Facial Regeneration Research Articles

Inhibition of nitric oxide production enhances the activity of facial nerve tubulin polymerization and the ability of tau to promote microtubule assembly after neurorrhaphy

We previously reported that inhibition of nitric oxide (NO) production promotes rat reconnected facial nerve regeneration. However, the underlying mechanism is obscure. Microtubule assembly is known to be essential to axon regeneration; nevertheless, tubulins and microtubule-associated proteins (MAPs) have been demonstrated as targets for NO and peroxynitrite. Thus, we hypothesized that NO and/or peroxynitrite may affect facial nerve regeneration via influencing on microtubule assembly. First, tubulins and tau (a MAP) were extracted from facial nerves of normal rats, treated with NO donor or peroxynitrite, and processed for microtubule assembly assay. We found that peroxynitrite, DEA NONOate, and Angeli's salt reduced the tubulin polymerization activity to a greater extent than GSNO, SIN-1, and SNAP. Additionally, SIN-1, peroxynitrite, and Angeli's salt impaired the ability of tau to promote microtubule assembly. Next, nitrosative stress biomarkers 3-nitrotyrosine (3-NT) and S-nitrosylated cysteine (SNO-Cys) were immunolabeled in facial nerves. Both biomarkers were highly upregulated in proximal and distal stumps of reconnected facial nerves at 3 days and 1 week after neurorrhaphy. Notably, the expression of 3-NT was greatly reduced at 2 weeks, whereas that of SNO-Cys was maintained. Conversely, inhibition of NO production with L-NAME prevented the upregulation of SNO-Cys. Further, we used tubulins and tau extracted from facial nerves of sham-operated, nerve suture + vehicle treatment, and nerve suture + L-NAME treatment rats to perform microtubule assembly assay. We found that L-NAME treatment enhanced polymerization activity of tubulins and ability of tau to promote microtubule assembly. It is noteworthy that α-tubulin plays a more important role than β-tubulin since the activity of microtubule assembly using α-tubulin extracted from L-NAME-treated rats was greatly elevated, whereas that using β-tubulin extracted from L-NAME-treated rats was not. Overall, our findings support that inhibition of NO production reduces nitrosative stress, and may thus facilitate microtubule assembly and facial nerve regeneration.

Facial nerve regeneration with bioabsorbable collagen conduits filled with collagen filaments: An experimental study.

IntroductionA bioabsorbable collagen conduit (Renerve™) filled with collagen filaments is currently approved as an artificial nerve conduit in Japan and is mainly used for connecting and repairing peripheral nerves after traumatic nerve injury. However, there are few reports on its applications for reconstructing and repairing the facial nerve. The present study evaluated the efficacy of the conduit on promoting nerve regeneration in a murine model with a nerve defect at the buccal branch of the facial nerve.MethodsUnder inhalational anesthesia and microscopic guidance, the buccal branch of the left facial nerve in an 8-week-old Lewis rat was exposed, and a 7 mm gap was created in the nerve. The gap was then connected with either the nerve conduits (NC group) or an autologous nerve graft (the autograft group). At 13 weeks after the procedure, we compared the histological and physiological regenerations in the both groups.ResultsWe found compound muscle action potential amplitude is significantly larger in the autograft group (2.8 ± 1.4 mV) than in NC group (1.3 ± 0.5 mV) (p < 0.05). The number of myelinated fibers of the autograft group was higher (3634 ± 1645) than that of NC group (1112 ± 490) (p < 0.01). The fiber diameter of the autograft group (4.8 ± 1.9 μm) was larger than that of NC group (3.8 ± 1.4 μm) (p < 0.05). The myelin thickness of the autograft group was thicker than that of NC group (0.6 ± 0.3 μm vs. 0.4 ± 0.1 μm) (p < 0.05). G-ratio of the autograft group (0.74 ± 0.19) was lower than that of NC group (0.79 ± 0.10) (p < 0.05).ConclusionThis study demonstrated the efficacy of collagen nerve conduit for facial nerve reconstruction following nerve injury. However, the effectiveness of the conduit on the promotion of nerve regeneration was inferior to that of the autograft.

Intratympanic Insulin-like Growth Factor-1 Administration Via the Otic Bulla in a Severe Facial Paralysis Model.

