Spinal Cord Injury: Pathophysiology, Multimolecular Interactions, and Underlying Recovery Mechanisms

Quercetin prevents the ferroptosis of OPCs by inhibiting the Id2/transferrin pathway

Spinal cord injury (SCI) is a destructive neurological disorder that causes impaired mobility, sensory, and autonomic dysfunctions. The loss of oligodendrocyte progenitor cells (OPCs), which can differentiate into mature oligodendrocytes and re-myelinate damaged axons, is related to poorer recovery for SCI patients. However, inhibiting OPCs loss has always been a difficult problem to overcome. In this study, we demonstrated the anti-ferroptosis effects of quercetin as a mechanism in erastin-induced OPC ferroptosis. Quercetin ameliorated erastin-induced ferroptosis in OPCs, as indicated by decreased iron concentration, reactive oxygen species (ROS) production, and increased content of glutathione (GSH) as well as more normal mitochondria morphology. Compared with erastin-induced OPCs, the myelin basic protein (MBP)-positive myelin and NF200-positive axonal was remarkably increased in quercetin-treated OPCs. Furthermore, quercetin ameliorated the erastin-induced ferroptosis as well as the myelin and axon loss of OPCs by downregulating transferrin. Transfected OPCs with transferrin overexpression plasmids significantly abrogated the protective role of quercetin in OPC ferroptosis. Using ChIP-qPCR, a direct interaction of transferrin with its upstream gene Id2 was found. The overexpression of Id2 reversed the effect of quercetin on OPC ferroptosis. In vivo study found that quercetin greatly decreased the area of injury, and enhanced the BBB score after SCI. Furthermore, in the SCI model, quercetin significantly downregulated Id2 and transferrin expression, while significantly up-regulated GPX4 and PTGS2 expression. In conclusion, quercetin prevents the ferroptosis of OPCs by inhibiting the Id2/transferrin pathway. These findings highlight quercetin as an anti-ferroptosis agent for the treatment or prevention of spinal cord injury.

Identification of canonical pyroptosis-related genes, associated regulation axis, and related traditional Chinese medicine in spinal cord injury

Neuroinflammation plays an important role in spinal cord injury (SCI), and pyroptosis is inflammatory-related programmed cell death. Although neuroinflammation induced by pyroptosis has been reported in SCI, there is a lack of systematic research on SCI pyroptosis and its regulation mechanism. The purpose of this study was to systematically analyze the expression of pyroptosis-related genes (PRGs) in different SCI models and associated regulation axis by bioinformatics methods. We downloaded raw counts data of seven high-throughput sequencings and two microarray datasets from the GEO database, classified by species (rat and mouse) and SCI modes (moderate contusive model, aneurysm clip impact-compression model, and hemisection model), including mRNAs, miRNAs, lncRNAs, and circRNAs, basically covering the acute, subacute and chronic stages of SCI. We performed differential analysis by R (DEseq2) or GEO2R and found that the AIM2/NLRC4/NLRP3 inflammasome-related genes, GSDMD, IL1B, and IL18, were highly expressed in SCI. Based on the canonical NLRP3 inflammasome-mediated pyroptosis-related genes (NLRP3/PRGs), we constructed transcription factors (TFs)-NLRP3/PRGs, miRNAs- Nlrp3/PRGs and lncRNAs/circRNAs/mRNAs-miRNA- Nlrp3/PRGs (ceRNA) networks. In addition, we also predicted Traditional Chinese medicine (TCM) and small, drug-like molecules with NLRP3/PRGs as potential targets. Finally, 39 up-regulated TFs were identified, which may regulate at least two of NLRP3/PRGs. A total of 7 down-regulated miRNAs were identified which could regulate Nlrp3/PRGs. ceRNA networks were constructed including 23 lncRNAs, 3 cicrRNAs, 6 mRNAs, and 44 miRNAs. A total of 24 herbs were identified which may with two NLRP3/PRGs as potential targets. It is expected to provide new ideas and therapeutic targets for the treatment of SCI.

Incidence and risk factors of deep vein thrombosis in patients with spinal cord injury: a systematic review with meta-analysis

Background

Spinal cord injury (SCI) is a highly disabling disease with huge public health burden. The complications associated with it, especially deep vein thrombosis (DVT), further aggravate the disability.

Objective

To explore the incidence and risk factors of DVT after SCI, in order to provide guidance for disease prevention in the future.

Methods

A search was performed on PubMed, Web of Science, Embase, and Cochrane database up to November 9, 2022. Literature screening, information extraction and quality evaluation were performed by two researchers. The data was later combined by metaprop and metan commands in STATA 16.0.

Results

A total of 101 articles were included, including 223,221 patients. Meta-analysis showed that the overall incidence of DVT was 9.3% (95% CI: 8.2%-10.6%), and the incidence of DVT in patients with acute and chronic SCI was 10.9% (95% CI: 8.7%-13.2%) and 5.3% (95% CI: 2.2%-9.7%), respectively. The incidence of DVT decreased gradually with the accumulation of publication years and sample size. However, the annual incidence of DVT has increased since 2017. There are 24 kinds of risk factors that may contribute to the formation of DVT, involving multiple aspects of the baseline characteristics of the patient, biochemical indicators, severity of SCI, and comorbidities.

Conclusions

The incidence of DVT after SCI is high and has been gradually increasing in recent years. Moreover, there are numerous risk factors associated with DVT. Comprehensive preventive measures need to be taken as early as possible in the future.

Systematic Review Registration

www.crd.york.ac.uk/prospero, identifier CRD42022377466.

The RNA binding protein HuR promotes neuronal apoptosis in rats with spinal cord injury via the HDAC1/RAD21 axis

The current research aims to study the regulation of the RNA binding protein HuR on neuronal apoptosis during spinal cord injury (SCI) and its underlying mechanism. SCI rat models were injected with HuR shRNA and/or pcDNA3.1-RAD21, followed by the evaluation of motor function, the degree of SCI, the expression of HuR and RAD21, and neuronal-like apoptosis. The co-localization of HuR-RAD21, RAD21-NeuN, and NeuN-cleaved caspase 3 was measured by immunofluorescence. Additionally, targeting relationships among HuR, HDAC1, and RAD21 were verified by chromatin immunoprecipitation and RNA immunoprecipitation. After transfection, apoptosis of PC12 cells was tested by flow cytometry. Results showed that silencing HuR or up-regulating RAD21 could alleviate SCI and reduce neuronal apoptosis. HuR could combine HDAC1 mRNA, and HDAC1 combined the promoter of RAD21. Further experiments revealed that HuR enhanced HDAC1 expression and reduced RAD21 promoter region acetylation. Overexpression of RAD21 reversed the enhancement in apoptosis of PC12 cells caused by overexpression of HuR. The injection of HuR shRNA in tail vein of SCI rats increased basso, beattie, and bresnahan score, relieved SCI, reduced HuR and HDAC1 expression, elevated RAD21 expression, and decreased neuronal-like apoptosis. However, this result was reversed by co-injection of pcDNA3.1-HDAC1. In conclusion, down-regulation of HuR alleviated SCI and neuronal apoptosis in rats by suppressing HDAC1 expression and promoting RAD21 expression.

Human Adipose-Derived Stem Cells Reduce Cellular Damage after Experimental Spinal Cord Injury in Rats

Traumatic spinal cord injury (SCI) is a devastating condition without an effective therapy. Cellular therapies are among the promising treatment strategies. Adult stem cells, such as mesenchymal stem cells, are often used clinical research for their immunomodulatory and regenerative potential. This study aimed to evaluate the effect of human adipose tissue-derived stem cells (ADSC) infusion through the cauda equina in rats with SCI. The human ADSC from bariatric surgery was isolated, expanded, and characterized. Wistar rats were subjected to blunt SCI and were divided into four groups. Two experimental groups (EG): EG1 received one ADSC infusion after SCI, and EG2 received two infusions, the first one after SCI and the second infusion seven days after the injury. Control groups (CG1 and CG2) received infusion with a culture medium. In vivo, cell tracking was performed 48 h and seven days after ADSC infusion. The animals were followed up for 40 days after SCI, and immunohistochemical quantification of myelin, neurons, and astrocytes was performed. Cellular tracking showed cell migration towards the injury site. ADSC infusion significantly reduced neuronal loss, although it did not prevent the myelin loss or enhance the area occupied by astrocytes compared to the control group. The results were similar when comparing one or two cell infusions. The injection of ADSC distal to the injured area was shown to be a safe and effective method for cellular administration in spinal cord injury.

Recent advances in the combination of cellular therapy with stem cells and nanoparticles after a spinal cord injury

Background

Currently, combined therapies could help to reduce long-term sequelae of spinal cord injury (SCI); stem cell therapy at the site of injury in combination with other therapies has shown very promising results that can be transferred to the clinical field. Nanoparticles (NPs) are versatile technologies with applications to medical research for treatments of SCI since they could deliver therapeutic molecules to the target tissue and may help to reduce the side effects of non-targeted therapies. This article's purpose is to analyze and concisely describe the diverse cellular therapies in combination with NPs and their regenerative effect after SCI.

