Molecular approaches to spinal cord repair

Neural regeneration in the human central nervous system-from understanding the underlying mechanisms to developing treatments. Where do we stand today?

Mature neurons in the human central nervous system (CNS) fail to regenerate after injuries. This is a common denominator across different aetiologies, including multiple sclerosis, spinal cord injury and ischemic stroke. The lack of regeneration leads to permanent functional deficits with a substantial impact on patient quality of life, representing a significant socioeconomic burden worldwide. Great efforts have been made to decipher the responsible mechanisms and we now know that potent intra- and extracellular barriers prevent axonal repair. This knowledge has resulted in numerous clinical trials, aiming to promote neuroregeneration through different approaches. Here, we summarize the current understanding of the causes to the poor regeneration within the human CNS. We also review the results of the treatment attempts that have been translated into clinical trials so far.

Human placenta-derived mesenchymal stem cells stimulate neuronal regeneration by promoting axon growth and restoring neuronal activity

In the last decades, mesenchymal stem cells (MSCs) have become the cornerstone of cellular therapy due to their unique characteristics. Specifically human placenta-derived mesenchymal stem cells (hPMSCs) are highlighted for their unique features, including ease to isolate, non-invasive techniques for large scale cell production, significant immunomodulatory capacity, and a high ability to migrate to injuries. Researchers are exploring innovative techniques to overcome the low regenerative capacity of Central Nervous System (CNS) neurons, with one promising avenue being the development of tailored mesenchymal stem cell therapies capable of promoting neural repair and recovery. In this context, we have evaluated hPMSCs as candidates for CNS lesion regeneration using a skillful co-culture model system. Indeed, we have demonstrated the hPMSCs ability to stimulate damaged rat-retina neurons regeneration by promoting axon growth and restoring neuronal activity both under normoxia and hypoxia conditions. With our model we have obtained neuronal regeneration values of 10%-14% and axonal length per neuron rates of 19-26, μm/neuron. To assess whether the regenerative capabilities of hPMSCs are contact-dependent effects or it is mediated through paracrine mechanisms, we carried out transwell co-culture and conditioned medium experiments confirming the role of secreted factors in axonal regeneration. It was found that hPMSCs produce brain derived, neurotrophic factor (BDNF), nerve-growth factor (NGF) and Neurotrophin-3 (NT-3), involved in the process of neuronal regeneration and restoration of the physiological activity of neurons. In effect, we confirmed the success of our treatment using the patch clamp technique to study ionic currents in individual isolated living cells demonstrating that in our model the regenerated neurons are electrophysiologically active, firing action potentials. The outcomes of our neuronal regeneration studies, combined with the axon-regenerating capabilities exhibited by mesenchymal stem cells derived from the placenta, present a hopeful outlook for the potential therapeutic application of hPMSCs in the treatment of neurological disorders.

Regulation of the JAK/STAT signaling pathway in spinal cord injury: an updated review

Cytokines are involved in neural homeostasis and pathological processes associated with neuroinflammation after spinal cord injury (SCI). The biological effect of cytokines, including those associated with acute or chronic SCI pathologies, are the result of receptor-mediated signaling through the Janus kinases (JAKs) as well as the signal transducers and activators of transcription (STAT) DNA-binding protein families. Although therapies targeting at cytokines have led to significant changes in the treatment of SCI, they present difficulties in various aspects for the direct use by patients themselves. Several small-molecule inhibitors of JAKs, which may affect multiple pro-inflammatory cytokine-dependent pathways, as well as STATs, are in clinical development for the treatment of SCI. This review describes the current understanding of the JAK-STAT signaling in neuroendocrine homeostasis and diseases, together with the rationale for targeting at this pathway for the treatment of SCI.

Ayurveda, yoga, and acupuncture therapies in alleviating the symptom score among patients with spinal cord injury - A systematic review

BACKGROUND

Spinal cord injury (SCI) is the leading cause of motor and sensory abnormalities due to damage caused to any part of the spinal cord resulting from trauma, disease, or degeneration. Most of the disability caused will be irreversible with various systemic manifestations. Hence, management of SCI focuses on minimising disability, diminishing limitations due to impairment, and improving quality of life, emotional, and psychological aspects.

AIM

This review is aimed at describing Ayurveda, Yoga, and Acupuncture therapies in the management of SCI as individual and integrated approaches for alleviating the symptom score in patients with SCI.

METHODS

The data was collected from six databases, including PubMed Central, the Cochrane Library, Google Scholar, Scopus, MEDLINE, and Grey Literature. The subjects in these studies were between the ages group 21-70 years and had been previously diagnosed with SCI and its clinical presentation. The interventions used in the selected studies incorporate Ayurveda (medicinal system of longevity) herbal medications, Panchakarma (five methods) treatment, diet, and yoga (mind-body medicine) therapy. Full-text publications in English, and research designs such as randomised controlled trials, case studies, review articles and cohort studies were included. Letter to the editor, study protocol, animal trials, and in vitro studies were excluded.

RESULTS

216 records were identified using keywords such as spinal cord injury, Äyurveda, Acupuncture, païca karma, rehabilitation, and yoga. After applying inclusion and exclusion criteria, 28 articles were selected for synthesis, which contain 12 case studies, 12 literature review articles, 2 randomised controlled trials, 1 cohort study, and 1 meta-analysis.

CONCLUSION

The integration of Ayurveda management, including Panchakarmatherapy and Ayurveda medications, with other alternative therapies like Acupuncture, Yoga, and Rehabilitation improved muscle strength, quality of life, range of motion, and neuronal function, and reduced depression, stress, and pain with symptom scores.

Biomimetic engineered approaches for neural tissue engineering: Spinal cord injury

The healing process for spinal cord injuries is complex and presents many challenges. Current advances in nerve regeneration are based on promising tissue engineering techniques, However, the chances of success depend on better mimicking the extracellular matrix (ECM) of neural tissue and better supporting neurons in a three-dimensional environment. The ECM provides excellent biological conditions, including desirable morphological features, electrical conductivity, and chemical compositions for neuron attachment, proliferation and function. This review outlines the rationale for developing a construct for neuron regrowth in spinal cord injury using appropriate biomaterials and scaffolding techniques.

A novel cell-free intrathecal approach with PRP for the treatment of spinal cord multiple sclerosis in cats

Background

Multiple sclerosis (MS) is a progressive autoimmune demyelinating disease of the central nervous system. To date, there is no effective therapy for it. Our study aimed to determine the potential role of platelet-rich plasma (PRP) in the treatment of MS in cats.

Methods

The current study was conducted on 15 adult Persian cats that were divided into three groups: control negative, control positive (ethidium bromide (EB)-treated group), and PRP co-treated group (EB-treated group intrathecally injected with PRP on day 14 post-spinal cord injury). PRP was obtained by centrifuging blood on anticoagulant citrate dextrose and activating it with red and green laser diodes. The Basso–Beattie–Bresnahan (BBB) scores were used to assess the motor function recovery on days 1, 3, 7, 14, 20, and 28 following 14 days from EB injection. Moreover, magnetic resonance imaging (MRI) analysis, histopathological investigations, transmission electron microscopy (TEM) studies, and immunohistochemical analysis were conducted, and the gene expressions of nerve growth factors (NGFs), brain-derived neurotrophic factors (BDNF), and stromal cell-derived factors (SDF) were evaluated.

Results

Our results indicated that PRP had a significant ameliorative effect on the motor function of the hindlimbs as early as day 20 and so on. MRI revealed that the size and intensity of the lesion were significantly reduced in the PRP co-treated group. The histopathological and TEM investigations demonstrated that the PRP co-treated group had a significant improvement in the structure and organization of the white matter, as well as a high remyelination capacity. Furthermore, a significant increase in myelin basic protein and Olig2 immunoreactivity as well as a reduction in Bax and glial fibrillar acidic protein immune markers was observed. NGFs were found to be upregulated by gene expression.

