Investigation of the Neuro-Regenerative Effects of Bioresonance and Magnetotherapy in Sciatic Nerve Damage-Induced Rats / Investigación de los Efectos Neurorregenerativos de Biorresonancia y Magnetoterapia en Ratas Inducidas por Daño del Nervio Ciático

SUMMARY: Peripheral nerve damage is a significant clinical problem that can lead to severe complications in patients. Regarding the regeneration of peripheral nerves, it is crucial to use experimental animals' nerves and use different evaluation methods. Epineural or perineural suturing is the gold standard in treating sciatic nerve injury, but nerve repair is often unsuccessful. This study aimed to investigate the neuroregenerative effects of magnetotherapy and bioresonance in experimental animals with sciatic nerve damage. In this study, 24 female Wistar rats were divided into 7 groups (n=6) as follows: Group 1 (Control), Group 2 (Axonotmesis control), Group 3 (Anastomosis control), Group 4 (Axonotmesis + magnetotherapy), Group 5 (Anastomosis + magnetotherapy), Group 6 (Axonotmesis + bioresonance), Group 7 (Anastomosis + bioresonance). Magnetotherapy and bioresonance treatments were applied for 12 weeks. Behavioural tests and EMG tests were performed at the end of the 12th week. Then the rats were sacrificed, and a histopathological evaluation was made. The statistical significance level was taken as 5 % in the calculations, and the SPSS (IBM SPSS for Windows, ver.21) statistical package program was used for the calculations. Statistically significant results were obtained in animal behaviour tests, EMG, and pathology groups treated with magnetotherapy. There was no statistically significant difference in the groups treated with bioresonance treatment compared to the control groups. Muscle activity and nerve repair occurred in experimental animals with acute peripheral nerve damage due to 12 weeks of magnetotherapy, and further studies should support these results.

El daño a los nervios periféricos es un problema clínico importante que puede conducir a complicaciones graves en los pacientes. En cuanto a la regeneración de los nervios periféricos, es crucial utilizar los nervios de los animales de experimentación y diferentes métodos de evaluación. La sutura epineural o perineural es el gold estándar en el tratamiento de lesiones del nervio ciático, pero la reparación del nervio a menudo no tiene éxito. Este estudio tuvo como objetivo investigar los efectos neuroregenerativos de la magnetoterapia y la biorresonancia en animales de experimentación con daño del nervio ciático. En el estudio, 24 ratas hembras Wistar se dividieron en 7 grupos (n=6) de la siguiente manera: Grupo 1 (Control), Grupo 2 (Control de axonotmesis), Grupo 3 (Control de anastomosis), Grupo 4 (Axonotmesis + magnetoterapia), Grupo 5 (Anastomosis + magnetoterapia), Grupo 6 (Axonotmesis + biorresonancia), Grupo 7 (Anastomosis + biorresonancia). Se aplicaron durante 12 semanas tratamientos de magnetoterapia y biorresonancia. Las pruebas de comportamiento y las pruebas de EMG se realizaron al final de la semana 12. Luego se sacrificaron las ratas y se realizó una evaluación histopatológica. El nivel de significación estadística se tomó como 5 % en los cálculos, y se utilizó el programa de paquete estadístico SPSS (IBM SPSS para Windows, ver.21). Se obtuvieron resultados estadísticamente significativos en pruebas de comportamiento animal, EMG y grupos de patología tratados con magnetoterapia. No hubo diferencia estadísticamente significativa en los grupos con tratamiento de biorresonancia en comparación con los grupos controles. La actividad muscular y la reparación nerviosa, se produjeron en animales de experimentación con daño nervioso periférico agudo, debido a 12 semanas de magnetoterapia.Estudios adicionales deberían respaldar estos resultados.

Retrograde labeling correlates with motor unit number estimation in rapid-stretch nerve injury.