We investigated the treatment effect of intratympanic insulin-like growth factor-1 (IGF-1) on severe facial paralysis in guinea pigs. The use of regenerative medicine involving growth factors has been reported in the treatment of peripheral nerve diseases. IGF-1 plays a crucial role in nerve regeneration. We performed the following procedures on guinea pigs. In the normal group (n = 7), no procedure was performed. In the saline (n = 7) and IGF-1 (n = 7) groups, facial paralysis was induced by freezing of the facial canal. Subsequently, in the saline and IGF-1 groups, a gelatin hydrogel impregnated with 100 μL saline and 400 μg/100 μL IGF-1, respectively, was placed in the facial canal. Facial nerve functions were evaluated using three test batteries: facial movement observation, electrophysiological testing, and histological assessment. At 10 weeks postoperatively, the facial movement scores for the IGF-1 group were improved compared to those in the saline group. The conductive velocity was significantly faster in the IGF-1 group than in the saline group. There was a significant between-group difference in the nerve fiber number and myelin thickness. Intratympanic IGF-1 administration improved facial nerve regeneration. This novel method could provide prompt ambulatory regenerative treatment and reduce the incidence of poor recovery in patients with severe facial paralysis.

Clinical Studies and Pre-clinical Animal Models on Facial Nerve Preservation, Reconstruction, and Regeneration Following Cerebellopontine Angle Tumor Surgery–A Systematic Review and Future Perspectives

Background and purpose: Tumorous lesions developing in the cerebellopontine angle (CPA) get into close contact with the 1st (cisternal) and 2nd (meatal) intra-arachnoidal portion of the facial nerve (FN). When surgical damage occurs, commonly known reconstruction strategies are often associated with poor functional recovery. This article aims to provide a systematic overview for translational research by establishing the current evidence on available clinical studies and experimental models reporting on intracranial FN injury.Methods: A systematic literature search of several databases (PubMed, EMBASE, Medline) was performed prior to July 2020. Suitable articles were selected based on predefined eligibility criteria following the Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) guidelines. Included clinical studies were reviewed and categorized according to the pathology and surgical resection strategy, and experimental studies according to the animal. For anatomical study purposes, perfusion-fixed adult New Zealand white rabbits were used for radiological high-resolution imaging and anatomical dissection of the CPA and periotic skull base.Results: One hundred forty four out of 166 included publications were clinical studies reporting on FN outcomes after CPA-tumor surgery in 19,136 patients. During CPA-tumor surgery, the specific vulnerability of the intracranial FN to stretching and compression more likely leads to neurapraxia or axonotmesis than neurotmesis. Severe FN palsy was reported in 7 to 15 % after vestibular schwannoma surgery, and 6% following the resection of CPA-meningioma. Twenty-two papers reported on experimental studies, out of which only 6 specifically used intracranial FN injury in a rodent (n = 4) or non-rodent model (n = 2). Rats and rabbits offer a feasible model for manipulation of the FN in the CPA, the latter was further confirmed in our study covering the radiological and anatomical analysis of perfusion fixed periotic bones.Conclusion: The particular anatomical and physiological features of the intracranial FN warrant a distinguishment of experimental models for intracranial FN injuries. New Zealand White rabbits might be a very cost-effective and valuable option to test new experimental approaches for intracranial FN regeneration. Flexible and bioactive biomaterials, commonly used in skull base surgery, endowed with trophic and topographical functions, should address the specific needs of intracranial FN injuries.

Efficacy of platelet-rich fibrin and tacrolimus on facial nerve regeneration: an animal study

This study was performed to investigate the effect of platelet-rich fibrin membrane (PRFM), alone and with topical tacrolimus application, on regeneration of the crushed facial nerve (FN). Thirty healthy 7-week-old albino rats were used. The left FN was damaged by crushing in all rats. Three random groups of rats were formed: group 1, untreated; group 2, treated with PRFM; group 3, treated with PRFM plus topical tacrolimus. Functional recovery and histological and immunohistochemical evaluations were performed 4 and 8 weeks later. Anti-S100 was used to detect myelin sheath. At 4 weeks, blinking reflex recovery was more rapid in group 3 than in groups 2 and 1 (4.30 ± 0.48, 3.40 ± 0.52, and 2.20 ± 0.42, respectively); the difference was statistically significant (P = 0.001). Histologically, group 3 showed more apparent normal FN structures than the other groups. Immunohistochemical caspase-3 evaluation of the axon area revealed a significant difference between group 2 (PRFM alone; 8.67 ± 0.029) and group 3 (PRFM plus topical tacrolimus; 4.42 ± 0.028) (P = 0.001). Group 3 showed the greatest positive staining in the myelin sheath. Based on the results of this animal study, clinical studies should be performed to determine whether the combination of PRF and tacrolimus also improves the outcome of nerve regeneration in humans.