Methods

We reviewed the literature related to combinatory therapy for motor impairment following SCI that has been published by Web of Science, Scopus, EBSCO host, and PubMed databases. The research covers the databases from 2001 to December 2022.

Result

Animal models of SCI have shown that the combination of NPs plus stem cells has a positive impact on neuroprotection and neuroregeneration. Further research is required to better understand the effects and benefits of SCI on a clinical level; therefore, it is necessary to find and select the most effective molecules that are capable of exacerbating the neurorestorative effects of the different stem cells and then try them out on patients after SCI. On the other hand, we consider that synthetic polymers such as poly [lactic-co-glycolic acid] (PLGA) could be a candidate for the design of the first therapeutic strategy that combines NPs with stem cells in patients with SCI. The reasons for the selection are that PLGA has shown important advantages over other NPs, such as being biodegradable, having low toxicity levels, and high biocompatibility; In addition, researchers could control the release time and the biodegradation kinetics, and most importantly, it could be used as NMs on other clinical pathologies (12 studies on www.clinicaltrials.gov) and has been approved by the Federal Food, Drug, and Cosmetic Act (FDA).

Conclusion

The use of cellular therapy and NPs may be a worthwhile alternative for SCI therapy; however, it is expected that the data obtained from interventions after SCI reflect an important variability of molecules combined with NPs. Therefore, it is necessary to properly define the limits of this research to be able to continue to work on the same line. Consequently, the selection of a specific therapeutic molecule and type of NPs plus stem cells are crucial to evaluate its application in clinical trials.

BMP7 Attenuates Neuroinflammation after Spinal Cord Injury by Suppressing the Microglia Activation and Inducing Microglial Polarization Via the STAT3 Pathway

Excessive activation of pro-inflammatory (M1) microglia phenotypes after spinal cord injury (SCI) disrupts tissue repair and increases the risk of secondary SCI. We previously reported that adeno-associated virus (AAV) mediated delivery of bone morphogenetic protein 7 (BMP7) promotes functional recovery after SCI by reducing oligodendrocyte loss and demyelination; however, little is known about the early effects of BMP7 in ameliorating neuroinflammation in the acute SCI phase. Herein, we demonstrate that treatment with recombinant human BMP7 (rhBMP7) suppresses the viability of LPS-induced HMC3 microglia cells and increases the proportion with the M2 phenotype. Consistently, in a rat SCI model, rhBMP7 decreases the activation of microglia and promotes M2 polarization. After rhBMP7 administration, the STAT3 signaling pathway was activated in LPS-induced HMC3 cells and microglia in spinal cord lesions. Furthermore, the levels of TNF-α and IL-1β were significantly decreased in cell culture supernatants, lesion sites of injured spinal cords, and cerebrospinal fluid circulation after rhBMP7 administration, thus reducing neuron loss in the injured spinal cord and promoting functional recovery after SCI. These results provide insight into the immediate early mechanisms by which BMP7 may ameliorate the inflammation response to secondary SCI.

Edema after CNS Trauma: A Focus on Spinal Cord Injury

Edema after spinal cord injury (SCI) is one of the first observations after the primary injury and lasts for few days after trauma. It has serious consequences on the affected tissue and can aggravate the initial devastating condition. To date, the mechanisms of the water content increase after SCI are not fully understood. Edema formation results in a combination of interdependent factors related to mechanical damage after the initial trauma progressing, along with the subacute and acute phases of the secondary lesion. These factors include mechanical disruption and subsequent inflammatory permeabilization of the blood spinal cord barrier, increase in the capillary permeability, deregulation in the hydrostatic pressure, electrolyte-imbalanced membranes and water uptake in the cells. Previous research has attempted to characterize edema formation by focusing mainly on brain swelling. The purpose of this review is to summarize the current understanding of the differences in edema formation in the spinal cord and brain, and to highlight the importance of elucidating the specific mechanisms of edema formation after SCI. Additionally, it outlines findings on the spatiotemporal evolution of edema after spinal cord lesion and provides a general overview of prospective treatment strategies by focusing on insights to prevent edema formation after SCI.

Patients with Chronic Spinal Cord Injury and a Long Period of Evolution Exhibit an Altered Cytokine Production by CD4 and CD8 T Cell Populations

Spinal cord injury (SCI) is a disabling neurological condition coursing with serious multisystem affections and morbidities. Changes in immune cell compartments have been consistently reported in previous works, representing a critical point of study for understanding the pathophysiology and progression of SCI from acute to chronic stages. Some relevant variations in circulating T cells have been noticed in patients with chronic SCI, although the number, distribution, and function of these populations remain to be fully elucidated. Likewise, the characterization of specific T cell subpopulations and their related cytokine production can aid in understanding the immunopathological role of T cells in SCI progression. In this sense, the objective of the present study was to analyze and quantify the total number of different cytokine-producers T cells in the serum of patients with chronic SCI (n = 105) in comparison to healthy controls (n = 38) by polychromatic flow cytometry. Having this goal, we studied CD4 and CD8 lymphocytes as well as naïve, effector, and effector/central memory subpopulations. SCI patients were classified according to the duration of the lesion in chronic SCI with a short period of evolution (SCI-SP) (comprised between 1 and 5 years since initial injury), early chronic phase (SCI-ECP) (between 5 and 15 years since initial injury) and late-chronic phase (SCI-LCP) (>15 years since initial injury). Our results show that patients with chronic SCI exhibited an altered immune profile of cytokine-producer T cells, including CD4/CD8 naïve, effector, and memory subpopulations in comparison to HC. In particular, IL-10 and IL-9 production seems to be importantly altered, especially in patients with SCI-LCP, whereas changes in IL-17, TNF-α, and IFN-γ T cell populations have also been reported in this and other chronic SCI groups. In conclusion, our study demonstrates an altered profile of cytokine-producer T cells in patients with chronic SCI, with marked changes throughout the course of the disease. In more detail, we have observed significant variations in cytokine production by circulating naive, effector, and effector/central memory CD4 and CD8 T cells. Future studies should be directed to explore the possible clinical consequences of these changes or develop additional translational approaches in these groups of patients.

Analysis and verification of the circRNA regulatory network RNO_CIRCpedia_ 4214/RNO-miR-667-5p/Msr1 axis as a potential ceRNA promoting macrophage M2-like polarization in spinal cord injury

BACKGROUND

CircRNAs are involved in the pathogenesis of several central nervous system diseases. However, their functions and mechanisms in spinal cord injury (SCI) are still unclear. Therefore, the purpose of this study was to evaluate circRNA and mRNA expression profiles in the pathological setting of SCI and to predict the potential function of circRNA through bioinformatics.

METHODS

A microarray-based approach was used for the simultaneous measurement of circRNAs and mRNAs, together with qPCR, fluorescence in situ hybridization, western immunoblotting, and dual-luciferase reporter assays to investigate the associated regulatory mechanisms in a rat SCI model.

RESULTS

SCI was found to be associated with the differential expression of 414 and 5337 circRNAs and mRNAs, respectively. Pathway enrichment analyses were used to predict the primary function of these circRNAs and mRNAs. GSEA analysis showed that differentially expressed mRNAs were primarily associated with inflammatory immune response activity. Further screening of these inflammation-associated genes was used to construct and analyze a competing endogenous RNA network. RNO_CIRCpedia_4214 was knocked down in vitro, resulting in reduced expression of Msr1, while the expression of RNO-miR-667-5p and Arg1 was increased. Dual-luciferase assays demonstrated that RNO_CIRCpedia_4214 bound to RNO-miR-667-5p. The RNO_CIRCpedia_4214/RNO-miR-667-5p/Msr1 axis may be a potential ceRNA that promotes macrophage M2-like polarization in SCI.

CONCLUSION

Overall, these results highlighted the critical role that circRNAs may play in the pathophysiology of SCI and the discovery of a potential ceRNA mechanism based on novel circRNAs that regulates macrophage polarization, providing new targets for the treatment of SCI.