Conclusion

As a result, we concluded that the intrathecal injection of PRP was an effective, safe, and promising method for the treatment of MS.

Ultrafast Doppler imaging and ultrasound localization microscopy reveal the complexity of vascular rearrangement in chronic spinal lesion

Acute spinal cord injury (SCI) leads to severe damage to the microvascular network. The process of spontaneous repair is accompanied by formation of new blood vessels; their functionality, however, presumably very important for functional recovery, has never been clearly established, as most studies so far used fixed tissues. Here, combining ultrafast Doppler imaging and ultrasound localization microscopy (ULM) on the same animals, we proceeded at a detailed analysis of structural and functional vascular alterations associated with the establishment of chronic SCI, both at macroscopic and microscopic scales. Using a standardized animal model of SCI, our results demonstrate striking hemodynamic alterations in several subparts of the spinal cord: a reduced blood velocity in the lesion site, and an asymmetrical hypoperfusion caudal but not rostral to the lesion. In addition, the worsening of many evaluated parameters at later time points suggests that the neoformed vascular network is not yet fully operational, and reveals ULM as an efficient in vivo readout for spinal cord vascular alterations. Finally, we show statistical correlations between the diverse biomarkers of vascular dysfunction and SCI severity. The imaging modality developed here will allow evaluating recovery of vascular function over time in pre-clinical models of SCI. Also, used on SCI patients in combination with other quantitative markers of neural tissue damage, it may help classifying lesion severity and predict possible treatment outcomes in patients.

Spinal Cord Injury Significantly Alters the Properties of Reticulospinal Neurons: I. Biophysical Properties, Firing Patterns, Excitability, and Synaptic Inputs

Following spinal cord injury (SCI) for larval lampreys, descending axons of reticulospinal (RS) neurons regenerate, and locomotor function gradually recovers. In the present study, the electrophysiological properties of uninjured (left)-injured (right) pairs of large, identified RS neurons were compared following rostral, right spinal cord hemi-transections (HTs). First, changes in firing patterns of injured RS neurons began in as little as 2-3 days following injury, these changes were maximal at ~2-3 weeks (wks), and by 12-16 wks normal firing patterns were restored for the majority of neurons. Second, at ~2-3 wks following spinal cord HTs, injured RS neurons displayed several significant changes in properties compared to uninjured neurons: (a) more hyperpolarized V_REST; (b) longer membrane time constant and larger membrane capacitance; (c) increased voltage and current thresholds for action potentials (APs); (d) larger amplitudes and durations for APs; (e) higher slope for the repolarizing phase of APs; (f) virtual absence of some afterpotential components, including the slow afterhyperpolarization (sAHP); (g) altered, injury-type firing patterns; and (h) reduced average and peak firing (spiking) frequencies during applied depolarizing currents. These altered properties, referred to as the "injury phenotype", reduced excitability and spiking frequencies of injured RS neurons compared to uninjured neurons. Third, artificially injecting a current to add a sAHP waveform following APs for injured neurons or removing the sAHP following APs for uninjured neurons did not convert these neurons to normal firing patterns or injury-type firing patterns, respectively. Fourth, trigeminal sensory-evoked synaptic responses recorded from uninjured and injured pairs of RS neurons were not significantly different. Following SCI, injured lamprey RS neurons displayed several dramatic changes in their biophysical properties that are expected to reduce calcium influx and provide supportive intracellular conditions for axonal regeneration.

Transplantation of a vascularized pedicle of hemisected spinal cord to establish spinal cord continuity after removal of a segment of the thoracic spinal cord: A proof-of-principle study in dogs

Introduction

Glial scar formation impedes nerve regeneration/reinnervation after spinal cord injury (SCI); therefore, removal of scar tissue is essential for SCI treatment.

Aims

To investigate whether removing a spinal cord and transplanting a vascularized pedicle of hemisected spinal cord from the spinal cord caudal to the transection can restore motor function, to aid in the treatment of future clinical spinal cord injuries. We developed a canine model. After removal of a 1‐cm segment of the thoracic (T10–T11) spinal cord in eight beagles, a vascularized pedicle of hemisected spinal cord from the first 1.5 cm of the spinal cord caudal to the transection (cut along the posterior median sulcus of the spinal cord) was transplanted to bridge the transected spinal cord in the presence of a fusogen (polyethylene glycol, PEG) in four of the eight dogs. We used various forms of imaging, electron microscopy, and histologic data to determine that after our transplantation of a vascular pedicled hemisection to bridge the transected spinal cord, electrical continuity across the spinal bridge was restored.

Results

Motor function was restored following our transplantation, as confirmed by the re‐establishment of anatomic continuity along with interfacial axonal sprouting.

Conclusion

Taken together, our findings suggest that SCI patients—who have previously been thought to have irreversible damage and/or paralysis—may be treated effectively with similar operative techniques to re‐establish electrical and functional continuity following SCI.

Inhibition of astrocyte hemichannel improves recovery from spinal cord injury

Spinal cord injury (SCI) causes severe disability, and the current inability to restore function to the damaged spinal cord leads to lasting detrimental consequences to patients. One strategy to reduce SCI morbidity involves limiting the spread of secondary damage after injury. Previous studies have shown that connexin 43 (Cx43), a gap junction protein richly expressed in spinal cord astrocytes, is a potential mediator of secondary damage. Here, we developed a specific inhibitory antibody, mouse-human chimeric MHC1 antibody (MHC1), that inhibited Cx43 hemichannels, but not gap junctions, and reduced secondary damage in 2 incomplete SCI mouse models. MHC1 inhibited the activation of Cx43 hemichannels in both primary spinal astrocytes and astrocytes in situ. In both SCI mouse models, administration of MHC1 after SCI significantly improved hind limb locomotion function. Remarkably, a single administration of MHC1 30 minutes after injury improved the recovery up to 8 weeks post-SCI. Moreover, MHC1 treatment decreased gliosis and lesion sizes, increased white and gray matter sparing, and improved neuronal survival. Together, these results suggest that inhibition of Cx43 hemichannel function after traumatic SCI reduces secondary damage, limits perilesional gliosis, and improves functional recovery. By targeting hemichannels specifically with an antibody, this study provides a potentially new, innovative therapeutic approach in treating SCI.

Mechanisms and repair strategies for white matter degeneration in CNS injury and diseases

White matter degeneration is an important pathophysiological event of the central nervous system that is collectively characterized by demyelination, oligodendrocyte loss, axonal degeneration and parenchymal changes that can result in sensory, motor, autonomic and cognitive impairments. White matter degeneration can occur due to a variety of causes including trauma, neurotoxic exposure, insufficient blood flow, neuroinflammation, and developmental and inherited neuropathies. Regardless of the etiology, the degeneration processes share similar pathologic features. In recent years, a plethora of cellular and molecular mechanisms have been identified for axon and oligodendrocyte degeneration including oxidative damage, calcium overload, neuroinflammatory events, activation of proteases, depletion of adenosine triphosphate and energy supply. Extensive efforts have been also made to develop neuroprotective and neuroregenerative approaches for white matter repair. However, less progress has been achieved in this area mainly due to the complexity and multifactorial nature of the degeneration processes. Here, we will provide a timely review on the current understanding of the cellular and molecular mechanisms of white matter degeneration and will also discuss recent pharmacological and cellular therapeutic approaches for white matter protection as well as axonal regeneration, oligodendrogenesis and remyelination.

