Dorsal Ganglion Research Articles

Tumor necrosis factor α receptor 1A transduces the inhibitory effect on axon regeneration triggered by IgG anti-ganglioside GD1a antibodies

Anti-ganglioside antibodies (anti-Gg Abs) have been linked to delayed/poor clinical recovery in both axonal and demyelinating forms of Guillain-Barrè Syndrome (GBS). In many instances, the incomplete recovery is attributed to the peripheral nervous system's failure to regenerate. The cross-linking of cell surface gangliosides by anti-Gg Abs triggers inhibition of nerve repair in both in vitro and in vivo axon regeneration paradigms. This mechanism involves the activation of the small GTPase RhoA, which negatively modulates the growth cone cytoskeleton. At present, the identity/es of the receptor/s responsible for transducing the signal that ultimately leads to RhoA activation remains poorly understood. The aim of this work was to identify the transducer molecule responsible for the inhibitory effect of anti-Gg Abs on nerve repair. Putative candidate molecules were identified through proteomic mass spectrometry of ganglioside affinity-captured proteins from rat cerebellar granule neurons (Prendergast et al., 2014). These candidates were evaluated using an in vitro model of neurite outgrowth with primary cultured dorsal root ganglion neurons (DRGn) and an in vivo model of axon regeneration. Using an shRNA-strategy to silence putative candidates on DRGn, we identified tumor necrosis factor receptor 1A protein (TNFR1A) as a transducer molecule for the inhibitory effect on neurite outgrowth from rat/mouse DRGn cultures of a well characterized mAb targeting the related gangliosides GD1a and GT1b. Interestingly, lack of TNFr1A expression on DRGn abolished the inhibitory effect on neurite outgrowth caused by anti-GD1a but not anti-GT1b specific mAbs, suggesting specificity of GD1a/transducer signaling. Similar results were obtained using primary DRGn cultures from TNFR1a-null mice, which did not activate RhoA after exposure to anti-GD1a mAbs. Generation of single point mutants at the stalk region of TNFR1A identified a critical amino acid for transducing GD1a signaling, suggesting a direct interaction. Finally, passive immunization with an anti-GD1a/GT1b mAb in an in vivo model of axon regeneration exhibited reduced inhibitory activity in TNFR1a-null mice compared to wild type mice. In conclusion, these findings identify TNFR1A as a novel transducer receptor for the inhibitory effect exerted by anti-GD1a Abs on nerve repair, representing a significant step forward toward understanding the factors contributing to poor clinical recovery in GBS associated with anti-Gg Abs.

Purpurin ameliorated neuropathic allodynia and hyperalgesia by modulating neuronal mitochondrial bioenergetics and redox status in type 1 diabetic mice

A substantial proportion of diabetic patients suffer a debilitating and persistent pain state, known as peripheral painful neuropathy that necessitates improved therapy or antidote. Purpurin, a natural anthraquinone compound from Rubia tinctorum L., has been reported to possess antidepressant activity in preclinical studies. As antidepressants have been typically used as standard agents against persistent neuropathic pain, this study aimed to probe the effect of purpurin on neuropathic pain associated with streptozotocin-induced type 1 diabetes in male C57BL6J mice. The Hargreaves test and the von Frey test were used to assess the pain-like behaviors, shown as heat hyperalgesia and mechanical allodynia respectively. Chronic treatment of diabetic mice with purpurin not only ameliorated the established symptoms of heat hyperalgesia and mechanical allodynia, but also arrested the development of these pain states given preemptively at low doses. Although purpurin treatment hardly impacted on metabolic disturbance in diabetic mice, it ameliorated exacerbated oxidative stress in pain-associated tissues, improved mitochondrial bioenergetics in dorsal root ganglion neurons and restored nerve conduction velocity in sciatic nerves. Notably, the analgesic actions of purpurin were modified by pharmacologically manipulating redox status and mitochondrial bioenergetics. These findings unveil the analgesic activity of purpurin, an effect that is causally associated with its bioenergetics-enhancing and antioxidant effects, in mice with type 1 diabetes.

PEDOT-Integrated Fish Swim Bladders as Conductive Nerve Conduits.

