Harmful and beneficial effects of inflammation after spinal cord injury: potential therapeutic implications

Surgical intervention combined with weight-bearing walking training promotes recovery in patients with chronic spinal cord injury: a randomized controlled study

JOURNAL/nrgr/04.03/01300535-202412000-00032/figure1/v/2024-04-08T165401Z/r/image-tiff For patients with chronic spinal cord injury, the conventional treatment is rehabilitation and treatment of spinal cord injury complications such as urinary tract infection, pressure sores, osteoporosis, and deep vein thrombosis. Surgery is rarely performed on spinal cord injury in the chronic phase, and few treatments have been proven effective in chronic spinal cord injury patients. Development of effective therapies for chronic spinal cord injury patients is needed. We conducted a randomized controlled clinical trial in patients with chronic complete thoracic spinal cord injury to compare intensive rehabilitation (weight-bearing walking training) alone with surgical intervention plus intensive rehabilitation. This clinical trial was registered at ClinicalTrials.gov (NCT02663310). The goal of surgical intervention was spinal cord detethering, restoration of cerebrospinal fluid flow, and elimination of residual spinal cord compression. We found that surgical intervention plus weight-bearing walking training was associated with a higher incidence of American Spinal Injury Association Impairment Scale improvement, reduced spasticity, and more rapid bowel and bladder functional recovery than weight-bearing walking training alone. Overall, the surgical procedures and intensive rehabilitation were safe. American Spinal Injury Association Impairment Scale improvement was more common in T7-T11 injuries than in T2-T6 injuries. Surgery combined with rehabilitation appears to have a role in treatment of chronic spinal cord injury patients.

PTPRO inhibition ameliorates spinal cord injury through shifting microglial M1/M2 polarization via the NF-κB/STAT6 signaling pathway

Spinal cord injury (SCI) induces severe neuroinflammation, and subsequently neurological dysfunction. Activated microglia are critical for modulation of neuroinflammation. Protein tyrosine phosphatase receptor type O (PTPRO), a member of protein tyrosine phosphatases (PTPs), exerts a pro-inflammatory role in multiple human diseases; however, its role in SCI remains unclarified. Here, a T7 spinal cord compression injury model was established in Sprague-Dawley (SD) rats, and PTPRO expression was upregulated in injured spinal cord and microglia after SCI. Microglia M1 and M2 polarization in vitro were induced using LPS/IFN-γ and IL-4, respectively. PTPRO expression was elevated in M1-polarized microglia, and PTPRO downregulation mediated by PTPRO shRNA (shPTPRO) decreased CD86+ cell proportion, iNOS, TNF-α, IL-1β, and IL-6 levels, and p65 phosphorylation. PTPRO was downregulated in M2 microglia, and PTPRO upregulation by PTPRO overexpression plasmid (OE-PTPRO) reduced CD206+ cell percentage, Arg-1, IL-10, and TGF-β1 levels and STAT6 phosphorylation. Mechanistically, the transcription factor SOX4 elevated PTPRO expression and its promoter activity. SOX4 overexpression enhanced M1 polarization and p65 phosphorylation, while its knockdown promoted M2 polarization and STAT6 phosphorylation. PTPRO might mediate the function of SOX4 in BV2 microglia polarization. Furthermore, lentivirus-mediated downregulation of PTPRO following SCI improved locomotor functional recovery, demonstrated by elevated BBB scores, incline angle, consistent hindlimb coordination, and reduced lesion area and neuronal apoptosis. PTPRO downregulation promoted microglia M2 polarization, NF-κB inactivation and STAT6 activation after injury. In conclusion, PTPRO inhibition improves spinal cord injury through facilitating M2 microglia polarization via the NF-κB/STAT6 signaling pathway, which is probably controlled by SOX4.

Promising application of pulsed electromagnetic fields on tissue repair and regeneration

Tissue repair and regeneration is a vital biological process in organisms, which is influenced by various internal mechanisms and microenvironments. Pulsed electromagnetic fields (PEMFs) are becoming a potential medical technology due to its advantages of effectiveness and non-invasiveness. Numerous studies have demonstrated that PEMFs can stimulate stem cell proliferation and differentiation, regulate inflammatory reactions, accelerate wound healing, which is of great significance for tissue regeneration and repair, providing a solid basis for enlarging its clinical application. However, some important issues such as optimal parameter system and potential deep mechanisms remain to be resolved due to PEMFs window effect and biological complexity. Thus, it is of great importance to comprehensively summarizing and analyzing the literature related to the biological effects of PEMFs in tissue regeneration and repair. This review expounded the biological effects of PEMFs on stem cells, inflammation response, wound healing and musculoskeletal disorders in order to improve the application value of PEMFs in medicine. It is believed that with the continuous exploration of biological effects of PEMFs, it will be applied increasingly widely to tissue repair and other diseases.

CCL2 Knockdown Attenuates Inflammatory Response After Spinal Cord Injury Through the PI3K/Akt Signaling Pathway: Bioinformatics Analysis and Experimental Validation

Spinal cord injury (SCI) is a common clinical problem in orthopedics with a lack of effective treatments and drug targets. In the present study, we performed bioinformatic analysis of SCI datasets GSE464 and GSE45006 in the Gene Expression Omnibus (GEO) public database and experimentally validated CCL2 expression in an animal model of SCI. This was followed by stimulation of PC-12 cells using hydrogen peroxide to construct a cellular model of SCI. CCL2 expression was knocked down using small interfering RNA (si-CCL2), and PI3K signaling pathway inhibitors and activators were used to validate and observe the changes in downstream inflammation. Through data mining, we found that the inflammatory chemokine CCL2 and PI3K/Akt signaling pathways after SCI expression were significantly increased, and after peroxide stimulation of PC-12 cells with CCL2 knockdown, their downstream cellular inflammatory factor levels were decreased. The PI3K/Akt signaling pathway was blocked by PI3K inhibitors, and the downstream inflammatory response was suppressed. In contrast, when PI3K activators were used, the inflammatory response was enhanced, indicating that the CCL2-PI3K/Akt signaling pathway plays a key role in the regulation of the inflammatory response. This study revealed that the inflammatory chemokine CCL2 can regulate the inflammatory response of PC-12 cells through the PI3K/Akt signaling pathway, and blocking the expression of the inflammatory chemokine CCL2 may be a promising strategy for the treatment of secondary injury after SCI.

Tlr4 Deletion Modulates Cytokine and Extracellular Matrix Expression in Chronic Spinal Cord Injury, Leading to Improved Secondary Damage and Functional Recovery

Toll-like receptors (TLRs) play an important role in the innate immune response after CNS injury. Although TLR4 is one of the best characterized, its role in chronic stages after spinal cord injury (SCI) is not well understood. We examined the role of TLR4 signaling in injury-induced responses at 1 d, 7 d, and 8 weeks after spinal cord contusion injury in adult female TLR4 null and wild-type mice. Analyses include secondary damage, a range of transcriptome and protein analyses of inflammatory, cell death, and extracellular matrix (ECM) molecules, as well as immune cell infiltration and changes in axonal sprouting and locomotor recovery. Lack of TLR4 signaling results in reduced neuronal and myelin loss, reduced activation of NFκB, and decreased expression of inflammatory cytokines and necroptotic cell death pathway at a late time point (8 weeks) after injury. TLR4 null mice also showed reduction of scar-related ECM molecules at 8 weeks after SCI, accompanied by increase in ECM molecules associated with perineuronal nets, increased sprouting of serotonergic fibers, and improved locomotor recovery. These findings reveal novel effects of TLR4 signaling in chronic SCI. We show that TLR4 influences inflammation, cell death, and ECM deposition at late-stage post-injury when secondary injury processes are normally considered to be over. This highlights the potential for late-stage targeting of TLR4 as a potential therapy for chronic SCI.

