Dorsal Root Research Articles

Biomechanical comparison of ultra-high molecular weight polyethylene sutures of different thicknesses of the tensile strength for pullout repair of medial meniscal posterior root tear.

Medial meniscus posterior root tears (MMPRT) are a risk factor for knee osteoarthritis. The predominant treatment for MMPRT is transtibial pullout repair, and loop suture remains the gold standard procedure. This study aimed to investigate the structural properties of the meniscus-suture-tibia (MST) complex after loop stitch using ultra-high molecular weight polyethylene (UHMWPE) suture tape of different thicknesses. This study used 20 fresh porcine MMPRT model knees. All specimens were randomised into two treatment groups: (1) pullout repair using 1.3 mm suture tape (thin group, n = 10; 1.3 mm PERMATAPE, Mitek Sports Medicine) fixation and (2) pullout repair using 2.5 mm suture tape (thick group, n = 10; 2.5 mm PERMATAPE, Mitek Sports Medicine) fixation. The single-loop stitch MS technique was utilised. The MST complex specimens were placed on a tensile tester. The structural properties of the MST complex (yield load, maximum load, liner stiffness, and elongation at failure) were identified. No significant differences were found between the thin and thick groups in terms of maximum load (108.8 ± 49.6 vs. 90.1 ± 33.6 N; p = 0.34), yield load (43.8 ± 15.2 vs. 39.4 ± 15.5 N; p = 0.53), liner stiffness (12.6 ± 8.4 vs. 11.2 ± 5.5 N/mm; p = 0.45), and elongation at failure (27.1 ± 19.4 vs. 19.9 ± 10.0 mm; p = 0.32). The structural properties of the thickness of the different UHMWPE were comparable in MMPRT repair. Additionally, 1.3 mm PERMATAPE may demonstrate similar repair potential as 2.5 mm PERMATAPE. Level Ⅳ.

Mid-term patient-reported outcomes are inferior in opening-wedge high tibial osteotomy patients with untreated medial meniscus posterior root tear.

The impact of untreated medial meniscus posterior root (MMPR) tear (MMPRT) during opening-wedge high tibial osteotomy (OWHTO) on patient-reported outcomes (PROs) remains poorly understood. This retrospective cohort study aimed to investigate the association between the presence of MMPRT and post-operative PROs in patients who underwent OWHTO. A total of 83 knees that underwent OWHTO that were followed up for 6.6 years were included. Post-operative PROs were assessed using the knee injury and osteoarthritis outcome score (KOOS) subscales. Medial meniscus extrusion (MME) was measured by magnetic resonance imaging (MRI). MMPRT was diagnosed based on preoperative MRI and intraoperative arthroscopy findings. The participants were categorized into the MMPRT and MMPR intact (MMPRI) groups, and their KOOS subscales were compared. Additionally, logistic regression analysis was conducted to explore the correlation between KOOS and MMPRT presence. In total, 29 out of 80 (36.3%) knees were classified into the MMPRT group, while three knees underwent total knee arthroplasty. Preoperative MME was 3.5 ± 1.9 (range 0-8.9) mm, showing correlation with the presence of MMPRT (p = 0.004) by regression analysis. The post-operative KOOS subscales of the MMPRT group were lower than the MMPRI group for pain (p = 0.017), activities of daily living (ADLs) (p = 0.001), sports (p < 0.001) and quality of life (QOL) (p < 0.001). Additionally, regression analysis showed the presence of MMPRT was correlated with lower KOOS subscale scores for pain (p = 0.041), ADLs (p = 0.011), sports (p < 0.001) and QOL (p = 0.002). Preoperative MMPRT correlated with a reduction in mid-term post-operative PROs, as assessed using the KOOS, among patients who underwent OWHTO. Surgeons should consider addressing an MMPRT at the time of OWHTO. Level IV.

Arthroscopic Repair of the Medial Meniscal Root Tear: A Simple Surgical Technique

Medial meniscal root tears pose significant challenges in orthopaedic practice, disrupting knee biomechanics and predisposing to degenerative changes. This article introduces an arthroscopic repair technique tailored for posterior root tears of the medial meniscus. The procedure involves meticulous preoperative evaluation, arthroscopic identification, and suture anchor fixation to restore normal knee mechanics. Inclusion and exclusion criteria ensure suitability, whereas postoperative care emphasizes early rehabilitation. By elucidating the surgical technique and outlining clinical implications, this article aims to equip surgeons with effective strategies for managing this challenging orthopaedic condition.