Advanced artificial nerve conduits offer a promising alternative for nerve injury repair. Current research focuses on improving the therapeutic effectiveness of nerve conduits by optimizing scaffold materials and functional components. In this study, a novel poly(3,4-ethylenedioxythiophene) (PEDOT)-integrated fish swim bladder (FSB) is presented as a conductive nerve conduit with ordered topology and electrical stimulation to promote nerve regeneration. PEDOT nanomaterials and adhesive peptides (IKVAV) are successfully incorporated onto the decellularized FSB substrate through pre-coating with polydopamine. The obtained PEDOT/IKVAV-integrated FSB substrate exhibits outstanding mechanical properties, high electrical conductivity, stability, as well as excellent biocompatibility and bioadhesive properties. In vitro studies confirm that the PEDOT/IKVAV-integrated FSB can effectively facilitate the growth and directional extension of pheochromocytoma 12 cells and dorsal root ganglion neurites. In addition, in vivo experiments demonstrate that the proposed PEDOT/IKVAV-integrated FSB conduit can accelerate defective nerve repair and functional restoration. The findings indicate that the FSB-derived conductive nerve conduits with multiple regenerative inducing signals integration provide a conducive milieu for nerve regeneration, exhibiting great potential for repairing long-segment neural defects.

Baricitinib ameliorates inflammatory and neuropathic pain in collagen antibody-induced arthritis mice by modulating the IL-6/JAK/STAT3 pathway and CSF-1 expression in dorsal root ganglion neurons

BackgroundJanus kinase (JAK) inhibitors, such as baricitinib, are widely used to treat rheumatoid arthritis (RA). Clinical studies show that baricitinib is more effective at reducing pain than other similar drugs. Here, we aimed to elucidate the molecular mechanisms underlying the pain relief conferred by baricitinib, using a mouse model of arthritis.MethodsWe treated collagen antibody-induced arthritis (CAIA) model mice with baricitinib, celecoxib, or vehicle, and evaluated the severity of arthritis, histological findings of the spinal cord, and pain-related behaviours. We also conducted RNA sequencing (RNA-seq) to identify alterations in gene expression in the dorsal root ganglion (DRG) following baricitinib treatment. Finally, we conducted in vitro experiments to investigate the direct effects of baricitinib on neuronal cells.ResultsBoth baricitinib and celecoxib significantly decreased CAIA and improved arthritis-dependent grip-strength deficit, while only baricitinib notably suppressed residual tactile allodynia as determined by the von Frey test. CAIA induction of inflammatory cytokines in ankle synovium, including interleukin (IL)-1β and IL-6, was suppressed by treatment with either baricitinib or celecoxib. In contrast, RNA-seq analysis of the DRG revealed that baricitinib, but not celecoxib, restored gene expression alterations induced by CAIA to the control condition. Among many pathways changed by CAIA and baricitinib treatment, the interferon-alpha/gamma, JAK-signal transducer and activator of transcription 3 (STAT3), and nuclear factor kappa B (NF-κB) pathways were considerably decreased in the baricitinib group compared with the celecoxib group. Notably, only baricitinib decreased the expression of colony-stimulating factor 1 (CSF-1), a potent cytokine that causes neuropathic pain through activation of the microglia–astrocyte axis in the spinal cord. Accordingly, baricitinib prevented increases in microglia and astrocytes caused by CAIA. Baricitinib also suppressed JAK/STAT3 pathway activity and Csf1 expression in cultured neuronal cells.ConclusionsOur findings demonstrate the effects baricitinib has on the DRG in relation to ameliorating both inflammatory and neuropathic pain.

Role of Spinal Cholecystokinin Octapeptide, Nociceptin/Orphanin FQ, and Hemokinin-1 in Diabetic Allodynia.

