Neural plasticity after peripheral nerve injury and regeneration

Schwann Cells as Orchestrators of Nerve Repair: Implications for Tissue Regeneration and Pathologies

Peripheral nerves exist in a stable state in adulthood providing a rapid bidirectional signaling system to control tissue structure and function. However, following injury, peripheral nerves can regenerate much more effectively than those of the central nervous system (CNS). This multicellular process is coordinated by peripheral glia, in particular Schwann cells, which have multiple roles in stimulating and nurturing the regrowth of damaged axons back to their targets. Aside from the repair of damaged nerves themselves, nerve regenerative processes have been linked to the repair of other tissues and de novo innervation appears important in establishing an environment conducive for the development and spread of tumors. In contrast, defects in these processes are linked to neuropathies, aging, and pain. In this review, we focus on the role of peripheral glia, especially Schwann cells, in multiple aspects of nerve regeneration and discuss how these findings may be relevant for pathologies associated with these processes.

Real time monitoring peripheral nerve function with ICG and BDA-ICG by NIR-II fluorescence imaging

Neuroanatomical tract tracers are important for studying axoplasmic transport and the complex interconnections of the nervous system. Though traditional fluorescent tracers are widely used, they have several prominent drawbacks when imaging, including low resolutions and low tissue penetrations and inability to be supervised dynamically within a long peripheral nerve during the long term. Here, we explored the potential of ICG as a neural tracer for axoplasmic transport and for the first time demonstrated that ICG could be used to detect transport function within peripheral nerve by near-infrared region II (NIR-II) imaging. On basis of this finding, a novel bi-directional neural tracer biotinylated dextran amine-indocyanine green (BDA-ICG) was prepared and characterized with better long-term stability and higher nerve-to-background ratio than ICG in vivo, and successfully imaged the injured peripheral nerve from the healthy one within 24 h. Our results show that BDA-ICG are promising neural tracers and clinically available dyes with NIR-II emission tail characteristics as ICG.

Netrin-1 as A neural guidance protein in development and reinnervation of the larynx

Neural guidance proteins participate in motor neuron migration, axonal projection, and muscle fiber innervation during development. One of the guidance proteins that participates in axonal pathfinding is Netrin-1. Despite the well-known role of Netrin-1 in embryogenesis of central nervous tissue, it is still unclear how the expression of this guidance protein contributes to primary innervation of the periphery, as well as reinnervation. This is especially true in the larynx where Netrin-1 is upregulated within the intrinsic laryngeal muscles after nerve injury and where blocking of Netrin-1 alters the pattern of reinnervation of the intrinsic laryngeal muscles. Despite this consistent finding, it is unknown how Netrin-1 expression contributes to guidance of the axons towards the larynx. Improved knowledge of Netrin-1's role in nerve regeneration and reinnervation post-injury in comparison to its role in primary innervation during embryological development, may provide insights in the search for therapeutics to treat nerve injury. This paper reviews the known functions of Netrin-1 during the formation of the central nervous system and during cranial nerve primary innervation. It also describes the role of Netrin-1 in the formation of the larynx and during recurrent laryngeal reinnervation following nerve injury in the adult.

Expression of ChAT, Iba-1, and nNOS in the Central Nervous System following Facial Nerve Injury

Facial nerve injury can cause significant functional impairment, impacting both the peripheral and central nervous systems. The present study evaluated changes in facial motor function, numbers of cholinergic neurons and microglia, and nNOS levels in the facial nucleus of the central nervous system (CNS) following peripheral facial nerve injury. Facial nerve function, as determined by eyeblink and whisker-movement reflexes, was evaluated at baseline and 1, 2, 3, 4, 8, and 12 weeks after inducing facial nerve injury through compression or axotomy. The expression of choline acetyltransferase (ChAT), ionized calcium-binding adaptor molecule 1 (Iba-1), and neuronal nitric oxide synthase (nNOS) in the facial nucleus of the CNS was analyzed 2, 4, and 12 weeks after peripheral facial nerve injury. Compression-induced facial nerve injury was found to lead to temporary facial motor impairment, whereas axotomy resulted in persistent impairment. Moreover, both compression and axotomy reduced ChAT expression and increased Iba-1 and nNOS expression in the facial nucleus, indicating upregulation of an inflammatory response and neurodegeneration. These results indicate that, compared with compression-induced injury, axotomy-induced facial nerve injury results in greater facial motor dysfunction and more persistent microglial and nitric oxide activation in the facial nucleus of the CNS.

Trigeminal somatosensation in the temporomandibular joint and associated disorders

The temporomandibular joint (TMJ) consists of bone, cartilage, ligaments, and associated masticatory muscles and tendons that coordinate to enable mastication in mammals. The TMJ is innervated by the trigeminal nerve (CNV), containing axons of motor and somatosensory neurons. Somatosensation includes touch, temperature, proprioception, and pain that enables mammals to recognize and react to stimuli for survival. The somatosensory innervation of the TMJ remains poorly defined. Disorders of the TMJ (TMD) are of diverse etiology and presentation. Some known symptoms associated with TMD include facial, shoulder, or neck pain, jaw popping or clicking, headaches, toothaches, and tinnitus. Acute or chronic pain in TMD stems from the activation of somatosensory nociceptors. Treatment of TMD may involve over- the-counter and prescription medication, nonsurgical treatments, and surgical treatments. In many cases, treatment achieves only a temporary relief of symptoms including pain. We suggest that defining the sensory innervation of the temporomandibular joint and its associated tissues with a specific focus on the contribution of peripheral innervation to the development of chronic pain could provide insights into the origins of joint pain and facilitate the development of improved analgesics and treatments for TMD.

Rosmarinic acid Ameliorates neuronal regeneration in the bridging silicone rubber conduits of the sciatic nerve in taxol-treated rats

Background and aim

Taxol modulates local inflammatory conditions in peripheral nerves, which may impair their regeneration and recovery when injured. This study aimed to determine the effects of rosmarinic acid (RA, a polyphenol constituent of many culinary herbs) on the regeneration of the sciatic nerves in the bridging conduits.

Experimental procedure

In the cell study, RA decreased nuclear factor (NF)-κB activity induced by taxol in a dose dependency. In the animal model, taxol-treated rats were divided into 3 groups (n = 10/group): taxol (2 mg/kg body weight for 4 times) and taxol + RA (3 times/week for 4 weeks at 20 and 40 mg/kg body weight) groups. Macrophage infiltration, calcitonin gene-related peptide (CGRP) expression levels, neuronal connectivity, animal behavior, and neuronal electrophysiology were evaluated.

Results and conclusion

At the end of 4 weeks, macrophage density, CGRP expression level, and axon number significantly increased in the RA group compared with the taxol group. The RA administration unaffected heat, cold plate licking latencies, and motor coordination. Moreover, the 40 mg/kg RA group had significantly larger nerve conduction velocity and less latency compared to the taxol group. This study suggested that RA could ameliorate local inflammatory conditions to augment the recovery of regenerating nerves by accelerating their regrowth and improving electrophysiological function in taxol-treated peripheral nerve injury repaired with the silicone rubber conduit.

Animal models in peripheral nerve transection studies: a systematic review on study design and outcomes assessment

Aim: Peripheral nerve injury regeneration studies using animal models are crucial to different pre-clinical therapeutic approaches efficacy evaluation whatever the surgical technique explored. Materials & methods: A 944 articles systematic review on 'peripheral nerve injury in animal models' over the last 9 years was carried out. Results: It was found that 91% used rodents, and only 9% employed large animals. Different nerves are studied, with generated gaps (10,78 mm) and methods applied for regeneration evaluation uniformed. Sciatic nerve was the most used (88%), followed by median and facial nerves (2.6%), significantly different. Conclusion: There has not been a significant scale-up of the in vivo testing to large animal models (anatomically/physiologically closer to humans), allowing an improvement in translational medicine for clinical cases.

Knowledge, attitudes, and perceptions of physical therapists towards conventional physical therapy-across-sectional study

Background

Conventional physical therapy (CPT) is widely used in clinical practice and known to contribute beneficially to patient's health conditions but remains loosely defined. Research has shown inconsistency in the definition and utilization of CPT among physical therapists in clinical and research settings, limiting its generalisability and reproducibility. Therefore, this study evaluates physical therapists' knowledge, attitudes, and perceptions toward CPT.

