Current and future therapeutic strategies for functional repair of spinal cord injury

Roles of cerebrospinal fluid-contacting neurons as potential neural stem cells in the repair and regeneration of spinal cord injuries

Cerebrospinal fluid-contacting neurons (CSF-cNs) represent a distinct group of interneurons characterized by their prominent apical globular protrusions penetrating the spinal cord's central canal and their basal axons extending towards adjacent cells. Identified nearly a century back, the specific roles and attributes of CSF-cNs have just started to emerge due to the historical lack of definitive markers. Recent findings have confirmed that CSF-cNs expressing PKD2L1 possess attributes of neural stem cells, suggesting a critical function in the regeneration processes following spinal cord injuries. This review aims to elucidate the molecular markers of CSF-cNs as potential neural stem cells during spinal cord development and assess their roles post-spinal cord injury, with an emphasis on their potential therapeutic implications for spinal cord repair.

Genetically engineered electrospinning contributes to spinal cord injury repair by regulating the immune microenvironment

Introduction: Spinal cord injury (SCI) is associated with microenvironment imbalance, thereby resulting in poor regeneration and recovery of the spinal cord. Gene therapy can be used to balance the inflammatory response, however target genes cannot exist in localized injured areas. Methods: A genetically engineered electrospun scaffold (GEES) to achieve long-term immunoregulation and nerve repair was constructed. By combining the microfluidic and electrospinning techniques, interleukin-10 plasmid (pIL10) was loaded into lipid nanoparticles (LNPs) (pIL10-LNP), which was encapsulated to the nerve growth factor (NGF). Immunofluorescence staining, qRT-PCR, ELISA, flow cytometry, and other tests were employed to comprehensively assess the role of GEES in modulating macrophage polarization and facilitating neural repair. Results: The results showed that the scaffold released >70% of the pIL10-LNP within 10 d and continued slow release within 30 d. In vitro cell experiments have demonstrated that GEES effectively stimulates macrophages to secrete anti-inflammatory cytokines and facilitates the differentiation of neural stem cells into neuronal cells. In rat T9 SCI model, the GEES significantly inhibited the inflammatory response in the acute and chronic phases of SCI by transfecting local tissues with slow-release pIL10-LNP to promote the release of the anti-inflammatory factor IL10, thereby creating a favorable microenvironment. With the addition of NGF, the repair and regeneration of nerve tissues was effectively promoted, and the post-SCI motor function of rats improved. Discussion: GEES can regulate post-SCI immune responses through continuous and effective gene delivery, providing a new strategy for the construction of electrospun scaffolds for nerve repair in gene therapy.

Do Pharmacological Treatments Act in Collaboration with Rehabilitation in Spinal Cord Injury Treatment? A Review of Preclinical Studies

There is no choice other than rehabilitation as a practical medical treatment to restore impairments or improve activities after acute treatment in people with spinal cord injury (SCI); however, the effect is unremarkable. Therefore, researchers have been seeking effective pharmacological treatments. These will, hopefully, exert a greater effect when combined with rehabilitation. However, no review has specifically summarized the combinatorial effects of rehabilitation with various medical agents. In the current review, which included 43 articles, we summarized the combinatorial effects according to the properties of the medical agents, namely neuromodulation, neurotrophic factors, counteraction to inhibitory factors, and others. The recovery processes promoted by rehabilitation include the regeneration of tracts, neuroprotection, scar tissue reorganization, plasticity of spinal circuits, microenvironmental change in the spinal cord, and enforcement of the musculoskeletal system, which are additive, complementary, or even synergistic with medication in many cases. However, there are some cases that lack interaction or even demonstrate competition between medication and rehabilitation. A large fraction of the combinatorial mechanisms remains to be elucidated, and very few studies have investigated complex combinations of these agents or targeted chronically injured spinal cords.

Acupuncture combined with moxibustion mitigates spinal cord injury-induced motor dysfunction in mice by NLRP3-IL-18 signaling pathway inhibition

BACKGROUND

Spinal cord injury (SCI), which reportedly induces severe motor dysfunction, imposes a significant social and financial burden on affected individuals, families, communities, and nations. Acupuncture combined with moxibustion (AM) therapy has been widely used for motor dysfunction treatment, but the underlying mechanisms remain unknown. In this work, we aimed to determine whether AM therapy could alleviate motor impairment post-SCI and, if so, the potential mechanism.

