin and keloi d scar; this finding may play a role in the treatment of the disease e ntity.