Mesenchymal stem cells for repairing glaucomatous optic nerve

Glaucoma is a common and complex neurodegenerative disease characterized by progressive loss of retinal ganglion cells(RGCs)and axons.Currently,there is no effective method to address the cause of RGCs degeneration.However,studies on neuroprotective strategies for optic neuropathy have increased in recent years.Cell replacement and neuroprotection are major strategies for treating glaucoma and optic neuropathy.Regenerative medicine research into the repair of optic nerve damage using stem cells has Received considerable attention.Stem cells possess the potential for multidirectional differentiation abilities and are capable of producing RGCfriendly microenvironments through paracrine effects.This article reviews a thorough researches of recent advances and approaches in stem cell repair of optic nerve injury,raising the controversies and unresolved issues surrounding the future of stem cells.

Long noncoding RNA H19 regulates degeneration and regeneration of injured peripheral nerves

Our previous studies have shown that long noncoding RNA(lncRNA)H19 is upregulated in injured rat sciatic nerve during the process of Wallerian degeneration,and that it promotes the migration of Schwann cells and slows down the growth of dorsal root ganglion axons.However,the mechanism by which lncRNA H19 regulates neural repair and regeneration after peripheral nerve injury remains unclear.In this study,we established a Sprague-Dawley rat model of sciatic nerve transection injury.We performed in situ hybridization and found that at 4–7 days after sciatic nerve injury,lncRNA H19 was highly expressed.At 14 days before injury,adeno-associated virus was intrathecally injected into the L4–L5 foramina to disrupt or overexpress lncRNA H19.After overexpression of lncRNA H19,the growth of newly formed axons from the sciatic nerve was inhibited,whereas myelination was enhanced.Then,we performed gait analysis and thermal pain analysis to evaluate rat behavior.We found that lncRNA H19 overexpression delayed the recovery of rat behavior function,whereas interfering with lncRNA H19 expression improved functional recovery.Finally,we examined the expression of lncRNA H19 downstream target SEMA6D,and found that after lncRNA H19 overexpression,the SEMA6D protein level was increased.These findings suggest that lncRNA H19 regulates peripheral nerve degeneration and regeneration through activating SEMA6D in injured nerves.This provides a new clue to understand the role of lncRNA H19 in peripheral nerve degeneration and regeneration.

Electroacupuncture promotes peripheral nerve regeneration after facial nerve crush injury and upregulates the expression of glial cell-derived neurotrophic factor

The efficacy of electroacupuncture in the treatment of peripheral facial paralysis is known, but the specific mechanism has not been clarified. Glial cell-derived neurotrophic factor(GDNF) has been shown to protect neurons by binding to N-cadherin. Our previous results have shown that electroacupuncture could increase the expression of N-cadherin mRNA in facial neurons and promote facial nerve regeneration. In this study, the potential mechanisms by which electroacupuncture promotes nerve regeneration were elucidated through assessing the effects of electroacupuncture on GDNF and N-cadherin expression in facial motoneurons of rabbits with peripheral facial nerve crush injury. New Zealand rabbits were randomly divided into a normal group(normal control, n = 21), injury group(n = 45) and electroacupuncture group(n = 45). Model rabbits underwent facial nerve crush injury only. Rabbits in the electroacupuncture group received facial nerve injury, and then underwent electroacupuncture at Yifeng(TE17), Jiache(ST6), Sibai(ST2), Dicang(ST4), Yangbai(GB14), Quanliao(SI18), and Hegu(LI4; only acupuncture, no electrical stimulation). The results showed that in behavioral assessments, the total scores of blink reflex, vibrissae movement, and position of apex nasi, were markedly lower in the EA group than those in the injury group. Hematoxylin-eosin staining of the right buccinator muscle of each group showed that the cross-sectional area of buccinator was larger in the electroacupuncture group than in the injury group on days 1, 14 and 21 post-surgery. Toluidine blue staining of the right facial nerve tissue of each group revealed that on day 14 post-surgery, there was less axonal demyelination and fewer inflammatory cells in the electroacupuncture group compared with the injury group. Quantitative real time-polymerase chain reaction showed that compared with the injury group, N-cadherin mRNA levels on days 4, 7, 14 and 21 and GDNF mRNA levels on days 4, 7 and 14 were significantly higher in the electroacupuncture group. Western blot assay displayed that compared with the injury group, the expression of GDNF protein levels on days 7, 14 and 21 were significantly upregulated in the electroacupuncture group. The histology with hematoxylin-eosin staining and Nissl staining of brainstem tissues containing facial neurons in the middle and lower part of the pons exhibited that on day 7 post-surgery, there were significantly fewer apoptotic neurons in the electroacupuncture group than in the injury group. By day 21, there was no significantly difference in the number of neurons between the electroacupuncture and normal groups. Taken together, these results have confirmed that electroacupuncture promotes regeneration of peripheral facial nerve injury in rabbits, inhibits neuronal apoptosis, and reduces peripheral inflammatory response, resulting in the recovery of facial muscle function. This is achieved by up-regulating the expression of GDNF and N-cadherin in central facial neurons.

