Insulin growth factor 1 (IGF-1) suppressed cell apoptosis induced by hypoxia in neural stem cells (NSCs). NSCs were divided into four groups: the Control, Hypoxia, Hypoxia+IGF-1, and Hypoxia+IGF-1+PPP groups. (A, B) NSCs were double stained by Annexin V-FITC and propidium iodide (PI), and then apoptotic cells were analyzed by flow cytometry. (C) The protein expression levels of apoptosis-associated factors were assayed by Western blot analysis. (D) The band intensity was assessed by Image Lab™ Software. The expression levels were all normalized by GAPDH. The expression level of activated caspase-3 was expressed as the relative intensity of cleaved/pro caspase-3. Data presented are the mean ±SD of three independent experiments. ** P<0.01; *** P<0.001. The significance marked at the top of the columns refers to comparison with the control group.