Regeneration Of Injured Nerves Research Articles

Electroacupuncture alleviates motor dysfunction by regulating neuromuscular junction disruption and neuronal degeneration in SOD1G93A mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurological disease characterized by the progressive destruction of the neuromuscular junction (NMJ) and the degeneration of motor neurons, eventually leading to atrophy and paralysis of voluntary muscles responsible for motion and breathing. NMJs, synaptic connections between motor neurons and skeletal muscle fibers, are extremely fragile in ALS. To determine the effects of early electroacupuncture (EA) intervention on nerve reinnervation and regeneration following injury, a model of sciatic nerve injury (SNI) was first established using SOD1G93A mice, and early electroacupuncture (EA) intervention was conducted at Baihui (DU20), and bilateral Zusanli (ST36). The results revealed that EA increased the Sciatic nerve Functional Index, the structural integrity of the gastrocnemius muscles, and the cross-sectional area of muscle fibers, as well as up-regulated the expression of acetylcholinesterase and facilitated the co-location of α7 nicotinic acetate choline receptors and α-actinin. Overall, these results suggested that EA can promote the repair and regeneration of injured nerves and delay NMJ degeneration in SOD1G93A-SNI mice. Moreover, analysis of the cerebral cortex demonstrated that EA alleviated cortical motor neuron damage in SOD1G93A mice, potentially attributed to the inhibition of the cyclic GMP-AMP synthase-stimulator of interferon genes pathway and the release of interferon-β suppressing the activation of natural killer cells and the secretion of interferon-γ, thereby further inhibiting microglial activation and the expression of inflammatory factors. In summary, EA delayed the degeneration of NMJ and mitigated the loss of cortical motor neurons, thus delaying disease onset, accompanied by alleviation of muscle atrophy and improvements in motor function in SOD1G93A mice.

The Pulsed Nd:YAG Laser Therapy Enhanced Nerve Regeneration via Apoptosis Inhibition in a Rat Crushed Sciatic Nerve Model.

The study was aimed to validate the efficacy of the pulsed Nd:YAG laser on nerve regeneration in a rat sciatic nerve crushed model. 54 Wistar rats were randomly assigned into three groups: shame control, crush control, and laser treated group. For the laser treated group, the pulsed Nd:YAG laser (10Hz) with 350mJ per pulse in energy density and 50J/cm2 in fluence was applied extracorporeally at the lesion site for 12min to daily deliver 500J immediately and consecutive 9days following the crush injury. At week 1, the apoptosis-related activities in the injured nerve were examined (n = 8/each group). The sciatic functional index (SFI) was measured preoperatively and weekly until 4weeks after the index procedure. The injured nerve and the innervated gastrocnemius muscle histology were assessed at week 4 (n = 10/each group). At week 1, the laser group showed the significant less TUNEL-positive ratio (P < 0.05), and the lower expression of cleaved caspase3/procaspase-3 and beclin-2/beclin-2-associated protein X ratios compared with the crush control. Furthermore, the laser group revealed significantly better SFI since week 1 and throughout the study (P < 0.05, all) compared with the crush control. At week 4, the laser group showed significantly higher axon density, lower myelin g-ratio, and the corresponding higher glycogen expression (P < 0.05, all) in the gastrocnemius muscle compared with those in the crush control. The pulsed Nd:YAG might enhance the injured nerve regeneration via apoptosis inhibition.

Acupuncture on “Huantiao” (GB30) and "Yanglingquan" (GB34) acupoints promotes nerve regeneration in mice model of peripheral nerve injury

ObjectiveTo investigate the effects of acupuncture on promoting nerve regeneration in mice with sciatic nerve crushed injury, an animal model of peripheral nerve injury (PNI). MethodsAcupuncture was performed on the "Huantiao" (GB30) and "Yanglingquan" (GB34) acupoints in PNI mice model for 2 weeks. Gait analysis, toe spreading test, electrophysiological test, toluidine blue staining and immunostaining of myelin basic protein (MBP), neurofilament-200 (NF200), p75 neurotrophin receptor (p75NTR), and growth associated protein-43 (GAP43) were respectively performed to investigate the effects of acupuncture on crushed sciatic nerve. ResultsAcupuncture stimulation of “Huantiao” (GB30) and "Yanglingquan" (GB34) acupoints promoted the recovery of motor function and electrophysiological function in PNI mice model, which was indicated by a better gait level, toe spreading level and CMAP value in acupuncture group. The number of myelinated nerve fibers and the fluorescence intensity of MBP, NF200, p75NTR and GAP43 staining demonstrated that the acupuncture stimulation promoted the regeneration of injured nerves in PNI mice model. ConclusionAcupuncture significantly promoted the functional and morphological recovery of crushed sciatic nerve via promoting the expression of p75NTR in Schwann cells.

