Absence of IL-1β positively affects neurological outcome, lesion development and axonal plasticity after spinal cord injury

Combination use of human menstrual blood stem cell- derived exosomes and hyperbaric oxygen therapy, synergistically promote recovery after spinal cord injury in rats

Traumatic spinal cord injury (TSCI) is one of the catastrophic events in the nervous system that leads to the loss of sensory and motor function of the spinal cord at the site of injury. Considering that several factors such as apoptosis, inflammation, and oxidative stress play a role in the spread of damage caused by trauma, therefore, the treatment should also be based on multifactorial approaches. Currently, we investigated the effects of human menstrual blood stem cells (MenSCs)-derived exosomes in combination with hyperbaric oxygen therapy (HBOT) in the recovery of TSCI in rats. Ninety male mature Sprague-Dawley (SD) rats were planned into five equal groups, including; control group, TSCI group, Exo group (underwent TSCI and received MenSCs -derived exosomes), HBOT group (underwent TSCI and received HBOT), and Exo+HBOT group (underwent TSCI and received MenSCs -derived exosomes plus HBOT). After the behavioral evaluation, tissue samples were obtained for stereological, immunohistochemical, biochemical, and molecular assessments. Our results showed that the numerical density of neurons, the concentrations of antioxidative biomarkers (CAT, GSH, and SOD), and neurological function scores were significantly greater in the treatments group than in the TSCI group, and these changes were more obvious in the Exo+HBOT ones (P<0.05). This is while the numerical densities of apoptotic cells and glial cells, the levels of an oxidative factor (MDA) and proinflammatory cytokines (IL-1β and TNF-α) were considerably decreased in the treatment groups, specially the Exo+HBOT group, compared to the TSCI group (P<0.05). We conclude that the co-administration of exosomes derived from MenSCs and HBOT has more neuroprotective effects in animals with TSCI.

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.

Reduced Neuroinflammation Via Astrocytes and Neutrophils Promotes Regeneration After Spinal Cord Injury in Neonatal Mice

Neonatal spinal cord injury (SCI) shows better functional outcomes than adult SCI. Although the regenerative capability in the neonatal spinal cord may have cues in the treatment of adult SCI, the mechanism underlying neonatal spinal cord regeneration after SCI is unclear. We previously reported age-dependent variation in the pathogenesis of inflammation after SCI. Therefore, we explored differences in the pathogenesis of inflammation after SCI between neonatal and adult mice and their effect on axon regeneration and functional outcome. We established two-day-old spinal cord crush mice as a model of neonatal SCI. Immunohistochemistry of the spinal cord revealed that the nuclear translocation of NF-κB, which promotes the expression of chemokines, was significantly lower in the astrocytes of neonates than in those of adults. Flow cytometry revealed that neonatal astrocytes secrete low levels of chemokines to recruit circulating neutrophils (e.g., Cxcl1 and Cxcl2) after SCI in comparison with adults. We also found that the expression of a chemokine receptor (CXCR2) and an adhesion molecule (β2 integrin) quantified by flow cytometry was lower in neonatal circulating neutrophils than in adult neutrophils. Strikingly, these neonate-specific cellular properties seemed to be associated with no neutrophil infiltration into the injured spinal cord, followed by significantly lower expression of inflammatory cytokines (Il-1β, Il-6 and TNF-α) after SCI in the spinal cords of neonates than in those of adults. At the same time, significantly fewer apoptotic neurons and greater axonal regeneration were observed in neonates in comparison with adults, which led to a marked recovery of locomotor function. This neonate-specific mechanism of inflammation regulation may have potential therapeutic applications in controlling inflammation after adult SCI.

Human Placental Mesenchymal Stem Cell-derived Exosomes in Combination with Hyperbaric Oxygen Synergistically Promote Recovery after Spinal Cord Injury in Rats

Spinal cord injury (SCI) is a critical medical condition during which sensorimotor function is lost. Current treatments are still unable to effectively improve these conditions, so it is important to pay attention to other effective approaches. Currently, we investigated the combined effects of human placenta mesenchymal stem cells (hPMSCs)-derived exosomes along with hyperbaric oxygen (HBO) in the recovery of SCI in rats. Ninety male mature Sprague-Dawley (SD) rats were allocated into five equal groups, including; sham group, SCI group, Exo group (underwent SCI and received hPMSCs-derived exosomes), HBO group (underwent SCI and received HBO), and Exo+HBO group (underwent SCI and received hPMSCs-derived exosomes plus HBO). Tissue samples at the lesion site were obtained for the evaluation of stereological, immunohistochemical, biochemical, molecular, and behavioral characteristics. Findings showed a significant increase in stereological parameters, biochemical factors (GSH, SOD, and CAT), IL-10 gene expression and behavioral functions (BBB and EMG Latency) in treatment groups, especially Exo+HBO group, compared to SCI group. In addition, MDA levels, the density of apoptotic cells and gliosis, as well as expression of inflammatory genes (TNF-α and IL-1β) were considerably reduced in treatment groups, especially Exo+HBO group, compared to SCI group. We conclude that co-administration of hPMSCs-derived exosomes and HBO has synergistic neuroprotective effects in animals undergoing SCI.

Elamipretide reduces pyroptosis and improves functional recovery after spinal cord injury

AIMS

Elamipretide (EPT), a novel mitochondria-targeted peptide, has been shown to be protective in a range of diseases. However, the effect of EPT in spinal cord injury (SCI) has yet to be elucidated. We aimed to investigate whether EPT would inhibit pyroptosis and protect against SCI.

METHODS

After establishing the SCI model, we determined the biochemical and morphological changes associated with pyroptosis, including neuronal cell death, proinflammatory cytokine expression, and signal pathway levels. Furthermore, mitochondrial function was assessed with flow cytometry, quantitative real-time polymerase chain reaction, and western blot.

RESULTS

Here, we demonstrate that EPT improved locomotor functional recovery following SCI as well as reduced neuronal loss. Moreover, EPT inhibited nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome activation and pyroptosis occurrence and decreased pro-inflammatory cytokines levels following SCI. Furthermore, EPT alleviated mitochondrial dysfunction and reduced mitochondrial reactive oxygen species level.

CONCLUSION

EPT treatment may protect against SCI via inhibition of pyroptosis.

Hyperbaric oxygen therapy and coenzyme Q10 synergistically attenuates damage progression in spinal cord injury in a rat model

BACKGROUND

Identifying effective spinal cord injury (SCI) treatments remains a major challenge, and current approaches are still unable to effectively improve its. Currently, we investigated the combined effects of hyperbaric oxygen (HBO) along with coenzyme Q10 (CoQ10) in the recovery of SCI in rats.

MATERIAL AND METHODS

Ninety female mature Sprague-Dawley rats were allocated into five equal groups, including; sham group, SCI group, HBO group (underwent SCI and received HBO), CoQ10 group (underwent SCI and received CoQ10), and HBO+CoQ10 group (underwent SCI and received HBO plus CoQ10). Tissue samples at the lesion site were obtained for evaluation of stereological, immunohistochemical, biochemical, molecular. Also, functional tests were performed to evaluate of behavioral properties.

RESULTS

We found that a significant increase in stereological parameters, biochemical factors (GSH, SOD and CAT), IL-10 gene expression and behavioral functions (BBB and EMG Latency) in the treatment groups, especially HBO+CoQ10 group, compared to SCI group. In addition, MDA levels, the density of apoptotic cells, as well as expression of inflammatory genes (TNF-α and IL-1β) were considerably reduced in the treatment groups, especially HBO+CoQ10 group, compared to SCI group.