METHODS

A SCI model was established in mice through impact methods. AM treatment was performed in SCI model mice at Dazhui (GV14) and Jiaji points (T7-T12), Mingmen (GV4), Zusanli (ST36), and Ciliao (BL32) on both sides for 30 min once per day for 28 days. The Basso-Beattie-Bresnahan score was used to assess motor function in mice. A series of experiments including astrocytes activation detected by immunofluorescence, the roles of NOD-like receptor pyrin domain-containing-3 (NLRP3)-IL-18 signaling pathway with the application of astrocyte-specific NLRP3 knockout mice, and western blot were performed to explore the specific mechanism of AM treatment in SCI.

RESULTS

Our data indicated that mice with SCI exposure exhibited motor dysfunction, a significant decrease of neuronal cells, a remarkable activation of astrocytes and microglia, an increase of IL-6, TNF-α, IL-18 expression, and an elevation of IL-18 colocalized with astrocytes, while astrocytes-specific NLRP3 knockout heavily reversed these changes. Besides, AM treatment simulated the neuroprotective effects of astrocyte-specific NLRP3 knockout, whereas an activator of NLRP3 nigericin partially reversed the AM neuroprotective effects.

CONCLUSION

AM treatment mitigates SCI-induced motor dysfunction in mice; this protective mechanism may be related to the NLRP3-IL18 signaling pathway inhibition in astrocytes.

Therapeutic administration of mouse mast cell protease 6 improves functional recovery after traumatic spinal cord injury in mice by promoting remyelination and reducing glial scar formation

Traumatic spinal cord injury (SCI) most often leads to permanent paralysis due to the inability of axons to regenerate in the adult mammalian central nervous system (CNS). In the past, we have shown that mast cells (MCs) improve the functional outcome after SCI by suppressing scar tissue formation at the lesion site via mouse mast cell protease 6 (mMCP6). In this study, we investigated whether recombinant mMCP6 can be used therapeutically to improve the functional outcome after SCI. Therefore, we applied mMCP6 locally via an intrathecal catheter in the subacute phase after a spinal cord hemisection injury in mice. Our findings showed that hind limb motor function was significantly improved in mice that received recombinant mMCP6 compared with the vehicle-treated group. In contrast to our previous findings in mMCP6 knockout mice, the lesion size and expression levels of the scar components fibronectin, laminin, and axon-growth-inhibitory chondroitin sulfate proteoglycans were not affected by the treatment with recombinant mMCP6. Surprisingly, no difference in infiltration of CD4+ T cells and reactivity of Iba-1+ microglia/macrophages at the lesion site was observed between the mMCP6-treated mice and control mice. Additionally, local protein levels of the pro- and anti-inflammatory mediators IL-1β, IL-2, IL-4, IL-6, IL-10, TNF-α, IFNγ, and MCP-1 were comparable between the two treatment groups, indicating that locally applied mMCP6 did not affect inflammatory processes after injury. However, the increase in locomotor performance in mMCP6-treated mice was accompanied by reduced demyelination and astrogliosis in the perilesional area after SCI. Consistently, we found that TNF-α/IL-1β-astrocyte activation was decreased and that oligodendrocyte precursor cell (OPC) differentiation was increased after recombinant mMCP6 treatment in vitro. Mechanistically, this suggests effects of mMCP6 on reducing astrogliosis and improving (re)myelination in the spinal cord after injury. In conclusion, these data show for the first time that recombinant mMCP6 is therapeutically active in enhancing recovery after SCI.

Protective Effect of Hydrogen-Rich Saline on Spinal Cord Damage in Rats

The anti-inflammatory and anti-apoptotic effects of molecular hydrogen, delivered as hydrogen-rich saline (HRS), on spinal cord injury was investigated. Four-month-old male Sprague Dawley rats (n = 24) were classified into four groups: (1) control—laminectomy only at T7-T10; (2) spinal injury—dura left intact, Tator and Rivlin clip compression model applied to the spinal cord for 1 min, no treatment given; (3) HRS group—applied intraperitoneally (i.p.) for seven days; and (4) spinal injury—HRS administered i.p. for seven days after laminectomy at T7–T10 level, leaving the dura intact and applying the Tator and Rivlin clip compression model to the spinal cord for 1 min. Levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) were measured in blood taken at day seven from all groups, and hematoxylin–eosin (H & E) and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) were used to stain the tissue samples. IL-6 and TNF-α levels were significantly lower in the group treated with HRS following the spinal cord injury compared to the group whose spinal cord was damaged. A decrease in apoptosis was also observed. The anti-inflammatory and anti-apoptotic effect of IL-6 may be a clinically useful adjuvant therapy after spinal cord injury.