Nerve injury augments Cacna2d1 transcription via CK2-mediated phosphorylation of the histone deacetylase HDAC2 in dorsal root ganglia

Development of chronic neuropathic pain involves complex synaptic and epigenetic mechanisms. Nerve injury causes sustained upregulation of α2δ-1 (encoded by the Cacna2d1 gene) in the dorsal root ganglion (DRG), contributing to pain hypersensitivity by directly interacting with and augmenting presynaptic NMDA receptor activity in the spinal dorsal horn. Under normal conditions, histone deacetylase 2 (HDAC2) is highly enriched at the Cacna2d1 gene promoter in the DRG, which constitutively suppresses Cacna2d1 transcription. However, nerve injury leads to HDAC2 dissociation from the Cacna2d1 promoter, promoting the enrichment of active histone marks and Cacna2d1 transcription in primary sensory neurons. In this study, we determined the mechanism by which nerve injury diminishes HDAC2 occupancy at the Cacna2d1 promoter in the DRG. Spinal nerve injury in rats increased serine-394 phosphorylation of HDAC2 in the DRG. Coimmunoprecipitation showed that nerve injury enhanced the physical interaction between HDAC2 and casein kinase II (CK2) in the DRG. Furthermore, repeated intrathecal treatment with CX-4945, a potent and specific CK2 inhibitor, markedly reversed nerve injury–induced pain hypersensitivity, HDAC2 phosphorylation, and α2δ-1 expression levels in the DRG. In addition, treatment with CX-4945 largely restored HDAC2 enrichment at the Cacna2d1 promoter and reduced the elevated levels of acetylated H3 and H4 histones, particularly H3K9ac and H4K5ac, at the Cacna2d1 promoter in the injured DRG. These findings suggest that nerve injury increases CK2 activity and CK2-HDAC2 interactions, which enhance HDAC2 phosphorylation in the DRG. This, in turn, diminishes HDAC2 enrichment at the Cacna2d1 promoter, thereby promoting Cacna2d1 transcription.

The Nociceptor Primary Cilium Contributes to Mechanical Nociceptive Threshold and Inflammatory and Neuropathic Pain.

The primary cilium, a single microtubule-based organelle protruding from the cell surface and critical for neural development, also functions in adult neurons. While some dorsal root ganglion neurons elaborate a primary cilium, whether it is expressed by and functional in nociceptors is unknown. Recent studies have shown a role of Hedgehog, whose canonical signaling is primary cilium dependent, in nociceptor sensitization. We establish the presence of primary cilia in soma of rat nociceptors, where they contribute to mechanical threshold, prostaglandin E2 (PGE2)-induced hyperalgesia, and chemotherapy-induced neuropathic pain (CIPN). Intrathecal administration of siRNA targeting Ift88, a primary cilium-specific intra-flagellar transport (IFT) protein required for ciliary integrity, resulted in attenuation of Ift88 mRNA and nociceptor primary cilia. Attenuation of primary cilia was associated with an increase in mechanical nociceptive threshold in vivo, and decrease in nociceptor excitability in vitro, abrogation of hyperalgesia, and nociceptor sensitization induced by both a prototypical pronociceptive inflammatory mediator PGE2 and paclitaxel CIPN, in a sex-specific fashion. siRNA targeting Ift52, another IFT protein, and knockdown of NompB, the Drosophila Ift88 ortholog, also abrogated CIPN and reduced baseline mechanosensitivity, respectively, providing independent confirmation for primary cilia control of nociceptor function. Hedgehog-induced hyperalgesia is attenuated by Ift88 siRNA, supporting a role for primary cilia in Hedgehog-induced hyperalgesia. Attenuation of CIPN by cyclopamine (intradermal and intra-ganglion), which inhibits Hedgehog signaling, supports a role of Hedgehog in CIPN. Our findings support a role of the nociceptor primary cilium in control of mechanical nociceptive threshold and inflammatory and neuropathic pain, the latter Hedgehog-dependent.Significance statement Many neurons have a tiny antenna-like structure, the primary cilium, protruding from their cell body, which processes information about the extracellular environment as well as regulates intracellular signaling. We report experiments aimed at understanding the role of the primary cilium in pain sensory neurons (nociceptors), including in the setting of inflammatory and neuropathic pain. We establish that nociceptors bear a primary cilium and show that this organelle regulates detection of noxious stimuli and contributes to nociceptor sensitization, using both the rat and the fruit fly as model organisms to manipulate primary cilia in pain states. We also identify primary cilium dependence of the contribution of Hedgehog to pain states.

