IN-VITRO RADIATION SENSITIVITY OF MOUSE LUNG FIBROBLASTS ISOLATED BY FLOW-CYTOMETRY

Purpose: Recently, we have isolated two major fibroblast cells (Thy-1(+), Thy-1(-)) from mouse LAF1 lung tissue using the anti-Thy-1 antibody expression and fluorescence activated cell sorter. To examine the possibility that x- or gamma-ray-induced pulmonary fibrosis at the late stage of injury could arise from radioresistant cell subpopulations, the radiation sensitivities of Thy-1(+) and Thy-1(-) cells were evaluated by the colony forming assay. Methods and Materials: Cell survival curves, repair of potentially lethal damage (PLD) and sublethal damage (SLD), and cell-age response curves were obtained after Cs-137 gamma-ray irradiation. Results: The cell survival curves measured after 0-10 Gy gamma-ray showed that Thy-1(+) cells were slightly more radioresistant than Thy-1(-) cells. The D-0, n, alpha, and beta values measured from the survival curves also confirmed this observation. After a single dose of 10 Gy, a small amount of PLD repair was observed in Thy-1(-) cells, while no PLD repair was found in Thy-1(+) cells. Although the initial cell survival level of Thy-1(-) cells was lower, the final survival levels of Thy-1(+) and Thy-1(-) cells became identical at 8 h after irradiation due to the PLD repair. After split-dose irradiation of 4 Gy followed by 4 Gy, a similar extent and rate of SLD repair was found in Thy(1+) and Thy-1(-) cells. Cell-age response curves were obtained from irradiated G(0)/G(1), S, and G(2)M cells separated by centrifugal elutriation and irradiated with 8 Gy gamma-ray. The results indicated that Thy-1(+) and Thy-1(-) cells had a similar S resistant, and G(1), G(2)M-sensitive radiation cell-age response curve. Conclusions: This study suggests that the selection of radioresistant lung fibroblast may not be responsible for the development of lung fibrosis in irradiated LAF(1) mouse.