INTRODUCTION/AIMS: Rapid-stretch nerve injuries represent a substantial treatment challenge. No study has examined motor neuron connection after rapid-stretch injury. Our objective in this study was to characterize the electrophysiological properties of graded rapid-stretch nerve injury and assess motor neuron health using retrograde labeling and muscle adenosine triphosphatase (ATPase) histology. METHODS: Male C57BL/6 mice (n = 6 per group) were rapid-stretch injured at four levels of severity: sham injury, stretch within elastic modulus, inelastic deformation, and stretch rupture. Serial compound muscle action potential (CMAP) and motor unit number estimation (MUNE) measurements were made for 48 days, followed by retrograde labeling and muscle ATPase histology. RESULTS: Elastic injuries showed no durable abnormalities. Inelastic injury demonstrated profound initial reduction in CMAP and MUNE (P < .036) on day 2, with partial recovery by day 14 after injury (CMAP: 40% baseline, P = .003; MUNE: 55% baseline, P = .033). However, at the experimental endpoint, CMAP had recovered to baseline with only limited improvement in MUNE. Inelastic injury led to reduced retrograde-labeled neurons and grouped fiber type histology. Rupture injury had severe and nonrecovering electrophysiological impairment, dramatically reducing labeled neurons (P = .005), and atrophic or type 1 muscle fibers. There was an excellent correlation between MUNE and retrograde-labeled tibial motor neurons across injury severities (R2  = 0.96). DISCUSSION: There was no significant electrophysiological derangement in low-severity injuries but there was recoverable conduction block in inelastic injury with slow recovery, potentially due to collateral sprouting. Rupture injuries yielded permanent failure of injured axons to reinnervate. These results provide insight into the pathophysiology of clinical injuries and recovery.

Hydrogen peroxide induced by nerve injury promotes axon regeneration via connective tissue growth factor.

Regeneration of the neuromuscular junction (NMJ) leverages on extensive exchange of factors released from motor axon terminals (MATs), muscle fibers and perisynaptic Schwann cells (PSCs), among which hydrogen peroxide (H2O2) is a major pro-regenerative signal. To identify critical determinants of NMJ remodeling in response to injury, we performed temporal transcriptional profiling of NMJs from 2 month-old mice during MAT degeneration/regeneration, and cross-referenced the differentially expressed genes with those elicited by H2O2 in SCs. We identified an enrichment in extracellular matrix (ECM) transcripts, including Connective Tissue Growth Factor (Ctgf), which is usually expressed during development. We discovered that Ctgf levels are increased in a Yes-associated protein (YAP)-dependent fashion in response to rapid, local H2O2 signaling generated by stressed mitochondria in the injured sciatic nerve, a finding highlighting the importance of signals triggered by mechanical force to motor nerve repair. Through sequestration of Ctgf or inactivation of H2O2, we delayed the recovery of neuromuscular function by impairing SC migration and, in turn, axon-oriented re-growth. These data indicate that H2O2 and its downstream effector Ctgf are pro-regenerative factors that enable axonal growth, and reveal a striking ECM remodeling process during nerve regeneration upon local H2O2 signaling. Our study identifies key transcriptomic changes at the regenerating NMJ, providing a rich source of pro-regenerative factors with potential for alleviating the consequences of peripheral nerve injuries.

A spinal microglia population involved in remitting and relapsing neuropathic pain.

Neuropathic pain is often caused by injury and diseases that affect the somatosensory system. Although pain development has been well studied, pain recovery mechanisms remain largely unknown. Here, we found that CD11c-expressing spinal microglia appear after the development of behavioral pain hypersensitivity following nerve injury. Nerve-injured mice with spinal CD11c+ microglial depletion failed to recover spontaneously from this hypersensitivity. CD11c+ microglia expressed insulin-like growth factor-1 (IGF1), and interference with IGF1 signaling recapitulated the impairment in pain recovery. In pain-recovered mice, the depletion of CD11c+ microglia or the interruption of IGF1 signaling resulted in a relapse in pain hypersensitivity. Our findings reveal a mechanism for the remission and recurrence of neuropathic pain, providing potential targets for therapeutic strategies.

Changes of Functional, Morphological, and Inflammatory Reactions in Spontaneous Peripheral Nerve Reinnervation after Thermal Injury.

In recent decades, the use of energy-based devices has substantially increased the incidence of iatrogenic thermal injury to nerves (cauterization, etc.). While recovery of the nerve after thermal injury is important, the changes in neural structure, function, and peripheral inflammatory reactions postinjury remain unclear. This study is aimed at demonstrating the changes mentioned above during the acute, subacute, and chronic stages of nerve reinnervation after thermal injury. Spontaneous reinnervation was evaluated, including the neural structures, nerve conduction abilities, and muscle regeneration. These effects vary depending on the severity of thermal injury (slight, moderate, and severe). Peripheral inflammatory reactions, as impediments to reinnervation, were found in significant numbers 3 days after thermal injury, exhibiting high expression of IL-1ß and TNF-α, but low expression of IL-10. Our findings reveal the pathogenesis of peripheral nerve reinnervation after thermal injury, which will assist in selecting appropriate treatments in further research.