Axonal Regeneration: Underlying Molecular Mechanisms and Potential Therapeutic Targets.

Axons in the peripheral nervous system have the ability to repair themselves after damage, whereas axons in the central nervous system are unable to do so. A common and important characteristic of damage to the spinal cord, brain, and peripheral nerves is the disruption of axonal regrowth. Interestingly, intrinsic growth factors play a significant role in the axonal regeneration of injured nerves. Various factors such as proteomic profile, microtubule stability, ribosomal location, and signalling pathways mark a line between the central and peripheral axons' capacity for self-renewal. Unfortunately, glial scar development, myelin-associated inhibitor molecules, lack of neurotrophic factors, and inflammatory reactions are among the factors that restrict axonal regeneration. Molecular pathways such as cAMP, MAPK, JAK/STAT, ATF3/CREB, BMP/SMAD, AKT/mTORC1/p70S6K, PI3K/AKT, GSK-3β/CLASP, BDNF/Trk, Ras/ERK, integrin/FAK, RhoA/ROCK/LIMK, and POSTN/integrin are activated after nerve injury and are considered significant players in axonal regeneration. In addition to the aforementioned pathways, growth factors, microRNAs, and astrocytes are also commendable participants in regeneration. In this review, we discuss the detailed mechanism of each pathway along with key players that can be potentially valuable targets to help achieve quick axonal healing. We also identify the prospective targets that could help close knowledge gaps in the molecular pathways underlying regeneration and shed light on the creation of more powerful strategies to encourage axonal regeneration after nervous system injury.

Gabapentin inhibits the analgesic effects and nerve regeneration process induced by hepatocyte growth factor (HGF) in a peripheral nerve injury model: Implication for the use of VM202 and gabapentinoids for peripheral neuropathy

Hepatocyte growth factor (HGF) is a multifunctional protein that plays a critical role in the angiogenic, neurotrophic, antifibrotic, and antiapoptotic activities of various cell types. It has been previously reported that intramuscular injection of pCK-HGF-X7 (or VM202), a plasmid DNA designed to express both native isoforms of human HGF (Pyun et al., 2010), significantly reduced the level of neuropathic pain in clinical studies as well as in a variety of animal models. In clinical studies, it has been observed that pCK-HGF-X7 appeared to give much higher pain-relieving effects in subjects not taking pregabalin or gabapentin, α2δ1 calcium channel blockers frequently prescribed for reducing pain in patients with diabetic peripheral neuropathy. In this study, we tested the effects of gabapentin on HGF-mediated pain reduction and nerve regeneration in vivo. Consistent with the data from clinical studies, gabapentin administration inhibited the pain reduction and axon regeneration effects mediated by HGF expression from pCK-HGF-X7. In the context of nerve regenerative effects, treatment with gabapentin or EGTA, a Ca2+ chelator, inhibited HGF-mediated axon outgrowth of injured sciatic nerves in vivo. Taken together, i.m. injection of HGF-encoding plasmid DNA ameliorated pain symptoms and enhanced the regeneration of injured nerves, and these therapeutic effects of HGF were significantly hindered by gabapentin treatment, suggesting the possible involvement of Ca2+ in the pro-regenerative activities of native HGF derived from treatment with pCK-HGF-X7.

The impact of electroconductive multifunctional composite nanofibrous scaffold on adipose-derived mesenchymal stem cells