CONCLUSION

We conclude that co-administration of HBO and HBO+CoQ10 has a synergistic neuroprotective effects in animals undergoing SCI.

Pramipexole has a neuroprotective effect in spinal cord injury and upregulates D2 receptor expression in the injured spinal cord tissue in rats

Spinal cord injury (SCI) has emerged as a prevalent condition with limited effective treatment options. The neuroprotective role of pramipexole (PPX) in inhibiting nerve cell apoptosis in central nervous system injuries is well established. Therefore, we investigated the effects of PPX in SCI. Adult Sprague-Dawley rats were divided into four groups (sham, SCI, PPX-0.25, and PPX-2.0 groups) according to the PPX therapy (n = 24). Then, SCI was induced using the modified Allen method, and PPX was intravenously administered into the tail at dosages of 0.25 or 2.0 mg/kg following the injury. Motor function was evaluated using the Rivlin-modified inclined plate apparatus and the Basso Beattie Bresnahan (BBB) workout scale. Western blotting assay was used to measure protein expression levels of DRD2, NeuN, Bax/Bcl-2, and caspase-3. Furthermore, immunohistochemistry assessed the effect of PPX on the quantity of NeuN-positive cells in the spinal cord tissue after SCI. Our findings revealed that the BBB and slanting board test scores of the PPX-treated model groups were considerably higher for the SCI group and significantly lower for the sham operation group (P < 0.001). Moreover, the PPX-2.0 group exhibited significantly higher NeuN expression levels than the SCI group (P < 0.01). Our findings indicate that PPX exerts a neuroprotective effect in secondary neuronal injury following SCI, facilitating the recovery of hind limb function by downregulating Bax/Bcl-2, caspase-3, and IL-1β.

Hyperbaric Oxygen in Combination with Epigallocatechin-3-Gallate Synergistically Enhance Recovery from Spinal Cord Injury in Rats

Spinal cord injury (SCI) following trauma is a devastating neurological event that can lead to loss of sensory and motor functions. However, the most effective measures to prevent the spread of damage are treatment measures in the early stages. Currently, we investigated the combined effects of hyperbaric oxygen (HBO) along with epigallocatechin-3-gallate (EGCG) in the recovery of SCI in rats. Ninety male mature Sprague-Dawley rats were randomly planned into five equal groups (n = 18). In addition to sham group that only underwent laminectomy, SCI rats were allocated into 4 groups as follows: control group; HBO group; EGCG group; and HBO + EGCG group. Tissue samples at the lesion site were obtained for stereological, immunohistochemical, biochemical, and molecular evaluation. In addition, behavioral tests were performed to assess of neurological functions. The finding indicated that the stereological parameters, antioxidant factors (CAT, GSH, and SOD), IL-10 gene expression levels and neurological functions were considerably increased in the treatment groups in comparison with control group, and these changes were more obvious in the HBO + EGCG group (P < 0.05). On the other hand, we observed that the density of apoptotic cells and gliosis, the biochemical levels of MDA and the expression levels of inflammatory genes (TNF-α and IL-1β) in the treatment groups, especially the HBO + EGCG group, were considerably reduced in comparison with control group (P < 0.05). We conclude that co-administration of HBO and EGCG has a synergistic neuroprotective effects in animals undergoing SCI.

Selective Inhibition of Soluble Tumor Necrosis Factor Alters the Neuroinflammatory Response following Moderate Spinal Cord Injury in Mice

Clinical and animal model studies have implicated inflammation and glial and peripheral immune cell responses in the pathophysiology of spinal cord injury (SCI). A key player in the inflammatory response after SCI is the pleiotropic cytokine tumor necrosis factor (TNF), which exists both in both a transmembrane (tmTNF) and a soluble (solTNF) form. In the present study, we extend our previous findings of a therapeutic effect of topically blocking solTNF signaling after SCI for three consecutive days on lesion size and functional outcome to study the effect on spatio-temporal changes in the inflammatory response after SCI in mice treated with the selective solTNF inhibitor XPro1595 and compared to saline-treated mice. We found that despite comparable TNF and TNF receptor levels between XPro1595- and saline-treated mice, XPro1595 transiently decreased pro-inflammatory interleukin (IL)-1β and IL-6 levels and increased pro-regenerative IL-10 levels in the acute phase after SCI. This was complemented by a decrease in the number of infiltrated leukocytes (macrophages and neutrophils) in the lesioned area of the spinal cord and an increase in the number of microglia in the peri-lesion area 14 days after SCI, followed by a decrease in microglial activation in the peri-lesion area 21 days after SCI. This translated into increased myelin preservation and improved functional outcomes in XPro1595-treated mice 35 days after SCI. Collectively, our data suggest that selective targeting of solTNF time-dependently modulates the neuroinflammatory response by favoring a pro-regenerative environment in the lesioned spinal cord, leading to improved functional outcomes.

Drug screening in zebrafish larvae reveals inflammation-related modulators of secondary damage after spinal cord injury in mice

Prolonged inflammation after spinal cord injury is detrimental to recovery. To find pharmacological modulators of the inflammation response, we designed a rapid drug screening paradigm in larval zebrafish followed by testing of hit compounds in a mouse spinal cord injury model. Methods: We used reduced il-1β linked green fluorescent protein (GFP) reporter gene expression as a read-out for reduced inflammation in a screen of 1081 compounds in larval zebrafish. Hit drugs were tested in a moderate contusion model in mice for cytokine regulation, and improved tissue preservation and locomotor recovery. Results: Three compounds robustly reduced il-1β expression in zebrafish. Cimetidine, an over-the-counter H2 receptor antagonist, also reduced the number of pro-inflammatory neutrophils and rescued recovery after injury in a zebrafish mutant with prolonged inflammation. Cimetidine action on il-1β expression levels was abolished by somatic mutation of H2 receptor hrh2b, suggesting specific action. In mice, systemic treatment with Cimetidine led to significantly improved recovery of locomotor behavior as compared to controls, accompanied by decreased neuronal tissue loss and a shift towards a pro-regenerative profile of cytokine gene expression. Conclusion: Our screen revealed H2 receptor signaling as a promising target for future therapeutic interventions in spinal cord injury. This work highlights the usefulness of the zebrafish model for rapid screening of drug libraries to identify therapeutics to treat mammalian spinal cord injury.

Quercetin in combination with hyperbaric oxygen therapy synergistically attenuates damage progression in traumatic spinal cord injury in a rat model

BACKGROUND

Oxidative stress, inflammation and cell apoptosis are the most important destructive factors in the spread of damage following trauma to the spinal cord. Therefore, presently, we investigated the synergistic effects of quercetin along with hyperbaric oxygen therapy (HBOT) as strong antioxidant, anti-inflammatory and anti-apoptotic compounds in the recovery of traumatic spinal cord injury (TSCI) in a rat model.

MATERIAL AND METHODS

Seventy-five male mature Sprague-Dawley rats allocated into 5 groups, including: Sham group (SG), TSCI group, Quercetin group (underwent TSCI and received quercetin), HBOT group (underwent TSCI and received HBOT), and Quercetin+ HBOT group (underwent TSCI and received quercetin plus HBOT). Finally, the spinal cord samples at the traumatic site were harvested and various characteristics were evaluated, including the total volumes of the spinal cord and its central cavity as well as the numerical density of neuron and glial cells by stereological method, oxidant (malondialdehyde; MDA) and antioxidant (glutathione; GSH, superoxide dismutase; SOD and catalase; CAT) factors by biochemical method, molecular levels of IL-10, TNF-α and IL-1β by qRT-PCR method, and cell apoptosis by immunohistochemistry method against Caspase-3 antibody. Furthermore, Basso-Beattie-Bresnahan (BBB) and electromyography latency (EMG Latency) tests were performed to evaluate neurological functions.