Prognostic Value of Malondialdehyde (MDA) in the Temporal Progression of Chronic Spinal Cord Injury

Background: Oxidative stress is a major signature of spinal cord injury (SCI). The altered levels of various oxidative stress markers have been demonstrated in acute and chronic SCI. However, the variation of these markers in patients with chronic SCI depending on the time since the initial injury has not been explored yet. Objective: Our aim was to measure plasma levels of malondialdehyde (MDA), a marker of lipid peroxidation in patients with SCI stratified in different periods of suffering the injury (0–5 years, 5–10 years, and more than 10 years). Patients and methods: This cross-sectional study enrolled patients with SCI (N = 105) from different periods of the lesion and healthy control (HC) subjects (N = 38): short period (SCI SP, N = 31, time of evolution less than 5 years); early chronic (SCI ECP, N = 32, time of evolution 5–15 years); and late chronic (SCI LCP, N = 42, time of evolution more than 15 years). The plasma levels of MDA were measured using a commercially available colorimetric assay. Results: Patients with SCI had significantly higher plasma levels of MDA than HC subjects. Receiver operating characteristic (ROC) curve analysis for plasma MDA levels in patients with SCI demonstrated areas under the curve (AUC) of 1 (HC vs. SCI-SP); 0.998 (HC vs. SCI-ECP); and 0.964 (HC vs. SCI-LCP). Additionally, three ROC curves were used to compare the different concentrations of MDA between the subgroups of patients with SCI, and the resulting AUCs were: 0.896 (SCI-SP vs. SCI-ECP); 0.840 (SCI-ECP vs. SCI-LCP); and 0.979 (SCI-SP vs. SCI-LCP). Conclusion: Plasma concentration of MDA can be considered as an oxidative stress biomarker to assess the prognosis of SCI in chronic stages.

Sodium houttuyfonate exerts its neuroprotection effect by inhibiting the M1 microglia polarization in a TLR4/NF-κB signal pathway

Neuroinflammation plays an important role in secondary injury after spinal cord injury (SCI) and may aggravate neurological dysfunction. Several studies have indicated that sodium houttuyfonate (SH) can significantly inhibit macrophage- mediated inflammation; however, its effects on SCI still needs to be elucidated. We found that SH improved Basso, Beattie, and Bresnahan scores and performance in the inclined plane test of SCI model rats. The injured spinal cord exhibited less neuronal loss, cell apoptosis, and M1 microglial polarization after SH treatment. In vitro, SH reduced TLR4/NF-κB expression in cultured primary microglia and decreased M1 microglial polarization and cell apoptosis in a lipopolysaccharide (LPS)-pretreated microglia and neuron coculture system. These results indicated that SH may exert a neuroprotective effect by inhibiting M1 microglial polarization after SCI via the TLR4/NF-κB signalling pathway.

MiR-135a-5p/SP1 Axis Regulates Spinal Astrocyte Proliferation and Migration

Following spinal cord injury (SCI), astrocyte activation and proliferation result in the development of glial scars, which impede axonal growth and neurological recovery. Dysregulation of microRNAs (miRNAs) during SCI results in altered expression of downstream genes. Our previous study has revealed that miR-135a-5p regulates neuronal apoptosis and axonal growth by targeting specificity protein 1 (SP1). This study attempted to investigate whether the miR-135a-5p/SP1 axis has regulatory effect on astrocytes. Herein, lipopolysaccharide (LPS) reduced miR-135a-5p expression in astrocytes. miR-135a-5p overexpression in astrocytes resulted in a decrease in CyclinD1, MMP9, GFAP, and vimentin proteins, and thus attenuated LPS-induced proliferation and migration of astrocytes. Moreover, miR-135a-5p overexpression decreased astrocyte size and the total quantity of cell protrusions, suggesting a role for miR-135a-5p in regulating astrocyte morphology. SP1 silencing also decreased astrocyte proliferation and migration by LPS. SP1 silencing could significantly reverse the promoting effect of miR-135a-5p inhibition on astrocyte proliferation and migration. In summary, the miR-135a-5p/SP1 axis regulates astrocyte proliferation and migration after SCI. This finding benefits for the development of novel ways in treating SCI effectively.

Inhibition of Neural Stem Cell Necroptosis Mediated by RIPK1/MLKL Promotes Functional Recovery After SCI

Endogenous neural stem cells (eNSCs) are a new therapeutic strategy for the noninvasive repair of spinal cord injury (SCI). Necroptosis is a necrosome-dependent cell death process that serves as a significant regulatory mechanism in SCI. Current research shows that neurons, oligodendrocytes, and astrocytes all undergo necroptosis after SCI. However, it is unclear whether eNSCs are associated with necroptosis after SCI. By performing immunofluorescence analysis, we found that eNSCs undergo necroptosis during spinal cord injury repair in mice. Our present work demonstrates that receptor-interacting protein kinase 1 (RIPK1)/mixed lineage kinase domain-like protein (MLKL) are involved in necroptosis pathway in SCI mice. In vitro, the necroptosis induced by TNF-α/Smac-mimetic/Z-VAD-FMK (TSZ) treatment regulates phenotype of NSCs. In detail, the proliferative capacity of NSCs was significantly decreased in the presence of continual TSZ treatment, and the transcription of proinflammatory genes was upregulated, while the transcription of neurotrophic factors was inhibited. NSCs exhibited an obvious tendency to differentiate into glial cells under short-duration TSZ stimulation (6 h and 12 h); as the stimulus duration increased (24 h), the differentiation ability of the NSCs was significantly inhibited. These phenotypic changes are not conducive to neural cell survival and neural repair. Moreover, we examined the effect of necroptosis inhibitors on TSZ-treated NSCs. Necrostatin-1 and necrosulfonamide significantly reduced the necroptosis of NSCs after TSZ treatment and improved the phenotypic function of NSCs under TSZ stimulation. In additional in vivo experiments, after 2 weeks of administration, the necroptosis inhibitors reduced the necroptosis of NSCs and improved functional recovery in SCI mice. Taken together, these data indicate that the inhibition of NSC necroptosis with necroptosis inhibitors facilitates survival and phenotype maintenance in vitro and contributes to neuroprotection and repair in vivo. Our findings suggest that blocking necroptosis of eNSCs may be a potential therapeutic strategy for treating SCI.

Early versus late surgical intervention for cervical spinal cord injury: A protocol for systematic review and meta-analysis

BACKGROUND

Acute traumatic cervical spinal cord injury (SCI) is a catastrophic event with substantial physical, emotional, and economic burdens to patients, families, and society. Spinal cord decompression is recommended for the treatment of acute SCI. However, the optimal surgical timing remains controversial. Therefore, we perform a protocol for systematic review and meta-analysis to compare the efficacy of early and late surgical intervention for acute SCI.

METHODS

This systematic review and meta-analysis follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols statement, which have been registered in advance in the International prospective register of systematic reviews (registration number: CRD42023397592). We will search the following databases for randomized controlled trials: the Cochrane Skin Group Trials Register, MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, Chinese Biomedical Literature Database, Chinese Medical Current Content, and China National Knowledge Infrastructure. The risk of bias of the included studies will be appraised using the Cochrane Collaboration tool for randomized controlled trials. Statistical analysis will be performed using IBM SPSS Statistics (Armonk, NY).

RESULT

The results of this systematic review will be published in a peer-reviewed journal.

CONCLUSION

This systematic review will provide evidence regarding the optimal timing for spinal cord decompression in patients with acute SCI.

Immune Regulatory Functions of Macrophages and Microglia in Central Nervous System Diseases

Macrophages can be characterized as a very multifunctional cell type with a spectrum of phenotypes and functions being observed spatially and temporally in various disease states. Ample studies have now demonstrated a possible causal link between macrophage activation and the development of autoimmune disorders. How these cells may be contributing to the adaptive immune response and potentially perpetuating the progression of neurodegenerative diseases and neural injuries is not fully understood. Within this review, we hope to illustrate the role that macrophages and microglia play as initiators of adaptive immune response in various CNS diseases by offering evidence of: (1) the types of immune responses and the processes of antigen presentation in each disease, (2) receptors involved in macrophage/microglial phagocytosis of disease-related cell debris or molecules, and, finally, (3) the implications of macrophages/microglia on the pathogenesis of the diseases.

Swimming training combined with fecal microbial transplantation protects motor functions in rats with spinal cord injury by improving the intestinal system

Spinal cord injury (SCI) leads to severe intestinal dysfunction and decreased motility. There is an interaction between the intestine and the nervous system, intestinal intervention through microbial regulation and exercise is a potential treatment option for spinal cord injury. We investigated the effects of swimming rehabilitation training combined with fecal microbial transplantation on intestinal as well as neurological functions in rats with spinal cord injuries, and explored the potential mechanisms. The animals were randomly divided into five groups: sham-operated control group (Sham), spinal cord injury only group (SCI), swimming training group (Swimming), fecal microbial transplantation group (FMT) and combined interventions group (Combined). Behavioral assessments, pathological and immunological analyses were performed after the interventions. Compared to rats in the spinal cord injury group, rats subjected to swimming training, fecal microbial transplantation and combined interventions group exhibited improved intestinal transit, barrier functions, motility, and motor conduction pathway conductivity(P < 0.05). The combined interventions group had better outcomes(P < 0.01). In addition, combined interventions significantly suppressed inflammatory factor levels (P < 0.05) in the colon and spinal cords and significantly protected forefoot motor neurons (NeuN) in the spinal cord injury area, inhibiting astrocyte activation and reducing the expressions of the signature glial fibrillary acidic protein (GFAP) and markers of microglia (Iba-1) at the lesion site(P < 0.05). In conclusion, all effects of combined swimming training and fecal microbial transplantation interventions were superior to swimming training or fecal microbial transplantation alone. Swimming training and fecal microbial transplantation interventions have a synergistic effect on the recovery of intestinal function and motility after spinal cord injury. The mechanism of mutual facilitation between gut function and motility may be related to the brain-gut axis interaction.

