OBJECTIVE: To investigate the effects of removing microglia from spinal cord on nerve repair and functional recovery after spinal cord injury (SCI) in mice. METHODS: Thirty-nine 6-week-old female C57BL/6 mice were randomly divided into control group ( n=12), SCI group ( n=12), and PLX3397+SCI group ( n=15). The PLX3397+SCI group received continuous feeding of PLX3397, a colony-stimulating factor 1 receptor inhibitor, while the other two groups were fed a standard diet. After 14 days, both the SCI group and the PLX3397+SCI group were tested for ionized calcium binding adapter molecule 1 (Iba1) to confirm that the PLX3397+SCI group had completely depleted the spinal cord microglia. The SCI model was then prepared by clamping the spinal cord in both the SCI group and the PLX3397+SCI group, while the control group underwent laminectomy. Preoperatively and at 1, 3, 7, 14, 21, and 28 days postoperatively, the Basso Mouse Scale (BMS) was used to assess the hind limb function of mice in each group. At 28 days, a footprint test was conducted to observe the gait of the mice. After SCI, spinal cord tissue from the injury site was taken, and Iba1 immunofluorescence staining was performed at 7 days to observe the aggregation and proliferation of microglia in the spinal cord. HE staining was used to observe the formation of glial scars at the injury site at 28 days; glial fibrillary acidic protein (GFAP) immunofluorescence staining was applied to astrocytes to assess the extent of the injured area; neuronal nuclei antigen (NeuN) immunofluorescence staining was used to evaluate neuronal survival. And 5-hydroxytryptamine (5-HT) immunofluorescence staining was performed to assess axonal survival at 60 days. RESULTS: All mice survived until the end of the experiment. Immunofluorescence staining revealed that the microglia in the spinal cord of the PLX3397+SCI group decreased by more than 95% compared to the control group after 14 days of continuous feeding with PLX3397 ( P<0.05). Compared to the control group, the BMS scores in the PLX3397+SCI group and the SCI group significantly decreased at different time points after SCI ( P<0.05). Moreover, the PLX3397+SCI group showed a further decrease in BMS scores compared to the SCI group, and exhibited a dragging gait. The differences between the two groups were significant at 14, 21, and 28 days ( P<0.05). HE staining at 28 days revealed that the SCI group had formed a well-defined and dense gliotic scar, while the PLX3397+SCI group also developed a gliotic scar, but with a more blurred and loose boundary. Immunofluorescence staining revealed that the number of microglia near the injury center at 7 days increased in the SCI group than in the control group, but the difference between groups was not significant ( P>0.05). In contrast, the PLX3397+SCI group showed a significant reduction in microglia compared to both the control and SCI groups ( P<0.05). At 28 days after SCI, the area of spinal cord injury in the PLX3397+SCI group was significantly larger than that in SCI group ( P<0.05); the surviving neurons significantly reduced compared with the control group and SCI group ( P<0.05). The axonal necrosis and retraction at 60 days after SCI were more obvious. CONCLUSION The removal of microglia in the spinal cord aggravate the tissue damage after SCI and affecte the recovery of motor function in mice, suggesting that microglia played a neuroprotective role in SCI.
Animals ; Spinal Cord Injuries/surgery* ; Microglia/pathology* ; Female ; Mice ; Mice, Inbred C57BL ; Nerve Regeneration/drug effects* ; Spinal Cord/pathology* ; Pyrroles/administration & dosage* ; Aminopyridines/administration & dosage* ; Recovery of Function ; Disease Models, Animal ; Calcium-Binding Proteins/metabolism* ; Receptors, Granulocyte-Macrophage Colony-Stimulating Factor/antagonists & inhibitors* ; Microfilament Proteins/metabolism* ; Glial Fibrillary Acidic Protein/metabolism*