RESULTS

Findings demonstrated that the stereological characteristics, biochemical factors (except MDA), expression of IL-10 gene and behavioral functions were significantly better in Quercetin, HBOT and Quercetin+HBOT groups than TSCI group, and were greater in Quercetin+HBOT ones (P < 0.05). While MDA levels, expression of TNF-α and IL-1β genes as well as the density of apoptotic cells significantly more decreased in Quercetin+HBOT group compared to other treated groups (P < 0.05).

CONCLUSION

Overall, co-administration of quercetin with HBOT has synergistic neuroprotective effects in animals underwent TSCI.

Role of peripheral immune cells in spinal cord injury

Secondary spinal cord injury is caused by an inflammatory response cascade, and the process is irreversible. The immune system, as a mediator of inflammation, plays an important role in spinal cord injury. The spinal cord retains its immune privilege in a physiological state. Hence, elucidating the mechanisms by which peripheral immune cells are recruited to the lesion site and function after spinal cord injury is meaningful for the exploration of clinical therapeutic targets. In this review, we provide an overview of the multifaceted roles of peripheral immune cells in spinal cord injury.

Dopamine inhibits pyroptosis and attenuates secondary damage after spinal cord injury in female mice

BACKGROUND

An excessive inflammatory response accompanies the pathogenesis of spinal cord injury (SCI) and has been found to be promoted by inflammasomes in a variety of disease models. Dopamine is a neurotransmitter that also regulates nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome-dependent neuroinflammation. However, little is known regarding the effects and molecular mechanisms underlying the role of dopamine in SCI.

METHODS

Functional recovery in mice was assessed with the Basso Mouse Scale (BMS). Neuronal loss was evaluated with immunochemical staining of NeuN. Pyroptosis was assessed with immunofluorescence staining, flow cytometry, western blotting, and cell viability and cytotoxicity assays.

RESULTS

Dopamine was significantly associated with enhanced locomotor recovery after SCI, and with decreased NLRP3 inflammasome activation, pyroptosis, neuronal loss and pro-inflammatory cytokine levels. In vitro data suggested that dopamine suppressed NLRP3 inflammasome activation and pyroptosis, and decreased pro-inflammatory cytokine levels.

CONCLUSIONS

Dopamine may be a novel approach for alleviating secondary damage after SCI.

Fractional anisotropy and peripheral cytokine concentrations in outpatients with depressive episode: a diffusion tensor imaging observational study

Over the past few years, evidence of a positive relationship between inflammation and depression has grown steadily. The aim of the current study was to investigate whether such depression-related inflammation could also be associated with altered microstructural changes in the white matter. FA and serum cytokines (IL-1β, IL-6, TNF-α, and IFN-γ) were measured in 25 patients with depression (DE) and 24 healthy controls (HC). Diffusion tensor imaging was performed. Fractional anisotropy (FA) was calculated using the FSL pipeline for Tract-Based Spatial Statistics (TBSS). Both voxelwise and mean whole-brain FA were analyzed using general linear models (GLM). Higher concentrations of IL-1β were associated with lower whole-brain fractional anisotropy, particularly in people with depression (ρ = - 0.67; p < 0.001). TNF-α shared some variance with IL-1β and also showed a negative relationship between TNF-α concentrations and FA in depression (F_1,46 = 11.13, p = 0.002, η²p = 0.21). In detail, the voxelwise analysis showed that the regression slopes of IL-1β on FA were more negative in the DE group than in the HC group, mainly in the corpus callosum (cluster statistics: genu corpus callosum, p = 0.022; splenium of corpus callosum, p = 0.047). Similar effects were not found for the other remaining cytokines. This study clearly demonstrated an association between peripherally measured IL-1β and white matter integrity in depression as assessed by DTI. The results suggest that microstructural changes in the corpus callosum are associated with increased peripheral IL-1β concentrations in depression.

Interference of Interleukin-1β Mediated by Lentivirus Promotes Functional Recovery of Spinal Cord Contusion Injury in Rats via the PI3K/AKT1 Signaling Pathway

Purpose

Inflammation and apoptosis after spinal cord contusion (SCC) are important causes of irreversible spinal cord injury. Interleukin-1β (IL-1β) is a key inflammatory factor that promotes the aggravation of spinal cord contusion. However, the specific role and regulatory mechanism of IL-1β in spinal cord contusion is still unclear. Therefore, this study applied bioinformatics to analyze and mine potential gene targets interlinked with IL-1β, animal experiments and lentiviral interference technology were used to explore whether IL-1β affected the recovery of motor function in spinal cord contusion by interfering with PI3K/AKT1 signaling pathway.

Method

This study used bioinformatics to screen and analyze gene targets related to IL-1β. The rat SCC animal model was established by the Allen method, and the Basso Beattie Bresnahan (BBB) score was used to evaluate the motor function of the spinal cord-injured rats. Immunohistochemistry and immunofluorescence were used to localize the expression of IL-1β and AKT1 proteins in spinal cord tissue. Quantitative polymerase chain reaction and Western blot were used to detect the gene and protein expressions of IL-1β, PI3K, and AKT1. RNAi technology was used to construct lentivirus to inhibit the expression of IL-1β, lentiviral interference with IL-1β was used to investigate the effect of IL-1β and AKT1 on the function of spinal cord contusion and the relationship among IL-1β, AKT1, and downstream signaling pathways.

Results

Bioinformatics analysis suggested a close relationship between IL-1β and AKT1. Animal experiments have confirmed that IL-1β is closely related to the functional recovery of spinal cord contusion. Firstly, from the phenomenological level, the BBB score decreased after SCC, IL-1β and AKT1 were located in the cytoplasm of neurons in the anterior horn of the spinal cord, and the expression levels of IL-1β gene and protein in the experimental group were higher than those in the sham operation group. At the same time, the expression of AKT1 gene decreased, the results suggested that the increase of IL-1β affected the functional recovery of spinal cord contusion. Secondly, from the functional level, after inhibiting the expression of IL-1β with a lentivirus-mediated method, the BBB score was significantly increased, and the motor function of the spinal cord was improved. Thirdly, from the mechanistic level, bioinformatics analysis revealed the relationship between IL-1β and AKT1. In addition, the experiment further verified that in the PI3K/AKT1 signaling pathway, inhibition of IL-1β expression upregulated AKT1 gene expression, but PI3K expression was unchanged.

Conclusion

Inhibition of IL-1β promotes recovery of motor function after spinal cord injury in rats through upregulation of AKT1 expression in the PI3K/AKT1 signaling pathway. Bioinformatics analysis suggested that IL-1β may affect apoptosis and regeneration by inhibiting the expression of AKT1 in the PI3K/AKT1 signaling pathway to regulate the downstream FOXO, mTOR, and GSK3 signaling pathways; thereby hindering the recovery of motor function in rats after spinal cord contusion. It provided a new perspective for clinical treatment of spinal cord contusion in the future.

Inflammation: A Target for Treatment in Spinal Cord Injury

Spinal cord injury (SCI) is a significant cause of disability, and treatment alternatives that generate beneficial outcomes and have no side effects are urgently needed. SCI may be treatable if intervention is initiated promptly. Therefore, several treatment proposals are currently being evaluated. Inflammation is part of a complex physiological response to injury or harmful stimuli induced by mechanical, chemical, or immunological agents. Neuroinflammation is one of the principal secondary changes following SCI and plays a crucial role in modulating the pathological progression of acute and chronic SCI. This review describes the main inflammatory events occurring after SCI and discusses recently proposed potential treatments and therapeutic agents that regulate inflammation after insult in animal models.

