Search Results (62)

Contactin-associated protein-like 2 (CASPR2) is a transmembrane protein of the neurexin superfamily, essential for clustering voltage-gated potassium channels, particularly Kv1, at the juxtaparanodal regions of myelinated axons. This precise localisation is essential for maintaining normal axonal excitability and preventing aberrant signal propagation. Autoantibodies targeting CASPR2 have been associated with various neurological syndromes, notably peripheral nerve hyperexcitability (PNH), which presents clinically with neuromyotonia and myokymia. PNH is characterised by distinctive electrophysiological findings, including neuromyotonic discharges, myokymic discharges, and afterdischarges, which provide diagnostic value and insight into underlying pathophysiology. This review explores the mechanisms of anti-CASPR2-associated PNH, focusing on how antibody-mediated disruption of Kv1 channel clustering leads to altered axonal excitability. Current evidence suggests that both the distal and proximal segments of the axon are sites of pathological activity, where impairments in action potential termination and re-entry prevention result in spontaneous, repetitive discharges. While afterdischarges likely originate within the axon, the precise location—whether in the alpha-motoneuron soma or axon—is uncertain. The involvement of spinal inhibitory circuits has also been proposed, though it remains speculative. Understanding the neurophysiological features of anti-CASPR2-associated PNH is essential for improving diagnostic accuracy and guiding treatment strategies. Further research is needed to clarify the mechanisms of CASPR2-related hyperexcitability. Full article

Tissue engineering has the potential to overcome the limitations of using autografts in nerve gap repair, using cellular biomaterials to bridge the gap and support neuronal regeneration. Various types of therapeutic cells could be considered for use in aligned collagen-based engineered neural tissue (EngNT), including Schwann cells and their precursors, which can be derived from human induced pluripotent stem cells (hiPSCs). Using Schwann cell precursors may have practical advantages over mature Schwann cells as they expand readily in vitro and involve a shorter differentiation period. However, the performance of each cell type needs to be tested in EngNT. By adapting established protocols, hiPSCs were differentiated into Schwann cell precursors and Schwann cells, with distinctive molecular profiles confirmed using immunocytochemistry and RT-qPCR. For the first time, both cell types were incorporated into EngNT using gel aspiration–ejection, a technique used to align and simultaneously stabilise the cellular hydrogels. Both types of cellular constructs supported and guided aligned neurite outgrowth from adult rat dorsal root ganglion neurons in vitro. Initial experiments in a rat model of nerve gap injury demonstrated the extent to which the engrafted cells survived after 2 weeks and indicated that both types of hiPSC-derived cells supported the infiltration of host neurons, Schwann cells and endothelial cells. In summary, we show that human Schwann cell precursors promote infiltrating endogenous axons in a model of peripheral nerve injury to a greater degree than their terminally differentiated Schwann cell counterparts. Full article

The agents of prion diseases have the capacity to efficiently infect susceptible hosts by peripheral routes and to project to clinical target areas of the central nervous system (CNS) via peripheral nerves. Understanding the process of prion spread from the site of infection to the CNS may allow us to identify novel therapeutic strategies. To investigate the mechanism involved in the intranerval transit of 263K scrapie prions in golden Syrian hamsters (GSHs), we transected the sciatic nerve at increasing times post-footpad injection and recorded the incubation periods as estimates of the efficiency of infection. We calculated that intranerval transit of this strain of scrapie is at least 10 times faster than previously reported and may reach 50 mm/day, similar to other neurotropic viruses. By in vivo exposure/injection of sciatic nerves to 263K infectivity, we have also shown that prion entry likely occurs via nerve terminals rather than by direct contact with the sciatic nerve. Application of this experimental approach in other forms of prion diseases could allow verification of the timing of neuroinvasion, a relevant parameter for the definition of therapeutic interventions. Full article

