Vascular endothelial growth factor activates neural stem cells through epidermal growth factor receptor signal after spinal cord injury

AAV-mediated VEGFA overexpression promotes angiogenesis and recovery of locomotor function following spinal cord injury via PI3K/Akt signaling

Spinal cord injury (SCI) is a disorder of the central nervous system resulting from various factors such as trauma, inflammation, tumors, and other etiologies. This condition leads to impairment in motor, sensory, and autonomic functions below the level of injury. Limitations of current therapeutic approaches prompt an investigation into therapeutic angiogenesis through persistent local expression of proangiogenic factors. Here, we investigated whether overexpression of adeno-associated virus (AAV)-mediated vascular endothelial growth factor A (VEGFA) in mouse SCI promoted locomotor function recovery, and whether the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway was mechanistically involved. Three weeks before SCI, AAV-VEGFA was injected at the T10 level to induce VEGFA overexpression. Neurofunctional, histological, and biochemical assessments were done to determine tissue damage and/or recovery of neuromuscular and behavioral impairments. Daily injections of the PI3K/Akt pathway inhibitor LY294002 were made to assess a possible mechanism. AAV-VEGFA overexpression dramatically improved locomotor function and ameliorated pathological injury caused by SCI. Improved motor-evoked potentials in hindlimbs and more spinal CD31-positive microvessels were observed in AAV-VEGFA-overexpressing mice. LY294002 reduced PI3K and Akt phosphorylation levels and attenuated AAV-VEGFA-related improvements. In conclusion, sustained local AAV-mediated VEGFA overexpression in spinal cord can significantly promote angiogenesis and ameliorate locomotor impairment after SCI in a contusion mouse model through activation of the PI3K/Akt signaling pathway.

[Experimental study of tetramethylpyrazine-loaded electroconductive hydrogel on angiogenesis and neuroprotection after spinal cord injury]

Objective

To explore the mechanisms for repairing spinal cord injury (SCI) with tetramethylpyrazine-loaded electroconductive hydrogel (hereinafter referred to as "TGTP").

Mehtods

A total of 72 female Sprague-Dawley rats were randomly divided into 4 groups: sham operation group (group A), SCI group (group B), SCI+electroconductive hydrogel group (group C), and SCI+TGTP group (group D). Only the vertebral plate was removed in group A, while the remaining groups were subjected to a whole transection model of spinal cord with a 2 mm gap in the lesions. The recovery of hindlimb motor function was evaluated by Basso, Beattie, Bresnahan (BBB) score and modified Rivlin-Tator inclined plate test before operation and at 1, 3, 7, 14, and 28 days after operation, respectively. Animals were sacrificed at 7 days and 28 days after modeling. Neovascularisation was observed by immunofluorescence staining of CD31 and the expression levels of angiopoietin 1 (Ang-1) and Tie-2 were assessed by Western blot assay. At 28 days postoperatively, the expression levels of pro-angiogenic related proteins, including platelet-derived growth factor B (PDGF-B), PDGF receptor β (PDGFR-β), vascular endothelial growth factor A (VEGF-A), and VEGF receptor 2 (VEGFR-2), were also assessed by Western blot. The fibrous scar in the injured area was assessed using Masson staining, while neuronal survival was observed through Nissl staining. Furthermore, LFB staining was utilized to detect myelin distribution and regeneration. Immunofluorescence and Western blot assay were employed to evaluate the expression of neurofilament 200 (NF200).