Biodegradable nanoparticles targeting circulating immune cells reduce central and peripheral sensitization to alleviate neuropathic pain following spinal cord injury

ABSTRACT

Neuropathic pain is a critical source of comorbidity following spinal cord injury (SCI) that can be exacerbated by immune-mediated pathologies in the central and peripheral nervous systems. In this article, we investigate whether drug-free, biodegradable, poly(lactide- co -glycolide) (PLG) nanoparticle treatment mitigates the development of post-SCI neuropathic pain in female mice. Our results show that acute treatment with PLG nanoparticles following thoracic SCI significantly reduces tactile and cold hypersensitivity scores in a durable fashion. Nanoparticles primarily reduce peripheral immune-mediated mechanisms of neuropathic pain, including neuropathic pain-associated gene transcript frequency, transient receptor potential ankyrin 1 nociceptor expression, and MCP-1 (CCL2) chemokine production in the subacute period after injury. Altered central neuropathic pain mechanisms during this period are limited to reduced innate immune cell cytokine expression. However, in the chronic phase of SCI, nanoparticle treatment induces changes in both central and peripheral neuropathic pain signaling, driving reductions in cytokine production and other immune-relevant markers. This research suggests that drug-free PLG nanoparticles reprogram peripheral proalgesic pathways subacutely after SCI to reduce neuropathic pain outcomes and improve chronic central pain signaling.

A narrative review of the effects of dexamethasone on traumatic brain injury in clinical and animal studies: focusing on inflammation

Traumatic brain injury (TBI) is a type of brain injury resulting from a sudden physical force to the head. TBI can range from mild, such as a concussion, to severe, which might result in long-term complications or even death. The initial impact or primary injury to the brain is followed by neuroinflammation, excitotoxicity, and oxidative stress, which are the hallmarks of the secondary injury phase, that can further damage the brain tissue. Dexamethasone (DXM) has neuroprotective effects. It reduces neuroinflammation, a critical factor in secondary injury-associated neuronal damage. DXM can also suppress the microglia activation and infiltrated macrophages, which are responsible for producing pro-inflammatory cytokines that contribute to neuroinflammation. Considering the outcomes of this research, some of the effects of DXM on TBI include: (1) DXM-loaded hydrogels reduce apoptosis, neuroinflammation, and lesion volume and improves neuronal cell survival and motor performance, (2) DXM treatment elevates the levels of Ndufs2, Gria3, MAOB, and Ndufv2 in the hippocampus following TBI, (3) DXM decreases the quantity of circulating endothelial progenitor cells, (4) DXM reduces the expression of IL1, (5) DXM suppresses the infiltration of RhoA + cells into primary lesions of TBI and (6) DXM treatment led to an increase in fractional anisotropy values and a decrease in apparent diffusion coefficient values, indicating improved white matter integrity. According to the study, the findings show that DXM treatment has neuroprotective effects in TBI. This indicates that DXM is a promising therapeutic approach to treating TBI.

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.

Co-Administration of Resolvin D1 and Peripheral Nerve-Derived Stem Cell Spheroids as a Therapeutic Strategy in a Rat Model of Spinal Cord Injury

Spinal cord injury (SCI), primarily caused by trauma, leads to permanent and lasting loss of motor, sensory, and autonomic functions. Current therapeutic strategies are focused on mitigating secondary injury, a crucial aspect of SCI pathophysiology. Among these strategies, stem cell therapy has shown considerable therapeutic potential. This study builds on our previous work, which demonstrated the functional recovery and neuronal regeneration capabilities of peripheral nerve-derived stem cell (PNSC) spheroids, which are akin to neural crest stem cells, in SCI models. However, the limited anti-inflammatory capacity of PNSC spheroids necessitates a combined therapeutic approach. As a result, we investigated the potential of co-administering resolvin D1 (RvD1), known for its anti-inflammatory and neuroprotective properties, with PNSC spheroids. In vitro analysis confirmed RvD1's anti-inflammatory activity and its inhibitory effect on pro-inflammatory cytokines. In vivo studies involving a rat SCI model demonstrated that combined therapy of RvD1 and PNSC spheroids outperformed monotherapies, exhibiting enhanced neuronal regeneration and anti-inflammatory effects as validated through behavior tests, quantitative reverse transcription polymerase chain reaction, and immunohistochemistry. Thus, our findings suggest that the combined application of RvD1 and PNSC spheroids may represent a novel therapeutic approach for SCI management.

Tackling the glial scar in spinal cord regeneration: new discoveries and future directions

Axonal regeneration and functional recovery are poor after spinal cord injury (SCI), typified by the formation of an injury scar. While this scar was traditionally believed to be primarily responsible for axonal regeneration failure, current knowledge takes a more holistic approach that considers the intrinsic growth capacity of axons. Targeting the SCI scar has also not reproducibly yielded nearly the same efficacy in animal models compared to these neuron-directed approaches. These results suggest that the major reason behind central nervous system (CNS) regeneration failure is not the injury scar but a failure to stimulate axon growth adequately. These findings raise questions about whether targeting neuroinflammation and glial scarring still constitute viable translational avenues. We provide a comprehensive review of the dual role of neuroinflammation and scarring after SCI and how future research can produce therapeutic strategies targeting the hurdles to axonal regeneration posed by these processes without compromising neuroprotection.

Self-delivering mRNA inhibitors of MK2 improve outcomes after spinal cord injury

Functional recovery and tissue damage after spinal cord injury (SCI) are influenced by secondary damage mechanisms, including inflammation. The inflammatory response after SCI relies on a variety of cell types with both protective and cytotoxic functions. The macrophage derived MAPK-activated protein kinase 2 has been described as a critical regulator of inflammation with detrimental function after SCI. Targeted modification of inflammatory effector molecules after SCI faces challenges of optimal timing, dosage and location of administration. Modified RNA inhibitors, FANA antisense oligonucleotides, are promising inhibitors due to their stability, local penetration of cells and high efficacy in targeted suppression. Here, we describe the use of anti- MAPK-activated protein kinase 2 FANA antisense oligonucleotides in a mouse model of contusional SCI. The most efficient inhibitor was selected with in vitro and in vivo techniques and then applied via intrathecal injections after SCI. This treatment resulted in improved gait applying DigiGait assessments and tissue preservation, indicating the usefulness of the target and inhibition approach.

Therapeutic Potential of Combinative shRNA-Encoded Lentivirus-Mediated Gene Silencing to Accelerate Somatosensory Recovery After Spinal Cord Trauma

Neuropathic pain following spinal cord injury (SCI) remains a difficult problem that affects more than 80% of SCI patients. Growing evidence indicates that neuroinflammatory responses play a key role in neuropathic pain after SCI. Short hairpin RNA (shRNA) interference is an efficient tool for the knockdown of disease-related specific gene expression after SCI, yet insufficient data is available to establish guidelines. In this study, we have constructed the transient receptor potential ankyrin 1 (TRPA1) shRNA encoded-lentiviral vector (LV-shTRPA1) and P38 MAPK shRNA encoded-lentiviral vector (LV-shP38) to investigate the silencing effects of shRNAs and their ability to reprogram the neuroinflammatory responses, thereby enhancing somatosensory recovery after SCI. Our in vitro data employing HEK293-FT and activated macrophages demonstrated that delivered LV-shRNAs showed high transduction efficacy with no cytotoxicity. Furthermore, a combination of LV-shP38 and LV-shTRPA1 was found to be most effective at suppressing target genes, cutting the expression of pro-inflammatory and pro-nociceptive factors in the dorsal horn of the spinal cord and dorsal root ganglia, thus contributing to the alleviation of neuronal hypersensitivities after SCI. Overall, our data demonstrated that the combination LV-shP38/shTRPA1 produced a synergistic effect for immunomodulation and reduced neuropathic pain with a favorable risk-to-benefit ratio. Collectively, our LV-mediated shRNA delivery will provide an efficient tool for gene silencing therapeutic approaches to treat various incurable disorders.

Clinical Trials Targeting Secondary Damage after Traumatic Spinal Cord Injury

Spinal cord injury (SCI) often causes loss of sensory and motor function resulting in a significant reduction in quality of life for patients. Currently, no therapies are available that can repair spinal cord tissue. After the primary SCI, an acute inflammatory response induces further tissue damage in a process known as secondary injury. Targeting secondary injury to prevent additional tissue damage during the acute and subacute phases of SCI represents a promising strategy to improve patient outcomes. Here, we review clinical trials of neuroprotective therapeutics expected to mitigate secondary injury, focusing primarily on those in the last decade. The strategies discussed are broadly categorized as acute-phase procedural/surgical interventions, systemically delivered pharmacological agents, and cell-based therapies. In addition, we summarize the potential for combinatorial therapies and considerations.

Single cell profiling of CD45+ spinal cord cells reveals microglial and B cell heterogeneity and crosstalk following spinal cord injury

Background

Immune cells play crucial roles after spinal cord injury (SCI). However, incomplete knowledge of immune contributions to injury and repair hinders development of SCI therapies. We leveraged single-cell observations to describe key populations of immune cells present in the spinal cord and changes in their transcriptional profiles from uninjured to subacute and chronic stages of SCI.