In recent years, the study of single-cell transcriptome sequencing technology in the heterogeneity of astrocytes (astrocytes) after spinal cord injury (SCI) has provided new perspectives on post-traumatic nerve regeneration and repair. To provide a review on the research progress of single-cell sequencing technology in astrocytes after spinal cord injury (SCI), and to more comprehensively and deeply elaborate the application of single-cell sequencing technology in the field of astrocytes after SCI. Single-cell sequencing technology can analyse the transcriptomes of individual cells in a high-throughput manner, thus revealing fine differences in cell types and states. By using single-cell sequencing technology, the heterogeneity of astrocytes after SCI and their association with nerve regeneration and repair were revealed. In conclusion, the application of single-cell sequencing technology provides an important tool to reveal the heterogeneity of astrocytes after SCI, to further explore the mechanisms of astrocytes in SCI, and to develop intervention strategies targeting their regulatory mechanisms in order to improve the therapeutic efficacy of SCI. The discovery of changes in astrocyte transcriptome dynamics has improved researchers' understanding of spinal cord injury lesion progression and provided new insights into the treatment of spinal cord injury at different time points. To date, all of these findings need to be validated by more basic research and sufficient clinical trials. In the future, single-cell sequencing technology, through interdisciplinary collaboration with bioinformatics, computer science, tissue engineering, and clinical medicine, is expected to open a new window for the treatment of spinal cord injury.
Spinal Cord Injuries/metabolism* ; Astrocytes/cytology* ; Single-Cell Analysis/methods* ; Humans ; Animals ; Transcriptome ; Nerve Regeneration

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

Spinal cord injury is a severe central nervous system disease, which will cause a series of complex pathophysiological changes and activate a variety of signaling pathways including Notch signaling. Studies have evidenced that activation of the Notch signaling pathway is not conducive to nerve repair and symptom improvement after spinal cord injury. Its mechanisms include inhibiting neuronal differentiation and axon regeneration, promoting reactive astrocyte proliferation, promoting M1 macrophage polarization and the release of proinflammatory factors, and inhibiting angiogenesis. Therefore, it has become a promising therapeutic strategy to inhibit Notch signal as a target in the treatment of spinal cord injury. In recent years, some researchers have used drugs, cell transplantation or genetic modification to regulate Notch signaling, which can promote the recovery of nerve function after spinal cord injury, thereby providing new treatment strategies for the treatment of spinal cord injury. This article will summarize the mechanism of Notch signaling pathway in spinal cord injury, and at the same time review the research progress in the treatment of spinal cord injury by modulating Notch signaling pathway in recent years, so as to provide new research ideas for further exploring new strategies for spinal cord injury.
Axons/metabolism* ; Cell Transplantation ; Humans ; Nerve Regeneration ; Signal Transduction/genetics* ; Spinal Cord/metabolism* ; Spinal Cord Injuries/metabolism*

Spinal cord injury is a highly disabled neurological disease, and there is still a lack of effective treatments. Studies have proved that olfactory ensheathing cells are one of the ideal seed cells for promoting nerve regeneration after spinal cord injury. Olfactory ensheathing cells can promote axonal germination and elongation through secretion, interaction with astrocytes, regulation of inflammatory reaction, migration characteristics, myelination, anti-oxidation, lipid regulation and other channels. Thus olfactory ensheathing cells play the role of neuroprotection and nerve repair. In recent years, some studies have used bioengineering, tissue engineering, reprogramming and other technologies to enhance the efficacy of olfactoryensheathing cells from different aspects, thereby providing new therapeutic strategies for optimizing the cell therapy of spinal cord injury. This article will summarize the mechanism of olfactory ensheathing cells in repairing spinal cord injury, and review the progress of optimizing strategy of olfactory ensheathing cells in treating spinal cord injury recently, so as to provide new research ideas for the further developing the repair potential of olfactory ensheathing cells and optimize the cell therapy effect of spinal cord injury.
Cell Transplantation ; Humans ; Nerve Regeneration ; Spinal Cord Injuries/therapy*

Perineuronal nets (PNNs) is a complex network composed of highly condensed extracellular matrix molecules surrounding neurons. It plays an important role in maintaining the performance of neurons and protecting them from harmful substances. However, after spinal cord injury, PNNs forms a physical barrier that surrounds the neuron and limits neuroplasticity, impedes axonal regeneration and myelin formation, and promotes local neuroinflammatory uptake. This paper mainly describes the composition and function of PNNs of neurons and its regulatory effects on axonal regeneration, myelin formation and neuroinflammation after spinal cord injury.
Axons ; Extracellular Matrix ; Humans ; Nerve Regeneration ; Neuronal Plasticity ; Neurons ; Spinal Cord ; Spinal Cord Injuries

