Nerve Injury Model Research Articles

A Roadmap of Peptide-Based Materials in Neural Regeneration.

Injuries to the nervous system lead to irreversible damage and limited functional recovery. The peripheral nervous system (PNS) can self-regenerate to some extent for short nerve gaps. In contrast, the central nervous system (CNS) has an intrinsic limitation to self-repair owing to its convoluted neural microenvironment and inhibitory response. The primary phase of CNS injury, happening within 48h, results from external impacts like mechanical stress. Afterward, the secondary phase of the injury occurs, originating from neuronal excitotoxicity, mitochondrial dysfunction, and neuroinflammation. No golden standard to treat injured neurons exists, and conventional medicine serves only as a protective approach to alleviating the symptoms of chronic injury. Synthetic peptides provide a promising approach for neural repair, either as soluble drugs or by using their intrinsic self-assembly propensity to serve as an extracellular matrix (ECM) mimic for cell adhesion and to incorporate bioactive epitopes. In this review, an overview of nerve injury models, common in vitro models, and peptide-based therapeutics such as ECM mimics is provided. Due to the complexity of treating neuronal injuries, a multidisciplinary collaboration between biologists, physicians, and material scientists is paramount. Together, scientists with complementary expertise will be required to formulate future therapeutic approaches for clinical use.

Porcine decellularized nerve matrix hydrogel attenuates neuroinflammation after peripheral nerve injury by inhibiting the TLR4/MyD88/NF-κB axis

Peripheral nerve injury causes severe neuroinflammation and has become a global medical challenge. Previous research has demonstrated that porcine decellularized nerve matrix hydrogel exhibits excellent biological properties and tissue specificity, highlighting its potential as a biomedical material for the repair of severe peripheral nerve injury; however, its role in modulating neuroinflammation post–peripheral nerve injury remains unknown. Here, we aimed to characterize the anti-inflammatory properties of porcine decellularized nerve matrix hydrogel and their underlying molecular mechanisms. Using peripheral nerve injury model rats treated with porcine decellularized nerve matrix hydrogel, we evaluated structural and functional recovery, macrophage phenotype alteration, specific cytokine expression, and changes in related signaling molecules in vivo. Similar parameters were evaluated in vitro using monocyte/macrophage cell lines stimulated with lipopolysaccharide and cultured on porcine decellularized nerve matrix hydrogel–coated plates in complete medium. These comprehensive analyses revealed that porcine decellularized nerve matrix hydrogel attenuated the activation of excessive inflammation at the early stage of peripheral nerve injury and increased the proportion of the M2 subtype in monocytes/macrophages. Additionally, porcine decellularized nerve matrix hydrogel negatively regulated the Toll-like receptor 4/myeloid differentiation factor 88/nuclear factor-κB axis both in vivo and in vitro. Our findings suggest that the efficacious anti-inflammatory properties of porcine decellularized nerve matrix hydrogel induce M2 macrophage polarization via suppression of the Toll-like receptor 4/myeloid differentiation factor 88/nuclear factor-?B pathway, providing new insights into the therapeutic mechanism of porcine decellularized nerve matrix hydrogel in peripheral nerve injury.

The epidermal growth factor receptor inhibitor gefitinib enhances in vitro and in vivo sensory axon regeneration and functional recovery following transection in a mouse median nerve injury model.

The epidermal growth factor receptor (EGFR; ErbB1), a membrane bound receptor tyrosine kinase, is hypothesized to have an inhibitory influence on peripheral nerve regeneration. This study examines the impact of EGFR inhibition on nerve regeneration using the commercially available small molecule inhibitor gefitinib. In vitro assays included neurite outgrowth of cultured dorsal root ganglion (DRG) neurons from adult C57Bl/6 wildtype mice on immobilized chondroitin sulfate proteoglycans (CSPG). Following forelimb median nerve injury, EGFR expression, number of regenerated neurons (using retrograde labeling) and myelination of motor and sensory neurons were compared between mice that received either gefitinib or vehicle. Functional recovery was assessed using grip strength. EGFR expression on DRG and spinal motor neurons was confirmed. Gefitinib significantly increased neurite outgrowth in medium sized (30-50 μm) DRG neurons, resulting in longer neurites (183 ± 36 μm) compared with CSPG alone (49 ± 9 μm). After median nerve injury, significantly greater numbers of sensory neurons (638 ± 112 vs. 301 ± 81), but not motor neurons (31 ± 12 vs. 42 ± 13) regenerated in animals treated with gefitinib compared with controls. Regenerated axons in gefitinib treated animals displayed significantly greater diameter and increased g-ratio compared with controls. Grip strength recovered more quickly in animals receiving gefitinib compared with controls (27.6 vs. 19.1 g 18 days post-injury). This study provides data supporting the role of EGFR as a negative regulator of sensory but not motor neuron regeneration. Further, it demonstrates versatile potential uses of existing pharmaceuticals.