Methods

A cross-sectional study using a self-administered questionnaire containing 36 questions was distributed among 238 licensed physical therapists. Descriptive and inferential statistics were used to measure the physical therapists' knowledge, attitudes, and perceptions towards CPT.

Results

Physical therapists showed limited knowledge of CPT in rehabilitation (4.09±1.698, 51%). However, the knowledge scores were significantly associated with age (P=0.002), educational levels (P=0.006), and years of work experience (P=0.001). Nevertheless, physical therapists showed an overall positive attitude towards CPT and perceived it as essential to rehabilitation.

Conclusion

Most physical therapists have low knowledge about CPT but positive attitudes and perceptions. Therefore, customized medical education is necessary to incorporate CPT theories and applications into physical therapists' rehabilitation programs.

Alteration of serotonin release response in the central nucleus of the amygdala to noxious and non-noxious mechanical stimulation in a neuropathic pain model rat

Previously, we found that serotonin (5-HT) release in the central nucleus of the amygdala (CeA) of anesthetized rats decreases in response to innocuous stroking of the skin, irrespective of stimulus laterality, but increases in response to noxious pinching applied to a hindlimb contralateral to the 5-HT measurement site. The aim of the present study was to determine whether intra-CeA 5-HT release responses to cutaneous stimulation were altered in an animal model of neuropathic pain induced by ligation of the left L5 spinal nerve. In anesthetized neuropathic pain model rats, stroking of the left hindlimb increased 5-HT release in the CeA, whereas stroking of the right hindlimb decreased it. Meanwhile, pinching of the left hindlimb increased intra-CeA 5-HT release irrespective of stimulus laterality. In conclusion, the present study demonstrated that intra-CeA 5-HT release responses to cutaneous stimulation are altered in an animal model of neuropathic pain.

Contralateral thalamocortical connectivity is related to postural control in the uninvolved limb of older adults with history of ankle sprain

BACKGROUND

Sensorimotor brain connectivity is often overlooked when determining relationships between postural control and motor performance following musculoskeletal injury. Thalamocortical brain connectivity is of particular interest as it represents the temporal synchrony of functionally and anatomically linked brain regions. Importantly, adults over the age of 60 are especially vulnerable to musculoskeletal injury due to age-related declines in postural control and brain connectivity.

RESEARCH QUESTION

Is there a relationship between thalamocortical connectivity and static postural control in older adults with a history of LAS?

METHODS

Data were analyzed from twenty older adults (mean age = 67.0 ± 4.3 yrs; 13 females) with a history of LAS. The sensorimotor network (SMN) was identified from resting-state MRI data, and a priori thalamic and postcentral gyri regions of interest were selected in order to determine left and right hemisphere thalamocortical connectivity. Balance was assessed for the involved and non-involved limbs via center of pressure velocity (COPV) in the medial-lateral (ML) and anterior-posterior (AP) directions.

RESULTS

Contralateral thalamocortical connectivity was significantly associated with COPV_ML COPV_ML (r = -0.474, P = 0.05) and COPV_AP (r = -0.622, P = 0.008) in the non-involved limb. No significant association was observed between involved limb balance and contralateral thalamocortical connectivity (COPV_ML: r = -0.08, P = 0.77; COPV_AP: r = 0.12, P = 0.63).

SIGNIFICANCE

A significant relationship between thalamocortical connectivity and static postural control was observed in the non-involved, but not the involved limb in older adults with a history of LAS. Findings suggest that thalamocortical connectivity may lead to or be the product of LAS.

TsMS combined with EA promotes functional recovery and axonal regeneration via mediating the miR-539-5p/Sema3A/PlexinA1 signalling axis in sciatic nerve-injured rats

Enhancing axonal regeneration is one of the most important processes in treating nerve injuries. Both magnetic and electrical stimulation have the effect of promoting nerve axon regeneration. But few study has investigated the effects of trans-spinal magnetic stimulation (TsMS) combined with electroacupuncture (EA) on nerve regeneration in rats with sciatic nerve injury. In this study, we compared the improvement of neurological function in rats with sciatic nerve crush injuries after 4 weeks of different interventions (EA, TsMS, or TsMS combined with EA). We further explored the morphological and molecular biological alterations following sciatic nerve injury by HE, Masson, RT-PCR, western blotting, immunofluorescence staining and small RNA transcriptome sequencing. The results showed that TsMS combined with EA treatment significantly promoted axonal regeneration, increased the survival rate of neurons, and suppressed denervation atrophy of the gastrocnemius muscle. Subsequent experiments suggested that the combination treatment may play an active role by mediating the miR-539-5p/Sema3A/PlexinA1 signaling axis.

Preparation of bilayer tissue-engineered polyurethane/poly-L-lactic acid nerve conduits and their in vitro characterization for use in peripheral nerve regeneration

BACKGROUND

Due to loss of peripheral nerve structure and/or function resulting from trauma, accidents, and other causes, peripheral nerve injuries continue to be a major clinical problem. These injuries can cause partial or total loss of sensory, motor, and autonomic capabilities as well as neuropathic pain. PNI affects between 13 and 23 out of every 100,000 people annually in developed countries. Regeneration of damaged nerves and restoration of function after peripheral nerve injury remain significant therapeutic challenges. Although autologous nerve graft transplantation is a viable therapy option in several clinical conditions, donor site morbidity and a lack of donor tissue often hinder full functional recovery. Biomimetic conduits used in tissue engineering to encourage and direct peripheral nerve regeneration by providing a suitable microenvironment for nerve ingrowth are only one example of the cutting-edge methods made possible by this field. Many innate extracellular matrix (ECM) structures of different tissues can be successfully mimicked by nanofibrous scaffolds. Nanofibrous scaffolds can closely mimic the surface structure and morphology of native ECMs of many tissues.

METHODS

In this study, we have produced bilayer nanofibrous nerve conduit based on poly-lactic acid/polyurethane/multiwall carbon nanotube (PLA/PU/MWCNT), for application as composite scaffolds for static nerve tissue engineering. The contact angle was indicated to show the hydrophilicity properties of electrospun nanofibers. The SEM images were analyzed to determine the fiber's diameters, scaffold morphology, and endometrial stem cell adhesion. Moreover, MTT assay and DAPI staining were used to show the viability and proliferation of endometrial stem cells.

RESULTS

The constructed bilayer PLA/PU/MWCNT scaffolds demonstrated the capacity to support cell attachment, and the vitality of samples was assessed using SEM, MTT assay, and DAPI staining technique.

CONCLUSIONS

According to an in vitro study, electrospun bilayer PLA/PU/MWCNT scaffolds can encourage the adhesion and proliferation of human endometrial stem cells (hEnSCs) and create the ideal environment for increasing cell survival.

The involvement of Neuregulin-1 in the process of facial nerve injury repair through the utilization of dental pulp stem cells

BACKGROUND

Facial nerve injury often results in poor prognosis due to the challenging process of nerve regeneration. Neuregulin-1, a human calmodulin, is under investigation in this study for its impact on the reparative capabilities of Dental Pulp Stem Cells (DPSCs) in facial nerve injury.

METHODS

Lentivirus was used to transfect and construct Neuregulin-1 overexpressed DPSCs. Various techniques assessed the effects of Neuregulin-1: osteogenic induction, lipid induction, Reverse Transcription Polymerase Chain Reaction, Western Blot, Cell Counting Kit-8 assay, wound healing, immunofluorescence, Phalloidin staining, nerve stem action potential, Hematoxylin-eosin staining, transmission electron microscopy, and immunohistochemistry.

RESULTS

Neuregulin-1 effectively enhanced the proliferation, migration, and cytoskeletal rearrangement of DPSCs, while simultaneously suppressing the expression of Ras homolog gene family member A (RhoA) and Microfilament actin (F-actin). These changes facilitated the neural differentiation of DPSCs. Additionally, in vivo experiments showed that Neuregulin-1 expedited the restoration of action potential in the facial nerve trunk, increased the thickness of the myelin sheath, and stimulated axon regeneration.

CONCLUSION

Neuregulin-1 has the capability to facilitate the repair of facial nerve injuries by promoting the regenerative capacity of DPSCs. Thus, Neuregulin-1 is a significant potential gene in the reparative processes of nerve damage.