Results

The hindlimb motor function of rats in each group gradually recovered from the 3rd day after operation. The BBB score and climbing angle in group D were significantly higher than those in group B from 3 to 28 days after operation, and significantly higher than those in group C at 14 days and 28 days after operation ( P<0.05). Masson staining showed that the collagen volume fraction in groups B-D were significantly higher than that in group A, and that in group D was significantly lower than that in groups B and C ( P<0.05); a small amount of black conductive particles were scattered at the broken end in group D, and the surrounding collagen fibers were less than those in group C. Nissl and LFB staining showed that the structure of neurons and myelin sheath in the injured area of spinal cord in group D was relatively complete and continuous, and the number of Nissl bodies and the positive area of myelin sheath in group D were significantly better than those in groups B and C ( P<0.05). NF200 immunofluorescence staining and Western blot assay results showed that the relative expression of NF200 protein in group D was significantly higher than that in groups B and C ( P<0.05). CD31 immunofluorescence staining showed that the fluorescence intensity of group D was better than that of groups B and C at 28 days after operation, and tubular or linear neovascularization could be seen. The relative expressions of Ang-1 and Tie-2 proteins in group D were significantly higher than those in groups B and C at 7 and 28 days after operation ( P<0.05). The relative expressions of PDGF-B and PDGFR-β proteins in group D were significantly higher than those in groups B and C, and group B was significantly higher than group C at 28 days after operation ( P<0.05). The relative expressions of VEGF-A and VEGFR2 proteins in group D were higher than those in groups B and C, showing significant difference when compared with group B ( P<0.05), but only the expression of VEGF-A protein was significantly higher than that in group C ( P<0.05). There was significant difference only in VEGFR-2 protein between groups B and C ( P<0.05).

Conclusion

TGTP may enhance the revascularization of the injured area and protect the neurons, thus alleviating the injury of spinal cord tissue structure and promoting the recovery of neurological function after SCI in rats.

Effect of Electroacupuncture Stimulation on Proliferation and Differentiation of Endogenous Neural Stem Cells in Rats with Spinal Cord Injury

The aim of this work was to investigate the effects of electroacupuncture (EA) stimulation on the proliferation and differentiation of endogenous neural stem cells (NSCs) in rats with spinal cord injury (SCI). One hundred rats were included and randomly divided into the sham-operation (SO) group, model (MO) group, EA group, and preacupuncture stimulation (PAS) group, with 25 rats in each group. All the rats in the SO group had their spinal cord of thoracic segment T10 exposed but without SCI. In the remaining three groups, the modified Allen's weight dropping method was adopted to make SCI models. Those in the SO group and the MO group did not receive any treatment. Those in the EA group were treated with EA after the modelling was completed, which stopped when the samples were collected at each time point. The spinal cord tissue of rats was subjected to immunohistochemical staining and real-time quantitative polymerase chain reaction (PCR) to detect the expressions of neurofilament nestin and glial fibrillary acidic protein (GFAP). The Basso-Beattie-Bresnahan (BBB) score of the MO group was much lower than that of the SO group on the 3rd, 7th, and 14th days after surgery (P < 0.05). The BBB scores of the EA group and PAS group were notably higher than that of the MO group (P < 0.05). The number of nestin-, GFAP-, and MAP-2-positive cells was significantly increased in rat tissues after spinal cord injury. On the 3rd, 7th, and 14th days postoperatively, the numbers of nestin-positive cells in the EA and PAS groups were considerably higher than those in the MO group (P < 0.01). However, the numbers of GFAP-positive cells in the EA and PAS groups were considerably decreased compared with those in the MO group (P < 0.01). The positive rate of MAP-2 in the model group was significantly increased compared to that in the sham-operation group (P < 0.001). The positive rates of MAP-2 in the EA group and PAS group were significantly higher than those in the MO group (P < 0.01). After spinal cord injury, EA could activate the proliferation of endogenous NSCs and promote their differentiation into neuronal cells. Consequently, injuries were repaired, and functions were rehabilitated.