Epineural Scarring Visualization and Noninvasive Quantification of a Severe Posttraumatic Complication: An Experimental Magnetic Resonance Neurography Study.

Peripheral nerve scarring is a severe yet common complication following nerve injury or surgery that can lead to impaired nerve function, including chronic pain and sensory or motor deficits. In this study, we aimed to establish high-resolution magnetic resonance neurography (MRN) to accurately visualize and monitor de novo-formed epineural fibrotic adhesions (EFAs) of the sciatic nerve in a rat nerve injury model. Employing an established model to induce overshooting EFA, the study included 3 experimental groups of animals (n = 6 each): a positive control group (PC), an intervention group (IG), and a sham group. All groups underwent surgical nerve exposure: both PC and IG received an application of 10 μL 2.5% glutaraldehyde to induce EFA, but only IG received an additional preventive wrapping of the nerve with a collagen-containing matrix. Magnetic resonance imaging was performed 6, 8, and 12 weeks postoperatively using a standardized protocol including T2w and T1w without and with contrast media. Motor function and nerve regeneration was assessed using the visual static sciatic index. Histological specimens were obtained 12 weeks postoperatively and correlated with imaging. On high-resolution MRN, prominently contrast-enhancing epineural sleeves were present in vivo, which corresponded to histologically confirmed EFA (ratio of EFA to nerve area MRN 1.512 ± 0.106 vs histological ratio 1.459 ± 0.208, nonsignificant). As expected, average EFA in IG (0.310 ± 0.118 mm2) was smaller than in PC (0.909 ± 0.212 mm2, P < 0.01). Also, the average EFA in sham (0.386 ± 0.030 mm2) was less pronounced than in PC (P < 0.01). There was no significant difference in the average EFA between IG und sham. The EFA correlated with the functional outcome, which was measured by visual static sciatic index (correlation coefficient -0.59, P < 0.05). The results of the present study for the first time confirm the clinical observation that epineural thickening on contrast-enhanced T1w imaging following manipulation to a nerve indeed corresponds to overshooting epineural scarring, which may be linked to impaired nerve function. This can be followed noninvasively in vivo over time providing an important basis for clinical decision-making in cases where further invasive therapies may be necessary.

A nanofibrous polycaprolactone/collagen neural guidance channel filled with sciatic allogeneic schwann cells and platelet-rich plasma for sciatic nerve repair.

Sciatic nerve damage, a common condition affecting approximately 2.8% of the US population, can lead to significant disability due to impaired nerve signal transmission, resulting in loss of sensation and motor function in the lower extremities. In this study, a neural guidance channel was developed by rolling a nanofibrous scaffold produced via electrospinning. The scaffold's microstructure, biocompatibility, biodegradation rate, porosity, mechanical properties, and hemocompatibility were evaluated. Platelet-rich plasma (PRP) activated with 30,000 allogeneic Schwann cells (SCs) was injected into the lumen of the channels following implantation into a rat model of sciatic nerve injury. Recovery of motor function, sensory function, and muscle re-innervation was assessed using the sciatic function index (SFI), hot plate latency time, and gastrocnemius muscle wet weight loss. Results showed mean hot plate latency times of Autograft: 7.03, PCL/collagen scaffolds loaded with PRP and SCs (PCLCOLPRPSCs): 8.34, polymer-only scaffolds (PCLCOL): 10.66, and untreated animals (Negative Control): 12.00. The mean SFI values at week eight were Autograft: -49.30, PCLCOLPRPSCs: -64.29, PCLCOL: -75.62, and Negative Control: -77.14. The PCLCOLPRPSCs group showed a more negative SFI compared to the Autograft group but performed better than both the PCLCOL and Negative Control groups. These findings suggest that the developed strategy enhanced sensory and functional recovery compared to the negative control and polymer-only scaffold groups.