Methods

Deep-read single-cell sequencing was performed on CD45+ cells from spinal cords of uninjured and injured Swiss-webster mice. After T9 thoracic contusion, cells were collected 3-, 7-, and 60-day post-injury (dpi). Subpopulations of CD45+ immune cells were identified informatically, and their transcriptional responses characterized with time. We compared gene expression in spinal cord microglia and B cell subpopulations with those in published models of disease and injury. Microglia were compared with Disease Associated Microglia (DAM) and Injury Responsive Microglia (IRM). B cells were compared to developmental lineage states and to an Amyotrophic Lateral Sclerosis (ALS) model.

Results

In uninjured and 7 dpi spinal cord, most CD45+ cells isolated were microglia while chronically B cells predominated. B cells accumulating in the spinal cord following injury included immature B to mature stages and were predominantly found in the injury zone. We defined diverse subtypes of microglia and B cells with altered gene expression with time after SCI. Spinal cord microglia gene expression indicates differences from brain microglia at rest and in inflammatory states. Expression analysis of signaling ligand–receptor partners identified microglia–B cell interactions at acute and chronic stages that may be involved in B cell recruitment, retention, and formation of ectopic lymphoid follicles.

Conclusions

Immune cell responses to SCI have region-specific aspects and evolve with time. Developmentally diverse populations of B cells accumulate in the spinal cord following injury. Microglia at subacute stages express B cell recruitment factors, while chronically, they express factors predicted to reduce B cell inflammatory state. In the injured spinal cord, B cells create ectopic lymphoid structures, and express secreted factors potentially acting on microglia. Our study predicts previously unidentified crosstalk between microglia and B cells post-injury at acute and chronic stages, revealing new potential targets of inflammatory responses for SCI repair warranting future functional analyses.

Selective Calpain Inhibition Improves Functional and Histopathological Outcomes in a Canine Spinal Cord Injury Model

Calpain activation has been implicated in various pathologies, including neurodegeneration. Thus, calpain inhibition could effectively prevent spinal cord injury (SCI) associated with neurodegeneration. In the current study, a dog SCI model was used to evaluate the therapeutic potential of a selective calpain inhibitor (PD150606) in combination with methylprednisolone sodium succinate (MPSS) as an anti-inflammatory drug. SCI was experimentally induced in sixteen mongrel dogs through an epidural balloon compression technique. The dogs were allocated randomly into four groups: control, MPSS, PD150606, and MPSS+PD150606. Clinical evaluation, serum biochemical, somatosensory evoked potentials, histopathological, and immunoblotting analyses were performed to assess treated dogs during the study. The current findings revealed that the combined administration of MPSS+PD150606 demonstrated considerably lower neuronal loss and microglial cell infiltration than the other groups, with a significant improvement in the locomotor score. The increased levels of inflammatory markers (GFAP and CD11) and calcium-binding proteins (Iba1 and S100) were significantly reduced in the combination group and to a lesser extent in MPSS or PD150606 treatment alone. Interestingly, the combined treatment effectively inhibited the calpain-induced cleavage of p35, limited cdk5 activation, and inhibited tau phosphorylation. These results suggest that early MPSS+PD150606 therapy after acute SCI may prevent subsequent neurodegeneration via calpain inhibition.

Muscone Can Improve Spinal Cord Injury by Activating the Angiogenin/Plexin-B2 Axis

Spinal cord injury (SCI) is a devastating neurological disorder that usually damages sensorimotor and autonomic functions. Signaling pathways can play a key role in the repair process of SCI. The plexin-B2 acts as a receptor for angiogenin and mediates ribosomal RNA transcription, influencing cell survival and proliferation. Protein kinase B serine/threonine kinase interacts with angiogenin to form a positive feedback effect. Brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor can induce angiogenin nuclear translocation. Moreover, the BDNF can promote the secretion of angiogenin. Interestingly, all of them can activate the angiogenin/plexin-B2 axis. Muscone has anti-inflammatory and proliferative features as it can inhibit nuclear transcription factor kappa-B (NF-κB) and activate the angiogenin/plexin-B2 axis, thus being significant agent in the SCI repair process. Herein, we review the potential mechanism of angiogenin/plexin-B2 axis activation and the role of muscone in SCI treatment. Muscone may attenuate inflammatory responses and promote neuronal regeneration after SCI.

Protective effects of muscone on traumatic spinal cord injury in rats

Background

Traumatic spinal cord injury (SCI) is a major clinical concern, and it is a life-changing neurological condition with substantial socioeconomic implications. Muscone has been widely used in traditional Chinese medicinal formulations for its anti-inflammatory activity. However, its protective effects on traumatic SCI have not been explored. This study investigated whether muscone plays a protective role in SCI and compared its effects with those of methylprednisolone sodium succinate (MPSS).

Methods

Rats were divided into five groups: normal saline (NS; n=24), methylprednisolone (MP; w=24), and muscone 1 (MO1), muscone 2 (MO2), and muscone 3 (MO3) (n=24 in each group, collectively called the MOx groups). The SCI rat model was established by the modified Allen's method. The rats were administered muscone (MO1: 2.5 mg/kg, MO2: 5 mg/kg, and MO3: 10 mg/kg) or MP (30 mg/kg), or an equivalent volume of saline. The rats were kept under observation for 4 weeks. Malondialdehyde (MDA), superoxide dismutase (SOD), interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-alpha (TNF-α) levels were detected using enzyme-linked immunosorbent assay (ELISA). The expression of glial fibrillary acidic protein (GFAP), B-cell lymphoma-2 (BCL-2), and caspase3 was detected by western blot analysis. Hematoxylin-eosin (HE), Nissl, and immunocytochemistry (ICC) staining was performed for pathological observation. Basso-Beattie-Bresnahan motor function scores were evaluated for assessment of neural functions after acute SCI.

Results

Muscone inhibited immune-inflammatory reactions, neuronal necrosis, and apoptosis. The lower limb function recovery was better in the MOx groups compared with NS and MP groups according to Basso-Beattie-Bresnahan scores. The changes were remarkable in the MO2 group compared with the other groups.

Conclusions

Muscone alleviates secondary injury after SCI by reducing immune-inflammatory reactions, neuronal necrosis, and apoptosis.

Chondroitin sulfate proteoglycans prevent immune cell phenotypic conversion and inflammation resolution via TLR4 in rodent models of spinal cord injury

Chondroitin sulfate proteoglycans (CSPGs) act as potent inhibitors of axonal growth and neuroplasticity after spinal cord injury (SCI). Here we reveal that CSPGs also play a critical role in preventing inflammation resolution by blocking the conversion of pro-inflammatory immune cells to a pro-repair phenotype in rodent models of SCI. We demonstrate that enzymatic digestion of CSPG glycosaminoglycans enhances immune cell clearance and reduces pro-inflammatory protein and gene expression profiles at key resolution time points. Analysis of phenotypically distinct immune cell clusters revealed CSPG-mediated modulation of macrophage and microglial subtypes which, together with T lymphocyte infiltration and composition changes, suggests a role for CSPGs in modulating both innate and adaptive immune responses after SCI. Mechanistically, CSPG activation of a pro-inflammatory phenotype in pro-repair immune cells was found to be TLR4-dependent, identifying TLR4 signalling as a key driver of CSPG-mediated immune modulation. These findings establish CSPGs as critical mediators of inflammation resolution failure after SCI in rodents, which leads to prolonged inflammatory pathology and irreversible tissue destruction.

Trehalose inhibits ferroptosis via NRF2/HO-1 pathway and promotes functional recovery in mice with spinal cord injury

Spinal cord injury (SCI) is the main cause of severe damage to the central nervous system and leads to irreversible tissue loss and neurological dysfunction. Ferroptosis is a cell death pattern, newly discovered in recent years. Ferroptosis is an oxidizing cell death induced by small molecules, and is an iron-dependent process caused by the imbalance between the generation and degradation of lipid reactive oxygen species (ROS) in cells. As an antioxidant, trehalose can effectively prevent lipid peroxidation. Studies have reported that trehalose can improve the prognosis of SCI. However, it is unclear whether these benefits are related to ferroptosis. In this study, we demonstrated for the first time that trehalose reduces the degeneration and iron accumulation of neurons by inhibiting the production of ROS and ferroptosis caused by lipid peroxides after SCI, thus promoting the survival of neurons and improving the recovery of motor function. More specifically, we found that trehalose inhibited the expansion of cavities in the nerve tissue of mice with SCI, inhibited neuron loss, and improved functional recovery. In terms of mechanism, our results indicate that the neuroprotective effect of trehalose is due to the activation of the NRF2/HO-1 pathway, which in turn inhibits ferroptosis and ferroptosis-related inflammation. Our findings provide important insights into the previously unknown role of trehalose in SCI, as well as new evidence supporting the hypothesis that suppression of ferroptosis plays a key neuroprotective role in SCI.