A nerve conduit filled with Wnt5a-loaded fibrin hydrogels promotes peripheral nerve regeneration.

AIMS: Peripheral nerve injury is a significant clinical problem with a substantial impact on quality of life, for which no optimal treatment has been found. This study aimed to analyze the effect and mechanism of Wnt5a-loaded fibrin hydrogel on a 10-mm rat sciatic nerve defect. METHODS: The Wnt5a-loaded fibrin hydrogel was synthesized by mixing a Wnt5a solution with thrombin and fibrinogen solutions. The loading capacity and release profile of Wnt5a-loaded fibrin hydrogel and the effect of Wnt5a on Schwann cells were evaluated in vitro. We also assessed the in vivo repair status via histological analysis of the regenerative nerve and gastrocnemius muscle, electrophysiological examination, gait analysis, and muscle wet weight. RESULTS: We developed a nerve conduit filled with Wnt5a-loaded fibrin hydrogel (Fn) as a sustained-release system to repair a 10-mm rat sciatic nerve defect. In vitro, Wnt5a could promote SC proliferation and the gene expression of vascular endothelial growth factor (VEGF), nerve growth factor (NGF), and cholinergic neurotrophic factor (CNTF), as well as the protein secretion of VEGF and NGF. In vivo, the Wnt5a/Fn group was superior to the hollow, fibrin hydrogel, and Wnt5a groups in terms of axonal growth, myelination, electrophysiological recovery, target organ innervation, and motor function recovery 12 weeks after the operation. CONCLUSION: The Wnt5a/Fn nerve conduit can promote peripheral nerve defect regeneration, with potential clinical applications. The mechanism for this may be the facilitation of multiple neurotrophin secretion, combining vascularization and neurotrophic growth cues.

Delayed inhibition of ERK and p38 attenuates neuropathic pain without affecting motor function recovery after peripheral nerve injury.

Peripheral nerve injuries (PNIs) often result in persistent neuropathic pain, seriously affecting quality of life. Existing therapeutic interventions for PNI-induced neuropathic pain are far from satisfactory. Extracellular signal-regulated kinases (ERKs) and p38 have been found to participate in triggering and maintaining PNI-induced neuropathic pain. However, ERK and p38 also contribute to axonal regeneration and motor function recovery after PNI, making it difficult to inhibit ERK and p38 for therapeutic purposes. In this study, we simultaneously characterized neuropathic pain and motor function recovery in a mouse sciatic nerve crush injury model to identify the time window for therapeutic interventions. We further demonstrated that delayed delivery of a combination of ERK and p38 inhibitors at three weeks after PNI could significantly alleviate PNI-induced neuropathic pain without affecting motor function recovery. Additionally, the combined use of these two inhibitors could suppress pain markedly better than either inhibitor alone, possibly reducing the required dose of each inhibitor and alleviating the side effects and risks of the inhibitors when used individually.

Effect of decorin protein administration on rat sciatic nerve injury: an experimental study.

INTRODUCTION: Peripheral nerve traumas are common injuries in young adult population. The myriad of techniques and medications have been defined to obtain better recovery but none of them was proved to have superior effect. This study aims to determine the anti-fibrotic effect of the decorin on sciatic nerve injury in order to enhance functional outcome. MATERIALS AND METHODS: 24 12-week-old male Sprague-Dawley rats (350-400 gr) were divided into four groups. The sciatic nerve was dissected and exposed; a full-thickness laceration was created 1.5 cm proximal to the bifurcation point and 1.5 cm distal to where it originated from the lumbosacral plexus. Motor and sensory tests were conducted before and after the operations for evaluating the nerve healing. RESULTS: There was a statistically significant difference between DCN bolus and PBS bolus group. (p<0.0001, p<0.05) in neuromotor tests. Increase of the latency was significantly lower in DCN bolus and infusion group when compared with the PBS bolus group. (p<0,001). All operated gastrocnemius muscles were atrophic compared with the contralateral side. The differences between the averages in the sciatic functional index, the improvement of the DCN infusion group was 8.6 units better than the PBS group and 4.4 units better than the DCN bolus group. When the amount of stimulation was 10 mV at the proximal segment in electromyography, there was no significant difference between the DCN bolus and sham groups. (p> 0.05, p = 0.6623). CONCLUSION: Decorin protein reduces the fibrosis and enhances the motor and sensory recovery both clinically and histologically. Despite the high cost, short half-life and production issues, this protein could be administered after the microsurgical repair but more studies are required to overcome the limitations.