BackgroundThe development of tissue-engineered scaffolds with electrical properties is the primary motivation of novel regenerative medicine. Electroconductive scaffolds are designed to mimic the injured tissue environment's electrical properties and regulate cellular behavior - growth, proliferation, and differentiation - that could stimulate the injured nerve's regeneration. MethodsWe fabricated dedicated electroconductive scaffolds and customized an appropriate device with an external current supply to expose cells on the scaffold to electrical stimulation (ES). Next, we isolated rat adipose-derived stem cells (ASCs) and performed in vitro experiments that combine cells, an electroconductive scaffold, NGF (nerve growth factor), and ES (90 mV/mm, constant, for four days). Finally, we checked cellular activity as proliferation, viability, morphology, the neurogenic differentiation potential of ASCs, cell alignment, and karyotype. ResultsWe observed that the electrical stimulation did not change the viability and chromosome stability of rat ASCs, but altered slightly proliferation compared to non-stimulated cells. The combined effect of a scaffold, NGF, and ES caused morphology changes and enhancement of ASCs neuronal differentiation as indicated in βIII-tubulin expression, actin organization, and upregulation of neurogenic gene expression. ConclusionsWe developed an electroconductive scaffold and customized device for in vitro study with many experimental variants. Based on our results, we presumed that the established study scheme - including an electroconductive scaffold, NGF and ES - is biocompatible and could guide ASCs to differentiate in neurogenic lineage, thus may be potentially applied in nerve injury regeneration.

The immune microenvironment and tissue engineering strategies for spinal cord regeneration.

Regeneration of neural tissue is limited following spinal cord injury (SCI). Successful regeneration of injured nerves requires the intrinsic regenerative capability of the neurons and a suitable microenvironment. However, the local microenvironment is damaged, including insufficient intraneural vascularization, prolonged immune responses, overactive immune responses, dysregulated bioenergetic metabolism and terminated bioelectrical conduction. Among them, the immune microenvironment formed by immune cells and cytokines plays a dual role in inflammation and regeneration. Few studies have focused on the role of the immune microenvironment in spinal cord regeneration. Here, we summarize those findings involving various immune cells (neutrophils, monocytes, microglia and T lymphocytes) after SCI. The pathological changes that occur in the local microenvironment and the function of immune cells are described. We also summarize and discuss the current strategies for treating SCI with tissue-engineered biomaterials from the perspective of the immune microenvironment.

Low-Stiffness Hydrogels Promote Peripheral Nerve Regeneration Through the Rapid Release of Exosomes.

A hydrogel system loaded with mesenchymal stem cell–derived exosome (MSC-Exos) is an attractive new tool for tissue regeneration. However, the effect of the stiffness of exosome-loaded hydrogels on tissue regeneration is unclear. Here, the role of exosome-loaded hydrogel stiffness, during the regeneration of injured nerves, was assessed in vivo. The results showed that the photocrosslinkable hyaluronic acid methacrylate hydrogel stiffness plays an important role in repairing nerve injury. Compared with the stiff hydrogels loaded with exosomes, soft hydrogels loaded with exosomes showed better repair of injured peripheral nerves. The soft hydrogel promoted nerve repair by quickly releasing exosomes to inhibit the infiltration of macrophages and the expression of the proinflammatory factors IL-1β and TNF-α in injured nerves. Our work revealed that exosome-loaded hydrogel stiffness plays an important role in tissue regeneration by regulating exosome release behavior and provided important clues for the clinical application of biological scaffold materials.

Maresin 1 promotes nerve regeneration and alleviates neuropathic pain after nerve injury

BackgroundPeripheral nerve injury (PNI) is a public health concern that results in sensory and motor disorders as well as neuropathic pain and secondary lesions. Currently, effective treatments for PNI are still limited. For example, while nerve growth factor (NGF) is widely used in the treatment of PNI to promote nerve regeneration, it also induces pain. Maresin 1 (MaR1) is an anti-inflammatory and proresolving mediator that has the potential to regenerate tissue. We determined whether MaR1 is able to promote nerve regeneration as well as alleviating neuropathic pain, and to be considered as a putative therapeutic agent for treating PNI.MethodsPNI models were constructed with 8-week-old adult male ICR mice and treated with NGF, MaR1 or saline by local application, intrathecal injection or intraplantar injection. Behavioral analysis and muscle atrophy test were assessed after treatment. Immunofluorescence assay was performed to examine the expression of ATF-3, GFAP, IBA1, and NF200. The expression transcript levels of inflammatory factors IL1β, IL-6, and TNF-α were detected by quantitative real-time RT-PCR. AKT, ERK, mTOR, PI3K, phosphorylated AKT, phosphorylated ERK, phosphorylated mTOR, and phosphorylated PI3K levels were examined by western blot analysis. Whole-cell patch-clamp recordings were executed to detect transient receptor potential vanilloid 1 (TRPV1) currents.ResultsMaR1 demonstrated a more robust ability to promote sensory and motor function recovery in mice after sciatic nerve crush injury than NGF. Immunohistochemistry analyses showed that the administration of MaR1 to mice with nerve crush injury reduced the number of damaged DRG neurons, promoted injured nerve regeneration and inhibited gastrocnemius muscle atrophy. Western blot analysis of ND7/23 cells cultured with MaR1 or DRG neurons collected from MaR1 treated mice revealed that MaR1 regulated neurite outgrowth through the PI3K–AKT–mTOR signaling pathway. Moreover, MaR1 dose-dependently attenuated the mechanical allodynia and thermal hyperalgesia induced by nerve injury. Consistent with the analgesic effect, MaR1 inhibited capsaicin-elicited TRPV1 currents, repressed the nerve injury-induced activation of spinal microglia and astrocytes and reduced the production of proinflammatory cytokines in the spinal cord dorsal horn in PNI mice.ConclusionsApplication of MaR1 to PNI mice significantly promoted nerve regeneration and alleviated neuropathic pain, suggesting that MaR1 is a promising therapeutic agent for PNI.

