Brain-derived neurotrophic factor transgenic neural stem cells can alleviate toxicity of β-amyloid to cultured neurons

Objective To explore the resistance of neural stem cells (NSCs) in β-amyloid (Aβ) toxicity after being transfected with brain-derived neurotrophic factor (BDNF) and its mechenism. Methods NSCs in the C57 mice were transfected with BDNF gene by using lipofectamine technique; the BDNF gene expression in transfected NSCs and their differentiated cells were detected by immune-fluorescent staining and ELISA. Rat neurons were cultured in vitro and divided into 3 groups: neurons group, neurons co-cultured with NSCs group, neurons co-cultured with BDNF transfected NSCs group; two-parallel group design was adopted. Three d after the group culturing, cells from each parallel group were added Aβ40 protein. Neuron survival of each group was recorded 24 and 48 h after adding Aβ40 by ELISA. The Aβ, tau, and phosphorylating tau (ptau) levels were detected by Western blotting. Results BDNF-transfected NSCs could continuously express BDNF gene products during the first 1.5 weeks. Both transfected NSCs and their progenies expressed BDNF gene products. Using neurons group as reference, the mean survival rates of neurons plus Aβ40 group, neurons co-cultured with NSCs plus Aβ40 group, neurons co-cultured with BDNF transfected NSCs plus Aβ40 group were 51.86%±0.03%, 73.68%±0.04% and 85.34%±0.01% at 24 h after adding Aβ40, and 38.76%±0.01%, 59.65%±0.04%, 75.61%±0.07% at 48 h after adding Aβ40; the survival rate in the neurons plus Aβ40 group and neurons co-cultured with NSCs plus Aβ40 group was significantly lower than the other groups (P 0.05). The tau protein level showed no significant differences between each two groups (P>0.05), while the p-tau protein level was significantly different (that in the neurons co-cultured with NSCs plus Aβ40 group and neurons co-cultured with BDNF transfected NSCs plus Aβ40 group was significantly higher than that in the other groups, P<0.05). Conclusion BDNF-transfected NSCs express BDNF gene products during the early time, which alleviate the toxicity of Aβ to NSCs and reduce the p-tau protein level, leading to increased survival rate of neurons. Key words: Beta-amyloid; Tau; Brain-derived neurotrophic factor; Neural stem cell