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.

Co-culturing of a Dorsal Root Ganglion Explant with Schwann Cells for Neuron Myelination

Co-culturing of a Dorsal Root Ganglion Explant with Schwann Cells for Neuron Myelination

Establishing a Primary Dorsal Root Ganglia Cell Culture from a Rat Spinal Column

Establishing a Primary Dorsal Root Ganglia Cell Culture from a Rat Spinal Column

Electroacupuncture inhibits TLR4/NF-κB signaling in the dorsal root ganglion of rats with spared nerve injury.

Neuropathic pain can be provoked by high mobility group box 1 (HMGB1) activation of toll-like receptor (TLR)4/nuclear factor (NF)-κB signaling in the dorsal root ganglion (DRG). Electroacupuncture (EA) has been reported to effectively alleviate neuropathic pain with few side effects, but its precise mechanism of action remains unknown. The aim of this study was to explore whether 2 Hz EA stimulation suppresses TLR4/NF-κB signaling in the DRG following spared nerve injury (SNI) in a rat model. In this experiment, SNI rats were given 2 Hz EA once every other day for a total of 21 days. Paw withdrawal threshold (PWT) was measured to assess SNI-induced mechanical hypersensitivity, and western blotting and immunofluorescence staining were used to determine the levels of pain-related signaling molecules and pro-inflammatory mediators in the DRG. SNI up-regulated HMGB1, TLR4, myeloid differentiation factor-88 adaptor protein (MyD88) and NF-κB p65 protein expression in the DRG. In addition, immunofluorescence staining demonstrated that SNI induced higher levels of TLR4 and MyD88 in the DRG. We also demonstrated co-localization of TLR4 and MyD88 with both calcitonin gene-related peptide (CGRP) and isolectin GS-IB4 in the DRG of SNI rats, respectively. Meanwhile, 2 Hz EA stimulation effectively reversed the elevations of HMGB1, TLR4, MyD88 and NF-κB p65 induced by SNI in the DRG, which was coupled with amelioration of SNI-induced mechanical hypersensitivity. The results of this study suggested that inhibition of the TLR4/NF-κB signaling pathway in the DRG by 2 Hz EA might be exploited as a therapeutic option for neuropathic pain.

A Technique for Harvesting and Dissociating Dorsal Root Ganglia for Neuronal Cultures

A Technique for Harvesting and Dissociating Dorsal Root Ganglia for Neuronal Cultures

Nageotte nodules in human DRG reveal neurodegeneration in painful diabetic neuropathy.

Diabetic neuropathy is frequently accompanied by pain and loss of sensation attributed to axonal dieback. We recovered dorsal root ganglia (DRGs) from 90 organ donors, 19 of whom had medical indices for diabetic painful neuropathy (DPN). Nageotte nodules, dead sensory neurons engulfed by non-neuronal cells, were abundant in DPN DRGs and accounted for 25% of all neurons. Peripherin-and Nav1.7-positive dystrophic axons invaded Nageotte nodules, forming small neuroma-like structures. Using histology and spatial sequencing, we demonstrate that Nageotte nodules are mainly composed of satellite glia and non-myelinating Schwann cells that express SPP1 and are intertwined with sprouting sensory axons originating from neighboring neurons. Our findings solve a 100-year mystery of the nature of Nageotte nodules linking these pathological structures to pain and sensory loss in DPN.

Neuronal Enrichment of Dorsal Root Ganglia by Immunopanning

Neuronal Enrichment of Dorsal Root Ganglia by Immunopanning

Neurocardiology: translational advancements and potential.

In our original white paper published in the The Journal of Physiology in 2016, we set out our knowledge of the structural and functional organization of cardiac autonomic control, how it remodels during disease, and approaches to exploit such knowledge for autonomic regulation therapy. The aim of this update is to build on this original blueprint, highlighting the significant progress which has been made in the field since and major challenges and opportunities that exist with regard to translation. Imbalances in autonomic responses, while beneficial in the short term, ultimately contribute to the evolution of cardiac pathology. As our understanding emerges of where and how to target in terms of actuators (including the heart and intracardiac nervous system (ICNS), stellate ganglia, dorsal root ganglia (DRG), vagus nerve, brainstem, and even higher centres), there is also a need to develop sensor technology to respond to appropriate biomarkers (electrophysiological, mechanical, and molecular) such that closed-loop autonomic regulation therapies can evolve. The goal is to work with endogenous control systems, rather than in opposition to them, to improve outcomes.