Immunization with Neural-Derived Peptides in Neurodegenerative Diseases: A Narrative Review

Neurodegenerative diseases (NDDs) are a major health problem worldwide. Statistics suggest that in America in 2030 there will be more than 12 million people suffering from a neurodegenerative pathology. Furthermore, the increase in life expectancy enhances the importance of finding new and better therapies for these pathologies. NDDs could be classified into chronic or acute, depending on the time required for the development of clinical symptoms and brain degeneration. Nevertheless, both chronic and acute stages share a common immune and inflammatory pathway in their pathophysiology. Immunization with neural-derived peptides (INDP) is a novel therapy that has been studied during the last decade. By inoculating neural-derived peptides obtained from the central nervous system (CNS), this therapy aims to boost protective autoimmunity, an autoreactive response that leads to a protective phenotype that produces a healing environment and neuroregeneration instead of causing damage. INDP has shown promising findings in studies performed either in vitro, in vivo or even in some pre-clinical trials of different NDDs, standing as a potentially beneficial therapy. In this review, we will describe some of the studies in which the effect of INDP strategies have been explored in different (chronic and acute) neurodegenerative diseases.

Multidisciplinary Approach to Spinal Metastases and Metastatic Spinal Cord Compression—A New Integrative Flowchart for Patient Management

Metastatic spine disease (MSD) and metastatic spinal cord compression (MSCC) are major causes of permanent neurological damage and long-term disability for cancer patients. The development of MSD is pathophysiologically framed by a cooperative interaction between general mechanisms of bone growth and specific mechanisms of spinal metastases (SM) expansion. SM most commonly affects the thoracic spine, even though multiple segments may be affected concomitantly. The great majority of SM are extradural, while intradural-extramedullary and intramedullary metastases are less frequently seen. The management of patients with SM is particularly complex and challenging, with multiple factors—such as the spinal stability status, primary tumor radio and chemosensitivity, cancer biological burden, patient performance status and comorbidities, and patient’s oncological prognosis—influencing the clinical decision-making process. Different frameworks were developed in order to systematize and support this process. A multidisciplinary, personalized approach, enriched by the expertise of each involved specialty, is crucial. We reviewed the most recent evidence and proposed an updated algorithmic approach to patients with MSD according to the clinical scenario of each patient. A flowchart-based approach offers an evidence-based management of MSD, providing a valuable clinical decision tool in a context of high uncertainty and quick-acting need.

Exosomes combined with biomaterials in the treatment of spinal cord injury

Spinal cord injury (SCI) is a serious and disabling disease with a high mortality rate. It often leads to complete or partial sensory and motor dysfunction and is accompanied by a series of secondary outcomes, such as pressure sores, pulmonary infections, deep vein thrombosis in the lower extremities, urinary tract infections, and autonomic dysfunction. Currently, the main treatments for SCI include surgical decompression, drug therapy, and postoperative rehabilitation. Studies have shown that cell therapy plays a beneficial role in the treatment of SCI. Nonetheless, there is controversy regarding the therapeutic effect of cell transplantation in SCI models. Meanwhile exosomes, as a new therapeutic medium for regenerative medicine, possess the advantages of small size, low immunogenicity, and the ability to cross the blood-spinal cord barrier. Certain studies have shown that stem cell-derived exosomes have anti-inflammatory effects and can play an irreplaceable role in the treatment of SCI. In this case, it is difficult for a single treatment method to play an effective role in the repair of neural tissue after SCI. The combination of biomaterial scaffolds and exosomes can better transfer and fix exosomes to the injury site and improve their survival rate. This paper first reviews the current research status of stem cell-derived exosomes and biomaterial scaffolds in the treatment of SCI respectively, and then describes the application of exosomes combined with biomaterial scaffolds in the treatment of SCI, as well as the challenges and prospects.

Protein arginine methyltransferase 8 regulates ferroptosis and macrophage polarization in spinal cord injury via glial cell-derived neurotrophic factor

OBJECTIVE

To explore the influence of protein arginine methyltransferase 8 (PRMT8) regulating glial cell-derived neurotrophic factor (GDNF) on neuron ferroptosis and macrophage polarization in spinal cord injury (SCI).

METHODS

A rat model of SCI was established through an injury induced by an external force. Basso, Beattie, and Bresnahan score, hematoxylin and eosin staining, and immunofluorescence were used, respectively, to detect changes in rat locomotion, spinal cord histopathology, and NeuN expression in the spinal cord. Iron content in the spinal cord and levels of malondialdehyde and glutathione were measured using detection kits. Transmission electron microscopy was used to reveal the morphological characteristics of mitochondria. Western blotting was performed to detect PRMT8, GDNF, cystine/glutamate transporter XCT, glutathione peroxidase 4, 4-hydroxynonenal, heme oxygenase-1, inducible nitric oxide synthase (iNOS), CD16, and arginase 1 (Arg1). The expression levels of iNOS and Arg1 in the spinal cord were visualized by immunofluorescence. ELISA was performed to measure the expression levels of IL-6, IL-1β, and TNF-α. Rat dorsal root ganglion (DRG) neurons and RMa-bm rat macrophages were treated with lipopolysaccharide under hypoxic conditions. The viability and iron content of the neurons were detected using Cell Counting Kit-8 and a specific probe, respectively. Flow cytometry and immunofluorescence were used to assess macrophage polarization. Chromatin immunoprecipitation was used to identify the binding of PRMT8 to the GDFN promoter.

RESULTS

Neuronal ferroptosis and M1 macrophage polarization were promoted, and PRMT8 expression was downregulated in SCI. PRMT8 overexpression exerted therapeutic effects on injured DRG neurons and RMa-bm cells. Moreover, PRMT8 overexpression inhibited ferroptosis and M1 macrophage polarization in rats with SCI. PRMT8 promoted GDNF expression by catalyzing H3K4 methylation. Knockdown of GDNF counteracted the therapeutic effects of PRMT8 overexpression.

CONCLUSION

Overexpression of PRMT8 may inhibit ferroptosis and M1 macrophage polarization by increasing GDNF expression, thereby alleviating SCI.

Protocatechuic aldehyde promotes the functional recovery of spinal cord injury by activating the Wnt/β-catenin signaling pathway

CONTEXT/OBJECTIVE

This study aimed to explore the anti-inflammatory and neuroprotective effects of protocatechuic aldehyde (PCA) in rats with spinal cord injury (SCI) and to clarify the molecular mechanisms underlying its pharmacological effects.

DESIGN

Male Sprague Dawley rat model of moderate spinal cord contusion were established.

SETTING

Third-class first-class hospital.

OUTCOME MEASURES

The Basso, Beattie, and Bresnahan scores and performance on the inclined plane test were evaluated. Histological analyses were performed via hematoxylin and eosin staining. Apoptosis in the spinal cord and neurons was detected by 5 terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling staining. Apoptotic factors (Bax, Bcl-2, and cleaved caspase-3) were also evaluated. INOS, IL-1β, IL-10, TNF-α, Wnt-3α, β-catenin, iBA-1, and NeuN were assessed by real-time reverse transcription-polymerase chain reaction (RT-PCR), western blotting (WB), and enzyme-linked immunosorbent assay. Cell viability and the immunofluorescence of IL-1β were measured in PC-12 cells.

RESULTS

Using WB and quantitative reverse transcription-PCR, we confirmed that PCA treatment activated the Wnt/β-catenin signaling axis in vivo and in vitro. Hematoxylin and eosin staining and hindlimb motor functional evaluation revealed that treatment with PCA improved tissue protection and functional recovery via the Wnt/β-catenin axis. The upregulation of TUNEL-positive cells, downregulation of neurons, elevated apoptosis-associated factors in rats, and increased apoptotic rates were observed in microglia and PC-12 after PCA application. Finally, PCA mitigated SCI-induced inflammation by targeting the Wnt/β-catenin axis.

CONCLUSION

This study provided preliminary evidence that PCA inhibits neuroinflammation and apoptosis through the Wnt/β-catenin pathway, thereby attenuating the secondary injury after SCI and promoting the regeneration of injured spinal tissues.