S100A9 blockade improves the functional recovery after spinal cord injury via mediating neutrophil infiltration

Spinal cord injury (SCI) refers to damage to the spinal cord resulting from trauma, disease or degeneration. Controlling the inflammatory process and restoring neural homeostasis is hypothesized to prevent injury aggravation. S100 calcium-binding protein A9 (S100A9) is a pro-inflammatory alarm protein, which is expressed in and released by activated neutrophils. However, whether S100A9 could serve as an effective target for the treatment of SCI has not been reported to date. In the present study, a T10 spinal cord contusion injury model was established in Sprague-Dawley rats. S100A9 expression level was determined in the serum and injured spinal cord tissue via ELISA, reverse transcription-quantitative PCR (RT-qPCR) and western blotting. The S100A9-specific blocker, ABR-238901 (ABR), was administered during the inflammatory phase of SCI, as a form of treatment. Subsequently, the morphological structure, neuronal viability and inflammatory levels of injured spinal cord were observed by histopathology, immunohistochemistry and RT-qPCR. In the obtained results, S100A9 was found to be highly expressed in the injured spinal cord and serum in the first 3 days after SCI. However, at 28 days after surgery, ABR treatment significantly improved motor function, reduced the cavity formation and neutrophil infiltration in the lesion, which was verified via H&E staining and immunohistochemistry for myeloperoxidase. Furthermore, ABR treatment was found to effectively improve the survival and viability of neurons, as shown via Nissl staining and immunofluorescence of the synaptic plasticity markers, microtubule associated protein 2 and neurofilament 200. Moreover, S100A9 blockade effectively upregulated the mRNA expression level of the anti-inflammatory genes, IL-4 and IL-10 and downregulated the mRNA expression level of the pro-inflammatory factors, IL-1β, IL-6 and TNF-α. In addition, S100A9 blockade notably alleviated the apoptosis level of the injured nerve cells. Therefore, the findings of the present study revealed that S100A9 may be a useful target for the treatment of SCI.

Treatment with Pulsed Extremely Low Frequency Electromagnetic Field (PELF-EMF) Exhibit Anti-Inflammatory and Neuroprotective Effect in Compression Spinal Cord Injury Model

Background: Spinal cord injury (SCI) pathology includes both primary and secondary events. The primary injury includes the original traumatic event, and the secondary injury, beginning immediately after the initial injury, involves progressive neuroinflammation, neuronal excitotoxicity, gliosis, and degeneration. Currently, there is no effective neuroprotective treatment for SCI. However, an accumulating body of data suggests that PELF-EMF has beneficial therapeutic effects on neurotrauma. The purpose of this study was to test the efficacy of the PELF-EMF SEQEX device using a compression SCI mouse model. Methods: C57BL/6 mice were exposed to PELF-EMF for 4 h on a daily basis for two months, beginning 2 h after a mild-moderate compression SCI. Results: The PELF-EMF treatment significantly diminished inflammatory cell infiltration and astrocyte activation by reducing Iba1, F4/80, CD68+ cells, and GAFP at the lesion borders, and increased pro-survival signaling, such as BDNF, on the neuronal cells. Moreover, the treatment exhibited a neuroprotective effect by reducing the demyelination of the axons of the white matter at the lesion’s center. Conclusions: Treatment with SEQEX demonstrated significant anti-inflammatory and neuroprotective effects. Considering our results, this safe and effective rehabilitative device, already available on the market, may provide a major therapeutic asset in the treatment of SCI.

Inflammation after spinal cord injury: a review of the critical timeline of signaling cues and cellular infiltration

Traumatic spinal cord injury (SCI) is a devastating neurological condition that results in a loss of motor and sensory function. Although extensive research to develop treatments for SCI has been performed, to date, none of these treatments have produced a meaningful amount of functional recovery after injury. The primary injury is caused by the initial trauma to the spinal cord and results in ischemia, oxidative damage, edema, and glutamate excitotoxicity. This process initiates a secondary injury cascade, which starts just a few hours post-injury and may continue for more than 6 months, leading to additional cell death and spinal cord damage. Inflammation after SCI is complex and driven by a diverse set of cells and signaling molecules. In this review, we utilize an extensive literature survey to develop the timeline of local immune cell and cytokine behavior after SCI in rodent models. We discuss the precise functional roles of several key cytokines and their effects on a variety of cell types involved in the secondary injury cascade. Furthermore, variations in the inflammatory response between rats and mice are highlighted. Since current SCI treatment options do not successfully initiate functional recovery or axonal regeneration, identifying the specific mechanisms attributed to secondary injury is critical. With a more thorough understanding of the complex SCI pathophysiology, effective therapeutic targets with realistic timelines for intervention may be established to successfully attenuate secondary damage.

Interleukin-4 and interleukin-13 induce different metabolic profiles in microglia and macrophages that relate with divergent outcomes after spinal cord injury

Background: Microglia and macrophages adopt a pro-inflammatory phenotype after spinal cord injury (SCI), what is thought to contribute to secondary tissue degeneration. We previously reported that this is due, in part, to the low levels of anti-inflammatory cytokines, such as IL-4. Since IL-13 and IL-4 share receptors and both cytokines drive microglia and macrophages towards an anti-inflammatory phenotype in vitro, here we studied whether administration of IL-13 and IL-4 after SCI leads to beneficial effects. Methods: We injected mice with recombinant IL-13 or IL-4 at 48 h after SCI and assessed their effects on microglia and macrophage phenotype and functional outcomes. We also performed RNA sequencing analysis of macrophages and microglia sorted from the injured spinal cords of mice treated with IL-13 or IL-4 and evaluated the metabolic state of these cells by using Seahorse technology. Results: We observed that IL-13 induced the expression of anti-inflammatory markers in microglia and macrophages after SCI but, in contrast to IL-4, it failed to mediate functional recovery. We found that these two cytokines induced different gene signatures in microglia and macrophages after SCI and that IL-4, in contrast to IL-13, shifted microglia and macrophage metabolism from glycolytic to oxidative phosphorylation. These findings were further confirmed by measuring the metabolic profile of these cells. Importantly, we also revealed that macrophages stimulated with IL-4 or IL-13 are not deleterious to neurons, but they become cytotoxic when oxidative metabolism is blocked. This suggests that the metabolic shift, from glycolysis to oxidative phosphorylation, is required to minimize the cytotoxic responses of microglia and macrophages. Conclusions: These results reveal that the metabolic fitness of microglia and macrophages after SCI contributes to secondary damage and that strategies aimed at boosting oxidative phosphorylation might be a novel approach to minimize the deleterious actions of microglia and macrophages in neurotrauma.

Perspectives in the Cell-Based Therapies of Various Aspects of the Spinal Cord Injury-Associated Pathologies: Lessons from the Animal Models

Traumatic injury of the spinal cord (SCI) is a devastating neurological condition often leading to severe dysfunctions, therefore an improvement in clinical treatment for SCI patients is urgently needed. The potential benefits of transplantation of various cell types into the injured spinal cord have been intensively investigated in preclinical SCI models and clinical trials. Despite the many challenges that are still ahead, cell transplantation alone or in combination with other factors, such as artificial matrices, seems to be the most promising perspective. Here, we reviewed recent advances in cell-based experimental strategies supporting or restoring the function of the injured spinal cord with a particular focus on the regenerative mechanisms that could define their clinical translation.

The Unique Properties of Placental Mesenchymal Stromal Cells: A Novel Source of Therapy for Congenital and Acquired Spinal Cord Injury

Spinal cord injury (SCI) is a devasting condition with no reliable treatment. Spina bifida is the most common cause of congenital SCI. Cell-based therapies using mesenchymal stem/stromal cells (MSCS) have been largely utilized in SCI. Several clinical trials for acquired SCI use adult tissue-derived MSC sources, including bone-marrow, adipose, and umbilical cord tissues. The first stem/stromal cell clinical trial for spina bifida is currently underway (NCT04652908). The trial uses early gestational placental-derived mesenchymal stem/stromal cells (PMSCs) during the fetal repair of myelomeningocele. PMSCs have been shown to exhibit unique neuroprotective, angiogenic, and antioxidant properties, all which are promising applications for SCI. This review will summarize the unique properties and current applications of PMSCs and discuss their therapeutic role for acquired SCI.