Sigma-1 receptor increases intracellular calcium in cultured astrocytes and contributes to mechanical allodynia in a model of neuropathic pain.

Recent studies have revealed that glial sigma-1 receptor (Sig-1R) in the spinal cord may be a critical factor to mediate sensory function. However, the functional role of Sig-1R in astrocyte has not been clearly elucidated. Here, we determined whether Sig-1Rs modulate calcium responses in primary cultured astrocytes and pathological changes in spinal astrocytes, and whether they contribute to pain hypersensitivity in naïve mice and neuropathic pain following chronic constriction injury (CCI) of the sciatic nerve in mice. Sig-1R was expressed in glial fibrillary acidic protein (GFAP)-positive cultured astrocytes. Treatment with the Sig-1R agonist, PRE-084 or neurosteroid dehydroepiandrosterone (DHEA) increased intracellular calcium responses in cultured astrocytes, and this increase was blocked by the pretreatment with the Sig-1R antagonist, BD-1047 or neurosteroid progesterone. Intrathecal administration of PRE-084 or DHEA for 10 days induced mechanical and thermal hypersensitivity and increased the number of Sig-1R-immunostained GFAP-positive cells in the superficial dorsal horn (SDH) region of the spinal cord in naïve mice, and these changes were inhibited by administration with BD-1047 or progesterone. In CCI mice, intrathecal administration of BD-1047 or progesterone at post-operative day 14 suppressed the developed mechanical allodynia and the number of Sig-1R-immunostained GFAP-positive cells that were increased in the SDH region of the spinal cord following CCI of the sciatic nerve. These results demonstrate that Sig-1Rs play an important role in the modulation of intracellular calcium responses in cultured astrocytes and pathological changes in spinal astrocytes and that administration of BD-1047 or progesterone alleviates the Sig-1R-induced pain hypersensitivity and the peripheral nerve injury-induced mechanical allodynia.

Analysis of Influencing Factors of Repair Effect after Peripheral Nerve Injury.

In order to improve the repair effect after peripheral nerve injury, this paper analyzes the related influencing factors. The regeneration of peripheral nerve includes two continuous and overlapping processes: the acute wound healing period and the axon seeking target tissue period. The complete and effective process of peripheral nerve regeneration includes the sprouting, growth and extension of regenerated axons, and the reconstruction of synaptic connections (neuromuscular junctions) with target organs to realize the reinnervation of nerves and restore function. This process includes three indicators of success in regeneration: structural reconstruction, metabolic regeneration, and functional recovery. In order to improve the repair effect of peripheral nerve injury, relevant influencing factors can be analyzed, and effective improvement of these influencing factors can improve the recovery effect of peripheral nerve injury. Finally, this paper analyzes multiple factors to provide theoretical references for follow-up clinical diagnosis and treatment.

ZNF382 controls mouse neuropathic pain via silencer-based epigenetic inhibition of Cxcl13 in DRG neurons.

Nerve injury-induced changes of gene expression in dorsal root ganglion (DRG) are critical for neuropathic pain genesis. However, how these changes occur remains elusive. Here we report the down-regulation of zinc finger protein 382 (ZNF382) in injured DRG neurons after nerve injury. Rescuing this down-regulation attenuates nociceptive hypersensitivity. Conversely, mimicking this down-regulation produces neuropathic pain symptoms, which are alleviated by C-X-C motif chemokine 13 (CXCL13) knockdown or its receptor CXCR5 knockout. Mechanistically, an identified cis-acting silencer at distal upstream of the Cxcl13 promoter suppresses Cxcl13 transcription via binding to ZNF382. Blocking this binding or genetically deleting this silencer abolishes the ZNF382 suppression on Cxcl13 transcription and impairs ZNF382-induced antinociception. Moreover, ZNF382 down-regulation disrupts the repressive epigenetic complex containing histone deacetylase 1 and SET domain bifurcated 1 at the silencer-promoter loop, resulting in Cxcl13 transcriptional activation. Thus, ZNF382 down-regulation is required for neuropathic pain likely through silencer-based epigenetic disinhibition of CXCL13, a key neuropathic pain player, in DRG neurons.