Application of Injectable Hydrogels as Delivery Systems in Spinal Cord Injury

Spinal cord injury (SCI) is a severe neurological injury caused by traffic accidents, trauma, or falls, which leads to significant loss of sensory, motor, and autonomous functions and seriously affects the patient's life quality. Although considerable progress has been made in mitigating secondary injury and promoting the regeneration/repair of SCI, the therapeutic effects need to be improved due to drug availability. Given their good biocompatibility, biodegradability, and low immunogenicity, injectable hydrogels can be used as delivery systems to achieve controlled release of drugs and other substances (cells and proteins, etc.), offering new hope for SCI repair. In this article, we summarized the types of injectable hydrogels, analyzed their application as delivery systems in SCI, and further discussed the mechanisms of hydrogels in the treatment of SCI, such as anti-inflammatory, antioxidant, anti-apoptosis, and pro-neurogenesis. Moreover, we highlighted the potential benefits of hydrogels in the treatment of SCI in combination with therapies, including the recent advances and achievements of these promising tools. Our review may offer new strategies for the development of SCI treatments based on injectable hydrogels as delivery systems.

Recent progress and challenges in the treatment of spinal cord injury

Spinal cord injury (SCI) disrupts the structural and functional connectivity between the higher center and the spinal cord, resulting in severe motor, sensory, and autonomic dysfunction with a variety of complications. The pathophysiology of SCI is complicated and multifaceted, and thus individual treatments acting on a specific aspect or process are inadequate to elicit neuronal regeneration and functional recovery after SCI. Combinatory strategies targeting multiple aspects of SCI pathology have achieved greater beneficial effects than individual therapy alone. Although many problems and challenges remain, the encouraging outcomes that have been achieved in preclinical models offer a promising foothold for the development of novel clinical strategies to treat SCI. In this review, we characterize the mechanisms underlying axon regeneration of adult neurons and summarize recent advances in facilitating functional recovery following SCI at both the acute and chronic stages. In addition, we analyze the current status, remaining problems, and realistic challenges towards clinical translation. Finally, we consider the future of SCI treatment and provide insights into how to narrow the translational gap that currently exists between preclinical studies and clinical practice. Going forward, clinical trials should emphasize multidisciplinary conversation and cooperation to identify optimal combinatorial approaches to maximize therapeutic benefit in humans with SCI.

Exercise training remodels inguinal white adipose tissue through adaptations in innervation, vascularization, and the extracellular matrix

Inguinal white adipose tissue (iWAT) is essential for the beneficial effects of exercise training on metabolic health. The underlying mechanisms for these effects are not fully understood, and here, we test the hypothesis that exercise training results in a more favorable iWAT structural phenotype. Using biochemical, imaging, and multi-omics analyses, we find that 11 days of wheel running in male mice causes profound iWAT remodeling including decreased extracellular matrix (ECM) deposition and increased vascularization and innervation. We identify adipose stem cells as one of the main contributors to training-induced ECM remodeling, show that the PRDM16 transcriptional complex is necessary for iWAT remodeling and beiging, and discover neuronal growth regulator 1 (NEGR1) as a link between PRDM16 and neuritogenesis. Moreover, we find that training causes a shift from hypertrophic to insulin-sensitive adipocyte subpopulations. Exercise training leads to remarkable adaptations to iWAT structure and cell-type composition that can confer beneficial changes in tissue metabolism.

VEGFA Isoforms as Pro-Angiogenic Therapeutics for Cerebrovascular Diseases

Therapeutic angiogenesis has long been considered a viable treatment for vasculature disruptions, including cerebral vasculature diseases. One widely-discussed treatment method to increase angiogenesis is vascular endothelial growth factor (VEGF) A. In animal models, treatment with VEGFA proved beneficial, resulting in increased angiogenesis, increased neuronal density, and improved outcome. However, VEGFA administration in clinical trials has thus far failed to replicate the promising results seen in animal models. The lack of beneficial effects in humans and the difficulty in medicinal translation may be due in part to administration methods and VEGFA's ability to increase vascular permeability. One solution to mitigate the side effects of VEGFA may be found in the VEGFA isoforms. VEGFA is able to produce several different isoforms through alternative splicing. Each VEGFA isoform interacts differently with both the cellular components and the VEGF receptors. Because of the different biological effects elicited, VEGFA isoforms may hold promise as a tangible potential therapeutic for cerebrovascular diseases.