Inhibition of the NLRP3 inflammasome by OLT1177 induces functional protection and myelin preservation after spinal cord injury

Spinal cord injury (SCI) leads to irreversible functional deficits due to the disruption of axons and the death of neurons and glial cells. The inflammatory response that occurs in the injured spinal cord results in tissue degeneration; thus, targeting inflammation after acute SCI is expected to ameliorate histopathological evidence indicative of damage and, consequently, reduce functional disabilities. Interleukin 1 beta (IL-1β) and interleukin 18 (IL-18) are pro-inflammatory cytokines members of the IL-1 family that initiate and propagate inflammation. Here, we report that protein levels of IL-1β and IL-18 were increased in spinal cord parenchyma after SCI, but with different expression profiles. Whereas levels of IL-1β were rapidly increased reaching peak levels at 12 h after the injury, levels of IL-18 did not increase until 7 days after the injury. Since activation of the NLRP3 inflammasome is required for the processing and release of IL-1β and IL-18, we intraperitoneally administered OLT1177, a selective inhibitor of the NLRP3 inflammasome, to reduce the contribution of these cytokines to SCI. At a dose of 200 mg/kg, OLT1177 protected against neurological deficits and histological evidence of damage. OLT1177 also reduced the levels of IL-1β in the spinal cord after contusion injury and diminished the accumulation of neutrophils and macrophages at later time points. These data suggest that targeting the NLRP3 inflammasome with OLT1177 could be a novel therapeutic strategy to arrest neuroinflammation and reduce functional impairments after acute SCI in humans.

Gramine promotes functional recovery after spinal cord injury via ameliorating microglia activation

In recent years, a large number of studies have reported that neuroinflammation aggravates the occurrence of secondary injury after spinal cord injury. Gramine (GM), a natural indole alkaloid, possesses various pharmacological properties; however, the anti-inflammation property remains unclear. In our study, Gramine was investigated in vitro and in vivo to explore the neuroprotection effects. In vitro experiment, our results suggest that Gramine treatment can inhibit release of pro-inflammatory mediators. Moreover, Gramine prevented apoptosis of PC12 cells which was caused by activated HAPI microglia, and the inflammatory secretion ability of microglia was inhibited by Gramine through NF-κB pathway. The in vivo experiment is that 80 mg/kg Gramine was injected orthotopically to rats after spinal cord injury (SCI). Behavioural and histological analyses demonstrated that Gramine treatment may alleviate microglia activation and then boost recovery of motor function after SCI. Overall, our research has demonstrated that Gramine exerts suppressed microglia activation and promotes motor functional recovery after SCI through NF-κB pathway, which may put forward the prospect of clinical treatment of inflammation-related central nervous diseases.

Sirtuins: Potential Therapeutic Targets for Defense against Oxidative Stress in Spinal Cord Injury

Spinal cord injury (SCI) is one of the most incapacitating neurological disorders. It involves complex pathological processes that include a primary injury and a secondary injury phase, or a delayed stage, which follows the primary injury and contributes to the aggravation of the SCI pathology. Oxidative stress, a key pathophysiological event after SCI, contributes to a cascade of inflammation, excitotoxicity, neuronal and glial apoptosis, and other processes during the secondary injury phase. In recent years, increasing evidence has demonstrated that sirtuins are protective toward the pathological process of SCI through a variety of antioxidant mechanisms. Notably, strategies that modulate the expression of sirtuins exert beneficial effects in cellular and animal models of SCI. Given the significance and novelty of sirtuins, we summarize the oxidative stress processes that occur in SCI and discuss the antioxidant effects of sirtuins in SCI. We also highlight the potential of targeting sirtuins for the treatment of SCI.

Dual Role of Lysophosphatidic Acid Receptor 2 (LPA2) in Amyotrophic Lateral Sclerosis

Lysophosphatidic acid (LPA) is a pleiotropic extracellular lipid mediator with many physiological functions that signal through six known G protein-coupled receptors (LPA1-6). In the central nervous system (CNS), LPA mediates a wide range of effects including neural progenitor cell physiology, neuronal cell death, axonal retraction, and inflammation. Since inflammation is a hallmark of most neurological conditions, we hypothesized that LPA could be involved in the physiopathology of amyotrophic lateral sclerosis (ALS). We found that LPA2 RNA was upregulated in post-mortem spinal cord samples of ALS patients and in the sciatic nerve and skeletal muscle of SOD1G93A mouse, the most widely used ALS mouse model. To assess the contribution of LPA2 to ALS, we generated a SOD1G93A mouse that was deficient in Lpar2. This animal revealed that LPA2 signaling accelerates disease onset and neurological decline but, unexpectedly, extended the lifespan. To gain insights into the early harmful actions of LPA2 in ALS, we studied the effects of this receptor in the spinal cord, peripheral nerve, and skeletal muscle of ALS mice. We found that LPA2 gene deletion increased microglial activation but did not contribute to motoneuron death, astrogliosis, degeneration, and demyelination of motor axons. However, we observed that Lpar2 deficiency protected against muscle atrophy. Moreover, we also found the deletion of Lpar2 reduced the invasion of macrophages into the skeletal muscle of SOD1G93A mice, linking LPA2 signaling with muscle inflammation and atrophy in ALS. Overall, these results suggest for the first time that LPA2 contributes to ALS, and its genetic deletion results in protective actions at the early stages of the disease but shortens survival thereafter.

Mechanism of mesenchymal stem cells in spinal cord injury repair through macrophage polarization

Treatment and rehabilitation of spinal cord injury (SCI) is a major problem in clinical medicine. Modern medicine has achieved minimal progress in improving the functions of injured nerves in patients with SCI, mainly due to the complex pathophysiological changes that present after injury. Inflammatory reactions occurring after SCI are related to various functions of immune cells over time at different injury sites. Macrophages are important mediators of inflammatory reactions and are divided into two different subtypes (M1 and M2), which play important roles at different times after SCI. Mesenchymal stem cells (MSCs) are characterized by multi-differentiation and immunoregulatory potentials, and different treatments can have different effects on macrophage polarization. MSC transplantation has become a promising method for eliminating nerve injury caused by SCI and can help repair injured nerve tissues. Therapeutic effects are related to the induced formation of specific immune microenvironments, caused by influencing macrophage polarization, controlling the consequences of secondary injury after SCI, and assisting with function recovery. Herein, we review the mechanisms whereby MSCs affect macrophage-induced specific immune microenvironments, and discuss potential avenues of investigation for improving SCI treatment.

Inhibition of autotaxin activity ameliorates neuropathic pain derived from lumbar spinal canal stenosis

Lumbar spinal canal stenosis (LSS) or mechanical compression of dorsal root ganglion (DRG) is one of the causes of low back pain and neuropathic pain (NP). Lysophosphatidic acid (LPA) is a potent bioactive lipid mediator that is produced mainly from lysophosphatidylcholine (LPC) via autotaxin (ATX) and is known to induce NP via LPA1 receptor signaling in mice. Recently, we demonstrated that LPC and LPA were higher in cerebrospinal fluid (CSF) of patients with LSS. Based on the possible potential efficacy of the ATX inhibitor for NP treatment, we used an NP model with compression of DRG (CD model) and investigated LPA dynamics and whether ATX inhibition could ameliorate NP symptoms, using an orally available ATX inhibitor (ONO-8430506) at a dose of 30 mg/kg. In CD model, we observed increased LPC and LPA levels in CSF, and decreased threshold of the pain which were ameliorated by oral administration of the ATX inhibitor with decreased microglia and astrocyte populations at the site of the spinal dorsal horn projecting from injured DRG. These results suggested possible efficacy of ATX inhibitor for the treatment of NP caused by spinal nerve root compression and involvement of the ATX-LPA axis in the mechanism of NP induction.

