Efficacy Of Electrical Stimulation In The Treatment Of Facial Nerve Injury And Possible Changes In Neurotrophic Factors Expression

Objective:To investigate the efficacy and time window of electrical stimulation in the treatment of facial nerve injury and possible changes in neurotrophic factors expression.Methods:In part one,main trunk of the right facial nerve was exposed and transected close to its emergence out of the foramen stylomastoideum.At the designated postoperative survival periods of 2,7,14 and 28 days post-facial nerve transection and anastomosis,behavior(mimetic muscle movements)and facial nerve electromyography were evaluated weekly and facial nerve specimens were stained with hematoxylin and eosin for histological examination of axon density.Expression of markers of neural tissue regeneration(S-100B),as well as proliferating Schwann cells and myelin-axon relationships(NF200),were also focused on.In the study,the animals were randomly allocated to one of four treatment groups(fifteen rats/group):facial nerve resection intervention(Group A),facial nerve resection and electrical stimulation(Group B),end-to-end anastomosis with epineural sutures after facial nerve resection(Group C)and end-to-end anastomosis with epineural sutures after facial nerve resection followed by electrical stimulation(Group D).Data were statistical evaluated,the level of significance was set to p<0.05.Data of group A was compared with group B,data of group C was compared with group D.In part two,the extent of up-or downregulation of neurotrophic factors(BDNF,NT-4,FGF2,IGF1,and IGF2)in the muscle part with most numerous NMJs of the levator labii superioris muscle was determined by quantitative PCR and Western blot.At the designated postoperative survival periods of 2,7,14 and 28 days post-facial nerve transection and anastomosis,qPCR and Western blot data of group A was compared with group B,data of group C was compared with group D.Results:In part one,facial nerve regeneration over time.On the 7th day the facial nerve function began to recover.The recovery rate of facial paralysis in group B was significantly higher than that in group A.Electrochemically physiological results also show that there are differences in action potential of the lead rate between group A and group B on the 14th and the 28th day and from the 7th day between group C and group D.Usingχ~2 test neuronal electrophysiological results showed on day 1 and day 7,the action potentials were not elicited without difference and on day 14 and 28 with difference.There was no difference in the action potential of the C and D groups on the first day after facial nerve injury and difference show out on the 7th,14th and 28th day.There was a significant difference in latency at day 1and 14.Volatility in the 14th day and 28th day difference was statistically significant(P<0.05).In HE staining,day 1 and day 7 were not significantly different,showing to damage the distal facial nerve fibers myelin have varying degrees of thinning or defects.Intracellular and fibrous bundles showed a lot of vacuoles formed.A large number of axons disappeared,structural disorders,uneven,sparse nerve fibers,the difference between the groups is not very obviousNerve fibers are swelling,myelin is still absent on day14 and axonal morphology irregular,no obvious recovery of myelinon day 28 in group A.Increased number of axons in the nerve fibers,swelling improved,surrounded by a small nerve bundle into the proliferation of repair nerve bundles on the 14th day.Axonal morphology is normal,but the edge of irregular waves,the surrounding myelin is also restored in group B.Distal nerve fibers are more coarse and compact after electrical stimulation in group B and group D than that in group A and group C.Immunofluorescence staining results showed that the NF200 of the distal nerve was not upregulated at each time point from the 1th to the 28th day in group A.NF200 was slightly up-regulated on the 14th without difference between group B and the control group.On the 28th day,the percentage of NF200 fluorescence staining was up-regulated,compared with the normal control group,the difference was statistically significant which indicated regeneration of axonal myelination.NF200 was weakly positive only on day 28 in group C and was positive on the 28th day in group D.The expression of S100B protein was significantly higher in the distal nerve tissue of the group B and group D adjacent to the facial nerve at the 14th and 28th day after receiving electrical stimulation.The expression of S100B protein was not up-regulated in the distal nerve tissue of rats adjacent to facial nerve truncation without receiving electrical stimulation.In part two,There was no increase in neurotrophic factors at each time point in group A.BDNF and NT4 mRNA and protein upregulated on the 7th,14th and 28th day in group B.BDNF and NT4 mRNA and protein upregulated on the 14th and 28th day in group C.BDNF,FGF2 and NT4 m RNA and protein upregulated on the 7th,14th and 28th day in group D.Intramuscular IGF1 mRNA was slightly up-regulated on day 7 after electrical stimulation and then resumed as usual.The IGF2 mRNA and protein in group B and group D undergoing electrical stimulation decreased only on day 1 and no significant changes were observed afterword.Conclusion:Electrical stimulation can effectively promote facial nerve axon regeneration andaccelerate facial nerve function recovery.Electrical stimulation can promote the expression of neurotrophic factor(BDNF,FGF2,NT4)in neuromuscular junctions.