Glycoprotein non-metastatic melanoma B interacts with epidermal growth factor receptor to regulate neural stem cell survival and differentiation

The functional recovery following spinal cord injury (SCI) remains a challenge clinically. Among the proteins interacted with the glycoprotein non-metastatic melanoma B (GPNMB), epidermal growth factor receptor (EGFR) during activation is able to promote the proliferation of neural stem cells (NSCs) in the spinal cord. We investigated the roles of GPNMB and EGFR in regulating the survival and differentiation of the NSCs. By overexpression and short-hairpin RNA-mediated knockdown of GPNMB in the NSCs, GPNMB promoted cell viability and differentiation by increasing the expressions of βIII tubulin and CNPase (2',3'-cyclic nucleotide 3-phosphodiesterase). Using co-immunoprecipitation, we found that EGFR interacted with GPNMB. Furthermore, EGFR had a similar effect as GPNMB on promoting cell viability and differentiation. Overexpression of EGFR reversed the decrease in viability and differentiation caused by the knockdown of GPNMB, and vice versa. Last but not least, we tested the effect of GPNMB and EGFR on several intracellular pathways and found that GPNMB/EGFR modulated the phosphorylated (p)-c-Jun N-terminal kinase (JNK)1/2/JNK1/2 ratio and the p-nuclear factor κB (NF-κB p65)/NF-κB p65 ratio. In sum, our findings demonstrate the interaction between GPNMB and EGFR that regulates cell bioprocesses, with the hope to provide a new strategy of SCI therapy.

The neural stem cell properties of Pkd2l1+ cerebrospinal fluid-contacting neurons in vivo

The neural stem cells (NSCs) in the ventricular-subventricular zone of the adult mammalian spinal cord may be of great benefit for repairing spinal cord injuries. However, the sources of NSCs remain unclear. Previously, we have confirmed that cerebrospinal fluid-contacting neurons (CSF-cNs) have NSC potential in vitro. In this study, we verified the NSC properties of CSF-cNs in vivo. In mouse spinal cords, Pkd2l1+ CSF-cNs localized around the central canal express NSC markers. In vitro, Pkd2l1+ CSF-cNs form a neurosphere and express NSC markers. Activation and proliferation of CSF-cNs can be induced by injection of the neurotrophic factors basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) into the lateral ventricle. Spinal cord injury (SCI) also induces NSC activation and proliferation of CSF-cNs. Collectively, our results demonstrate that Pkd2l1+ CSF-cNs have NSC properties in vivo and may be involved in SCI recovery.

Regulating Endogenous Neural Stem Cell Activation to Promote Spinal Cord Injury Repair

Spinal cord injury (SCI) affects millions of individuals worldwide. Currently, there is no cure, and treatment options to promote neural recovery are limited. An innovative approach to improve outcomes following SCI involves the recruitment of endogenous populations of neural stem cells (NSCs). NSCs can be isolated from the neuroaxis of the central nervous system (CNS), with brain and spinal cord populations sharing common characteristics (as well as regionally distinct phenotypes). Within the spinal cord, a number of NSC sub-populations have been identified which display unique protein expression profiles and proliferation kinetics. Collectively, the potential for NSCs to impact regenerative medicine strategies hinges on their cardinal properties, including self-renewal and multipotency (the ability to generate de novo neurons, astrocytes, and oligodendrocytes). Accordingly, endogenous NSCs could be harnessed to replace lost cells and promote structural repair following SCI. While studies exploring the efficacy of this approach continue to suggest its potential, many questions remain including those related to heterogeneity within the NSC pool, the interaction of NSCs with their environment, and the identification of factors that can enhance their response. We discuss the current state of knowledge regarding populations of endogenous spinal cord NSCs, their niche, and the factors that regulate their behavior. In an attempt to move towards the goal of enhancing neural repair, we highlight approaches that promote NSC activation following injury including the modulation of the microenvironment and parenchymal cells, pharmaceuticals, and applied electrical stimulation.

