Transcriptome analysis of molecular mechanisms underlying facial nerve injury repair in rats

Although the transcriptional alterations inside the facial nucleus after facial nerve injury have been well studied,the gene expression changes in the facial nerve trunk after injury are still unknown.In this study,we established an adult rat model of facial nerve crush injury by compressing the right lateral extracranial nerve trunk.Transcriptome sequencing,differential gene expression analysis,and cluster analysis of the injured facial nerve trunk were performed,and 39 intersecting genes with significant variance in expression were identified.Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway analyses of the 39 intersecting genes revealed that these genes are mostly involved in leukocyte cell-cell adhesion and phagocytosis and have essential roles in regulating nerve repair.Quantitative real-time polymerase chain reaction assays were used to validate the expression of pivotal genes.Finally,nine pivotal genes that contribute to facial nerve recovery were identified,including Arhgap30,Akr1b8,C5ar1,Csf2ra,Dock2,Hcls1,Inpp5d,Sla,and Spi1.Primary Schwann cells were isolated from the sciatic nerve of neonatal rats.After knocking down Akr1b8 in Schwann cells with an Akr1b8-specific small interfering RNA plasmid,expression levels of monocyte chemoattractant protein-1 and interleukin-6 were decreased,while cell proliferation and migration were not obviously altered.These findings suggest that Akr1b8 likely regulates the interaction between Schwann cells and macrophages through regulation of cytokine expression to promote facial nerve regeneration.This study is the first to reveal a transcriptome change in the facial nerve trunk after facial nerve injury,thereby revealing the potential mechanism underlying repair of facial nerve injury.This study was approved by the Animal Ethics Committee of Nantong University,China in 2018(approval No.S20180923-007).

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.

Agmatine promotes expression of brain-derived neurotrophic factor in brainstem facial nucleus in the rat facial nerve injury model

BACKGROUND： Studies have shown that agmatine can reduce inhibition of neuronal regeneration by increasing cyclic adenosine monophosphate and brain-derived neurotrophic factor （BDNF） in the hippocampus of morphine-dependent rats. The hypothesis that agmatine exerts similar effects on facial nerve injury deserves further analysis. OBJECTIVE： To study the effects of peritoneal agmatine injection on BDNF levels in the rat brainstem after facial nerve injury. DESIGN, TIME AND SETTING： A controlled animal experiment was performed at the Department of Otolaryngology-Head and Neck Surgery at the Second Affiliated Hospital, Chongqing University of Medical Sciences （Chongqing, China）, between October and December in 2007. MATERIALS： Twenty-four male Sprague-Dawley rats were randomly divided into a control, a lesion, and an agmatine treatment group, with eight rats in each group. Bilateral facial nerve anastomosis was induced in the lesion and agmatine treatment groups, while the control group remained untreated. A rat BDNF Enzyme-linked immunosorbent assay kit was used to measure BDNF levels in the brainstem facial nucleus. METHODS： Starting on the day of lesion, the agmatine group received a peritoneal injection of 100 mg/kg agmatine, once per day, for a week, whereas rats in the lesion group received saline injections. MAIN OUTCOME MEASURES： BDNF levels in the brainstem containing facial nucleus were measured by ELISA. RESULTS： Twenty-four rats were included in the final analysis without any loss. Two weeks after lesion, BDNF levels were significantly higher in the lesion group than in the control group （P 〈 0.01）. A significant increase was noted in the agmatine group compared to the lesion group （P 〈 0.01）. CONCLUSION： Agmatine can substantially increase BDNF levels in the rat brainstem after facial nerve injury.

Application of a venous conduit as a stent for repairing rabbit facial nerve injury

