Iinterleukin 4 In White Matter Repairing And Long-term Neurological Recovery After TBI

Part I Test the hypothesis that IL-4 post-treatment enhances WM integrity and promotes long-term neurological recovery after TBIObjective Traumatic brain injury(TBI)is one of the major concerns for neurosurgery,accumulating evidence reveal the importance of white matter(WM)repairmen in post TBI Rehabilitation.Interleukin-4 is a well-known immune modulator that regulate multiple immune responses as well as central nerve system(CNS)diseases with unclear underlying mechanisms.In this part of our study,we applied a well established CCI model to C57/BL6 mice to mimic TBI.Theraputic IL-4 nanoparticles were intranasally delivered to the mice to see its effects in WM recovery after TBI.Methods C57BL/6J mice were randomly subdivided into three group:sham,TBI+IL-4,TBI+vehicle.l)Intranasal treatment of IL-4 nanoparticles were applied to the mice after TBI with a comparison of applying PBS to the sham and TBI+vehicle,behavior tests were adopted to estimate the effect of IL-4 in neurological functions after TBI;2)Test the white matter neuroelectrophysiological fucctions to determin if post-TBI treatment of IL-4 enhances the functional integrity;3)BrdU/APC and SMI32/MBP immunohistochemical staining and diffusion tensor image to test whether IL-4 preserves the structural integrity of WM after TBI;4)MAP2 immunofluorescence staining to determine the effect of IL-4 on tissue loss.Results(1)Mice with IL-4 treatment showed better results in neurological functional tests such as cylinder test,RotaRod test and adhesive removal test(p<0.01,0.01,0.05),as well as better morris water maze test,forced swim,tail suspension test and passive avoidance test(p<0.05,0.001,0.01,0.001)that representing better cognition fuctions;(2)After IL-4 treatment,both N1 and N2 amplitude increased in neuroelectrophysiological test 35 days after TBI(p<0.05).(3)compared to vehicle group,after administration of IL-4 post TBI,BrdU+/APC+cells were increased in CC and cortex(p<0.001,0.01).BrdU+/APC-cells were increased in CC,cortex and stritum(p<0.001,0.01,0.05).BrdU-/APC+cells were increased in CC and cortex(p<0.01,0.05).As for SMI32/MBP staining,SMI32/MBP ratio were increased in CC,cortex and stritum(p<0.01,0.05,0.05).DTI image showed deceased FA value as well as an increased Rd value with no significant difference.(4)No significant decrease in tissue loss in IL-4 treating group was seen when compared to the vehicle group.Conclusion Intranasal administration of IL-4 can improve post TBI neurological rehabilitation,protect the functional and structural integrity of injured white matter,and saving tissue loss in injured area.Keywords:interleukin 4;traumatic brain injury;neurological recovery;white matter repairPart II Determine if IL-4 Induces OPCs Differentiation into Mature OLs and Promotes Remyelination via PPAR-Y ActivationObjective To investigate the effect of IL-4 on OPCs differentiation and axons myelination in vitro as well as if PPAR-Y is crucial in these activities.Determine whether PPAR-Y activation is necessary in IL-4 induced neurological recovery after TBI.Methods 1)Apply IL-4 to OPCs primary culture and neuro-glia co-culture to test the efficacy of IL-4 promoting OPCs differentiation and axonal myelination compared to the blank group in vitro;2)PPAR-Y KO mice will be used to determine if OPCs will still differentiate after use of IL-4,the efficacy will be measured by SMI32/MBP staining.2)four groups(WT+IL-4,WT+vehicle,cKO+IL-4 and cKO+vehicle)will be treated with IL-4 or PBS after TBI to determine whether PPAR-Y is crucial for IL-4 induced post TBI neurological recovery.Results(1)After applying IL-4,OPCs showed greater differentiation and mylination rate in vitro.(2)No significant difference was seen between IL-4 treatment group and vehicle group in PPAR-y knockout mice.(3)The degree of neurological functional recovery of the four groups are WT+IL-4>WT+vehicle>cKO+IL-4?cKO+vehicle.Significant diffence were seen in most of the tests.Conclusion IL-4 can promote OPCs differentiation and remyelination via activated PPAR-? after TBI.PPAR-? activation is crucial for IL-4 induced neurological recovery.