Endoplasmic Reticulum Stress Causing Apoptosis in a Mouse Model of an Ischemic Spinal Cord Injury

A spinal cord injury (SCI) is the devastating trauma associated with functional deterioration due to apoptosis. Most laboratory SCI models are generated by a direct impact on an animal's spinal cord; however, our model does not involve the direct impact on the spinal cord. Instead, we use a clamp compression to create an ischemia in the descending aortas of mice. Following the success of inducing an ischemic SCI (ISCI), we hypothesized that this model may show apoptosis via an endoplasmic reticulum (ER) stress pathway. This apoptosis by the ER stress pathway is enhanced by the inducible nitric oxide synthase (iNOS). The ER is used for the protein folding in the cell. When the protein folding capacity is overloaded, the condition is termed the ER stress and is characterized by the accumulation of misfolded proteins inside the ER lumen. The unfolded protein response (UPR) signaling pathways that deal with the ER stress response then become activated. This UPR activates the three signal pathways that are regulated by the inositol-requiring enzyme 1α (IRE1α), the activating transcription factor 6 (ATF6), and the protein kinase RNA-like ER kinase (PERK). IRE1α and PERK are associated with the expression of the apoptotic proteins. Apoptosis caused by an ISCI is assessed using the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) test. An ISCI also reduces synaptophysin and the neuronal nuclear protein (NeuN) in the spinal cord. In conclusion, an ISCI increases the ER stress proteins, resulting in apoptosis in neuronal cells in the spinal cord.

From 2D to 3D Co-Culture Systems: A Review of Co-Culture Models to Study the Neural Cells Interaction

The central nervous system (CNS) controls and regulates the functional activities of the organ systems and maintains the unity between the body and the external environment. The advent of co-culture systems has made it possible to elucidate the interactions between neural cells in vitro and to reproduce complex neural circuits. Here, we classified the co-culture system as a two-dimensional (2D) co-culture system, a cell-based three-dimensional (3D) co-culture system, a tissue slice-based 3D co-culture system, an organoid-based 3D co-culture system, and a microfluidic platform-based 3D co-culture system. We provide an overview of these different co-culture models and their applications in the study of neural cell interaction. The application of co-culture systems in virus-infected CNS disease models is also discussed here. Finally, the direction of the co-culture system in future research is prospected.

Synthesis, Processing and the Effect of Thermal Treatment on the Solubility, Antioxidant Potential and Cytocompatibility of Y2O3 and CeO2 doped SiO2-SrO-Na2O Glass-Ceramics

Thermal treatment of a 0.52SiO₂-0.24SrO-0.24-xNa₂O-xMO glass-ceramic series (where x = 0.08 and MO = Y₂O₃ or CeO₂) was conducted in order to synthesize yttrium (Y³⁺) and cerium (Ce³⁺) crystalline species that may act as radical oxygen specie (ROS) scavengers. The prominent phase for the Control is a sodium-strontium-silicate while the experimental glass-ceramics (HY, YCe, and HCe) present sodium-Y/Ce-silicate and oxide phases. Disk shrinkage during thermal processing ranges from 1-7% for Control, HY, YCe, and HCe in both diameter and thickness. Solubility studies determined that the release of Si⁴⁺ and Na⁺ are greatest from the Control disks which peaks at 1550 µg/mL. Release from the Y³⁺ and Ce³⁺ glass-ceramics reached 320 µg/mL for Si⁴⁺ and 630 µg/mL for Na⁺. The range of antioxidant capacity (ABTS assay) for all samples was 0.31-3.9 mMTE. No significant reduction in MC 3T3 Osteoblast cell viability was observed for any composition tested.

Sesamol Attenuates Neuroinflammation by Regulating the AMPK/SIRT1/NF-κB Signaling Pathway after Spinal Cord Injury in Mice

Inflammation is one of the crucial mechanisms mediating spinal cord injury (SCI) progress. Sesamol, a component of sesame oil, has anti-inflammatory activity, but its mechanism in SCI remains unclear. We investigated if the AMPK/SIRT1/NF-κB pathway participated in anti-inflammation of sesamol in SCI. Sesamol could inhibit neuronal apoptosis, reduce neuroinflammation, enhance M2 phenotype microglial polarization, and improved motor function recovery in mice after SCI. Furthermore, sesamol increased SIRT1 protein expression and p-AMPK/AMPK ratio, while it downregulated the p-p65/p65 ratio, indicating that sesamol treatment upregulated the AMPK/SIRT1 pathway and inhibited NF-κB activation. However, these effects were blocked by compound C which is a specific AMPK inhibitor. Together, the study suggests that sesamol is a potential drug for antineuroinflammation and improving locomotor functional recovery through regulation of the AMPK/SIRT1/NF-κB pathway in SCI.