VEGF and Neuronal Survival

Vascular endothelial growth factor (VEGF) is well known for its angiogenic activity, but recent evidence has revealed a neuroprotective action of this factor on injured or diseased neurons. In the present review, we summarize the most relevant findings that have contributed to establish a link between VEGF deficiency and neuronal degeneration. At issue, 1) mutant mice with reduced levels of VEGF show adult-onset muscle weakness and motoneuron degeneration resembling amyotrophic lateral sclerosis (ALS), 2) administration of VEGF to different animal models of motoneuron degeneration improves motor performance and ameliorates motoneuronal degeneration, and 3) there is an association between low plasmatic levels of VEGF and human ALS. Altogether, the results presented in this review highlight VEGF as an essential motoneuron neurotrophic factor endowed with promising therapeutic potential for the treatment of motoneuron disorders.

Functional Brain Changes Following Burn Injury: A Narrative Review

BACKGROUND

Burn injuries cause significant motor and sensory dysfunctions that can negatively impact burn survivors' quality of life. The underlying mechanisms of these burn-induced dysfunctions have primarily been associated with damage to the peripheral neural architecture, however, evidence points to a systemic influence of burn injury. Central nervous system (CNS) reorganizations due to inflammation, afferent dysfunction, and pain could contribute to persistent motor and sensory dysfunction in burn survivors. Recent evidence shows that the capacity for neuroplasticity is associated with self-reported functional recovery in burn survivors.

OBJECTIVE

This review first outlines motor and sensory dysfunctions following burn injury and critically examines recent literature investigating the mechanisms mediating CNS reorganization following burn injury. The review then provides recommendations for future research and interventions targeting the CNS such as non-invasive brain stimulation to improve functional recovery.

CONCLUSIONS

Directing focus to the CNS following burn injury, alongside the development of non-invasive methods to induce functionally beneficial neuroplasticity in the CNS, could advance treatments and transform clinical practice to improve quality of life in burn survivors.

Exploration of sensations evoked during electrical stimulation of the median nerve at the wrist level

Objective.Nerve rehabilitation following nerve injury or surgery at the wrist level is a lengthy process during which not only peripheral nerves regrow towards receptors and muscles, but also the brain undergoes plastic changes. As a result, at the time when nerves reach their targets, the brain might have already allocated some of the areas within the somatosensory cortex that originally processed hand signals to some other regions of the body. The aim of this study is to show that it is possible to evoke a variety of somatotopic sensations related to the hand while stimulating proximally to the injury, therefore, providing the brain with the relevant inputs from the hand regions affected by the nerve damage.Approach.This study included electrical stimulation of 28 able-bodied participants where an electrode that acted as a cathode was placed above the Median nerve at the wrist level. The parameters of electrical stimulation, amplitude, frequency, and pulse shape, were modulated within predefined ranges to evaluate their influence on the evoked sensations.Main results.Using this methodology, the participants reported a wide variety of somatotopic sensations from the hand regions distal to the stimulation electrode.Significance.Furthermore, to propose an accelerated stimulation tuning procedure that could be implemented in a clinical protocol and/or standalone device for providing meaningful sensations to the somatosensory cortex during nerve regeneration, we trained machine-learning techniques using the gathered data to predict the location/area, naturalness, and sensation type of the evoked sensations following different stimulation patterns.

Tuina therapy promotes behavioral improvement and brain plasticity in rats with peripheral nerve injury and repair

INTRODUCTION

Tuina is currently one of the popular complementary and alternative methods of rehabilitation therapy. Tuina can improve patients' pain and mobility function. However, the underlying physiological mechanism remains largely unknown, which might limit its further popularization in clinical practice. The aim of this study is to explore the short-term and long-term changes in brain functional activity following Tuina intervention for peripheral nerve injury repair.

METHODS

A total of 16 rats were equally divided into the intervention group and the control group. Rats in the intervention group received Tuina therapy applying on the gastrocnemius muscle of the right side for 4 months following sciatic nerve transection and immediate repair, while the control group received nerve transection and repair only. The block-design functional magnetic resonance imaging scan was applied in both groups at 1 and 4 months after the surgery. During the scan, both the injured and intact hindpaw was electrically stimulated according to a "boxcar" paradigm.

RESULTS

When stimulating the intact hindpaw, the intervention group exhibited significantly lower activation in the somatosensory area, limbic/paralimbic areas, pain-regulation areas, and basal ganglia compared to the control group, with only the prefrontal area showing higher activation. After 4 months of sciatic nerve injury, the control group exhibited decreased motor cortex activity compared to the activity observed at 1 month, and the intervention group demonstrated stronger bilateral motor cortex activity compared to the control group.

CONCLUSION

Tuina therapy on the gastrocnemius muscle of rats with sciatic nerve injury can effectively alleviate pain and maintain the motor function of the affected limb. In addition, Tuina therapy reduced the activation level of pain-related brain regions and inhibited the decreased activity of the motor cortex caused by nerve injury, reflecting the impact of peripheral stimulation on brain plasticity.

Effect of Metformin on the Functional and Electrophysiological Recovery of Crush Injury-Induced Facial Nerve Paralysis in Diabetic Rats

The impact of metformin on the rat facial nerve following crush injury has only occasionally been documented to date. The purpose of the current investigation was to use functional and electrophysiological evaluations to investigate the effects of metformin administration on recovery following crush injury to the rat facial nerve. The rats were randomly divided into four groups: the nonDM/PBS group (n = 4), the nonDM/metformin group (n = 4), the DM/PBS group (n = 4), and the DM/metformin group (n = 4). Diabetes was generated by an intraperitoneal injection of streptozotocin. Facial nerve paralysis was induced by a crush injury 7 days after diabetes induction. The blood glucose levels of the DM/PBS and DM/metformin groups were maintained at over 300 mg/dL, whereas the blood glucose levels of the nonDM/PBS and nonDM/metformin groups were maintained at less than 150 mg/dL. There was no significant difference between the two nonDM groups. In comparison to the PBS group, the metformin group's recurrence of vibrissa fibrillation occurred noticeably sooner over time. The nonDM/metformin group showed the highest recovery rate in the second, third, and fourth weeks post-crush, respectively. The threshold of action potential 4 weeks after crush injury showed that the nonDM/metformin group had a significantly lower mean threshold of MAP compared to other groups. The short-term effect of metformin on the recovery of facial nerve blood flow (FNBF) was significantly increased compared to the DM/PBS group. However, there was no significant difference in FNBF between the nonDM/metformin and nonDM/PBS groups. A diabetic condition promoted a delay in FN regeneration. Metformin is able to accelerate functional recovery in diabetic or nondiabetic FN-injured rats. Further studies using a morphometric or molecular approach are planned to understand the pharmacologic mechanism of metformin.

Advances in Nerve Injury Models on a Chip

Regeneration and functional recovery of the damaged nerve are challenging due to the need for effective therapeutic drugs, biomaterials, and approaches. The poor outcome of the treatment of nerve injury stems from the incomplete understanding of axonal biology and interactions between neurons and the surrounding environment, such as glial cells and extracellular matrix. Microfluidic devices, in combination with various injury techniques, have been applied to test biological hypotheses in nerve injury and nerve regeneration. The microfluidic devices provide multiple advantages over the in vitro cell culture on a petri dish and in vivo animal models because a specific part of the neuronal environment can be manipulated using physical and chemical interventions. In addition, single-cell behavior and interactions between neurons and glial cells can be visualized and quantified on microfluidic platforms. In this article, current in vitro nerve injury models on a chip that mimics in vivo axonal injuries and the regeneration process of axons are summarized. The microfluidic-based nerve injury models could enhance the understanding of the physiological and pathophysiological mechanisms of nerve tissues and simultaneously serve as powerful drug and biomaterial screening platforms.

Multi-animal-model study reveals mutations in neural plasticity and nociception genes linked to excessive alcohol drinking

BACKGROUND

The basis for familial alcohol use disorder (AUD) remains an enigma due to various biological and societal confounds. The present study used three of the most adopted and documented rat models, combining the alcohol-preferring/non-alcohol-preferring (P/NP) lines and high alcohol-drinking/low alcohol-drinking (HAD/LAD) replicated lines, of AUD as examined through the lens of whole genomic analyses.

METHODS

We used complete genome sequencing of the P/NP lines and previously published sequences of the HAD/LAD replicates to enhance the discovery of variants associated with AUD and to remove confounding with genetic background and random genetic drift. Specifically, we used high-order statistical methods to search for genetic variants whose frequency changes in whole sets of gene ontologies corresponded with phenotypic changes in the direction of selection, that is, ethanol-drinking preference.

