Spatiotemporal dynamics of exercise-induced macrophages influences axonal regeneration after peripheral nerve injury.

Peripheral nerve injuries commonly occur due to trauma, like a traffic accident. Peripheral nerves get severed, causing motor neuron death and potential muscle atrophy. The current golden standard to treat peripheral nerve lesions, especially lesions with large (≥ 3 cm) nerve gaps, is the use of a nerve autograft or reimplantation in cases where nerve root avulsions occur. If not tended early, degeneration of motor neurons and loss of axon regeneration can occur, leading to loss of function. Although surgical procedures exist, patients often do not fully recover, and quality of life deteriorates. Peripheral nerves have limited regeneration, and it is usually mediated by Schwann cells and neurotrophic factors, like glial cell line-derived neurotrophic factor, as seen in Wallerian degeneration. Glial cell line-derived neurotrophic factor is a neurotrophic factor known to promote motor neuron survival and neurite outgrowth. Glial cell line-derived neurotrophic factor is upregulated in different forms of nerve injuries like axotomy, sciatic nerve crush, and compression, thus creating great interest to explore this protein as a potential treatment for peripheral nerve injuries. Exogenous glial cell line-derived neurotrophic factor has shown positive effects in regeneration and functional recovery when applied in experimental models of peripheral nerve injuries. In this review, we discuss the mechanism of repair provided by Schwann cells and upregulation of glial cell line-derived neurotrophic factor, the latest findings on the effects of glial cell line-derived neurotrophic factor in different types of peripheral nerve injuries, delivery systems, and complementary treatments (electrical muscle stimulation and exercise). Understanding and overcoming the challenges of proper timing and glial cell line-derived neurotrophic factor delivery is paramount to creating novel treatments to tend to peripheral nerve injuries to improve patients’ quality of life.

MicroRNA-135a-5p Promotes the Functional Recovery of Spinal Cord Injury by Targeting SP1 and ROCK

Peripheral nerve injury (PNI) is a common condition that leads to the partial loss of function in the sensory, motor, and autonomic nervous systems. The peripheral nervous system has an inherent capacity to regenerate after injury and re-innervate its target organs, but full functional recovery is rare. In recent years, there has been growing interest in identifying drugs that can promote axonal regeneration and outgrowth following PNI. Epothilone B (EpoB) is an FDA-approved antineoplastic agent that promotes tubulin polymerization and enhances the stability of microtubules. Recently, the regenerative effects of EpoB in the central nervous system have garnered attention, but its potential therapeutic effects on peripheral nerve regeneration remain underexplored. This study utilized a sciatic nerve transection and anastomosis model in rats to evaluate the effects of EpoB on neuroprotein expression following nerve injury. Behavioral analysis, Masson’s trichrome staining, and immunofluorescence staining were conducted to assess the impact of EpoB on sciatic nerve regeneration. Over time, motor recovery and muscle reinnervation were observed, with Sciatic Functional Index (SFI) scores higher in the EpoB-treated group compared to the vehicle group. The expression of fibronectin (FN) was significantly lower in the EpoB group, while the expression of Tau, neurofilament-M (NF-M), and growth-associated protein-43 (GAP-43) was significantly higher. In conclusion, EpoB treatment significantly increases the expression of Tau, NF-M, and GAP-43, suggesting a positive effect on axonal regeneration and repair.