Functional hydrogels as therapeutic tools for spinal cord injury: New perspectives on immunopharmacological interventions

Spinal cord injury (SCI) is a complex medical and psychological challenge for which there is no curative therapy currently available. Despite major progress in pharmacological and surgical approaches, clinical trials for SCI patients have been uniformly disappointing thus far as there are many practical and biological issues yet to be resolved. Neuroinflammation is a critical event of the secondary injury phase after SCI, and recent research strategies have focused on modulating the immune response after injury to provide a more favorable recovery environment. Biomaterials can serve this purpose by providing physical and trophic support to the injured spinal cord after SCI. Of all potential biomaterials, functional hydrogels are emerging as a key component in novel treatment strategies for SCI, including controlled and localized delivery of immunomodulatory therapies to drive polarization of immune cells towards a pro-regenerative phenotype. Here, we extensively review recent developments in the use of functional hydrogels as immunomodulatory therapies for SCI. We briefly describe physicochemical properties of hydrogels and demonstrate how advanced fabrication methods lead to the required heterogeneity and hierarchical arrangements that increasingly mimic complex spinal cord tissue. We then summarize potential SCI therapeutic modalities including: (i) hydrogels alone; (ii) hydrogels as cellular or (iii) bioactive molecule delivery vehicles, and; (iv) combinatorial approaches. By linking the structural properties of hydrogels to their functions in treatment with particular focus on immunopharmacological stimuli, this may accelerate further development of functional hydrogels for SCI, and indeed next-generation central nervous system regenerative therapies.

Inhibition of heat shock protein family A member 8 attenuates spinal cord ischemia-reperfusion injury via astrocyte NF-κB/NLRP3 inflammasome pathway : HSPA8 inhibition protects spinal ischemia-reperfusion injury

Background

Astrocyte over-activation and extensive neuron loss are the main characteristic pathological features of spinal cord ischemia–reperfusion injury (SCII). Prior studies have placed substantial emphasis on the role of heat shock protein family A member 8 (HSPA8) on postischemic myocardial inflammation and cardiac dysfunction. However, it has never been determined whether HSPA8 participates in astrocyte activation and thus mediated neuroinflammation associated with SCII.

Methods

The left renal artery ligation-induced SCII rat models and oxygen–glucose deprivation and reoxygenation (OGD/R)-induced rat primary cultured astrocytes were established. The lentiviral vector encoding short hairpin RNA targeting HSPA8 was delivered to the spinal cord by intrathecal administration or to culture astrocytes. Then, the spinal neuron survival, gliosis, and nod-like receptor pyrin domain-containing 3 (NLRP3) inflammasome and its related pro-inflammatory cytokines were analyzed.

Results

SCII significantly enhanced the GFAP and HSPA8 expression in the spinal cord, resulting in blood–brain barrier breakdown and the dramatical loss of spinal neuron and motor function. Moreover, injury also increased spinal nuclear factor-kappa B (NF-κB) p65 phosphorylation, NLRP3 inflammasome-mediated caspase-1 activation, and subsequent interleukin (IL)-1β as well as IL-18 secretion. Silencing the HSPA8 expression efficiently ameliorated the spinal cord tissue damage and promoted motor function recovery after SCII, through blockade of the astrocyte activation and levels of phosphorylated NF-κB, NLRP3, caspase-1, IL-1β, and IL-18. Further in vitro studies confirmed that HSPA8 knockdown protected astrocytes from OGD/R-induced injury via the blockade of NF-κB and NLRP3 inflammasome activation.

Conclusion

Our findings indicate that knockdown of HSPA8 inhibits spinal astrocytic damage after SCII, which may provide a promising therapeutic strategy for SCII treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02220-0.