Tissue-engineered nerve guides with mesenchymal stem cells in the facial nerve regeneration

Nerve guides with mesenchymal stem cells have been investigated in the rat facial nerve defect model to promote peripheral nerve regeneration and shorten recovery time to improve patients' quality of life. A 7-mm facial nerve gap experimental rat model is frequently employed in facial nerve regeneration studies. Facial nerve regeneration with nerve guides is evaluated by (1) assessing myelinated fiber counts using toluidine blue staining, (2) immunohistological analysis, (3) determining the g-ratio (axon diameter/total outer diameter) of regenerated nerve on transmission electron microscopic images, (4) retrograde nerve tracing in the facial nucleus, (5) electrophysiological evaluations using compound muscle action potential, and (6) functional evaluations using rat facial palsy scores. Dental pulp and adipose-derived stem cells, easily harvested using a minimally invasive procedure, possess characteristics of mesenchymal tissue lineages and can differentiate into Schwann-like cells. Cultured dental pulp-derived cells can produce neurotrophic factors, including nerve growth factor, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor. These neurotrophic factors promote peripheral nerve regeneration and afford protection against facial motor neuron death. Moreover, artificial nerve guides can maneuver axonal regrowth, and dental pulp-derived cells and adipose-derived Schwann cells may supply neurotrophic factors, promoting axonal regeneration. In the present review, the authors discuss facial nerve regeneration using nerve guides with mesenchymal stem cells.

Potential Therapeutic Strategies and Substances for Facial Nerve Regeneration Based on Preclinical Studies.

Despite advances in microsurgical technology and an improved understanding of nerve regeneration, obtaining satisfactory results after facial nerve injury remains a difficult clinical problem. Among existing peripheral nerve regeneration studies, relatively few have focused on the facial nerve, particularly how experimental studies of the facial nerve using animal models play an essential role in understanding functional outcomes and how such studies can lead to improved axon regeneration after nerve injury. The purpose of this article is to review current perspectives on strategies for applying potential therapeutic methods for facial nerve regeneration. To this end, we searched Embase, PubMed, and the Cochrane library using keywords, and after applying exclusion criteria, obtained a total of 31 qualifying experimental studies. We then summarize the fundamental experimental studies on facial nerve regeneration, highlighting recent bioengineering studies employing various strategies for supporting facial nerve regeneration, including nerve conduits with stem cells, neurotrophic factors, and/or other therapeutics. Our summary of the methods and results of these previous reports reveal a common feature among studies, showing that various neurotrophic factors arising from injured nerves contribute to a microenvironment that plays an important role in functional recovery. In most cases, histological examinations showed that this microenvironmental influence increased axonal diameter as well as myelination thickness. Such an analysis of available research on facial nerve injury and regeneration represents the first step toward future therapeutic strategies.

Effects of chitosan and platelet-rich plasma on facial nerve regeneration in an animal model.

There is still no widely-accepted local agent proven to be effective in nerve regeneration. We aimed to investigate the effects of chitosan gel and platelet-rich plasma MATERIALS AND METHODS: Electrophysiological measurements were performed before and immediately after injury. The injured nerves were covered with spongostan impregnated with the following agents: Group 1 (Control Group): Saline at a dose of 50 µl; Group 2: Chitosan (CHT) at a dose of 50 µl; Group 3: PRP at a dose of 50 ml; and Group 4: a solution of CHT with PRP (1:1). The final measurements were performed after 3 weeks and the injured nerve of each rat was removed. There were statistically-significant differences between the groups regarding the measurements of the after-treatment values of stimulus threshold (p < 0.05). The best improvement in electrophysiological measurement and histopathological evaluation was found in Group 4 (CHT-PRP). Chitosan gel has a positive effect on nerve healing and applying it along with PRP can enhance the effect of chitosan.

Contralateral Facial Botulinum Toxin Injection in Cases with Acute Facial Paralysis May Improve the Functional Recovery: Where We Stand and the Future Direction.

BACKGROUNDFacial nerve (FN) impacts the function of the facial musculature by creating muscle tone at rest as well as the muscles’ voluntary and involuntary contractions. Temporary or permanent loss of FN function could be due to different etiologic factors. Acute facial paralysis (FP) could be significantly stressful for the patient and the family and apart from supportive measures management options are quite restricted. While botulinum toxin (BTX) injection in the FP setting has been used mostly to address the compensatory hyperkinesia in the non-paralyzed side of the face, there are evidence to suggest contralateral injection of the non-paralyzed face with BTX may improve/enhance the recovery time of the FP in cases where the FP has a reversible cause. While further studies are underway, using the current evidence as discussed could potentially justify the current usage of contralateral BTX injection and biofeedback exercises in the setting of the temporary FP specialty due to lack of effective alternative management options.