Effectiveness of the injectable hyaluronic acid-based microparticles loaded with cannabidiol on rat sciatic nerve injury model

Effectiveness of the injectable hyaluronic acid-based microparticles loaded with cannabidiol on rat sciatic nerve injury model

Unraveling Neurotoxicity Discrepancies: Comparative In vitro and In vivo Analysis of Colistin and Polymyxin B and the Underlying Mechanisms.

Polymyxins, including colistin and polymyxin B, are the final resort against Gram-negative bacterial infections. However, its clinical application is restricted due to concerns related to neurotoxicity. Despite the similar antibacterial spectrum and mode of action shared between colistin and polymyxin B, there is still a lack of definitive evidence to support the idea that their neurotoxicity profiles are identical. To comprehensively compare the neurotoxicity between colistin and polymyxin B both in vivo and in vitro and establish a theoretical foundation to guide the rational use of polymyxins within clinical settings. in vitro experiments simulated nerve damage by exposing N2a and RSC96 cells to colistin and polymyxin B. The evaluation of nerve injury included assessments of cell viability and apoptosis. To discern the variance in the mechanisms of nerve injury between colistin and polymyxin B, oxidative stress levels were examined, such as SOD, CAT, GSH, and malondialdehyde (MDA). In in vivo experiments, a rat nerve injury model was created by intraventricular injections of colistin and polymyxin B, respectively. The impact of these drugs on brain injury in rats, particularly within the hippocampus and medulla oblongata, was measured using HE and Nissl staining. The potential influence of polymyxins on the ferroptosis pathway was evaluated by assessing LPO and Fe2+ levels and the degree of mitochondrial impairment. At equivalent doses, colistin demonstrated a reduced level of neurotoxicity compared to polymyxin B, both in vitro and in vivo. in vitro experiments revealed greater cell viability and a lower apoptosis rate after colistin treatment than after polymyxin B treatment. This variance in outcomes could be attributed to the comparatively lower levels of oxidative stress associated with colistin administration.In a rat model, nerve injury resulted in observable damage to both the hippocampus and the medulla oblongata. A comprehensive assessment of the extent of damage in the CA1 to CA4 regions of the hippocampus, and the solitary tract nucleus of the medulla oblongata underscored that the neurotoxic effects of colistin remained milder compared to those elicited by polymyxin B. Even when evaluated at equivalent multiples of clinically recommended doses, colistin exhibited lower neurotoxicity in vivo than polymyxin B. For the first time, this study demonstrated the role of ferroptosis in polymyxin B-induced nerve damage. The activation levels observed within the ferroptosis pathway due to polymyxin B exceeded those triggered by colistin. Colistin exhibited a marked reduction in neurotoxicity compared to polymyxin B, evident in both the equivalent and clinically recommended doses. These findings suggest that, from the perspective of neurotoxicity, colistin presents a more favorable option for clinical use.

MicroRNA Profile Changes in Brain, Cerebrospinal Fluid, and Blood Following Low-Level Repeated Blast Exposure in a Rat Model.