A novel paired associative stimulation protocol with a high-frequency peripheral component: A review on results in spinal cord injury rehabilitation

In recent decades, a multitude of therapeutic approaches has been developed for spinal cord injury (SCI), but few have progressed to regular clinical practice. Novel non-invasive, cost-effective, and feasible approaches to treat this challenging condition are needed. A novel variant of paired associative stimulation (PAS), high-PAS, consists of non-invasive high-intensity transcranial magnetic stimulation (TMS) and non-invasive high-frequency electrical peripheral nerve stimulation (PNS). We observed a therapeutic effect of high-PAS in 20 patients with incomplete SCI with wide range of injury severity, age, and time since injury. Tetraplegic and paraplegic, traumatic, and neurological SCI patients benefited from upper- or lower-limb high-PAS. We observed increases in manual motor scores (MMT) of upper and lower limbs, functional hand tests, walking tests, and measures of functional independence. We also optimized PAS settings in several studies in healthy subjects and began elucidating the mechanisms of therapeutic action. The scope of this review is to describe the clinical experience gained with this novel PAS approach. This review is focused on the summary of our results and observations and the methodological considerations for researchers and clinicians interested in adopting and further developing this new method.

Endocrine Therapy for the Functional Recovery of Spinal Cord Injury

Spinal cord injury (SCI) is a major cause of physical disability and leads to patient dissatisfaction with their quality of life. Patients with SCI usually exhibit severe clinical symptoms, including sensory and motor dysfunction below the injured levels, paraplegia, quadriplegia and urinary retention, which can exacerbate the substantial medical and social burdens. The major pathological change observed in SCI is inflammatory reaction, which induces demyelination, axonal degeneration, and the apoptosis and necrosis of neurons. Traditional medical treatments are mainly focused on the recovery of motor function and prevention of complications. To date, numerous studies have been conducted to explore the cellular and molecular mechanism of SCI and have proposed lots of effective treatments, but the clinical applications are still limited due to the complex pathogenesis and poor prognosis after SCI. Endocrine hormones are kinds of molecules that are synthesized by specialized endocrine organs and can participate in the regulation of multiple physiological activities, and their protective effects on several disorders have been widely discussed. In addition, many studies have identified that endocrine hormones can promote nerve regeneration and functional recovery in individuals with central nervous system diseases. Therefore, studies investigating the clinical applications of endocrine hormones as treatments for SCI are necessary. In this review, we described the neuroprotective roles of several endocrine hormones in SCI; endocrine hormone administration reduces cell death and promotes functional repair after SCI. We also proposed novel therapies for SCI.

Overexpression of the transcription factors OCT4 and KLF4 improves motor function after spinal cord injury

Introduction

Astrogliosis and glial scar formation following spinal cord injury (SCI) are viewed as major obstacles that hinder axonal regeneration and functional recovery. Regulating the glial scar and axonal regeneration in the lesion site is important for treating SCI.

Aims

Considering the important role of astrocyte in glial scar formation and subsequent axonal regeneration, we intended to investigate the effect of the transcription factors OCT4 and KLF4 on astrocyte and the underlying mechanism after spinal cord contusion injury in transgenic mice.

Results

Western blotting, q‐PCR, immunofluorescence, and functional evaluation suggested that glial fibrillary acidic protein (GFAP) expression decreased in the lesion area, the porosity of the scar increased, and remyelination enhanced. Mice overexpressing the transcription factors OCT4 and KLF4 had higher Basso Mouse Scale scores than did the control mice. Moreover, using immunofluorescence and Western blotting, we discovered that some astrocytes expressed nestin and sox2 protein, suggesting that these astrocytes were reprogrammed into neural stem cell‐like cells. Furthermore, a cell scratch assay showed that the migration ability of the astrocytes was significantly inhibited in the presence of the transcription factors OCT4 and KLF4. In addition, we demonstrated that the Hippo/Yap pathway was activated after these two transcription factors overexpressed in astrocytes.

Conclusions

In summary, these results suggest that overexpression of the transcription factors OCT4 and KLF4 could induce astrocyte reprogramming, which subsequently improves remyelination and functional recovery after SCI.

Acellularized spinal cord scaffolds incorporating bpV(pic)/PLGA microspheres promote axonal regeneration and functional recovery after spinal cord injury

Spinal cord injury (SCI) is a traumatic injury to the central nervous system (CNS) with a high rate of disability and a low capability of self-recovery. Phosphatase and tensin homolog (PTEN) inhibition by pharmacological blockade with bisperoxovanadium (pic) (bpV(pic)) has been reported to increase AKT/mTOR activity and induce robust axonal elongation and regeneration. However, the therapeutic effect of bpV(pic) in treating SCI is limited due to the lack of efficient delivery approaches. In this study, a composite scaffold consisting of an acellular spinal cord (ASC) scaffold and incorporated bpV(pic) loaded poly (lactic-co-glycolic acid) (PLGA) microspheres was developed, in order to improve the therapeutic effect of bpV(pic) on SCI. The inhibition of PTEN activity and activation of the mTORC1/AKT pathway, the axonal regeneration and the markers of apoptosis were analyzed via western blot and immunofluorescence in vitro. The bpV(pic)/PLGA/ASC scaffolds showed excellent biocompatibility and promoted the viability of neural stem cells and axonal growth in vitro. Implantation of the composite scaffold into rats with hemi-sectioned SCI resulted in increased axonal regeneration and functional recovery in vivo. Besides, bpV(pic) inhibited the phosphorylation of PTEN and activated the PI3K/mTOR signaling pathway. The successful construction of the composite scaffold improves the therapeutic effect of bpV(pic) on SCI.

