Sciatic Nerve Crush Injury Model Research Articles

GCPII Inhibition Promotes Remyelination after Peripheral Nerve Injury in Aged Mice.

Peripheral nerve injuries (PNIs) represent a significant clinical challenge, particularly in elderly populations where axonal remyelination and regeneration are impaired. Developing therapies to enhance these processes is crucial for improving PNI repair outcomes. Glutamate carboxypeptidase II (GCPII) is a neuropeptidase that plays a pivotal role in modulating glutamate signaling through its enzymatic cleavage of the abundant neuropeptide N-acetyl aspartyl glutamate (NAAG) to liberate glutamate. Within the PNS, GCPII is expressed in Schwann cells and activated macrophages, and its expression is amplified with aging. In this study, we explored the therapeutic potential of inhibiting GCPII activity following PNI. We report significant GCPII protein and activity upregulation following PNI, which was normalized by the potent and selective GCPII inhibitor 2-(phosphonomethyl)-pentanedioic acid (2-PMPA). In vitro, 2-PMPA robustly enhanced myelination in dorsal root ganglion (DRG) explants. In vivo, using a sciatic nerve crush injury model in aged mice, 2-PMPA accelerated remyelination, as evidenced by increased myelin sheath thickness and higher numbers of remyelinated axons. These findings suggest that GCPII inhibition may be a promising therapeutic strategy to enhance remyelination and potentially improve functional recovery after PNI, which is especially relevant in elderly PNI patients where this process is compromised.

MSC-derived mitochondria promote axonal regeneration via Atf3 gene up-regulation by ROS induced DNA double strand breaks at transcription initiation region

BackgroundThe repair of peripheral nerve injury poses a clinical challenge, necessitating further investigation into novel therapeutic approaches. In recent years, bone marrow mesenchymal stromal cell (MSC)-derived mitochondrial transfer has emerged as a promising therapy for cellular injury, with reported applications in central nerve injury. However, its potential therapeutic effect on peripheral nerve injury remains unclear.MethodsWe established a mouse sciatic nerve crush injury model. Mitochondria extracted from MSCs were intraneurally injected into the injured sciatic nerves. Axonal regeneration was observed through whole-mount nerve imaging. The dorsal root ganglions (DRGs) corresponding to the injured nerve were harvested to test the gene expression, reactive oxygen species (ROS) levels, as well as the degree and location of DNA double strand breaks (DSBs).ResultsThe in vivo experiments showed that the mitochondrial injection therapy effectively promoted axon regeneration in injured sciatic nerves. Four days after injection of fluorescently labeled mitochondria into the injured nerves, fluorescently labeled mitochondria were detected in the corresponding DRGs. RNA-seq and qPCR results showed that the mitochondrial injection therapy enhanced the expression of Atf3 and other regeneration-associated genes in DRG neurons. Knocking down of Atf3 in DRGs by siRNA could diminish the therapeutic effect of mitochondrial injection. Subsequent experiments showed that mitochondrial injection therapy could increase the levels of ROS and DSBs in injury-associated DRG neurons, with this increase being correlated with Atf3 expression. ChIP and Co-IP experiments revealed an elevation of DSB levels within the transcription initiation region of the Atf3 gene following mitochondrial injection therapy, while also demonstrating a spatial proximity between mitochondria-induced DSBs and CTCF binding sites.ConclusionThese findings suggest that MSC-derived mitochondria injected into the injured nerves can be retrogradely transferred to DRG neuron somas via axoplasmic transport, and increase the DSBs at the transcription initiation regions of the Atf3 gene through ROS accumulation, which rapidly release the CTCF-mediated topological constraints on chromatin interactions. This process may enhance spatial interactions between the Atf3 promoter and enhancer, ultimately promoting Atf3 expression. The up-regulation of Atf3 induced by mitochondria further promotes the expression of downstream regeneration-associated genes and facilitates axon regeneration.

