Figure 4
Neurospheres formed in 1%O2 presented different growth styles under different oxygen levels. (A) U87 CD133+CD15+NESTIN+ neurospheres maintained growth in suspension with a sphere morphology under 1%O2 conditions; under 21%O2, some neurospheres also existed after exposure for 5 d. However, there were no neurospheres after 95%O2 exposure for 5 d. (B) The number of neurospheres increased in a time-dependent manner from hypoxia exposure for 1 to 5 d; compared with 21%O2, the number of neurospheres in 1%O2 was substantially increased, whereas under hyperoxic conditions, few neurospheres were detected (* P < 0.05; ** P < 0.05; # P < 0.05, One-sample T Test, One-way ANOVA). (C) There were no differences among the different oxygen levels on day 2 for the cell number of U87 CD133+CD15+NESTIN+ neurospheres. After three days, the number of cells under 95%O2 gradually decreased. In contrast, the cell numbers in 1%O2 and 21%O2 increased in a time-dependent manner, and the cell proliferation rate of cells in 1%O2 was faster than that of cells in 21%O2 (* P < 0.05; # P > 0.05, One-sample T Test, One-way ANOVA). (D–F) Hypoxia promoted the expression levels of CD133, CD15, NESTIN, ABCG2 and MGMT and inhibited GFAP for U87 CD133+CD15+NESTIN+ stem cells. In contrast, hyperoxia presented the opposite effects, which resulted in decreases of CD133, CD15, NESTIN, ABCG2 and MGMT and an increase of GFAP (* P < 0.05, Paired-samples T Test).
