Construction Of Animal Model Of Chronic Compressive Spinal Cord Injury And Exploration Of Nerve Cell Status

Background:Chronic compressive spinal cord injury is a common type of spinal cord injury.At present,the animal models that can simulate chronic compressive spinal cord injury mainly include screw compression model,water-absorbent material compression model,tumor implantation model and twy animal model,but these models do not meet the conditions of applicability,controllability,practicability and economy of animal models in some aspects.So based on these animal models,we reconstruct an economic and practical animal model which can simulate the process of slow compression of the spinal cord by limiting the space for spinal cord growth.Clinically,we found that the degree of compression in chronic compressive spinal cord injury was not consistent with the neurological function.The current researchs showed that the slow compression of the spinal cord will produce the damage mechanism of the neurovascular unit,inflammatory response and apoptosis of nerve cells,and also the compensatory mechanism of astrocyte proliferation.However,there was no reasonable explanation for the discrepancy between the degree of compression and neurological symptoms in chronic compressive spinal cord injury.Purposes:The purpose of this study is to establish an animal model that can simulate the slow compression of the spinal cord,so as to lay a foundation for exploring the molecular mechanism of chronic compressive spinal cord injury.On the basis of the animal model,we explored the phenomenon that the degree of compression in the process of spinal cord compression was not consistent with the neurological symptoms from the aspects of astrocytes,microglia,neuronal activity and glucose metabolism.Methods:Three week old SD rats were randomly divided into two groups: model group and sham operation group.The chronic compressive spinal cord injury animal model was formed by limiting the growth of the spine with nylon tape,and the compression degree of the spinal cord in the model group was monitored by regular MRI.In order to monitor the matching degree of spinal cord compression and nerve function of rats,while monitoring the state of spinal cord compression,we evaluated the behavior of rats by BBB score,mechanical pain threshold measurement and hot plate experiment.After the behavioral stability of rats,we explored the state of neural cells through the expression of specific molecular markers.GFAP and Iba-1 are the specific markers of astrocytes and microglia,respectively.Therefore,GFAP and Iba-1 were mainly used in this study to detect astrocytes and microglia.Nissl staining can specifically label Nissl body in neurons,and NEUN is neuron-specific antigen.So we mainly detected the state of neurons by Nissl staining and NEUN Western blotting experiment.In order to explain the phenomenon of mismatch between clinical symptoms and compression degree in chronic spinal cord compression from the perspective of neuron activity and glucose metabolism,we used immunofluorescence double staining and Western blotting to monitor the expression of CFOs,FosB,GLUT1 and hexokinase Ⅱ in neurons.Results:In this study,MRI was used to monitor the degree of spinal cord compression in rats.The results showed that at 9W,the degree of spinal cord compression in the model group tended to be stable,and different degrees of spinal cord compression occurred.BBB score showed that the movement of the model group and the sham operation group did not change(P > 0.05);the sensory function of the two groups was evaluated from two aspects of mechanical pain and thermal pain.The results showed that the mechanical pain of the two groups did not produce a stable difference(P > 0.05),while the model group had stable thermal hyperalgesia after 1 W(P < 0.001).The results of monitoring the status of astrocytes and microglia in chronic spinal cord compression showed that there was no significant change of astrocytes in chronic spinal cord compression(P > 0.05),but the microglia count decreased significantly(P < 0.001).The results showed that there was no difference in the number of neurons between the two groups(P > 0.05);NEUN Western blotting was used for auxiliary verification,and the results were consistent with Nissl staining.Western blotting was used to monitor the activity of neurons and glucose metabolism in chronic compressive spinal cord injury.The results showed that the expression of CFOs protein in the neurons in the compression site of the spinal cord was significantly increased(P < 0.05),while the expression of FosB was not significantly changed(P > 0.05);the expression of GLUT1 in the neurons in the compression site was increased(P < 0.05),while the expression of hexokinase Ⅱ was not significantly changed(P > 0.05).The results of immunofluorescence were consistent with those of Western blotting.Conclusion:We have successfully constructed an animal model to simulate the slow compression process of chronic spinal cord injury.On the basis of this animal model,we found that astrocytes has no obvious changes after spinal cord compression,while microglia decreases after chronic compressive spinal cord injury.The main changes of neurons in chronic compressive spinal cord injury are as follows: 1.The increased activity of neurons increases the sensitivity of neurons to external stimulation;2.After chronic compressive spinal cord injury,glucose metabolism of neurons is maintained by high expression of GLUT1,which may be the main reason why the degree of compression in chronic compression spinal cord injury does not match the clinical symptoms.