Neuroprotective Effects of VEGF-A Nanofiber Membrane and FAAH Inhibitor URB597 Against Oxygen-Glucose Deprivation-Induced Ischemic Neuronal Injury

INTRODUCTION

Brain ischemia is a common neurological disorder worldwide that activates a cascade of pathophysiological events involving decreases in oxygen and glucose levels. Despite substantial efforts to explore its pathogenesis, the management of ischemic neuronal injury remains an enormous challenge. Accumulating evidence suggests that VEGF modified nanofiber (NF) materials and the fatty-acid amide hydrolase (FAAH) inhibitor URB597 exert an influence on alleviating ischemic brain damage. We aimed to further investigate their effects on primary hippocampal neurons, as well as the underlying mechanisms following oxygen-glucose deprivation (OGD).

METHODS

Different layers of VEGF-A loaded polycaprolactone (PCL) nanofibrous membranes were first synthesized by using layer-by-layer (LBL) self-assembly of electrospinning methods. The physicochemical and biological properties of VEGF-A NF membranes, and their morphology, hydrophilicity, and controlled-release of VEGF-A were then estimated. Furthermore, the effects of VEGF-A NF and URB597 on OGD-induced mitochondrial oxidative stress, inflammatory responses, neuronal apoptosis, and endocannabinoid signaling components were assessed.

RESULTS

The VEGF-A NF membrane and URB597 can not only promote hippocampal neuron adhesion and viability following OGD but also exhibited antioxidant/anti-inflammatory and mitochondrial membrane potential protection. The VEGF-A NF membrane and URB597 also inhibited OGD-induced cellular apoptosis through activating CB1R signaling. These results indicate that VEGF-A could be controlled-released by LBL self-assembled NF membranes.

DISCUSSION

The VEGF-A NF membrane and URB597 displayed positive synergistic neuroprotective effects through the inhibition of mitochondrial oxidative stress and activation of CB1R/PI3K/AKT/BDNF signaling, suggesting that a VEGF-A loaded NF membrane and the FAAH inhibitor URB597 could be of therapeutic value in ischemic cerebrovascular diseases.

NSCs Migration Promoted and Drug Delivered Exosomes-Collagen Scaffold via a Bio-Specific Peptide for One-Step Spinal Cord Injury Repair

Spinal cord injury (SCI) is plaguing medical professionals globally due to the complexity of injury progression. Based on tissue engineering technology, there recently emerges a promising way by integrating drugs with suitable scaffold biomaterials to mediate endogenous neural stem cells (NSCs) to achieve one-step SCI repair. Herein, exosomes extracted from human umbilical cord-derived mesenchymal stem cells (MExos) are found to promote the migration of NSCs in vitro/in vivo. Utilizing MExos as drug delivery vehicles, a NSCs migration promoted and paclitaxel (PTX) delivered MExos-collagen scaffold is designed via a novel dual bio-specificity peptide (BSP) to effectively retain MExos within scaffolds. By virtue of the synergy that MExos recruit endogenous NSCs to the injured site, and PTX induce NSCs to give rise to neurons, this multifunctional scaffold has shown superior performance for motor functional recovery after complete SCI in rats by enhancing neural regeneration and reducing scar deposition. Besides, the dual bio-specific peptide demonstrates the capacity of tethering other cells-derived exosomes on collagen scaffold, such as erythrocytes-derived or NSCs-derived exosomes on collagen fibers or membranes. The resulting exosomes-collagen scaffold may serve as a potential multifunctional therapy modality for various disease treatments including SCI.