Olfactory ensheathing cells promote nerve regeneration and functional recovery after facial nerve defects

Olfactory ensheathing cells from the olfactory bulb and olfactory mucosa have been tbund to increase axonal sprouting and pathfinding and promote the recovery of vibrissae motor performance in facial nerve transection injured rats. However, it is not yet clear whether olfactory ensheathing cells promote the reparation of facial nerve defects in rats. In this study, a collagen sponge and silicone tube neural conduit was implanted into the 6-mm defect of the buccal branch of the facial nerve in adult rats. Olfactory ensheathing cells isolated from the olfactory bulb of newborn Sprague-Dawley rats were injected into the neural conduits connecting the ends of tile broken nerves, the morphology and function of the regenerated nerves were compared between the rats implanted with olfactory ensheathing cells with the rats injected with saline. Facial paralysis was assessed. Nerve electrography was used to measure facial nerve-induced action potentials. Visual inspection, anatomical microscopy and hematoxylin-eosin staining were used to assess the histomorphology around the trans planted neural conduit and the morphology of the regenerated nerve. Using fluorogold retrograde tracing, toluidine blue staining and lead uranyl acetate staining, we also measured the number of neurons in the anterior exterior lateral f：acial nerve motor nucleus, the number of myelinated nerve fibers, and nerve fiber diameter and myelin sheath thickness, respectively. After surgery, olfactory ensheathing cells de- creased facial paralysis and the latency of the facial nerve-induced action potentials. There were no differences in the general morphology of the regenerating nerves between the rats implanted with olfactory ensheathing cells and the rats injected with saline. Between-group results showed that olfactory ensheathing cell treatment increased the number of regenerated neurons, improved nerve fiber morphology, and increased the number of myelinated nerve fibers, nerve fiber diameter, and myelin sheath thickness. In conclusion, implantation of olfactory ensheathing cells can promote regeneration and functional recovery after facial nerve damage in rats.

Immunobiology of Facial Nerve Repair and Regeneration

Immunobiological study is a key to revealing the important basis of facial nerve repair and regeneration for both research and development of clinic treatments. The microenvironmental changes around an injuried facial motoneuron, i.e., the aggregation and expression of various types of immune cells and molecules in a dynamic equilibrium, impenetrate from the start to the end of the repair of an injured facial nerve. The concept of 'immune microenvironment for facial nerve repair and regeneration', mainly concerns with the dynamic exchange between expression and regulation networks and a variaty of immune cells and immune molecules in the process of facial nerve repair and regeneration for the maintenance of a immune microenvironment favorable for nerve repair. Investigation on microglial activation and recruitment, T cell behavior, cytokine networks, and immunological cellular and molecular signaling pathways in facial nerve repair and regeneration are the current hot spots in the research on immunobiology of facial nerve injury. The current paper provides a comprehensive review of the above mentioned issues. Research of these issues will eventually make immunological interventions practicable treatments for facial nerve injury in the clinic.

