间充质干细胞对小鼠辐射早期造血组织细胞的细胞周期及凋亡的影响

本研究探讨骨髓间充质干细胞(MSC)对急性放射病小鼠重要造血免疫器官的早期辐射防护作用及其机制。BALB/c小鼠受5.5Gy60Coγ射线照射后随机分为两组。MSC组照射后1小时内,经尾静脉输注BALB/c小鼠的MSC2.5×107/kg;对照组在照射后输注等体积生理盐水。用流式细胞术检测两组小鼠照射后6、12、24和72小时的骨髓、胸腺和脾细胞的凋亡及细胞周期变化;用免疫组织化学法检测照射后12小时胸腺和脾脏P53蛋白表达情况。结果显示:照射后6小时各器官细胞出现G0/G1及G2/M期阻滞,S期下降。胸腺细胞,脾细胞和骨髓细胞分别于照射后12、6和24小时后发现G0/G1期阻滞峰值,随后G0/G1期细胞减少,S和G2/M期细胞增多,72小时时G0/G1期细胞数低于正常值,S期细胞数高于正常值。胸腺和脾细胞周期改变快于骨髓细胞,改变幅度也大于骨髓细胞。MSC组细胞周期变化速度和程度高于对照组。流式细胞术显示各器官细胞照射后6小时凋亡率明显增加,12小时达高峰,24小时后逐渐降到正常,脾与胸腺细胞凋亡率高于骨髓细胞。MSC组的胸腺细胞照射后12小时、脾细胞照射后12、24小时、骨髓细胞照射后24小时的凋亡率均少于对照组。免疫组织化学检测显示,照射后12小时MSC组小鼠脾脏胸腺细胞P53蛋白表达低于对照组。结论:MSC加快辐射小鼠骨髓、胸腺和脾脏细胞的周期变化,减少细胞凋亡,促进受损的造血和免疫器官修复,从而对受照小鼠起到早期辐射保护作用。

Effects of Mesenchymal Stem Cells on Cell Cycle and Apoptosis of Hematopoietic Tissue Cells in Irrdiated Mice

The aim of this study was to investigate the effect of mesenchymal stem cells (MSCs) on cell cycle and apoptosis of thymus, spleen and bone marrow cells in mice totally irradiated with sublethal dose, and to explore its mechanisms. BALB/c mice irradiated with 5.5 Gy 60Co gamma-ray were randomly divided into control group and MSC group. Mice in MSC group were infused with 0.4 ml containing 2.5x10(7)/kg of MSCs through tail vein at 1 hour after irradiation. Mice in control group were infused with 0.4 ml normal saline. The cell apoptosis and cell cycle of thymus, spleen and bone marrow cells were detected by flow cytometry at 6, 12, 24 and 72 hours after irradiation and the P53 protein expressions in thymus and bone marrow cells were assayed by immunohistochemistry at 12 hours after irradiation. The results showed that the arrest of cells in G0/G1 and G2/M phase, and decrease of cells in S phase appeared at 6 hours after irradiation, those reached peak respectively at 12 hours in thymus cells, 6 hours in spleen and 24 hours in bone marrow, then the cell counts in G0/G1 phase decreased and the cell counts in S and G2/M phases increased. At 72 hours the cell counts in G0/G1 phase were less than the normal level and the cell counts in S phase were more than the normal level. The above changes of cell cycle in thymus and spleen were more rapid in spleen and more obvious in amplitude than that in bone marrow, the change of cell cycle in MSC group was more rapid and obvious than those in control group. After irradiation the apoptosis cells increased from 6 hours, reached the highest level at 12 hours and decreased to the normal level gradually after 24 hours in two groups; the apoptosis rates in spleen and thymus cells were higher than that in bone marrow cells. In comparison with the control group, the apoptosis rate in thymus cells at 12 hours, in spleen cells at 12 and 24 hours, and in bone marrow cells at 24 hours were fewer in MSC group. The cells expressing P53 protein in control group were more than that in MSC group. It is concluded that the MSCs accelerate the running of cell cycle in these hematopoietic tissue cells of irradiated mice, reduce the cell apoptosis and promote the recovery from injuries in hematopietic and immunological organs, thus protect the irradiated mice at early stage.