Combination therapy with astaxanthin and epidermal neural crest stem cells improves motor impairments and activates mitochondrial biogenesis in a rat model of spinal cord injury

Spinal cord injury (SCI), a multifactorial disease, can lead to irreversible motor and sensory disabilities. Cell therapy in combination with pharmacological agents can be a promising approach to attenuate SCI damages. Epidermal neural crest stem cells (EPI-NCSCs) extracted from bulge hair follicle in adults are attractive candidates due to the possibility of autologous transplantation. This study evaluated the effect of EPI-NCSCs combined with astaxanthin (Ast), a potent antioxidant, on damages induced by SCI. Male rats were treated with Ast (0.2 mM) and EPI-NCSCs (10⁶/10 μl PBS) alone and combined together after SCI contusion. Motor function was assessed by Basso, Beattie and Bresnahan (BBB) test on days 1, 3, 7, 14, 21, 28, 35 and 42 post-injury. Motor neurons number and myelin level were evaluated on days 14 and 42 using Nissl and Luxol Fast Blue staining. The gene expression of mitochondrial biogenesis involved factors (PGC1α, NRF1 and TFAM) was measured by qPCR. All treatments improved motor function, with the highest BBB score in Ast + Cell compared to Ast and Cell. Decreased motor neurons number and myelin level following SCI, were increased by Ast, Cell and Ast + Cell, but combination therapy significantly had a better effect. We observed reduction in PGC1α, NRF1, and TFAM expression in spinal tissue after SCI, and treatment with Cell and Ast + Cell significantly restored NRF1 and TFAM mRNA levels. These results suggested that Ast in combination with EPI-NCSCs has better effects on behavioral dysfunction, motor neuron loss and demyelination after SCI. These protective effects may be attributed to mitochondrial biogenesis activation.

Fibroblast Growth Factor 22 Inhibits ER Stress-Induced Apoptosis and Improves Recovery of Spinal Cord Injury

Currently, inhibiting or reducing neuronal cell death is the main strategy to improve recovery of spinal cord injury (SCI). Therapies using nerve growth factors to treat SCI mainly focused on reducing the area damaged by postinjury degeneration to promote functional recovery. In this report, we investigated the mechanism of ER (endoplasmic reticulum) stress-induced apoptosis and the protective action of fibroblast growth factor 22 (FGF22) in vivo. Our results demonstrated that ER stress-induced apoptosis plays a significant role in injury of SCI model rats. FGF22 administration promoted recovery and increased neuron survival in the spinal cord lesions of model mice. The protective effect of FGF22 is related to decreased expression of CHOP (C/EBP-homologous protein), GRP78 (glucose-regulated protein 78), caspase-12, X-box binding protein 1 (XBP1), eukaryotic initiation factor 2α (Eif-2α) and Bad which are ER stress-induced apoptosis response proteins. Moreover, FGF22 administration also increased the number of neurons and the expression of growth-associated protein 43 (GAP43) which was related to axon regeneration. We also demonstrated that the protective effect of FGF22 effectively reduces neuronal apoptosis and promotes axonal regeneration. Our study first illustrated that the function of FGF22 is related to the inhibition of ER stress-induced cell death in SCI recovery via activation of downstream signals. This study also suggested a new tendency of FGF22 therapy development in central neural system injuries, which involved chronic ER stress-induced apoptosis.