Negative regulation by proBDNF signaling of peripheral neurogenesis in the sensory ganglia of adult rats.

Neurogenesis in the adult brain is well recognized and plays a critical role in the maintenance of brain function and homeostasis. However, whether neurogenesis also occurs in the adult peripheral nervous system remains unknown. Here, using sensory ganglia (dorsal root ganglia, DRGs) as a model, we show that neurogenesis also occurs in the peripheral nervous system, but in a manner different from that in the central nervous system. Satellite glial cells (SGCs) express the neuronal precursor markers Nestin, POU domain, class 4, transcription factor 1, and p75 pan-neurotrophin receptor. Following sciatic nerve injury, the suppression of endogenous proBDNF by proBDNF antibodies resulted in the transformation of proliferating SGCs into doublecortin-positive cells in the DRGs. Using purified SGCs migrating out from the DRGs, the inhibition of endogenous proBDNF promoted the conversion of SGCs into neuronal phenotypes in vitro. Our findings suggest that SGCs are neuronal precursors, and that proBDNF maintains the SGC phenotype. Furthermore, the suppression of proBDNF signaling is necessary for neuronal phenotype acquisition by SGCs. Thus, we propose that peripheral neurogenesis may occur via the direct conversion of SGCs into neurons, and that this process is negatively regulated by proBDNF.

Brief Electrical Stimulation Accelerates Axon Regeneration and Promotes Recovery Following Nerve Transection and Repair in Mice.

BACKGROUND: Clinical outcomes following nerve injury repair can be inadequate. Pulsed-current electrical stimulation (ES) is a therapeutic method that facilitates functional recovery by accelerating axon regeneration. However, current clinical ES protocols involve the application of ES for 60 minutes during surgery, which can increase operative complexity and time. Shorter ES protocols could be a strategy to facilitate broader clinical adoption. The purpose of the present study was to determine if a 10-minute ES protocol could improve outcomes. METHODS: C57BL/6J mice were randomized to 3 groups: no ES, 10 minutes of ES, and 60 minutes of ES. In all groups, the sciatic nerve was transected and repaired, and, in the latter 2 groups, ES was applied after repair. Postoperatively, changes to gene expression from dorsal root ganglia were measured after 24 hours. The number of motoneurons regenerating axons was determined by retrograde labeling at 7 days. Histomorphological analyses of the nerve were performed at 14 days. Function was evaluated serially with use of behavioral tests up to 56 days postoperatively, and relative muscle weight was evaluated. RESULTS: Compared with the no-ES group, both ES groups demonstrated increased regeneration-associated gene expression within dorsal root ganglia. The 10-minute and 60-minute ES groups demonstrated accelerated axon regeneration compared with the no-ES group based on increased numbers of labeled motoneurons regenerating axons (mean difference, 202.0 [95% confidence interval (CI), 17.5 to 386.5] and 219.4 [95% CI, 34.9 to 403.9], respectively) and myelinated axon counts (mean difference, 559.3 [95% CI, 241.1 to 877.5] and 339.4 [95% CI, 21.2 to 657.6], respectively). The 10-minute and 60-minute ES groups had improved behavioral recovery, including on grid-walking analysis, compared with the no-ES group (mean difference, 11.9% [95% CI, 3.8% to 20.0%] and 10.9% [95% CI, 2.9% to 19.0%], respectively). There was no difference between the ES groups in measured outcomes. CONCLUSIONS: A 10-minute ES protocol accelerated axon regeneration and facilitated functional recovery. CLINICAL RELEVANCE: The brief (10-minute) ES protocol provided similar benefits to the 60-minute protocol in an acute sciatic nerve transection/repair mice model and merits further studies.

Contralateral Projection of Anterior Cingulate Cortex Contributes to Mirror-Image Pain.

