| ObjectionFunctional repair of peripheral nerve injury has been a difficult problem in medicine,often leads to serious limb dysfunction and affects the live quality of patients.Excessive hyperplasia of peripheral nerve scar will prevent axonal sprouting.The injured peripheral nerve is easy to adhesion with the surrounding tissue which prevents nerve slippage,can lead to neuronal ischemic changes,is not conducive to the regeneration and functional recovery of peripheral nerve.Although there are many treatment methods for inhibiting peripheral nerve scar formation after peripheral nerve injury,the therapeutic effect is often unsatisfactory.How to effectively inhibit the formation of peripheral nerve scar and promote the repair of peripheral nerve function is an important subject in the field of clinical medicine.The mechanism of peripheral nerve scar hyperplasia is very complex.Dexamethasone as long-acting glucocorticoid,can affect the apoptosis of fibroblasts and the formation of scar.By reading a lot of literature,it has not been found that some scholars have investigated whether dexamethasone can inhibit the formation of nerve scar after peripheral nerve injury.In this subject,we established SD sciatic nerve crush injury models,locally injected dexamethasone injection,observed the sciatic nerve function repair and scar hyperplasia after operation.Hope to provide new ideas for clinical treatment and lay foundation for the further study.Methods40 SD male rats were randomly divided into 2 groups(A group and B group).Then we establish the model of right sciatic nerve crush injury in each rat.The SD rats in A group was locally injected with saline(1mL),B group rats was locally injected with dexamethasone injection 0.5mg/Kg(prepared in saline 1mL).The frequency of local injection was once a week.The general situation of postoperative SD rats were observed.The sciatic nerve conduction velocity and nerve electrophysiological test were measured at 4 weeks,8 weeks,and 12 weeks after operation,respectively.At postoperation 12 weeks,measured the nerve scar adhesion and the survival rate gastrocnemius wet mass,analyzed sciatic nerve tissue of the crush site by western blot,HE stain and Realtime PCR.Results(a)The time of right foot paw reflex of SD rat in A group was 25.7±2.32 days.The time of right foot paw reflex of SD rat in B group was 21.3±3.13 days.The average recovery time of claw reflex of right lower limb in B group was shorter than that in A group,and the difference was so statistically significant(P<0.05).(b)At 4 weeks after operation,the SFI value of SD rats in A group and B group were-80.6±6.69,-73.4±7.24,respectively.At 8 weeks after operation,the SFI value of SD rats in A group and B group were-65±8,-55.5±5.91,respectively.At 12 weeks after operation,the SFI value of SD rats in A group and B group were-54.6±7.38,-45.7±5.64,respectively(At postoperation 4 weeks P<0.01,At postoperation 8 weeks and 12 weeks P<0.001).(c)At 4 weeks after operation,the NCV value of SD rats in A group and B group were 32±3.21,38.4±4.29,respectively.At 4 weeks after operation,the NCV value of SD rats in A group and B group were 39.9±3.74,46.6±5.64,respectively.At 4 weeks after operation,the NCV value of SD rats in A group and B group were 39.9±3.74,46.6±5.64,respectively.There was significant difference between the two groups(P<0.001).(d)Isolation of skin,muscle and fascia of SD rats in B group were easier than A group at postoperation 12 weeks,but there was no statistical difference(P>0.05).Isolation of nerve tissue in B group were also easier than A group,the difference was statistically significant(P<0.01).(e)At postoperation 12 weeks,under optical microscope(X 100),there were few fibroblasts in the nerve tissue of the dexamethasone group,the number of nerve fibers were more and regular arrangement,however,in control group,there were more fibroblasts,nerve fibers were sparse,disorganized.(f)At postoperation 12 weeks,the expression of type Ⅰ collagen and type Ⅲcollagen at the right sciatic nerve injury site of SD rats in B group is much lower than A group,the difference was obvious(P<0.05 and P<0.01,respectively).Compared with the control group,the expression level of TGF-1 and Smad4 in dexamethasone group was significantly lower(P<0.05 and P<0.01,respectively).(g)At postoperation 12 weeks,compared with the control group,the mRNA expression level of Smad4 and TGF-β1 in dexamethasone group was significantly lower(P<0.01).(h)At 12 weeks after operation,B group had higher survival rate of gastrocnemius wet mass than A group,there was statistical difference(P<0.001).ConclusionDexamethasone can down regulate the expression of TGF-β1 and Smad4 at the site of sciatic nerve injury,inhibit the formation of peripheral nerve scar,and improve the peripheral nerve function repair. |
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