Protective effects of nerve regeneration factor and brain-derived neurotrophic factor on retinal ganglion cells in a rabbit model of acute hyper-intraocular pressure

BACKGROUND： Previous studies have shown that nerve regeneration factor （NRF） provides neuroprotective effects. However, the neuroprotective effects on retinal ganglion cells in an animal model of glaucoma remain uncertain. OBJECTIVE： To determine the neuroprotective effects of NRF on retinal ganglion cells in a rabbit model of acute hyper-intraocular pressure and to compare the effects on brain-derived neurotrophic factor （BDNF）. DESIGN, TIME AND SETTING： A randomized, controlled, animal experiment was performed at Jiangsu Provincial Key Laboratory of Neural Regeneration from September 2006 to August 2007. MATERIALS： Sterone, a major component of NRF, was provided by the Key Laboratory of Neural Regeneration, Nantong University in China; BDNF was provided by BioDesign Inc., USA. METHODS： A total of 24 healthy rabbits were randomly assigned to NRF, BDNF, and phosphate buffered saline groups, with 8 rabbits per group. The left eyes were considered normal controls, and acute hyper-intraocular pressure was induced in the right eyes via anterior chamber perfusion. The right camera vitrea bulbi was injected with 4.5 μg NRF, 3.75 μg BDNF, or 5 μL 0.1 mol/L phosphate buffered saline, respectively. MAIN OUTCOME MEASURES： Retinal ganglion cells were reverse-labeled using horseradish peroxidase to quantify cell density at 2, 4, and 6 mm from the optic disc edge. RESULTS： NRF increased the number of surviving retinal ganglion cells at the optic disc edge （P 〈 0.01 or P 〈 0.05）. The density of surviving retinal ganglion cells decreased with increasing distance from the optic disc. The number of retinal ganglion cells in the BDNF group was similar to the NRF group （P 〉 0.05）. At 2, 4, and 6 mm away from the optic disc edge, there was no significant difference in retinal ganglion cell density between NRF and BDNF groups （P〉 0.05）. CONCLUSION： NRF provided protection to retinal ganglion cells in a rabbit model of acute hyper-intraocular pressure, Le., NRF enhanced the survival rate of retinal ganglion cells. The neuroprotective effect was similar to BDNF.

Erythropoietin upregulates growth associated protein-43 expression and promotes retinal ganglion cell axonal regeneration in vivo after optic nerve crush

In this study, we established a rat model of optic nerve crush to explore the effects of erythropoietin on retinal ganglion cell axonal regeneration. At 15 days after injury in erythropoietin treated rats, retinal ganglion cell densities in regions corresponding to the 1/6, 3/6 and 5/6 ratios of the retinal radius were significantly increased. In addition, the number of growth associated protein-43 positive axons was significantly increased at different distances （50, 250 and 500 pm） from the crush site after erythropoietin treatment. Erythropoietin significantly increased growth associated protein-43 protein levels in the retina after crush injury, as determined by westem blot and immunofluorescence analysis. These results demonstrate that erythropoietin protects injured retinal ganglion cells and promotes axonal regeneration.

Etomidate affects the anti-oxidant pathway to protect retinal ganglion cells after optic nerve transection

Our previous studies revealed that etomidate, a non-barbiturate intravenous anesthetic agent, has protective effects on retinal ganglion cells within 7 days after optic nerve transection. Whether this process is related to anti-oxidative stress is not clear. To reveal its mechanism, we established the optic nerve transection injury model by transecting 1 mm behind the left eyeball of adult male Sprague-Dawley rats. The rats received an intraperitoneal injection of etomidate(4 mg/kg) once per day for 7 days. The results showed that etomidate significantly enhanced the number of retinal ganglion cells retrogradely labeled with Fluorogold at 7 days after optic nerve transection. Etomidate also significantly reduced the levels of nitric oxide and malonaldehyde in the retina and increased the level of glutathione at 12 hours after optic nerve transection. Thus, etomidate can protect retinal ganglion cells after optic nerve transection in adult rats by activating an anti-oxidative stress response. The study was approved by the Animal Ethics Committee at Air Force Medical University, China(approval No. 20180305) on March 5, 2018.