Olfactory ensheathing cells: Unique glial cells promising for treatments of spinal cord injury

Spinal cord injury (SCI) is generally the consequence of physical damage, which may result in devastating consequences such as paraplegia or paralysis. Some certain candidates for SCI repair are olfactory ensheathing cells (OECs), which are unique glial cells located in the transition region of the peripheral nervous system and central nervous system and perform neuron regeneration in the olfactory system throughout life. Culture studies have clarified many properties of OECs, but their mechanisms of actions are not fully understood. Successful results achieved in animal models showcased that SCI treatment with OEC transplants is suitable for clinical trials. However, clinical trials are limited by difficulties like cell acquisition for autograft transplantation. Despite the improvements in both animal and clinical studies so far, there is still insufficient information about the mechanism of actions, adverse effects, proper application methods, effective subtypes, and sources of cells. This review summarizes pre-clinical and clinical literature focused on the cellular characterization of both OECs in vitro and post-transplantation. We highlight the roles and effects of OECs on (a) the injury-induced glial milieu, (b) neuronal growth/regeneration, and (c) functional recovery after injury. Due to the shown benefits of OECs with in vitro and animal studies and a limited number of clinical trials, where safety and effectivity were shown, it is necessary to conduct more studies on OECs to obtain effective and feasible treatment methods.

Neuroimmune System as a Driving Force for Plasticity Following CNS Injury

Following an injury to the central nervous system (CNS), spontaneous plasticity is observed throughout the neuraxis and affects multiple key circuits. Much of this spontaneous plasticity can elicit beneficial and deleterious functional outcomes, depending on the context of plasticity and circuit affected. Injury-induced activation of the neuroimmune system has been proposed to be a major factor in driving this plasticity, as neuroimmune and inflammatory factors have been shown to influence cellular, synaptic, structural, and anatomical plasticity. Here, we will review the mechanisms through which the neuroimmune system mediates plasticity after CNS injury. Understanding the role of specific neuroimmune factors in driving adaptive and maladaptive plasticity may offer valuable therapeutic insight into how to promote adaptive plasticity and/or diminish maladaptive plasticity, respectively.

Identification of Key Genes and Pathways Involved in the Heterogeneity of Intrinsic Growth Ability Between Neurons After Spinal Cord Injury in Adult Zebrafish

In the adult central nervous system (CNS), axon regeneration is a major hurdle for functional recovery after trauma. The intrinsic growth potential of an injured axon varies widely between neurons. The underlying molecular mechanisms of such heterogeneity are largely unclear. In the present study, the adult zebrafish dataset GSE56842 were downloaded. Differentially expressed genes (DEGs) were sorted and deeply analyzed by bioinformatics methods. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of DEGs were performed with the DAVID. A DEGs-associated protein-protein interaction network was constructed from the STRING database and visualized with Cytoscape software. In total, 621 DEGs were identified. GO analysis showed that the biological processes of DEGs focused mainly on the Notch signaling pathway, cell differentiation and positive regulation of neuron differentiation. The molecular functions mainly included calcium-transporting ATPase activity and calcium ion binding and structural constituents of the cytoskeleton. The cellular components included the plasma membrane, spectrin, and cytoplasmic and membrane-bound vesicles. KEGG pathway analysis showed that these DEGs were mainly involved in the metabolic pathway and Notch signaling pathway, and subnetworks revealed that genes within modules were involved in the metabolic pathway, Wnt signaling pathway, and calcium signaling pathway. This study identified DEG candidate genes and pathways involved in the heterogeneity of the intrinsic growth ability between neurons after spinal cord injury in adult zebrafish, which could facilitate our understanding of the molecular mechanisms underlying axon regeneration, and these candidate genes and pathways could be therapeutic targets for the treatment of CNS injury.

The endocannabinoid 2-AG enhances spontaneous remyelination by targeting microglia

Remyelination is an endogenous process by which functional recovery of damaged neurons is achieved by reinstating the myelin sheath around axons. Remyelination has been documented in multiple sclerosis (MS) lesions and experimental models, although it is often incomplete or fails to affect the integrity of the axon, thereby leading to progressive disability. Microglia play a crucial role in the clearance of the myelin debris produced by demyelination and in inflammation-dependent OPC activation, two processes necessary for remyelination to occur. We show here that following corpus callosum demyelination in the TMEV-IDD viral murine model of MS, there is spontaneous and partial remyelination that involves a temporal discordance between OPC mobilization and microglia activation. Pharmacological treatment with the endocannabinoid 2-AG enhances the clearance of myelin debris by microglia and OPC differentiation, resulting in complete remyelination and a thickening of the myelin sheath. These results highlight the importance of targeting microglia during the repair processes in order to enhance remyelination.

Interferon β-Mediated Protective Functions of Microglia in Central Nervous System Autoimmunity

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) leading to demyelination and axonal damage. It often affects young adults and can lead to neurological disability. Interferon β (IFNβ) preparations represent widely used treatment regimens for patients with relapsing-remitting MS (RRMS) with therapeutic efficacy in reducing disease progression and frequency of acute exacerbations. In mice, IFNβ therapy has been shown to ameliorate experimental autoimmune encephalomyelitis (EAE), an animal model of MS while genetic deletion of IFNβ or its receptor augments clinical severity of disease. However, the complex mechanism of action of IFNβ in CNS autoimmunity has not been fully elucidated. Here, we review our current understanding of the origin, phenotype, and function of microglia and CNS immigrating macrophages in the pathogenesis of MS and EAE. In addition, we highlight the emerging roles of microglia as IFNβ-producing cells and vice versa the impact of IFNβ on microglia in CNS autoimmunity. We finally discuss recent progress in unraveling the underlying molecular mechanisms of IFNβ-mediated effects in EAE.

Genistein Loaded Nanofibers Protect Spinal Cord Tissue Following Experimental Injury in Rats

Innovative drug-delivery systems offer a unique approach to effectively provide therapeutic drug dose over the needed time to achieve better tissue protection and enhanced recovery. The hypothesis of the current study was to test the antioxidant and anti-inflammatory effects of genistein and nanofibers on the spinal cord tissue following experimental spinal cord injury (SCI). Rats were treated post SCI with genistein that is loaded on chitosan/polyvinyl alcohol (CS/PVA) nanofibers as an implantable drug-delivery system. SCI caused marked oxidative damage and inflammation, as is evident by the reduction in the super oxide dismutase (SOD) activity and the level of interleukin-10 (IL-10) in injured spinal cord tissue, as well as the significant increase in the levels of nitric oxide (NO), malondialdehyde (MDA), and tumor necrosis factor-alpha (TNF-α). Treatment of rats post SCI with genistein and CS/PVA nanofibers improved most of the above-mentioned biochemical parameters and shifted them toward the control group values. Genistein induced an increase in the activity of SOD and the level of IL-10, while causing a decrease in NO, MDA, and TNF-α in injured spinal cord tissue. Genistein and CS/PVA nanofibers provide a novel combination for treating inflammatory nervous tissue conditions, especially when combined as an implantable drug-delivery system.

NT3-chitosan enables de novo regeneration and functional recovery in monkeys after spinal cord injury

Spinal cord injury (SCI) often leads to permanent loss of motor, sensory, and autonomic functions. We have previously shown that neurotrophin3 (NT3)-loaded chitosan biodegradable material allowed for prolonged slow release of NT3 for 14 weeks under physiological conditions. Here we report that NT3-loaded chitosan, when inserted into a 1-cm gap of hemisectioned and excised adult rhesus monkey thoracic spinal cord, elicited robust axonal regeneration. Labeling of cortical motor neurons indicated motor axons in the corticospinal tract not only entered the injury site within the biomaterial but also grew across the 1-cm-long lesion area and into the distal spinal cord. Through a combination of magnetic resonance diffusion tensor imaging, functional MRI, electrophysiology, and kinematics-based quantitative walking behavioral analyses, we demonstrated that NT3-chitosan enabled robust neural regeneration accompanied by motor and sensory functional recovery. Given that monkeys and humans share similar genetics and physiology, our method is likely translatable to human SCI repair.