Objective: Given the side effects and reduced efficacy of conventional local anesthetics in inflammatory conditions, there is a compelling need for complementary alternative medicine (CAM), particularly those based on phytochemicals. While a previous study showed that in vivo local injection of (-)-epigallocatechin-3-gallate (EGCG) into the peripheral receptive field suppresses the excitability of rat trigeminal ganglion (TG) neurons in the absence of inflammation, the acute effects of EGCG in vivo, especially on TG neurons under inflammatory conditions, are still unknown. We aimed to determine if acute local EGCG administration into inflamed tissue effectively attenuates the excitability of nociceptive TG neurons evoked by mechanical stimulation. Methods: The escape reflex threshold was measured to assess hyperalgesia caused by complete Freund’s adjuvant (CFA)-induced inflammation. To assess neuronal activity, extracellular single-unit recordings were performed on TG neurons in anesthetized CFA-inflamed rats in response to orofacial mechanical stimulation. Results: The mechanical escape threshold was significantly lower in CFA-inflamed rats compared to before CFA injection. EGCG (1–10 mM) reversibly and dose-dependently inhibited the mean firing frequency of TG neurons evoked by both non-noxious and noxious mechanical stimuli (p < 0.05). For comparison, 1% lidocaine (37 mM), a local anesthetic, also caused reversible inhibition of the mean firing frequency in inflamed TG neurons responding to mechanical stimuli. Importantly, 10 mM EGCG produced a significantly greater magnitude of inhibition on TG neuronal discharge frequency than 1% lidocaine (noxious, lidocaine vs. EGCG, 19.7 ± 3.3% vs. 42.3 ± 3.4%, p < 0.05). Conclusions: Local injection of EGCG into inflamed tissue effectively suppresses the excitability of nociceptive primary sensory TG neurons, as indicated by these findings. Significantly, locally administered EGCG exerted a more potent local analgesic action compared to conventional voltage-gated sodium channel blockers. This heightened efficacy originates from EGCG’s ability to inhibit both generator potentials and action potentials directly at nociceptive primary nerve terminals. As a result, EGCG stands out as a compelling candidate for novel analgesic development, holding particular relevance for CAM strategies. Full article

Background: The brachial plexus is a network of nerves responsible for the motor and sensory innervation of the upper limb. Variations in the formation and course of the brachial plexus are well documented, though combinations of multiple unilateral abnormalities are rare. The complex pathology of this structure nerve may result in clinical consequences. We present a unique set of brachial plexus abnormalities involving the C4–C6 nerve roots, superior and middle trunks, additional communicating branches, and delayed median nerve union. Case Presentation: During the routine dissection of a 70-year-old female cadaver, several unique variations in the brachial plexus anatomy were identified. The C4 root contributed to C5 before the superior trunk formed, resulting in a superior trunk composed of C4–C6. The C5 root was located anterior to the anterior scalene muscle, whereas C6 maintained its usual posterior position. Additionally, an anterior communicating branch from the middle trunk to the posterior cord was observed. A communicating branch between the lateral and medial cords split into two terminal branches: one merged with the ulnar nerve, and the other joined the medial contribution of the median nerve. The median nerve contributions from the lateral and medial cords merged approximately two inches above the elbow. Conclusions: This rare combination of brachial plexus anomalies has not been previously described in the literature and is of significant clinical relevance. The additional anterior communicating branch from the middle trunk may suggest potential flexor muscle innervation by the posterior cord, which typically innervates extensor muscles. Additionally, the delayed convergence of the median nerve may provide a protective mechanism in cases of midshaft humeral fracture. Awareness of these peripheral nerve abnormalities is important for diagnostic imaging, surgery, or peripheral nerve blocks. Knowledge of such variations is critical for clinicians managing upper limb pathologies. Full article