Emerging role of mesenchymal stromal cells (MSCs)-derived exosome in neurodegeneration-associated conditions: a groundbreaking cell-free approach

Accumulating proofs signify that pleiotropic effects of mesenchymal stromal cells (MSCs) are not allied to their differentiation competencies but rather are mediated mainly by the releases of soluble paracrine mediators, making them a reasonable therapeutic option to enable damaged tissue repair. Due to their unique immunomodulatory and regenerative attributes, the MSC-derived exosomes hold great potential to treat neurodegeneration-associated neurological diseases. Exosome treatment circumvents drawbacks regarding the direct administration of MSCs, such as tumor formation or reduced infiltration and migration to brain tissue. Noteworthy, MSCs-derived exosomes can cross the blood-brain barrier (BBB) and then efficiently deliver their cargo (e.g., protein, miRNAs, lipid, and mRNA) to damaged brain tissue. These biomolecules influence various biological processes (e.g., survival, proliferation, migration, etc.) in neurons, oligodendrocytes, and astrocytes. Various studies have shown that the systemic or local administration of MSCs-derived exosome could lead to the favored outcome in animals with neurodegeneration-associated disease mainly by supporting BBB integrity, eliciting pro-angiogenic effects, attenuating neuroinflammation, and promoting neurogenesis in vivo. In the present review, we will deliver an overview of the therapeutic benefits of MSCs-derived exosome therapy to ameliorate the pathological symptoms of acute and chronic neurodegenerative disease. Also, the underlying mechanism behind these favored effects has been elucidated.

Topoisomerase 1 inhibition modulates pyroptosis to improve recovery after spinal cord injury

Excessive neuroinflammation and neuronal loss contribute to mechanisms of spinal cord injury (SCI). Accumulating evidence has suggested that topoisomerase 1 (Top1) inhibition can suppress exacerbated immune responses and protect against lethal inflammation. Pyroptosis is a recently identified pro-inflammatory programmed mode of cell death. However, the effects and underlying mechanisms of Top1 inhibition in SCI remains unclear. Locomotor functional recovery in mice was evaluated through Basso Mouse Scale (BMS). Neuronal loss was evaluated by immunochemistry staining of NeuN. Pyroptosis was determined by immunofluorescence staining, western blot, flow cytometry, cell viability, and cytotoxicity assays. In the present study, we estimated the effects of chemical inhibition of Top1 in an SCI model. Administration of Top1 inhibitor camptothecin (CPT) to mice significantly improved locomotor functional recovery after SCI. Moreover, CPT reduced Top1 level, inhibited nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasome activation and pyroptosis, attenuated proinflammatory cytokines levels, diminished the number of neutrophil and neuronal loss in mice. Furthermore, CPT in oxygen-glucose deprivation neurons down-regulated Top1 level, attenuated NLRP3 inflammasome activation, and suppressed pyroptosis and inflammatory response. Together, our findings indicate that inhibition of Top1 with CPT can inhibit pyroptosis, control neuroinflammation, and improve functional recovery after SCI.

Neuroinflammation Following Traumatic Brain Injury: Take It Seriously or Not

Traumatic brain injury (TBI) is associated with high mortality and disability, with a substantial socioeconomic burden. With the standardization of the treatment process, there is increasing interest in the role that the secondary insult of TBI plays in outcome heterogeneity. The secondary insult is neither detrimental nor beneficial in an absolute sense, among which the inflammatory response was a complex cascade of events and can thus be regarded as a double-edged sword. Therefore, clinicians should take the generation and balance of neuroinflammation following TBI seriously. In this review, we summarize the current human and animal model studies of neuroinflammation and provide a better understanding of the inflammatory response in the different stages of TBI. In particular, advances in neuroinflammation using proteomic and transcriptomic techniques have enabled us to identify a functional specific delineation of the immune cell in TBI patients. Based on recent advances in our understanding of immune cell activation, we present the difference between diffuse axonal injury and focal brain injury. In addition, we give a figurative profiling of the general paradigm in the pre- and post-injury inflammatory settings employing a bow-tie framework.

GIT1 Promotes Axonal Growth in an Inflammatory Environment by Promoting the Phosphorylation of MAP1B

Spinal cord injury (SCI) is a severe traumatic condition. The loss of the bundle of axons involved in motor conduction in the spinal cord after SCI is the main cause of motor function injury. Presently, axon regeneration in the spinal cord has been studied extensively, but it remains unclear how axon growth is regulated in an inflammatory environment at the cellular level. In the present study, GIT1 knockout (KO) mouse neurons were cultured in a microfluidic device to simulate the growth of axons in an inflammatory environment. The molecular regulation of axon growth in an inflammatory environment by GIT1 was then investigated. We found that the axon growth of GIT1 KO mouse neurons was restricted in an inflammatory environment. Further investigations revealed that in both axons and cell bodies in the inflammatory environment, GIT1 phosphorylated ERK, promoted the entry of Nrf2 into the nucleus, and promoted the transcription of MAP1B, thereby increasing the levels of MAP1B and p-MAP1B and promoting axon growth. We also found that MAP1B could be translated locally in axons and transported in cell bodies and axons. In conclusion, we found that GIT1 regulated axon growth in an inflammatory environment. This provided a theoretical basis for axon regeneration in an inflammatory environment after SCI to develop new treatment options for axon regeneration.

Multiple therapeutic effects of human neural stem cells derived from induced pluripotent stem cells in a rat model of post-traumatic syringomyelia

Background

Post-traumatic syringomyelia (PTS) affects patients with chronic spinal cord injury (SCI) and is characterized by progressive deterioration of neurological symptoms. To improve surgical treatment, we studied the therapeutic effects of neuroepithelial-like stem cells (NESCs) derived from induced pluripotent stem cells (iPSCs) in a rat model of PTS. To facilitate clinical translation, we studied NESCs derived from Good Manufacturing Practice (GMP)-compliant iPSCs.

Methods

Human GMP-compliant iPSCs were used to derive NESCs. Cryo-preserved NESCs were used off-the-shelf for intraspinal implantation to PTS rats 1 or 10 weeks post-injury, and rats were sacrificed 10 weeks later. In vivo cyst volumes were measured with micro-MRI. Phenotypes of differentiated NESCs and host responses were analyzed by immunohistochemistry.

Findings

Off-the-shelf NESCs transplanted to PTS rats 10 weeks post-injury reduced cyst volume. The grafted NESCs differentiated mainly into glial cells. Importantly, NESCs also stimulated tissue repair. They reduced the density of glial scars and neurite-inhibiting chondroitin sulfate proteoglycan 4 (CSPG4), stimulated host oligodendrocyte precursor cells to migrate and proliferate, reduced active microglia/macrophages, and promoted axonal regrowth after subacute as well as chronic transplantation.

Interpretation

Significant neural repair promoted by NESCs demonstrated that human NESCs could be used as a complement to standard surgery in PTS. We envisage that future PTS patients transplanted with NESCs will benefit both from eliminating the symptoms of PTS, as well as a long-term improvement of the neurological symptoms of SCI.

Funding

This work was supported by Vinnova (2016-04134), Karolinska Institutet StratRegen, and the Chinese Scholarship Council.