Current Advancements in Spinal Cord Injury Research—Glial Scar Formation and Neural Regeneration

Spinal cord injury (SCI) is a complex tissue injury resulting in permanent and degenerating damage to the central nervous system (CNS). Detrimental cellular processes occur after SCI, including axonal degeneration, neuronal loss, neuroinflammation, reactive gliosis, and scar formation. The glial scar border forms to segregate the neural lesion and isolate spreading inflammation, reactive oxygen species, and excitotoxicity at the injury epicenter to preserve surrounding healthy tissue. The scar border is a physicochemical barrier composed of elongated astrocytes, fibroblasts, and microglia secreting chondroitin sulfate proteoglycans, collogen, and the dense extra-cellular matrix. While this physiological response preserves viable neural tissue, it is also detrimental to regeneration. To overcome negative outcomes associated with scar formation, therapeutic strategies have been developed: the prevention of scar formation, the resolution of the developed scar, cell transplantation into the lesion, and endogenous cell reprogramming. This review focuses on cellular/molecular aspects of glial scar formation, and discusses advantages and disadvantages of strategies to promote regeneration after SCI.

Neuroprotective Effects of N-acetylserotonin and Its Derivative

N-acetylserotonin (NAS) is a chemical intermediate in melatonin biosynthesis. NAS and its derivative N-(2-(5-hydroxy-1H-indol-3-yl) ethyl)-2-oxopiperidine-3-carboxamide (HIOC) are potential therapeutic agents for traumatic brain injury, autoimmune encephalomyelitis, hypoxic-ischemic encephalopathy, and other diseases. Evidence shows that NAS and its derivative HIOC have neuroprotective properties, and can exert neuroprotective effects by inhibiting oxidative stress, anti-apoptosis, regulating autophagy dysfunction, and anti-inflammatory. In this review, we discussed the neuroprotective effects and related mechanisms of NAS and its derivative HIOC to provide a reference for follow-up research and applications.

A review of vascular endothelial growth factor and its potential to improve functional outcomes following spinal cord injury

Spinal cord injuries (SCI) are traumatic events with limited treatment options. Following injury, the lesion site experiences a drastic change to both its structure and vasculature which reduces its ability for tissue regeneration. Despite the lack of clinical options, researchers are investigating therapies to induce neuronal regeneration. Cell-based therapies have long been assessed in the context of SCI to promote neuronal protection and repair. Vascular endothelial growth factor (VEGF) not only demonstrates this ability, but also demonstrates angiogenic potential to promote blood vessel formation. While there have been numerous animal studies investigating VEGF, further research is still warranted to pinpoint its role following SCI. This review aims to discuss the literature surrounding the role of VEGF following SCI and its potential in promoting functional recovery.

Phosphoglycerate mutase 5 facilitates mitochondrial dysfunction and neuroinflammation in spinal tissues after spinal cord injury

Spinal cord injury (SCI) is a high incidence worldwide that causes a heavy physical and psychological burden to patients. It is urgent to further reveal the pathological mechanism and effective treatment of SCI. Mitochondrial dysfunction plays an important role in the disease progression of SCI. As a mitochondrial membrane protein, phosphoglycerate mutase 5 (PGAM5) is mainly involved in mitochondrial function and mitosis to modulate cellular physiological functions, but the roles of PGAM5 in spinal tissues remain to be unreported after SCI. The purpose of this study was to evaluate the role of PGAM5 in SCI mice and its relationship with neuroinflammation. The results showed that the mitochondrial membrane protein PGAM5 was involved in microglia activation after SCI, and PGAM5 deletion could improve mitochondrial dysfunction (including abnormal mtDNA, ATP synthases, and ATP levels, Cyt C expression, and ROS and rGSH levels) in spinal cord tissue after SCI, Arg1/iNOS mRNA level, iNOS expression, and pro-inflammatory cytokines TNF-α, IL-1β, and IL-18 levels. In vitro, H₂O₂ increased TNF-α, IL-1β, and IL-18 levels in BV2 cells, and PGAM5-sh and Nrf2 activators significantly reversed H₂O₂-induced iNOS expression and proinflammatory cytokine production. Furthermore, IP/Western blotting results revealed that PGAM5-sh treatment significantly reduced the interaction of PGAM5 with Nrf2 and enhanced the nuclear translocation of Nrf2 in BV2 cells. The data suggested that PGAM5 was involved in the cascade of oxidative stress and inflammatory response in microglia via facilitating the expression level of Nrf2 in the nucleus after SCI. It provided a reference for clarifying the pathological mechanism and therapeutic target of SCI.

Conditioned medium from bone marrow mesenchymal stem cells relieves spinal cord injury through suppression of Gal-3/NLRP3 and M1 microglia/macrophage polarization

The therapeutic effects of bone marrow mesenchymal stem cells (BMSCs) and their conditioned media have been well-documented. This study focused on the effects of BMSC-conditioned medium (BMSCcm) on spinal cord injury (SCI). To study the effects of BMSCcm on rat motor function, inflammatory response, and M1/M2 macrophage/microglial polarization, SCI model rats were treated with BMSCcm and vectors for overexpression of galectin-3 (Gal-3) or NLR family pyrin domain containing 3 (NLRP3). Treatment with BMSCcm reduced the expression of Gal-3 and NLRP3, alleviated the inflammatory response, suppressed M1 microglia/macrophage polarization, and triggered M2 microglia/macrophage polarization in SCI model rats. Meanwhile, overexpression of Gal-3 or NLRP3 counteracted the suppressive effect of BMSCcm on SCI. Moreover, during BMSCcm treatment, overexpression of Gal-3 promoted the expression of NLRP3, whereas overexpression of NLRP3 had no significant effect on the expression of Gal-3. Additionally, the effects of BMSCcm on macrophage/microglial polarization and the underlying molecular mechanisms were observed in vitro. This study demonstrated that BMSCcm alleviates SCI by suppressing the expression of Gal-3 and NLRP3.

Inhibition of A1 Astrocytes and Activation of A2 Astrocytes for the Treatment of Spinal Cord Injury

Spinal cord injury (SCI) is a serious injury to the central nervous system that causes significant physical and psychological trauma to the patient. SCI includes primary spinal cord injuries and secondary spinal cord injuries. The secondary injury refers to the pathological process or reaction after the primary injury. Although SCI has always been thought to be an incurable injury, the human nerve has the ability to repair itself after an injury. However, the reparability is limited because glial scar formation impedes functional recovery. There is a type of astrocyte that can differentiate into two forms of reactive astrocytes known as 'A1' and 'A2' astrocytes. A1 astrocytes release cytotoxic chemicals that cause neurons and oligodendrocytes to die and perform a harmful role. A2 astrocytes can produce neurotrophic factors and act as neuroprotectors. This article discusses ways to block A1 astrocytes while stimulating A2 astrocytes to formulate a new treatment for spinal cord injury.

Upregulation of RAB7 is related to neuronal pyroptosis after spinal cord injury in rats

Rab7 belongs to the Ras small GTPase superfamily, and abnormal expression of Rab7 can cause neuropathy and lipid metabolism diseases. Studies have shown that Rab7 plays a crucial role in the inner membrane translocase. However, the role of Rab7 in the regulatory mechanisms of cell survival in spinal cord injury remains unknown. We used a rat spinal cord injury (SCI) model to explore the cellular localization and expression of Rab7 after SCI in this study. Western blot analysis showed that Rab7 was expressed in the spinal cord tissue. On the first day, it significantly increased and peaked after SCI on the third day. Furthermore, western blotting also demonstrated that pyroptosis-related protein Gasdermin D (GSDMD), Caspase-1, apoptosis-associated speck-like protein (ASC) expression peaked after the third-day post-injury. Importantly, the immunohistochemistry analysis revealed that Rab7 was completely colocalized with ASC in neurons after SCI. These results suggested that Rab7 was colocalized with NeuN and ASC, involved in the pyroptosis of neurons, and closely related to the spinal cord after injury.

Applications of chitosan-based biomaterials: From preparation to spinal cord injury neuroprosthetic treatment

Spinal cord injury (SCI)-related disabilities are a serious problem in the modern society. Further, the treatment of SCI is highly challenging and is urgently required in clinical practice. Research on nerve tissue engineering is an emerging approach for improving the treatment outcomes of SCI. Chitosan (CS) is a cationic polysaccharide derived from natural biomaterials. Chitosan has been found to exhibit excellent biological properties, such as nontoxicity, biocompatibility, biodegradation, and antibacterial activity. Recently, chitosan-based biomaterials have attracted significant attention for SCI repair in nerve tissue engineering applications. These studies revealed that chitosan-based biomaterials have various functions and mechanisms to promote SCI repair, such as promoting neural cell growth, guiding nerve tissue regeneration, delivering nerve growth factors, and as a vector for gene therapy. Chitosan-based biomaterials have proven to have excellent potential for the treatment of SCI. This review aims to introduce the recent advances in chitosan-based biomaterials for SCI treatment and to highlight the prospects for further application.