Examination and characterisation of the effect of amitriptyline therapy for chronic neuropathic pain on neuropeptide and proteomic constituents of human cerebrospinal fluid

INTRODUCTION

Amitriptyline is prescribed to reduce the intensity of chronic neuropathic pain. There is a paucity of validated in vivo evidence in humans regarding amitriptyline's mechanism of action. We examined the effect of amitriptyline therapy on cerebrospinal fluid (CSF) neuropeptides and proteome in patients with chronic neuropathic pain to identify potential mechanisms of action of amitriptyline.

METHODS

Patients with lumbar radicular neuropathic pain were selected for inclusion with clinical and radiological signs and a >50% reduction in pain in response to a selective nerve root block. Baseline (pre-treatment) and 8-week (post-treatment) pain scores with demographics were recorded. CSF samples were taken at baseline (pre-treatment) and 8 weeks after amitriptyline treatment (post-treatment). Proteome analysis was performed using mass spectrometry and secreted cytokines, chemokines and neurotrophins were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

A total of 9/16 patients experienced a >30% reduction in pain after treatment with amitriptyline and GO analysis demonstrated that the greatest modulatory effect was on immune system processes. KEGG analysis also identified a reduction in PI3K-Akt and MAPK signalling pathways in responders but not in non-responders. There was also a significant decrease in the chemokine eotaxin-1 (p ​= ​0.02) and a significant increase in the neurotrophin VEGF-A (p ​= ​0.04) in responders.

CONCLUSION

The CSF secretome and proteome was modulated in responders to amitriptyline verifying many pre-clinical and in vitro models. The predominant features were immunomodulation with a reduction in pro-inflammatory pathways of neuronal-glia communications and evidence of a neurotrophic effect.

miR-30b Promotes spinal cord sensory function recovery via the Sema3A/NRP-1/PlexinA1/RhoA/ROCK Pathway

Spinal cord injury (SCI) induces both motor and sensory dysfunctions. We wondered whether miR-30b could promote primary sensory neuron (PSN) axon growth in inhibitory microenvironment. The neurite growth was promoted by miR-30b agomir and inhibited by antagomir. MiR-30b targeted and degraded sema3A mRNA. MiR-30b regulated the formation of sema3A-NRP-1-PlexinA1 complex via targeting sema3A. The neurite length was induced by the miR-30b agomir, and the application of sema3A protein could reverse the effect of agomir. GTP-RhoA and ROCK expression were down-regulated by miR-30b. Neurite outgrowth that inhibited by sema3A and the miR-30b antagomir was increased by Y-27632. Agomir promoted neurite growth in NogoA inhibitory conditions, which indicated miR-30b could both enhance neuronal intrinsic regenerative ability and promote neurite growth against inhibitory microenvironment via Sema3A/NRP-1/PlexinA1/RhoA/ROCK axis. The agomir could also regulate Sema3A/NRP-1/PlexinA1/RhoA/ROCK axis in vivo and restore spinal cord sensory conductive function. In conclusion, miR-30b could be a novel target for sensation recovery after SCI.

Thyroid Hormone and Neural Stem Cells: Repair Potential Following Brain and Spinal Cord Injury

Neurodegenerative diseases are characterized by chronic neuronal and/or glial cell loss, while traumatic injury is often accompanied by the acute loss of both. Multipotent neural stem cells (NSCs) in the adult mammalian brain spontaneously proliferate, forming neuronal and glial progenitors that migrate toward lesion sites upon injury. However, they fail to replace neurons and glial cells due to molecular inhibition and the lack of pro-regenerative cues. A major challenge in regenerative biology therefore is to unveil signaling pathways that could override molecular brakes and boost endogenous repair. In physiological conditions, thyroid hormone (TH) acts on NSC commitment in the subventricular zone, and the subgranular zone, the two largest NSC niches in mammals, including humans. Here, we discuss whether TH could have beneficial actions in various pathological contexts too, by evaluating recent data obtained in mammalian models of multiple sclerosis (MS; loss of oligodendroglial cells), Alzheimer’s disease (loss of neuronal cells), stroke and spinal cord injury (neuroglial cell loss). So far, TH has shown promising effects as a stimulator of remyelination in MS models, while its role in NSC-mediated repair in other diseases remains elusive. Disentangling the spatiotemporal aspects of the injury-driven repair response as well as the molecular and cellular mechanisms by which TH acts, could unveil new ways to further exploit its pro-regenerative potential, while TH (ant)agonists with cell type-specific action could provide safer and more target-directed approaches that translate easier to clinical settings.

