Determination of the radiation sensitivity of the stromal cells in the murine long-term bone marrow culture by measuring the induction and rejoining of interphase chromosome breaks

Abstract

Purpose : To determine the radiosensitivity of bone marrow stromal cells, the rate of interphase chromosome breakage and rejoining of stromal cells in the murine long term bone marrow culture and of human skin fibroblasts were compared. Methods and Materials : The cells were irradiated with doses up to 6 Gy and repair times up to 6 hr were investigated. After induction of premature chromosome condensation by fusing the cells with mitotic HeLa cells, the number of interphase chromosome fragments was counted. Results : The number of radiation induced breaks was found to be not significantly different for both cell types with 6.16 ± 0.26 breaks per Gray for the fibroblasts and 5.96 ± 0.20 breaks per Gray for the stromal cells. A significant difference was observed in the repair rate. The fibroblasts rejoined 39.6% of the breaks induced initially during the first hour after irradiation and 5.6 ± 1.84 breaks remained unrejoined after 6 hr, while the stromal cells were able to rejoin 63.2% in 1 hr and had 2.05 ± 0.07 breaks unrejoined after 6 hr. Conclusion : If the well substantiated assumption is made, that the capacity to repair DNA double strand breaks or interphase chromosome breaks is correlated with the cellular radiosensitivity, this findings indicate, that murine bone marrow stromal cells are more radioresistant than human skin fibroblasts.