Background and aims Peripheral nerve injuries (PNIs) cause motor and sensory dysfunction. This study assessed cardamonin’s effectiveness in enhancing sciatic nerve regeneration and functional recovery in a rat model of nerve crush injury. Methods Male rats underwent unilateral sciatic nerve crush and received graded doses of cardamonin (5, 10, 20 mg/kg). The study also included a Sham surgery and a Crush control group. Motor function was assessed with the Sciatic Functional Index (SFI) and sensory function using the Hargreaves test. Electrophysiological measurements, including compound muscle action potential (CMAP) amplitude and nerve conduction velocity (NCV), were recorded at 8 weeks. Histomorphometric analyses of nerve and gastrocnemius muscle were performed, along with quantification of pro- and anti-inflammatory cytokines, neurotrophic factors, and apoptosis markers 7 days post-injury. Results Cardamonin treatment significantly improved motor (SFI) and sensory recovery in a dose-dependent manner compared to crush controls (p < 0.001). CMAP and NCV also improved significantly with cardamonin treatment (p < 0.001). Histological evaluation revealed partial restoration of myelin thickness, axon and fiber diameter, and an increase in fiber number (p < 0.01). Cardamonin reduced muscle atrophy and collagen deposition (p < 0.001). Pro-inflammatory cytokines IL-1β, IL-6, and TNF-α were significantly attenuated, while anti-inflammatory cytokines IL-10 and TGF-β, and neurotrophic factors NGF, BDNF, and NT-3 were upregulated dose-dependently (p < 0.05). Caspase-3, -8, and -9 activities were markedly reduced (p < 0.05). Conclusion Cardamonin promotes peripheral nerve regeneration and functional recovery after sciatic nerve crush injury through anti-inflammatory, neurotrophic, and anti-apoptotic effects.

Introduction. Peripheral nerve injury (PNI) is a common wartime pathology, the presence of which significantly complicates the course and treatment of combat injuries to the limbs. The development of new methods of treatment of PNI is impossible without validating existing models of PNI and clarifying the dynamics of the recovery process in this type of injury over long periods of observation. In this paper, the dynamics of the sciatic functional index (SFI) after transection and immediate suturing of the sciatic nerve of an adult rat during 24 weeks of observation was analyzed in detail. Objective: to analyze the dynamics of SFI after transection, as well as after transection and immediate suturing of the sciatic nerve of an adult rat for 24 weeks and compare the obtained results with the data of other authors under similar experimental conditions. Materials and Methods. The study was performed on 76 white adult outbred male rats, adhering to bioethical norms. In animals of the Sham group (n=24) an access to the sciatic nerve was performed, in animals of the Sect group (n=29) — the sciatic nerve was transected, and Raph group (n=23) — transection and immediate epineural suturing of the sciatic nerve was performed. A certain number of animals were removed from each group 4, 8, and 12 weeks after surgery for electrophysiological and morphological studies, and for the rest of the animals, the experiment was completed 24 weeks after the start of observation. SFI was determined before animals were removed, for all animals in each group at 4, 8, 12, 16, 20 and 24 weeks according to the Bain-Mackinnon-Hunter formula. Processing of digital data was carried out by various means of mathematical statistics. Results. In animals of the Sham group, which were observed throughout the entire 24 weeks of the experiment (n=7), the average value of SFI one month after the injury simulation was -8.9 points and did not change significantly until the end of the experiment. In animals of the Sect group, which were observed throughout the entire 24 weeks of the experiment (n=8), one month after the injury, the mean SFI value was –84.7 points, significantly increasing to –67.0 points at the end of the 16th week, and subsequently significantly decreasing to –96.5 points. In animals of the Raph group, which were observed throughout the entire 24 weeks of the experiment (n=7), the average value of SFI after one month was -64.4 points, and its increase to -45.4 points at the end of week 24 should be considered relatively reliable. Pairwise comparison of the averaged for all animals SFI values in the Sham and Sect, Sham and Raph, and Sect and Raph groups revealed significant differences at 4, 8, 12, 20, and 24 weeks after simulated injury. At 16 weeks post-intervention, the SFI values in the Sect and Raph groups were significantly different from those in the Sham group, but were not different from each other. Conclusions. The method of determining the function of the paretic limb after sciatic nerve injury in rats using SFI has a number of technical limitations, which are the reason for significant variability in experimental results among different research groups. The reliable biphasic SFI dynamics that was discovered after sciatic nerve transection, as well as the insignificant (according to this data) fluctuations in SFI after sciatic nerve transection and neurorrhaphy, require independent verification, pathophysiological interpretation, and should be taken into account when evaluating rehabilitation methods using such an experimental model of peripheral nerve injury.

