The Expression Of Neuregulin-1 And Its Protection Following Acute Optic Nerve Injury In Rat

OBJECTIVENerve regeneration,especially central nervous system(including optic nerve),its regeneration is always the important topic in the neuroscience.Acute optic nerve injury is frequent in ocular injury.Clinically,it is always taking expectant treatment as well as decompression of optic canal,which are always ineffective,till now there is no specific treatment.Neuregulin-1(NRG-1) conduce neural axis extend to target area and the development of synapsis in those areas,full-grown cortical neuronal network can extensively remodeling,moreover it can enhance such factors as they can promote neuron differentiation which show important effects in the synapse regeneration,NRG-1 and its ErbB receptors can also enhance conjunction among mature nemon.For the past few years,it has been found during the neuronal degenerative process,different NRG-1 level variation and the co-balance among them as well as other neurotrophic factorallplay important roles.This research first set up the model of acute optic nerve ring clamp injury,then to utilize it,establish in different period the NRG-1 variation in optic nerve and RGCs.And inject variation dosage of NRG-1 in vitreous chamber,to study the possible mechanism and the interaction among them.METHODSPart 1:Disregarding gender,48 matured rats eye for operation(randomly 24 for sham operation group,24 for experimental group),left eye for operation,right eye do nothing,after ring clamp every group profess FVEP and eyeground photography to observe the state of optical nerve injury qualitedly.and 2h,1d,2d,7d,14d,28d after operation to put experimental animal to death,eyeballs involving ON were obtained to evaluate the damage using light microscope after HE staining and mmunity class was extracted to analyze the changes of neuregulin-1's level expression compared with the control group in vitro after execution.Part 2:Disregarding gender,100 matured rats were medially divided into 5 groups randomly:common group(n=20),acute optic nerve wound group;all experimental animal left eye for operation,right eye do nothing,to build model as part 1,after injuy neuregulin-10.5ug,lug,3ug(each group n=20) were injected into vitreous chamber one time respectively,isometrical NS were injected in the control group(n=20).after ring clamp 1d,2d,7d,14d,28d every group profess FVEP and eyeground photography to qualitation optic nerve damage and reparation,1d,2d, 7d,14d,28d after operation to put experimental animal to death,eyeballs involving ON were obtained to evaluate the damage using light microscope after HE staining and TUNEL to analyze the changes of RGCs and its apoptosis compared with the control group in vitro after execution.RESULTS:Part 1:1.Morphous,electrophysiology,pathology observation after building modelEyeground photography:the difference in sham operated group was not significant.After acute optic nerve ring clamp 2h-7d eyeground photography was not significant to the normal one,then 2w optic papilla gradual etiolate.till 4w whiteness basicly stereotypia.FVEP:Shape ofFVEP(P₁,N₁ and P₂) diversed obviously and irregular figures appeared 2h after injury:Latence prolonged and amplitude cut down. The changes of FVEP slightly revived,but still lower than 50%of the normal,the injury groupshad statistical significance to the normal one at each time point. (P＜0.05).HE staining:Retina in sham operation group had no marked changes but gentle dropsy.The number and alignmentof nucelus has no obviously changed.The histological change in experimental group manifest dropsy in2h,especially in nerve fiber layer and reticular layer dyeing light.In 1-2d retinal edema fundamental fading,reflecting the number of RGCs decrease,cell degeneration,nerve fiber layer thinning,inner nuclear layer disorder outer nuclear layer thinning;In 7-14d entoretina obviously become thin;till 4w the change is not obviously.2.The expression of NRG-1Compared to sham operated group,2h,1d,2d,7d,14d after acute ON injury, The expression of NRG-1 at each time point is obviously increasing(P＜0.05), among the total,14d is peak;then fall-off to normal in28d,which is not statistically significant to sham operated group(P＞0.05). Part 21.Eyeground photography:There was not significant in each group during themorning after injury.till 2w the eyeground NRG-1 groups not statistically significant to common rential tissue.2.FVEP:The amplitude of FVEP in each group fallen down to the lowest in the first day,slightly revived,to view the difference of each time point,14d manifest most(P＜0.05).Compared to the time of incubation period,NRG-10.5ug group has no statistical significance to NS group(P＞0.05);except 1d timepoint,1ug NRG-1 group other time point has statistical significance to NS group(P＜0.05),especially in 14d,28d,the statistical significance is obviously(P＜0.01).3ug NRG-1 group has statistical significance to NS group,especially in 7d,14d,28d,the statistical significance is obviously(P＜0.01).3.HE staining:NS group retinal RGCs arrangement obviously sparseness,multiple RGCs nuclear fragmentation chromoplasm fringe gather;vacuolar degeneration,nerve fiber layer obviously thinningz,;NRG-10.5ug group is similary to NS group;NRG-1 1ug,3ug group retinal RGCs arrangement fairly raritas,RGCs form is normal,among cells,there are Muller fiber,vacuolar degeneration,nerve fiber layer thin,but they are better than NS group.We count the number of RGCs in 2d,7d,14d after injury.,the number of both is decreasing in 2w,but in 7d,14d the number of RGCs in NRG-1 groups is higher than NS group,the difference is statistical significance(P＜0.01).4.TUNEL:Retinal apoptosis cell appear in INL,GCLand ONL nearly no masccline expression.With regard to NS group,NRG-1 group(0.5ug,1ug,3ug) each time point the number of RGCs apoptosis is fewer.Nerve tissue is also found apoptosis gliocyte,show brown dyeing.0.5ug NRG-1 group each time point the number of RGCs apoptosis has no statistical significance to NS group(P＞0.05);except 1d timepoint,lug NRG-1 group other time point has statistical significance to NS group(P＜0.05);3ug NRG-1 group the number of RGCs apoptosis has statistical significance to NS group,especially in 7d,14d,28d,the statistical significance is obviously(P＜0.01).CONCLUSION: 1.To establish optic nerve injury model of cat successfully;the fluorscent immunohistochemcal method was used to detect the expresson of NRG-1 in normal rat nerve cell and retina tissue,then constructed the model of acute optic nerve injury in rat.We observed that the expression of NRG-1 in normal nerve cell and retina tissue is extensive,after injury,the expression of NRG-1 increased in the first few days and then fall These result suggested that NRG-1 is necessary for maintenance of normal optic nerve function in rat,and NRG-1 may play a certain role in the pathological changes of optic nerve and retina tissue.2.NRG-1 can effectively reduce the apptosis of nerve cell and retina tissue,this result suggest that NRG-1may play essential role in repairing and protecting acute optic nerve injury.3.It is critical to reduce the damage of optic nerve injury and protect RGCs from poptosis.Based on our results,it is better to apply NRG-1 as early as possible after acute optic nerve injury.