Differentiated mesenchymal stem cells-derived exosomes immobilized in decellularized sciatic nerve hydrogels for peripheral nerve repair

Peripheral nerve injury (PNI) and the limitations of current treatments often result in incomplete sensory and motor function recovery, which significantly impact the patient's quality of life. While exosomes (Exo) derived from stem cells and Schwann cells have shown promise on promoting PNI repair following systemic administration or intraneural injection, achieving effective local and sustained Exo delivery holds promise to treat local PNI and remains challenging. In this study, we developed Exo-loaded decellularized porcine nerve hydrogels (DNH) for PNI repair. We successfully isolated Exo from differentiated human adipose-derived mesenchymal stem cells (hADMSC) with a Schwann cell-like phenotype (denoted as dExo). These dExo were further combined with polyethylenimine (PEI), and DNH to create polyplex hydrogels (dExo-loaded pDNH). At a PEI content of 0.1%, pDNH showed cytocompatibility for hADMSCs and supported neurite outgrowth of dorsal root ganglions. The sustained release of dExos from dExo-loaded pDNH persisted for at least 21 days both in vitro and in vivo. When applied around injured nerves in a mouse sciatic nerve crush injury model, the dExo-loaded pDNH group significantly improved sensory and motor function recovery and enhanced remyelination compared to dExo and pDNH only groups, highlighting the synergistic regenerative effects. Interestingly, we observed a negative correlation between the number of colony-stimulating factor-1 receptor (CSF-1R) positive cells and the extent of PNI regeneration at the 21-day post-surgery stage. Subsequent in vitro experiments demonstrated the potential involvement of the CSF-1/CSF-1R axis in Schwann cells and macrophage interaction, with dExo effectively downregulating CSF-1/CSF-1R signaling.

Sleep disturbance correlated with severity of neuropathic pain in sciatic nerve crush injury model.

The association between sleep and pain has been investigated widely. However, inconsistent results from animal studies compared with human data show the need for a validated animal model in the sleep-pain association field. Our study aims to validate common neuropathic pain models as a tool for evaluating the sleep-pain association. Electrodes electroencephalogram (EEG) and electromyogram (EMG) were surgically implanted to measure sleep. The von Frey test was used to measure pain sensitivity. Following the baseline data acquisition, two pain-modelling procedures were performed: sciatic nerve crush injury (SCI) and common peroneal nerve ligation (CPL). Post-injury measurements were performed on days 1, 5, 10, and 15 post-surgery. The results presented decreased paw withdrawal thresholds and reduced NREM sleep duration in both models on the first post-surgery day. In the SCI model, NREM sleep duration was negatively correlated with paw withdrawal thresholds (p = 0.0466), but not in the CPL model. Wake alpha and theta EEG powers were also correlated with the pain threshold. The results confirm that the SCI model shows disturbed sleep patterns associated with increased pain sensitivity, suggesting it is a reliable tool for investigating sleep disturbances associated with neuropathic pain.

Cdon ablation in motor neurons causes age-related motor neuron degeneration and impaired sciatic nerve repair.