RESULTS

Our first finding was that in addition to variants causing translational changes, the principal genetic changes associated with drinking predisposition were silent mutations and mutations in the 3' untranslated regions (3'UTR) of genes. Neither of these types of mutations alters the amino acid sequence of the translated protein but they influence both the rate and conformation of gene transcription, including its stability and posttranslational events that alter gene efficacy. This finding argues for refocusing human genomic studies on changes in gene efficacy. Among the key ontologies identified were the central genes associated with the Na+ voltage-gated channels of neurons and glia (including the Scn1a, Scn2a, Scn2b, Scn3a, Scn7a, and Scn9a subtypes) and excitatory glutamatergic secretion (including Grm2 and Myo6), both of which are essential in neuroplasticity. In addition, we identified "Nociception or Sensory Perception of Pain," which contained variants in nociception (Arrb1, Ccl3, Ephb1) and enlist sodium (Scn1a, Scn2a, Scn2b, Scn3a, Scn7a), pain activation (Scn9a), and potassium channel (Kcna1) genes.

CONCLUSION

The multi-model analyses used herein reduced the confounding effects of random drift and the "founders" genetic background. The most differentiated bidirectionally selected genes across all three animal models were Scn9a, Scn1a, and Kcna, all of which are annotated in the nociception ontology. The complexity of neuroplasticity and nociception adds strength to the hypothesis that neuroplasticity and pain (physical or psychological) are prominent phenotypes genetically linked to the development of AUD.

Histomorphometry of the Sural Nerve for Use as a CFNG in Facial Reanimation Procedures

Facial palsy (FP) is a debilitating nerve pathology. Cross Face Nerve Grafting (CFNG) describes a surgical technique that uses nerve grafts to reanimate the paralyzed face. The sural nerve has been shown to be a reliable nerve graft with little donor side morbidity. Therefore, we aimed to investigate the microanatomy of the sural nerve. Biopsies were obtained from 15 FP patients who underwent CFNG using sural nerve grafts. Histological cross-sections were fixated, stained with PPD, and digitized. Histomorphometry and a validated software-based axon quantification were conducted. The median age of the operated patients was 37 years (5-62 years). There was a significant difference in axonal capacity decrease towards the periphery when comparing proximal vs. distal biopsies (p = 0.047), while the side of nerve harvest showed no significant differences in nerve caliber (proximal p = 0.253, distal p = 0.506) and axonal capacity for proximal and distal biopsies (proximal p = 0.414, distal p = 0.922). Age did not correlate with axonal capacity (proximal: R = -0.201, p = 0.603; distal: R = 0.317, p = 0.292). These novel insights into the microanatomy of the sural nerve may help refine CFNG techniques and individualize FP patient treatment plans, ultimately improving overall patient outcomes.

Altered Neural Pathways and Related Brain Remodeling: A Rat Study Using Different Nerve Reconstructions

BACKGROUND

Function recovery is related to cortical plasticity. The brain remodeling patterns induced by alterations in peripheral nerve pathways with different nerve reconstructions are unknown.

OBJECTIVE

To explore brain remodeling patterns related to alterations in peripheral neural pathways after different nerve reconstruction surgeries.

METHODS

Twenty-four female Sprague-Dawley rats underwent complete left brachial plexus nerve transection, together with the following interventions: no nerve repair (n = 8), grafted nerve repair (n = 8), and phrenic nerve transfer (n = 8). Resting-state functional MR images of brain were acquired at the end of seventh month postsurgery. Amplitude of low-frequency fluctuation (ALFF), regional homogeneity (ReHo), and functional connectivity (FC) were compared among 3 groups. Behavioral observation and electromyography assessed nerve regeneration.

RESULTS

Compared with brachial plexus injury group, ALFF and ReHo of left entorhinal cortex decreased in nerve repair and nerve transfer groups. The nerve transfer group showed increased ALFF and ReHo than nerve repair group in left caudate putamen, right accumbens nucleus shell (AcbSh), and right somatosensory cortex. The FC between right somatosensory cortex and bilateral piriform cortices and bilateral somatosensory cortices increased in nerve repair group than brachial plexus injury and nerve transfer groups. The nerve transfer group showed increased FC between right somatosensory cortex and areas including left corpus callosum, left retrosplenial cortex, right parietal association cortex, and right dorsolateral thalamus than nerve repair group.

CONCLUSION

Entorhinal cortex is a key brain area in recovery of limb function after nerve reconstruction. Nerve transfer related brain remodeling mainly involved contralateral sensorimotor areas, facilitating directional "shifting" of motor representation.

Different Cortical Activation of Facial Synkinesis Patients with Different Course of Disease: A Task fMRI Study

Facial synkinesis is a disease characterized by unintentional activation of facial muscles, which causes that the patients cannot control their facial expressions independently. Previous studies have shown that its pathogenesis is related to the reorganization of cerebral cortex, but it remains unclear what brain changes the patients have at different stage of the disease. For this study, we recruited 30 patients with facial synkinesis and 19 healthy control subjects from Shanghai Huashan Hospital. All participants completed bilateral blinking and grinning tasks while functional magnetic resonance imaging (fMRI) data was collected. We measured the brain activation strength of each task and observed the activation similarity of the ipsilateral tasks. Then we explored the correlation between activation pattern and clinical scale. Results showed different activation pattern along the courses of disease for blinking and grinning task, which may be due to the inconsistent process of cortical reorganization. The late stage group activated more in blinking task, but the least in grinning tasks, especially on the affected side (p<0.001 at voxel level, p<0.05 at cluster level, FWE corrected). Compared with healthy controls, the activation of patients between tasks on the affected side is more similar(p<0.05). There was a negative correlation in right postcentral gyrus between activation similarity and scale scores (symmetry of voluntary movement scores: R = -0.469, p = 0.009). This could be attributed to the rearrangement of the nervous system following facial nerve injury, leading to incorrect connections between nerves and muscles. Our study may be helpful for understanding mechanism of facial synkinesis and provide basis for the stage-dependent diagnosis and treatment.

The Role of Hydrogen Sulfide in Regulation of Cell Death following Neurotrauma and Related Neurodegenerative and Psychiatric Diseases

Injuries of the central (CNS) and peripheral nervous system (PNS) are a serious problem of the modern healthcare system. The situation is complicated by the lack of clinically effective neuroprotective drugs that can protect damaged neurons and glial cells from death. In addition, people who have undergone neurotrauma often develop mental disorders and neurodegenerative diseases that worsen the quality of life up to severe disability and death. Hydrogen sulfide (H₂S) is a gaseous signaling molecule that performs various cellular functions in normal and pathological conditions. However, the role of H₂S in neurotrauma and mental disorders remains unexplored and sometimes controversial. In this large-scale review study, we examined the various biological effects of H₂S associated with survival and cell death in trauma to the brain, spinal cord, and PNS, and the signaling mechanisms underlying the pathogenesis of mental illnesses, such as cognitive impairment, encephalopathy, depression and anxiety disorders, epilepsy and chronic pain. We also studied the role of H₂S in the pathogenesis of neurodegenerative diseases: Alzheimer's disease (AD) and Parkinson's disease (PD). In addition, we reviewed the current state of the art study of H₂S donors as neuroprotectors and the possibility of their therapeutic uses in medicine. Our study showed that H₂S has great neuroprotective potential. H₂S reduces oxidative stress, lipid peroxidation, and neuroinflammation; inhibits processes associated with apoptosis, autophagy, ferroptosis and pyroptosis; prevents the destruction of the blood-brain barrier; increases the expression of neurotrophic factors; and models the activity of Ca²⁺ channels in neurotrauma. In addition, H₂S activates neuroprotective signaling pathways in psychiatric and neurodegenerative diseases. However, high levels of H₂S can cause cytotoxic effects. Thus, the development of H₂S-associated neuroprotectors seems to be especially relevant. However, so far, all H₂S modulators are at the stage of preclinical trials. Nevertheless, many of them show a high neuroprotective effect in various animal models of neurotrauma and related disorders. Despite the fact that our review is very extensive and detailed, it is well structured right down to the conclusions, which will allow researchers to quickly find the proper information they are interested in.