PTEN knockdown with the Y444F mutant AAV2 vector promotes axonal regeneration in the adult optic nerve

The lack of axonal regeneration is the major cause of vision loss after optic nerve injury in adult mammals. Activating the PI3K/AKT/mTOR signaling pathway has been shown to enhance the intrinsic growth capacity of neurons and to facilitate axonal regeneration in the central nervous system after injury. The deletion of the mTOR negative regulator phosphatase and tensin homolog （PTEN） enhances regeneration of adult corticospinal neurons and ganglion cells. In the present study, we used a tyrosine-mutated （Y444F） AAV2 vector to efficiently express a short hairpin RNA （shRNA） for silencing PTEN expression in retinal ganglion cells. We evaluated cell survival and axonal regeneration in a rat model of optic nerve axotomy. The rats received an intravitreal injection of wildtype AAV2 or Y444F mutant AAV2 （both carrying shRNA to PTEN） 4 weeks before optic nerve axotomy. Compared with the wildtype AAV2 vector, the Y444F mutant AAV2 vector enhanced retinal ganglia cell survival and stimulated axonal regeneration to a greater extent 6 weeks after axotomy. Moreover,post-axotomy injection of the Y444F AAV2 vector expressing the shRNA to PTEN rescued ～19% of retinal ganglion cells and induced axons to regenerate near to the optic chiasm. Taken together, our results demonstrate that PTEN knockdown with the Y444F AAV2 vector promotes retinal ganglion cell survival and stimulates long-distance axonal regeneration after optic nerve axotomy. Therefore, the Y444F AAV2 vector might be a promising gene therapy tool for treating optic nerve injury.

The Achyranthes bidentata polypeptide k fraction enhances neuronal growth in vitro and promotes peripheral nerve regeneration after crush injury in vivo

We have previously shown that Achyranthes bidentata polypeptides （ABPP）, isolated from Achyranthes bidentata Blume （a medicinal herb）, exhibit neurotrophic and neuroprotective effects on the nervous system. To identify the major active component of ABPP, and thus optimize the use of ABPP, we used reverse-phase high performance liquid chromatography to separate ABPP. We obtained 12 fractions, among which the fraction of ABPPk demonstrated the strongest neuroactivity. Immunocytochemistry and western blot analysis showed that ABPPk promoted neurite growth in cultured dorsal root ganglion explant and dorsal root ganglion neurons, which might be associated with activation of Erk1/2. A combination of behavioral tests, electrophysiological assessment, and histomorphometric analysis indicated that ABPPk enhanced nerve regeneration and function restoration in a mouse model of crushed sciatic nerve. All the results suggest that ABPPk, as the key component of ABPP, can be used for peripheral nerve repair to yield better outcomes than ABPP.

Autogenous inside-out versus standard vein and skeletal muscle-combined grafting for facial nerve repair

BACKGROUND： In the repair of nerve defects, collapse of the venous wall, as a result of vein grafting alone, could impede nerve regeneration. Therefore, vein lumens filled with muscle and nerve segments have been used to bridge nerve defects. OBJECTIVE： To compare the effects of autogenous, inside-out, vein-skeletal, muscle-combined grafting versus standard, vein-skeletal, muscle-combined grafting for the repair of facial nerve defects. DESIGN, TIME AND SETTING： A randomized, controlled, neuroanatomical, animal study was performed at the Animal Experimental Center and Laboratories of the Capital Medical University Xuanwu Hospital and the Peking Union Medical College Hospital from September 2007 to October 2008.MATERIALS： A total of 10 healthy, male, New Zealand rabbits, aged 6 months, were randomly assigned to inside-out, vein-skeletal, muscle-combined grafting and standard, vein-skeletal, muscle-combined grafting groups, with 5 rabbits in each group. METHODS： A 20-mm gap in the buccal branch of the right facial nerve was made in each animal, which was respectively repaired with inside-out, vein-skeletal, muscle-combined grafts or standard vein-skeletal muscle-combined grafts.MAIN OUTCOME MEASURES： At 6 months after implantation, evoked maximal compound muscle action potentials were recorded on bilateral facial nerves using electromyogram. Myelinated nerve fibers of the regenerating nerves were quantified using myelin sheath osmic acid staining. RESULTS： There was no significant difference between the groups in terms of ratios of bilateral amplitude and latency of compound muscle action potential （P 〉 0.05）. Moreover, morphology of regenerating nerves and quantity of myelinated nerve fibers were similar between the groups （P 〉 0.05）. CONCLUTION： Compared with standard vein grafting, the inside-out vein grafting did not significantly improve nerve regeneration. Therefore, it is not necessary to utilize inside-out vein grafting for the repair of nerve defects, in particular with the combined use of autogenous vein and skeletal muscle grafts.