The functional deterioration and loss of motor neurons are tightly associated with degenerative motor neuron diseases and aging-related muscle wasting. Motor neuron diseases or aging-related muscle wasting in turn contribute to increased risk of adverse health outcomes in the elderly. Cdon (cell adhesion molecule-downregulated oncogene) belongs to the immunoglobulin superfamily of cell adhesion molecule and plays essential roles in multiple signalling pathways, including sonic hedgehog (Shh), netrin, and cadherin-mediated signalling. Cdon as a Shh coreceptor plays a critical role in motor neuron specification during embryonic development. However, its role in adult motor neuron function is unknown. Hb9-Cre recombinase-driven motor neuron-specific Cdon deficient mice (mnKO) and a compound mutant mice (mnKO::SOD1G93A ) were generated to investigate the role of Cdon in motor neuron degeneration. Motor neuron regeneration was examined by using a sciatic nerve crush injury model. To investigate the phenotype, physical activity, compound muscle action potential, immunostaining, and transmission electron microscopy were carried out. In the mechanism study, RNA sequencing and RNA/protein analyses were employed. Mice lacking Cdon in motor neurons exhibited middle age onset lethality and aging-related decline in motor function. In the sciatic nerve crush injury model, mnKO mice exhibited an impairment in motor function recovery evident by prolonged compound muscle action potential duration (4.63±0.35 vs. 3.93±0.22s for f/f, P<0.01) and physical activity. Consistently, neuromuscular junctions of mnKO muscles were incompletely occupied (49.79±5.74 vs. 79.39±3.77% fully occupied neuromuscular junctions for f/f, P<0.0001), suggesting an impaired reinnervation. The transmission electron microscopy analysis revealed that mnKO sciatic nerves had smaller axon diameter (0.88±0.13 vs. 1.43±0.48μm for f/f, P<0.0001) and myelination defects. RNA sequencing of mnKO lumbar spinal cords showed alteration in genes related to neurogenesis, inflammation and cell death. Among the altered genes, ErbB4 and FgfR expressions were significantly altered in mnKO as well as in Cdon-depleted NSC34 motor neuron cells. Consistently, Cdon-depleted NSC34 cells exhibited elevated levels of cleaved Caspase3 and γH2AX proteins, as well as Bax transcription. Cdon-depleted NSC34 cells also exhibited impaired activation of Akt in response to neuregulin-1 (NRG1) treatment. Our current data demonstrate the functional importance of Cdon in motor neuron function and nerve repair. Cdon ablation causes alterations in neurotrophin signalling that leads to motor neuron degeneration.

0261 Sleep Disturbance Reliably Predicted by Pain Sensitivity in Sciatic Nerve Crush Injury Model

Abstract Introduction A bi-directional relationship between sleep and neuropathic pain is of interest because of its impact on human health. Numerous studies in humans and animals have examined the association between sleep and neuropathic pain. However, animal studies showed inconsistent results compared to human data. Therefore, validation of an animal model for sleep-pain association research is needed. We examined the animal models to identify a best-fit model predicting sleep disturbances with the level of neuropathic pain. Methods Adult male C57BL/6J mice (n=7 per group) were implanted with electrodes for electroencephalogram (EEG) and electromyogram. After two weeks of recovery, we obtained baseline EEG data for 24 hours and evaluated the paw withdrawal threshold, a measure of pain sensitivity, by the von Frey test. Afterward, sciatic nerve crush injury (SCI) and common peroneal nerve ligation (CPL) were conducted to make the two different neuropathic pain models. Post-surgery sleep was recorded continuously for 24 hours, followed by von Frey tests. EEG recording during the light period and von Frey tests were repeated on post-surgery days 5, 10, and 15. Results Both SCI and CPL models showed lower paw withdrawal thresholds after the peripheral nerve injury. NREM sleep duration on post-surgery day 1 was reduced significantly compared to baseline in both SCI and CPL, but only SCI showed decreased REM sleep. There was a significant positive correlation between paw withdrawal threshold and NREM sleep duration in SCI (P&amp;lt; 0.0001) but not CPL. Also, wake alpha and theta EEG powers were correlated with pain threshold. Conclusion We confirmed that both models of neuropathic pain disturbed sleep patterns. Nevertheless, sleep disturbances were reliably predicted by the pain sensitivity in the SCI model. Hence, we suggest SCI as a reliable pain model for studying the mechanism of sleep-pain association. Support (if any)

Neurotropin® accelerates peripheral nerve regeneration in a rat sciatic nerve crush injury model

BackgroundPeripheral nerve injuries are common and serious conditions. The effect of Neurotropin® (NTP), a nonprotein extract derived from the inflamed skin of rabbits inoculated with vaccinia virus, on peripheral nerve regeneration has not been fully elucidated. However, it has analgesic properties via the activation of descending pain inhibitory systems. Therefore, the current study aimed to determine the effects of NTP on peripheral nerve regeneration. MethodsWe examined axonal outgrowth of dorsal root ganglion (DRG) neurons using immunocytochemistry in vitro. In addition, nerve regeneration was evaluated functionally, electrophysiologically, and histologically in a rat sciatic nerve crush injury model in vivo. Furthermore, gene expression of neurotrophic factors in the injured sciatic nerves and DRGs was evaluated. ResultsIn the dorsal root ganglion neurons in vitro, NTP promoted axonal outgrowth at a concentration of 10 mNU/mL. Moreover, the systemic administration of NTP contributed to the recovery of motor and sensory function at 2 weeks, and of sensory function, nerve conduction velocity, terminal latency, and axon-remyelination 4 weeks after sciatic nerve injury. In the gene expression assessment, insulin-like growth factor 1 and vascular endothelial growth factor expressions were increased in the injured sciatic nerve 2 days postoperatively. ConclusionsTherefore, NTP might be effective in not only treating chronic pain but also promoting peripheral nerve regeneration after injury.