KCC2 downregulation after sciatic nerve injury enhances motor function recovery

Injury to mature neurons induces downregulated KCC2 expression and activity, resulting in elevated intracellular [Cl^-] and depolarized GABAergic signaling. This phenotype mirrors immature neurons wherein GABA-evoked depolarizations facilitate neuronal circuit maturation. Thus, injury-induced KCC2 downregulation is broadly speculated to similarly facilitate neuronal circuit repair. We test this hypothesis in spinal cord motoneurons injured by sciatic nerve crush, using transgenic (CaMKII-KCC2) mice wherein conditional CaMKIIα promoter-KCC2 expression coupling selectively prevents injury-induced KCC2 downregulation. We demonstrate, via an accelerating rotarod assay, impaired motor function recovery in CaMKII-KCC2 mice relative to wild-type mice. Across both cohorts, we observe similar motoneuron survival and re-innervation rates, but differing post-injury reorganization patterns of synaptic input to motoneuron somas-for wild-type, both VGLUT1-positive (excitatory) and GAD67-positive (inhibitory) terminal counts decrease; for CaMKII-KCC2, only VGLUT1-positive terminal counts decrease. Finally, we recapitulate the impaired motor function recovery of CaMKII-KCC2 mice in wild-type mice by administering local spinal cord injections of bicuculline (GABA_A receptor blockade) or bumetanide (lowers intracellular [Cl^-] by NKCC1 blockade) during the early post-injury period. Thus, our results provide direct evidence that injury-induced KCC2 downregulation enhances motor function recovery and suggest an underlying mechanism of depolarizing GABAergic signaling driving adaptive reconfiguration of presynaptic GABAergic input.

Central Facial Nervous System Biomolecules Involved in Peripheral Facial Nerve Injury Responses and Potential Therapeutic Strategies

Peripheral facial nerve injury leads to changes in the expression of various neuroactive substances that affect nerve cell damage, survival, growth, and regeneration. In the case of peripheral facial nerve damage, the injury directly affects the peripheral nerves and induces changes in the central nervous system (CNS) through various factors, but the substances involved in these changes in the CNS are not well understood. The objective of this review is to investigate the biomolecules involved in peripheral facial nerve damage so as to gain insight into the mechanisms and limitations of targeting the CNS after such damage and identify potential facial nerve treatment strategies. To this end, we searched PubMed using keywords and exclusion criteria and selected 29 eligible experimental studies. Our analysis summarizes basic experimental studies on changes in the CNS following peripheral facial nerve damage, focusing on biomolecules that increase or decrease in the CNS and/or those involved in the damage, and reviews various approaches for treating facial nerve injury. By establishing the biomolecules in the CNS that change after peripheral nerve damage, we can expect to identify factors that play an important role in functional recovery from facial nerve damage. Accordingly, this review could represent a significant step toward developing treatment strategies for peripheral facial palsy.

Aligned core-shell fibrous nerve wrap containing Bletilla striata polysaccharide improves functional outcomes of peripheral nerve repair

Peripheral nerve injuries are commonly encountered in extremity traumas. Their motor and sensory recovery following microsurgical repair is limited by slow regeneration speed (<1 mm/d) and subsequent muscle atrophy, which are consequently correlated with the activity of local Schwann cells and efficacy of axon outgrowth. To promote post-surgical nerve regeneration, we synthesized a nerve wrap consisting of an aligned polycaprolactone (PCL) fiber shell with a Bletilla striata polysaccharide (BSP) core (APB). Cell experiments demonstrated that the APB nerve wrap markedly promoted neurite outgrowth and Schwann cell migration and proliferation. Animal experiments applying a rat sciatic nerve repair model indicated that the APB nerve wrap restored conduction efficacy of the repaired nerve and the compound action potential as well as contraction force of the related leg muscles. Histology of the downstream nerves disclosed significantly higher fascicle diameter and myelin thickness with the APB nerve wrap compared to those without BSP. Thus, the BSP-loaded nerve wrap is potentially beneficial for the functional recovery after peripheral nerve repair and offers sustained targeted release of a natural polysaccharide with good bioactivity.

Facile construction of calcium titanate-loaded silk fibroin scaffolds hybrid frameworks for accelerating neuronal cell growth in peripheral nerve regeneration

Different concentrations of calcium titanate (CaTiO3) nanoparticles were loaded into the Silk fibroin (SF) solution to construct porous SF@CaTiO3 hybrid scaffolds, which were shown to have enhanced properties for stimulating peripheral nerve regeneration. Surface charges, crystallization intensity, wettability, porosity, and morphology were measured and analyzed. We analyzed the hybrid porous SF@CaTiO₃ scaffolds that affected the expansion of Schwann cells. The results demonstrated a concentration-dependent influence on the dispersion of nanoparticles in the CaTiO₃ hybridized SF scaffolds. Incorporating CaTiO₃-NPs into the porous SF@CaTiO₃ hybrid scaffolds can boost hydrophobicity while decreasing surface charge density and porosity. The hybridized scaffolds mostly had an orthorhombic calcium titanate crystal structure with amorphous Silk fibroin mixed. Schwann cell cultures revealed that SF@CaTiO₃ hybrid scaffolds containing an optimal CaTiO₃-NPs concentration could stimulate the proliferation, attachment, and protection of Schwann cell biological functions, suggesting the scaffolds' potential for use in peripheral nerve regeneration.

Electrophysiological Study in the Right Upper and Lower Limbs in Infants with Lumbosacral Meningomyelocele and in Normal Infants: A Case-control Study

Objective

The study aimed to assess the electrophysiological parameters (Hofmann reflex [H-reflex] and motor nerve conduction velocity [MNCV]) on children's upper and lower limbs with lumbosacral meningomyelocele (MMC) and age-matched control to see the effect of the MMC on the cervical segment of the spinal cord.

Materials and Methods

The present study was performed on infants with lumbosacral MMC. Twenty-five infants were examined with a mean age of 50 days of either sex. Out of them, 13 infants were in control and the remaining 12 were diagnosed with MMC. The H-reflex parameter and MNCV were recorded in these children's right upper and lower limbs.

Results

H-reflex was elicited in all the control group babies. In MMC, the H-reflex was elicited in the upper limbs. However, H-reflex was not elicited in the lower limbs of a few MMC babies. The upper limb's H-reflex parameters and conduction velocity were significantly higher than those corresponding lower limbs in control babies. In MMC, where the H-reflex was elicited, such differences in the lower and upper limbs were not observed. However, the values of MNCV in the upper limb (right median nerve) were significantly less, and the values of Hmax in the lower limb (soleus muscle) were significantly more in MMC babies than in the control group.

Conclusions

The values of electrophysiological parameters were higher in the upper limbs as compared to the corresponding lower limbs in control. These values were not altered in the upper limbs than those corresponding lower limbs of MMC, suggesting that motor function development was impaired/delayed in the spinal segment cranial to MMC lesion, and motor impairment in MMC children is mostly a result of upper motor neuron dysfunction.

Concomitant Occurrence of Acute Motor Axonal Neuropathy in Systemic Lupus Erythematosus

ABSTRACT

Few case reports exist on the association of acute motor axonal neuropathy, a subtype of the Guillain-Barré syndrome (GBS), with systemic lupus erythematosus. Standard therapeutic guidelines for concomitant acute motor axonal neuropathy and systemic lupus erythematosus in the acute phase are not established, and no studies have reported physical medicine and rehabilitation perspective management in the plateau and recovery phases. A 50-yr-old woman with systemic lupus erythematosus presented with upper and lower limb weakness that progressed to an inability to walk. Neurological examination, radiologic evaluation, serologic analysis, and electrodiagnostic study were conducted, and she was diagnosed with acute motor axonal neuropathy. Subsequently, intravenous immunoglobulin therapy was administered. She complained of residual upper and lower extremity weakness and an inability to walk 3 mos after symptom onset. She underwent an intensive inpatient rehabilitation program for 6 wks and showed remarkable recovery in muscle strength and functional status (Berg Balance Scale, modified Barthel index, and Guillain-Barré syndrome disability scale). To our knowledge, this is the first reported case that focused on the functional outcomes after the rehabilitation program in acute motor axonal neuropathy with a history of systemic lupus erythematosus. This case report emphasizes the need for rehabilitation intervention for functional recovery in the plateau and recovery phases.