Acute and non-resolving inflammation associate with oxidative injury after human spinal cord injury

Traumatic spinal cord injury is a devastating insult followed by progressive cord atrophy and neurodegeneration. Dysregulated or non-resolving inflammatory processes can disturb neuronal homeostasis and drive neurodegeneration. Here, we provide an in-depth characterization of innate and adaptive inflammatory responses as well as oxidative tissue injury in human traumatic spinal cord injury lesions compared to non-traumatic control cords. In the lesion core, microglia were rapidly lost while intermediate (co-expressing pro- as well as anti-inflammatory molecules) blood-borne macrophages dominated. In contrast, in the surrounding rim, TMEM119+ microglia numbers were maintained through local proliferation and demonstrated a predominantly pro-inflammatory phenotype. Lymphocyte numbers were low and mainly consisted of CD8+ T cells. Only in a subpopulation of patients, CD138+/IgG+ plasma cells were detected, which could serve as candidate cellular sources for a developing humoral immunity. Oxidative neuronal cell body and axonal injury was visualized by intracellular accumulation of amyloid precursor protein (APP) and oxidized phospholipids (e06) and occurred early within the lesion core and declined over time. In contrast, within the surrounding rim, pronounced APP+/e06+ axon-dendritic injury of neurons was detected, which remained significantly elevated up to months/years, thus providing mechanistic evidence for ongoing neuronal damage long after initial trauma. Dynamic and sustained neurotoxicity after human spinal cord injury might be a substantial contributor to (i) an impaired response to rehabilitation; (ii) overall failure of recovery; or (iii) late loss of recovered function (neuro-worsening/degeneration).

Extracellular and nuclear roles of IL-37 after spinal cord injury

Interleukin 37 (IL-37) is an anti-inflammatory cytokine of the interleukin 1 family. Transgenic mice expressing the human form of the IL37 gene (hIL-37Tg) display protective effects in several animal models of disease. Previous data from our group revealed that IL-37 limits inflammation after spinal cord injury (SCI) and ameliorates tissue damage and functional deficits. IL-37 can exert its anti-inflammatory effects by translocating to the nucleus or acting as an extracellular cytokine. However, whether this protection after SCI is mediated by translocating to the nucleus, activating of extracellular receptors, or both, is currently unknown. In the present study, we used different transgenic animals to answer this question. We demonstrated that the beneficial effects of IL-37 on functional and histological outcomes after SCI were lost in the lack of the extracellular receptor IL-1R8, indicating that IL-37 induces protection as an extracellular cytokine. On the other hand, transgenic mice with the nuclear function of IL-37 abolished (hIL-37D20ATg) showed significant improvement in locomotor skills and myelin sparing after SCI, indicating that nuclear pathway is not required for the protective actions of IL-37. Moreover, we also showed that the therapeutic effects of the recombinant IL-37 protein are produced only in the presence of the extracellular receptor IL-1R8, further highlighting the importance of the extracellular function of this cytokine after SCI. Finally, we revealed that the administration of recombinant IL-37 protein exerted therapeutic actions when administered in the lesion site but not systemically. This work demonstrated for the first time that translocation of IL-37 to the nucleus is not required for the beneficial actions of this cytokine after SCI and highlights the importance of the extracellular signaling of IL-37 to mediate neuroprotective actions.

Lentiviral Interleukin-10 Gene Therapy Preserves Fine Motor Circuitry and Function After a Cervical Spinal Cord Injury in Male and Female Mice

In mammals, spinal cord injuries often result in muscle paralysis through the apoptosis of lower motor neurons and denervation of neuromuscular junctions. Previous research shows that the inflammatory response to a spinal cord injury can cause additional tissue damage after the initial trauma. To modulate this inflammatory response, we delivered lentiviral anti-inflammatory interleukin-10, via loading onto an implantable biomaterial scaffold, into a left-sided hemisection at the C5 vertebra in mice. We hypothesized that improved behavioral outcomes associated with anti-inflammatory treatment are due to the sparing of fine motor circuit components. We examined behavioral recovery using a ladder beam, tissue sparing using histology, and electromyogram recordings using intraspinal optogenetic stimulation at 2 weeks post-injury. Ladder beam analysis shows interleukin-10 treatment results in significant improvement of behavioral recovery at 2 and 12 weeks post-injury when compared to mice treated with a control virus. Histology shows interleukin-10 results in greater numbers of lower motor neurons, axons, and muscle innervation at 2 weeks post-injury. Furthermore, electromyogram recordings suggest that interleukin-10-treated animals have signal-to-noise ratios and peak-to-peak amplitudes more similar to that of uninjured controls than to that of control injured animals at 2 weeks post-injury. These data show that gene therapy using anti-inflammatory interleukin-10 can significantly reduce tissue damage and subsequent motor deficits after a spinal cord injury. Together, these results suggest that early modulation of the injury response can preserve muscle function with long-lasting benefits.

CCL3 contributes to secondary damage after spinal cord injury

Background

Secondary damage after spinal cord injury (SCI) is characterized by a cascade of events including hemorrhage, apoptosis, oxidative stress, and inflammation which increase the lesion size which can influence the functional impairment. Thus, identifying specific mechanisms attributed to secondary injury is critical in minimizing tissue damage and improving neurological outcome. In this work, we are investigating the role of CCL3 (macrophage inflammatory protein 1-α, MIP-1α), a chemokine involved in the recruitment of inflammatory cells, which plays an important role in inflammatory conditions of the central and peripheral nervous system.

Methods

A mouse model of lower thoracic (T11) spinal cord contusion injury was used. We assessed expression levels of CCL3 and its receptors on the mRNA and protein level and analyzed changes in locomotor recovery and the inflammatory response in the injured spinal cord of wild-type and CCL3^−/− mice.

Results

The expression of CCL3 and its receptors was increased after thoracic contusion SCI in mice. We then examined the role of CCL3 after SCI and its direct influence on the inflammatory response, locomotor recovery and lesion size using CCL3^−/− mice. CCL3^−/− mice showed mild but significant improvement of locomotor recovery, a smaller lesion size and reduced neuronal damage compared to wild-type controls. In addition, neutrophil numbers as well as the pro-inflammatory cytokines and chemokines, known to play a deleterious role after SCI, were markedly reduced in the absence of CCL3.

Conclusion

We have identified CCL3 as a potential target to modulate the inflammatory response and secondary damage after SCI. Collectively, this study shows that CCL3 contributes to progressive tissue damage and functional impairment during secondary injury after SCI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-020-02037-3.

Clinical evaluation following the percutaneous transplantation of allogenic bone marrow-derived mesenchymal stem cells (aBM-MSC) in dogs affected by vertebral compression fracture

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Intraspinal administration of allogenic bone marrow-derived mesenchymal stem cells (aBM-MSC) along with supportive therapy can be recommended as a therapeutic strategy for managing neural defects associated with non-deviating vertebral compression fractures in canine patients.

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Percutaneous technique described in this communication is a non-invasive and efficient method that can be used for transplanting stem cell into the target site without the need of any imaging or guidance system.

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Simplified implantation protocol that can be applied in the field level.

Stem cell therapy has been extensively evaluated for its potential in managing neuronal diseases and disorders. The present study was performed to evaluate the therapeutic potential of allogenic bone marrow-derived mesenchymal stem cells (aBM-MSC) for the management of neural defects associated with vertebral compression fracture (VCF) in canine. Six clinical cases presented with the history of neural defects secondary to non-deviating VCFs were included in the present study. All the animals were subjected to detailed clinical, radiological, and haematological investigations and observations were recorded. The neurological defects in each case were graded based on routine neurological examination. The aBM-MSCs were isolated, cultured, and characterized as per ISCT criteria from the bone marrow collected from healthy dogs presented for elective surgery. The prepared cell suspension containing aBM-MSC at 3rd passage was utilized for transplantation in the clinical cases of VCF. Following the intraspinal administration of aBM-MSC, the dogs were treated with methylcobalamin and gabapentin orally throughout the study period. Improvement was evaluated on the basis of a detailed neurological examination. Significant improvement in locomotor status and sensory functions was observed in all the cases. Findings of the present study suggest that intraspinal administration of aBM-MSCs along with supportive therapy can be recommended as a therapeutic strategy for managing neural defects associated with non-deviating VCFs in canine patients.

Butylphthalide has an Anti-Inflammatory Role in Spinal Cord Injury by Promoting Macrophage/Microglia M2 Polarization via p38 Phosphorylation

STUDY DESIGN

An experimental animal study of treatment of spinal cord injury (SCI).

OBJECTIVE

This report aims to evaluate the in vivo effects of butylphthalide NBP on SCI biology and to explore its potential mechanism.