In veterinary medicine, the diagnosis of peripheral neuropathies is currently performed using semithin sections or nerve fiber teasing from nerve biopsy. However, these methods actually fail to identify more specific length-dependent and somatosensitive neuropathies. In humans, skin punch biopsy is used to diagnose the latter, through the identification and count of intraepidermal nerve fibers (IENFs) crossing the dermal–epidermal junction, with indirect immunofluorescence (IIF). However, the current need for frozen samples for this technique limits its routine application in clinical practice. In this study, we set up an IIF protocol to identify IENFs in dogs’ skin punch biopsies. Six tests were performed on canine formalin-fixed paraffin-embedded (FFPE) 8 mm skin punches, using an antibody anti-PGP9.5, also known as ubiquitin carboxyl-terminal hydrolase-1. Three parameters were checked: (1) the effectiveness of the co-localization immunoreaction, (2) the thickness of sections, and (3) the magnification for image acquisition. The best IIF results in terms of the sharpness of fiber visualization and the possibility to count them were obtained with 10 µm sections, with a high-power field (×40), without co-localization for nuclei and epithelial structures. Reference data concerning the IENF density of different skin regions in healthy animals of different ages remain to be defined for future diagnostic applications. Full article

Pain, or the ability to feel pain and express the unpleasantness caused by peripheral injuries, are functions of the central nervous system. From peripheral sensory nerve terminals to certain cortical regions of the brain, activation of related neural networks underlies the sensory process. Recently, our knowledge of pain has been increasing dramatically, due to the advancement of scientific approaches. We no longer see the brain as a random matrix for pain but, rather, we are able to identify the step-by-step selective signaling proteins, neurons, and networks that preferentially contribute to the process of chronic pain and its related negative emotions, like anxiety and fear. However, there is still lacking the selective and effective drugs and methods for the treatment of chronic pain clinically. While first-line drugs for acute pain and mental diseases are also applied for the clinical management of chronic pain, their prolonged usage always causes serious side effects. In this short review, we will update and summarize the recent progress in this field and mainly focus on the roles of neural networks and synaptic mechanisms in chronic neuropathic pain. Furthermore, potential drug targets (such as plasticity-related signaling molecules, ionic channels, cytokines, and neuropeptides) and methods for the management of chronic neuropathic pain will be discussed as well. We hope this review can provide new, valuable insight into the treatment of chronic neuropathic pain. Full article

Background: In eukaryotes with a double-stranded linear DNA genome, the loss of terminal DNA during replication is inevitable due to an end-replication problem; here, telomeres serve as a buffer against DNA loss. Thus, the activation of the telomere maintenance mechanism (TMM) is a prerequisite for malignant transformation. Methods: We compared neurofibroma (NF, benign) and malignant peripheral nerve sheath tumors (MPNSTs) occurring in the same patient with type 1 neurofibromatosis, where each NF–MPNST pair shared the same genetic background and differentiation lineage; this minimizes the genetic bias and contrasts only those changes that are related to malignant transformation. A total of 20 NF–MPNST pairs from 20 NF1 patients were analyzed. Whole-transcriptome sequencing (WTS) was conducted to profile the transcriptional relationship, and whole-genome sequencing (WGS) was performed to measure the telomere length. Results: We identified 22 differentially expressed genes (DEGs) during the malignant transformation of MPNSTs. Among them, NELL2 activated PAX7, which sequentially activated RAD52, the recombinase of RAD52-dependent alternative lengthening of telomeres (ALT). RAD52 elongated MPNSTs–telomeres (p = 0.017). Otherwise, neither NELL2 nor PAX7 affected telomere length (p = 0.647 and p = 0.354, respectively). RAD52 increased MPNSTs–telomeres length, independently of NELL2 and PAX7 in multiple analyses (p = 0.021). The group with increased telomere length during the malignant transformation showed inferior overall survival (OS) (HR = 3.809, p = 0.038) to the group without increased telomere length. Accordingly, the group with increased PAX7 showed inferior OS (HR = 4.896, p = 0.046) and metastasis-free survival (MFS) (HR = 9.129, p = 0.007) in comparison to the group without increased PAX7; the group with increased RAD52 showed inferior MFS (HR = 8.669, p = 0.011) in comparison to the group without increased RAD52. Conclusions: We suggest that the NELL2-PAX7 transcriptional cascade activates RAD52-dependent ALT to increase telomere length during the malignant transformation of MPNSTs, resulting in a poor prognosis. Full article