Allogenic bone marrow-derived mesenchymal stem cells and its conditioned media for repairing acute and sub-acute peripheral nerve injuries in a rabbit model

The present study evaluated healing potential of bone marrow-derived mesenchymal stem cells (BM-MSCs) and BM-MSCs-conditioned medium (BM-MSCs-CM) for acute and subacute injuries in the rabbit peripheral nerve injury model. The regenerative capacity of MSCs was evaluated in 40 rabbits divided into eight groups, four groups each for acute and subacute injury models. BM-MSCs and BM-MSCS-CM were prepared by isolating allogenic bone marrow from the iliac crest. After inducing sciatic nerve crush injury, different treatments consisting of PBS, Laminin, BM-MSCs + laminin, and BM-MSCS-CM + laminin were used on the day of injury in the acute injury model and after ten days of crush injury in the subacute groups. The parameters studied included: pain, total neurological score, gastrocnemius muscle weight and volume ratio, histopathology of the sciatic nerve and gastrocnemius muscle, and scanning electron microscopy (SEM). Findings indicate that BM-MSCs and BM-MSCS-CM have augmented the regenerative capacity in acute and subacute injury groups with a slightly better improvement in the subacute groups than the animals in acute injury groups. Histopathology data revealed different levels of regenerative process undergoing in the nerve. Neurological observations, gastrocnemius muscle evaluation, muscle histopathology, and the SEM results depicted better healing in animals treated with BM-MSCs and BM-MSCS-CM. With this data, it could be concluded that BM-MSCs support the healing of injured peripheral nerves, and the BM-MSCS-CM does accelerate the healing of acute and subacute peripheral nerve injuries in rabbits. However, stem cell therapy may be indicated during the subacute phase for better results.

Enhanced sciatic nerve regeneration with fibrin scaffold containing human endometrial stem cells and insulin encapsulated chitosan particles: An in vivo study

BACKGROUND

Based on recent advances in tissue engineering and stem cell therapy in nervous system diseases treatments, this study aimed to investigate sciatic nerve regeneration using human endometrial stem cells (hEnSCs) encapsulated fibrin gel containing chitosan nanoparticle loaded by insulin (Ins-CPs). Stem cells and also Insulin (Ins), which is a strong signaling molecule in peripheral nerve regeneration, play an important role in neural tissue engineering.

METHODS

The fibrin hydrogel scaffold containing insulin loaded chitosan particles was synthesized and characterized. Release profiles of insulin from hydrogel was determined through UV-visible spectroscopy. Also, human endometrial stem cells encapsulated in hydrogel and its cell biocompatibility were assigned. Furthermore, the sciatic nerve crush injury was carried out and prepared fibrin gel was injected at the crush injury site by an 18-gage needle. Eight and twelve weeks later, the recovery of motor and sensory function and histopathological evaluation were assessed.

RESULTS

The in vitro experiments showed that the insulin can promote hEnSCs proliferation within a certain concentration range. Animals' treatment confirmed that developed fibrin gel containing Ins-CPs and hEnSCs significantly improves motor function and sensory recovery. Hematoxylin and Eosin (H&E) images provided from cross-sectional and, longitudinal-sections of the harvested regenerative nerve showed that regenerative nerve fibers had been formed and accompanied with new blood vessels in the fibrin/insulin/hEnSCs group.

CONCLUSION

Our results demonstrated that the prepared hydrogel scaffolds containing insulin nanoparticles and hEnSCs could be considered as a potential biomaterial aimed at regeneration of sciatic nerves.

Hopeless Neuroma-The Neurotized Free Flap Tissue Augmentation as Salvage Therapy-A Concept and Clinical Demonstration

Therapy-resistant neuroma pain is a devastating condition for patients and surgeons. Although various methods are described to surgically deal with neuromas, some discontinuity and stump neuroma therapies have anatomical limitations. It is widely known that a neurotizable target for axon ingrowth is beneficial for dealing with neuromas. The nerve needs "something to do". Furthermore, sufficient soft tissue coverage plays a major role in sufficient neuroma therapy. We aimed, therefore, to demonstrate our approach for therapy of resistant neuromas with insufficient tissue coverage using free flaps, which are sensory neurotized via anatomical constant branches. The central idea is to provide a new target, a new "to do" for the painful mislead axons, as well as an augmentation of deficient soft tissues. As indication is key, we furthermore demonstrate clinical cases and common neurotizable workhorse flaps.

Massive Loss of Proprioceptive Ia Synapses in Rat Spinal Motoneurons after Nerve Crush Injuries in the Postnatal Period

Peripheral nerve injuries (PNIs) induce the retraction from the ventral horn of the synaptic collaterals of Ia afferents injured in the nerve, effectively removing Ia synapses from α-motoneurons. The loss of Ia input impairs functional recovery and could explain, in part, better recovery after PNIs with better Ia synaptic preservation. Synaptic losses correlate with injury severity, speed, and efficiency of muscle reinnervation and requires ventral microglia activation. It is unknown whether this plasticity is age dependent. In neonates, axotomized motoneurons and sensory neurons undergo apoptosis, but after postnatal day 10 most survive. The goal of this study was to analyze vesicular glutamate transporter 1 (VGluT1)-labeled Ia synapses (which also include II afferents) after nerve crush in 10 day old rats, a PNI causing little Ia/II synapse loss in adult rats. We confirmed fast and efficient reinnervation of leg muscles; however, a massive number of VGluT1/Ia/II synapses were permanently lost. This synapse loss was similar to that after more severe nerve injuries involving full transection in adults. In adults, disappearance of ventrally directed Ia/II collaterals targeting α-motoneurons was associated with a prolonged microglia reaction and a CCR2 mechanism that included infiltration of CCR2 blood immune cells. By contrast, microgliosis after P10 injuries was fast, resolved in about a week, and there was no evidence of peripheral immune cell infiltration. We conclude that VGluT1/Ia/II synapse loss in young animals differs in mechanism, perhaps associated with higher microglia synaptic pruning activity at this age and results in larger losses after milder nerve injuries.

Repair of Long Peripheral Nerve Defects in Sheep: A Translational Model for Nerve Regeneration

Despite advances in microsurgery, full functional recovery of severe peripheral nerve injuries is not commonly attained. The sheep appears as a good preclinical model since it presents nerves with similar characteristics to humans. In this study, we induced 5 or 7 cm resection in the peroneal nerve and repaired with an autograft. Functional evaluation was performed monthly. Electromyographic and ultrasound tests were performed at 6.5 and 9 months postoperation (mpo). No significant differences were found between groups with respect to functional tests, although slow improvements were seen from 5 mpo. Electrophysiological tests showed compound muscle action potentials (CMAP) of small amplitude at 6.5 mpo that increased at 9 mpo, although they were significantly lower than the contralateral side. Ultrasound tests showed significantly reduced size of tibialis anterior (TA) muscle at 6.5 mpo and partially recovered size at 9 mpo. Histological evaluation of the grafts showed good axonal regeneration in all except one sheep from autograft 7 cm (AG7) group, while distal to the graft there was a higher number of axons than in control nerves. The results indicate that sheep nerve repair is a useful model for investigating long-gap peripheral nerve injuries.

Opioid modulation of T-type Ca2+ channel-dependent neuritogenesis/neurite outgrowth through the prostaglandin E2/EP4 receptor/protein kinase A pathway in mouse dorsal root ganglion neurons

Irregular regeneration or inappropriate remodeling of the axons of the primary afferent neurons after peripheral nerve trauma could be associated with the development of neuropathic pain. We analyzed the molecular mechanisms for the neuritogenesis and neurite outgrowth caused by prostaglandin E2 (PGE2) in mouse dorsal root ganglion (DRG) neurons, and evaluated their opioid modulation. PGE2 in combination with IBMX, a phosphodiesterase inhibitor, caused neuritogenesis/neurite outgrowth in DRG cells, an effect abolished by a prostanoid EP4, but not EP2, receptor antagonist, and inhibitors of adenylyl cyclase or protein kinase A (PKA). Blockers of T-type Ca2+ channels (T-channels), that are responsible for window currents involving the sustained low-level Ca2+ entry at voltages near the resting membrane potentials and can be functionally upregulated by PKA, inhibited the neuritogenesis/neurite outgrowth caused by PGE2/IBMX or dibutylyl cyclic AMP, a PKA activator, in DRG neurons, an inhibitory effect mimicked by ZnCl2 and ascorbic acid that block Cav3.2, but not Cav3.1 or Cav3.3, T-channels. Morphine and DAMGO, μ-opioid receptor (MOR) agonists, suppressed the neuritogenesis and/or neurite outgrowth induced by PGE2/IBMX in DRG neurons and also DRG neuron-like ND7/23 cells, an effect reversed by naloxone or β-funaltrexamine, a selective MOR antagonist. Our data suggest that the EP4 receptor/PKA/Cav3.2 pathway is involved in the PGE2-induced neuritogenesis/neurite outgrowth in DRG neurons, which can be suppressed by MOR stimulation. We propose that MOR agonists including morphine in the early phase after peripheral nerve trauma might delay the axonal regeneration of the primary afferent neurons but prevent the development of neuropathic pain.