A complication of diabetes is neuropathic pain, which is difficult to control with medication. We have confirmed that neuropathic pain due to mechanical allodynia in diabetic mice is mediated by a characteristic neuropeptide in the spinal cord. We evaluated the strength of mechanical allodynia in mice using von Frey filaments. When mice were intravenously injected with streptozotocin, mechanical allodynia appeared 3 days later. Antibodies of representative neuropeptides were intrathecally (i.t.) administered to allodynia-induced mice 7 days after the intravenous administration of streptozotocin, and allodynia was reduced by anti-cholecystokinin octapeptide antibodies, anti-nociceptin/orphanin FQ antibodies, and anti-hemokinin-1 antibodies. In contrast, i.t.-administered anti-substance P antibodies, anti-somatostatin antibodies, and anti-angiotensin II antibodies did not affect streptozotocin-induced diabetic allodynia mice. Mechanical allodynia was attenuated by the i.t. administration of CCK-B receptor antagonists and ORL-1 receptor antagonists. The mRNA level of CCK-B receptors in streptozotocin-induced diabetic allodynia mice increased in the spinal cord, but not in the dorsal root ganglion. These results indicate that diabetic allodynia is caused by cholecystokinin octapeptide, nociceptin/orphanin FQ, and hemokinin-1 released from primary afferent neurons in the spinal cord that transmit pain to the brain via the spinal dorsal horn.

Effect of repeated sciatic nerve crush on the conditioning lesion response: Generating an experimental animal model to prolong the denervation period while maintaining peripheral nerve continuity

Peripheral nerves exhibit long-term residual motor dysfunction following injury. The length of the denervation period before nerve and muscle reconnection is an important factor in motor function recovery. We aimed to investigate whether repeated nerve crush injuries to the same site every 7 days would preserve the conditioning lesion (CL) response and to determine the number of nerve crush injuries required to create an experimental animal model that would prolong the denervation period while maintaining peripheral nerve continuity. Rats were grouped according to the number of sciatic nerve crushes. A significant decrease in the soleus muscle fiber cross-sectional area was observed with increased crushes. After a single crush, macrophage accumulation and macrophage chemotaxis factor CCL2 expression in dorsal root ganglia were markedly increased, which aligned with the gene expression of Ccl2 and its receptor Ccr2. Macrophage numbers, histological CCL2 expression, and Ccl2 and Ccr2 gene expression levels decreased, depending on the number of repeated crushes. Histological analysis and gene expression analysis in the group with four repeated crushes did not differ significantly when compared with uninjured animals. Our findings indicated that repeated nerve crushes at the same site every 7 days sustained innervation loss and caused a loss of the CL response. The experimental model did not require nerve stump suturing and is useful for exploring factors causing prolonged denervation-induced motor dysfunction. Significance StatementThis study elucidates the effects of repeated nerve crush injury to the same site on innervation and conditioning lesion responses and demonstrates the utility of an experimental animal model that recapitulates the persistent residual motor deficits owing to prolonged denervation without requiring nerve transection and transection suturing.

126-OR: Differences of Three-Dimensional Pathology of Dorsal Root Ganglia in Neuropathy of Type 1 and Type 2 Diabetes Mellitus

126-OR: Differences of Three-Dimensional Pathology of Dorsal Root Ganglia in Neuropathy of Type 1 and Type 2 Diabetes Mellitus

Computed Tomography-Guided Dorsal Root Ganglion Ozone Injection Combined With Pulsed Radiofrequency for Acute Herpes Zoster Neuralgia Treatment of Middle-aged and Elderly People: A Randomized, Double-blinded, Controlled Trial.

To investigate the efficacy and safety of pulsed radiofrequency of the dorsal root ganglion combined with ozone injection for treating acute herpes zoster (HZ) neuralgia in middle-aged and elderly adults. A total of 164 middle-aged and elderly patients with acute HZ were randomly assigned to 2 groups: the pulsed radiofrequency combined with ozone injection group (group A) and the pulsed radiofrequency group (group B). The therapeutic effects were evaluated using Numeric Rating Scale (NRS) scores and the average doses of gabapentin (mg/d) preoperatively and 1 day, 2 weeks, 4 weeks, 12 weeks, and 24 weeks postoperatively. The incidence of clinically significant postherpetic neuralgia (PHN) and complications in the 2 groups were recorded. The data showed that the NRS scores and the doses of gabapentin after treatment were significantly lower when compared with the baseline values in both groups. Compared with group B, the NRS scores and the doses of postoperative gabapentin were significantly lower in group A. The incidence of PHN was significantly lower at weeks 4, 12, and 24 in group A than in group B. No adverse reactions occurred in either of the 2 groups post-treatment. The results indicated that ozone injection in the dorsal root ganglion combined with pulsed radiofrequency therapy was more effective in treating acute HZ neuralgia in middle-aged and elderly adults. It provides patients with longer-lasting pain relief, decreased incidence of PHN and the doses of medication, and improved quality of life than with Pulsed Radiofrequency treatment.