Necrosulfonamide Ameliorates Neurological Impairment in Spinal Cord Injury by Improving Antioxidative Capacity

Currently, there is no efficient therapy for spinal cord injury (SCI). Anoxemia after SCI is a key problem, which leads to tissue destruction, while hypoxia after SCI induces cell injury along with inflammation. Mixed-lineage kinase domain-like protein (MLKL) is a critical signal molecule of necroptosis, and mitochondrial dysfunction is regarded as one of the most pivotal events after SCI. Based on the important role of MLKL in cell damage and potential role of mitochondrial dysfunction, our study focuses on the regulation of MLKL by Necrosulfonamide (NSA) in mitochondrial dysfunction of oxygen-glucose deprivation (OGD)-induced cell damage and SCI-mice, which specifically blocks the MLKL. Our results showed that NSA protected against a decrease in the mitochondrial membrane potential, adenosine triphosphate, glutathione, and superoxide dismutase levels and an increase in reactive oxygen species and malonyldialdehyde levels. NSA also improved the locomotor function in SCI-mice and OGD-induced spinal neuron injury through inhibition of MLKL activation independently of receptor-interacting protein kinase 3 (RIP3) phosphorylation. Besides the protective effects, NSA exhibited a therapeutic window. The optimal treatment time was within 12 h after the injury in the SCI-mice model. In conclusion, our data suggest a close association between the NSA level inhibiting p-MLKL independently of RIP3 phosphorylation and induction of neurological impairment by improving antioxidative capacity after SCI. NSA ameliorates neurological impairment in SCI through inhibiting MLKL-dependent necroptosis. It also provides a theoretical basis for further research and application of NSA in the treatment of SCI.

Skilled Movements in Mice Require Inhibition of Corticospinal Axon Collateral Formation in the Spinal Cord by Semaphorin Signaling

Corticospinal (CS) neurons in layer V of the sensorimotor cortex are essential for voluntary motor control. Those neurons project axons to specific segments along the rostro-caudal axis of the spinal cord, and reach their spinal targets by sending collateral branches interstitially along axon bundles. Currently, little is known how CS axon collaterals are formed in the proper spinal cord regions. Here, we show that the semaphorin3A (Sema3A)-neuropilin-1 (Npn-1) signaling pathway is an essential negative regulator of CS axon collateral formation in the spinal cord from mice of either sex. Sema3A is expressed in the ventral spinal cord, whereas CS neurons express Npn-1, suggesting that Sema3A might prevent CS axons from entering the ventral spinal cord. Indeed, the ectopic expression of Sema3A in the spinal cord in vivo inhibits CS axon collateral formation, whereas Sema3A or Npn-1 mutant mice have ectopic CS axon collateral formation within the ventral spinal cord compared with littermate controls. Finally, Npn-1 mutant mice exhibit impaired skilled movements, likely because of aberrantly formed CS connections in the ventral spinal cord. These genetic findings reveal that Sema3A-Npn-1 signaling-mediated inhibition of CS axon collateral formation is critical for proper CS circuit formation and the ability to perform skilled motor behaviors.SIGNIFICANCE STATEMENT CS neurons project axons to the spinal cord to control skilled movements in mammals. Previous studies revealed some of the molecular mechanisms underlying different phases of CS circuit development such as initial axon guidance in the brain, and midline crossing in the brainstem and spinal cord. However, the molecular mechanisms underlying CS axon collateral formation in the spinal gray matter has remained obscure. In this study, using in vivo gain-of- and loss-of-function experiments, we show that Sema3A-Npn-1 signaling functions to inhibit CS axon collateral formation in the ventral spinal cord, allowing for the development of proper skilled movements in mice.

Upregulated protein O-GlcNAcylation promoted functional and structural recovery of the contused spinal cord injury in rats by Thiamet-G treatment

Objectives-Elevated protein O-GlcNAcylation could benefit cell survival and promote organ functional recovery. Thiamet-G (O-GlcNAcase inhibitor) could upregulate protein O-GlcNAcylation level to improve dyskinesia in models of neurodegenerative diseases without any obvious detrimental side-effects. Therefore, we conducted this study to investigate the effects of protein O-GlcNAcylation upregulation by Thiamet-G on the spinal cord injury (SCI) in rats. Methods-We randomly assigned 74 rats to three groups: sham-operated group (Sham) with no lesion (n = 22), injured control group (SCI+SS) with saline solution (n = 26), and Thiamet-G treated group (SCI+Thiamet-G) (n = 26). We assessed Locomotor behavior using the Basso, Beattice, and Bresnahan (BBB) scale and evaluated histopathological alterations by morphometry and histochemistry. We also assessed potential inflammatory effects by microglia/macrophages immunohistochemistry, and potential apoptosis effects by caspase-3 western blot. Results-Thiamet-G treatment improved hindlimb motor functional recovery by inducing elevated protein O-GlcNAcylation, and mitigated the severity, reduced the lesion size and promoted the structural recovery of the injured spinal cord. Thiamet-G treatment also inhibited microglia/macrophages infiltration at the injury sites and the caspase-3 mediated apoptosis pathway. Discussion-We conclude that Thiamet-G induced elevated protein O-GlcNAcylation to ameliorate acute SCI, which could provide a potential novel therapeutic approach for SCI treatment.