Increased Expression of Toll-like Receptor 2 mRNA after Facial Nerve Injury in Rat

Abstract Objectives: The aim of this study was to determine whether TLRs mRNA is expressed in the distal facial nerve after facial nerve injury. Methods: The adult male Sprague-Dawley with a body weight of 200–250g underwent injury of unilateral facial nerve. Crush or cutting injury was given at the midpoint between the facial nerve trunk and the facial nerve branch. The whisker movement of vibrissae muscle was examined 4 and 14 days after facial nerve injury. The normal facial nerve on the left side and the damaged facial nerve on the right side were taken under the inhalation anesthesia and real-time polymerase chain reaction was performed. Results: In the whisker movement of vibrissae muscle, the crush group and the cutting group showed worse scores on the 14th day than the 4th scores in each group (p&amp;lt;0.05). On the 4th day of injury, the expression of TLR 7 mRNA was highest in the crush group, and on the 14th day of injury, the expression of TLR 7 mRNA was highest in the cutting group. On the 14th day of injury, the expression of TLR 2 mRNA was significantly higher in the cutting group than in the control group (p&amp;lt;0.05), on the 4th day of injury, the expression of TLR 9, 13 mRNA was significantly lower in the crush and cutting groups than in the control group (p&amp;lt;0.05). Conclusions: The expression of TLR 2 mRNA in the distal facial nerve after facial nerve injury in the cutting group was significantly higher than that in the control group, but the expressions of TLR 9 and 13 mRNA in the crush and cutting groups were significantly low. Therefore, TLR mRNA may be involved in facial nerve damage and regeneration.

Facial nerve regeneration using silicone conduits filled with ammonia-functionalized graphene oxide and frankincense-embedded hydrogel

BackgroundSilicone tube (ST) conduits have been accepted as a therapeutic alternative to direct nerve suturing in the treatment of nerve injuries; however, the search for optimal adjuncts to maximize the outcomes is still ongoing. Frankincense (Fr) and graphene oxide (GO) have both been cited as neuroregenerative compounds in the literature. This study assesses the efficacy of these materials using a ST conduit in a rat facial nerve motor neuron axotomy model, distal to the stylomastoid foramen.MethodsAmmonia-functionalized graphene oxide (NH2-GO) and/or Fr extract were embedded in a collagen-chitosan hydrogel and were injected inside a ST. The ST was inserted in the gap between the axotomized nerve stumps. Return of function in eye closure, blinking reflex, and vibrissae movements were assessed and compared to control groups through 30 days following axotomy. To assess the histological properties of regenerated nerves, biopsies were harvested distal to the axotomy site and were visualized through light and fluorescence microscopy using LFB and anti-MBP marker, respectively.ResultsThere was no significant difference in behavioral test results between groups. Histological analysis of the nerve sections revealed increased number of regenerating axons and mean axon diameter in NH2-GO group and decreased myelin surface area in Fr group. Using both NH2-GO and Fr resulted in increased number of regenerated axons and myelin thickness compared to the hydrogel group.ConclusionsThe findings suggest a synergistic effect of the substances above in axon regrowth, notably in myelin regeneration, where Fr supposedly decreases myelin synthesis.

An electrophysiological evaluation method for the ovine facial nerve.

IntroductionLarge-animal models such as sheep for facial nerve regeneration research have not yet been established because of the lack of methods for assessing the electrophysiological function of regenerated nerves. In this study, we developed a percutaneous measurement method for the evoked compound muscle action potential (CMAP) of the facial nerve in sheep.MethodsSix 3-year-old castrated male Corriedale sheep were used in this study. Under general anesthesia, an anatomical exploration was performed to identify the course of the buccal branch of the facial nerve and its innervating muscles on one side, followed by the application of surface stimulating electrodes to the contralateral side of the face along the course of the buccal branch of the facial nerve to obtain CMAP measurements of the nasolabial levator muscle.ResultsPercutaneous CMAP measurements of the nasolabial levator muscle could be obtained in all animals by placing stimulating electrodes 1 cm apart on the line coinciding with the course of the buccal branch of the facial nerve revealed by the preceding anatomical exploration. Mean values for electrophysiological parameters were amplitude 4.7 ± 0.7 mV, duration 2.1 ± 0.6 ms, and latency 3.6 ± 0.4 ms.ConclusionWe have established a percutaneous measurement method for CMAP of the buccal branch of the facial nerve in sheep. This method is expected to be very useful in future studies of facial nerve regeneration for long nerve defects in sheep.