Long-term limb nerve injury often leads to mirror-image pain (MIP), an abnormal pain sensation in the limb contralateral to the injury. Although it is clear that MIP is mediated in part by central nociception processing, the underlying mechanisms remain poorly understood. The anterior cingulate cortex (ACC) is a key brain region that receives relayed peripheral nociceptive information from the contralateral limb. In this study, we induced MIP in male mice, in which a unilateral chronic constrictive injury of the sciatic nerve (CCI) induced a decreased nociceptive threshold in both hind limbs and an increased number of c-Fos-expressing neurons in the ACC both contralateral and ipsilateral to the injured limb. Using viral-mediated projection mapping, we observed that a portion of ACC neurons formed monosynaptic connections with contralateral ACC neurons. Furthermore, the number of cross-callosal projection ACC neurons that exhibited c-Fos signal was increased in MIP-expressing mice, suggesting enhanced transmission between ACC neurons of the two hemispheres. Moreover, selective inhibition of the cross-callosal projection ACC neurons contralateral to the injured limb normalized the nociceptive sensation of the uninjured limb without affecting the increased nociceptive sensation of the injured limb in CCI mice. In contrast, inhibition of the non-cross-callosal projection ACC neurons contralateral to the injury normalized the nociceptive sensation of the injured limb without affecting the MIP exhibited in the uninjured limb. These results reveal a circuit mechanism, namely, the cross-callosal projection of ACC between two hemispheres, that contributes to MIP and possibly other forms of contralateral migration of pain sensation.SIGNIFICANCE STATEMENT Mirror-image pain (MIP) refers to the increased pain sensitivity of the contralateral body part in patients with chronic pain. This pathology requires central processing, yet the mechanisms are less known. Here, we demonstrate that the cross-callosal projection neurons in the anterior cingulate cortex (ACC) contralateral to the injury contribute to MIP exhibited in the uninjured limb, but do not affect nociceptive sensation of the injured limb. In contrast, the non-cross-callosal projection neurons in the ACC contralateral to the injury contribute to nociceptive sensation of the injured limb, but do not affect MIP exhibited in the uninjured limb. Our study depicts a novel cross-callosal projection of ACC that contributes to MIP, providing a central mechanism for MIP in chronic pain state.

Intrinsic positional memory guides target-specific axon regeneration in the zebrafish vagus nerve.

Regeneration after peripheral nerve damage requires that axons re-grow to the correct target tissues in a process called target-specific regeneration. Although much is known about the mechanisms that promote axon re-growth, re-growing axons often fail to reach the correct targets, resulting in impaired nerve function. We know very little about how axons achieve target-specific regeneration, particularly in branched nerves that require distinct targeting decisions at branch points. The zebrafish vagus motor nerve is a branched nerve with a well-defined topographic organization. Here, we track regeneration of individual vagus axons after whole-nerve laser severing and find a robust capacity for target-specific, functional re-growth. We then develop a new single-cell chimera injury model for precise manipulation of axon-environment interactions and find that (1) the guidance mechanism used during regeneration is distinct from the nerve's developmental guidance mechanism, (2) target selection is specified by neurons' intrinsic memory of their position within the brain, and (3) targeting to a branch requires its pre-existing innervation. This work establishes the zebrafish vagus nerve as a tractable regeneration model and reveals the mechanistic basis of target-specific regeneration.

Injury-Induced HSP27 Expression in Peripheral Nervous Tissue Is Not Associated with Any Alteration in Axonal Outgrowth after Immediate or Delayed Nerve Repair.

We investigated injury-induced heat shock protein 27 (HSP27) expression and its association to axonal outgrowth after injury and different nerve repair models in healthy Wistar and diabetic Goto-Kakizaki rats. By immunohistochemistry, expression of HSP27 in sciatic nerves and DRG and axonal outgrowth (neurofilaments) in sciatic nerves were analyzed after no, immediate, and delayed (7-day delay) nerve repairs (7- or 14-day follow-up). An increased HSP27 expression in nerves and in DRG at the uninjured side was associated with diabetes. HSP27 expression in nerves and in DRG increased substantially after the nerve injuries, being higher at the site where axons and Schwann cells interacted. Regression analysis indicated a positive influence of immediate nerve repair compared to an unrepaired injury, but a shortly delayed nerve repair had no impact on axonal outgrowth. Diabetes was associated with a decreased axonal outgrowth. The increased expression of HSP27 in sciatic nerve and DRG did not influence axonal outgrowth. Injured sciatic nerves should appropriately be repaired in healthy and diabetic rats, but a short delay does not influence axonal outgrowth. HSP27 expression in sciatic nerve or DRG, despite an increase after nerve injury with or without a repair, is not associated with any alteration in axonal outgrowth.

