| Objective To investigate the correlation between the expression level of VEGF and cells apoptosis after acute spinal cord injury as well as recovery of neurological function through observing the effect of defibrase on the expression of vascular endothelial growth factor(VEGF) at different time points after rats suffering acute spinal cord injury and the apoptosis of cells in local spinal cord, and thus to primarily explore the effect of defibrase on spinal cord injury and the underlying the mechanism so as to provide new theoretical foundation for the clinical application of defibrase in the treatment of spinal cord injury.Methods Ninety female SD rats, the weight of which were between 250-300g. Those animals were randomly divided into sham group(sham operation group), spinal cord injury group(control group),spinal cord injury and defibrase interventing group(Intervention group),with 30 animals in each group.The 90 rats were surgically removed the vertebral lamina of T12 segment to expose the spinal cord, and then in sham group, the spinal cord was untouched; in spinal cord injury group, the spinal cord was hit by power of 10g×6cm according to the improved Allen's method to establish rat acute spinal cord injury model. The behavior of each group were respectively observed at 1d,3d,5d,7d,14d,28d after injury and Motor Function Assessment was taken(BBB), then 5 randomly selected rats were sacrificed at each time point, materials were obtained from the injury locations following by HE staining,immunohistochemical staining(IHC) of cell apoptosis and VEGF, observation and calculation of the VEGF positive cells and the positive apoptosis cells under light microscope.The number of VEGF positive cells and apoptosis cells of injured spinal cord tissue were compared at every time point among groups and within groups. Then correlation between VEGF positive cells and apoptosis cells within pure injury group was analyzed. The experimental data was analyzed by SPSS16.0 statistical software.Results The BBB score of sham group was 21, and the score of control group and intervention group at every time point were significantly decreased compared to sham group, while the score of intervention group was higher than control group at all the time points after 3 days(P<0.05),among which the score of the two groups was apparently different at 7,14,28 days time pionts(P<0.01).The result of VEGF IHC: except that a few VEGF expressed around central canal and soft meninges of spinal cord, it seldomly expressed in other locations in sham group; In control group, after spinal cord injury VEGF highly expressed in the injured area and its periphery, which reached the peak at 5d,decreased after 5d,obviously expressed at 7d,14d and still expressed at 28d. While in intervention group, the expression of VEGF significantly increased at 1d,3d,5d,7d,14d, 28d compared to control group, and the difference was significant (P<0.05), among which the expression of VEGF between the two groups were apparently different at 3,5,7,14days time pionts(P<0.01). The result of TUNEL labeled cell apoptosis: a little TUNEL labeled positive cells were observed at every time point in sham group, while those cells could be observed obviously after spinal cord injury in the control and intervention groups.Apoptotic cells gradually increased after injury, reached the peak at 1d, decreased after that. At 5d, 7d time points there were still many apoptotic cells and still existed at 14d, 28d. Those positive cells mainly existed in neurons and astrocytes, the apoptosis positive cell in intervention group was significantly lower at 1d, 3d, 5d, 7d ,14d, 28d when compared to control group, which was significantly different(P <0.05), among which it was apparently different at 3d,5d,7d time pionts(P<0.01). The correlation between VEGF positive cells and apoptosis positive cells at the time point of 1d,3d,5d in pure injured group was analyzed, and the result was that the expression of VEGF was negatively correlate with the positive apoptosis cells at these time points (correlation index r = -0.90052, P <0.05).Conclusions①The expression of VEGF after acute spinal cord injury is correlate with secondary pathological development of spinal cord injury. VEGF plays a part in the pathological change after secondary spinal cord injury,especially in the early date.②Secondary neuron apoptosis exist for a long time after SCI which further aggravate primary spinal cord injury.③The expression of VEGF could decrease secondary neuron apoptosis after acute spinal cord injury, and thus is closely correlated with the development of secondary spinal cord injury.④Defibrase has therapeutic effect on acute spinal cord injury through promoting the expression of VEGF which could decrease neuron apoptosis in injured location.
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