The purpose of this study was to determine whether the timing of tread-mill exercise application can control expression levels of neuropathic pain- and regeneration-related proteins in the ipsilateral lumbar 4 (L4) to 6 (L6) dorsal root ganglion cells (DRG) after sciatic nerve injury (SNI). The experimental rats were randomly divided into five groups: the normal control, SNI+sedentary (IS), exercise+SNI (EI), SNI+exercise (IE), exercise+SNI+exercise (EIE) groups. The rats in exercise groups per-formed treadmill exercise at a speed of 8 m/min for 30 min once a day during 14 days before and/or after SNI. For investigating the expression of specific neuropathic pain and regeneration-related proteins in DRG, we prepared L4 to L6 DRG in the ipsilateral side. In the quantitative analysis, growth associated protein 43 (GAP-43) and brain-derived neurotrophic factor levels were further increased in the ipsilateral DRG at all treadmill exercise groups than those in IS group. In the histological findings, GAP-43 was qualitatively increased IE and EIE groups than IS group at DRG. Wnt3a and β-catenin were dramatically downregulated in EIE and IE groups than IS groups. In addition, nuclear factor kappa-light-chain-enhancer of activated B cells and tumor necrosis factor-α were significantly decreased in IE and EIE groups than IS group in the ipsilateral DRG. Our findings suggested novel information that regular low-intensity exercise before and/or after SNI might be a therapeutic and preventive approaches for relieving neuropathic pain and improving axonal elongation after peripheral nerve injury.

Objective:Although regimens of stem cell implantation can elicit functional recovery following peripheral nerve injury, the degree of outcome is still limited. This study evaluated the synergistic effects of cold-water swimming (CWS) and mesenchymal stem cell (MSC) transplantation on functional recovery of crushed sciatic nerve in rats.Method:Forty Sprague-Dawley rats that had their sciatic nerve crushed during surgery were randomly divided into four groups: MSCCWS group, treated with combination of MSC and CWS; MSC group, treated with MSC alone; CWS group, treated with CWS alone; and non-treated group, without any treatments. The sciatic function index (SFI), vertical activity (VA), ankle activity (AA) and electrophysiological study were examined before, immediately after surgery, after the treatment and after 4 weeks from treatment. Morphological and S100 immunohistochemical studies were also performed.Results:The MSCCWS group showed a greater improvement in SFI, VA, AA, peak amplitudes and onset latencies of compound muscle action potential (CMAP) in sciatic nerve and infiltration of immune cells with significant difference from the MSC, CWS and non-treated groups (P < 0.05).Conclusions:MSC transplantation combined with CWS could achieve better results in functional recovery than a single treatment of MSC alone or CWS alone in nerve crush injury.

Nerve injury of the central nervous system and the peripheral nervous system still poses a major challenge in modern clinics. Understanding the roles of neurotrophic factors and their molecular mechanisms on neuro-regeneration will not only benefit patients with neural damage but could potentially treat neurodegenerative disorders, such as amyotrophic lateral sclerosis. In this study, we showed that human IL12 p40-p40 homodimer (hIL12p80) within PLA and PLGA conduits improved sciatic nerve regeneration in mice. As such, the group of conduits with NSCs and hIL12p80 (CNI) showed the best recovery among the groups in the sciatic functional index (SFI), compound muscle action potential (CMAP), and Rotarod performance analyses. In addition, the CNI group had a faster recovery and outperformed the other groups in SFI and Rotarod performance tests beginning in the fourth week post-surgery. Immunohistochemistry showed that the CNI group increased the diameter of the newly regenerated nerve by two-fold (p < 0.01). In vitro studies showed that hIL12p80 stimulated differentiation of mouse NSCs to oligodendrocyte lineages through phosphorylation of Stat3 at Y705 and S727. Furthermore, implantation using PLGA conduits (C2.0 and C2.1) showed better recovery in the Rotarod test and CMAP than using PLA conduits in FVB mice. In B6 mice, the group with C2.1 + NSCs + hIL12p80 (C2.1NI) not only promoted sciatic functional recovery but also reduced the rate of experimental autotomy. These results suggested that hIL12p80, combined with NSCs, enhanced the functional recovery and accelerated the regeneration of damaged nerves in the sciatic nerve injury mice. Our findings could further shed light on IL12′s application not only in damaged nerves but also in rectifying the oligodendrocytes’ defects in neurodegenerative diseases, such as amyotrophic lateral sclerosis and multiple sclerosis.

