Purpose: To evaluate the role of mitochondrial DNA (mtDNA) following exposure to ionizing irradiation.
Materials and methods: We examined two human osteosarcoma cell lines either lacking mtDNA (143B.rho(0)206; rho0 cells) or having normal mtDNA (143B.TK-; rho+ cells). Cell survival curves were generated by using colony formation and micronucleus assay. The delay in population doubling time after irradiation was evaluated with dye exclusion tests.
Results: No significant difference was seen between rho+ and rho0 cell lines in colony formation assay. In micronucleus assay, rho0 cells showed a significantly lower rate of micronucleus formation. The ratios of binucleated cells with micronuclei were 0.49 for rho+ cells and 0.25 for rho0 cells (p=0.005). In the dye exclusion test, rho0 cells revealed a delay of about 1.6 times in population doubling time compared with the control after 5 Gy of irradiation, similar to the 1.7 times of rho+ cells.
Conclusion: In the human osteosarcoma cell line 143B.TK-, mtDNA does not influence clonogenic survival and delay of population doubling time after irradiation. However, the difference in micronucleus formation shows that mtDNA influences DNA damage after radiation exposure.