End-to-end and end-to-side neurorrhaphy between thick donor nerves and thin recipient nerves:an axon regeneration study in a rat model

During nerve reconstruction,nerves of different thicknesses are often sutured together using end-to-side neurorrhaphy and end-to-end neurorrhaphy techniques.In this study,the effect of the type of neurorrhaphy on the number and diameter of regenerated axon fibers was studied in a rat facial nerve repair model.An inflow-type end-to-side and end-to-end neurorrhaphy model with nerve stumps of different thicknesses（2：1 diameter ratio） was created in the facial nerve of 14 adult male Sprague-Dawley rats.After 6 and 12 weeks,nerve regeneration was evaluated in the rats using the following outcomes：total number of myelinated axons,average minor axis diameter of the myelinated axons in the central and peripheral sections,and axon regeneration rate.End-to-end neurorrhaphy resulted in a significantly greater number of regenerated myelinated axons and rate of regeneration after 6 weeks than end-to-side neurorrhaphy;however,no such differences were observed at 12 weeks.While the regenerated axons were thicker at 12 weeks than at 6 weeks,no significant differences in axon fiber thickness were detected between end-to-end and end-toside neurorrhaphy.Thus,end-to-end neurorrhaphy resulted in greater numbers of regenerated axons and increased axon regeneration rate during the early postoperative period.As rapid reinnervation is one of the most important factors influencing the restoration of target muscle function,we conclude that end-to-end neurorrhaphy is desirable when suturing thick nerves to thin nerves.

Current landscape in motoneuron regeneration and reconstruction for motor cranial nerve injuries

The intricate anatomy and physiology of cranial nerves have inspired clinicians and scientists to study their roles in the nervous system. Damage to motor cranial nerves may result from a variety of organic or iatrogenic insults and causes devastating functional impairment and disfigurement. Surgical innovations directed towards restoring function to injured motor cranial nerves and their associated organs have evolved to include nerve repair, grafting, substitution, and muscle transposition. In parallel with this progress, research on tissue-engineered constructs, development of bioelectrical interfaces, and modulation of the regenerative milieu through cellular, immunomodulatory, or neurotrophic mechanisms has proliferated to enhance the available repertoire of clinically applicable reconstructive options. Despite these advances, patients continue to suffer from functional limitations relating to inadequate cranial nerve regeneration, aberrant reinnervation, or incomplete recovery of neuromuscular function. These shortfalls have profound quality of life ramifications and provide an impetus to further elucidate mechanisms underlying cranial nerve denervation and to improve repair. In this review, we summarize the literature on reconstruction and regeneration of motor cranial nerves following various injury patterns. We focus on seven cranial nerves with predominantly efferent functions and highlight shared patterns of injuries and clinical manifestations. We also present an overview of the existing reconstructive approaches, from facial reanimation, laryngeal reinnervation, to variations of interposition nerve grafts for reconstruction. We discuss ongoing endeavors to promote nerve regeneration and to suppress aberrant reinnervation and the development of synkinesis. Insights from these studies will shed light on recent progress and new horizons in understanding the biomechanics of peripheral nerve neurobiology, with emphasis on promising strategies for optimizing neural regeneration and identifying future directions in the field of motor cranial neuron research.

Peripheral nerve injury induced changes in the spinal cord and strategies to counteract/enhance the changes to promote nerve regeneration

Peripheral nerve injury leads to morphological, molecular and gene expression changes in the spinal cord and dorsal root ganglia, some of which have positive impact on the survival of neurons and nerve regeneration, while the effect of others is the opposite. It is crucial to take prompt measures to capitalize on the positive effects of these reactions and counteract the negative impact after peripheral nerve injury at the level of spinal cord, especially for peripheral nerve injuries that are severe, located close to the cell body, involve long distance for axons to regrow and happen in immature individuals. Early nerve repair, exogenous supply of neurotrophic factors and Schwann cells can sustain the regeneration inductive environment and enhance the positive changes in neurons. Administration of neurotrophic factors, acetyl-L-carnitine, N-acetyl-cysteine, and N-methyl-D-aspartate receptor antagonist MK-801 can help counteract axotomy-induced neuronal loss and promote regeneration, which are all time-dependent. Sustaining and reactivation of Schwann cells after denervation provides another effective strategy. FK506 can be used to accelerate axonal regeneration of neurons, especially after chronic axotomy. Exploring the axotomy-induced changes after peripheral nerve injury and applying protective and promotional measures in the spinal cord which help to retain a positive functional status for neuron cell bodies will inevitably benefit regeneration of the peripheral nerve and improve functional outcomes.

