| Objective: 1,To investigate the mechanism of the secondary lesion after spinal cord injury. 2,To study the protection of cyclosporine A on the secondary lesion after spinal cord injury.Methods: The rat acute spinal cord injury model was prepared according to the modified Allen method. SD rats were divided into three groups: the control group (A group), the injury group (B group) and the spinal cord injury with mini-dose CsA-treated group(C group). The rats of group C were administered CsA through the tail vein at the early stage of spinal cord injury. The movements of hind limbs were observed in rats of groups and evaluated with BBB score,after that the rats were sacrificed and the injured spinal cord was taken out. The structure of the rat spinal cord was shown by HE staining. The expression of OMgp in the rat spinal cord was detected by immunohistochemistry staining.The expressions of OMgp mRNA in the spinal cord lesion and neighbor areas were examined by Real-time Fluorescence Quantitative PCR (RT-PCR). The expressions of OMgp protein in the spinal cord lesion were analyzed with Western blotting.Results: 1,Neurological study BBB score: Compared with the control group, nerve function in rats of the injury group and the treatment group was obviously diminished, and rats of the injury group had the most notable dysfunction. BBB scores of the treatment group were obviously better than the injured group. The difference has statistics significance. 2,Changes of the injured spinal cord with HE staining: Using light microscope, we could see the schistose bleeds within the gray matter, the central area fragmentation, axonal disruption and demyelination at 1d after injury. On the third day, neuron swelling, the cell nucleus strengthen shrink, devoid of content formation, and the glial cells fall off. At 7d after injury, quantity of surviving neuron falls off, the glial cells hyperplasia, and the glial scar formation. Bag cavity-like change appeared on the spinal cord injured area at 14d after injury. 3,Immunohistochemical method is observed: OMgp positive reaction was located in few quality glial cells and membrane, and the OMgp expression in acute injury spinal cord of rats was obvious increased. There was a little OMgp positive expression in neuron of the control group, gradually increased after injury, and obvious reach a peak at 7d after injury, then slow go down, and still comparatively highly till 14d after injury. The expression of OMgp of the group which in the low-dose CsA treatment of acute spinal cord of rats was obvious lower than the injury group at each time point, difference has statistics meaning (P <0.05). 4,RT-PCR and westemblot detection: Expression of OMgp in protein and mRNA was consistent. The normal control group showed that a small amount of expression of OMgp in mRNA and proteins. The expression began to increase ld after spinal cord injury, and significantly increased on 7d. There was significant difference between the injury group and the spinal cord injury with mini-dose CsA-treated group (P<0.05).Conclusions:CsA depresses significantly the expression of OMgp and apoptosis after spinal cord injury in rats and relieves the secondary spinal cord injury, to help promote spinal cord regeneration and neuroprotection.
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