Is Decorin a Promising New Agent for Facial Nerve Regeneration? An Experimental Study

Objective: The aim of this study was to investigate the effects of systemic administration of decorin (DC) on facial nerve (FN) regeneration. Methods: A total of 32 female albino Wistar rats were divided into 4 groups: control (C) group: no bilateral FN neurorrhaphy (B-FNN), no DC application, sham-operated group: B-FNN without DC application, DC group: DC application without B-FNN, and B-FNN + DC group: B-FNN and DC application. Nerve conduction studies were performed before and after skin incisions at 1st, 3rd, 5th, and 7th weeks in all groups. The amplitude and latency of compound muscle action potentials were recorded. FN samples were obtained and were investigated under light microscopy and immunohistochemical staining. The nerve and axon diameter, number of axons, H score, Schwann cell proliferation, and myelin and axonal degeneration were recorded quantitatively. Results: In the sham group, the 3rd and 5th postoperative week, amplitude values were significantly lower than those of the B-FNN + DC group (p < 0.05). Nerve diameters were found to be significantly larger in the sham, DC, and B-FNN + DC groups than in the C group (p < 0.05). The number of axons, the axon diameter, and the H scores were found to be significantly higher in the B-FNN + DC group than in the sham group (p < 0.05). The Schwann cell proliferation, myelin degeneration, and axonal degeneration scores were significantly lower in the B-FNN + DC group than in the sham group (p < 0.05). Conclusion: Electrophysiological and histopathological evaluation revealed the potential benefits provided by DC. This agent may increase FN regeneration.

Nerve guidance conduit promoted peripheral nerve regeneration in rats.

Nerve growth factor (NGF) is important for peripheral nerve regeneration. However, its short half-life and rapid diffusion in body fluids limit its clinical efficacy. Collagen has favorable biocompatibility and biodegradability, and weak immunogenicity. Because it possesses an NGF binding domain, we cross-linked heparin to collagen tubes to construct nerve guidance conduits for delivering NGF. The conduits were implanted to bridge a facial nerve defect in rats. Histological and functional analyses were performed to assess the effect of the nerve guidance conduit on facial nerve regeneration. Heparin enhanced the binding of NGF to collagen while retaining its bioactivity. Also, the nerve guidance conduit significantly promoted axonal growth and Schwan cell proliferation at 12weeks after surgery. The nerve regeneration and functional recovery outcomes using the nerve guidance conduit were similar to those of autologous nerve grafting. Therefore, the nerve guidance conduit may promote safer nerve regeneration.

Contemporary techniques for nerve transfer in facial reanimation

Nerve transfer procedures have the potential to restore innervation and function to the native facial musculature. This review summarizes the existing literature on facial nerve injury, regeneration, and reinnervation techniques with a focus on nerve transfer and its various options. Utilizing nerve transfer as early as possible, and ideally during the first 12 months of paralysis, is recommended. Prolonged paralysis is frequently not amenable to nerve transfer. The masseteric nerve provides excellent smile restoration after coapation to midfacial nerve branches with minimal morbidity. Several modifications to the hypoglossal nerve transfer have been described to limit its morbidity in speech and swallowing. The cross facial nerve, while appealing and able to achieve a true spontaneous smile, has limitations in terms of axonal load, time to reinnervation, unpredictable outcomes, and utility in older patients, who have less regenerative potential. Finally, there are exciting new developments in the field, combining reanimation techniques to harness advantages of various donor nerves, and research in peripheral nerve regeneration.

A personalized nutrition plan based on genetic profile improves outcomes of facial regeneration with Platelet-Rich Fibrin liquid matrices

Aim: The importance of nutrition in the prevention of skin aging has been shown by large observational studies. However, there are no studies assessing dietary changes as adjunct procedures to aesthetic interventions. The objective of this study was to assess whether a personalized nutritional plan conveys additional benefits to platelet-rich fibrin (PRF) facial regeneration.