It is well documented that service members are exposed to repeated low-level blast overpressure during training with heavy weapons such as artillery, mortars and explosive breaching. Often, acute symptoms associated with these exposures are transient but cumulative effect of low-level repeated blast exposures (RBEs) can include persistent deficits in cognitive and behavioral health. Thus far, reliable diagnostic biomarkers which can guide countermeasure strategies have not been identified. In this study, rats were exposed to multiple field-relevant blast waves with 8.5 and 10 psi peak positive overpressures, applying one exposure per day for 14 consecutive days. micro-RNAs that can potentially be used as biomarkers for RBEs were assessed in blood, brain, and cerebrospinal fluid (CSF). RBE caused a differential pattern of changes in various miRNAs in blood, brain and CSF in an overpressure-dependent manner. Our key outcomes were decrease of mir-6215 and let-7 family miRNAs and increase of mir-6321 and mir-222-5p in brain, blood, and CSF. Expression pattern of these miRNAs is in concurrence with various neurological conditions such as upregulation of mir-6321 in focal ischemic injury and downregulation of mir-6215 in nerve injury model. Contrarily, Let-7 family miRNAs have neuroprotective role and their downregulation suggests progression of blast induced traumatic brain injury (bTBI) with RBE at 14× -8.5 psi. Repeated blast caused alterations in miRNAs that are likely involved in vascular integrity, inflammation, and cell death. These results indicate that miRNAs are differentially dysregulated in response to blast injuries and may represent better prognostic and diagnostic biomarkers than traditional molecules to identify blast-specific brain injury.

Full-Field Electroretinogram Responses in Rodent Models of Ganglion Cell Injury.

Preclinical studies of optic nerve injury models have led to significant insight into the mechanism underlying retinal ganglion cell neurodegeneration. During the process of ganglion cell injury, morphological changes can occur prior to gross structural changes and cell death. Similarly, following injury, functional changes can occur in the absence of substantive structural changes. These more subtle effects can often be detected using functional tools such as the electroretinogram. Moreover, the electroretinogram is a sensitive and complementary means to quantify treatment efficacy. Here, we describe in vivo electroretinography for assessing ganglion cell injury in rodent models.

Toll-Like Receptor 4 (TLR4) Promotes DRG Regeneration and Repair after Sciatic Nerve Injury via the ERK-NF-kB Pathway.

Previously, we found that the expression of Toll-like receptor 4 (TLR4) is altered after sciatic nerve injury, and its differential expression plays a key role in recovery. However, the mechanisms by which TLR4 affects neuronal function in the dorsal root ganglion (DRG) have not been completely evaluated. The objective is to determine TLR4 expression in DRG tissues after sciatic neural injury and exploring the effects of TLR4 knockdown and overexpression in the DRG on neuronal function and nerve regeneration in rats in vivo and in vitro. We established a model of nerve injury and utilized molecular biology and cell biology experiments to explore the molecular mechanisms by which TLR4 in the DRG affects sciatic nerve restoration and regeneration after injury. Verified the localization of TLR4 in DRG neurons. Investigated pathways that related to apoptosis or nerve regeneration by which TLR4 regulates the function of DRG neurons. TLR4 expression was upregulated in the DRG tissues of rats after sciatic nerve injury. TLR4 overexpression promoted axon regeneration and inhibited apoptosis in DRG neurons. TLR4 promoted the regeneration of axons and the recovery of motor and sensory functions in the sciatic nerve after injury in vivo, and the data showed that TLR4 may regulate the function of DRG neurons and promote nerve repair and regeneration through the ERK and NF-κB signaling pathways in vivo and ex vivo. The study suggests that TLR4 may regulate the function of DRG neurons and promote nerve regeneration by affecting the ERK and NF-κB signaling pathways.

A microfluidic model of the first sensory synapse for analgesic target discovery.

The synaptic connections between dorsal root ganglia (DRG) and dorsal horn (DH) neurons are a crucial relay point for the transmission of painful stimuli. To delineate how synaptic plasticity may modulate the excitability of DH neurons, we have devised a microfluidic co-culture model that recapitulates the first sensory synapse using postnatal mouse sensory neurons. We show that DRG-DH co-cultures characterize salient features of the in vivo physiology of sensory neurons. Immunocytcochemical experiments of the cultured DH neurons show a co-localization of MAP2 with VGLUT2 and of MAP2 with Synapsin 1, corroborating the glutamatergic identity of the DH neurons and further suggesting the formation of active synapses in this neuronal set. Fluorometric imaging experiments demonstrate the elicitation of calcium responses in DH neurons following the stimulation of DRG cell bodies or axons. Selective NMDA and AMPA receptor blockade appreciably silences DH neuron responses, suggesting that glutamatergic signaling is maintained in vitro. Last, a surrogate model of peripheral nerve injury is introduced in the form of an axotomy, which results in elevated and prolonged calcium responses of DH neurons. Overall, the microfluidic mouse co-cultures provide a method advancement in the study of periphery-to-center pain signaling, where the potential of utilizing the platform for drug target identification is underscored.

