The effects of repetitive magnetic stimulation on differentiation and apoptosis of neural stem cells in vitro

Objective To study any effect of repetitive magnetic stimulation (rMS) on the differentiation and apoptosis of rat neural stem cells in vitro. Methods The bilateral hippocampus of a 3-day old Sprague-Dawley rat was used to culture neural stem cells (NSCs) in vitro. P2 NSCs were differentiated to neurons or astrocytes in differentiation medium and then divided into a control group in which the NSCs differentiated naturally, and an rMS group in which 1000 impulses/day of rMS were applied at 10 Hz once a day for 7 days at 50% of maximum output. One hour after the last stimulation, immunofluorescence was used to analyze the ratio of neurons and astrocytes, and Western blotting was employed to evaluate the expression of glial fibrillary acidic protein (GFAP), β-Ⅲ tubulin and brain-derived neurotrophic factor (BDNF). NSCs which had differentiated for 7 days without stimulation were then selected and divided into an apoptosis group and an apoptosis+ rMS group. The same rMS protocol was applied to the latter group 1h after the apoptosis, and 4h later flow cytometry (anexin V-FITC) was employed to evaluate the apoptosis ratio. Bcl-2, Bax and caspase-3 protein expression were analyzed using Western blotting. Results There were no significant differences between the control and rMS groups in the proportion of NSCs differentiating to neurons or in β-Ⅲ tubulin, GFAP or BDNF protein expression. The cell apoptosis rate of the apoptosis+ rMS group was significant lower than in the apoptosis group. Caspase-3, Bcl-2 and Bax protein expression were also significantly different between the two groups. Conclusion rMS at 10Hz for 7 days has no effect on the differentiation of NSCs, but it has a protective effect on neural cells and decreases the apoptosis rate. Key words: Repetitive magnetic stimulation; Neural stem cells; Apoptosis; Differentiation