Axonal regeneration in zebrafish spinal cord

In the present review we discuss two interrelated events-axonal damage and repair-known to occur after spinal cord injury (SCI) in the zebrafish. Adult zebrafish are capable of regenerating axonal tracts and can restore full functionality after SCI. Unlike fish, axon regeneration in the adult mammalian central nervous system is extremely limited. As a consequence of an injury there is very little repair of disengaged axons and therefore functional deficit persists after SCI in adult mammals. In contrast, peripheral nervous system axons readily regenerate following injury and hence allow functional recovery both in mammals and fish. A better mechanistic understanding of these three scenarios could provide a more comprehensive insight into the success or failure of axonal regeneration after SCI. This review summarizes the present understanding of the cellular and molecular basis of axonal regeneration, in both the peripheral nervous system and the central nervous system, and large scale gene expression analysis is used to focus on different events during regeneration. The discovery and identification of genes involved in zebrafish spinal cord regeneration and subsequent functional experimentation will provide more insight into the endogenous mechanism of myelination and remyelination. Furthermore, precise knowledge of the mechanism underlying the extraordinary axonal regeneration process in zebrafish will also allow us to unravel the potential therapeutic strategies to be implemented for enhancing regrowth and remyelination of axons in mammals.

Transient activation of Wnt/β-catenin signaling reporter in fibrotic scar formation after compression spinal cord injury in adult mice

After traumatic spinal cord injury (SCI), a scar may form with a fibrotic core (fibrotic scar) and surrounding reactive astrocytes (glial scar) at the lesion site. The scar tissue is considered a major obstacle preventing regeneration both as a physical barrier and as a source for secretion of inhibitors of axonal regeneration. Understanding the mechanism of scar formation and how to control it may lead to effective SCI therapies. Using a compression-SCI model on adult transgenic mice, we demonstrate that the canonical Wnt/β-catenin signaling reporter TOPgal (TCF/Lef1-lacZ) positive cells appeared at the lesion site by 5 days, peaked on 7 days, and diminished by 14 days post injury. Using various representative cell lineage markers, we demonstrate that, these transiently TOPgal positive cells are a group of Fibronectin(+);GFAP(-) fibroblast-like cells in the core scar region. Some of them are proliferative. These results indicate that Wnt/β-catenin signaling may play a key role in fibrotic scar formation after traumatic spinal cord injury.

Cell therapy for spinal cord injury with olfactory ensheathing glia cells (OECs)

The prospects of achieving regeneration in the central nervous system (CNS) have changed, as most recent findings indicate that several species, including humans, can produce neurons in adulthood. Studies targeting this property may be considered as potential therapeutic strategies to respond to injury or the effects of demyelinating diseases in the CNS. While CNS trauma may interrupt the axonal tracts that connect neurons with their targets, some neurons remain alive, as seen in optic nerve and spinal cord (SC) injuries (SCIs). The devastating consequences of SCIs are due to the immediate and significant disruption of the ascending and descending spinal pathways, which result in varying degrees of motor and sensory impairment. Recent therapeutic studies for SCI have focused on cell transplantation in animal models, using cells capable of inducing axon regeneration like Schwann cells (SchCs), astrocytes, genetically modified fibroblasts and olfactory ensheathing glia cells (OECs). Nevertheless, and despite the improvements in such cell-based therapeutic strategies, there is still little information regarding the mechanisms underlying the success of transplantation and regarding any secondary effects. Therefore, further studies are needed to clarify these issues. In this review, we highlight the properties of OECs that make them suitable to achieve neuroplasticity/neuroregeneration in SCI. OECs can interact with the glial scar, stimulate angiogenesis, axon outgrowth and remyelination, improving functional outcomes following lesion. Furthermore, we present evidence of the utility of cell therapy with OECs to treat SCI, both from animal models and clinical studies performed on SCI patients, providing promising results for future treatments.

Nogo receptor expression in microglia/macrophages during experimental autoimmune encephalomyelitis progression

Myelin-associated inhibitory factors within the central nervous system (CNS) are considered to be one of the main obstacles for axonal regeneration following disease or injury. The nogo receptor 1 (NgR1) has been well documented to play a key role in limiting axonal regrowth in the injured and diseased mammalian CNS. However, the role of nogo receptor in immune cell activation during CNS inflammation is yet to be mechanistically elucidated. Microglia/macrophages are immune cells that are regarded as pathogenic contributors to inflammatory demyelinating lesions in multiple sclerosis (MS). In this study, the animal model of MS, experimental autoimmune encephalomyelitis (EAE) was induced in ngr1^+/+ and ngr1^–/– female mice following injection with the myelin oligodendrocyte glycoprotein (MOG_35–55) peptide. A fate-map analysis of microglia/macrophages was performed throughout spinal cord sections of EAE-induced mice at clinical scores of 0, 1, 2 and 3, respectively (increasing locomotor disability) from both genotypes, using the CD11b and Iba1 cell markers. Western immunoblotting using lysates from isolated spinal cord microglia/macrophages, along with immunohistochemistry and flow cytometric analysis, was performed to demonstrate the expression of nogo receptor and its two homologs during EAE progression. Myelin protein engulfment during EAE progression in ngr1^+/+ and ngr1^–/– mice was demonstrated by western immunblotting of lysates from isolated spinal cord microglia/macrophages, detecting levels of Nogo-A and MOG. The numbers of M1 and M2 microglia/macrophage phenotypes present in the spinal cords of EAE-induced ngr1^+/+ and ngr1^–/– mice, were assessed by flow cytometric analysis using CD38 and Erg-2 markers. A significant difference in microglia/macrophage numbers between ngr1^+/+ and ngr1^–/– mice was identified during the progression of the clinical symptoms of EAE, in the white versus gray matter regions of the spinal cord. This difference was unrelated to the expression of NgR on these macrophage/microglial cells. We have identified that as EAE progresses, the phagocytic activity of microglia/macrophages with myelin debris, in ngr1^–/– mice, was enhanced. Moreover, we show a modulation from a predominant M1-pathogenic to the M2-neurotrophic cell phenotype in the ngr1^–/– mice during EAE progression. These findings suggest that CNS-specific macrophages and microglia of ngr1^–/– mice may exhibit an enhanced capacity to clear inhibitory molecules that are sequestered in inflammatory lesions.

Micropuncture and pressure assisted Schwann cell seeding of nerve allograft

BACKGROUND

Tissue processing to create immunotolerant nerve allograft removes neurosupportive cells. Few strategies have been described for implanting new cells into the graft to support axonal regeneration.

NEW METHOD

Micropuncture of the nerve allograft surface combined with immersion into a pressurized cell-rich solution to potentiate the introduction of viable Schwann cells (SC) into processed nerve allograft. Allografts were used to repair rodent sciatic nerve defects. At 3, 7, and 21days, grafts were harvested, stained for SCs, and analyzed using total cross sectional area (CSA) occupied by SCs to quantify SC presence.

RESULTS

At days 3 and 7, SC CSA was significantly greater for the injection group compared to all other groups. At day 21, SC CSA for the injection group (0.2252%±0.2730) was significantly greater compared to following groups: pressurized-punctured (0.0653%±0.0934), nonpressurized-nonpunctured (0.0607%±0.0709), punctured-control (0.0246%±0.0398), and nonpunctured-control (0.0126%±0.0151). A significant decrease in percent CSA occupied by SCs from day 3 to day 21 was noted in nonpressurized-punctured group (p=0.0106), pressurized-nonpunctured group (p=0.0477), and injection group (p=0.0010).