Co-culturing of a Dorsal Root Ganglion Explant with Schwann Cells for Neuron Myelination

Co-culturing of a Dorsal Root Ganglion Explant with Schwann Cells for Neuron Myelination

Early life stress modulates neonatal somatosensation and the transcriptional profile of immature sensory neurons

Abstract Early life stress (ELS) is associated with an increased risk of experiencing chronic pain during adulthood, but surprisingly little is known about the short-term influence of ELS on nociceptive processing in the immature nervous system and the concomitant effects on somatosensation in the neonate. Here, we investigate how ELS modulates pain in neonatal mice and the transcriptional and electrophysiological signatures of immature dorsal root ganglia (DRG). Shortly after the administration of a neonatal limiting bedding (NLB) paradigm from postnatal days (P)2 to P9, both male and female pups exhibited robust hypersensitivity in response to tactile, pressure, and noxious cold stimuli compared with a control group housed under standard conditions, with no change in their sensitivity to noxious heat. Bulk RNA-seq analysis of L3-L5 DRGs at P9 revealed significant alterations in the transcription of pain- and itch-related genes following ELS, highlighted by a marked downregulation in Sst, Nppb, Chrna6, Trpa1, and Il31ra. Nonetheless, ex vivo whole-cell patch-clamp recordings from putative A- and C-fiber sensory neurons in the neonatal DRG found no significant changes in their intrinsic membrane excitability following NLB. Overall, these findings suggest that ELS triggers hyperalgesia in neonates across multiple pain modalities that is accompanied by transcriptional plasticity within developing sensory neurons. A better understanding of the mechanisms governing the interactions between chronic stress and pain during the neonatal period could inform the future development of novel interventional strategies to relieve pain in infants and children who have experienced trauma.

Acrylic Acid Modified Poly-ethylene Glycol Microparticles for Affinity-Based release of Insulin-Like Growth Factor-1 in Neural Applications.

Sustained release of bioactive molecules via affinity-based interactions presents a promising approach for controlled delivery of growth factors. Insulin-like growth factor-1 (IGF-1) has gained increased attention due to its ability to promote axonal growth in the central nervous system. In this work, we aimed to evaluate the effect of IGF-1 delivery from polyethylene-glycol diacrylate (PEG-DA) microparticles using affinity-based sustained release on neurons. We developed PEG-DA-based microparticles with varying levels of acrylic acid (AA) as a comonomer to tune their overall charge. The particles were synthesized via precipitation polymerization under UV light, yielding microparticles (MPs) with a relatively low polydispersity index. IGF-1 was incubated with the PEG-DA particles overnight, and formulations with a higher AA content resulted in higher loading efficiency and slower release rates over 4 weeks, suggesting the presence of binding interactions between the positively charged IGF-1 and negatively charged particles containing AA. The released IGF-1 was tested in dorsal root ganglion (DRG) neurite outgrowth assay and found to retain its biological activity for up to two weeks after encapsulation. Furthermore, the trophic effect of IGF-1 was tested with stem cell-derived V2a interneurons and found to have a synergistic effect when combined with neurotrophin-3 (NT3). To assess the potential of a combinatorial approach, IGF-1-releasing MPs were encapsulated within a hyaluronic acid (HA) hydrogel and showed promise as a dual delivery system. Overall, the PEG-DA MPs developed herein deliver bioactive IGF-1 for a period of weeks and hold potential to enable axonal growth of injured neurons via sustained release.

Establishing a Primary Dorsal Root Ganglia Cell Culture from a Rat Spinal Column

Establishing a Primary Dorsal Root Ganglia Cell Culture from a Rat Spinal Column

Molecular Study of Varicella zoster virus in Cerebrospinal Fluid from Stroke Patients of Thi-Qar province.