Denervated mouse CA1 pyramidal neurons express homeostatic synaptic plasticity following entorhinal cortex lesion

Structural, functional, and molecular reorganization of denervated neural networks is often observed in neurological conditions. The loss of input is accompanied by homeostatic synaptic adaptations, which can affect the reorganization process. A major challenge of denervation-induced homeostatic plasticity operating in complex neural networks is the specialization of neuronal inputs. It remains unclear whether neurons respond similarly to the loss of distinct inputs. Here, we used in vitro entorhinal cortex lesion (ECL) and Schaffer collateral lesion (SCL) in mouse organotypic entorhino-hippocampal tissue cultures to study denervation-induced plasticity of CA1 pyramidal neurons. We observed microglia accumulation, presynaptic bouton degeneration, and a reduction in dendritic spine numbers in the denervated layers 3 days after SCL and ECL. Transcriptome analysis of the CA1 region revealed complex changes in differential gene expression following SCL and ECL compared to non-lesioned controls with a specific enrichment of differentially expressed synapse-related genes observed after ECL. Consistent with this finding, denervation-induced homeostatic plasticity of excitatory synapses was observed 3 days after ECL but not after SCL. Chemogenetic silencing of the EC but not CA3 confirmed the pathway-specific induction of homeostatic synaptic plasticity in CA1. Additionally, increased RNA oxidation was observed after SCL and ECL. These results reveal important commonalities and differences between distinct pathway lesions and demonstrate a pathway-specific induction of denervation-induced homeostatic synaptic plasticity.

Artificial Intelligence-Assisted Evaluation of the Spatial Relationship between Brain Arteriovenous Malformations and the Corticospinal Tract to Predict Postsurgical Motor Defects

BACKGROUND AND PURPOSE

Preoperative evaluation of brain AVMs is crucial for the selection of surgical candidates. Our goal was to use artificial intelligence to predict postsurgical motor defects in patients with brain AVMs involving motor-related areas.

MATERIALS AND METHODS

Eighty-three patients who underwent microsurgical resection of brain AVMs involving motor-related areas were retrospectively reviewed. Four artificial intelligence-based indicators were calculated with artificial intelligence on TOF-MRA and DTI, including FN5mm/50mm (the proportion of fiber numbers within 5-50mm from the lesion border), FN10mm/50mm (the same but within 10-50mm), FP5mm/50mm (the proportion of fiber voxel points within 5-50mm from the lesion border), and FP10mm/50mm (the same but within 10-50mm). The association between the variables and long-term postsurgical motor defects was analyzed using univariate and multivariate analyses. Least absolute shrinkage and selection operator regression with the Pearson correlation coefficient was used to select the optimal features to develop the machine learning model to predict postsurgical motor defects. The area under the curve was calculated to evaluate the predictive performance.

RESULTS

In patients with and without postsurgical motor defects, the mean FN5mm/50mm, FN10mm/50mm, FP5mm/50mm, and FP10mm/50mm were 0.24 (SD, 0.24) and 0.03 (SD, 0.06), 0.37 (SD, 0.27) and 0.06 (SD, 0.08), 0.06 (SD, 0.10) and 0.01 (SD, 0.02), and 0.10 (SD, 0.12) and 0.02 (SD, 0.05), respectively. Univariate and multivariate logistic analyses identified FN10mm/50mm as an independent risk factor for long-term postsurgical motor defects (P = .002). FN10mm/50mm achieved a mean area under the curve of 0.86 (SD, 0.08). The mean area under the curve of the machine learning model consisting of FN10mm/50mm, diffuseness, and the Spetzler-Martin score was 0.88 (SD, 0.07).

CONCLUSIONS

The artificial intelligence-based indicator, FN10mm/50mm, can reflect the lesion-fiber spatial relationship and act as a dominant predictor for postsurgical motor defects in patients with brain AVMs involving motor-related areas.

The Relationship Between Health-Related Quality of Life and Lower-Extremity Visuomotor Reaction Time in Young Adult Women Following Ankle Sprain

CONTEXT

Many individuals who sustain a lateral ankle sprain (LAS) fail to return to prior activity due to residual symptoms; and report elevated levels of injury-related fear, decreased function, and decreased health-related quality of life (HRQOL). Additionally, individuals with history of LAS exhibit deficits in neurocognitive functional measures like visuomotor reaction time (VMRT), which contributes to worse patient-reported outcome scores. The aim of this study was to examine the relationship between HRQOL and lower-extremity (LE) VMRT in individuals with LAS history.

DESIGN

Cross-sectional.

METHODS

Young adult female volunteers with history of LAS (n = 22; age = 24 [3.5] y; height = 163.1 [9.8] cm; mass = 65.1 [11.5] kg; and time since last LAS = 67.8 [50.5] mo) completed HRQOL outcomes including the following: (1) Tampa Scale of Kinesiophobia-11, (2) Fear-Avoidance Beliefs Questionnaire, (3) Penn State Worry Questionnaire, (4) modified Disablement in the Physically Active Scale, and (5) Foot and Ankle Disability Index (FADI). Additionally, participants completed a LE-VMRT task by responding to a visual stimulus using their foot to deactivate light sensors. Participants completed trials bilaterally. Separate Spearman rho correlations were performed to assess the relationship between patient-reported outcomes assessing constructs of HRQOL and LE-VRMT bilaterally. Significance was set at P < .05.

RESULTS

There was a strong, significant negative correlation between FADI-Activities of Daily Living (ρ = -.68; P = .002) and FADI-Sport (ρ = -.76; P = .001) scores and injured limb LE-VMRT; moderate, significant negative correlations between the uninjured limb LE-VMRT and FADI-Activities of Daily Living (ρ = -.60; P = .01) and FADI-Sport (ρ = -.60; P = .01) scores; and moderate, significant positive correlations between the injured limb LE-VMRT and modified Disablement in the Physically Active Scale-Physical Summary Component (ρ = .52; P = .01) and modified Disablement in the Physically Active Scale-Total (ρ = .54; P = .02) scores. All other correlations were not statistically significant.

CONCLUSIONS

Young adult women with history of LAS demonstrated an association between self-reported constructs of HRQOL and LE-VMRT. As LE-VMRT is a modifiable injury risk factor, future studies should examine the effectiveness of interventions designed to improve LE-VMRT and the impact on self-reported HRQOL.

Selective Repair of Motor Branches in the Femoral Nerve by Transferring the Motor Branches of Obturator Nerve: An Anatomical Feasibility Study

BACKGROUND

Anterior branch of the obturator nerve transfer has been proven as an effective method for femoral nerve injuries, but the patient still has difficulty in rising and squatting, up and downstairs. Here, we presented a novel neurotization procedure of selectively repairing 3 motor branches of the femoral nerve by transferring motor branches of the obturator nerve in the thigh level and assessing its anatomical feasibility.

METHODS

Eight adult cadavers (16 thighs) were dissected. The nerve overlap distance between the gracilis branch and the rectus femoris (RF) branch, the adductor longus (AL) branch and the vastus medialis (VM) branch, as well as the adductor magnus (AM) branch and the vastus intermedius (VI) branch were measured. Also, the axon counts of the donor and recipient nerve were evaluated by histological evaluation.

RESULTS

In all specimens, nerve overlap of at least 2.1 cm was observed in all 16 dissected thighs between the donor and recipient nerve branches, and the repair appeared to be without tension. There is no significant difference in the axon counts between gracilis branch (598 ± 83) and the RF branch (709 ± 151). The axon counts of the AL branch (601 ± 93) was about half of axon counts of the VM branch (1423 ± 189), and the axon counts of AM branch (761 ± 110) was also about half of the VI branch (1649 ± 281).