COMPARISON WITH EXISTING METHOD(S)

Most studies have used small caliber hypodermic needles to inject the cells into grafts.

CONCLUSIONS

Despite a presumed decrease in cell viability over the three weeks of the study, the large initial inoculum achieved by injection technique results in higher levels of final SC seeding in acellular nerve allograft compared with bathing techniques with or without micropuncture or pressurization.

Combinatorial Therapies After Spinal Cord Injury: How Can Biomaterials Help?

Traumatic spinal cord injury (SCI) results in an immediate loss of motor and sensory function below the injury site and is associated with a poor prognosis. The inhibitory environment that develops in response to the injury is mainly due to local expression of inhibitory factors, scarring and the formation of cystic cavitations, all of which limit the regenerative capacity of endogenous or transplanted cells. Strategies that demonstrate promising results induce a change in the microenvironment at- and around the lesion site to promote endogenous cell repair, including axonal regeneration or the integration of transplanted cells. To date, many of these strategies target only a single aspect of SCI; however, the multifaceted nature of SCI suggests that combinatorial strategies will likely be more effective. Biomaterials are a key component of combinatorial strategies, as they have the potential to deliver drugs locally over a prolonged period of time and aid in cell survival, integration and differentiation. Here we summarize the advantages and limitations of widely used strategies to promote recovery after injury and highlight recent research where biomaterials aided combinatorial strategies to overcome some of the barriers of spinal cord regeneration.

E6020, a synthetic TLR4 agonist, accelerates myelin debris clearance, Schwann cell infiltration, and remyelination in the rat spinal cord

Oligodendrocyte progenitor cells (OPCs) are present throughout the adult brain and spinal cord and can replace oligodendrocytes lost to injury, aging, or disease. Their differentiation, however, is inhibited by myelin debris, making clearance of this debris an important step for cellular repair following demyelination. In models of peripheral nerve injury, TLR4 activation by lipopolysaccharide (LPS) promotes macrophage phagocytosis of debris. Here we tested whether the novel synthetic TLR4 agonist E6020, a Lipid A mimetic, promotes myelin debris clearance and remyelination in spinal cord white matter following lysolecithin-induced demyelination. In vitro, E6020 induced TLR4-dependent cytokine expression (TNFα, IL1β, IL-6) and NF-κB signaling, albeit at ∼10-fold reduced potency compared to LPS. Microinjection of E6020 into the intact rat spinal cord gray/white matter border induced macrophage activation, OPC proliferation, and robust oligodendrogenesis, similar to what we described previously using an intraspinal LPS microinjection model. Finally, a single co-injection of E6020 with lysolecithin into spinal cord white matter increased axon sparing, accelerated myelin debris clearance, enhanced Schwann cell infiltration into demyelinated lesions, and increased the number of remyelinated axons. In vitro assays confirmed that direct stimulation of macrophages by E6020 stimulates myelin phagocytosis. These data implicate TLR4 signaling in promoting repair after CNS demyelination, likely by stimulating phagocytic activity of macrophages, sparing axons, recruiting myelinating cells, and promoting remyelination. This work furthers our understanding of immune-myelin interactions and identifies a novel synthetic TLR4 agonist as a potential therapeutic avenue for white matter demyelinating conditions such as spinal cord injury and multiple sclerosis.

Descending propriospinal neurons mediate restoration of locomotor function following spinal cord injury

Following spinal cord injury (SCI) in the lamprey, there is virtually complete recovery of locomotion within a few weeks, but interestingly, axonal regeneration of reticulospinal (RS) neurons is mostly limited to short distances caudal to the injury site. To explain this situation, we hypothesize that descending propriospinal (PS) neurons relay descending drive from RS neurons to indirectly activate spinal central pattern generators (CPGs). In the present study, the contributions of PS neurons to locomotor recovery were tested in the lamprey following SCI. First, long RS neuron projections were interrupted by staggered spinal hemitransections on the right side at 10% body length (BL; normalized from the tip of the oral hood) and on the left side at 30% BL. For acute recovery conditions (≤1 wk) and before axonal regeneration, swimming muscle burst activity was relatively normal, but with some deficits in coordination. Second, lampreys received two spaced complete spinal transections, one at 10% BL and one at 30% BL, to interrupt long-axon RS neuron projections. At short recovery times (3-5 wk), RS and PS neurons will have regenerated their axons for short distances and potentially established a polysynaptic descending command pathway. At these short recovery times, swimming muscle burst activity had only minor coordination deficits. A computer model that incorporated either of the two spinal lesions could mimic many aspects of the experimental data. In conclusion, descending PS neurons are a viable mechanism for indirect activation of spinal locomotor CPGs, although there can be coordination deficits of locomotor activity.

NEW & NOTEWORTHY

In the lamprey following spinal lesion-mediated interruption of long axonal projections of reticulospinal (RS) neurons, sensory stimulation still elicited relatively normal locomotor muscle burst activity, but with some coordination deficits. Computer models incorporating the spinal lesions could mimic many aspects of the experimental results. Thus, after disruption of long-axon projections from RS neurons in the lamprey, descending propriospinal (PS) neurons appear to be a viable compensatory mechanism for indirect activation of spinal locomotor networks.

Jisuikang, a Chinese herbal formula, increases neurotrophic factor expression and promotes the recovery of neurological function after spinal cord injury

The Chinese medicine compound, Jisuikang, can promote recovery of neurological function by inhibiting lipid peroxidation, scavenging oxygen free radicals, and effectively improving the local microenvironment after spinal cord injury. However, the mechanism remains unclear. Thus, we established a rat model of acute spinal cord injury using a modified version of Allen's method. Jisuikang (50, 25, and 12.5 g/kg/d) and prednisolone were administered 30 minutes after anesthesia. Basso, Beattie, and Bresnahan locomotor scale scores and the oblique board test showed improved motor function recovery in the prednisone group and moderate-dose Jisuikang group compared with the other groups at 3-7 days post-injury. The rats in the moderate-dose Jisuikang group recovered best at 14 days post-injury. Hematoxylin-eosin staining and transmission electron microscopy showed that the survival rate of neurons in treatment groups increased after 3-7 days of administration. Further, the structure of neurons and glial cells was more distinct, especially in prednisolone and moderate-dose Jisuikang groups. Western blot assay and immunohistochemistry showed that expression of brain-derived neurotrophic factor (BDNF) in injured segments was maintained at a high level after 7-14 days of treatment. In contrast, expression of nerve growth factor (NGF) was down-regulated at 7 days after spinal cord injury. Real-time fluorescence quantitative polymerase chain reaction showed that expression of BDNF and NGF mRNA was induced in injured segments by prednisolone and Jisuikang. At 3-7 days after injury, the effect of prednisolone was greater, while 14 days after injury, the effect of moderate-dose Jisuikang was greater. These results confirm that Jisuikang can upregulate BDNF and NGF expression for a prolonged period after spinal cord injury and promote repair of acute spinal cord injury, with its effect being similar to prednisolone.