Recent advances in the application of MXenes for neural tissue engineering and regeneration

Transition metal carbides and nitrides(MXenes)are crystal nanomaterials with a number of surface functional groups such as fluorine,hydroxyl,and oxygen,which can be used as carriers for proteins and drugs.MXenes have excellent biocompatibility,electrical conductivity,surface hydrophilicity,mechanical properties and easy surface modification.However,at present,the stability of most MXenes needs to be improved,and more synthesis methods need to be explored.MXenes are good substrates for nerve cell regeneration and nerve reconstruction,which have broad application prospects in the repair of nervous system injury.Regarding the application of MXenes in neuroscience,mainly at the cellular level,the long-term in vivo biosafety and effects also need to be further explored.This review focuses on the progress of using MXenes in nerve regeneration over the last few years;discussing preparation of MXenes and their biocompatibility with different cells as well as the regulation by MXenes of nerve cell regeneration in two-dimensional and three-dimensional environments in vitro.MXenes have great potential in regulating the proliferation,differentiation,and maturation of nerve cells and in promoting regeneration and recovery after nerve injury.In addition,this review also presents the main challenges during optimization processes,such as the preparation of stable MXenes and long-term in vivo biosafety,and further discusses future directions in neural tissue engineering.

Artificial facial nerve reflex restores eyelid closure following orbicularis oculi muscle denervation

To date, treatment of peripheral facial paralysis has focused on preservation of facial nerve integrity. However, with seriously damaged facial nerve cases, it is difficult to recover anatomical and functional integrity using present therapies. Therefore, the present study utilized artificial facial nerve reflex to obtain orbicularis oculi muscle （OOM） electromyography signals on the uninjured side through the use of implanted recording electrodes. The implanted electrical chips analyzed facial muscle motion on the uninjured side and triggered an electrical stimulator to emit current pulses, which resulted in stimulation of injured OOM contraction and maintained bilateral symmetry and consistency. Following signal recognition, extraction, and computer analysis, electromyography signals in the uninjured OOM resulted in complete eyelid closure, which was consistent with the voltage threshold for eye closure. These findings suggested that artificial facial nerve reflex through the use of implanted microelectronics in unilateral peripheral facial paralysis could restore eyelid closure following orbicularis oculi muscle denervation.

Brain-derived neurotrophic factor expression in dorsal root ganglion neurons in response to reanastomosis of the distal stoma after nerve grafting

Studies have shown that retreatment of the distal stoma after nerve grafting can stimulate nerve regeneration. The present study attempted to verify the effects of reanastomosis of the distal stoma, after nerve grafting, on nerve regeneration by assessing brain-derived neurotrophic factor expression in 2-month-old rats. Results showed that brain-derived neurotrophic factor expression in L2-4 dorsal root ganglia began to increase 3 days after autologous nerve grafting post sciatic nerve injury, peaked at 14 days, decreased at 28 days, and reached similar levels to the sham-surgery group at 56 days. Brain-derived neurotrophic factor expression in L2-4 dorsal root ganglia began to increase 3 days after reanastomosis of the distal stoma, 59 days after autologous nerve grafting post sciatic nerve injury, significantly increased at 63 days, peaked at 70 days, and gradually decreased thereafter, but remained higher compared with the sham-surgery group up to 112 days. The results of this study indicate that reanastomosis of the distal stoma after orthotopic nerve grafting stimulated brain-derived neurotrophic factor expression in L2.4 dorsal root ganglia.

