How methylprednisolone affect the apoptosis of nerve cells in the compressed spinal cord: An experimental study

Objective To investigate the protective function of methylprednisolone on the nerve cells in the continuously compressed spinal cord. Methods One hundred and forty-five Japanese white rabbits were enrolled in this experiment. Five of these rabbits were put in the blank group, seventy of them were put in the operation group and the other 70 rabbits were put in the MP treating group. Rabbits in blank group received cervical median incision to bluntly peel off the muscles without compression of spinal cord and then the incisions were sutured. Meanwhile rabbits in both operation group and MP treating group received mild spinal cord compression by setting a flap head screw between C6 and C7 after the neck. The spinal cord decompression was conducted seven days later. After 30 minutes, rabbits in the MP treating group were injected with a large amount of MP through ear border veins, while the rabbits in the operation group only received 0.9% sodium chloride injection. The transmission electron microscope were used to observe the apoptotic bodies at 6 hours, 24 hours, 3 days and 7 days after compression and 3 days, 7 days, and 14 days after decompression, flow cytometry were used to test the rate of apoptosis of spinal cord cells, and immunohistochemistry were used to test the expression of Bax protein related to apoptosis. Results The neuronal apoptosis appeared after six hours' compression in both operation group and MP treating group. The neuronal apoptosis rates in both groups peaked after three day's compression, but the apoptosis rate in MP group was lower than that in the operation group at every time point. The rates of the apoptosis in MP group and operation group became lower after the decompression of spinal cord, and there were significantly statistical differences in neuronal apoptosis rates among those decompression time points. Conclusion MP given at the early stage can reduce the neuronal apoptosis rate when spinal cord compression happens. In conclusion, using the spinal cord decompression along with MP can protect the nerve function of the compressed spinal cord.