The potential neuroprotective effects of cannabinoids against paclitaxel-induced peripheral neuropathy: in vitro study on neurite outgrowth.

Introduction: Chemotherapy-induced peripheral neuropathy (CIPN) is a shared burden for 68.1% of oncological patients undergoing chemotherapy with Paclitaxel (PTX). The symptoms are intense and troublesome, patients reporting paresthesia, loss of sensation, and dysesthetic pain. While current medications focus on decreasing the symptom intensity, often ineffective, no medication is yet recommended by the guidelines for the prevention of CIPN. Cannabinoids are an attractive option, as their neuroprotective features have already been demonstrated in neuropathies with other etiologies, by offering the peripheral neurons protection against toxic effects, which promotes analgesia. Methods: We aim to screen several new cannabinoids for their potential use as neuroprotective agents for CIPN by investigating the cellular toxicity profile and by assessing the potential neuroprotective features against PTX using a primary dorsal root ganglion neuronal culture. Results: Our study showed that synthetic cannabinoids JWH-007, AM-694 and MAB-CHMINACA and phytocannabinoids Cannabixir® Medium dried flowers (NC1) and Cannabixir® THC full extract (NC2) preserve the viability of fibroblasts and primary cultured neurons, in most of the tested dosages and time-points. The combination between the cannabinoids and PTX conducted to a cell viability of 70%-89% compared to 40% when PTX was administered alone for 48h. When assessing the efficacy for neuroprotection, the combination between cannabinoids and PTX led to better preservation of neurite length at all tested time-points compared to controls, highly drug and exposure-time dependent. By comparison, the combination of the cannabinoids and PTX administered for 24h conducted to axonal shortening between 23% and 44%, as opposed to PTX only, which shortened the axons by 63% compared to their baseline values. Discussion and Conclusion: Cannabinoids could be potential new candidates for the treatment of paclitaxel-induced peripheral neuropathy; however, our findings need to be followed by additional tests to understand the exact mechanism of action, which would support the translation of the cannabinoids in the oncological clinical practice.

Opposite effects of acute and chronic IGF1 on rat dorsal root ganglion neuron excitability.

Insulin-like growth factor-1 (IGF-1) is a polypeptide hormone with a ubiquitous distribution in numerous tissues and with various functions in both neuronal and non-neuronal cells. IGF-1 provides trophic support for many neurons of both the central and peripheral nervous systems. In the central nervous system (CNS), IGF-1R signaling regulates brain development, increases neuronal firing and modulates synaptic transmission. IGF-1 and IGF-IR are not only expressed in CNS neurons but also in sensory dorsal root ganglion (DRG) nociceptive neurons that convey pain signals. DRG nociceptive neurons express a variety of receptors and ion channels that are essential players of neuronal excitability, notably the ligand-gated cation channel TRPV1 and the voltage-gated M-type K+ channel, which, respectively, triggers and dampens sensory neuron excitability. Although many lines of evidence suggest that IGF-IR signaling contributes to pain sensitivity, its possible modulation of TRPV1 and M-type K+ channel remains largely unexplored. In this study, we examined the impact of IGF-1R signaling on DRG neuron excitability and its modulation of TRPV1 and M-type K+ channel activities in cultured rat DRG neurons. Acute application of IGF-1 to DRG neurons triggered hyper-excitability by inducing spontaneous firing or by increasing the frequency of spikes evoked by depolarizing current injection. These effects were prevented by the IGF-1R antagonist NVP-AEW541 and by the PI3Kinase blocker wortmannin. Surprisingly, acute exposure to IGF-1 profoundly inhibited both the TRPV1 current and the spike burst evoked by capsaicin. The Src kinase inhibitor PP2 potently depressed the capsaicin-evoked spike burst but did not alter the IGF-1 inhibition of the hyperexcitability triggered by capsaicin. Chronic IGF-1 treatment (24 h) reduced the spike firing evoked by depolarizing current injection and upregulated the M-current density. In contrast, chronic IGF-1 markedly increased the spike burst evoked by capsaicin. In all, our data suggest that IGF-1 exerts complex effects on DRG neuron excitability as revealed by its dual and opposite actions upon acute and chronic exposures.