Small-molecule natural product sophoricoside reduces peripheral neuropathic pain via directly blocking of NaV1.6 in dorsal root ganglion nociceptive neurons.

Peripheral neuropathic pain poses a significant global health challenge. Current drugs for peripheral neuropathic pain often fall short in efficacy or come with severe side effects, emphasizing the critical need for the development of highly effective and well-tolerated alternatives. Sophoricoside (SOP) is a nature product-derived isoflavone that possesses various pharmacological effects on inflammatory and neuropathy diseases. Here, in this study, analgesic effect was investigated by intrathecally administration of SOP/vehicle to spared nerve injury (SNI) or paclitaxel-induced peripheral neuropathic pain (PINP) rodent models, and mechanical allodynia was measured in Von Frey tests. Ipsilateral L4-L6 dorsal root ganglia (DRG) were used for protein expression. In silico molecular docking analysis was applied for assessing compound-target binding affinity. Primary cultured DRG neurons were utilized to investigate SOP's effect on veratridine-triggered nociceptor activities and its selective inhibition of voltage-gated sodium channels subtype 1.6 (NaV1.6). The results showed SOP treatment alleviated mechanical allodynia in SNI and PINP rodent models (paw withdrawal threshold after 1 h of injection: SNI-vehicle: 1.385 ± 0.338 g; SNI-SOP: 9.963 ± 2.029 g, P < 0.001; PINP-vehicle: 5.040 ± 0.985 g; PINP-SOP: 8.287 ± 3.812 g, P = 0.004). SOP presented effects on both inhibiting veratridine-triggered nociceptor activities (oscillatory population: vehicle: 39.9 ± 7.3%; SOP: 30.7 ± 9.8%, P = 0.021) and selectively blocking NaV1.6 in DRG sensory neurons. Molecular docking analysis indicated direct binding between SOP and NaV1.6, leading to its endocytosis in DRG Sensory Neurons. In conclusion, SOP alleviated nociceptive allodynia induced by peripheral nerve injury via selectively blocking of NaV1.6 in DRG nociceptive neurons. we highlight its potential as an analgesic and elucidate its mechanism involving NaV1.6 endocytosis. This research opens avenues for exploring the analgesic effects of SOP and its potential impact on neuropathic pain therapy.

Differential evaluation of neuromuscular injuries to understand re-innervation at the neuromuscular junction

Peripheral nerve-crush injury is a well-established model of neuromuscular junction (NMJ) denervation and subsequent re-innervation. Functionally, the skeletal muscle follows a similar pattern as neural recovery, with immediate loss of force production that steadily improves in parallel with rates of re-innervation. On the other hand, traumatic injury to the muscle itself, specifically volumetric muscle loss (VML), results in an irrecoverable loss of muscle function. Recent work has indicated significant impairments to the NMJ following this injury that appear chronic in nature, alongside the lack of functional recovery. Thus, the goal of this study was to compare the effects of nerve and muscle injury on NMJ remodeling. Even numbers of adult male and female mice were used with three experimental groups: injury Naïve, nerve crush, and VML injury; and three terminal timepoints: 3-, 48-, and 112-days post-injury. Confirming the assumed recoverability of the two injury models, we found in vivo maximal torque was fully restored following nerve-crush injury but remained at a significant deficit following VML. Compared to injury Naïve and nerve-crush injury, we found VML results in aberrantly high trophic signaling (e.g., neuregulin-1) and numbers of supporting cells, including terminal Schwann cells and sub-synaptic nuclei. In some cases, sex differences were detected, including higher rates of innervation in females than males. Both nerve crush and VML injury display chronic changes to NMJ morphology, such as increased fragmentation and nerve sprouting, highlighting the potential of VML for modeling NMJ regeneration in adulthood, alongside the established nerve-injury models.

Addition of Ostrea rivularis polysaccharides in microneedle loaded with 3-acetylaconitine liposomes enhance analgesic activities and drug delivery properties.