Recovery from central nervous system (CNS) injury, such as stroke or spinal cord injury (SCI), largely depends on axonal regeneration, and the neuronal and glial cells plasticity in the lesioned tissue. The lesioned tissue following CNS injury forms a scar that is composed of astrocytes and mixed with connective tissues. At the glial scar, the regenerating axon forms dystrophic endbulbs which do not regenerate and grow beyond the glial scar without a suitable environment. Along with the astrocytes, microglia are also suspected of being involved in necrotic and apoptotic neuronal cell death and the early response to axonal damage in CNS injury. The inflammatory response, a major component of secondary injury and controlled by the microglia, plays a pivotal role in nerve injury and control the regenerative response. As a result, it is very important to control the glial cell function in order to assure the recovery of the CNS injury. Studies have suggested that agmatine, a L-arginine derived primary amine, is a potential modulator of glial cell function after CNS injuries. Agmatine was found to possess anti-inflammatory and neuroprotective characteristics that benefited the rehabilitation process following CNS injury. In this review, we will discuss the effect of agmatine on glial cells in the process of recovery after CNS injury.
Agmatine ; Arginine ; Astrocytes ; Axons ; Cell Death ; Central Nervous System ; Cicatrix ; Connective Tissue ; Microglia ; Neuroglia ; Neurons ; Plastics ; Regeneration ; Rehabilitation ; Spinal Cord Injuries ; Stroke

OBJECTIVE: Spinal cord injury (SCI) is a very serious health problem, usually caused by a trauma and accompanied by elevated levels of inflammation indicators. Stem cell-based therapy is promising some valuable strategies for its functional recovery. Nestin-positive progenitor and/or stem cells (SC) isolated from pancreatic islets (PI) show mesenchymal stem cell (MSC) characteristics. For this reason, we aimed to analyze the effects of rat pancreatic islet derived stem cell (rPI-SC) delivery on functional recovery, as well as the levels of inflammation factors following SCI.METHODS: rPI-SCs were isolated, cultured and their MSC characteristics were determined through flow cytometry and immunofluorescence analysis. The experimental rat population was divided into three groups : 1) laminectomy & trauma, 2) laminectomy & trauma & phosphate-buffered saline (PBS), and 3) laminectomy+trauma+SCs. Green fluorescent protein (GFP) labelled rPI-SCs were transplanted into the injured rat spinal cord. Their motilities were evaluated with Basso, Beattie and Bresnahan (BBB) Score. After 4-weeks, spinal cord sections were analyzed for GFP labeled SCs and stained for vimentin, S100β, brain derived neurotrophic factor (BDNF), 2’,3’-cyclic-nucleotide 3'-phosphodiesterase (CNPase), vascular endothelial growth factor (VEGF) and proinflammatory (interleukin [IL]-6, transforming growth factor [TGF]-β, macrophage inflammatory protein [MIP]-2, myeloperoxidase [MPO]) and anti-inflammatory (IL-1 receptor antagonis) factors.RESULTS: rPI-SCs were revealed to display MSC characteristics and express neural and glial cell markers including BDNF, glial fibrillary acidic protein (GFAP), fibronectin, microtubule associated protein-2a,b (MAP2a,b), β3-tubulin and nestin as well as antiinflammatory prostaglandin E2 receptor, EP3. The BBB scores showed significant motor recovery in group 3. GFP-labelled cells were localized on the injury site. In addition, decreased proinflammatory factor levels and increased intensity of anti-inflammatory factors were determined.CONCLUSION: Transplantation of PI-SCs might be an effective strategy to improve functional recovery following spinal cord trauma.
Animals ; Brain-Derived Neurotrophic Factor ; Dinoprostone ; Fibronectins ; Flow Cytometry ; Fluorescent Antibody Technique ; Glial Fibrillary Acidic Protein ; Inflammation ; Islets of Langerhans ; Laminectomy ; Macrophages ; Mesenchymal Stromal Cells ; Microtubules ; Nestin ; Neuroglia ; Peroxidase ; Rats ; Regeneration ; Spinal Cord Injuries ; Spinal Cord ; Stem Cell Transplantation ; Stem Cells ; Transforming Growth Factors ; Vascular Endothelial Growth Factor A ; Vimentin ; Wounds and Injuries