Varicella-zoster virus-related neurological complications: From infection to immunomodulatory therapies.

The Varicella-zoster virus (VZV), classified as a neurotropic member of the Herpesviridae family, exhibits a characteristic pathogenicity, predominantly inducing varicella, commonly known as chickenpox, during the initial infectious phase, and triggering the reactivation of herpes zoster, more commonly recognized as shingles, following its emergence from a latent state. The pathogenesis of VZV-associated neuroinflammation involves a complex interplay between viral replication within sensory ganglia and immune-mediated responses that contribute to tissue damage and dysfunction. Upon primary infection, VZV gains access to sensory ganglia, establishing latent infection within neurons. During reactivation, the virus can spread along sensory nerves, triggering a cascade of inflammatory mediators, chemokines, and immune cell infiltration in the affected neural tissues. The role of both adaptive and innate immune reactions, including the contributions of T and B cells, macrophages, and dendritic cells, in orchestrating the immune-mediated damage in the central nervous system is elucidated. Furthermore, the aberrant activation of the natural defence mechanism, characterised by the dysregulated production of immunomodulatory proteins and chemokines, has been implicated in the pathogenesis of VZV-induced neurological disorders, such as encephalitis, myelitis, and vasculopathy. The intricate balance between protective and detrimental immune responses in the context of VZV infection emphasises the necessity for an exhaustive comprehension of the immunopathogenic mechanisms propelling neuroinflammatory processes. Despite the availability of vaccines and antiviral therapies, VZV-related neurological complications remain a significant concern, particularly in immunocompromised individuals and the elderly. Elucidating these mechanisms might facilitate the emergence of innovative immunomodulatory strategies and targeted therapies aimed at mitigating VZV-induced neuroinflammatory damage and improving clinical outcomes. This comprehensive understanding enhances our grasp of viral pathogenesis and holds promise for pioneering therapeutic strategies designed to mitigate the neurological ramifications of VZV infections.

Dorsal wrist ganglion: clinical and imaging correlation in symptomatic population based on high-field MRI.

To determine prevalence in the symptomatic population of dorsal mucoid cysts centered on dorsal capsuloscapholunate septum (DCSS) using high-field magnetic resonance imaging (MRI) for anatomoclinical and epidemiological correlations. This single-center retrospective study analyzed all 3-Tesla MRIs consecutively performed for painful wrists in 295 patients. Two blinded readers performed measurements. The protocol included T1 spin echo and 3D proton density sequences with fat saturation. Inter-observer reliability was assessed using kappa and intra-class correlation coefficients for cyst detection and volumetry, respectively. Disagreements concerning cyst detection were resolved by a consensus reading. Cyst size, relationship to extrinsic and scapholunate ligaments (SL), continuity of SL, minimum distance to the posterior interosseous nerve (PIN), cyst communication with joint, and anatomical classifications of cysts were analyzed. Correlation tests were performed to assess associations. Two-hundred ninety-five patients (mean age 39.6 +/- 15.6 (standard deviation), 161 males) were evaluated for detection of dorsal wrist cysts identified in 150/295. In this subgroup, the mean age was 38.7 years (15-75), the sex ratio of 0.6 (59% women), and the median volume cyst of 8.7 mm3 (0.52-2555). Cyst detection, volume, and major axis measurements showed very high agreement between observers, respectively, 0.89, 0.96, and 0.91. 42 patients had dorsal SL pain. A weak negative correlation was found between distance to PIN and dorsal SL pain (r = -0.2415; p < 0.05) and a weak positive correlation between Guérini's classification and dorsal SL pain (r = 0.2466; p < 0.05). High-field MRI is the modality of choice for the detection, anatomical, and volumetric assessment of dorsal cysts. Preoperative assessment will be aided by the proposed revised anatomical classification. High-field MRI is the modality of choice for the anatomical study of dorsal ganglion cysts. It allows the radiologist to accurately describe the anatomical relationships, size, and visibility of the pedicle, essential information for the surgeon's preoperative assessment. Dorsal mucoid wrist ganglion is a condition for which prevalence remains to be determined. High-field MRI is a reproducible imaging modality for the detection and assessment of dorsal wrist cysts. High-field MRI has a key role in the preoperative management of dorsal mucoid cysts.