Evaluation methods of a rat sciatic nerve crush injury model.

The rat sciatic nerve crush injury model is one of the most commonly used models to research peripheral nerve injury (PNI), however, the evaluation of the model preparation lacks exact standards. This study aimed to investigate accurately assessment methods for research concerning the rat sciatic nerve crush injury. The sciatic nerve crush injury model of was performed using the FST toothless forceps. The corresponding locations and pressures of different ratchet strengths were assessed by using CMAP, behavioral, and morphological methods. In each group of PNI, motor and sensory functions were gradually restricted on the injured side of rats as the applied pressure increased. CMAP was more sensitive to nerve injury arising out of the force values obtained from the forceps. As a sensitive indicator for PNI, the neuroelectrophysiological examination was more likely to reflect the morphological changes of injured nerves. These findings may provide a standardized approach to sciatic crush injury modelling.

Raman spectroscopy and sciatic functional index (SFI) after low-level laser therapy (LLLT) in a rat sciatic nerve crush injury model.

Axonotmesis causes sensorimotor and neurofunctional deficits, and its regeneration can occur slowly or not occur if not treated appropriately. Low-level laser therapy (LLLT) promotes nerve regeneration with the proliferation of myelinating Schwann cells to recover the myelin sheath and the production of glycoproteins for endoneurium reconstruction. This study aimed to evaluate the effects of LLLT on sciatic nerve regeneration after compression injury by means of the sciatic functional index (SFI) and Raman spectroscopy (RS). For this, 64 Wistar rats were divided into two groups according to the length of treatment: 14days (n = 32) and 21days (n = 32). These two groups were subdivided into four sub-groups of eight animals each (control 1; control 2; laser 660nm; laser 808nm). All animals had surgical exposure to the sciatic nerve, and only control 1 did not suffer nerve damage. To cause the lesion in the sciatic nerve, compression was applied with a Kelly clamp for 6s. The evaluation of sensory deficit was performed by the painful exteroceptive sensitivity (PES) and neuromotor tests by the SFI. Laser 660nm and laser 808nm sub-groups were irradiated daily (100 mW, 40s, energy density of 133J/cm2). The sciatic nerve segment was removed for RS analysis. The animals showed accentuated sensory and neurofunctional deficit after injury and their rehabilitation occurred more effectively in the sub-groups treated with 660nm laser. Control 2 sub-group did not obtain functional recovery of gait. The RS identified sphingolipids (718, 1065, and 1440cm-1) and collagen (700, 852, 1004, 1270, and 1660cm-1) as biomolecular characteristics of sciatic nerves. Principal component analysis revealed important differences among sub-groups and a directly proportional correlation with SFI, mainly in the sub-group laser 660nm treated for 21days. In the axonotmesis-type lesion model presented herein, the 660nm laser was more efficient in neurofunctional recovery, and the Raman spectra of lipid and protein properties were attributed to the basic biochemical composition of the sciatic nerve.

Enhancing Membrane Repair in Neuronal Cell Types as a Potential Therapeutic for Neurodegenerative Diseases

