Establishment Of Rat Sciatic Nerve Injury Model And Experimental Study On The Treatment Of Denervated Muscle Atrophy And Comparison Of Surgical Methods For Late Facial Paralysis

BackgroundPeripheral nerves refer to the rest of the nerve tissue except for the brain and spinal cord.Peripheral nerve injury is a common clinical injury with potential harm.Generally speaking,peripheral nerve injury not only brings great physiological defects and psychological pressure to patients,but also causes serious economic burden to the society.Due to the complex structure of the nervous system,it is difficult to replicate in vitro,so the peripheral nerve regeneration in vitro studies is very limited.To date,the most commonly used experimental model for preclinical studies of peripheral nerve regeneration is the sciatic nerve injury model,but no experimental studies have evaluated different injury models at the same time.Peripheral nerve injury is often accompanied by muscle denervation atrophy,which makes the treatment of peripheral nerve injury more complicated.However,the mechanism of denervation muscular atrophy is very complex and the treatment methods are varied.Adipose-derived stem cells(ADSCs)are widely available and easy to obtain.ADSCs can differentiate into various cell lineages and have strong anti-inflammatory,anti-fibrosis,anti-apoptosis,and pro-angiogenesis effects in vitro or in vivo.So they have been widely used in the field of cell therapy and tissue engineering regeneration.Facial paralysis is a common peripheral nerve injury disease,when the course of the disease is more than 2 years called late facial paralysis.In order to rebuild facial muscle dynamics,muscle transplantation and nerve graft therapy have become important surgical methods for late facial paralysis.According to the methods of nerve anastomosis innervating the free muscle,it can be divided into two categories:cross-facial nerve free muscle transplantation and other nerve replacement free muscle transplantation.Objective1.To construct rat sciatic nerve injury models with different injury modes,and evaluate the damage degree of different injury models and self-repair degree after injury.2.To investigate the effect of human adipose-derived stem cells(hADSC)on muscular atrophy after sciatic nerve injury in rats.3.To compare the two surgical methods for the treatment of late facial paralysis:the free functional gracilis transfer innervated by the cross-facial nerve graft and the free functional gracilis transfer innervated by the masseteric nerve.Methods1.Construction and effect evaluation of different sciatic nerve injury models in rats:100 rats were fed in cages and divided into 5 groups:control group,sciatic nerve was exposed without any treatment;sciatic nerve transverse injury group;sciatic nerve clamp group;preserved epineurium injury model,and the epineurium was retained;chemical damage injury model,lysolated lecithin solution was injected to subepineural.Nerve electrophysiological detection of muscle action potential detection,sciatic nerve function index(SFI)determination,hot plate test,tenderness test,gastnemius mass index(GMI)determination,gastnemius micro-cross sectional area determination and sciatic nerve myelin count were performed in each group before injury,immediately after injury,14 days after injury and 28 days after injury.2.Human adipose-derived stem cells delay muscular atrophy after peripheral nerve injury in rats:fifty rats were fed in cages and divided into 5 groups:non-operation group,sciatic nerve was exposed without any operation;control group,sciatic nerve transverse injury,and Phosphate Buffer solution(PBS)was injected;hADSC injection group;PRP injection group;PRP combined with hADSC injection group.The stem cells of human origin were extracted,cultured and identified for use.The rats in each group were injected one week after operation.Sciatic nerve function index(SFI),gastrocnemius mass index(GMI)and micro-cross sectional area of gastrocnemius were measured at 2 and 4 weeks after injection.3.Gracilis transfer innervated by the cross-facial nerve graft and the masseteric nerve in late facial paralysis:according to the inclusion criteria,patients with late facial paralysis who underwent cross-facial nerve graft and the masseteric nerve were included.Preoperative and postoperative data were collected from medical records.Postoperative photos and videos were collected and House Brackmann grading was performed.The patients were included to complete the questionnaire as required,which included the patient’s current treatment status,satisfaction with the surgical outcome,and the Facial Clinical Assessment(FaCE)scale.Statistical analysis was conducted to compare the data results of the two groups of patients.Results1.The evaluations showed that the muscle action potential,sciatic nerve function index,rate of wet gastrocnemius muscle weight,area of muscle fiber,and numbers of myelinated nerve fibers were the lowest in the transverse injury group,and the nociceptive threshold and mechanical threshold were the highest.The quantitative values of chemical damage group were opposite to those in transverse damage group.There was no significant difference in the values between the clamp group and the preserved epineurium group,and all values were between the transverse group and the chemical injury group.2.At 4 weeks post-surgery,there were significant differences in the sciatic functional index between experimental(injected with hADSC,PRP,or combined hADSC+ PRP)and non-operated groups(p<0.0001),but no significant differences were observed between the different treatment groups(p>0.05).Post hoc Bonferroni tests also showed significant differences in the wet muscle weight ratios of hADSC,PRP,and combined groups compared to PBS group.The gastrocnemius muscle fiber area was larger in hADSC group and the combined group compared to PBS group at 4 weeks post-surgery.3.Of 20 eligible patients,11 gracilis transfer innervated by the masseteric nerve and 9 innervated by the cross-facial nerve graft patients participated.No significant differences were found between both groups in postoperative quality of life and satisfaction.The results of the Modified House Brackmann grading scale system were similar.Conclusion1.In the rat model of sciatic nerve injury,transverse injury models have the most stable effect among all damage models;chemical injury models self-recovery quickly and damage incompletely with poor stability of effect;clamp injury models and keep epineurium injury models have no significant differences in many ways with middle stability.2.Gastrocnemius atrophy occurs after sciatic nerve injury.The injection of hADSC delays muscular atrophy after sciatic nerve injury in rats;thus,hADSC are a promising alternative for regenerating atrophied muscle.3.For patients with late facial paralysis,we performed gracilis transfer innervated by the cross-facial nerve graft and the masseteric nerve.In this study,we found that gracilis transfer innervated by the masseteric nerve did not lead to the superior quality of life and satisfaction outcomes compared to gracilis transfer innervated by the cross-facial nerve graft.The surgeon should choose the surgical method according to the patient’s condition.