KCNQ1 is an essential mediator of the sex-dependent perception of moderate cold temperatures

Low temperatures and cooling agents like menthol induce cold sensation by activating the peripheral cold receptors TRPM8 and TRPA1, cation channels belonging to the TRP channel family, while the reduction of potassium currents provides an additional and/or synergistic mechanism of cold sensation. Despite extensive studies over the past decades to identify the molecular receptors that mediate thermosensation, cold sensation is still not fully understood and many cold-sensitive peripheral neurons do not express the well-established cold sensor TRPM8. We found that the voltage-gated potassium channel KCNQ1 (Kv7.1), which is defective in cardiac LQT1 syndrome, is, in addition to its known function in the heart, a highly relevant and sex-specific sensor of moderately cold temperatures. We found that KCNQ1 is expressed in skin and dorsal root ganglion neurons, is sensitive to menthol and cooling agents, and is highly sensitive to moderately cold temperatures, in a temperature range at which TRPM8 is not thermosensitive. C-fiber recordings from KCNQ1-/- mice displayed altered action potential firing properties. Strikingly, only male KCNQ1-/- mice showed substantial deficits in cold avoidance at moderately cold temperatures, with a strength of the phenotype similar to that observed in TRPM8-/- animals. While sex-dependent differences in thermal sensitivity have been well documented in humans and mice, KCNQ1 is the first gene reported to play a role in sex-specific temperature sensation. Moreover, we propose that KCNQ1, together with TRPM8, is a key instrumentalist that orchestrates the range and intensity of cold sensation.

A Narrative Review of the Dorsal Root Ganglia and Spinal Cord Mechanisms of Action of Neuromodulation Therapies in Neuropathic Pain.

Neuropathic pain arises from injuries to the nervous system in diseases such as diabetes, infections, toxicity, and traumas. The underlying mechanism of neuropathic pain involves peripheral and central pathological modifications. Peripheral mechanisms entail nerve damage, leading to neuronal hypersensitivity and ectopic action potentials. Central sensitization involves a neuropathological process with increased responsiveness of the nociceptive neurons in the central nervous system (CNS) to their normal or subthreshold input due to persistent stimuli, leading to sustained electrical discharge, synaptic plasticity, and aberrant processing in the CNS. Current treatments, both pharmacological and non-pharmacological, aim to alleviate symptoms but often face challenges due to the complexity of neuropathic pain. Neuromodulation is emerging as an important therapeutic approach for the treatment of neuropathic pain in patients unresponsive to common therapies, by promoting the normalization of neuronal and/or glial activity and by targeting cerebral cortical regions, spinal cord, dorsal root ganglia, and nerve endings. Having a better understanding of the efficacy, adverse events and applicability of neuromodulation through pre-clinical studies is of great importance. Unveiling the mechanisms and characteristics of neuromodulation to manage neuropathic pain is essential to understand how to use it. In the present article, we review the current understanding supporting dorsal root ganglia and spinal cord neuromodulation as a therapeutic approach for neuropathic pain.

Three-dimensional chromatin mapping of sensory neurons reveals that cohesin-dependent genomic domains are required for axonal regeneration.

The in vivo three-dimensional genomic architecture of adult mature neurons at homeostasis and after medically relevant perturbations such as axonal injury remains elusive. Here we address this knowledge gap by mapping the three-dimensional chromatin architecture and gene expression programme at homeostasis and after sciatic nerve injury in wild-type and cohesin-deficient mouse sensory dorsal root ganglia neurons via combinatorial Hi-C and RNA-seq. We find that cohesin is required for the full induction of the regenerative transcriptional program, by organising 3D genomic domains required for the activation of regenerative genes. Importantly, loss of cohesin results in disruption of chromatin architecture at regenerative genes and severely impaired nerve regeneration. Together, these data provide an original three-dimensional chromatin map of adult sensory neurons in vivo and demonstrate a role for cohesin-dependent chromatin interactions in neuronal regeneration.