SUMMARY OF BACKGROUND DATA

SCI causes great damage to humans. The inflammatory and reconstructive processes after SCI is regulated by activation of astroglial and microglial cells. Activated microglia/macrophages can be divided into M2 (anti-inflammatory) and M1 (pro-inflammatory) phenotypes. Butylphthalide (3-n-butylphthalide or NBP) treatment can significantly alleviate ischemic brain damage, and further study has confirmed that central neuroprotective effects can be realized by converting M1 polarized microglia/macrophages to the M2 phenotype. Thus far, it remains unknown whether NBP can modulate the transition of macrophages/microglia between the M1 and M2 phenotypes.

METHODS

We randomly divided male mice into three groups (sham group, SCI group, SCI+ NBP group). Molecular and histological tests were performed to detect the macrophage/microglia polarization as well as the potential mechanism of NBP in vivo and in vitro.

RESULT

It was found that NBP treatment significantly attenuated the motor dysfunction and neuronal apoptosis induced by SCI. Treatment with NBP could also reduce pro-inflammatory cytokine release after SCI and could facilitate macrophage/microglia M2 polarization and inhibit M1 polarization after SCI. To verify the findings in animal experiments, we examined the effect of NBP on BV2 cell polarization, the results showed that NBP treatment could enhance M2 polarization and inhibit M1 polarization, and that M2 polarization occurred in a p38-dependent manner.

CONCLUSION

NBP plays an important role in the anti-inflammatory response in SCI via the facilitation of macrophage/microglia M2 polarization as well as the inhibition of macrophage/microglia M1 polarization. The M2 polarization of macrophages/microglia occurs via activation of p38 pathway.

LEVEL OF EVIDENCE

3.

Microglia as therapeutic target in central nervous system disorders

Chronic microglial activation is associated with the pathogenesis of several CNS disorders. Microglia show phenotypic diversity and functional complexity in diseased CNS. Thus, understanding the pathology-specific heterogeneity of microglial behavior is crucial for the future development of microglia-modulating therapy for variety of CNS disorders. This review summarizes up-to-date knowledge on how microglia contribute to CNS homeostasis during development and throughout adulthood. We discuss the heterogeneity of microglial phenotypes in the context of CNS disorders with an emphasis on neurodegenerative diseases, demyelinating diseases, CNS trauma, and epilepsy. We conclude this review with a discussion about the disease-specific heterogeneity of microglial function and how it could be exploited for therapeutic intervention.

Modulation of inflammatory factors predicts the outcome following spinal cord injury

BACKGROUND

The correlation between inflammatory responses caused by spinal cord injury (SCI) and the prognosis of patients with SCI still remains controversial.

METHODS

In the present study, we preliminary investigated the serum levels of interleukin (IL)-4, IL-10, major histocompatibility complex (MHC)-I, and inducible nitric oxide synthase (iNOS) and compared the serum IL-4 and IL-10 expression in rats of high Basso-Beattie-Bresnahan (BBB) scores with these of low BBB scores. Besides, the infiltration of macrophage and the axonal regeneration of the injured spinal cord were observed from day 10 to day 30.

RESULTS

We found that higher serum levels of IL-4 and IL-10 can reflect the restorability degree of SCI and could be potential biomarkers for the prognosis of SCI. The infiltration of the M2 subtype of macrophage and the axons regrowth might contribute to a better prognosis.

CONCLUSIONS

The current study demonstrates that the serum levels of IL-4 and IL-10 are preliminarily adopted as serologic markers to forecast SCI, and high serum levels of IL-4 and IL-10 may indicate a better prognosis. Moreover, the way to promote macrophage polarization from M1 to M2 may contribute to better axonal regeneration.

Biomarkers in Traumatic Spinal Cord Injury—Technical and Clinical Considerations: A Systematic Review

Objective. To examine (1) if serological or cerebrospinal fluid (CSF) biomarkers can be used as diagnostic and/or prognostic tools in patients with spinal cord injury (SCI) and (2) if literature provides recommendations regarding timing and source of biomarker evaluation. Data Sources. A systematic literature search to identify studies reporting on diagnostic and prognostic blood and/or CSF biomarkers in SCI was conducted in PubMed/MEDLINE, CINAHL, Science Direct, The Cochrane Library, ISI Web of Science, and PEDro. Study Selection. Clinical trials, cohort, and pilot studies on patients with traumatic SCI investigating at least one blood or CSF biomarker were included. Following systematic screening, 19 articles were included in the final analysis. PRISMA guidelines were followed to conduct this review. Data Extraction. Independent extraction of articles was completed by 2 authors using predefined inclusion criteria and study quality indicators. Data Synthesis. Nineteen studies published between 2002 and April 2019 with 1596 patients were included in the systematic review. In 14 studies, blood biomarkers were measured, 4 studies investigated CSF biomarkers, and 1 study used both blood and CSF samples. Conclusions. Serum/CSF concentrations of several biomarkers (S100b, IL-6, GFAP, NSE, tau, TNF-α, IL-8, MCP-1, pNF-H, and IP-10) following SCI are highly time dependent and related to injury severity. Future studies need to validate these markers as true biomarkers and should control for secondary complications associated with SCI. A deeper understanding of secondary pathophysiological events after SCI and their effect on biomarker dynamics may improve their clinical significance as surrogate parameters in future clinical studies.

The Role of Maresins in Inflammatory Pain: Function of Macrophages in Wound Regeneration

Although acute inflammatory responses are host-protective and generally self-limited, unresolved and delayed resolution of acute inflammation can lead to further tissue damage and chronic inflammation. The mechanism of pain induction under inflammatory conditions has been studied extensively; however, the mechanism of pain resolution is not fully understood. The resolution of inflammation is a biosynthetically active process, involving specialized pro-resolving mediators (SPMs). In particular, maresins (MaRs) are synthesized from docosahexaenoic acid (DHA) by macrophages and have anti-inflammatory and pro-resolving capacities as well as tissue regenerating and pain-relieving properties. A new class of macrophage-derived molecules—MaR conjugates in tissue regeneration (MCTRs)—has been reported to regulate phagocytosis and the repair and regeneration of damaged tissue. Macrophages not only participate in the biosynthesis of SPMs, but also play an important role in phagocytosis. They exhibit different phenotypes categorized as proinflammatory M1-like phenotypes and anti-inflammatory M2 phenotypes that mediate both harmful and protective functions, respectively. However, the signaling mechanisms underlying macrophage functions and phenotypic changes have not yet been fully established. Recent studies report that MaRs help resolve inflammatory pain by enhancing macrophage phagocytosis and shifting cytokine release to the anti-inflammatory M2 phenotypes. Consequently, this review elucidated the characteristics of MaRs and macrophages, focusing on the potent action of MaRs to enhance the M2 macrophage phenotype profiles that possess the ability to alleviate inflammatory pain.

Alteration of the lysophosphatidic acid and its precursor lysophosphatidylcholine levels in spinal cord stenosis: A study using a rat cauda equina compression model

Cauda equina compression (CEC) is a major cause of neurogenic claudication and progresses to neuropathic pain (NP). A lipid mediator, lysophosphatidic acid (LPA), is known to induce NP via the LPA₁ receptor. To know a possible mechanism of LPA production in neurogenic claudication, we determined the levels of LPA, lysophosphatidylcholine (LPC) and LPA-producing enzyme autotaxin (ATX), in the cerebrospinal fluid (CSF) and spinal cord (SC) using a CEC as a possible model of neurogenic claudication. Using silicon blocks within the lumbar epidural space, we developed a CEC model in rats with motor dysfunction. LPC and LPA levels in the CSF were significantly increased from day 1. Importantly, specific LPA species (16:0, 18:2, 20:4) were upregulated, which have been shown to produce by ATX detected in the CSF, without changes on its level. In SC, the LPC and LPA levels did not change, but mass spectrometry imaging analysis revealed that LPC was present in a region where the silicon blocks were inserted. These results propose a model for LPA production in SC and CSF upon neurogenic claudication that LPC produced locally by tissue damages is converted to LPA by ATX, which then leak out into the CSF.