Role of EGFR in the Nervous System

Epidermal growth factor receptor (EGFR) is the first discovered member of the receptor tyrosine kinase superfamily and plays a fundamental role during embryogenesis and in adult tissues, being involved in growth, differentiation, maintenance and repair of various tissues and organs. The role of EGFR in the regulation of tissue development and homeostasis has been thoroughly investigated and it has also been demonstrated that EGFR is a driver of tumorigenesis. In the nervous system, other growth factors, and thus other receptors, are important for growth, differentiation and repair of the tissue, namely neurotrophins and neurotrophins receptors. For this reason, for a long time, the role of EGFR in the nervous system has been underestimated and poorly investigated. However, EGFR is expressed both in the central and peripheral nervous systems and it has been demonstrated to have specific important neurotrophic functions, in particular in the central nervous system. This review discusses the role of EGFR in regulating differentiation and functions of neurons and neuroglia. Furthermore, its involvement in regeneration after injury and in the onset of neurodegenerative diseases is examined.

Possible role of EphA4 and VEGFR2 interactions in neural stem and progenitor cell differentiation

Neural stem and progenitor cells (NSPCs) are important pluripotent stem cells, which have potential applications for cell replacement therapy. Ephrin receptors (Ephs) and angiogenic growth factor receptors have a major impact on the proliferation and differentiation of NSPCs. Potential interactions between EphA4 and vascular endothelial growth factor (VEGF) receptor (VEGFR) 2, and their roles in NSPC differentiation in vitro remain unknown. In the present study, mouse embryonic NSPCs were treated with ephrin-A1 or VEGF165 alone as well as with combination treatment (ephrin-A1 + VEGF165). Immunoprecipitation and immunoblot assays demonstrated that wild-type EphA4, but not the EphA4 kinase-dead mutant, interacted with VEGFR2 when overexpressed in 293T cells. This interaction was inhibited by dominant-negative EphA4. The percentage of β-tubulin III (Tuj1)⁺, but not glial fibrillary acid protein (GFAP)⁺ cells, was increased in the ephrin-A1 + VEGF165 combination group as compared to the VEGF165 alone group in mouse embryonic NSPCs. VEGF165-induced neuronal differentiation was potentiated by ephrin-A1 in NSPCs in vitro and ephrin-A1- or VEGF165-stimulated EphA4 and VEGFR2 interactions may mediate the signaling pathway.

miR-22-3p enhances the intrinsic regenerative abilities of primary sensory neurons via the CBL/p-EGFR/p-STAT3/GAP43/p-GAP43 axis

Spinal cord injury (SCI) is a devastating disease. Strategies that enhance the intrinsic regenerative ability are very important for the recovery of SCI to radically prevent the occurrence of sensory disorders. Epidermal growth factor (EGF) showed a limited effect on the growth of primary sensory neuron neurites due to the degradation of phosphorylated-epidermal growth factor receptor (p-EGFR) in a manner dependent on Casitas B-lineage lymphoma (CBL) (an E3 ubiquitin-protein ligase). MiR-22-3p predicted from four databases could target CBL to inhibit the expression of CBL, increase p-EGFR levels and neurites length via STAT3/GAP43 pathway rather than Erk1/2 axis. EGF, EGFR, and miR-22-3p were downregulated sharply after injury. In vivo miR-22-3p Agomir application could regulate CBL/p-EGFR/p-STAT3/GAP43/p-GAP43 axis, and restore spinal cord sensory conductive function. This study clarified the mechanism of the limited promotion effect of EGF on adult primary sensory neuron neurite and targeting miR-22-3p could be a novel strategy to treat sensory dysfunction after SCI.