BACKGROUND： Recently, many investigators have tried to use natural biomaterials, such as, artery, vein, decalcified bone, etc., as conduits for nerve repair. However, immunological rejection of conduits made of natural biomaterials limits their application. Therefore, it is essential to identify more suitable types of biomaterials. OBJECTIVE： To observe the characteristics of a bioengineering processing method using venous conduit as a stent for repairing facial nerve injury. DESIGN： A controlled observational experiment. SETTING： Animal Laboratories of the Third Hospital Affiliated to Sun Yat-sen University and the 157 Hospital. MATERIALS： Thirty-three male New Zealand rabbits of pure breed, weighing 1.5 to 2.0 kg, were provided by Medical Experimental Animal Room of Sun Yat-sen University. The protocol was carried out in accordance with animal ethics guidelines for the use and care of animals. Venous conduits and autogenous nerves were transplanted into the left and right cheeks, respectively. Eleven animals were chosen for anatomical observations at 5, 10 and 15 weeks after surgery. METHODS： This experiment was carried out in the Animal Laboratories of the Third Hospital Affdiated to Sun Yat-sen University and the 157 Hospital between May and November 2006. After animals were anesthetized, 15 mm of retromandibular vein was harvested for preparing a venous conduit. Approximately 3 cm of low buccal branch of facial nerve was exposed. A segment of 1.2 cm nerve was resected from the middle, and a gap of 1.5 cm formed due to bilateral retraction. The prepared venous conduit of 1.5 cm was sutured to the outer membrane of the severed ends of the nerve. Muscle and skin were sutured layer by layer. Using the same above-mentioned method, the low buccal branch of right autogenous facial nerve was resected, and the left facial nerve segment from the same animal was transplanted using end-to-end neurorrhaphy for control. MAIN OUTCOME MEASURES： （1）Post-operatively, food intake, vibrissae activity and wound healing of each animal were observed daily. （2） Animals were anesthetized at 5, 10 and 15 weeks after operation for observing the structural change of the venous conduit, the appearance of regenerated nerve, and the relationship between conduit and peripheral muscle tissue. （3） The action potential and latency of bilateral nerves of animals were measured by electrophysiologic examination, and nerve conduction velocity was calculated. （4）Neural myelination and neurite growth were observed by histological staining using an optical microscope. RESULTS： Thirty-three New Zealand rabbits were involved in the final analysis. （1）Immediately following the operation, vibrissae activity and orbicularis otis muscle activity of the upper lip on venous conduit side were more prominent, and their amplitudes of movement were larger as compared with autogenous nerve side. （2） At postoperative 10 weeks, by visual inspection, we found that on the venous conduit side, the venous conduit exhibited membrane structure which encased regenerated nerve. Regenerated nerve adhered to the muscle edge of orbicularis oris muscle. Muscle and nerve could be separated with a forceps. The muscle of musculus orbicularis oris of rabbit was darker and thicker as compared with autogenous nerve side. After the venous conduit was longitudinally split, the regenerated nerve and nerves at two the severed ends were connected together. When compared with postoperative 5 weeks, the connected nerve was thickened, texture was tough and its middle part was thicker than its two ends. On the autogenous nerve side, the regenerated nerve stem was enwrapped by scar tissue. It was bulky and adhered to peripheral muscle. Its neural profile structure was unclear. The two stomas were obviously enlarged. （3）At postoperative 10 weeks and 15 weeks, nerve action potentials could be elicited from both the venous conduit and autologous nerve side. The mean nerve conduction velocity on the venous conduit side was greater than that of the autologous nerve side. （4）At postoperative 10 weeks, using histochemical staining, it was found that in the venous conduit, regenerated medullated nerve fibers were densely distributed, with well split facial nerve structure, while on the autologous nerve side, nerve fibers were sparsely scattered, with immature medullated nerve structure. CONCLUSION： Biological natural venous conduit processed by bioengineering technology overcomes the tissue inflammatory reactions and connective tissue reactions caused by natural biomaterials. It is more conducive to promote neural regeneration and functional recovery than autologous nerve transplantation.

Acute pathological changes of facial nucleus and expressions of postsynaptic density protein-95 following facial nerve injury of varying severity A semi-quantitative analysis