Chitin conduits modified with DNA-peptide coating promote the peripheral nerve regeneration

Peripheral nerve injury (PNI) is one of the common clinical injuries which needs to be addressed. Previous studies demonstrated the effectiveness of using biodegradable chitin (CT) conduits small gap tubulization technology as a substitute for traditional epineurial neurorrhaphy. Aiming to improve the effectiveness of CT conduits in repairing PNI, we modified their surface with a DNA-peptide coating. The coating consisted of single strand DNA (ssDNA) and its complementary DNAʹ-peptide mimics. First, we immobilize ssDNA (DNA1 + 2) on CT conduits by carbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) method to construct CT/DNA conduits. EDC/NHS was used to activate carboxyl groups of modified ssDNA for direct reaction with primary amines on the CT via amide bond formation. Then, DNA1ʹ-BDNF + DNA2ʹ-VEGF mimic peptide (RGI + KLT) were bonded to CT/DNA conduits by complementary base pairing principle at room temperature to form CT/RGI + KLT conduits. When the surrounding environment rose to a certain point (37 °C), the CT/RGI + KLT conduits achieved sustainable release of DNA′-peptide. In vitro, the CT conduits modified with the DNA-peptide coating promoted the proliferation and secretion of Schwann cells by maintaining their repair state. It also promoted the proliferation of human umbilical vein vessel endothelial cells and axon outgrowth of dorsal root ganglion explants. In vivo, CT/RGI + KLT conduits promoted regeneration of injured nerves and functional recovery of target muscles, which was facilitated by the synergistic contribution of angiogenesis and neurogenesis. Our research brings DNA and DNA-peptide hybrids into the realm of tissue engineering to repair PNI.

Oriented nanofibrous P(MMD-co-LA)/Deferoxamine nerve scaffold facilitates peripheral nerve regeneration by regulating macrophage phenotype and revascularization

Delayed injured nerve regeneration remains a clinical problem, partly ascribing to the lack of regulation of regenerative microenvironment, topographical cues, and blood nourishment. Functional electrospun conduits have been established as an efficacious strategy to facilitate nerve regeneration by providing structural guidance, regulating the regenerative immune microenvironment, and improving vascular regeneration. However, the synthetic polymers conventionally used to fabricate electrospinning scaffolds, such as poly(L-lactic acid), poly(glycolic acid), and poly(lactic-co-glycolic acid), can cause aseptic inflammation due to acidic degradation products. Therefore, a poly[3(S)-methyl-morpholine-2,5-dione-co-lactic] [P(MMD-co-LA)] containing alanine units with good mechanical properties and reduced acid degradation products, was obtained by melt ring-opening polymerization (ROP). Here, we aimed to explore the effect of oriented nanofiber/Deferoxamine (DFO, a hydrophilic angiogenic drug) scaffold in the rapid construction of a favorable regenerative microenvironment, including cell bridge, polarized vascular system, and immune microenvironment. In vitro studies have shown that the scaffold can sustainably release DFO, which accelerates the migration and tube formation of human umbilical vein endothelial cells (HUVECs), as well as the expression of genes related to angiogenesis. The physical clues provided by the arranged nanofibers can regulate the polarization of macrophages and reduce the expression of inflammatory factors. Furthermore, the in vivo results demonstrated a higher M2 polarization level of the oriented nanofibrous scaffold treatment group with reducedinflammation reaction in the injured nerve. Moreover, the in-situ release of DFO up-regulated the expression of HIF1-α and SDF-1α genes, as well as the expression of HIF1-α′s target gene VEGF, further promoting revascularization and enhancing nerve regeneration at the defect site. The obtained results provide essential insights on accelerating the creation of the nerve regeneration microenvironment by combining the physiological processes of nerve regeneration with topographical cues and chemical signal induction.