Nociceptive information is transmitted by action potentials (APs) through primary afferent neurons from the periphery to the central nervous system. Voltage-gated Na⁺ channels are involved in this AP production, while transient receptor potential (TRP) channels, which are non-selective cation channels, are involved in receiving and transmitting nociceptive stimuli in the peripheral and central terminals of the primary afferent neurons. Peripheral terminal TRP vanilloid-1 (TRPV1), ankylin-1 (TRPA1) and melastatin-8 (TRPM8) activation produces APs, while central terminal TRP activation enhances the spontaneous release of L-glutamate from the terminal to spinal cord and brain stem lamina II neurons that play a pivotal role in modulating nociceptive transmission. There is much evidence demonstrating that chemical compounds involved in Na⁺ channel (or nerve AP conduction) inhibition modify TRP channel functions. Among these compounds are local anesthetics, anti-epileptics, α₂-adrenoceptor agonists, antidepressants (all of which are used as analgesic adjuvants), general anesthetics, opioids, non-steroidal anti-inflammatory drugs and plant-derived compounds, many of which are involved in antinociception. This review mentions the modulation of Na⁺ channels and TRP channels including TRPV1, TRPA1 and TRPM8, both of which modulations are produced by pain-related compounds. Full article

Background: The combination of macroporous cryogels with synthetic peptide factors represents a promising but poorly explored strategy for the development of extracellular matrix (ECM)-mimicking scaffolds for peripheral nerve (PN) repair. Methods: In this study, IKVAV peptide was functionalized with terminal lysine residues to allow its in situ cross-linking with gelatin macromer, resulting in the formation of IKVAV-containing proteinaceous cryogels. The controllable inclusion and distribution of the peptide molecules within the scaffold was verified using a fluorescently labelled peptide counterpart. The optimized cryogel scaffold was combined with polycaprolactone (PCL)-based shell tube to form a suturable nerve conduit (NC) to be implanted into sciatic nerve diastasis in rats. Results: The NC constituents did not impair the viability of primary skin fibroblasts. Concentration-dependent effects of the peptide component on interrelated viscoelastic and swelling properties of the cryogels as well as on proliferation and morphological differentiation of neurogenic PC-12 cells were established, also indicating the existence of an optimal-density range of the introduced peptide. The in vivo implanted NC sustained the connection of the nerve stumps with partial degradation of the PCL tube over eight weeks, whereas the core-filling cryogel profoundly improved local electromyographic recovery and morphological repair of the nerve tissues, confirming the regenerative activity of the developed scaffold. Conclusions: These results provide proof-of-concept for the development of a newly designed PN conduit prototype based on IKVAV-activated cryogel, and they can be exploited to create other ECM-mimicking scaffolds. Full article

