Objective: To investigate the mechanism of radiation induced premature senescence of bone marrow stromal cells induced by gamma-radiation.
Methods: Bone marrow stromal cells were isolated from the bones of mice, cultured, and divided into 2 groups: control group and irradiation group. The cells of the irradiation group were exposed to 60Co gamma-rays of the dose of 8.0 Gy. 24 h, 72 h, 1 week, and 2 weeks after irradiation MTT method was used to test the proliferation of the cells, Giemsa staining was used to observe the morphology, the percentage of cells positive in beta-galactosidase (SA-beta-Gal), a senescence associated biomarker, was detected by cytochemistry, and RT-PCR was used to detect the mRNA expression of p21(Cip1/Waf1) and p53 gene, both associated with senescence. One week after the irradiation flow cytometry was used to analyze the cell cycle distribution.
Results: Characteristics of mature senescence were seen in the cells of the irradiation group. One week after the irradiation the percentage of G0/G1 of the irradiation group was 89.83% +/- 0.05%, significantly higher than that of the control group (66.95% +/- 0.36%, P < 0.01). 24 h, 72 h, 1 week, and 2 weeks after irradiation the percentages of SA-beta-gal positive cells in the irradiation group were 20.33% +/- 0.03%, 34.33% +/- 0.03%, 86.33% +/- 0.02%, and 95.67% +/- 0.02% respectively, significantly higher than those of the control group (2.33% +/- 0.006%, 14.33% +/- 0.02%, 24.67% +/- 0.02%, and 45.00% +/- 0.02% respectively, all P < 0.01). The mRNA expression of p53 and p21(Cip1/Waf1) mRNA expressions in the irradiation group increased 24 h after the irradiation and lasted for two weeks.
Conclusion: Gamma-radiation induces changes of premature senescence in bone marrow stromal cells in which p53-p21(Cip1/Waf1) manner pathways may play an important role.