Administration of C5a receptor antagonist improves the efficacy of human iPSCs-derived NS/PC transplantation in the acute phase of spinal cord injury

Human-induced pluripotent stem cell-derived neural stem/progenitor cell (hiPSC-NS/PCs) transplantation during the acute phase of spinal cord injury (SCI) is not effective due to the inflammatory response occurring immediately after SCI, which negatively impacts transplanted cell survival. Therefore, we chose to study the powerful chemoattractant complement C5a as a method to generate a more favorable transplantation environment. We hypothesized that suppression of the inflammatory response immediately after SCI by C5a receptor antagonist (C5aRA) would improve the efficacy of hiPSC-NS/PCs transplantation for acute phase SCI. Here, we evaluated the influence of C5aRA on the inflammatory reaction during the acute phase after SCI, and observed significant reductions in several inflammatory cytokines, macrophages, neutrophils and apoptotic markers. Next, we divided the SCI mice into 4 groups: i) Phosphate-buffered saline (PBS) only, ii) C5aRA only, iii) PBS + transplantation (PBS+TP), and iv) C5aRA + transplantation (C5aRA+TP). Immediately after SCI, C5aRA or PBS was injected once a day for 4 consecutive days, followed by hiPSC-NS/PC transplantation or PBS into the lesion epicenter on day 4. The C5aRA+TP group had better functional improvement as compared to the PBS only group. The C5aRA+TP group also had a significantly higher cell survival rate compared to the PBS+TP group. This study demonstrates that administration of C5aRA can suppress the inflammatory response during the acute phase of SCI, while improving the survival rate of transplanted hiPSC-NS/PCs as well as enhancing motor functional restoration. hiPSC-NS/PC transplantation with C5aRA is a promising treatment during the acute injury phase for SCI patients.

Timing of Splenectomy after Acute Spinal Cord Injury

Spinal cord injury (SCI) is a devastating condition. Splenectomy may play a protective role in the development of SCI. However, little is known about whether the timing of splenectomy affects the outcome after SCI. Investigation into splenectomy after SCI would provide insight into how the timing can be selected following SCI to improve neurologic outcomes. Rats were randomized into a sham group, a nonsplenectomized group (NonSPX), four splenectomized groups with the surgery performed immediately, 6 h, 12 h, and 24 h after SCI (SPX0, SPX6, SPX12, and SPX24, respectively). Rats were subjected to severe contusive SCI at the level of the third thoracic vertebra. At different time points following SCI, Basso, Beattie, and Bresnahan (BBB) score was used to assess the recovery of injury. The animals in each group were randomly selected for tissue collection at days 3, 14, and 28 after surgery. Then, immunohistochemistry of immunologic cells was performed and inflammatory mediators were determined. Our study showed that splenectomy within 6 h after SCI improved BBB scores as compared with splenectomy more than 12 h after SCI, and decrease the immune cell responses to SCI. Protein levels of interleukin (IL)-1β and tumor necrosis factor (TNF)-α were significantly elevated in nonsplenectomized group compared with sham group. No difference was observed in IL-10 at the lesion site between splenectomized and nonsplenectomized groups at 3 d post-SCI. The study demonstrates that splenectomy within 6 h after SCI would lessen the development of SCI and improve outcome.

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.

Early Inflammation Dysregulates Neuronal Circuit Formation In Vivo via Upregulation of IL-1β

Neuroimmune interaction during development is strongly implicated in the pathogenesis of neurodevelopmental disorders, but the mechanisms that cause neuronal circuit dysregulation are not well understood. We performed in vivo imaging of the developing retinotectal system in the larval zebrafish to characterize the effects of immune system activation on refinement of an archetypal sensory processing circuit. Acute inflammatory insult induced hyperdynamic remodeling of developing retinal axons in larval fish and increased axon arbor elaboration over days. Using calcium imaging in GCaMP6s transgenic fish, we showed that these morphologic changes were accompanied by a shift toward decreased visual acuity in tectal cells. This finding was supported by poorer performance in a visually guided behavioral task. We further found that the pro-inflammatory cytokine, interleukin-1β (IL-1β), is upregulated by the inflammatory insult, and that downregulation of IL-1β abrogated the effects of inflammation on axonal dynamics and growth. Moreover, baseline branching of the retinal ganglion cell arbors in IL-1β morphant animals was significantly different from that in control larvae, and their performance in a predation assay was impaired, indicating a role for this cytokine in normal neuronal development. This work establishes a simple and powerful non-mammalian model of developmental immune activation and demonstrates a role for IL-1β in mediating the pathologic effects of inflammation on neuronal circuit development.SIGNIFICANCE STATEMENT Maternal immune activation can increase the risk of neurodevelopmental disorders in offspring; however, the mechanisms involved are not fully understood. Using a non-mammalian vertebrate model of developmental immune activation, we show that even brief activation of inflammatory pathways has immediate and long-term effects on the arborization of axons, and that these morphologic changes have functional and behavioral consequences. Finally, we show that the pro-inflammatory cytokine IL-1β plays an essential role in both the effects of inflammation on circuit formation and normal axonal development. Our data add to a growing body of evidence supporting epidemiological studies linking immune activation to neurodevelopmental disorders, and help shed light on the molecular and cellular processes that contribute to the etiology of these disorders.

MMP2 Modulates Inflammatory Response during Axonal Regeneration in the Murine Visual System

Neuroinflammation has been put forward as a mechanism triggering axonal regrowth in the mammalian central nervous system (CNS), yet little is known about the underlying cellular and molecular players connecting these two processes. In this study, we provide evidence that MMP2 is an essential factor linking inflammation to axonal regeneration by using an in vivo mouse model of inflammation-induced axonal regeneration in the optic nerve. We show that infiltrating myeloid cells abundantly express MMP2 and that MMP2 deficiency results in reduced long-distance axonal regeneration. However, this phenotype can be rescued by restoring MMP2 expression in myeloid cells via a heterologous bone marrow transplantation. Furthermore, while MMP2 deficiency does not affect the number of infiltrating myeloid cells, it does determine the coordinated expression of pro- and anti-inflammatory molecules. Altogether, in addition to its role in axonal regeneration via resolution of the glial scar, here, we reveal a new mechanism via which MMP2 facilitates axonal regeneration, namely orchestrating the expression of pro- and anti-inflammatory molecules by infiltrating innate immune cells.

Involvement of mTOR Pathways in Recovery from Spinal Cord Injury by Modulation of Autophagy and Immune Response

Traumatic spinal cord injury (SCI) is untreatable and remains the leading cause of disability. Neuroprotection and recovery after SCI can be partially achieved by rapamycin (RAPA) treatment, an inhibitor of mTORC1, complex 1 of the mammalian target of rapamycin (mTOR) pathway. However, mechanisms regulated by the mTOR pathway are not only controlled by mTORC1, but also by a second mTOR complex (mTORC2). Second-generation inhibitor, pp242, inhibits both mTORC1 and mtORC2, which led us to explore its therapeutic potential after SCI and compare it to RAPA treatment. In a rat balloon-compression model of SCI, the effect of daily RAPA (5 mg/kg; IP) and pp242 (5 mg/kg; IP) treatment on inflammatory responses and autophagy was observed. We demonstrated inhibition of the mTOR pathway after SCI through analysis of p-S6, p-Akt, and p-4E-BP1 levels. Several proinflammatory cytokines were elevated in pp242-treated rats, while RAPA treatment led to a decrease in proinflammatory cytokines. Both RAPA and pp242 treatments caused an upregulation of LC3B and led to improved functional and structural recovery in acute SCI compared to the controls, however, a greater axonal sprouting was seen following RAPA treatment. These results suggest that dual mTOR inhibition by pp242 after SCI induces distinct mechanisms and leads to recovery somewhat inferior to that following RAPA treatment.

