The Dynamic Change Of MiR-124 And Its Association With Axonal Regeneration After Traumatic Brain Injury In Mice

Objective: In current researches,promote axonal regeneration of neuron after the traumatic brain injury(TBI)and correct to target are hot and difficult problems in the field of neuroscience.In these researches,they were divided into two parts.Th first used a mouse TBI model and then analyzed the dynamic change of micro RNA-124(miR-124)in traumatic zone.The second intervened in the expression of miR-124 in order to observe the axonal regeneration of neuron.All these two parts explored the molecular mechanisms of miR-124 in regulating axonal regeneration of neuron through the experiments in vivo and in vitro.Methods: In vivo,the mouse TBI model was investigated by a PCI-3000 device.In vitro,a mechanical scratch model was sued to simulate neuronal injury.Neuropilin-1(Nrp-1),microtubule-associated protein tau(Tau)and growth associated protein-43(Gap-43)were taken to mark the neuronal axon,and then western blot and immunohistochemical staining were adopted to detect the contents of the three proteins and the changes of the numbers of positive cells in traumatic zone.The contents of these proteins indicated the growth of axons indirectly.Real-time polymerase chain reaction(RT-PCR)was used to examine the dynamic changes of miR-124 in vivo and in vitro,and miR-124 mimic and inhibitor were taken to intervene in the expressions of miR-124 in vitro in order to observe the difference of the axonal growth affected by expression of miR-124.Results:1 In vivo: the relative expression of miR-124 peaked the 3rd day after injury(P<0.05),Nrp-1 showed its peak the 7th day after injury(P<0.05),Tau had a peak the 14 th day(P<0.05),and Gap-43 peaked on the 1st day after injury and maintained higher level expression until the 21 st day(P<0.05).2 In vitro: the expressions of miR-124,Nrp-1,Tau and Gap-43 presented similar trends to those in the experiments in vivo with a significantly positive correlation between.After miR-124 mimic and inhibitor intervened in cells in vitro,the expressions of miR-124 decreased markedly(P<0.05).The time point of posttraumatic 12 th hour was designed as an interferential time point for comparison.At this time point,the relative expressions of Nrp-1,Tau and Gap-43 were significantly lower,and the miR-124 inhibitor group reduced more significantly than the miR-124 mimic group(P<0.05).Conclusion:1 The peak expression of miR-124 was ahead of the peak of axon markers after TBI and a positive correlation was founded.So increased expression of miR-124 might have a close association with the axon regeneration.2 Overexpression or inhibited expression of miR-124 went against promoting the regeneration of axons.Nevertheless,the inhibited expression of miR-124 blocked neuronal axon regeneration more obviously than overexpression of miR-124.3 Only moderate expression of miR-124 could better promote axonal regeneration and repair.4 The expression of Gap 43 might associate with axon repair and neuronal differentiation at the same time.