A Rat Model Of Blast Induced Spinal Cord Injury And Preliminary Study Of The Mechanism

As for clinicians, the treatment of spinal cord injury have been always full of challenges. Spinal cord injury not only bring great pain to the patients, but also cause serious influences to social welfare. With the increasing number of local wars, terrorism and suicide bombings, and the number of blast induced spinal cord injury patients become more and more. Therefore, the blast induced spinal cord injury become a focus in scientific communities. Unfortunately, at present very few researches on the blast induced spinal cord injury. Moreover, the pathological processes of the blast induced spinal cord injury are still not clear. However, very few reports about animal model in this area. So it is necessary to establish an animal model on blast induced spinal cord injury and providing a new model for basic researches and clinical treatments.Objective Firstly, to develop a reliable and stable blast induced spinal cord injury device which generate shock wave and simulate blast injuries caused by the explosion of the papery electric detonator. Secondly, to establish the rat model of blast induced spinal cord injury at different extents. Thirdly, preliminary study on the mechanism of blast induced spinal cord injury.Methods Development a rat model device for studying blast induced spinal cord injury by using 800mg TNT as the explosive source. According to the characteristics of shock wave, ninety-six male Sprague-Dawley rats(weight between 250-300g) were randomly divided into five groups:4-cm(n=12),5-cm(n=26),7.5cm(n=26),10-cm(n=26) and the control group(n=6). By measurement the overpressure of blast wave under different explosive distance and, to evaluate the model device by observing the clinical features of the animals, the behavioral and histopathological changes.Results (1) By using 800mg TNT as the explosive source, the peak overpressure of blast wave in the 5-cm group is 998.68KPa, the 7.5-cm group is 682.54KPa and the 10-cm group is 245.90KPa. (2) Different degrees of clinical symptoms depend on different distances. Respiratory apnea could be seen in all experimental groups. Besides, the symptoms of limb seizure and hemorrhinia also could be seen both in the 5-cm group and the 7.5-cm group. The more closer distance the more severer clinical symptoms happened. (3) On one hand, different explosive distance lead to BBB scale significantly difference, and it is notable that a permanent paraplegia could be seen in all the 5-cm group animals. Despite of the injury time up to 7 days, the BBB scale reach only 8 to 9 points in this group.However,following the first day of the explosion the 7.5-cm group’s BBB scale reach at 12 to 13 points and reach up to 21 points on the 7th day. Interestingly, at the 1st day the 10-cm group’s scale has been reached up to 21 points. On the other hand, both the 5-cm group and the 7.5-cm group showed different degrees of movement disorders compared with the control group, i.e., both in ipsilateral forelimb stride length and locomotor speed were significantly difference(P<0.05). However, no statistical differences between the 10-cm group and the control group(P<0.05). (4)HE staining and Nissl’s staining showed that different explosive distance lead to different degree of spinal cord injury. The number of neurons and nissl bodies were significantly reduced in all experimental groups. On the 7th day, the anterior horn of spinal cord has no neuron survival in the 5-cm group, and in the group of 7.5-cm the number of neurons and nissl bodies were significantly reduced accompany with the phenomena of cell necrosis and apoptosis. The amount of spinal cord anterior horn motor neurons were directly related to the change of movement function. Noteworthily, despite of no clinical symptoms and movement disorders, the morphology of anterior horn neuron has changed,i.e.,the number of nissl bodis is still less than the control group.Conclusion:(1) Our team established a novel rat model device with fine stability and repeatability, and overcome the drawbacks of other models. (2) The device can simulate the shock wave generation, and we successfully established a blast induced spinal cord injury in three varying degrees,i.e.,the 5-cm, the 7.5-cm and the 10-cm group. (3) Our findings demonstrated that the amount of spinal cord anterior horn motor neuron was directly related to the change of movement function, the fewer the number of anterior horn motor neurons the heavier the movement function impaired.