Tau is a microtubule-associated protein that plays a vital role in the mammalian nervous system. Alternative splicing of the MAPT gene leads to the formation of tau isoforms with varying N-terminal inserts and microtubule-binding repeats. Dysregulation of tau alternative splicing has been linked to diseases in the central nervous system, but the roles of tau isoforms in the peripheral nervous system remain unclear. Here, we investigated the alternative splicing of tau exons 4A and 10 in the sciatic nerve and Schwann cells during development and following injury. We discovered that low-molecular-weight (LMW) tau, resulting from the exclusion of exon 4A, and 3R tau, generated by the exclusion of exon 10, diminishes with aging in rat sciatic nerve and Schwann cells. High-molecular-weight (HMW) tau and 3R tau increase in the adult sciatic nerve post-injury. We constructed viruses that expressed HMW−4R, LMW−4R, HMW−3R, and LMW−3R and introduced them into cultured cells or the distal part of the injured sciatic nerve to assess their effects on Schwann cell migration and proliferation. We also examined the effects of the four isoforms on axon growth and debris clearance after sciatic nerve injury. Our results demonstrated that tau isoforms inhibit Schwann cell proliferation while promoting Schwann cell migration and sciatic nerve regeneration. Specifically, the 3R−tau isoforms were more effective than the 4R−tau isoforms in promoting nerve regeneration. In conclusion, our study reveals the roles of tau isoforms in the peripheral nervous system and provides insights into the development of new therapeutic strategies for peripheral nerve injuries. Full article

Objectives: Vitamin B complexes are frequently used in clinical practice for peripheral nerve trauma. However, there is a lack of scientific data on their effectiveness. This study aims to investigate the impact of the vitamin B complex on nerve recovery in a rat model of peripheral nerve paralysis. Materials and Methods: Sixty male Wistar Albino rats were divided into six groups. Models of nerve injury, including blunt trauma, nerve incision, and autograft, were performed on all rats approximately 1 cm distal to the sciatic notch. B-complex vitamins were injected intraperitoneally at 0.2 mL/day to the treatment groups. The control groups were given 0.2 mL/day saline. After 1 month, the study was terminated, electromyography (EMG) was performed to measure the conduction velocity, and nerve tissue was taken from the repair line. The sciatic function indexes (SFIs) were calculated and analyzed. The histopathological samples were stained with hematoxylin and eosin and Toluidine blue and examined with a light microscope. Pathologically, myelination, fibrosis, edema, and mast cell densities in the nervous tissue were evaluated. Results: The vitamin B treatment groups demonstrated significant improvements in SFI compared to the control groups, indicating functional improvement in nerve damage (p < 0.05). In the nerve graft group, the vitamin B group showed a shorter latency, higher velocity, and larger peak-to-peak compared to the controls (p < 0.05). In the nerve transection group, the vitamin B group had better latency, velocity, and peak-to-peak values than the controls (p < 0.05). In the crush injury group, the vitamin B group exhibited an improved latency, velocity, and peak-to-peak compared to the controls (p < 0.05). Better myelination, less fibrosis, edema, and mast cells were also in the vitamin B group (p < 0.05). Conclusions: Vitamin B treatment significantly improves nerve healing and function in peripheral nerve injuries. It enhances nerve conduction, reduces fibrosis, and promotes myelination, indicating its therapeutic potential in nerve regeneration. Full article

Glutamate functions as the major excitatory neurotransmitter for primary sensory neurons and has a crucial role in sensitizing peripheral nociceptor terminals producing sensitization. Glutaminase (GLS) is the synthetic enzyme that converts glutamine to glutamate. GLS-immunoreactivity (-ir) and enzyme activity are elevated in dorsal root ganglion (DRG) neuronal cell bodies during chronic peripheral inflammation, but the mechanism for this GLS elevation is yet to be fully characterized. It has been well established that, after nerve growth factor (NGF) binds to its high-affinity receptor tropomyosin receptor kinase A (TrkA), a retrograde signaling endosome is formed. This endosome contains the late endosomal marker Rab7GTPase and is retrogradely transported via axons to the cell soma located in the DRG. This complex is responsible for regulating the transcription of several critical nociceptive genes. Here, we show that this retrograde NGF signaling mediates the expression of GLS in DRG neurons during the process of peripheral inflammation. We disrupted the normal NGF/TrkA signaling in adjuvant-induced arthritic (AIA) Sprague Dawley rats by the pharmacological inhibition of TrkA or blockade of Rab7GTPase, which significantly attenuated the expression of GLS in DRG cell bodies. The results indicate that NGF/TrkA signaling is crucial for the production of glutamate and has a vital role in the development of neurogenic inflammation. In addition, our pain behavioral data suggest that Rab7GTPase can be a potential target for attenuating peripheral inflammatory pain. Full article