Cell membrane repair is an essential cellular process to repair damage to the membrane and maintain the integrity of the cell membrane. Impaired membrane resealing kinetics can potentially lead to neurodegenerative diseases. Enhancing membrane repair via therapeutic intervention could minimize neurodegeneration in neuronal disease states. Recombinant human MG53 (rhMG53) and poloxamers have been an effective therapeutic to enhance membrane repair in muscle and non‐muscle cell types. Here, we aimed to assess if the membrane repair response is active and the efficacy of enhancing membrane resealing in neuronal cells. To assess if neuronal cells have an active membrane repair response, mouse neuroblastoma N2a cells were transfected with GFP or GFP‐MG53. MG53 localization was tracked following multiphoton infrared laser injury. N2a cells were transfected with GFP or GFP‐MG53, and subjected to multiphoton infrared laser injury to investigate if MG53 expression enhances membrane resealing following damage. An infrared laser was used to damage the cell membrane of N2a cells and primary mouse dorsal root ganglion neurons (DRG) in the presence of FM4‐64 dye. To test the efficacy of therapeutics, N2as and DRGs were treated with 1μM rhMG53 or 100μM Poloxamer 188 (P188) and challenged with the multiphoton laser injury. Lastly, the therapeutic potential of rhMG53 was tested in vivo with a sciatic nerve crush injury model. C57Bl/6 mice sciatic nerves were mechanically crushed for 10 seconds and then injected with 1μL rhMG53 (1mg/mL) or saline. The sciatic nerves were harvested and immunostained with an axonal regeneration marker, SCG10. SCG10 staining intensity was measured to calculate the regeneration index. Overall, we observed MG53 trafficking to the injury site which indicates there is an activate membrane repair mechanism within neuronal cells. Therapeutic levels of rhMG53 and P188 increased membrane resealing in both N2as and DRGs. Lastly, rhMG53‐treated sciatic nerves displayed a two‐fold increase in regenerative capacity following sciatic nerve crush injury compared to the saline vehicle control. These results illustrate an active membrane repair process in neuronal cells and potential for therapeutic intervention in the context of neuronal diseases, specifically neurodegenerative diseases.

The Effect of Thymoquinone Administration on Local Immunoglobulin-G Levels of Rattus norvegicus Strain Wistar Sciatic Nerve Crush Injury Model

BACKGROUND: Immunoglobulin-G (IgG) is a product of the initial response to secondary immune response, which accumulates in distal segment of the nerve after crush injury. Thymoquinone modulates the adaptive immune response. Effect of thymoquinone administration on local IgG levels of Rattus norvegicus Wistar rats sciatic nerve crush injury model has not been elucidated.METHODS: This was an experimental study, with 63 Rattus norvegicus Wistar rats that divided into 9 groups. Three groups were given placebo, 3 groups were given 100 mg/kg/day thymoquinone, and 3 groups were given 250 mg/kg/day thymoquinone. The rats were terminated based on the assigned group at 5x24, 6x24, and 7x24 hours and then the IgG levels were measured using sandwich enzyme-linked immunosorbent assay (ELISA).RESULTS: There was a significant difference in IgG levels after administration of 100 and 250 mg/kg/day thymoquinone at 5x24 hours and 7x24 hours post-injury compared to the rats that were given no treatment. A significant difference of IgG levels was also found after administration of 100 mg/kg/day thymoquinone group at 6x24 hours post-injury. Critical point of decreasing local IgG of all groups happened at 6x24 hours after injury, however, there was no significant difference in the median levels of thymoquinone at doses of 100 mg/kg and 250 mg/kg.CONCLUSION: Local IgG levels in distal segment of the sciatic nerve crush injury is lower in rats that were given 100 mg/kg thymoquinone treatment compared to the rats that receive no thymoquinone treatment since 5x24 hours after injury. Thymoquione administration should be given immediately after the crush injury until before 6x24 hours post-injury to decrease antibodies in degeneration process.KEYWORDS: thymoquinone, immunoglobulin-G, crush injury, sciatic nerve

Sustained delivery of vascular endothelial growth factor mediated by bioactive methacrylic anhydride hydrogel accelerates peripheral nerve regeneration after crush injury.