Application of stem cells and chitosan in the repair of spinal cord injury

Cytology and histology obstacles have been the main barriers to multiple tissues injury repair. In search of the most promising treatment strategies for spinal cord injury (SCI), stem cell-based transplantation coupled with various materials/technologies have been explored extensively to enhance SCI repair. Chitosan (CS) has demonstrated immense potential for widespread application in the form of scaffolds and micro-particles for SCI repair. The current review summarizes the evidences for stem cell-based transplantation and CS in SCI repair. Stem cells transplantation, which plays a key role in the repair of SCI, mainly results from its neural differentiation potential and neurotrophic effects. Application of CS enhances the survival of grafted stem cells, upregulates the expression level of neurotrophic factors and heightens the neural differentiation of stem cells as well as the functional recovery of spinal cord. Meanwhile, CS can also be exploited as growth factors/RNA carriers to control the release of regenerating molecules which are beneficial to damage spinal cord repair.

Employing Endogenous NSCs to Promote Recovery of Spinal Cord Injury

Endogenous neural stem cells (NSCs) exist in the central canal of mammalian spinal cords. Under normal conditions, these NSCs remain quiescent and express FoxJ1. After spinal cord injury (SCI), the endogenous NSCs of a heterogeneous nature are activated and proliferate and migrate towards the lesion site and mainly differentiate into astrocytes to repair the injured tissue. In vitro, spinal cord NSCs are multipotent and can differentiate into neurons, astrocytes, and oligodendrocytes. The altered microenvironments after SCI play key roles on the fate determination of activated NSCs, especially on the neuronal specification potential. Studies show that the activated spinal cord NSCs can generate interneurons when transplanted into the adult hippocampus. In addition, the spinal cord NSCs exhibit low immunogenicity in a transplantation context, thus implicating a promising therapeutic potential on SCI recovery. Here, we summarize the characteristics of spinal cord NSCs, especially their properties after injury. With a better understanding of endogenous NSCs under normal and SCI conditions, we may be able to employ endogenous NSCs for SCI repair in the future.

Vascular endothelial growth factor activates neural stem cells through epidermal growth factor receptor signal after spinal cord injury

AIMS

Neural stem cells (NSCs) in the adult mammalian spinal cord are activated in response to spinal cord injury (SCI); however, mechanisms modulating this process are not clear. Here, we noticed SCI elevated expression of vascular endothelial growth factor (VEGF) and we aimed to validate the roles of VEGF in NSCs activation after SCI and investigated the related signals during the process.

METHODS

In vitro we detected whether VEGF promoted spinal cord NSCs proliferation and investigated the involved signals; In vivo, we injected VEGF into rat spinal cord to check the NSCs activation.

RESULTS

In vitro, VEGF triggered spinal cord NSCs proliferation and maintained self-renewal. Further investigations demonstrated VEGF transactivated epidermal growth factor receptor (EGFR) through VEGF receptor 2 (VEGFR2) to promote spinal cord NSCs proliferation. In vivo, we injected VEGF into spinal cord by laminectomy to confirm the roles of VEGF-VEGFR2-EGFR signals in NSCs activation. VEGF significantly elevated the number of activated NSCs and increased EGFR phosphorylation. In contrast, intraspinal injection of specific inhibitors targeting EGFR and VEGFR2 decreased NSCs activation after SCI. Our results demonstrate that VEGF-VEGFR2-EGFR axis is important for NSCs activation after SCI, providing new insights into the mechanisms of spinal cord NSCs activation postinjury.