CRMP2 Promotes Repairment Of Neuronal Dendritic Spines After Traumatic Brain Injury

OBJECTIVE: To investigate the role of CRMP2 in the regeneration and repair of neuronal dendritic spines after traumatic brain injury(TBI).Methods: 1.Thy1-GFP mouse TBI was established through controlled cortical impact injury model(CCI).The changes of dendritic spine density and morphological were observed on the 1st day postinjury(P1D)and the 7th day postinjury(P7D).2.The expression of CRMP2 on P1 D and P7 D was verified by immunoblotting and immunofluorescence.3.The plasmid of CRMP2 overexpression and knockdown were constructed,and transfected into the cultured neurons in vitro to observe the change of the dendritic spines.4.The virus of CRMP2 overexpression,CRMP2 knockdown and vector were injected into ICR mice hippocampus by stereotactic injection.CCI injury was performed 4 weeks later,and neuron dendritic spines were observed on P7 D.5.The effect of CRMP2 overexpression and knockdown on the learning and memory function was observed by freezing time and freezing frequency in fear conditioning behavioral experiment.Results: 1.The dendritic spine density of hippocampus and cortex in Thy1-GFP mice was decreased on P1 D,in which the mushroom type and thin type were mainly lost.While the dendritic spine density increased on P7 D,most of which were thin type spines.2.The total amount of CRMP2 was decreased on P1 D,but the breakdown product of CRMP2 was increased.On P7 D,the total amount of CRMP2 was increased,while the breakdown product of CRMP2 was reduced.3.In vitro.,CRMP2 could increase the dendritic spine density of cultured neurons,while CRMP2-shRNA could reduce the neuron dendritic spine density.4.In vivo.,there was no significant difference in dendritic spine density between the TBI+ vector group and the sham+ vector group,but the thin type spines were increased while the mushroom type spines were reduced in the TBI + vector group.Compared with TBI+ vector group,the dendritic spine density of TBI + CRMP2-shRNA group was reduced,in which both the thin and mushroom type spines were decreased.On the contrary,the dendritic spine density in TBI + CRMP2 overexpression group was increased,and most of them were mushroom type dendritic spines.5.The freezing time and freezing frequency of TBI+vector group was lower than that of sham+vector group.Compared with TBI+vector group,the freezing time and freezing frequency of TBI+CRMP2-shRNA group were lower,while the TBI+CRMP2 overexpression group’s were higher.CONCLUSION:CRMP2 can promote the regeneration and repair of dendritic spines and restore learning and memory function after TBI.