Nucleolin inhibitor GroA triggers reduction in epidermal growth factor receptor activation: Pharmacological implication for glial scarring after spinal cord injury

Glial scarring, formed by reactive astrocytes, is one of the major impediments for regeneration after spinal cord injury (SCI). Reactive astrocytes become hypertrophic, proliferate and secrete chondroitin sulphate proteoglycans into the extracellular matrix (ECM). Many studies have demonstrated that epidermal growth factor receptors (EGFR) can mediate astrocyte reactivity after neurotrauma. Previously we showed that there is crosstalk between nucleolin and EGFR that leads to increased EGFR activation followed by increased cell proliferation. Treatment with the nucleolin inhibitor GroA (AS1411) prevented these effects in vitro and in vivo. In this study, we hypothesized that similar interactions may mediate astrogliosis after SCI. Our results demonstrate that nucleolin and EGFR interaction may play a pivotal role in mediating astrocyte proliferation and reactivity after SCI. Moreover, we demonstrate that treatment with GroA reduces EGFR activation, astrocyte proliferation and chondroitin sulphate proteoglycans secretion, therefore promoting axonal regeneration and sprouting into the lesion site. Our results identify, for the first time, a role for the interaction between nucleolin and EGFR in astrocytes after SCI, indicating that nucleolin inhibitor GroA may be used as a novel treatment after neurotrauma. A major barrier for axonal regeneration after spinal cord injury is glial scar created by reactive and proliferating astrocytes. EGFR mediate astrocyte reactivity. We showed that inhibition of nucleolin by GroA, reduces EGFR activation, which results in attenuation of astrocyte reactivity and proliferation in vivo and in vitro. EGFR, epidermal growth factor receptor.

Tumor necrosis factor-α antagonist suppresses local inflammatory reaction and facilitates olfactory nerve recovery following injury

OBJECTIVE

Olfactory dysfunction is a common finding in head trauma due to injury to the olfactory nerve. We previously reported that anti-inflammatory treatment with steroids improves recovery outcome in olfactory nerve injury models. Clinically, however, steroid administration is not recommended in the acute phase of head injury cases because of concerns regarding its side effects. Tumor necrosis factor (TNF-α) is known to play a key role in inflammatory response to injury. The present study examines if the inhibition of TNF-α can facilitate functional recovery in the olfactory system following injury.

MATERIALS AND METHODS

Olfactory nerve transection (NTx) was performed in olfactory marker protein (OMP-tau-lacZ) mice to establish injury models. We measured TNF-α gene expression in the olfactory bulb using semi-quantitative and real time polymerase chain reaction (PCR) assays and found that they increase within hours after NTx injury. A TNF-α antagonist (etanercept) was intraperitoneally injected immediately after the NTx and histological assessment of recovery within the olfactory bulb was performed at 5-70 days. X-gal staining labeled OMP in the degenerating and regenerating olfactory nerve fibers, and immunohistochemical staining detected the presence of reactive astrocytes and macrophages/microglia.

RESULTS

Etanercept-injected mice showed significantly smaller areas of injury-associated tissue, fewer astrocytes and macrophages/microglia, and an increase in regenerating nerve fibers. Olfactory function assessments using both an olfactory avoidance behavioral test and evoked potential recordings showed improved functional recovery in etanercept-injected animals.

CONCLUSION

These findings suggest that inhibition of TNF-α could provide a new therapeutic strategy for the treatment of olfactory dysfunction following head injuries.

Canadian Association of Neuroscience Review: Axonal Regeneration in the Peripheral and Central Nervous Systems – Current Issues and Advances

Injured nerves regenerate their axons in the peripheral (PNS) but not the central nervous system (CNS). The contrasting capacities have been attributed to the growth permissive Schwann cells in the PNS and the growth inhibitory environment of the oligodendrocytes in the CNS. In the current review, we first contrast the robust regenerative response of injured PNS neurons with the weak response of the CNS neurons, and the capacity of Schwann cells and not the oligodendrocytes to support axonal regeneration. We then consider the factors that limit axonal regeneration in both the PNS and CNS. Limiting factors in the PNS include slow regeneration of axons across the injury site, progressive decline in the regenerative capacity of axotomized neurons (chronic axotomy) and progressive failure of denervated Schwann cells to support axonal regeneration (chronic denervation). In the CNS on the other hand, it is the poor regenerative response of neurons, the inhibitory proteins that are expressed by oligodendrocytes and act via a common receptor on CNS neurons, and the formation of the glial scar that prevent axonal regeneration in the CNS. Strategies to overcome these limitations in the PNS are considered in detail and contrasted with strategies in the CNS.

Virus-Induced Demyelination: The Case for Virus(es) in Multiple Sclerosis

Multiple Sclerosis (MS) is the most common demyelinating disease of man with over 400,000 cases in the United States and over 2.5 million cases worldwide. There are over 64,000 citations in Pubmed dating back as far as 1887. Much has been learned over the past 129 years with a recent burst in therapeutic options (mostly anti-inflammatory) with newer medications in development that are neuroprotective and/or neuroreparative. However, with all these advancements the cause of MS remains elusive. There is a clear interplay of genetic, immunologic, and environmental factors that influences both the development and progression of this disorder. This chapter will give a brief overview of the history and pathogenesis of MS with attention to how host immune responses in genetically susceptible individuals contribute to the MS disease process. In addition, we will explore the role of infectious agents in MS as potential “triggers” of disease. Models of virus-induced demyelination will be discussed, with an emphasis on the recent interest in human herpesviruses and the role they may play in MS disease pathogenesis. Although we remain circumspect as to the role of any microbial pathogen in MS, we suggest that only through well-controlled serological, cellular immune, molecular, and animal studies we will be able to identify candidate agents. Ultimately, clinical interventional trials that either target a specific pathogen or class of pathogens will be required to make definitive links between the suspected agent and MS.

IFNβ secreted by microglia mediates clearance of myelin debris in CNS autoimmunity

Introduction

Multiple sclerosis (MS) is a chronic demyelinating disorder of the central nervous system (CNS) leading to progressive neurological disability. Interferon β (IFNβ) represents a standard treatment for relapsing-remitting MS and exogenous administration of IFNβ exhibits protective effects in experimentally induced CNS autoimmunity. Also, genetic deletion of IFNβ in mice leads to an aggravation of disease symptoms in the MS model of experimental autoimmune encephalomyelitis (EAE). However, neither the underlying mechanisms mediating the beneficial effects nor the cellular source of IFNβ have been fully elucidated.

Results

In this report, a subpopulation of activated microglia was identified as the major producers of IFNβ in the CNS at the peak of EAE using an IFNβ-fluorescence reporter mouse model. These IFNβ expressing microglia specifically localized to active CNS lesions and were associated with myelin debris in demyelinated cerebellar organotypic slice cultures (OSCs). In response to IFNβ microglia showed an enhanced capacity to phagocytose myelin in vitro and up-regulated the expression of phagocytosis-associated genes. IFNβ treatment was further sufficient to stimulate association of microglia with myelin debris in OSCs. Moreover, IFNβ-producing microglia mediated an enhanced removal of myelin debris when co-transplanted onto demyelinated OSCs as compared to IFNβ non-producing microglia.

Conclusions

These data identify activated microglia as the major producers of protective IFNβ at the peak of EAE and as orchestrators of IFNβ-induced clearance of myelin debris.

Electronic supplementary material

The online version of this article (doi:10.1186/s40478-015-0192-4) contains supplementary material, which is available to authorized users.

The role of the JAK-STAT pathway in neural stem cells, neural progenitor cells and reactive astrocytes after spinal cord injury

Patients with spinal cord injuries can develop severe neurological damage and dysfunction, which is not only induced by primary but also by secondary injuries. As an evolutionarily conserved pathway of eukaryotes, the JAK-STAT pathway is associated with cell growth, survival, development and differentiation; activation of the JAK-STAT pathway has been previously reported in central nervous system injury. The JAK-STAT pathway is directly associated with neurogenesis and glia scar formation in the injury region. Following injury of the axon, the overexpression and activation of STAT3 is exhibited specifically in protecting neurons. To investigate the role of the JAK-STAT pathway in neuroprotection, we summarized the effect of JAK-STAT pathway in the following three sections: Firstly, the modulation of JAK-STAT pathway in proliferation and differentiation of neural stem cells and neural progenitor cells is discussed; secondly, the time-dependent effect of JAK-STAT pathway in reactive astrocytes to reveal their capability of neuroprotection is revealed and lastly, we focus on how the astrocyte-secretory polypeptides (astrocyte-derived cytokines and trophic factors) accomplish neuroprotection via the JAK-STAT pathway.