In Situ Fabrication of Nerve Growth Factor Encapsulated Chitosan Nanoparticles in Oxidized Bacterial Nanocellulose for Rat Sciatic Nerve Regeneration.

Autograft is currently the gold standard in the clinical treatment of peripheral nerve injury (PNI), which, however, is limited by the availability of a donor nerve and secondary injuries. Nerve guidance conduits (NGC) provide a suitable microenvironment to promote the regeneration of injured nerves, which could be the substitutes for autografts. In this study, nerve growth factor (NGF) encapsulated chitosan nanoparticles (CSNPs) were first constructed in situ in an oxidized bacterial cellulose (OBC) conduit using the ion gel method after the introduction of a CS/NGF solution under pressure to enable a sustainable release of NGF. A novel NGF@CSNPs/OBC nanocomposite with antibacterial activity, biodegradability, and porous microstructure was successfully developed. In vitro experiments showed that the nanocomposite promoted the adhesion and proliferation of Schwann cells. When the nanocomposite was applied as NGC to repair the sciatic nerve defect of rats, a successful repair of the 10 mm nerve defect was observed after 4 weeks. At week 9, the diameter, morphology, histology, and functional recovery of the regenerated nerve was comparable to the autografts, indicating that the NGC effectively promoted the regeneration and function recovery of the nerve. In summary, the NGF@CSNPs/OBC as a novel NGC provides great potential in the treatment of PNI.

Co-transplantation of Schwann cells and neural stem cells in the laminin-chitosan-PLGA nerve conduit to repair the injured recurrent laryngeal nerve in SD rats.

The objective of this paper is to investigate the possibility and efficacy of recurrent laryngeal nerve repair by transplantation of co-cultured Schwann cells and neural stem cells (NSCs) in laminin-chitosan-poly-lactic-co-glycolic acid (laminin-chitosan-PLGA) nerve conduits in rats. A laminin-chitosan-PLGA conduit was used in a rat recurrent laryngeal nerve transection model. The rat recurrent laryngeal nerve was dissected to generate a 5 mm defect. Then, a laminin-chitosan-PLGA nerve conduit with or without Schwann cells and NSCs in the lumen was transplanted into the defect. A total of 96 female rats were randomised into six groups: co-culture of NSCs and Schwann cells in the nerve conduit group (CO), Schwann cells only in the nerve conduit group (SC), neural stem cells only in the nerve conduit group (NSC-only), nerve conduit group (null), autologous nerve graft group (autograft) and sham operation group (sham). Regenerated nerves were evaluated by histological and functional assessment at 8 and 12 weeks after surgery. The diameter and area of the regenerated myelin sheath, as well as the secretion of brain-derived neurotrophic factor and glial cell-derived neurotrophic factor in laryngeal muscle or regenerated nerve tissue in the CO group, were significantly better than they were in the SC, NSC-only and null groups (all P values < 0.05). Immunofluorescence showed that the CO group had significantly more neurofilament-200 immunoreactive and S-100 immunoreactive fibres than the SC, NSC-only and null groups (all P values < 0.05). The performance of the CO groups and autograft groups was found to be similar by laryngoscopy. Arytenoid cartilage motion recovery in these two groups was significantly better than it was in the other groups (all P values < 0.05). Our results indicated that co-culture of Schwann cells and NSCs in laminin-chitosan-PLGA conduits might promote injured nerve regeneration. This method might be a promising alternative for defective nerve repair.