Down-regulation miR-146a-5p in Schwann cell-derived exosomes induced macrophage M1 polarization by impairing the inhibition on TRAF6/NF-κB pathway after peripheral nerve injury

Axon regeneration is substantially regulated by gene expression and cytoskeleton remodeling. Here we show that the tumor suppressor protein p53 is required for neurite outgrowth in cultured cells including primary neurons as well as for axonal regeneration in mice. These effects are mediated by two newly identified p53 transcriptional targets, the actin-binding protein Coronin 1b and the GTPase Rab13, both of which associate with the cytoskeleton and regulate neurite outgrowth. We also demonstrate that acetylation of lysine 320 (K320) of p53 is specifically involved in the promotion of neurite outgrowth and in the regulation of the expression of Coronin 1b and Rab13. Thus, in addition to its recognized role in neuronal apoptosis, surprisingly, p53 is required for neurite outgrowth and axonal regeneration, likely through a different post-translational pathway. These observations may suggest a novel therapeutic target for promoting regenerative responses following peripheral or central nervous system injuries.

Schwann cells are integral to the regenerative capacity of the peripheral nervous system, which declines after adolescence. The mechanisms underlying this decline are poorly understood. This study sought to compare the protein expression of Notch, c-Jun, and Krox-20 after nerve crush injury in adolescent and young adult rats. We hypothesized that these Schwann cell myelinating regulatory factors are down-regulated after nerve injury in an age-dependent fashion. Adolescent (2 months old) and young adult (12 months old) rats (n = 48) underwent sciatic nerve crush injury. Protein expression of Notch, c-Jun, and Krox-20 was quantified by Western blot analysis at 1, 3, and 7 days post-injury. Functional recovery was assessed in a separate group of animals (n = 8) by gait analysis (sciatic functional index) and electromyography (compound motor action potential) over an 8-week post-injury period. Young adult rats demonstrated a trend of delayed onset of the dedifferentiating regulatory factors, Notch and c-Jun, corresponding to the delayed functional recovery observed in young adult rats compared to adolescent rats. Compound motor action potential area was significantly greater in adolescent rats relative to young adult rats, while amplitude and velocity trended toward statistical significance. The process of Schwann cell dedifferentiation following peripheral nerve injury shows different trends with age. These trends of delayed onset of key regulatory factors responsible for Schwann cell myelination may be one of many possible factors mediating the significant differences in functional recovery between adolescent and young adult rats following peripheral nerve injury.

BackgroundPeripheral nerve injury (PNI) is a common and progressive disorder with sensory and motor deficits in the peripheral nervous system (PNS). Treatment is difficult, with unfavorable prognosis. Green tea polyphenols (GTPs) exert neuroprotective effects on regeneration of the central nervous system (CNS). However, the effects of GTPs on functional recovery of the PNS have not been fully characterized. Consequently, the present study investigated the effects of GTPs on nerve regeneration of rats with PNI.Material/MethodsThe model of PNI was established in rats by sciatic nerve injury (SNI). Adult male Wistar rats with SNI were randomly divided into a vehicle group and a GTPs group. The compound muscle action potential (CMAP) of rat sciatic nerves (SN) was measured using the CM6240 physiological signal acquisition and processing system. The wet weight of the triceps muscle was determined using an analytical balance. The number of myelinated nerve fibers was counted under an optical microscope. Ultrastructure of the regenerated nerves in SN was observed by transmission electron microscopy. The mRNA and protein expression of nerve growth factor (NGF), growth-associated protein-43 (GAP-43), neurofilament 200 (NF200), and myelin-associated glycoprotein (MAG) in SN stumps were measured by real-time quantification PCR (RT-qPCR) and Western blot, respectively.ResultsIn rats with SNI, GTPs relieved the adhesion between nerve anastomosis and surrounding tissues, and significantly increased nerve conduction velocity, wet weight of the triceps muscle, and development and axonal regeneration of myelinated nerve fibers. Moreover, GTPs promoted the mRNA and protein expressions of NGF, GAP-43, NF200, and MAG in SN stumps.ConclusionsGTPs promotes nerve regeneration in rats with SNI.