Spinal cord tissue engineering using human primary neural progenitor cells and astrocytes

Neural progenitor cell (NPC) transplantation is a promising approach for repairing spinal cord injury (SCI). However, cell survival, maturation and integration after transplantation are still major challenges. Here, we produced a novel centimeter-scale human spinal cord neural tissue (hscNT) construct with human spinal cord neural progenitor cells (hscNPCs) and human spinal cord astrocytes (hscAS) on a linearly ordered collagen scaffold (LOCS). The hscAS promoted hscNPC adhesion, survival and neurite outgrowth on the LOCS, to form a linearly ordered spinal cord-like structure consisting of mature neurons and glia cells. When transplanted into rats with SCI, the hscNT created a favorable microenvironment by inhibiting inflammation and glial scar formation, and promoted neural and vascular regeneration. Notably, the hscNT promoted neural circuit reconstruction and motor functional recovery. Engineered human spinal cord implants containing astrocytes and neurons assembled on axon guidance scaffolds may therefore have potential in the treatment of SCI.

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.

The role of mitochondrial energy metabolism in neuroprotection and axonal regeneration after spinal cord injury

Mitochondrial dysfunction occurs in the early stage of axonal degeneration after spinal cord injury and involves oxidative stress, energy deficiency, imbalance of mitochondrial dynamics, etc., which play a key role in axonal degeneration and regeneration under physiological and pathological conditions. Failure of axonal regeneration can lead to long-term structural and functional damage. Several recent studies have shown that improved mitochondrial energy metabolism provides conditions for axonal regeneration and central nervous system repair. Here, we describe the role of mitochondrial energy metabolism in neuroprotection and axonal regeneration after spinal cord injury and review recent advances in targeted mitochondrial therapy.

Effectiveness of robotic-assisted gait training on cardiopulmonary fitness and exercise capacity for incomplete spinal cord injury: A systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

To determine the effects of robotic-assisted gait training on cardiopulmonary fitness and exercise capacity for people with incomplete spinal cord injury.

METHODS

PubMed, Embase, Web of Science, PEDro, CENTRAL and CINAHL were searched from inception until September 4, 2022. Randomized controlled trials that evaluated the effects of robotic-assisted gait training on cardiopulmonary fitness and exercise capacity for individuals with incomplete spinal cord injury were selected. Mean differences (MD) with 95% confidence interval (CI) were calculated. The methodological quality was evaluated by the Cochrane Risk of Bias 2.0 tool. Subgroup analyses were conducted according to the time since injury.

RESULTS

In total 19 studies involving 770 patients were eligible for analysis. Individuals with acute incomplete spinal cord injury in robotic-assisted gait training groups showed significantly greater improvements in 6-minute walking test (MD 53.32; 95% CI 33.49 to 73.15; P < 0.001), lower extremity motor scale (MD 5.22; 95% CI 3.63 to 6.80; P < 0.001) and walking index for spinal cord injury II (MD 3.18; 95% CI 1.34 to 5.02; P < 0.001). Robotic-assisted gait training improved peak oxygen consumption to a greater degree for chronic incomplete spinal cord injury patients (MD 4.90; 95% CI 0.96 to 8.84; P = 0.01).

CONCLUSION

Robot-assisted gait training may be a feasible and effective intervention in terms of cardiopulmonary fitness and exercise capacity for individuals with incomplete spinal cord injury.

Hydralazine plays an immunomodulation role of pro-regeneration in a mouse model of spinal cord injury

Spinal cord injury (SCI) results in severe motor and sensory dysfunction with no effective therapy. Spinal cord debris (sp) from injured spinal cord evokes secondary SCI continuously. We and other researchers have previously clarified that it is mainly bone marrow derived macrophages (BMDMs) infiltrating in the lesion epicenter to clear sp, rather than local microglia. Unfortunately, the pro-inflammatory phenotype of these infiltrating BMDMs is predominant which impairs wound healing. Hydralazine, as a potent vasodilator and scavenger of acrolein, has protective effects in many diseases. Hydralazine is also confirmed to promote motor function and hypersensitivity in SCI rats through scavenging acrolein. However, few studies have explored the effects of hydralazine on immunomodulation, as well as spontaneous pain and emotional response, the important syndromes in clinical patients. It remains unclear whether hydralazine affects infiltrating BMDMs after SCI. In this study, we targeted BMDMs to explore the influence of hydralazine on immune cells in a mouse model of SCI, and also investigated the contribution of polarized BMDMs to hydralazine-induced neurological function recovery after SCI in male mice. The adult male mice underwent T10 spinal cord compression. The results showed that in addition to improving motor function and hypersensitivity, hydralazine relieved SCI-induced spontaneous pain and emotional response, which is a newly discovered function of hydralazine. Hydralazine inhibited the recruitments of pro-inflammatory BMDMs and educated infiltrated BMDMs to a more reparative phenotype involving in multiple biological processes associated with SCI pathology, including immune/inflammation response, neurogenesis, lipid metabolism, oxidative stress, fibrosis formation, and angiogenesis, etc. As an overall effect, hydralazine-treated BMDMs loaden with sp partially rescued neurological function after SCI. It is concluded that hydralazine plays an immunomodulation role of educating pro-inflammatory BMDMs to a more reparative phenotype; and hydralazine-educated BMDMs contribute to hydralazine-induced improvement of neurological function in SCI mice, which provides support for drug and cell treatment options for SCI therapy.

The polarization of microglia and infiltrated macrophages in the injured mice spinal cords: a dynamic analysis

Background

Following spinal cord injury (SCI), a large number of peripheral monocytes infiltrate into the lesion area and differentiate into macrophages (Mø). These monocyte-derived Mø are very difficult to distinguish from the local activated microglia (MG). Therefore, the term Mø/MG are often used to define the infiltrated Mø and/or activated MG. It has been recognized that pro-inflammatory M1-type Mø/MG play "bad" roles in the SCI pathology. Our recent research showed that local M1 cells are mainly CD45^-/lowCD68⁺CD11b⁺ in the subacute stage of SCI. Thus, we speculated that the M1 cells in injured spinal cords mainly derived from MG rather than infiltrating Mø. So far, their dynamics following SCI are not yet entirely clear.

Methods

Female C57BL/6 mice were used to establish SCI model, using an Infinite Horizon impactor with a 1.3 mm diameter rod and a 50 Kdynes force. Sham-operated (sham) mice only underwent laminectomy without contusion. Flow cytometry and immunohistofluorescence were combined to analyze the dynamic changes of polarized Mø and MG in the acute (1 day), subacute (3, 7 and 14 days) and chronic (21 and 28 days) phases of SCI.

Results

The total Mø/MG gradually increased and peaked at 7 days post-injury (dpi), and maintained at high levels 14, 21 and 28 dpi. Most of the Mø/MG were activated, and the Mø increased significantly at 1 and 3 dpi. However, with the pathological process, activated MG increased nearly to 90% at 7, 14, 21 and 28 dpi. Both M1 and M2 Mø were increased significantly at 1 and 3 dpi. However, they decreased to very low levels from 7 to 28 dpi. On the contrary, the M2-type MG decreased significantly following SCI and maintained at a low level during the pathological process.

Mechanism of spinal cord injury regeneration and the effect of human neural stem cells-secretome treatment in rat model

BACKGROUND

Globally, complete neurological recovery of spinal cord injury (SCI) is still less than 1%, and 90% experience permanent disability. The key issue is that a pharmacological neuroprotective-neuroregenerative agent and SCI regeneration mechanism have not been found. The secretomes of stem cell are an emerging neurotrophic agent, but the effect of human neural stem cells (HNSCs) secretome on SCI is still unclear.

AIM

To investigate the regeneration mechanism of SCI and neuroprotective-neuroregenerative effects of HNSCs-secretome on subacute SCI post-laminectomy in rats.

METHODS

An experimental study was conducted with 45 Rattus norvegicus, divided into 15 normal, 15 control (10 mL physiologic saline), and 15 treatment (30 μL HNSCs-secretome, intrathecal T10, three days post-traumatic). Locomotor function was evaluated weekly by blinded evaluators. Fifty-six days post-injury, specimens were collected, and spinal cord lesion, free radical oxidative stress (F2-Isoprostanes), nuclear factor-kappa B (NF-κB), matrix metallopeptidase 9 (MMP9), tumor necrosis factor-alpha (TNF-α), interleukin-10 (IL-10), transforming growth factor-beta (TGF-β), vascular endothelial growth factor (VEGF), B cell lymphoma-2 (Bcl-2), nestin, brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF) were analyzed. The SCI regeneration mechanism was analyzed using partial least squares structural equation modeling (PLS SEM).

RESULTS

HNSCs-secretome significantly improved locomotor recovery according to Basso, Beattie, Bresnahan (BBB) scores and increased neurogenesis (nestin, BDNF, and GDNF), neuroangiogenesis (VEGF), anti-apoptotic (Bcl-2), anti-inflammatory (IL-10 and TGF-β), but decreased pro-inflammatory (NF-κB, MMP9, TNF-α), F2-Isoprostanes, and spinal cord lesion size. The SCI regeneration mechanism is valid by analyzed outer model, inner model, and hypothesis testing in PLS SEM, started with pro-inflammation followed by anti-inflammation, anti-apoptotic, neuroangiogenesis, neurogenesis, and locomotor function.