Micro-grooved nerve guidance conduits combined with microfiber for rat sciatic nerve regeneration

In order to accelerate the regeneration of injured nerves, highly aligned structures that mimic native tissues are essential for nerve guidance conduits (NGC). In this study, a biodegradable porous micro-patterned NGCs were manufactured by use of capillary force lithography and salt leaching method, which filled as wrapped with aligned electrospun microfiber (PA-NGC) using. These combined NGC showed 5μm aligned groove pattern on the interior wall and were filled with 4–5μm align fibers for a fascicular structure to mimic the native nerve. The highly aligned structure has increased PC12 migration and morphological elongation compared with random microfiber. For the in vivo study, we bridged in the 10mm sciatic nerve defect margins with NGC. The PA-NGC were compared to flat NGCs filled with random (FR-NGC) or aligned fiber (FA-NGC) and patterned NGCs filled with random fiber (PR-NGC). The PA-NGC showed as dramatically re-bridged neurofilament and higher sciatic function index, onset-to-peak of amplitude, muscle weight and fiber diameter compared to other groups after 8 weeks of implantation. In our results, the PA-NGC not only can serve as a design for functional NGC without growth factor but also can be used in clinical application for peripheral nerve regeneration.

Ultrasound Stimulation Increases Neurite Regeneration in Injured Dorsal Root Ganglion Neurons through Mammalian Target of Rapamycin Activation.

Ultrasound stimulation (US) is reported to be a safe and useful technology for improving injured nerve regeneration. However, the intracellular mechanisms underlying its stimulatory effects are only partially understood. Mammalian target of rapamycin (mTOR) signaling is involved in neuronal survival and axonal outgrowth. In this study, we investigated the effect of US on regeneration of injured dorsal root ganglion (DRG) neurons and activation of the mTOR pathway. We showed that US significantly increased neurite regeneration and enhanced mTOR activation. Moreover, the expression of growth-associated protein-43 (GAP-43), a crucial factor for axonal outgrowth and regeneration in neurons, was significantly increased by US. These data suggest that US-induced neurite regeneration is mediated by upregulation of mTOR activity, which promotes the regeneration of injured DRG neurons.

Down-regulation of long non-coding RNA MEG3 promotes Schwann cell proliferation and migration and repairs sciatic nerve injury in rats.

Peripheral nerve injury and regeneration are complex processes and involve multiple molecular and signalling components. However, the involvement of long non‐coding RNA (lncRNA) in this process is not fully clarified. In this study, we evaluated the expression of the lncRNA maternally expressed gene 3 (MEG3) in rats after sciatic nerve transection and explored its potential mechanisms. The expression of lncRNA MEG3 was up‐regulated following sciatic nerve injury and observed in Schwann cells (SCs). The down‐regulation of lncRNA MEG3 in SCs enhanced the proliferation and migration of SCs via the PTEN/PI3K/AKT pathway. The silencing of lncRNA MEG3 promoted the migration of SCs and axon outgrowth in rats after sciatic nerve transection and facilitated rat nerve regeneration and functional recovery. Our findings indicated that lncRNA MEG3 may be involved in nerve injury and injured nerve regeneration in rats with sciatic nerve defects by regulating the proliferation and migration of SCs. This gene may provide a potential therapeutic target for improving peripheral nerve injury.

Interference with SRF expression in skeletal muscles reduces peripheral nerve regeneration in mice

Traumatic injury of peripheral nerves typically also damages nerve surrounding tissue including muscles. Hence, molecular and cellular interactions of neighboring damaged tissues might be decisive for successful axonal regeneration of injured nerves. So far, the contribution of muscles and muscle-derived molecules to peripheral nerve regeneration has only poorly been studied. Herein, we conditionally ablated SRF (serum response factor), an important myofiber transcription factor, in skeletal muscles of mice. Subsequently, the impact of this myofiber-restricted SRF deletion on peripheral nerve regeneration, i.e. facial nerve injury was analyzed. Quantification of facial nerve regeneration by retrograde tracer transport, inspection of neuromuscular junctions (NMJs) and recovery of whisker movement revealed reduced axonal regeneration upon muscle specific Srf deletion. In contrast, responses in brainstem facial motor neuron cell bodies such as regeneration-associated gene (RAG) induction of Atf3, synaptic stripping and neuroinflammation were not overly affected by SRF deficiency. Mechanistically, SRF in myofibers appears to stimulate nerve regeneration through regulation of muscular satellite cell (SC) proliferation. In summary, our data suggest a role of muscle cells and SRF expression within muscles for regeneration of injured peripheral nerves.

Targeting chondroitinase ABC to axons enhances the ability of chondroitinase to promote neurite outgrowth and sprouting.