Neurotrophic factors, currently administered orally or by intravenous drip or intramuscular injection, are the main method for the treatment of peripheral nerve crush injury. However, the low effective drug concentration arriving at the injury site results in unsatisfactory outcomes. Therefore, there is an urgent need for a treatment method that can increase the effective drug concentration in the injured area. In this study, we first fabricated a gelatin modified by methacrylic anhydride hydrogel and loaded it with vascular endothelial growth factor that allowed the controlled release of the neurotrophic factor. This modified gelatin exhibited good physical and chemical properties, biocompatibility and supported the adhesion and proliferation of RSC96 cells and human umbilical vein endothelial cells. When injected into the epineurium of crushed nerves, the composite hydrogel in the rat sciatic nerve crush injury model promoted nerve regeneration, functional recovery and vascularization. The results showed that the modified gelatin gave sustained delivery of vascular endothelial growth factors and accelerated the repair of crushed peripheral nerves.

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.

Effects of tamoxifen therapy on sciatic nerve crush injury: An experimental study in rats.

This study aimed to determine the effects of tamoxifen on sciatic nerve crush injury in a rat model using histopathological, histomorphometric, and immunohistochemical approaches. In this study, 24 male Sprague-Dawley rats aged of 5 to 7 weeks and weighing between 300 g and 400 g were used. The rats were randomly divided into 3 groups: control (group C), sciatic nerve injury (group SNI), and sciatic nerve injury with tamoxifen (group SNT). The sciatic nerve crush injury model was performed using the De Koning's crush force method. In group C, only a skin incision was made and then the skin was sutured. In group SNI, the injury model was performed but no treatment was applied. In group SNT, the injury model was executed, and then 40 mg/kg/day tamoxifen was given for 4 weeks by intraperitoneal methods. At the end of 4 weeks, all animals were killed using high doses of an anesthetic. Approximately, 2-cm sciatic nerve samples were obtained for histopathological, histomorphometric, and immunohistochemical analyses using the old skin incision. In the histopathological examination, vascular congestion and density of vacuolization were significantly lower in group SNT than in group SNI (p<0.05). In the histomorphometric examination, the mean sciatic nerve diameter was 306±62 µm in group C, 510±42 µm in group SNI, and 204±23 µm in group SNT. A significant difference was observed in the sciatic nerve diameter measurements among the 3 groups (p<0.05). In pairwise comparisons, the mean sciatic nerve diameter was significantly lower in group SNT than in group SNI (p=0.00002). Sciatic nerve diameter measurements of both groups were found to be significantly higher than group C (p<0.05). The mean epineurium thickness was 17±0.8 µm in group C, 32±2.5 µm in group SNI, and 17±0.8 µm in group SNT. A significant difference was observed in the epineurium thickness measurements among the 3 groups (p<0.05). In pairwise comparisons, the epineurium thickness was significantly higher in group SNI than in groups SNT and C (p<0.05). In the immunohistochemical analysis, S100 immunoreactivity was found significantly higher in group SNI than in the other 2 groups (p<0.05). The histomorphometric, histopathological, and immunohistochemical data obtained from this study have shown that tamoxifen has a beneficial effect on sciatic nerve crush injury in the experimental rat model.

Nogo-C Inhibits Peripheral Nerve Regeneration by Regulating Schwann Cell Apoptosis and Dedifferentiation.

While Nogo protein demonstrably inhibits nerve regeneration in the central nervous system (CNS), its effect on Schwann cells in peripheral nerve repair and regeneration following sciatic nerve injury remains unknown. In this research, We assessed the post-injury expression of Nogo-C in an experimental mouse model of sciatic nerve-crush injury. Nogo-C knockout (Nogo-C–/–) mouse was generated to observe the effect of Nogo-C on sciatic nerve regeneration, Schwann cell apoptosis, and myelin disintegration after nerve injury, and the effects of Nogo-C on apoptosis and dedifferentiation of Schwann cells were observed in vitro. We found that the expression of Nogo-C protein at the distal end of the injured sciatic nerve increased in wild type (WT) mice. Compared with the injured WT mice, the proportion of neuronal apoptosis was significantly diminished and the myelin clearance rate was significantly elevated in injured Nogo-C–/– mice; the number of nerve fibers regenerated and the degree of myelination were significantly elevated in Nogo-C–/– mice on Day 14 after injury. In addition, the recovery of motor function was significantly accelerated in the injured Nogo-C–/– mice. The overexpression of Nogo-C in primary Schwann cells using adenovirus-mediated gene transfer promoted Schwann cells apoptosis. Nogo-C significantly reduced the ratio of c-Jun/krox-20 expression, indicating its inhibition of Schwann cell dedifferentiation. Above all, we hold the view that the expression of Nogo-C increases following peripheral nerve injury to promote Schwann cell apoptosis and inhibit Schwann cell dedifferentiation, thereby inhibiting peripheral nerve regeneration.