The inhibitory environment that surrounds the lesion site and the lack of intrinsic regenerative capacity of the adult mammalian central nervous system (CNS) impede the regrowth of injured axons and thereby the reestablishment of neural circuits required for functional recovery after spinal cord injuries (SCI). To circumvent these barriers, biomaterial scaffolds are applied to bridge the lesion gaps for the regrowing axons to follow, and, often by combining stem cell transplantation, to enable the local environment in the growth-supportive direction. Manipulations, such as the modulation of PTEN/mTOR pathways, can also enhance intrinsic CNS axon regrowth after injury. Given the complex pathophysiology of SCI, combining biomaterial scaffolds and genetic manipulation may provide synergistic effects and promote maximal axonal regrowth. Future directions will primarily focus on the translatability of these approaches and promote therapeutic avenues toward the functional rehabilitation of patients with SCIs.
Animals ; Axons ; physiology ; Biocompatible Materials ; Genetic Enhancement ; methods ; Humans ; Nerve Regeneration ; PTEN Phosphohydrolase ; metabolism ; Recovery of Function ; Spinal Cord Injuries ; physiopathology ; Tissue Engineering ; methods ; Tissue Scaffolds

Spinal cord injury (SCI) causes axonal damage and demyelination, neural cell death, and comprehensive tissue loss, resulting in devastating neurological dysfunction. Neural stem/progenitor cell (NSPCs) transplantation provides therapeutic benefits for neural repair in SCI, and glial cell line-derived neurotrophic factor (GDNF) has been uncovered to have capability of stimulating axonal regeneration and remyelination after SCI. In this study, to evaluate whether GDNF would augment therapeutic effects of NSPCs for SCI, GDNF-encoding or mock adenoviral vector-transduced human NSPCs (GDNF-or Mock-hNSPCs) were transplanted into the injured thoracic spinal cords of rats at 7 days after SCI. Grafted GDNF-hNSPCs showed robust engraftment, long-term survival, an extensive distribution, and increased differentiation into neurons and oligodendroglial cells. Compared with Mock-hNSPC- and vehicle-injected groups, transplantation of GDNF-hNSPCs significantly reduced lesion volume and glial scar formation, promoted neurite outgrowth, axonal regeneration and myelination, increased Schwann cell migration that contributed to the myelin repair, and improved locomotor recovery. In addition, tract tracing demonstrated that transplantation of GDNF-hNSPCs reduced significantly axonal dieback of the dorsal corticospinal tract (dCST), and increased the levels of dCST collaterals, propriospinal neurons (PSNs), and contacts between dCST collaterals and PSNs in the cervical enlargement over that of the controls. Finally grafted GDNF-hNSPCs substantially reversed the increased expression of voltage-gated sodium channels and neuropeptide Y, and elevated expression of GABA in the injured spinal cord, which are involved in the attenuation of neuropathic pain after SCI. These findings suggest that implantation of GDNF-hNSPCs enhances therapeutic efficiency of hNSPCs-based cell therapy for SCI.
Animals ; Axons ; Cell Death ; Cell Movement ; Cell- and Tissue-Based Therapy ; Cicatrix ; Demyelinating Diseases ; gamma-Aminobutyric Acid ; Glial Cell Line-Derived Neurotrophic Factor ; Humans ; Hyperalgesia ; Myelin Sheath ; Neuralgia ; Neurites ; Neuroglia ; Neurons ; Neuropeptide Y ; Paraplegia ; Pyramidal Tracts ; Rats ; Regeneration ; Spinal Cord Injuries ; Spinal Cord ; Therapeutic Uses ; Transplants ; Voltage-Gated Sodium Channels