BackgroundThere is currently no effective treatment for promoting regeneration of injured nerves in patients who have sustained injury to the central nervous system such as spinal cord injury. Chondroitinase ABC is an enzyme, which promotes neurite outgrowth and regeneration. It has shown considerable promise as a therapy for these conditions. The aim of the study is to determine if targeting chondroitinase ABC expression to the neuronal axon can further enhance its ability to promote axon outgrowth. Long-distance axon regeneration has not yet been achieved, and would be a significant step in attaining functional recovery following spinal cord injury.Methodology/Principal findingsTo investigate this, neuronal cultures were transfected with constructs encoding axon-targeted chondroitinase, non-targeted chondroitinase or GFP, and the effects on neuron outgrowth and sprouting determined on substrates either permissive or inhibitory to neuron regeneration. The mechanisms underlying the observed effects were also explored. Targeting chondroitinase to the neuronal axon markedly enhances its ability to promote neurite outgrowth. The increase in neurite length is associated with an upregulation of β-integrin staining at the axonal cell surface. Staining for phosphofocal adhesion kinase, is also increased, indicating that the β-integrins are in an activated state. Expression of chondroitinase within the neurons also resulted in a decrease in expression of PTEN and RhoA, molecules which present a block to neurite outgrowth, thus identifying two of the pathways by which ChABC promotes neurite outgrowth.Conclusions / SignificanceThe novel finding that targeting ChABC to the axon significantly enhances its ability to promote neurite extension, suggests that this may be an effective way of promoting long-distance axon regeneration following spinal cord injury. It could also potentially improve its efficacy in the treatment of other pathologies, where it has been shown to promote recovery, such as myocardial infarction, stroke and Parkinson’s disease.

Surface-Anchored Graphene Oxide Nanosheets on Cell-Scale Micropatterned Poly(d,l-lactide-co-caprolactone) Conduits Promote Peripheral Nerve Regeneration.

Regeneration and functional recovery of peripheral nerves remain formidable due to the inefficient physical and chemical cues in the available nerve guidance conduits (NGCs). Introducing micropatterns and bioactive substances into the inner wall of NGCs can effectively regulate the behavior of Schwann cells, the elongation of axons, and the phenotype of macrophages, thereby aiding the regeneration of injured nerve. In this study, linear micropatterns with ridges and grooves of 3/3, 5/5, 10/10, and 30/30 μm were created on poly(d,l-lactide-co-caprolactone) (PLCL) films following with surface aminolysis and electrostatic adsorption of graphene oxide (GO) nanosheets. The GO-modified micropatterns could significantly accelerate the collective migration of Schwann cells (SCs) and migration of SCs from their spheroids in vitro. Moreover, the SCs migrated directionally along the stripes with a fastest rate on the 3/3-GO film that had the largest cell adhesion force. The neurites of N2a cells were oriented along the micropatterns, and the macrophages tended to differentiate into the M2 type on the 3/3-GO film judged by the higher expression of Arg 1 and IL-10. The systematic histological and functional assessments of the regenerated nerves at 4 and 8 weeks post-surgery in vivo confirmed that the 3/3-GO NGCs had better performance to promote the nerve regeneration, and the CMAP, NCV, wet weight of gastrocnemius muscle, positive S100β and NF200 area percentages, and average myelinated axon diameter were more close to those of the autograft group at 8 weeks. This type of NGCs thus has a great potential for nerve regeneration.

Intraluminal Guiding Structure of Nerve Conduits for Peripheral Nerve Regeneration

Peripheral nerve injury that can lead to disability affects millions of people worldwide annually. As the gold standard treatment of peripheral nerve injury, autologous nerve grafts are the most widely used and effective, but the clinical application of the treatment is greatly limited by many disadvantages. Tissue engineering nerve conduits gradually become promising autologous nerve grafts alternatives to promote the regeneration of injured nerves. This review places emphasis on tissue engineering designs of physical and topographic guiding structure inside nerve conduits in order to promote the migration of Schwann cells and directional regrowth of axons towards target organs. Various strategies of intraluminal guiding cues have been described and analyzed, including the incorporation with the tissue with natural basement membrane, collagen, microfilaments, intraluminal multi-channel and grooves in the inner wall. Recently, much progress has been made in the development of tissue engineering nerve conduits, but poor curative effect and deficiencies such as axon dispersion and malposition healing still remain unsolved, many crucial factors need to be considered in further research before clinical practices.