Neurotrophic effects of dental pulp stem cells in repair of peripheral nerve after crush injury.

BACKGROUNDNerve diseases and injuries, which are usually accompanied by motor or sensory dysfunction and disorder, impose a heavy burden upon patients and greatly reduce their quality of life. Dental pulp stem cells (DPSCs), derived from the neural crest, have many characteristics that are similar to those of neural cells, indicating that they can be an ideal source for neural repair.AIMTo explore the potential roles and molecular mechanisms of DPSCs in crushed nerve recovery.METHODSDPSCs were isolated, cultured, and identified by multilineage differentiation and flow cytometry. Western blot and immunofluorescent staining were applied to analyze the expression levels of neurotrophic proteins in DPSCs after neural induction. Then, we collected the secretions of DPSCs. We analyzed their effects on RSC96 cell proliferation and migration by CCK8 and transwell assays. Finally, we generated a sciatic nerve crush injury model in vivo and used the sciatic function index, walking track analysis, muscle weight, and hematoxylin & eosin (H&E) staining to further evaluate the nerve repair ability of DPSCs.RESULTSDPSCs highly expressed several specific neural markers, including GFAP, S100, Nestin, P75, and NF200, and were inclined toward neural differentiation. Furthermore, neural-induced DPSCs (N-DPSCs) could express neurotrophic factors, including NGF, BDNF, and GDNF. The secretions of N-DPSCs could enhance the proliferation and migration of Schwann cells. In vivo, both DPSC and N-DPSC implants alleviated gastrocnemius muscle atrophy. However, in terms of anatomy and motor function, as shown by H&E staining, immunofluorescent staining, and walking track analyses, the repair effects of N-DPSCs were more sustained, potent, and effective than those of DPSCs and the controls. CONCLUSIONIn summary, this study demonstrated that DPSCs are inclined to differentiate into neural cells. N-DPSCs express neurotrophic proteins that could enhance the proliferation and migration of SCs. Furthermore, our results suggested that N-DPSCs could help crushed nerves with functional recovery and anatomical repair in vivo. Thus, DPSCs or N-DPSCs could be a promising therapeutic cell source for peripheral nerve repair and regeneration.

Composite nanofibers incorporating alpha lipoic acid and atorvastatin provide neuroprotection after peripheral nerve injury in rats

Despite the new treatment strategies within the last 30 years, peripheral nerve injury (PNI) is still a worldwide clinical problem. The incidence rate of PNIs is 1 in 1000 individuals per year. In this study, we designed a composite nanoplatform for dual therapy in peripheral nerve injury and investigated the in-vivo efficacy in rat sciatic nerve crush injury model. Alpha-lipoic acid (ALA) was loaded into poly lactic-co-glycolic acid (PLGA) electrospun nanofibers which would release the drug in a faster manner and atorvastatin (ATR) loaded chitosan (CH) nanoparticles were embedded into PLGA nanofibers to provide sustained release. Sciatic nerve crush was generated via Yasargil aneurism clip with a holding force of 50 g/cm2. Nanofiber formulations were administered to the injured nerve immediately after trauma. Functional recovery of operated rat hind limb was evaluated using the sciatic functional index (SFI), extensor postural thrust (EPT), withdrawal reflex latency (WRL) and Basso, Beattie, and Bresnahan (BBB) test up to one month in the post-operative period at different time intervals. In addition to functional recovery assessments, ultrastructural and biochemical analyses were carried out on regenerated nerve fibers. L-929 mouse fibroblast cell line and B35 neuroblastoma cell line were used to investigate the cytotoxicity of nanofibers before in-vivo experiments. The neuroprotection potential of these novel nanocomposite fiber formulations has been demonstrated after local implantation of composite nanofiber sheets incorporating ALA and ATR, which contributed to the recovery of the motor and sensory function and nerve regeneration in a rat sciatic nerve crush injury model.