BACKGROUND： Previous studies have demonstrated that postsynaptic density protein-95 （PSD-95） is widely distributed in the central nervous system and is related to the development of the CNS and sensory signal transmission as well as acute or chronic nerve cell death following ischemic brain injury. OBJECTIVE： To semi-quantitatively determine the pathological changes of apoptotic facial neurons and the expression of PSD-95 in the facial nucleus following facial nerve injury of varying extents using immunohistochemical staining methods. DESIGN, TIME AND SETTING： Randomized, controlled animal experiments were performed in the Ultrasonic Institute of the Second Affiliated Hospital of Chongqing University of Medical Sciences from September to December 2007. MATERIALS： Sixty-five healthy, adult, Sprague-Dawley （SD） rats, both male and female, were used for this study. Rabbit anti-rat PSD-95 polyclonal antibody was purchased from Beijing Biosynthesis Biotechnology Co., Ltd. METHODS： SD rats were randomly assigned into a control group with five rats and three injured groups with 20 rats per group. Exposure, clamp and cut for bilateral facial nerve trunks were performed in the rats of the injury groups, and no injury was inflicted on the rats of the control group. MAIN OUTCOME MEASURES; The brainstems of all the rats were excised on days 1, 3, 7, and 14 post injury, and then the facial nuclei were stained with hematoxylin-eosin to observe any pathological changes due to apoptosis in facial neurons. PSD-95 expression in facial nuclei was detected by immunohistochemistry and the number of PSD-95 positive cells was counted under a light microscope. RESULTS： The expression of PSD-95 in the facial nucleus and morphology of the facial neuron within the exposure group had no obvious changes at various points in time tested （P 〉 0.05）. However, the expressions of PSD-95 in the facial nucleus of the clamp group and cut group increased on day 1 post injury （P 〈 0.05）, and showed further increase on day 7 post injury （P 〈 0.01 ）. This did not decrease until day 14 post injury. Facial neuron apoptosis was detected on day 3 post injury and this was even more obvious on day 7 and was maintained to day 14 post injury. The number of cells expressing PSD-95 and displaying severe degrees of facial neuron apoptosis were as follows： cut group 〉 clamp group 〉 exposure group. CONCLUSION： The apoptotic extent of facial neurons and the expression of PSD-95 in apoptotic facial neurons increased with the degree of aggravation of injured severity of facial nerve.

Effects of gamma-aminobutyric acid receptors on muscarinic receptor-mediated free calcium ion levels in the facial nucleus following facial nerve injury

Muscarinic receptors and nicotine receptors can increase free calcium ion levels in the facial nucleus via different channels following facial nerve injury. In addition, γ-aminobutyric acid A （GABAA） receptors have been shown to negatively regulate free calcium ion levels in the facial nucleus by inhibiting nicotine receptors. The present study investigated the influence of GABAA, γ-aminobutyric acid B （GABAB） and C （GABAc） receptors on muscarinic receptors in rats with facial nerve injury by confocal laser microscopy. GABAA and GABAB receptors exhibited significant dose-dependent inhibitory effects on increased muscarinic receptor-mediated free calcium ion levels following facial nerve injury. Results showed that GABAA and GABAB receptors negatively regulate muscarinic receptor effects and interplay with cholinergic receptors to regulate free calcium ion levels for facial neural regeneration.

Electroacupuncture Promotes Functional Recovery after Facial Nerve Injury in Rats by Regulating Autophagy via GDNF and PI3K/m TOR Signaling Pathway

Objective:To explore the mechanism of electroacupuncture(EA) in promoting recovery of the facial function with the involvement of autophagy,glial cell line-derived neurotrophic factor(GDNF),and phosphatidylinositol-3-kinase(PI3K)/mammalian target of rapamycin(mTOR) signaling pathway.Methods:Seventy-two male Sprague-Dawley rats were randomly allocated into the control,sham-operated,facial nerve injury(FNI),EA,EA+3-methyladenine(3-MA),and EA+GDNF antagonist groups using a random number table,with 12 rats in each group.An FNI rat model was established with facial nerve crushing method.EA intervention was conducted at Dicang(ST 4),Jiache(ST 6),Yifeng(SJ 17),and Hegu(LI 4) acupoints for 2 weeks.The Simone’s 10-Point Scale was utilized to monitor the recovery of facial function.The histopathological evaluation of facial nerves was performed using hematoxylin-eosin(HE) staining.The levels of Beclin-1,light chain 3(LC3),and P62 were detected by immunohistochemistry(IHC),immunofluorescence,and reverse transcriptionpolymerase chain reaction,respectively.Additionally,IHC was also used to detect the levels of GDNF,Rai,PI3K,and mTOR.Results:The facial functional scores were significantly increased in the EA group than the FNI group(P<0.05 or P<0.01).HE staining showed nerve axons and myelin sheaths,which were destroyed immediately after the injury,were recovered with EA treatment.The expressions of Beclin-1 and LC3 were significantly elevated and the expression of P62 was markedly reduced in FNI rats(P<0.01);however,EA treatment reversed these abnormal changes(P<0.01).Meanwhile,EA stimulation significantly increased the levels of GDNF,Rai,PI3K,and mTOR(P<0.01).After exogenous administration with autophagy inhibitor 3-MA or GDNF antagonist,the repair effect of EA on facial function was attenuated(P<0.05 or P<0.01).Conclusions:EA could promote the recovery of facial function and repair the facial nerve damages in a rat model of FNI.EA may exert this neuroreparative effect through mediating the release of GDNF,activating the PI3K/mTOR signaling pathway,and further regulating the autophagy of facial nerves.