CONCLUSION

HNSCs-secretome as a potential neuroprotective-neuroregenerative agent for the treatment of SCI and uncover the SCI regeneration mechanism.

Molecular Aspects of Hypoxic Stress Effects in Chronic Ethanol Exposure of Neuronal Cells

Experimental models of a clinical, pathophysiological context are used to understand molecular mechanisms and develop novel therapies. Previous studies revealed better outcomes for spinal cord injury chronic ethanol-consuming patients. This study evaluated cellular and molecular changes in a model mimicking spinal cord injury (hypoxic stress induced by treatment with deferoxamine or cobalt chloride) in chronic ethanol-consuming patients (ethanol-exposed neural cultures (SK-N-SH)) in order to explain the clinical paradigm of better outcomes for spinal cord injury chronic ethanol-consuming patients. The results show that long-term ethanol exposure has a cytotoxic effect, inducing apoptosis. At 24 h after the induction of hypoxic stress (by deferoxamine or cobalt chloride treatments), reduced ROS in long-term ethanol-exposed SK-N-SH cells was observed, which might be due to an adaptation to stressful conditions. In addition, the HIF-1α protein level was increased after hypoxic treatment of long-term ethanol-exposed cells, inducing fluctuations in its target metabolic enzymes proportionally with treatment intensity. The wound healing assay demonstrated that the cells recovered after stress conditions, showing that the ethanol-exposed cells that passed the acute step had the same proliferation profile as the cells unexposed to ethanol. Deferoxamine-treated cells displayed higher proliferative activity than the control cells in the proliferation-migration assay, emphasizing the neuroprotective effect. Cells have overcome the critical point of the alcohol-induced traumatic impact and adapted to ethanol (a chronic phenomenon), sustaining the regeneration process. However, further experiments are needed to ensure recovery efficiency is more effective in chronic ethanol exposure.

Depression mediated the relationships between precentral-subcortical causal links and motor recovery in spinal cord injury patients

Depression after brain damage may impede the motivation and consequently influence the motor recovery after spinal cord injury (SCI); however, the neural mechanism underlying the psychological effects remains unclear. This study aimed to examine the casual connectivity changes of the emotion-motivation-motor circuit and the potential mediating effects of depression on motor recovery after SCI. Using the resting-state functional magnetic resonance imaging data of 35 SCI patients (24 good recoverers, GR and 11 poor recoverers, PR) and 32 healthy controls (HC), the results from the conditional Granger causality (GC) analysis demonstrated that the GR group exhibited sparser emotion-motivation-motor GC network compared with the HC and PR groups, though the in-/out-degrees of the emotion subnetwork and the motor subnetwork were relatively balanced in the HC and GR group. The PR group showed significantly inhibitory causal links from amygdala to supplementary motor area and from precentral gyrus to nucleus accumbens compared with GR group. Further mediation analysis revealed the indirect effect of the 2 causal connections on motor function recovery via depression severity. Our findings provide further evidence of abnormal causal connectivity in emotion-motivation-motor circuit in SCI patients and highlight the importance of emotion intervention for motor function recovery after SCI.

Ang-(1-7)/MasR axis promotes functional recovery after spinal cord injury by regulating microglia/macrophage polarization

BACKGROUND

Inflammatory response is an essential part of secondary injury after spinal cord injury (SCI). During this period, the injury may be exacerbated through the release of a large number of inflammatory factors and the polarization of infiltrating macrophages and microglia towards M1. Ang-(1-7), mainly generated by Ang II via angiotensin-converting enzyme 2 (ACE2), can specifically bind to the G protein-coupled receptor Mas (MasR) and plays an important role in regulating inflammation and alleviating oxidative stress.

METHODS

We aimed to investigate whether activating the Ang-(1-7)/MasR axis in rats after SCI can regulate local neuroinflammation to achieve functional recovery and obtain its potential mechanism. MasR expression of bone marrow-derived macrophages was determined by Western blot. Immunofluorescence, Western blot, Flow cytometry, and RT-qPCR were applied to evaluate the polarization of Ang-(1-7) on macrophages and the regulation of inflammatory cytokines. Previous evaluation of the spinal cord and bladder after SCI was conducted by hematoxylin-eosin staining, Basso, Beattie, and Bresnahan (BBB) score, inclined plate test, electrophysiology, and catwalk were used to evaluate the functional recovery of rats.

RESULTS

MasR expression increased in macrophages under inflammatory conditions and further elevated after Ang-(1-7) treatment. Both in vivo and in vitro results confirmed that Ang-(1-7) could regulate the expression of inflammatory cytokines by down-regulating proinflammatory cytokines and up-regulating anti-inflammatory cytokines, and bias the polarization direction of microglia/macrophages to M2 phenotypic. After SCI, Ang-(1-7) administration in situ led to better histological and functional recovery in rats, and this recovery at least partly involved the TLR4/NF-κB signaling pathway.

CONCLUSION

As shown in our data, activating Ang-(1-7)/MasR axis can effectively improve the inflammatory microenvironment after spinal cord injury, promote the polarization of microglia/macrophages towards the M2 phenotype, and finally support the recovery of motor function. Therefore, we suggest using Ang-(1-7) as a feasible treatment strategy for spinal cord injury to minimize the negative consequences of the inflammatory microenvironment after spinal cord injury.

Electrical stimulation for the treatment of spinal cord injuries: A review of the cellular and molecular mechanisms that drive functional improvements

Spinal cord injury (SCI) is a devastating condition that causes severe loss of motor, sensory and autonomic functions. Additionally, many individuals experience chronic neuropathic pain that is often refractory to interventions. While treatment options to improve outcomes for individuals with SCI remain limited, significant research efforts in the field of electrical stimulation have made promising advancements. Epidural electrical stimulation, peripheral nerve stimulation, and functional electrical stimulation have shown promising improvements for individuals with SCI, ranging from complete weight-bearing locomotion to the recovery of sexual function. Despite this, there is a paucity of mechanistic understanding, limiting our ability to optimize stimulation devices and parameters, or utilize combinatorial treatments to maximize efficacy. This review provides a background into SCI pathophysiology and electrical stimulation methods, before exploring cellular and molecular mechanisms suggested in the literature. We highlight several key mechanisms that contribute to functional improvements from electrical stimulation, identify gaps in current knowledge and highlight potential research avenues for future studies.

Construction of a searchable database for gene expression changes in spinal cord injury experiments

Spinal cord injury (SCI) is a debilitating disease resulting in an estimated 18,000 new cases in the United States on an annual basis. Significant behavioral research on animal models has led to a large amount of data, some of which has been catalogued in the Open Data Commons for Spinal Cord Injury (ODC-SCI). More recently, high throughput sequencing experiments have been utilized to understand molecular mechanisms associated with SCI, with nearly 6,000 samples from over 90 studies available in the Sequence Read Archive. However, to date, no resource is available for efficiently mining high throughput sequencing data from SCI experiments. Therefore, we have developed a protocol for processing RNA-Seq samples from high-throughput sequencing experiments related to SCI resulting in both raw and normalized data that can be efficiently mined for comparisons across studies as well as homologous discovery across species. We have processed 1,196 publicly available RNA-seq samples from 50 bulk RNA-Seq studies across nine different species, resulting in an SQLite database that can be used by the SCI research community for further discovery. We provide both the database as well as a web-based front-end that can be used to query the database for genes of interest, differential gene expression, genes with high variance, and gene set enrichments.

MicroRNAs in spinal cord injury: A narrative review

Spinal cord injury (SCI) is a global medical problem with high disability and mortality rates. At present, the diagnosis and treatment of SCI are still lacking. Spinal cord injury has a complex etiology, lack of diagnostic methods, poor treatment effect and other problems, which lead to the difficulty of spinal cord regeneration and repair, and poor functional recovery. Recent studies have shown that gene expression plays an important role in the regulation of SCI repair. MicroRNAs (miRNAs) are non-coding RNA molecules that target mRNA expression in order to silence, translate, or interfere with protein synthesis. Secondary damage, such as oxidative stress, apoptosis, autophagy, and inflammation, occurs after SCI, and differentially expressed miRNAs contribute to these events. This article reviews the pathophysiological mechanism of miRNAs in secondary injury after SCI, focusing on the mechanism of miRNAs in secondary neuroinflammation after SCI, so as to provide new ideas and basis for the clinical diagnosis and treatment of miRNAs in SCI. The mechanisms of miRNAs in neurological diseases may also make them potential biomarkers and therapeutic targets for spinal cord injuries.