Sympathetic nervous system (SNS) hyperactivity is mediated by elevated catecholamine (CA) secretion from the adrenal medulla, as well as enhanced norepinephrine (NE) release from peripheral sympathetic nerve terminals. Adrenal CA production from chromaffin cells is tightly regulated by sympatho-inhibitory α₂-adrenergic (auto)receptors (ARs), which inhibit both epinephrine (Epi) and NE secretion via coupling to Gi/o proteins. α₂-AR function is, in turn, regulated by G protein-coupled receptor (GPCR)-kinases (GRKs), especially GRK2, which phosphorylate and desensitize them, i.e., uncouple them from G proteins. On the other hand, the short-chain free fatty acid (SCFA) receptor (FFAR)-3, also known as GPR41, promotes NE release from sympathetic neurons via the Gi/o-derived free Gβγ-activated phospholipase C (PLC)-β/Ca²⁺ signaling pathway. However, whether it exerts a similar effect in adrenal chromaffin cells is not known at present. In the present study, we examined the interplay of the sympatho-inhibitory α_2A-AR and the sympatho-stimulatory FFAR3 in the regulation of CA secretion from rat adrenal chromaffin (pheochromocytoma) PC12 cells. We show that FFAR3 promotes CA secretion, similarly to what GRK2-dependent α_2A-AR desensitization does. In addition, FFAR3 activation enhances the effect of the physiologic stimulus (acetylcholine) on CA secretion. Importantly, GRK2 blockade to restore α_2A-AR function or the ketone body beta-hydroxybutyrate (BHB or 3-hydroxybutyrate), via FFAR3 antagonism, partially suppress CA production, when applied individually. When combined, however, CA secretion from PC12 cells is profoundly suppressed. Finally, propionate-activated FFAR3 induces leptin and adiponectin secretion from PC12 cells, two important adipokines known to be involved in tissue inflammation, and this effect of FFAR3 is fully blocked by the ketone BHB. In conclusion, SCFAs can promote CA and adipokine secretion from adrenal chromaffin cells via FFAR3 activation, but the metabolite/ketone body BHB can effectively inhibit this action. Full article

The administration of therapeutics to peripheral nerve tissue is challenging due to the complexities of peripheral neuroanatomy and the limitations imposed by the blood–nerve barrier (BNB). Therefore, there is a pressing need to enhance delivery effectiveness and implement targeted delivery methods. Recently, erythrocyte-derived exosomes (Exos) have gained widespread attention as biocompatible vehicles for therapeutics in clinical applications. However, engineering targeted Exos for the peripheral nervous system (PNS) is still challenging. This study aims to develop a targeted Exo delivery system specifically designed for presynaptic terminals of peripheral nerve tissue. The clostridium neurotoxin, tetanus toxin-C fragment (TTC), was tethered to the surface of red blood cell (RBC)-derived Exos via a facile and efficient bio-orthogonal click chemistry method without a catalyst. Additionally, Cyanine5 (Cy5), a reactive fluorescent tag, was also conjugated to track Exo movement in both in vitro and in vivo models. Subsequently, Neuro-2a, a mouse neuronal cell line, was treated with dye-labeled Exos with/without TTC in vitro, and the results indicated that TTC-Exos exhibited more efficient accumulation along the soma and axonal circumference, compared to their unmodified counterparts. Further investigation, using a mouse model, revealed that within 72 h of intramuscular administration, engineered TTC-Exos were successfully transported into the neuromuscular junction and sciatic nerve tissues. These results indicated that TTC played a crucial role in the Exo delivery system, improving the affinity to peripheral nerves. These promising results underscore the potential of using targeted Exo carriers to deliver therapeutics for treating peripheral neuropathies. Full article