Electrophysiological and anatomical characterization of synaptic remodeling in the mouse whisker thalamus.

In the central nervous system, developmental and pathophysiologic conditions cause a large-scale reorganization of functional connectivity of neural circuits. Here, by using a mouse model for peripheral sensory nerve injury, we present a protocol for combined electrophysiological and anatomical techniques to identify neural basis of synaptic remodeling in the mouse whisker thalamus. Our protocol provides comprehensive approaches to analyze both structural and functional components of synaptic remodeling. For complete details on the use and execution of this protocol, please refer to Ueta and Miyata, (2021).

C-terminal domain small phosphatase 1 (CTDSP1) regulates growth factor expression and axonal regeneration in peripheral nerve tissue.

Peripheral Nerve Injury (PNI) represents a major clinical and economic burden. Despite the ability of peripheral neurons to regenerate their axons after an injury, patients are often left with motor and/or sensory disability and may develop chronic pain. Successful regeneration and target organ reinnervation require comprehensive transcriptional changes in both injured neurons and support cells located at the site of injury. The expression of most of the genes required for axon growth and guidance and for synapsis formation is repressed by a single master transcriptional regulator, the Repressor Element 1 Silencing Transcription factor (REST). Sustained increase of REST levels after injury inhibits axon regeneration and leads to chronic pain. As targeting of transcription factors is challenging, we tested whether modulation of REST activity could be achieved through knockdown of carboxy-terminal domain small phosphatase 1 (CTDSP1), the enzyme that stabilizes REST by preventing its targeting to the proteasome. To test whether knockdown of CTDSP1 promotes neurotrophic factor expression in both support cells located at the site of injury and in peripheral neurons, we transfected mesenchymal progenitor cells (MPCs), a type of support cells that are present at high concentrations at the site of injury, and dorsal root ganglion (DRG) neurons with REST or CTDSP1 specific siRNA. We quantified neurotrophic factor expression by RT-qPCR and Western blot, and brain-derived neurotrophic factor (BDNF) release in the cell culture medium by ELISA, and we measured neurite outgrowth of DRG neurons in culture. Our results show that CTDSP1 knockdown promotes neurotrophic factor expression in both DRG neurons and the support cells MPCs, and promotes DRG neuron regeneration. Therapeutics targeting CTDSP1 activity may, therefore, represent a novel epigenetic strategy to promote peripheral nerve regeneration after PNI by promoting the regenerative program repressed by injury-induced increased levels of REST in both neurons and support cells.

Determining the real site of peroneal nerve injury with knee dislocation: Earlierier is easier.

Common peroneal nerve (CPN) injury is a recognised complication of traumatic knee dislocation with a direct association between the degree of ligamentous injury and the degree of CPN injury. It is essential explore and repair these injuries in good time to reduce morbidity. Often exploration only involves the portion of this nerve associated with the joint as it courses around the fibular head. However, a recent case highlighted the importance of proximal exploration to its branching point from the sciatic nerve, a known point of fragility, even if other defects have been identified.

BDNF produced by cerebral microglia promotes cortical plasticity and pain hypersensitivity after peripheral nerve injury.

Peripheral nerve injury-induced mechanical allodynia is often accompanied by abnormalities in the higher cortical regions, yet the mechanisms underlying such maladaptive cortical plasticity remain unclear. Here, we show that in male mice, structural and functional changes in the primary somatosensory cortex (S1) caused by peripheral nerve injury require neuron-microglial signaling within the local circuit. Following peripheral nerve injury, microglia in the S1 maintain ramified morphology and normal density but up-regulate the mRNA expression of brain-derived neurotrophic factor (BDNF). Using in vivo two-photon imaging and Cx3cr1CreER;Bdnfflox mice, we show that conditional knockout of BDNF from microglia prevents nerve injury-induced synaptic remodeling and pyramidal neuron hyperactivity in the S1, as well as pain hypersensitivity in mice. Importantly, S1-targeted removal of microglial BDNF largely recapitulates the beneficial effects of systemic BDNF depletion on cortical plasticity and allodynia. Together, these findings reveal a pivotal role of cerebral microglial BDNF in somatosensory cortical plasticity and pain hypersensitivity.