Enhancement of sciatic nerve regeneration with dual delivery of vascular endothelial growth factor and nerve growth factor genes

BackgroundPeripheral nerve injury is one common clinical disease worldwide, in which sciatic nerve is anatomically the most challenging to regenerate given its length and large cross-sectional area. For the present, autologous nerve grafting remains to be the most ideal strategy when treating with sciatic nerve injury. However, this method sacrifices healthy nerves and requires highly intensive surgery, still calling for other advanced alternatives for nerve grafting.ResultsIn this study, we utilized previously well-established gene delivery system to dually deliver plasmid DNA (pDNA) encoding vascular endothelial growth factor (VEGF) and nerve growth factor (NGF), exploring therapeutics for sciatic nerve injury. Low-molecular-weight branched polyethylenimine (bPEI) was constructed as the backbone structure of gene vectors, and it was further crosslinked to synthesize degradable polycations via the conjugation of dialdehydes. Potential synergistic effect between VEGF and NGF proteins were observed on rat sciatic nerve crush injury model in this study.ConclusionsWe concluded that dual delivery of plasmid VEGF and NGF as gene therapy could enhance sciatic nerve regeneration.

3D Kinematic Analysis for the Functional Evaluation in the Rat Model of Sciatic Nerve Crush Injury.

Compared to the Sciatic Functional Index (SFI), kinematic analysis is a more reliable and sensitive method for performing functional evaluations of sciatic nerve injury rodent models. In this protocol, we describe a novel kinematic analysis method that uses a three-dimensional (3D) motion capture apparatus for functional evaluations using a rat sciatic nerve crush injury model. First, the rat is familiarized with treadmill walking. Markers are then attached to the designated bone landmarks and the rat is made to walk on the treadmill at the desired speed. Meanwhile, the posterior limb movements of the rat are recorded using four cameras. Depending on the software used, marker tracings are created using both automatic and manual modes and the desired data are produced after subtle adjustments. This method of kinematic analysis, which uses a 3D motion capture apparatus, offers numerous advantages, including superior precision and accuracy. Many more parameters can be investigated during the comprehensive functional evaluations. This method has several shortcomings that require consideration: The system is expensive, can be complicated to operate, and may produce data deviations due to skin shifting. Nevertheless, kinematic analysis using a 3D motion capture apparatus is useful for performing functional anterior and posterior limb evaluations. In the future, this method may become increasingly useful for generating accurate assessments of various traumas and diseases.

Nerve growth factor activates autophagy in Schwann cells to enhance myelin debris clearance and to expedite nerve regeneration.

Rationale: Autophagy in Schwann cells (SCs) is crucial for myelin debris degradation and clearance following peripheral nerve injury (PNI). Nerve growth factor (NGF) plays an important role in reconstructing peripheral nerve fibers and promoting axonal regeneration. However, it remains unclear if NGF effect in enhancing nerve regeneration is mediated through autophagic clearance of myelin debris in SCs.Methods: In vivo, free NGF solution plus with/without pharmacological inhibitors were administered to a rat sciatic nerve crush injury model. In vitro, the primary Schwann cells (SCs) and its cell line were cultured in normal medium containing NGF, their capable of swallowing or clearing degenerated myelin was evaluated through supplement of homogenized myelin fractions.Results: Administration of exogenous NGF could activate autophagy in dedifferentiated SCs, accelerate myelin debris clearance and phagocytosis, as well as promote axon and myelin regeneration at early stage of PNI. These NGF effects were effectively blocked by autophagy inhibitors. In addition, inhibition of the p75 kD neurotrophin receptor (p75NTR) signal or inactivation of the AMP-activated protein kinase (AMPK) also inhibited the NGF effect as well.Conclusions: NGF effect on promoting early nerve regeneration is closely associated with its accelerating autophagic clearance of myelin debris in SCs, which probably regulated by the p75NTR/AMPK/mTOR axis. Our studies thus provide strong support that NGF may serve as a powerful pharmacological therapy for peripheral nerve injuries.