Muscarinic receptor-mediated calcium changes in a rat model of facial nerve nucleus injury

The muscarinic receptor modulates intracellular free calcium ion levels in the facial nerve nucleus via different channels. In the present study, muscarinic receptor-mediated free calcium ions levels were detected by confocal laser microscopy in the facial nerve nucleus following facial nerve injury in rats. There was no significant difference in muscarinic receptor expression at the affected facial nerve nucleus compared with expression prior to injury, but muscarinic receptor-mediated free calcium ion levels increased in the affected side following facial nerve injury （P 〈 0.01）. At day 30 after facial nerve injury, 50 pmol/L muscarinic-mediated free calcium ion levels were significantly inhibited at the affected facial nerve nucleus in calcium-free artificial cerebrospinal fluid, and the change range was 82% of artificial cerebrospinal fluid （P 〈 0.05）. These results suggest that increased free calcium ion concentrations are achieved by intracellular calcium ion release, and that the transmembrane flow of calcium ions is also involved in this process.

Nicotine alpha 4 beta 2 receptor-mediated free calcium in an animal model of facial nucleus injury

Previous studies have demonstrated that the cholinergic system, via nicotinic receptors, regulates intracellular free calcium levels in the facial nucleus under normal physiological conditions. However, the regulation of nicotinic receptors on free calcium levels following facial nerve injury remains unclear. In the present study, an animal model of facial nerve injury was established, and changes in nicotinic receptor expression following facial nerve injury in rats were detected using reverse transcription polymerase chain reaction. Nicotinic receptor-mediated changes of free calcium levels following facial nucleus injury were determined by laser confocal microscopy. Results showed no significant difference in nicotinic receptor expression between the normal group and the affected facial nerve nucleus. The nicotinic receptor a4132 subtype increased free calcium levels following facial nerve injury by promoting calcium transmembrane influx, and L-type voltage-gated calcium channel-mediated influx of calcium ions played an important role in promoting calcium transmembrane influx. The nicotinic receptor-mediated increase of free calcium levels following facial nerve injury provides an important mechanism for the repair of facial nerve injury.

Surgical Management of Traumatic Facial Paralysis:A Case Review Study

Objective To evaluate efficacy of surgical treatment in traumatic facial paralysis.Methods:Thirty-three cases were reviewed,including temporal bone fracture and iatrogenic facial nerve injury.All the patients were treated with various surgical methods according to their pathogeny.Results The mean percentage facial function improvement (House-Brackmann GradeⅠ-Ⅱ) was 86% in temporal bone fracture and function was improved after proper operation to iatrogenic facial nerve injury.Conclusions Patients with traumatic facial paralysis receive proved outcomes itreaed with proper surgical methods according to their particular condition of nerve injury.

The surgical management of frontal branch of the facial nerve injuries

Aim:The frontal branch of the facial nerve is particularly vulnerable to traumatic injury or during surgery.While the larger branches of the facial nerve,such as the buccal branch,are more easily identifiable and amenable to repair,the repair of the frontal branch is not common due to its complex branching pattern and smaller size.The description of the surgical approach to repair the frontal branch of the facial nerve is limited in the literature.In this study,we aim to explore the outcomes of patients who underwent frontal branch facial nerve repair in our centre.Method:In a retrospective case review at a single,tertiary Plastic Surgery centre,we performed frontal branch repair for eight patients(n=8)who sustained complete or partial division of the frontal branch of the facial nerves.These patients were followed up postoperatively and assessed with the Sunnybrook Facial Grading System.Results:Using super microsurgical techniques,primary nerve coaptations,fascicular nerve flaps,and direct neurotisations were performed.All eight patients(100%)demonstrated improvements in terms of resting brow symmetry.There was a significant improvement in brow and frontalis function following surgical repair of the frontal branch,with 87.5%(seven patients)demonstrating improvement in forehead movement.Conclusion:In this case series,we demonstrated that the repair of the frontal branch of the facial nerve is relevant,with reasonably good functional outcomes.Repair of the frontal branch of the facial nerve should ideally be done as early as possible following the injury.Nevertheless,delayed repair may still be beneficial within 18 months after the injury.