CONCLUSIONS

This novel technique of the combined nerve transfers below the inguinal ligament, specifically the gracilis branch to the RF branch, the AL branch to the VM branch, and the AM branch to the VI branch, is anatomically feasible. It provides a promising alternative in the repair of femoral nerve injuries and an anatomical basis for the clinical application of motor branches of the obturator nerve transfer to repair the motor portion of the injured femoral nerve.

Concise review: Current understanding of extracellular vesicles to treat neuropathic pain

Extracellular vesicles (EVs) including exosomes are vesicular vesicles with phospholipid bilayer implicated in many cellular interactions and have the ability to transfer multiple types of cargo to cells. It has been found that EVs can package various molecules including proteins and nucleic acids (DNA, mRNA, and noncoding RNA). The discovery of EVs as carriers of proteins and various forms of RNA, such as microRNAs (miRNA) and long noncoding RNAs (lncRNA), has raised great interest in the field of drug delivery. Despite the underlying mechanisms of neuropathic pain being unclear, it has been shown that uncontrolled glial cell activation and the neuroinflammation response to noxious stimulation are important in the emergence and maintenance of neuropathic pain. Many studies have demonstrated a role for noncoding RNAs in the pathogenesis of neuropathic pain and EVs may offer possibilities as carriers of noncoding RNAs for potential in neuropathic pain treatment. In this article, the origins and clinical application of EVs and the mechanism of neuropathic pain development are briefly introduced. Furthermore, we demonstrate the therapeutic roles of EVs in neuropathic pain and that this involve vesicular regulation of glial cell activation and neuroinflammation.

Electrodeposition of chitosan/graphene oxide conduit to enhance peripheral nerve regeneration

Currently available commercial nerve guidance conduits have been applied in the repair of peripheral nerve defects. However, a conduit exhibiting good biocompatibility remains to be developed. In this work, a series of chitosan/graphene oxide (GO) films with concentrations of GO varying from 0–1 wt% (collectively referred to as CHGF-n) were prepared by an electrodeposition technique. The effects of CHGF-n on proliferation and adhesion abilities of Schwann cells were evaluated. The results showed that Schwann cells exhibited elongated spindle shapes and upregulated expression of nerve regeneration-related factors such as Krox20 (a key myelination factor), Zeb2 (essential for Schwann cell differentiation, myelination, and nerve repair), and transforming growth factor β (a cytokine with regenerative functions). In addition, a nerve guidance conduit with a GO content of 0.25% (CHGFC-0.25) was implanted to repair a 10-mm sciatic nerve defect in rats. The results indicated improvements in sciatic functional index, electrophysiology, and sciatic nerve and gastrocnemius muscle histology compared with the CHGFC-0 group, and similar outcomes to the autograft group. In conclusion, we provide a candidate method for the repair of peripheral nerve defects using free-standing chitosan/GO nerve conduits produced by electrodeposition.

Cerebral Adaptation Associated with Peripheral Nerve Recovery in Neuralgic Amyotrophy: A Randomized Controlled Trial

BACKGROUND

Neuralgic amyotrophy (NA) is a common peripheral nerve disorder caused by auto-immune inflammation of nerves in the brachial plexus territory, characterized by acute pain and weakness of the shoulder muscles, followed by motor impairment. Recent work has confirmed that NA patients with residual motor dysfunction have abnormal cerebral sensorimotor representations of their affected upper extremity.

OBJECTIVE

To determine whether abnormal cerebral sensorimotor representations associated with NA can be altered by specialized, multidisciplinary outpatient rehabilitation focused on relearning motor control.

METHODS

27 NA patients with residual lateralized symptoms in the right upper extremity participated in a randomized controlled trial, comparing 17 weeks of multidisciplinary rehabilitation (n = 16) to usual care (n = 11). We used task-based functional MRI and a hand laterality judgment task, which involves motor imagery and is sensitive to altered cerebral sensorimotor representations of the upper extremity.

RESULTS

Change in task performance and related brain activity did not differ significantly between the multidisciplinary rehabilitation and usual care groups, whereas the multidisciplinary rehabilitation group showed significantly greater clinical improvement on the Shoulder Rating Questionnaire. Both groups, however, showed a significant improvement in task performance from baseline to follow-up, and significantly increased activity in visuomotor occipito-parietal brain areas, both specific to their affected upper extremity.

CONCLUSIONS

Abnormal cerebral sensorimotor representations of the upper extremity after peripheral nerve damage in NA can recover toward normality. As adaptations occurred in visuomotor brain areas, multidisciplinary rehabilitation after peripheral nerve damage may be further optimized by applying visuomotor strategies. This study is registered at ClinicalTrials.gov (NCT03441347).

Repair of Long Nerve Defects with a New Decellularized Nerve Graft in Rats and in Sheep

Decellularized nerve allografts (DC) are an alternative to autografts (AG) for repairing severe peripheral nerve injuries. We have assessed a new DC provided by VERIGRAFT. The decellularization procedure completely removed cellularity while preserving the extracellular matrix. We first assessed the DC in a 15 mm gap in the sciatic nerve of rats, showing slightly delayed but effective regeneration. Then, we assayed the DC in a 70 mm gap in the peroneal nerve of sheep compared with AG. Evaluation of nerve regeneration and functional recovery was performed by clinical, electrophysiology and ultrasound tests. No significant differences were found in functional recovery between groups of sheep. Histology showed a preserved fascicular structure in the AG while in the DC grafts regenerated axons were grouped in small units. In conclusion, the DC was permissive for axonal regeneration and allowed to repair a 70 mm long gap in the sheep nerve.

Characterization of circular RNAs in dorsal root ganglia after central and peripheral axon injuries

In central nervous system, axons fail to regenerate after injury while in peripheral nervous system, axons retain certain regenerative ability. Dorsal root ganglion (DRG) neuron has an ascending central axon branch and a descending peripheral axon branch stemming from one single axon and serves as a suitable model for the comparison of growth competence following central and peripheral axon injuries. Molecular alterations underpin different injury responses of DRG branches have been investigated from many aspects, such as coding gene expression, chromatin accessibility, and histone acetylation. However, changes of circular RNAs are poorly characterized. In the present study, we comprehensively investigate circular RNA expressions in DRGs after rat central and peripheral axon injuries using sequencing analysis and identify a total of 33 differentially expressed circular RNAs after central branch injury as well as 55 differentially expressed circular RNAs after peripheral branch injury. Functional enrichment of host genes of differentially expressed circular RNAs demonstrate the participation of Hippo signaling pathway and Notch signaling pathway after both central and peripheral axon injuries. Circular RNA changes after central axon injury are also linked with apoptosis and cellular junction while changes after peripheral axon injury are associated with metabolism and PTEN-related pathways. Altogether, the present study offers a systematic evaluation of alterations of circular RNAs in rat DRGs following injuries to the central and peripheral axon branches and contributes to the deciphering of essential biological activities and mechanisms behind successful nerve regeneration.

Thermosensitive hydrogel carrying extracellular vesicles from adipose-derived stem cells promotes peripheral nerve regeneration after microsurgical repair

Peripheral nerve injuries are commonly occurring traumas of the extremities; functional recovery is hindered by slow nerve regeneration (<1 mm/day) following microsurgical repair and subsequent muscle atrophy. Functional recovery after peripheral nerve repair is highly dependent on local Schwann cell activity and axon regeneration speed. Herein, to promote nerve regeneration, paracrine signals of adipose-derived stem cells were applied in the form of extracellular vesicles (EVs) loaded in a thermosensitive hydrogel (PALDE) that could solidify rapidly and sustain high EV concentration around a repaired nerve during surgery. Cell experiments revealed that PALDE hydrogel markedly promotes Schwann-cell migration and proliferation and axon outgrowth. In a rat sciatic nerve repair model, the PALDE hydrogel increased repaired-nerve conduction efficacy; contraction force of leg muscles innervated by the repaired nerve also recovered. Electromicroscopic examination of downstream nerves indicated that fascicle diameter and myeline thickness in the PALDE group (1.91 ± 0.61 and 1.06 ± 0.40 μm, respectively) were significantly higher than those in PALD and control groups. Thus, this EV-loaded thermosensitive hydrogel is a potential cell-free therapeutic modality to improve peripheral-nerve regeneration, offering sustained and focused EV release around the nerve-injury site to overcome rapid clearance and maintain EV bioactivity in vivo.