Objective: To observe the effects of basic fibroblast growth factor (bFGF) on neuronal apoptosis and caspase 3 gene expression after spinal cord injury.
Methods: Forty-five SD rats were randomly divided into 3 equal groups: normal group (n = 5, with the spinal cord intact), treatment group [n = 20, with their spinal cord at T13-L2 injured by distraction till the cortical somatosensory evoked potential (CSEP) decreased by 70% and then a thin plastic tube inserted into the subarachnoid cavity below the injured level for perfusion of bFGF 20 microg immediately, and 1, 2, 3, 4, 8, 12, and 24 hours after injury], and control group (n = 20, with their spinal cord at T13-L2 injured by distraction till the CSEP decreased by 70% and then a thin plastic tube inserted into the subarachnoid cavity below the injured level for perfusion of normal saline of the same volume at the same time points). CSEP was tested by electrophysiological technique to record the latent time of P1 wave and the amplitude of P1-N1. Combined behavioral score (CBS) was used to evaluate the function of spinal cord, including motivation, sensation, reflex, and coordination of actions. The rats were killed at the days 1, 4, 7, 14, and 21 postoperatively. A segment of spinal cord T13-L2 1.5 cm long was taken out to be fixed and sliced. Flow cytometry was used to detect the neuronal cell apoptosis. Imunohistochemistry and TUNEL were used to examine the expression of caspase 3.
Results: The CBS value of the normal group was 0, and the CBS values at different time points of the treatment group were all lower than those of the control group (P < 0.05 or P < 0.05). The values of latent time of P1 wave 4 approximately 21 days after injury of the 2 injury groups were all longer than that of the normal group, those of the treatment group being significantly shorter than those of the control group. The values of P1-N1 amplitude 4 approximately 21 days after injury of the 2 injury groups were all lower than that of the normal group, those of the treatment group being significantly lower than those of the control group (P < 0.05 or P < 0.01). TUNEL showed that the apoptotic cell numbers at different time points of the 2 injury groups were lower than that of the normal group, those of the treatment group being significantly lower than those of the control group (P < 0.05 or P < 0.01). Immunohistochemistry showed that the numbers of caspase 3 positive cells at different time points of the 2 injury groups were all lower than that of the normal group, those of the treatment group being significantly lower than those of the control group (P < 0.05 or P < 0.01). The active fluorescence values at different time points of the 2 injury groups were all higher than those of the normal group, those of the treatment group being significantly lower than those of the control group (P < 0.05 or P < 0.01).
Conclusion: bFGF inhibits the expression of caspase 3 protein, reduces the caspase 3 activity, lessens the secondary cell apoptosis in the injured spinal cord, and promotes nerve function recovery of spinal cord.