Current Status of Polysaccharides-Based Drug Delivery Systems for Nervous Tissue Injuries Repair

Neurological disorders affecting both CNS and PNS still represent one of the most critical and challenging pathologies, therefore many researchers have been focusing on this field in recent decades. Spinal cord injury (SCI) and peripheral nerve injury (PNI) are severely disabling diseases leading to dramatic and, in most cases, irreversible sensory, motor, and autonomic impairments. The challenging pathophysiologic consequences involved in SCI and PNI are demanding the development of more effective therapeutic strategies since, as yet, a therapeutic strategy that can effectively lead to a complete recovery from such pathologies is not available. Drug delivery systems (DDSs) based on polysaccharides have been receiving more and more attention for a wide range of applications, due to their outstanding physical-chemical properties. This review aims at providing an overview of the most studied polysaccharides used for the development of DDSs intended for the repair and regeneration of a damaged nervous system, with particular attention to spinal cord and peripheral nerve injury treatments. In particular, DDSs based on chitosan and their association with alginate, dextran, agarose, cellulose, and gellan were thoroughly revised.

Photobiomodulation promotes spinal cord injury repair by inhibiting macrophage polarization through lncRNA TUG1-miR-1192/TLR3 axis

BACKGROUND

Secondary spinal cord injury (SCI) often causes the aggravation of inflammatory reaction and nerve injury, which affects the recovery of motor function. Bone-marrow-derived macrophages (BMDMs) were recruited to the injured area after SCI, and the M1 polarization is the key process for inducing inflammatory response and neuronal apoptosis. We previously showed that photobiomodulation (PBM) can inhibit the polarization of M1 phenotype of BMDMs and reduce inflammation, but the underlying mechanisms are unclear. The purpose of this study is to explore the potential target and mechanism of PBM in treating SCI.

METHODS

Transcriptome sequencing and bioinformatics analysis showed that long noncoding RNA taurine upregulated gene 1 (lncRNA TUG1) was a potential target of PBM. The expression and specific mechanism of lncRNA TUG1 were detected by qPCR, immunofluorescence, flow cytometry, western blotting, fluorescence in situ hybridization, and luciferase assay. The Basso mouse scale (BMS) and gait analysis were used to evaluate the recovery of motor function in mice.

RESULTS

Results showed that lncRNA TUG1 may be a potential target of PBM, regulating the polarization of BMDMs, inflammatory response, and the axial growth of DRG. Mechanistically, TUG1 competed with TLR3 for binding to miR-1192 and attenuated the inhibitory effect of miR-1192 on TLR3. This effect protected TLR3 from degradation, enabling the high expression of TLR3, which promoted the activation of downstream NF-κB signal and the release of inflammatory cytokines. In vivo, PBM treatment could reduce the expression of TUG1, TLR3, and inflammatory cytokines and promoted nerve survival and motor function recovery in SCI mice.

CONCLUSIONS

Our study clarified that the lncRNA TUG1/miR-1192/TLR3 axis is an important pathway for PBM to inhibit M1 macrophage polarization and inflammation, which provides theoretical support for its clinical application in patients with SCI.

Research progress of hydrogels as delivery systems and scaffolds in the treatment of secondary spinal cord injury

Secondary spinal cord injury (SSCI) is the second stage of spinal cord injury (SCI) and involves vasculature derangement, immune response, inflammatory response, and glial scar formation. Bioactive additives, such as drugs and cells, have been widely used to inhibit the progression of secondary spinal cord injury. However, the delivery and long-term retention of these additives remain a problem to be solved. In recent years, hydrogels have attracted much attention as a popular delivery system for loading cells and drugs for secondary spinal cord injury therapy. After implantation into the site of spinal cord injury, hydrogels can deliver bioactive additives in situ and induce the unidirectional growth of nerve cells as scaffolds. In addition, physical and chemical methods can endow hydrogels with new functions. In this review, we summarize the current state of various hydrogel delivery systems for secondary spinal cord injury treatment. Moreover, functional modifications of these hydrogels for better therapeutic effects are also discussed to provide a comprehensive insight into the application of hydrogels in the treatment of secondary spinal cord injury.

Architecture-Engineered Electrospinning Cascade Regulates Spinal Microenvironment to Promote Nerve Regeneration

The inflammatory cascade after spinal cord injury (SCI) causes necrotizing apoptosis of local stem cells, which limits nerve regeneration. Therefore, coordinating the inflammatory immune response and neural stem cell (NSC) functions is key to promoting the recovery of central nervous system function. In this study, a hydrogel "perfusion" system and electrospinning technology are integrated, and a "concrete" composite support for the repair of nerve injuries is built. The hydrogel's hydrophilic properties activate macrophage integrin receptors to mediate polarization into anti-inflammatory subtypes and cause a 10% increase in polarized M2 macrophages, thus reprogramming the SCI immune microenvironment. Programmed stromal cell-derived factor-1α and brain-derived neurotrophic factor released from the composite increase recruitment and neuronal differentiation of NSCs by approximately four- and twofold, respectively. The fiber system regulates the SCI immune inflammatory microenvironment, recruits endogenous NSCs, promotes local blood vessel germination and maturation, and improves nerve function recovery in a rat SCI model. In conclusion, the engineering fiber composite improves the local inflammatory response. It promotes nerve regeneration through a hydrophilic programmed cytokine-delivery system, which further improves and supplements the immune response mechanism regulated by the inherent properties of the biomaterial. The new fiber composite may serve as a new treatment approach for SCI.

Adalimumab combined with erythropoietin improves recovery from spinal cord injury by suppressing microglial M1 polarization-mediated neural inflammation and apoptosis

OBJECTIVE

Adalimumab (ADM), a humanized antibody against tumour necrosis factor (TNF), is widely applied in treating inflammatory and autoimmune diseases, but its usage in spinal cord injury (SCI) is rarely reported. Hence, this study aimed to explore the effect of ADM with or without erythropoietin (EPO) on microglial polarization, neuroinflammation, neural apoptosis, and functional recovery in SCI.

METHODS

Primary microglia were stimulated with lipopolysaccharide (LPS) and then treated with ADM, EPO, or ADM combined with EPO. Then, primary neurons were incubated in the microglial culture medium. SCI rats were established and then treated with ADM, EPO or ADM combined with EPO.

RESULTS

ADM suppressed LPS-induced microglial M1 polarization, as reflected by downregulated iNOS and CD86 expression, and neuroinflammation, as reflected by decreased TNF-α, IL-1β, and IL-6 expression, in a dose-dependent manner. Moreover, ADM inhibited microglia-induced neural apoptosis, as reflected by TUNEL assay results and the expression of apoptotic markers (C-Caspase3 and Bcl2), in a dose-dependent manner. EPO monotherapy displayed an effect similar to that of ADM monotherapy. Furthermore, ADM combined with EPO therapy exhibited greater effects than either monotherapy in terms of inhibiting microglial M1 polarization, neuroinflammation, and neural apoptosis. In vivo experiments confirmed the findings of the in vitro experiments and showed that ADM combined with EPO improved SCI functional recovery and neural injury compared with monotherapy.

CONCLUSION

ADM combined with EPO improves recovery from SCI by suppressing microglial M1 polarization-mediated neural inflammation and apoptosis.

Induced pluripotent stem cells as natural biofactories for exosomes carrying miR-199b-5p in the treatment of spinal cord injury

Background: Induced pluripotent stem cells-derived exosomes (iPSCs-Exo) can effectively treat spinal cord injury (SCI) in mice. But the role of iPSCs-Exo in SCI mice and its molecular mechanisms remain unclear. This research intended to study the effects and molecular mechanism of iPSCs-Exo in SCI mice models. Methods: The feature of iPSCs-Exo was determined by transmission electron microscope (TEM), nanoparticle tracking analysis (NTA), and western blot. The effects of iPSCs-Exo in the SCI mice model were evaluated by Basso Mouse Scale (BMS) scores and H&E staining. The roles of iPSCs-Exo and miR-199b-5p in LPS-treated BMDM were verified by immunofluorescence, RT-qPCR, and Cytokine assays. The target genes of miR-199b-5p were identified, and the function of miR-199b-5p and its target genes on LPS-treated BMDM was explored by recuse experiment. Results: iPSCs-Exo improved motor function in SCI mice model in vivo, shifted the polarization from M1 macrophage to M2 phenotype, and regulated related inflammatory factors expression to accelerate the SCI recovery in LPS-treated BMDM in vitro. Meanwhile, miR-199b-5p was a functional player of iPSCs-Exo, which could target hepatocyte growth factor (Hgf). Moreover, miR-199b-5p overexpression polarized M1 macrophage into M2 phenotype and promoted neural regeneration in SCI. The rescue experiments confirmed that miR-199b-5p induced macrophage polarization and SCI recovery by regulating Hgf and Phosphoinositide 3-kinase (PI3K) signaling pathways. Conclusion: The miR-199b-5p-bearing iPSCs-Exo might become an effective method to treat SCI.