MiR-124a Promotes The Repair Of Spinal Cord Injury By Inhibiting Neuronal Apoptosis

Background:Spinal cord injury can result in damage or loss of motor,sensory and autonomic functions below the level of injury due to the injury of spinal never fiber bundles.Therefore,finding specific targets for promoting spinal cord injury repair is of great clinical siginificance.Recent studies have shown that miRNA is involved in the secondary injury and repair process of spinal cord injury.Micro RNA-124a（miR-124a）is abundantly expressed in the central nervous system,but its effect on neuronal development and function in vivo is still unclear.Studies have shown that a time-dependent decrease in miR-124a expression after spinal cord injury may reflect cell death.However,it is not clear whether overexpression of miR-124a inhibits neuronal apoptosis and promotes spinal cord injury recovery.Objectives:1.To investigate the effect of miR-124a overexpression on neuronal apoptosis after spinal cord injury in rats.2.To elucidate the effect of miR-124a mimics on apoptosis of PC12 cells.Methods:1.SD rats were randomly divided into four groups:sham group,spinal cord injury（SCI）group,SCI+AAV-NC group and SCI+AAV-miR-124a group.BBB score was used to evaluate the motor function of rats in each group.H&E staining,TUNEL staining and immunofluorescence staining were used to observe the apoptosis of injured local cells.The expression levels of miR-124a,Bax,Bcl-2 and Caspase 3 were detected by Western blotting and q RT-PCR.2.The cells were divided into control group,H₂O₂ group,H₂O₂+NC group and H₂O₂+miR-124a mimics group.The growth state of cells in each group was observed under a light microscope.Annexin V-FITC/PI staining and immunofluorescence staining were used to observe the apoptosis of each group.The expression levels of miR-124a,Bax,Bcl-2 and Caspase 3 were detected by Western blotting and q RT-PCR.Results:1.After spinal cord injury,the motor function of rats was lost,a large number of spinal cord neurons underwent apoptotic,causing serious damage to the spinal cord tissue.MiR-124a mRNA levels increased briefly and then decreased continuously.The expression of Bax mRNA and protein increased,the expression of Bcl-2 mRNA and protein decreased,and the expression of Caspase 3 protein increased.Overexpression of miR-124a reversed the aforementioned mRNA and protein expression levels,reduced the apoptosis of spinal cord neurons,improved the morphology of spinal cord tissue,and gradually restored the motor function of rats.2.After H₂O₂ induction,most of the cells in the H₂O₂ induction group died,and cell morphpgy was poor,the expression levels of miR-124a mRNA,Bcl-2 mRNA and Bcl-2protein were significantly lower than those in the Control group,and the expression of Caspase 3 protein was significantly increased.After pretreatment with miR-124a mimics,the cell growth state was better,between the control group and the H₂O₂ induction group,and the dead cells were less than the H₂O₂ induction group.After pretreatment with miR-124a mimics,the level of Bcl-2 mRNA was significantly increased,and the protein expression was increased.The expression of Caspase 3 protein decreased.ConclusionAfter spinal cord injury in rats,neuronal apoptosis is significant and hindlimb motor function was lost.Overexpression of miR-124a can inhibit neuronal apoptosis,improve motor function in rats,and promote the repair of spinal cord injury.