MicroRNA-145 as one negative regulator of astrogliosis

Astrogliosis occurs at the lesion site within days to weeks after spinal cord injury (SCI) and involves the proliferation and hypertrophy of astrocytes, leading to glia scar formation. Changes in gene expression by deregulated microRNAs (miRNAs) are involved in the process of central nervous system neurodegeneration. Here, we report that mir-145, a miRNA enriched in rat spinal neurons and astrocytes, was downregulated at 1 week and 1 month after SCI. Our in vitro studies using astrocytes prepared from neonatal spinal cord tissues indicated that potent inflammagen lipopolysaccharide downregulated mir-145 expression in astrocytes, suggesting that SCI-triggered inflammatory signaling pathways could play the inhibitory role in astrocytic mir-145 expression. To induce overexpression of mir-145 in astrocytes at the spinal cord lesion site, we developed a lentivirus-mediated pre-miRNA delivery system using the promoter of glial fibrillary acidic protein (GFAP), an astrocyte-specific intermediate filament. The results indicated that astrocyte-specific overexpression of mir-145 reduced astrocytic cell density at the lesion border of the injured spinal cord. In parallel, overexpression of mir-145 reduced the size of astrocytes and the number of related cell processes, as well as cell proliferation and migration. Through a luciferase reporter system, we found that GFAP and c-myc were the two potential targets of mir-145 in astrocytes. Together, the findings demonstrate the novel role of mir-145 in the regulation of astrocytic dynamics, and reveal that the downregulation of mir-145 in astrocytes is a critical factor inducing astrogliosis after SCI. GLIA 2015;63:194-205.

Mst3b promotes spinal cord neuronal regeneration by promoting growth cone branching out in spinal cord injury rats

Spinal cord injury is a severe clinical problem, and research searching activity molecular that can promote spinal cord injury repairing is very prevalent. Mst3b can promote repair of damaged peripheral nerves and the optic nerve, but has been rarely reported in spinal cord injury research. Through detecting its expression in different periods of injured spinal cord, we found that the expression of Mst3b was significantly upregulated in injured spinal cord neurons. Increasing Mst3b expression using adenovirus in vivo and in vitro promoted axonal regeneration of spinal cord neurons, which led to behavioral and electrophysiological improvement. Downregulation of Mst3b level had the adverse effects. Increasing Mst3b expression in PC12 cells resulted in an elevation of P42/44(MAPK) and LIMK/Cofilin activation. These results identified Mst3b as a powerful regulator for promoting spinal cord injury recovery through the P42/44(MAPK) and LIMK/Cofilin signaling pathways.

Cytokine concentrations in the cerebrospinal fluid of great danes with cervical spondylomyelopathy

Background

Chronic inflammation is involved in the pathogenesis of human cervical spondylotic myelopathy and could also play a role in cervical spondylomyelopathy (CSM) in dogs.

Hypothesis/Objectives

That cerebrospinal fluid (CSF) cytokine concentrations would differ between clinically normal (control) and CSM‐affected Great Danes (GDs), with affected GDs showing higher levels of inflammatory cytokines, such as interleukin (IL)‐6 and monocyte chemoattractant protein‐1/chemokine ligand 2 (MCP‐1/CCL2).

Animals

Client‐owned GDs: 15 control, 15 CSM‐affected.

Methods

Prospective study. Dogs underwent cervical vertebral column magnetic resonance imaging and collection of CSF from the cerebellomedullary cistern. Cytokine concentrations were measured using a commercially available canine multiplex immunoassay. Cytokine concentrations were compared between groups. Associations with the administration of anti‐inflammatory medications, disease duration and severity, severity of spinal cord (SC) compression, and SC signal changes were investigated in affected GDs.

Results

Affected GDs had significantly lower MCP‐1/CCL2 (mean 138.03 pg/mL, 95% confidence interval [CI] = 114.85–161.20) than control GDs (212.89 pg/mL, 95% CI = 165.68–260.11, P = .028). In affected GDs, MCP‐1/CCL2 concentrations correlated inversely with the severity of SC compression. There were no associations with administration of anti‐inflammatory medications, disease duration, or disease severity. IL‐6 concentrations were significantly higher (2.20 pg/mL, 95% CI = 1.92–2.47, P < .001) in GDs with SC signal changes.

Conclusions and Clinical Importance

Lower MCP‐1/CCL2 in CSM‐affected GDs might compromise clearance of axonal and myelin debris, delay axon regeneration, and affect recovery. Higher IL‐6 in CSM‐affected GDs with SC signal changes suggests more severe inflammation in this group.

Can we switch microglia's phenotype to foster neuroprotection? Focus on multiple sclerosis

Microglia cells, the resident innate immune cells in the brain, are highly active, extending and retracting highly motile processes through which they continuously survey their microenvironment for 'danger signals' and interact dynamically with surrounding cells. Upon sensing changes in their central nervous system microenvironment, microglia become activated, undergoing morphological and functional changes. Microglia activation is not an 'all-or-none' process, but rather a continuum depending on encountered stimuli, which is expressed through a spectrum of molecular and functional phenotypes ranging from so-called 'classically activated', with a highly pro-inflammatory profile, to 'alternatively activated' associated with a beneficial, less inflammatory, neuroprotective profile. Microglia activation has been demonstrated in most neurological diseases of diverse aetiology and has been implicated as a contributor to neurodegeneration. The possibility to promote microglia's neuroprotective phenotype has therefore become a therapeutic goal. We have focused our discussion on the role of microglia in multiple sclerosis, a prototype of inflammatory, demyelinating, neurodegenerative disease, and on the effect of currently approved or on-trial anti-inflammatory therapeutic strategies that might mediate neuroprotection at least in part through their effect on microglia by modifying their behaviour via a switch of their functional phenotype from a detrimental to a protective one. In addition to pharmaceutical approaches, such as treatment with glatiramer acetate, interferon-β, fingolimod or dimethyl fumarate, we address the alternative therapeutic approach of treatment with mesenchymal stem cells and their potential role in neuroprotection through their 'calming' effect on microglia.

Brief Report: Astrogliosis Promotes Functional Recovery of Completely Transected Spinal Cord Following Transplantation of hESC-Derived Oligodendrocyte and Motoneuron Progenitors

Spinal cord injury results in neural loss and consequently motor and sensory impairment below the injury. Reactive astrocytes contribute to formation of glial scar, thus impeding axonal regeneration, through secretion of extracellular matrix molecules, chondroitin sulfate proteoglycans (CSPGs). In this study, we analyze lesion site tissue to reveal the possible mechanism underlying the functional recovery after cell transplantation of human embryonic stem cell (hESC)-derived oligodendrocyte progenitor cell (OPC) and motoneuron progenitors (MP) and propose that transplanted cells increase astrogliosis through the regenerative signaling pathways activated in the host tissue that may crucial for restoring locomotor ability. We show that the transplantation of hESC-derived OPC and MP promotes astrogliosis, through activation of Jagged1-dependent Notch and Jak/STAT signaling that support axonal survival. The transplanted cells in synergism with reactive astrocytes create permissive environment in which the expression of detrimental genes (Cspg, Tenascins, and genes involved in SLIT/ROBO signaling) was significantly decreased while expression of beneficial ones (Laminins and Fibronectin) was increased. According to our data, this mechanism is activated in all transplantation groups independently of the level of locomotor recovery. These results indicate that modifying the beneficial function of reactive astrocytes could be a feasible therapeutic strategy for spinal cord injury in future. Stem Cells  2014;32:594–599