Impact of fetal brain tissue derived mesenchymal stem cell and fibrin glue on facial nerve crash injury

Background/aimTo evaluate the clinical and histopathological effects of fetal brain tissue derived mesenchymal stem cells (FBTMSC) and fibrin glue (FG) on the facial nerve (FN) regeneration in rats with traumatic FN injury.Materials and methodsTwenty-eight Sprague Dawley rats were included in the study and divided into 4 groups. Traumatic FN injury (FP) was created by a surgical clamp compression to the main trunk of left FN in all groups. In the control group (group 1) no treatment was applied, in group 2 (FBTMSC group) 2 × 106 FBTMSC was injected, in group 3 (FG group) only FG was applied, in group 4 (FBTMSC and FG groups) both FBTMSC and FG were applied to the injured section of the nerve. The FN functions were evaluated clinically, immediately after the procedure and at 3rd, 5th, and 8th weeks postoperatively. The FNs of all subjects were excised after the 8th week; then the rats were sacrificed. The presence of stem cells in the injured zone was assessed using bromo-deoxyuridine (BrdU), and apoptosis was determined by the TUNEL method.ResultsAfter the damage, total FP was observed in all subjects. Statistically significant functional improvement was observed in group 4 compared to all other groups (P < 0.005). TUNEL-positive cell count was statistically significantly higher in the control group than the other groups (P < 0.001). TUNEL-positive cell count was statistically significantly lower in group 4 than the other groups. The proportion of BrdU-stained cells in group 4 (5%) was higher than group 2 (2%).ConclusionClinically and histopathologically FBTMSC applied with FG may play a promising role as a regenerative treatment in posttraumatic FP.

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).

Effects of titanium prepared platelet rich fibrin on facial nerve regeneration: an experimental study

IntroductionFacial nerve damage is a condition that causes functional, psychological, and cosmetic problems; and treatment methods need to be improved. ObjectiveWe investigated the efficacy of titanium-prepared platelet-rich fibrin as a healing enhancer at the region of transection of the facial nerve. MethodsTwenty-seven New Zealand male rabbits were used in this study, divided into three experimental groups. Group 1, the sham group (n=7); Group 2, the suture group (n=10); and Group 3, the suture+T-PRF group (n=10). In Group 1, the facial nerve trunk was dissected, and no additional surgical intervention was performed. For Group 2, a transection was made to the facial nerve trunk and the nerve endings were sutured together. In Group 3, nerve endings were sutured after transection, and a titanium-prepared platelet-rich fibrin membrane was wrapped in a tube around the damaged area. All animals were followed up weekly for the presence of corneal reflex, whisker movement and low ears. Bilateral facial electromyography was performed both preoperatively and postoperatively at the 1st, 3rd, 5th, 7th, 10th weeks. Tissue samples obtained at the 10th week were histopathologically examined, and intra-group and inter-group comparisons were performed. ResultsSubjects in Group showed improvement in whisker movement and ear drop one week earlier than Group 2. In Group 3, the nerve stimulation threshold required to trigger the compound muscle action potential had returned to values similar to the preoperative control values (11.31±2.16V) by 5 weeks postoperatively (12.51±3.97V), (p=0.249). ConclusionTitanium-prepared platelet-rich fibrin administration contributed to partial nerve healing both on a functional and an electrophysiological level.

Prosaposin and its receptors GRP37 and GPR37L1 show increased immunoreactivity in the facial nucleus following facial nerve transection.

Neurotrophic factor prosaposin (PS) is a precursor for saposins A, B, C, and D, which are activators for specific sphingolipid hydrolases in lysosomes. Both saposins and PS are widely contained in various tissues. The brain, skeletal muscle, and heart cells predominantly contain unprocessed PS rather than saposins. PS and PS-derived peptides stimulate neuritogenesis and increase choline acetyltransferase activity in neuroblastoma cells and prevent programmed cell death in neurons. We previously detected increases in PS immunoactivity and its mRNA in the rat facial nucleus following facial nerve transection. PS mRNA expression increased not only in facial motoneurons, but also in microglia during facial nerve regeneration. In the present study, we examined the changes in immunoreactivity of the PS receptors GPR37 and GPR37L1 in the rat facial nucleus following facial nerve transection. Following facial nerve transection, many small Iba1- and glial fibrillary acidic protein (GFAP)-positive cells with strong GPR37L1 immunoreactivity, including microglia and astrocytes, were observed predominately on the operated side. These results indicate that GPR37 mainly works in neurons, whereas GPR37L1 is predominant in microglia or astrocytes, and suggest that increased PS in damaged neurons stimulates microglia or astrocytes via PS receptor GPR37L1 to produce neurotrophic factors for neuronal recovery.