3-Acetylaconitine (AAC) is a natural compound with strong anti-inflammatory and analgesic properties, but the severely narrow safety range limited its clinical application. Two dissolvable microneedle (MN) systems, AAC-ORP-MN and AAC-MN, loaded with AAC liposomes (AAC-Lips) either mixed with or without Ostrea rivularis polysaccharide (ORP) were developed. The size, zeta potential and encapsulation efficiency of AAC-Lips were 112.9 ± 0.5 nm, -31.3 ± 0.5 mV and 95.7 ± 1.2 %. AAC-ORP-MN demonstrated higher mechanical strength and faster initial drug release rate compared to AAC-MN. The results in the spared nerve injury (SNI) model showed that AAC-ORP-MN and AAC-MN both could significantly increase the mechanical pain threshold on the operated side of the rats, and gradually decrease the difference between the equilibrium pain thresholds of both feet, but AAC-ORP-MN showed a faster onset of action. In addition, AAC-ORP-MN significantly reduced inflammatory factors and improved pathological damage in the spinal cord better than AAC-MN, which might be due to the anti-inflammatory activity of ORP. Overall, the above results supported that AAC-ORP-MN showed promise as a clinical option for analgesia, which had anti-inflammatory and analgesic properties, meanwhile it could effectively deliver poorly water-soluble AAC and improve its safety and availability.

The analgesic effect and mechanism of the active components screening from Corydalis yanhusuo by P2X3 receptors

Ethnopharmacological relevanceCavidine (CAV) is the main bioactive ingredient of Corydalis ternata f. yanhusuo (Y.H.Chou & Chun C.Hsu) Y.C.Zhu, which is a traditional Chinese herbal containing a variety of uses such as analgesic, anticancer, and anti-inflammatory properties. Aim of the studyThe goal is to screen Corydalis yanhusuo for anti-central sensitization active components and investigate and clarify the pharmacological mechanism and therapeutic efficacy of the active ingredient CAV in the treatment of chronic pain. Material and MethodsFirst, cell membrane immobilized chromatography was used to screen the bioactive ingredients in Corydalis yanhusuo. Spare nerve injury (SNI) model and complete Freund's adjuvant (CFA) mice model were constructed to identify the analgesic effect of CAV. RNA-seq and bioinformatics analyses were used to explore the potential targets of CAV in CFA mice and SNI mice. HE staining was used to observe the infiltration of inflammatory cells in the dorsal root ganglion (DRG) and spinal cord(SC) of CFA mice and SNI mice. WB and qPCR were used to detect the level of inflammatory factors TNF-α, IL-1β, and IL-6 in DRG and SC of mice. SNI and CFA mice were used to study the effect and mechanism of CAV on microglial activation. Results9 potential active ingredients were screened out from Corydalis yanhusuo that can regulate P2X3 receptors. CAV showed good analgesic effects, increased the mechanical pain and thermal pain thresholds of CFA mice and SNI mice, inhibited the expression of DRG and SC inflammatory factors, downregulated IBA-1, and inhibited microglial activation. Further in vivo and in vitro experiments showed that CAV significantly inhibited the expression of P2X3 receptors and the activation of its downstream MAPK pathway in DRG neurons and SC. ConclusionThis study is the first to indicate that CAV exerts an analgesic effect by inhibiting microglia activation via the P2X3 signaling pathway axis, providing the clinical utility of CAV in chronic pain therapy.

ID: 323663 Transcriptomics of the L5-DRG after SCS in the Rat Spared Nerve Injury Model

ID: 323663 Transcriptomics of the L5-DRG after SCS in the Rat Spared Nerve Injury Model

ID: 326198 Chronically Recorded Spinal ECAP Thresholds in Rats in the Spared Nerve Injury Model

ID: 326198 Chronically Recorded Spinal ECAP Thresholds in Rats in the Spared Nerve Injury Model

Spared ulnar nerve injury results in increased layer III–VI excitability in the pig somatosensory cortex