Mapping Somatosensory Afferent Circuitry to Bone Identifies Neurotrophic Signals Required for Fracture Healing.

The profound pain accompanying bone fracture is mediated by somatosensory neurons, which also appear to be required to initiate bone regeneration following fracture. Surprisingly, the precise neuroanatomical circuitry mediating skeletal nociception and regeneration remains incompletely understood. Here, we characterized somatosensory dorsal root ganglia (DRG) afferent neurons innervating murine long bones before and after experimental long bone fracture in mice. Retrograde labeling of DRG neurons by an adeno-associated virus with peripheral nerve tropism showed AAV-tdT signal. Single cell transcriptomic profiling of 6,648 DRG neurons showed highest labeling across CGRP+ neuron clusters (6.9-17.2%) belonging to unmyelinated C fibers, thinly myelinated Aδ fibers and Aβ-Field LTMR (9.2%). Gene expression profiles of retrograde labeled DRG neurons over multiple timepoints following experimental stress fracture revealed dynamic changes in gene expression corresponding to the acute inflammatory ( S100a8 , S100a9 ) and mechanical force ( Piezo2 ). Reparative phase after fracture included morphogens such as Tgfb1, Fgf9 and Fgf18 . Two methods to surgically or genetically denervate fractured bones were used in combination with scRNA-seq to implicate defective mesenchymal cell proliferation and osteodifferentiation as underlying the poor bone repair capacity in the presence of attenuated innervation. Finally, multi-tissue scRNA-seq and interactome analyses implicated neuron-derived FGF9 as a potent regulator of fracture repair, a finding compatible with in vitro assessments of neuron-to-skeletal mesenchyme interactions.

Low-frequency dorsal root stimulation is effective for various pain etiologies and pain locations.

Dorsal root ganglion stimulation (DRG-S) has emerged as a novel therapeutic approach for managing chronic neuropathic pain. This study aims to compare the effectiveness of 4-20 Hz DRG-S through a retrospective analysis of a cohort of 28 patients with various neuropathic pain etiologies and pain locations. Patient responses to both stimulation frequencies were examined using the Numeric Rating Scale (NRS) and Patient Global Impression of Change (PGIC) assessments. Factors such as patient preference and satisfaction were also evaluated. The results indicate that 4 Hz DRG-S is not only as effective as 20 Hz stimulation but may also surpass it. Among the 28 patients, 26 assessed 4 Hz stimulation to be at least as effective as 20 Hz, with the majority (22 out of 26) considering 4 Hz stimulation superior. After trying 4 Hz stimulation, 24 out of 28 patients chose it over 20 Hz, while two patients opted for a combination of both settings. Only two patients reverted to their original 20 Hz stimulation program. A statistically significant pain reduction of 24% was observed when comparing the effects of 4 Hz versus 20 Hz. The study highlights the broader applicability of low-frequency DRG-S, extending its benefits beyond the realm of low back pain. Patients with diverse pain etiologies and locations experienced comparable positive outcomes, suggesting that the advantages of low-frequency stimulation are not confined to specific pain types or locations. This study emphasizes the potential of 4 Hz DRG-S as a valuable alternative to the standard 20 Hz stimulation. Although the exact mechanisms require further investigation, the observed clinical benefits and patient preferences for low-frequency stimulation suggest its viability across diverse pain indications and locations. Additional research is necessary to substantiate these findings and assess the durability and economic implications of low-frequency DRG-S.

Injury distance limits the transcriptional response to spinal injury.

The ability of neurons to sense and respond to damage is fundamental to homeostasis and nervous system repair. For some cell types, notably dorsal root ganglia (DRG) and retinal ganglion cells (RGCs), extensive profiling has revealed a large transcriptional response to axon injury that determines survival and regenerative outcomes. In contrast, the injury response of most supraspinal cell types, whose limited regeneration constrains recovery from spinal injury, is mostly unknown. Here we employed single-nuclei sequencing in mice to profile the transcriptional responses of diverse supraspinal cell types to spinal injury. Surprisingly, thoracic spinal injury triggered only modest changes in gene expression across all populations, including corticospinal tract (CST) neurons. Moreover, CST neurons also responded minimally to cervical injury but much more strongly to intracortical axotomy, including upregulation of numerous regeneration and apoptosis-related transcripts shared with injured DRG and RGC neurons. Thus, the muted response of CST neuron to spinal injury is linked to the injury's distal location, rather than intrinsic cellular characteristics. More broadly, these findings indicate that a central challenge for enhancing regeneration after a spinal injury is the limited sensing of distant injuries and the subsequent modest baseline neuronal response.