Identification of four genes and biological characteristics associated with acute spinal cord injury in rats integrated bioinformatics analysis

BACKGROUND

Spinal cord injury (SCI) is a serious condition that can cause physical disability and sensory dysfunction. Cytokines play an extremely important role in the acute phase of SCI. Clarifying the cytokine expression profile is of great importance.

METHODS

Cytokine array analysis was used to explore the changes in 67 different proteins at 0 hours, 2 hours, 1 day, 3 days, and 7 days after acute SCI in rats. The differentially expressed cytokines in the various periods were analyzed and compared. The biological processes related to the differentially expressed proteins were examined using Gene Ontology (GO) analysis.

RESULTS

Immediately after SCI (0 hours), only ciliary neurotrophic factor (CNTF) was slightly up-regulated, while 23 other proteins were down-regulated. At 2 hours after SCI, there were 3 upregulated and 21 downregulated proteins. At 1 day after SCI, there were 5 upregulated and 6 downregulated proteins. At 3 days after SCI, there were 6 upregulated and 4 downregulated proteins. At 7 days after SCI, there were 4 upregulated and 9 downregulated proteins. Erythropoietin (EPO) and Fms related tyrosine kinase 3 ligand (Flt-3L) were downregulated at all time points. CD48 was decreased at 2 hours to 7 days after SCI. Monocyte chemotactic protein-1 (MCP-1) was the only protein that was upregulated at 2 hours to 7 days. The GO and pathway analyses revealed that the cytokine-related pathways, cell death, and proliferation might play a key role during secondary SCI.

CONCLUSIONS

This study identified 3 downregulated proteins during SCI, that being EPO, Flt-3L, and CD48. MCP-1 was the only upregulated protein, and its expression was upregulated till day 7 following SCI. These 4 identified genes may be potential therapeutic targets for the treatment of SCI.

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.

Acute IL-1RA treatment suppresses the peripheral and central inflammatory response to spinal cord injury

BACKGROUND

The acute phase response (APR) to CNS insults contributes to the overall magnitude and nature of the systemic inflammatory response. Aspects of this response are thought to drive secondary inflammatory pathology at the lesion site, and suppression of the APR can therefore afford some neuroprotection. In this study, we examined the APR in a mouse model of traumatic spinal cord injury (SCI), along with its relationship to neutrophil recruitment during the immediate aftermath of the insult. We specifically investigated the effect of IL-1 receptor antagonist (IL-1RA) administration on the APR and leukocyte recruitment to the injured spinal cord.

METHODS

Adult female C57BL/6 mice underwent either a 70kD contusive SCI, or sham surgery, and tissue was collected at 2, 6, 12, and 24 hours post-operation. For IL-1RA experiments, SCI mice received two intraperitoneal injections of human IL-1RA (100mg/kg), or saline as control, immediately following, and 5 hours after impact, and animals were sacrificed 6 hours later. Blood, spleen, liver and spinal cord were collected to study markers of central and peripheral inflammation by flow cytometry, immunohistochemistry and qPCR. Results were analysed by two-way ANOVA or student's t-test, as appropriate.

RESULTS

SCI induced a robust APR, hallmarked by elevated hepatic expression of pro-inflammatory marker genes and a significantly increased neutrophil presence in the blood, liver and spleen of these animals, as early as 2 hours after injury. This peripheral response preceded significant neutrophil infiltration of the spinal cord, which peaked 24 hours post-SCI. Although expression of IL-1RA was also induced in the liver following SCI, its response was delayed compared to IL-1β. Exogenous administration of IL-1RA during this putative therapeutic window was able to suppress the hepatic APR, as evidenced by a reduction in CXCL1 and SAA-2 expression as well as a significant decrease in neutrophil infiltration in both the liver and the injured spinal cord itself.

CONCLUSIONS

Our data indicate that peripheral administration of IL-1RA can attenuate the APR which in turn reduces immune cell infiltration at the spinal cord lesion site. We propose IL-1RA treatment as a viable therapeutic strategy to minimise the harmful effects of SCI-induced inflammation.

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.

Ascorbic Acid Promotes Functional Restoration after Spinal Cord Injury Partly by Epigenetic Modulation

Axonal regeneration after spinal cord injury (SCI) is difficult to achieve, and no fundamental treatment can be applied in clinical settings. DNA methylation has been suggested to play a role in regeneration capacity and neuronal growth after SCI by controlling the expression of regeneration-associated genes (RAGs). The aim of this study was to examine changes in neuronal DNA methylation status after SCI and to determine whether modulation of DNA methylation with ascorbic acid can enhance neuronal regeneration or functional restoration after SCI. Changes in epigenetic marks (5-hydroxymethylcytosine (5hmC) and 5-methylcytosine (5mC)); the expression of Ten-eleven translocation (Tet) family genes; and the expression of genes related to inflammation, regeneration, and degeneration in the brain motor cortex were determined following SCI. The 5hmC level within the brain was increased after SCI, especially in the acute and subacute stages, and the mRNA levels of Tet gene family members (Tet1, Tet2, and Tet3) were also increased. Administration of ascorbic acid (100 mg/kg) to SCI rats enhanced 5hmC levels; increased the expression of the Tet1, Tet2, and Tet3 genes within the brain motor cortex; promoted axonal sprouting within the lesion cavity of the spinal cord; and enhanced recovery of locomotor function until 12 weeks. In conclusion, we found that epigenetic status in the brain motor cortex is changed after SCI and that epigenetic modulation using ascorbic acid may contribute to functional recovery after SCI.

The origin, fate, and contribution of macrophages to spinal cord injury pathology

Virtually all phases of spinal cord injury pathogenesis, including inflammation, cell proliferation and differentiation, as well as tissue remodeling, are mediated in part by infiltrating monocyte-derived macrophages. It is now clear that these infiltrating macrophages have distinct functions from resident microglia and are capable of mediating both harmful and beneficial effects after injury. These divergent effects have been largely attributed to environmental cues, such as specific cytokines, that influence the macrophage polarization state. In this review, we also consider the possibility that different macrophage origins, including the spleen, bone marrow, and local self-renewal, may also affect macrophage fate, and ultimately their function that contribute to the complex pathobiology of spinal cord injury.

Dynamic control of proinflammatory cytokines Il-1β and Tnf-α by macrophages in zebrafish spinal cord regeneration

Spinal cord injury leads to a massive response of innate immune cells in non-regenerating mammals, but also in successfully regenerating zebrafish. However, the role of the immune response in successful regeneration is poorly defined. Here we show that inhibiting inflammation reduces and promoting it accelerates axonal regeneration in spinal-lesioned zebrafish larvae. Mutant analyses show that peripheral macrophages, but not neutrophils or microglia, are necessary for repair. Macrophage-less irf8 mutants show prolonged inflammation with elevated levels of Tnf-α and Il-1β. Inhibiting Tnf-α does not rescue axonal growth in irf8 mutants, but impairs it in wildtype animals, indicating a pro-regenerative role of Tnf-α. In contrast, decreasing Il-1β levels or number of Il-1β⁺ neutrophils rescue functional regeneration in irf8 mutants. However, during early regeneration, interference with Il-1β function impairs regeneration in irf8 and wildtype animals. Hence, inflammation is dynamically controlled by macrophages to promote functional spinal cord regeneration in zebrafish.

While proinflammatory signalling is preventive to axon regrowth, activated macrophages can be beneficial, for example by limiting the inflammation. This study uses mutant zebrafish lines that lack macrophages and/or microglia to show that peripheral macrophages are necessary in axon regrowth following complete transection of spinal cord.