Central canal ependymal cells proliferate extensively in response to traumatic spinal cord injury but not demyelinating lesions

The adult mammalian spinal cord has limited regenerative capacity in settings such as spinal cord injury (SCI) and multiple sclerosis (MS). Recent studies have revealed that ependymal cells lining the central canal possess latent neural stem cell potential, undergoing proliferation and multi-lineage differentiation following experimental SCI. To determine whether reactive ependymal cells are a realistic endogenous cell population to target in order to promote spinal cord repair, we assessed the spatiotemporal dynamics of ependymal cell proliferation for up to 35 days in three models of spinal pathologies: contusion SCI using the Infinite Horizon impactor, focal demyelination by intraspinal injection of lysophosphatidylcholine (LPC), and autoimmune-mediated multi-focal demyelination using the active experimental autoimmune encephalomyelitis (EAE) model of MS. Contusion SCI at the T9-10 thoracic level stimulated a robust, long-lasting and long-distance wave of ependymal proliferation that peaked at 3 days in the lesion segment, 14 days in the rostral segment, and was still detectable at the cervical level, where it peaked at 21 days. This proliferative wave was suppressed distal to the contusion. Unlike SCI, neither chemical- nor autoimmune-mediated demyelination triggered ependymal cell proliferation at any time point, despite the occurrence of demyelination (LPC and EAE), remyelination (LPC) and significant locomotor defects (EAE). Thus, traumatic SCI induces widespread and enduring activation of reactive ependymal cells, identifying them as a robust cell population to target for therapeutic manipulation after contusion; conversely, neither demyelination, remyelination nor autoimmunity appears sufficient to trigger proliferation of quiescent ependymal cells in models of MS-like demyelinating diseases.

Effect of calcitonin gene-related peptide on the neurogenesis of rat adipose-derived stem cells in vitro

Calcitonin gene-related peptide (CGRP) promotes neuron recruitment and neurogenic activity. However, no evidence suggests that CGRP affects the ability of stem cells to differentiate toward neurogenesis. In this study, we genetically modified rat adipose-derived stem cells (ADSCs) with the CGRP gene (CGRP-ADSCs) and subsequently cultured in complete neural-induced medium. The formation of neurospheres, cellular morphology, and proliferative capacity of ADSCs were observed. In addition, the expression of the anti-apoptotic protein Bcl-2 and special markers of neural cells, such as Nestin, MAP2, RIP and GFAP, were evaluated using Western blot and immunocytochemistry analysis. The CGRP-ADSCs displayed a greater proliferation than un-transduced (ADSCs) and Vector-transduced (Vector-ADSCs) ADSCs (p<0.05), and lower rates of apoptosis, associated with the incremental expression of Bcl-2, were also observed for CGRP-ADSCs. Moreover, upon neural induction, CGRP-ADSCs formed markedly more and larger neurospheres and showed round cell bodies with more branching extensions contacted with neighboring cells widely. Furthermore, the expression levels of Nestin, MAP2, and RIP in CGRP-ADSCs were markedly increased, resulting in higher levels than the other groups (p<0.05); however, GFAP was distinctly undetectable until day 7, when slight GFAP expression was detected among all groups. Wnt signals, primarily Wnt 3a, Wnt 5a and β-catenin, regulate the neural differentiation of ADSCs, and CGRP gene expression apparently depends on canonical Wnt signals to promote the neurogenesis of ADSCs. Consequently, ADSCs genetically modified with CGRP exhibit stronger potential for differentiation and neurogenesis in vitro, potentially reflecting the usefulness of ADSCs as seed cells in therapeutic strategies for spinal cord injury.

Demyelination in multiple sclerosis

This review, focused on demyelination in multiple sclerosis, is divided in two parts. The first part addresses the many and not exclusive mechanisms leading to demyelination in the central nervous system. Although the hypothesis that a primary oligodendrocyte or myelin injury induces a secondary immune response in the central nervous system is still a matter of debate, most recent advances underline the influence of a primary immune response against myelin antigen(s), with a diversity of potential targets. Whereas multiple sclerosis was long considered as a T cell-mediated disease, the role of B lymphocytes is now increasingly recognized, and the influence of antibodies on tissue damage actively investigated. The second part of the review describes the axonal consequences of demyelination. Segmental demyelination results in conduction block or slowing of conduction through adaptative responses, notably related to modifications in the distribution of voltage gated sodium channels along the denuded axon. If demyelination persists, these changes, as well as the loss of trophic and metabolic support, will lead to irreversible axonal damage and loss. In this respect, favouring early myelin repair, during a window of time when axonal damage is still reversible, might pave the way for neuroprotection.

Schwann cells differentiated from adipose‑derived stem cells for the treatment of brain contusion

Rapid development of tissue engineering techniques has led to the possibility of treating central nervous injuries with Schwann cells (SCs). However, certain characteristics of SCs, such as a low proliferation ability, greatly restrict their use. The aim of the present study was to investigate whether SCs differentiated from adipose‑derived stem cells (ADSC‑SCs) could used to promote functional recovery in brain contusion in rat. ADSCs were isolated and expanded from the groin of Sprague‑Dawley rats and differentiated into SCs. The ADSC‑SCs were transplanted into the contused rat brain and the locomotor function of the rats was assessed. Significant locomotor function recovery was observed in hemiparalyzed rats treated with ADSCs‑SCs. In conclusion, transplantation of ADSC‑SCs significantly promoted functional recovery following brain contusion.

From basics to clinical: a comprehensive review on spinal cord injury

Spinal cord injury (SCI) is a devastating neurological disorder that affects thousands of individuals each year. Over the past decades an enormous progress has been made in our understanding of the molecular and cellular events generated by SCI, providing insights into crucial mechanisms that contribute to tissue damage and regenerative failure of injured neurons. Current treatment options for SCI include the use of high dose methylprednisolone, surgical interventions to stabilize and decompress the spinal cord, and rehabilitative care. Nonetheless, SCI is still a harmful condition for which there is yet no cure. Cellular, molecular, rehabilitative training and combinatorial therapies have shown promising results in animal models. Nevertheless, work remains to be done to ascertain whether any of these therapies can safely improve patient's condition after human SCI. This review provides an extensive overview of SCI research, as well as its clinical component. It starts covering areas from physiology and anatomy of the spinal cord, neuropathology of the SCI, current clinical options, neuronal plasticity after SCI, animal models and techniques to assess recovery, focusing the subsequent discussion on a variety of promising neuroprotective, cell-based and combinatorial therapeutic approaches that have recently moved, or are close, to clinical testing.

ADAMTS1, ADAMTS5, ADAMTS9 and aggrecanase-generated proteoglycan fragments are induced following spinal cord injury in mouse

ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) proteinases are involved in a variety of biological processes such as angiogenesis, cancer and arthritis. ADAMTSs appears to be responsible for the cleavage of proteoglycans in several tissues including brain and cartilage. Chondroitin sulfate proteoglycans (CSPGs) maintains the integrity of the brain extracellular matrix and major inhibitory contributors for glial scar and neural plasticity. The activity of aggrecanases in the central nervous system (CNS) has been reported. ADAMTSs are an enzyme degrading CSPGs in the brain. However, there is a little knowledge regarding ADAMTSs in the CNS. We investigated the expression levels of ADAMTSs mRNAs by RT-PCR after spinal cord injury in mouse. Transcripts encoding 4 of the 19 known ADAMTSs were evaluated in the mouse spinal cord following injury. ADAMTS1, -5 and -9 expression levels were found to be upregulated. No change was observed in ADAMTS4 expression. By means of immunohistochemistry, ADAMTSs were detected in the astrocytes implying its cellular source in SCI. Western blot analyses indicated that aggrecanase-generated proteoglycan fragments are produced after SCI.