Intrathecal gastrodin alleviates allodynia in a rat spinal nerve ligation model through NLRP3 inflammasome inhibition

BackgroundGastrodin (GAS), a main bioactive component of the herbal plant, Gastrodia elata Blume, has shown to have beneficial effects on neuroinflammatory diseases such as Alzheimer’s disease in animal studies and migraine in clinical studies. Inflammasome is a multimeric protein complex having a core of pattern recognition receptor and has been implicated in the development of neuroinflammatory diseases. Gastrodin has shown to modulate the activation of nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome. This study investigated the effects of GAS on the intensity of mechanical allodynia and associated changes in NLRP3 inflammasome expression at the spinal level using L5/6 spinal nerve ligation model (SNL) in rats.MethodsIntrathecal (IT) catheter implantation and SNL were used for drug administration and pain model in male Sprague-Dawley rats. The effect of gastrodin or MCC950 (NLRP3 inflammasome inhibitor) on mechanical allodynia was measured by von Frey test. Changes in NLRP3 inflammasome components and interleukin-1β (IL-1β) and cellular expression were examined in the spinal cord and dorsal root ganglion.ResultsThe expression of NLRP3 inflammasome components was found mostly in the neurons in the spinal cord and dorsal root ganglion. The protein and mRNA levels of NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), caspase-1, and IL-1β were upregulated in SNL animals compared to Sham animals. IT administration of GAS significantly attenuated the expression of NLRP3 inflammasome and the intensity of SNL-induced mechanical allodynia. NLRP3 inflammasome inhibitor, MCC950, also attenuated the intensity of allodynia, but the effect is less strong and shorter than that of GAS.ConclusionsExpression of NLRP3 inflammasome and IL-1β is greatly increased and mostly found in the neurons at the spinal level in SNL model, and IT gastrodin exerts a significant anti-allodynic effect in SNL model partly through suppressing the expression of NLRP3 inflammasome.

Effectiveness of two-dose vs. one-dose varicella vaccine in children in Shanghai, China: a prospective cohort study.

Varicella, a highly contagious viral disease caused by the varicella-zoster virus (VZV), affects millions globally, with a higher prevalence among children. After the initial infection, VZV lies dormant in sensory ganglia and has the potential to reactivate much later, causing herpes zoster (HZ). Vaccination is one of the most effective methods to prevent varicella, and the two-dose varicella vaccine (VarV) regimen is widely used around the world. In China, the VarV has been included in the national immunization programme with a recommended single-dose regimen. This study aimed to compare the effectiveness of the two-dose vs. one-dose VarV regimen in children in Shanghai, China. A prospective cohort study was conducted in Shanghai, China, from September 2018 to December 2022. The study enrolled children aged 3-18 years who had received either the one-dose, two-dose, or 0-dose VarV regimen. Vaccination history, varicella infection status, and relevant variables, including demographic information (name, date of birth and sex) and medical history (clinical features of varicella and illness duration) were collected through medical record review and parental interviews. A total of 3,838 children were included in the study, with 407 in the 0-dose regimen group, 2,107 in the one-dose regimen group and 1,324 in the two-dose regimen group. The corresponding incidence density in these groups was 0.13, 0.05 and 0.03 cases per 1,000 person-days, respectively. The adjusted vaccine effectiveness (VE) was 81.7% (95%CI: 59.3-91.8%) for the two-dose regimen and 60.3% (95%CI: 29.3-77.7%) for the one-dose regimen, compared to the 0-dose regimen. The two-dose VarV regimen showed a protective effectiveness of 47.6% (95%CI: 2.5-71.9%) compared to the one-dose VarV regimen. This study provides evidence supporting the greater effectiveness of the two-dose VarV regimen in preventing varicella infection compared to the one-dose regimen.