Cell Therapeutic Strategies for Spinal Cord Injury

Significance: Spinal cord injury (SCI) is a neurological disorder that resulted from destroyed long axis of spinal cord, affecting thousands of people every year. With the occurrence of SCI, the lesions can form cystic cavities and produce glial scar, myelin inhibitor, and inflammation that negatively impact repair of spinal cord. Therefore, SCI remains a difficult problem to overcome with present therapeutics. This review of cell therapeutics in SCI provides a systematic review of combinatory therapeutics of SCI and helps the realization of regeneration of spinal cord in the future. Recent Advances: With major breakthroughs in neurobiology in recent years, present therapeutic strategies for SCI mainly aim at nerve regeneration or neuroprotection. For nerve regeneration, the application approaches are tissue engineering and cell transplantation, while drug therapeutics is applied for neuroprotection. Cell therapeutics is a new approach that treats SCI by cell transplantation. Cell therapeutics possesses advantages of neuroprotection, immune regulation, axonal regeneration, neuron relay formation, and remyelination. Critical Issues: Neurons cannot regenerate at the site of injury. Therefore, it is essential to find a repair strategy for remyelination, axon regeneration, and functional recovery. Cell therapeutics is emerging as the most promising approach for treating SCI. Future Directions: The future application of SCI therapy in clinical practice may require a combination of multiple strategies. A comprehensive treatment of injury of spinal cord is the focus of the present research. With the combination of different cell therapy strategies, future experiments will achieve more dramatic success in spinal cord repair.

MIC-1/GDF15 Overexpression Is Associated with Increased Functional Recovery in Traumatic Spinal Cord Injury

Spinal cord injury (SCI) has devastating consequences, with limited therapeutic options; therefore, improving its functional outcome is a major goal. The outcome of SCI is contributed to by neuroinflammation, which may be a target for improved recovery and quality of life after injury. Macrophage inhibitory cytokine-1/growth differentiation factor 15 (MIC-1/GDF15) has been identified as a potential novel therapy for central nervous system (CNS) injury because it is an immune regulatory cytokine with neurotrophic properties. Here we used MIC-1/GDF15 knockout (KO) and overexpressing/transgenic (Tg) and wild type (WT) animals to explore its putative therapeutic benefits in a mouse model of contusive SCI. MIC-1/GDF15 Tg mice had superior locomotor recovery and reduced secondary tissue loss at 28 days compared with their KO and WT counterparts. Overexpression of MIC-1/GDF15 coincided with increased expression of monocyte chemoattractant protein-1 (MCP-1)/C-C Motif Chemokine Ligand 2 (CCL2) at the lesion site (28 days post-SCI) and enhanced recruitment of inflammatory cells to the injured spinal cord. This inflammatory cellular infiltrate included an increased frequency of macrophages and dendritic cells (DCs) that mostly preceded recruitment of cluster of differentiation (CD)4⁺ and CD8⁺ T cells. Collectively, our findings suggest hat MIC-1/GDF15 is associated with beneficial changes in the clinical course of SCI that are characterized by altered post-injury inflammation and improved functional outcome. Further investigation of MIC-1/GDF15 as a novel therapeutic target for traumatic SCI appears warranted.

Intravascular innate immune cells reprogrammed via intravenous nanoparticles to promote functional recovery after spinal cord injury

Traumatic primary spinal cord injury (SCI) results in paralysis below the level of injury and is associated with infiltration of hematogenous innate immune cells into the injured cord. Methylprednisolone has been applied to reduce inflammation following SCI, yet was discontinued due to an unfavorable risk-benefit ratio associated with off-target effects. In this study, i.v. administered poly(lactide-coglycolide) nanoparticles were internalized by circulating monocytes and neutrophils, reprogramming these cells based on their physicochemical properties and not by an active pharmaceutical ingredient, to exhibit altered biodistribution, gene expression, and function. Approximately 80% of nanoparticle-positive immune cells were observed within the injury, and, additionally, the overall accumulation of innate immune cells at the injury was reduced 4-fold, coinciding with down-regulated expression of proinflammatory factors and increased expression of antiinflammatory and proregenerative genes. Furthermore, nanoparticle administration induced macrophage polarization toward proregenerative phenotypes at the injury and markedly reduced both fibrotic and gliotic scarring 3-fold. Moreover, nanoparticle administration with the implanted multichannel bridge led to increased numbers of regenerating axons, increased myelination with about 40% of axons myelinated, and an enhanced locomotor function (score of 6 versus 3 for control group). These data demonstrate that nanoparticles provide a platform that limits acute inflammation and tissue destruction, at a favorable risk-benefit ratio, leading to a proregenerative microenvironment that supports regeneration and functional recovery. These particles may have applications to trauma and potentially other inflammatory diseases.

Role of microglia in spinal cord injury

Myeloid cells are important effector cells in the injured spinal cord tissue. Microglia and monocyte-derived macrophages serve important functions in the injured spinal cord, and their distinctive roles can now be studied more efficiently with the help of reporter mice and cell specific markers that were described in recent years. Focusing on microglia, this review discusses the microglial response to injury, microglia specific effects and the interaction between microglia and other cell types in the injured spinal cord.

Mesenchymal Stem Cells for Spinal Cord Injury: Current Options, Limitations, and Future of Cell Therapy

Spinal cord injury (SCI) constitutes an inestimable public health issue. The most crucial phase in the pathophysiological process of SCI concerns the well-known secondary injury, which is the uncontrolled and destructive cascade occurring later with aberrant molecular signaling, inflammation, vascular changes, and secondary cellular dysfunctions. The use of mesenchymal stem cells (MSCs) represents one of the most important and promising tested strategies. Their appeal, among the other sources and types of stem cells, increased because of their ease of isolation/preservation and their properties. Nevertheless, encouraging promise from preclinical studies was followed by weak and conflicting results in clinical trials. In this review, the therapeutic role of MSCs is discussed, together with their properties, application, limitations, and future perspectives.

LINGO-1 deficiency promotes nerve regeneration through reduction of cell apoptosis, inflammation, and glial scar after spinal cord injury in mice

Leucine-rich repeat and immunoglobulin domain-containing protein 1 (LINGO-1) is a transmembrane protein that negatively regulates neural regeneration in the central nervous system. LINGO-1 expression is up-regulated after central nerve injury, and is accompanied by cell death. Both LINGO-1 and cell death in the injury microenvironment are thought to limit neural regeneration, but the relationship between LINGO-1 and cell death has not been characterized. To investigate whether LINGO-1 deletion improves the spinal cord microenvironment after spinal cord injury (SCI) and contributes to cell survival, we generated LINGO-1 knockout (KO) mice. These mice and wild-type control mice were subjected to spinal cord transection. Fourteen days after spinal cord transection, cell apoptosis, inflammation, glial scar, and growth of nerve fibers were evaluated by immunostaining. The results showed that LINGO-1 KO mice demonstrated a profound reduction in expression of caspase-3, transferase-mediated deoxyuridine triphosphate biotin nick end labeling (TUNEL), ionized calcium binding adapter molecule 1 (IBA1), glial fibrillary acidic protein (GFAP), and chondroitin sulfate proteoglycans (CSPGs) compared to controls. In contrast, expression of neurofilament (NF) at the SCI site in LINGO-1 KO mice was markedly increased compared to that in wild-type mice. These results suggested that LINGO-1 plays a critical role in the injury microenvironment in processes such as cell death, inflammatory response, and glial scar formation. Importantly, LINGO-1 deletion and a positive microenvironment may exert synergistic effects to promote nerve fiber regeneration. Therefore, inhibition of LINGO-1 may be a therapeutic strategy to promote neural regeneration following SCI.

Combination of stem cells from deciduous teeth and electroacupuncture for therapy in dogs with chronic spinal cord injury: A pilot study

Spinal cord injury (SCI) is a serious condition that causes profound economic and emotional impact in human patients and companion animal owners. It has been shown that the neurogenic effects of the stem cells are enhanced when combined with electroacupuncture (EA) in rodent models of SCI. To determine the safety and feasibility of combining transplantation of allogenic stem cells derived from canine exfoliated deciduous teeth (SCED) and EA in dogs with chronic spinal cord injury a canine pilot clinical study was conducted. A total of 16 individuals ranging from 5 to 11 years at 3 to 18 months of injury were investigated and randomly assigned to 4 experimental groups (SCED, EA, SCED + EA, control). Mild neurological and functional improvements were seen in all 4 groups. There was no clinical progression or mortality of the cases occurred in a follow up of 7 months after procedure. The study shows that SCED transplantation and electroacupuncture were feasible, safe and potentially beneficial. However Long-term patient monitoring is necessary to rule out any delayed side effects and assess any further improvements.