Negative regulation of gamma-aminobutyric acid type A receptor on free calcium ion levels following facial nerve injury

Previous studies have demonstrated that muscarinic, and nicotinic receptors increase free Ca2＋ levels in the facial nerve nucleus via various channels following facial nerve injury. However, intracellular Ca2＋ overload can trigger either necrotic or apoptotic cell death. Gamma-aminobutyric acid （GABA）, an important inhibitory neurotransmitter in the central nervous system, exists in the facial nerve nucleus. It is assumed that GABA negatively regulates free Ca2＋ levels in the facial nerve nucleus. The present study investigated GABA type A （GABAA） receptor expression in the facial nerve nucleus in a rat model of facial nerve injury using immunohistochemistry and laser confocal microscopy, as well as the regulatory effects of GABAA receptor on nicotinic receptor response following facial nerve injury. Subunits α1, α3, α5, β1, β2, δ, and γ3 of GABAA receptors were expressed in the facial nerve nucleus following facial nerve injury. In addition, GABAA receptor expression significantly inhibited the increase in nicotinic receptor-mediated free Ca2＋ levels in the facial nerve nucleus following facial nerve injury in a concentration-dependent fashion. These results suggest that GABAA receptors exhibit negative effects on nicotinic receptor responses following facial nerve injury.

Repairing whole facial nerve defects with xenogeneic acellular nerve grafts in rhesus monkeys

Acellular nerve allografts conducted via chemical extraction have achieved satisfactory results in bridging whole facial nerve defects clinically,both in terms of branching a single trunk and in connecting multiple branches of an extratemporal segment.However,in the clinical treatment of facial nerve defects,allogeneic donors are limited.In this experiment,we exposed the left trunk and multiple branches of the extratemporal segment in six rhesus monkeys and dissected a gap of 25 mm to construct a monkey model of a whole left nerve defect.Six monkeys were randomly assigned to an autograft group or a xenogeneic acellular nerve graft group.In the autograft group,the 25-mm whole facial nerve defect was immediately bridged using an autogenous ipsilateral great auricular nerve,and in the xenogeneic acellular nerve graft group,this was done using a xenogeneic acellular nerve graft with trunk-branches.Examinations of facial symmetry,nerve-muscle electrophysiology,retrograde transport of labeled neuronal tracers,and morphology of the regenerated nerve and target muscle at 8 months postoperatively showed that the faces of the monkey appeared to be symmetrical in the static state and slightly asymmetrical during facial movement,and that they could actively close their eyelids completely.The degree of recovery from facial paralysis reached House-Brackmann grade II in both groups.Compound muscle action potentials were recorded and orbicularis oris muscles responded to electro-stimuli on the surgical side in each monkey.Fluoro Gold-labeled neurons could be detected in the facial nuclei on the injured side.Immunohistochemical staining showed abundant neurofilament-200-positive axons and soluble protein-100-positive Schwann cells in the regenerated nerves.A large number of mid-graft myelinated axons were observed via methylene blue staining and a transmission electron microscope.Taken together,our data indicate that xenogeneic acellular nerve grafts from minipigs are safe and effective for repairing whole facial nerve defects in rhesus monkeys,with an effect similar to that of autologous nerve transplantation.Thus,a xenogeneic acellular nerve graft may be a suitable choice for bridging a whole facial nerve defect if no other method is available.The study was approved by the Laboratory Animal Management Committee and the Ethics Review Committee of the Affiliated Wuxi No.2 People's Hospital of Nanjing Medical University,China(approval No.2018-D-1)on March 15,2018.

Amniotic membrane covering for facial nerve repair

Amniotic membranes have been widely used in ophthalmology and skin injury repair because of their anti-inflammatory properties. In this study, we measured therapeutic efficacy and determined if amniotic membranes could be used for facial nerve repair. The facial nerves of eight rats were dissected and end-to-end anastomosis was performed. Amniotic membranes were covered on the anastomosis sites in four rats. Electromyography results showed that, at the end of the 3rd and 8th weeks after amniotic membrane covering, the latency values of the facial nerves covered by amniotic membranes were significantly shortened and the amplitude values were significantly increased. Compared with simple facial nerve anastomosis, after histopathological examination, facial nerve anastomosed with amniotic membrane showed better continuity, milder inflammatory reactions, and more satisfactory nerve conduction. These findings suggest that amniotic membrane covering has great potential in facial nerve repair.