[Effect of G-CSF on murine thymocyte emigration and cell cycle alteration after a sublethal dose of irradiation]

This study was aimed to investigate the effect of recombinant human granulocyte colony-stimulating factor(G-CSF) on murine thymocyte emigration and cell cycle alteration after a sublethal dose of gamma-irradiation. Female BALB/c mice were given 6.0 Gy γ-ray total body irradiation and then randomly divided into G-CSF and control groups. Mice in the G-CSF group were injected recombinant human G-CSF 100 µg/(kg·d) subcutaneously once daily for 14 consecutive days and mice in the control group were given the same volume of phosphate buffered solution. Thymocyte cycle alteration and the proportion of apoptosis cells were detected by flow cytometry within 72 hours after irradiation. Real-time PCR was used for detection and quantitation of murine T cell receptor rearrangement excision circles (sjTREC) of the thymic cells at 30 and 60 day after the irradiation. The results showed that at 6 hour after irradiation G-CSF could significantly increase the thymic cells in G(0)/G(1) phase, G-CSF vs control: (82.0 ± 5.0)% vs (75.9 ± 2.8)% (p < 0.05), and decrease the thymic cells in S phase, G-CSF vs control: (10.2 ± 4.8)% vs (15.7 ± 2.3)% (p < 0.05), but G-CSF seemed have no evident effects on the percentage of thymic cells in G(2)/M phase. G-CSF could also protect thymocytes from apoptosis at 6 hour and 12 hour after irradiation the percentages of apoptosis cells in G-CSF group were (11.5 ± 2.4)% and (15.5 ± 3.3)%, respectively, which were significantly lower than that of the control group (16.5 ± 2.2)% and (22.6 ± 0.7)%, respectively (p < 0.05). The sjTREC copy amount was conspicuously higher in G-CSF group than that in the control at 30 day after irradiation (p < 0.01), but the preponderance disappeared 60 days later. It is concluded that G-CSF has a positive effect on the thymic cell cycle alteration to protect thymocytes from apoptosis and enhance the recent thymocyte emigration, which may contribute to the central immune reconstitution after irradiation.