Regulation of Inflammatory Cytokines for Spinal Cord Injury Repair Through Local Delivery of Therapeutic Agents

The balance of inflammation is critical to the repair of spinal cord injury (SCI), which is one of the most devastating traumas in human beings. Inflammatory cytokines, the direct mediators of local inflammation, have differential influences on the repair of the injured spinal cord. Some inflammatory cytokines are demonstrated beneficial to spinal cord repair in SCI models, while some detrimental. Various animal researches have revealed that local delivery of therapeutic agents efficiently regulates inflammatory cytokines and promotes repair from SCI. Quite a few clinical studies have also shown the promotion of repair from SCI through regulation of inflammatory cytokines. However, local delivery of a single agent affects only a part of the inflammatory cytokines that need to be regulated. Meanwhile, different individuals have differential profiles of inflammatory cytokines. Therefore, future studies may aim to develop personalized strategies of locally delivered therapeutic agent cocktails for effective and precise regulation of inflammation, and substantial functional recovery from SCI.

TRIM32 affects the recovery of motor function following spinal cord injury through regulating proliferation of glia

Both the extrinsic environmental factors and intrinsic neuronal mechanisms limit the axonal regeneration after spinal cord injury (SCI). However, the underlying molecular mechanisms remain unclear. In the present study, we identify tripartite motif protein 32 (TRIM32), an E3 ubiquitin ligase, which is barely detected in glial cells in the normal uninjured spinal cord, exhibits strong expression in both astrocytes and microglia following SCI. We further observe that deficiency of TRIM32 results in increased numbers of astrocytes and microglia, which is accompanied by enhanced proliferation of both cells and increased secretion of interleukin (IL)-1 and IL-10. The axonal regeneration is impaired in the spinal cord of TRIM32-/- mice following SCI, which is indicated by increased distances of the corticospinal tracts (CST) fiber to the lesion site and less axonal sprouting. We further show that deficiency of TRIM32 results in delay motor recovery following SCI. Therefore, TRIM32 is a novel essential positive factor modulating axonal regeneration and the recovery of motor function following SCI, possibly through suppressing proliferation of glial cells.

Carnosine suppresses oxygen-glucose deprivation/recovery-induced proliferation and migration of reactive astrocytes of rats in vitro

Glial scar formation resulted from excessive astrogliosis limits axonal regeneration and impairs recovery of function, thus an intervention to ameliorate excessive astrogliosis is crucial for the recovery of neurological function after cerebral ischemia. In this study we investigated the effects of carnosine, an endogenous water-soluble dipeptide (β-alanyl-L-histidine), on astrogliosis of cells exposed to oxygen-glucose deprivation/recovery (OGD/R) in vitro. Primary cultured rat astrocytes exhibited a significant increase in proliferation at 24 h recovery after OGD for 2 h. Pretreatment with carnosine (5 mmol/L) caused G₁ arrest of reactive astrocytes, significantly attenuated OGD/R-induced increase in cyclin D1 protein expression and suppressed OGD/R-induced proliferation of reactive astrocytes. Carnosine treatment also reversed glycolysis and ATP production, which was elevated at 24 h recovery after OGD. A marked increase in migration of reactive astrocytes was observed at 24 h after OGD, whereas carnosine treatment reversed the expression levels of MMP-9 and suppressed the migration of astrocytes. Furthermore, carnosine also improved neurite growth of cortical neurons co-cultured with astrocytes under ischemic conditions. These results demonstrate that carnosine may be a promising candidate for inhibiting astrogliosis and promoting neurological function recovery after ischemic stroke.

RNA Binding Protein Human Antigen R Is Translocated in Astrocytes following Spinal Cord Injury and Promotes the Inflammatory Response

Inflammation plays a prominent role in the events following traumatic injury to the central nervous system (CNS). The initial inflammatory response is driven by mediators such as tumor necrosis factor α and interleukin 1β, which are produced by activated astrocytes and microglia at the site of injury. These factors are regulated post-transcriptionally by RNA binding proteins (RBP) that interact with adenylate and uridylate-rich elements (ARE) in the 3'-untranslated region of the messenger RNA (mRNA). Human antigen R (HuR) is one of these RBPs and generally functions as a positive regulator of ARE-containing mRNAs. Here, we hypothesized that HuR plays an important role in the induction of cytokine and chemokines in astrocytes following traumatic injury. Using a mouse model of spinal cord injury, we found HuR to be extensively translocated to the cytoplasm in astrocytes at the level of injury, consistent with its activation. In an in vitro stretch injury model of CNS trauma, we observed a similar cytoplasmic shift of HuR in astrocytes and an attenuation of cytokine induction with HuR knockdown. RNA kinetics and luciferase assays suggested that the effect was more related to transcription than RNA destabilization. A small molecule inhibitor of HuR suppressed cytokine induction of injured astrocytes and reduced chemoattraction for neutrophils and microglia. In summary, HuR is activated in astrocytes in the early stages of CNS trauma and positively regulates the molecular response of key inflammatory mediators in astrocytes. Our findings suggest that HuR may be a therapeutic target in acute CNS trauma for blunting secondary tissue injury triggered by the inflammatory response.

A Comparative Study of Three Different Types of Stem Cells for Treatment of Rat Spinal Cord Injury

Three different sources of human stem cells-bone marrow-derived mesenchymal stem cells (BM-MSCs), neural progenitors (NPs) derived from immortalized spinal fetal cell line (SPC-01), and induced pluripotent stem cells (iPSCs)-were compared in the treatment of a balloon-induced spinal cord compression lesion in rats. One week after lesioning, the rats received either BM-MSCs (intrathecally) or NPs (SPC-01 cells or iPSC-NPs, both intraspinally), or saline. The rats were assessed for their locomotor skills (BBB, flat beam test, and rotarod). Morphometric analyses of spared white and gray matter, axonal sprouting, and glial scar formation, as well as qPCR and Luminex assay, were conducted to detect endogenous gene expression, while inflammatory cytokine levels were performed to evaluate the host tissue response to stem cell therapy. The highest locomotor recovery was observed in iPSC-NP-grafted animals, which also displayed the highest amount of preserved white and gray matter. Grafted iPSC-NPs and SPC-01 cells significantly increased the number of growth-associated protein 43 (GAP43+) axons, reduced astrogliosis, downregulated Casp3 expression, and increased IL-6 and IL-12 levels. hMSCs transiently decreased levels of inflammatory IL-2 and TNF-α. These findings correlate with the short survival of hMSCs, while NPs survived for 2 months and matured slowly into glia- and tissue-specific neuronal precursors. SPC-01 cells differentiated more in astroglial phenotypes with a dense structure of the implant, whereas iPSC-NPs displayed a more neuronal phenotype with a loose structure of the graft. We concluded that the BBB scores of iPSC-NP- and hMSC-injected rats were superior to the SPC-01-treated group. The iPSC-NP treatment of spinal cord injury (SCI) provided the highest recovery of locomotor function due to robust graft survival and its effect on tissue sparing, reduction of glial scarring, and increased axonal sprouting.