Physical activity can improve sensorimotor recovery after peripheral nerve injury. We examined the effects of treadmill training (TMT) on axonal regeneration in the injured sciatic nerve of the rat and further investigated cellular and molecular events that underlie enhanced axonal regrowth by training. After crush injury of the sciatic nerves, rats were randomly assigned into either TMT or sedentary groups. Three to 14 d after injury, changes in protein levels in the regenerating nerve were analyzed by Western blotting and immunofluorescence staining. Axonal regeneration was assessed by anterograde and retrograde tracing techniques. The animals' functional recovery was determined by the sciatic functional index. We identified enhanced axonal regrowth in the distal stump of the sciatic nerve 7-14 d after injury in the rats with TMT. Cell division cycle 2 (Cdc2) mRNA and protein levels were highly increased in the injured sciatic nerves 3 and 7 d after injury, and decreased to basal levels 14 d later. Daily TMT accelerated distal shift of Cdc2 mRNA and protein induced in the regenerating nerves, and Cdc2 kinase activity was similarly increased in the distal stump by TMT. Cdc2 protein induced by TMT was mainly colocalized with Schwann cell marker S100beta protein, and correlated with axial distribution pattern of bromodeoxyuridine-labeled proliferating cell population in the regenerating nerve. We further demonstrate that axonal regeneration and motor function recovery after injury, both of which were promoted by TMT, were greatly suppressed by in vivo administration of Cdc2 inhibitor roscovitine. The present data suggest that Cdc2 kinase activated in the regenerating sciatic nerve may play an important role in TMT-mediated enhancement of axonal regeneration.

Objective: A study was planned to investigate the effect of exposure to cigarette smoke and the effects of calcium channel blockers in experimentally induced sciatic nerve injuries. Material-Method: The sciatic nerve was cut on one side in all the groups, and repair was performed in hour 0. After repair, a single daily dose of 1 ml of 0.9% saline was administered to group 1, 90 days, 30 minutes, cigarette smoke to group 2, 1mg/kg calcium channel blocker to group 3, 90 days, 30 minutes, cigarette smoke and 1mg/kg Calcium channel blocker was given to group 4. Results: At the end of the 12th week, gait analysis at and sciatic function index (SFI), the number of myelinated axons, axon areas and myelin diameters were assessed. There was a significant difference between the measured values of SFI in group 1 and group 3 and 4, and there was a significant difference between group 2 and group 3 and 4 (p &amp;lt;0.05). In addition there was a significant difference between the number of axons in group 2 and group 3 (p &amp;lt;0.05). Conclusion: As a result, after peripheral nerve laceration repair calcium channel blockers have a positive effect on the sciatic function index while cigarette smoke has a negative effect. In addition, according to the sciatic function index the negative effect of cigarette smoke can be resolved with calcium channel blockers. But; these data are not supported by the number of axon, axon area, and the myelin diameter

Purpose: The research investigated the neuroprotective properties of Cerebrolysin regarding functional recovery, axonal regeneration, and macrophage polarization in a rat model of acute sciatic nerve damage. Methods: The research included 72 male Wistar rats, categorized into six groups: sham control, crush injury, vehicle-treated crush damage, and two groups receiving Cerebrolysin treatment for crush injury. The assessment of functional recovery was conducted with the sciatic functional index and hot plate test, while axonal regeneration, muscle atrophy, and macrophage polarization were also studied.Results: Results demonstrated that Cerebrolysin, particularly at 5 mg/kg, significantly improved SFI scores and thermal paw withdrawal latency compared to the control group, indicating enhanced functional recovery. Histomorphometric analysis revealed increased myelinated axon counts in the Cerebrolysin-treated groups. Cerebrolysin also reduced gastrocnemius muscle atrophy and induced a change in macrophage polarization from pro-inflammatory M1 to pro-healing M2.Conclusion: These results imply that cerebrolysin improves functional outcomes, promotes axonal regeneration, and modifies macrophage polarization to provide neuroprotective effects in peripheral nerve damage. The 5 mg/kg dosage proved to be more effective than the 2.5 mg/kg dose. This study highlights the potential of Cerebrolysin as a therapeutic agent for peripheral nerve injuries.