This study describes cortical recordings in a large animal nerve injury model. We investigated differences in primary somatosensory cortex (S1) hyperexcitability when stimulating injured and uninjured nerves and how different cortical layers contribute to S1 hyperexcitability after spared ulnar nerve injury. We used a multielectrode array to record single-neuron activity in the S1 of ten female Danish landrace pigs. Electrical stimulation of the injured and uninjured nerve evoked brain activity up to 3 h after injury. The peak amplitude and latency of early and late peristimulus time histogram responses were extracted for statistical analysis. Histological investigations determined the layer of the cortex in which each electrode contact was placed. Nerve injury increased the early peak amplitude compared with that of the control group. This difference was significant immediately after nerve injury when the uninjured nerve was stimulated, while it was delayed for the injured nerve. The amplitude of the early peak was increased in layers III–VI after nerve injury compared with the control. In layer III, S1 excitability was also increased compared with preinjury for the early peak. Furthermore, the late peak was significantly larger in layer III than in the other layers in the intervention and control group before and after injury. Thus, the most prominent increase in excitability occurred in layer III, which is responsible for the gain modulation of cortical output through layer V. Therefore, layer III neurons seem to have an important role in altered brain excitability after nerve injury.

Inflammatory pain resolution by mouse serum-derived small extracellular vesicles

Current treatments for chronic pain have limited efficacy and significant side effects, warranting research on alternative strategies for pain management. One approach involves using small extracellular vesicles (sEVs), or exosomes, to transport beneficial biomolecular cargo to aid pain resolution. Exosomes are 30–150 nm sEVs that can be beneficial or harmful depending on their source and cargo composition. We report a comprehensive multi-modal analysis of different aspects of sEV characterization, miRNAs, and protein markers across sEV sources. To investigate the short- and long-term effects of mouse serum-derived sEVs in pain modulation, sEVs from naïve control or spared nerve injury (SNI) model male donor mice were injected intrathecally into naïve male recipient mice. These sEVs transiently increased basal mechanical thresholds, an effect mediated by opioid signaling as this outcome was blocked by naltrexone. Mass spectrometry of sEVs detected endogenous opioid peptide leu-enkephalin. sEVs from naïve female mice have higher levels of leu-enkephalin compared to male, matching the analgesic onset of leu-enkephalin in male recipient mice. In investigating the long-term effect of sEVs, we observed that a single prophylactic intrathecal injection of sEVs two weeks prior to induction of the pain model in recipient mice accelerated recovery from inflammatory pain after complete Freund’s adjuvant (CFA) injection. Our exploratory studies examining immune cell populations in spinal cord and dorsal root ganglion using ChipCytometry suggested alterations in immune cell populations 14 days post-CFA. Flow cytometry confirmed increases in CD206+ macrophages in the spinal cord in sEV-treated mice. Collectively, these studies demonstrate multiple mechanisms by which sEVs can attenuate pain.

Electroacupuncture alleviates sciatic nerve injury and inhibits autophagy in rats.

Sciatic nerve injury is a common form of peripheral nerve injury (PNI). It has been suggested that electroacupuncture (EA) stimulation at GB30 and ST36 can improve nerve dysfunction post-PNI. Autophagy is an important factor in the regeneration of sciatic nerves and recovery of motor function. Therefore, we investigated the biological effects of EA and examined whether these were mediated by autophagy in sciatic nerve injury. Mechanical clamping of the sciatic nerve in Sprague-Dawley rats was performed to establish an experimental model of sciatic nerve injury. EA stimulation was administered once daily for 15 min for seven consecutive days beginning 1 week after successful modeling. The recovery of sciatic nerve function was examined via the sciatic functional index (SFI) test. Morphometric analysis was conducted by staining nerve samples with toluidine blue. Autophagy-associated protein levels were measured via Western blotting. EA stimulation at GB30 and ST36 significantly increased the number of myelinated fibers, axonal and fiber diameters, and the thickness of the myelin sheath in our rat model of sciatic nerve injury. In addition, EA stimulation greatly facilitated nerve regeneration following sciatic nerve injury. Moreover, sciatic nerve injury-induced autophagy was inhibited by EA stimulation. EA facilitates recovery of injured sciatic nerves and inhibits autophagy in a rat model.