Anti-Inflammatory Mechanism of Neural Stem Cell Transplantation in Spinal Cord Injury

Neural stem cell (NSC) transplantation has been proposed to promote functional recovery after spinal cord injury. However, a detailed understanding of the mechanisms of how NSCs exert their therapeutic plasticity is lacking. We transplanted mouse NSCs into the injured spinal cord seven days after SCI, and the Basso Mouse Scale (BMS) score was performed to assess locomotor function. The anti-inflammatory effects of NSC transplantation was analyzed by immunofluorescence staining of neutrophil and macrophages and the detection of mRNA levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6) and interleukin-12 (IL-12). Furthermore, bone marrow-derived macrophages (BMDMs) were co-cultured with NSCs and followed by analyzing the mRNA levels of inducible nitric oxide synthase (iNOS), TNF-α, IL-1β, IL-6 and IL-10 with quantitative real-time PCR. The production of TNF-α and IL-1β by BMDMs was examined using the enzyme-linked immunosorbent assay (ELISA). Transplanted NSCs had significantly increased BMS scores (p < 0.05). Histological results showed that the grafted NSCs migrated from the injection site toward the injured area. NSCs transplantation significantly reduced the number of neutrophils and iNOS+/Mac-2+ cells at the epicenter of the injured area (p < 0.05). Meanwhile, mRNA levels of TNF-α, IL-1β, IL-6 and IL-12 in the NSCs transplantation group were significantly decreased compared to the control group. Furthermore, NSCs inhibited the iNOS expression of BMDMs and the release of inflammatory factors by macrophages in vitro (p < 0.05). These results suggest that NSC transplantation could modulate SCI-induced inflammatory responses and enhance neurological function after SCI via reducing M1 macrophage activation and infiltrating neutrophils. Thus, this study provides a new insight into the mechanisms responsible for the anti-inflammatory effect of NSC transplantation after SCI.

Interleukin-25 is detrimental for recovery after spinal cord injury in mice

Background

The cytokine, interleukin (IL)-25, is thought to be critically involved in inducing a type 2 immune response which may contribute to regeneration after central nervous system (CNS) trauma. We investigated whether applying recombinant IL-25, locally or systemically, in a mouse model of spinal cord injury (SCI) improves functional and histological recovery.

Findings

Repeated systemic administration of IL-25 did not influence functional recovery following SCI. In contrast, a single local administration of IL-25 significantly worsened locomotor outcome, which was evident from a decreased Basso mouse scale (BMS) score compared with phosphate-buffered saline (PBS)-treated controls. This was accompanied by a significant increase in lesion size, demyelination, and T helper cell infiltration.

Conclusions

These data show for the first time that IL-25 is either ineffective when applied systemically or detrimental to spinal cord recovery when applied locally. Our findings question the potential neuroprotective role of IL-25 following CNS trauma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0566-y) contains supplementary material, which is available to authorized users.

Neuroprotective effect of asiatic acid against spinal cord injury in rats

AIMS

The present study investigated the therapeutic efficacy of asiatic acid (AA) on spinal cord injury (SCI) as well as the underlying mechanisms.

MAIN METHODS

Sprague-Dawley rats (n=150) were randomly assigned to five groups: sham, SCI, SCI+methylprednisolone (30mg/kg), SCI+AA (30mg/kg), and SCI+AA (75mg/kg). Motor function, histological changes, neutrophil infiltration, proinflammatory cytokine production, and oxidative stress as well as nuclear factor erythroid 2-related factor (Nrf)2, heme oxygenase (HO)-1, and nucleotide-binding domain-like receptor protein (NLRP)3 levels were evaluated.

KEY FINDINGS

AA treatment increased Basso, Beattie and Bresnahan scores and inclined plane test scores that were reduced by SCI. In addition, AA suppressed myeloperoxidase activity and reduced the levels of interleukin-1β, -18, and -6 and tumor necrosis factor-α as well as reactive oxygen species (ROS), H2O2, and malondialdehyde levels while increasing superoxide dismutase activity and glutathione production. AA treatment results in the upregulation in Nrf2/HO-1 levels and downregulation of NLRP3 inflammasome protein expression in SC tissue.

SIGNIFICANCE

AA protects against SCI via suppression of inflammation and oxidative stress. The underlying mechanism likely involves activation of Nrf2 and HO-1 and inhibition of ROS and the NLRP3 inflammasome pathway. AA has therapeutic potential for SCI treatment.

Dopamine D1 Receptor Agonist A-68930 Inhibits NLRP3 Inflammasome Activation, Controls Inflammation, and Alleviates Histopathology in a Rat Model of Spinal Cord Injury

STUDY DESIGN

A randomized experimental study.

OBJECTIVE

The aim of this study was to investigate the therapeutic efficacy and molecular mechanisms of dopamine D1 receptor agonist A-68930 in spinal cord injury (SCI) rats.

SUMMARY OF BACKGROUND DATA

The inflammation induced by SCI includes maturation and secretion of pro-inflammatory cytokines interleukin (IL)-1β and IL-18 mediated by nucleotide-binding domain -like receptor protein 3 (NLRP3) inflammasome. Dopamine D1 receptor agonist A-68930 has been reported to exert neuroprotective effect via suppressing NLRP3 inflammasome activation in some central nervous injury models. However, whether A-68930 can exert nueroprotection in rat SCI models through inhibition of NLRP3 inflammasome activation has yet to be investigated.

METHODS

Eighty female Sprague-Dawley rats were randomly divided into 4 groups: sham group, SCI group, SCI + Vehicle (Veh) group, SCI + A-68930 group. The influences of A-68930 on the proinflammatory cytokines levels, histological changes, and locomotion scale were estimated.

RESULTS

SCI significantly promoted NLRP3 inflammasome activation and increased proinflammatory cytokines productions in SCI group as compared with sham group. A-68930 administration significantly inhibited NLRP3 inflammasome activation and reduced inflammatory cytokines levels. Moreover, A-68930 administration attenuated histopathology and promoted locomotion recovery.

CONCLUSION

A-68930 can attenuate tissue damage and improve neurological function recovery, and the mechanism may be related to the inhibition of NLRP3 inflammasome activation.

PSA-NCAM positive neural progenitors stably expressing BDNF promote functional recovery in a mouse model of spinal cord injury

Background

Neural stem cells for the treatment of spinal cord injury (SCI) are of particular interest for future therapeutic use. However, until now, stem cell therapies are often limited due to the inhibitory environment following the injury. Therefore, in this study, we aimed at testing a combinatorial approach with BDNF (brain-derived neurotrophic factor) overexpressing early neural progenitors derived from mouse embryonic stem cells. BDNF is a neurotrophin, which both facilitates neural differentiation of stem cells and favors regeneration of damaged axons.

Methods

Mouse embryonic stem cells, modified to stably express BDNF-GFP, were differentiated into PSA-NCAM positive progenitors, which were enriched, and SSEA1 depleted by a sequential procedure of magnetic-activated and fluorescence-activated cell sorting. Purified cells were injected into the lesion core seven days after contusion injury of the spinal cord in mice, and the Basso mouse scale (BMS) test to evaluate motor function was performed for 5 weeks after transplantation. To analyze axonal regeneration the anterograde tracer biotinylated dextran amine was injected into the sensorimotor cortex two weeks prior to tissue analysis. Cellular differentiation was analyzed by immunohistochemistry of spinal cord sections.

Results

Motor function was significantly improved in animals obtaining transplanted BDNF-GFP-overexpressing cells as compared to GFP-expressing cells and vehicle controls. Stem cell differentiation in vivo revealed an increase of neuronal and oligodendrocytic lineage differentiation by BDNF as evaluated by immunohistochemistry of the neuronal marker MAP2 (microtubule associated protein 2) and the oligodendrocytic markers ASPA (aspartoacylase) and Olig2 (oligodendrocyte transcription factor 2). Furthermore, axonal tracing showed a significant increase of biotin dextran amine positive corticospinal tract fibers in BDNF-GFP-cell transplanted animals caudally to the lesion site.

Conclusions

The combinatorial therapy approach by transplanting BDNF-overexpressing neural progenitors improved motor function in a mouse contusion model of SCI. Histologically, we observed enhanced neuronal and oligodendrocytic differentiation of progenitors as well as enhanced axonal regeneration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0268-x) contains supplementary material, which is available to authorized users.