Influence of mitochondrial DNA upon cellular radiosensitivity

Objective To assess the effect of mitochondrial DNA (mtDNA) on radiosensitivity in vitro. Methods Three human fibroblast cell lines with deficient mtDNA (ρ 0 cell), mutanted mtDNA (syn - cell) and normal mtDNA (ρ + cell) were exposed to 137 Cs gamma ray. Cologenic formation assay was used for cell survival curves. Cell cycle distribution and apoptosis were analyzed by flow cytometry. Results The ρ 0 cell line showed a stronger resistance to radiation as compared to the other two cell lines by colony formation assay (P=0.022). A marked shoulder in the cell survival curve was observed in the ρ 0 cell at low dose irradiation. The lower percentage of radiation-induced apoptosis was observed in ρ 0 cells after 2, 5, and 8 Gy, as compared to those in syn - cell and ρ + cells (P= 0.017). No difference in cell cycle distribution was observed in three cell lines. Conclusion Our results suggest that mtDNA play an important role in the radiation sensitivity in human fibroblast cells.