Varicella zoster virus (VZV) is a type of alpha-herpesvirus that specifically targets the nervous system. The initial infection, typically occurring during childhood, results in varicella (commonly known as chickenpox), after which the virus enters a dormant state in cranial nerve ganglia, dorsal root ganglia, and autonomic ganglia throughout the entire neuroaxis. Molecular and genetic studies of viruses are an important tool for virus development and identifying viral treatments to combat the diseases. The aim of the study was to determine the whole ORF4 sequence of the local VZV strains for phylogenetic analysis to determine the variability in the viral sequence. Ten samples of VZV DNA were subjected to the sequencing of the whole ORF4 region following identification using the PCR method. Sequences from five samples have been successfully analyzed. All clinical strains were discovered to possess a genome with a length of 124,884 base pairs. The sequences exhibited the occurrence of two distinct mutations, one being a transversion and the other a transition, with the latter resulting in an alteration of the amino acid. A phylogenetic tree was constructed using the maximum likelihood method based on the sequences of five nucleotide sequences from clinical samples and nine reference VZV strains. The tree displayed the evolutionary distances between these sequences. The analysis of the phylogenetic tree revealed the presence of five primary clades, with four of them originating from India (isolates S1, S2, S4, S5), while S3 exhibited similarity to a strain from the United Kingdom.

B cells drive neuropathic pain-related behaviors in mice through IgG-Fc gamma receptor signaling.

Neuroimmune interactions are essential for the development of neuropathic pain, yet the contributions of distinct immune cell populations have not been fully unraveled. Here, we demonstrate the critical role of B cells in promoting mechanical hypersensitivity (allodynia) after peripheral nerve injury in male and female mice. Depletion of B cells with a single injection of anti-CD20 monoclonal antibody at the time of injury prevented the development of allodynia. B cell-deficient (muMT) mice were similarly spared from allodynia. Nerve injury was associated with increased immunoglobulin G (IgG) accumulation in ipsilateral lumbar dorsal root ganglia (DRGs) and dorsal spinal cords. IgG was colocalized with sensory neurons and macrophages in DRGs and microglia in spinal cords. IgG also accumulated in DRG samples from human donors with chronic pain, colocalizing with a marker for macrophages and satellite glia. RNA sequencing revealed a B cell population in naive mouse and human DRGs. A B cell transcriptional signature was enriched in DRGs from human donors with neuropathic pain. Passive transfer of IgG from injured mice induced allodynia in injured muMT recipient mice. The pronociceptive effects of IgG are likely mediated through immune complexes interacting with Fc gamma receptors (FcγRs) expressed by sensory neurons, microglia, and macrophages, given that both mechanical allodynia and hyperexcitability of dissociated DRG neurons were abolished in nerve-injured FcγR-deficient mice. Consistently, the pronociceptive effects of IgG passive transfer were lost in FcγR-deficient mice. These data reveal that a B cell-IgG-FcγR axis is required for the development of neuropathic pain in mice.

Inhibition of KIF5b-mediated Nav1.8 transport by ropivacaine contributes to axonal regeneration following sciatic nerve injury in rats

Peripheral nerve injury (PNI), typically caused by traumatic accidents or medical events, is currently one of the most common diseases that leads to limb disability. After PNI, tetrodotoxin-resistant voltage-gated sodium channel Nav1.8 is upregulated at the lesion site. Our earlier study suggested that ropivacaine promotes axon regrowth by regulating Nav1.8-mediated macrophage signaling. Nevertheless, the mechanism of ropivacaine in regulation of Nav1.8 expression remains incompletely understood. Kinesin family 5b (KIF5b) was reported to mediate the Nav1.8 axonal transport from dorsal root ganglia (DRGs) to lesion site. Herein, we investigated whether ropivacaine promotes axon regeneration through inhibition of KIF5b-mediated Nav1.8 transport. Reduced levels of KIF5b and Nav1.8 in DRGs coincide with their increase at the lesion site. Nav1.8 mRNA was significantly increased at the lesion site but not in DRGs. Surprisingly, ropivacaine reversed the alterations of Nav1.8 and KIF5b protein expression without affecting Nav1.8 mRNA level. Due to KIF5b overexpression in DRGs, Nav1.8 protein level was significantly decreased in DRGs and increased at the lesion site. We also found KIF5b overexpression significantly impaired behavioral functions, reduced the recovery index of compound muscle action potential (CMAP) amplitude, inhibited axonal regrowth, slowed M1 macrophage infiltration and shift to M2 phenotype, and delayed myelin debris clearance. Notably, all aforementioned results caused by KIF5b overexpression were alleviated by ropivacaine. Furthermore, we demonstrated that inhibition of Nav1.8 transport by A-803467 produced mitigating effects on the impairment of regenerative capacity induced by KIF5b overexpression similar to ropivacaine. These results suggest that ropivacaine promotes axonal regeneration at least partially by inhibiting KIF5b-mediated Nav1.8 forward transport.