Differential Glycosylation Expression in Injured Rat Spinal Cord Treated with Immunosuppressive Drug Cyclosporin-A

Glycosylation is ubiquitous throughout the central nervous system and altered following spinal cord injury (SCI). The glial scar that forms following SCI is composed of several chondroitin sulfate proteoglycans, which inhibit axonal regrowth. Cyclosporin-A (CsA), an immunosuppressive therapeutic, has been proposed as a potential treatment after SCI. We investigated CsA treatment in the spinal cord of healthy, contusion injured, and injured CsA-treated rats. Lectin histochemistry using fluorescently labeled lectins, SBA, MAA, SNA-I, and WFA, was performed to identify the terminal carbohydrate residues of glycoconjugates within the spinal cord. SBA staining decreased in gray and white matter following spinal cord injury, whereas staining was increased at the lesion site in CsA-treated animals, indicating an increase in galactose and N-acetylgalactosamine terminal structures. No significant changes in MAA were observed. WFA staining was abundant in gray matter and observed to increase at the lesion site, in agreement with increased expression of chondroitin sulfate proteoglycans. SNA-I-stained blood vessels in all spinal cord regions and dual staining identified a subpopulation of astrocytes in the lesion site, which expressed α-(2,6)-sialic acid. Glycosylation were altered in injured spinal cord treated with CsA, indicating that glycosylation and alteration of particular carbohydrate structures are important factors to consider in the examination of the environment of the spinal cord after injury.

Hydrogel-Assisted Antisense LNA Gapmer Delivery for In Situ Gene Silencing in Spinal Cord Injury

After spinal cord injury (SCI), nerve regeneration is severely hampered due to the establishment of a highly inhibitory microenvironment at the injury site, through the contribution of multiple factors. The potential of antisense oligonucleotides (AONs) to modify gene expression at different levels, allowing the regulation of cell survival and cell function, together with the availability of chemically modified nucleic acids with favorable biopharmaceutical properties, make AONs an attractive tool for novel SCI therapy developments. In this work, we explored the potential of locked nucleic acid (LNA)-modified AON gapmers in combination with a fibrin hydrogel bridging material to induce gene silencing in situ at a SCI lesion site. LNA gapmers were effectively developed against two promising gene targets aiming at enhancing axonal regeneration-RhoA and GSK3β. The fibrin-matrix-assisted AON delivery system mediated potent RNA knockdown in vitro in a dorsal root ganglion explant culture system and in vivo at a SCI lesion site, achieving around 75% downregulation 5 days after hydrogel injection. Our results show that local implantation of a AON-gapmer-loaded hydrogel matrix mediated efficient gene silencing in the lesioned spinal cord and is an innovative platform that can potentially combine gene regulation with regenerative permissive substrates aiming at SCI therapeutics and nerve regeneration.

Combine effect of Chondroitinase ABC and low level laser (660nm) on spinal cord injury model in adult male rats

After spinal cord injury (SCI) there are many recoveries inhibiting factors such as chondroitin sulfate proteoglycan (CSPG) and inflammation. The present study investigated the combinational effect of low level laser therapy (LLLT) as anti-inflammatory agent and Chondroitinase ABC (ChABC) enzyme as CSPG digesting factor on spinal cord after injury. This study performed on 44 male Wistar rats, spinal cord injury induced by a clip compression injury. Animals received two-weeks treatment of 660nm low level laser (LLL) and intraspinal injection of 1μg ChABC. Functional recovery, cavity size, myelination, axonal projections around the cavity, fibroblast invasion and expression of glycogen synthase kinase-3β (GSk 3β), CSPG and aquaporin 4 (AQP4) expression were evaluated. In statistical evaluation p<0.05 considered significant. Result showed the combination of LLLT and ChABC have more effect on reduction of cavity size, improvement of myelination and number of axons around the cavity and decreasing the expression of GSK3β, CSPG and AQP4 expression compared to LLLT and ChABC alone. In the laser and laser+enzyme groups AQP4 expression decreased significantly after SCI. Functional recovery, improved in LLLT and ChABC treated animals, but higher recovery belonged to the combination therapy group. The current study showed combination therapy by LLLT and ChABC is more efficient than a single therapy with each of them.

HDAC3 inhibition ameliorates spinal cord injury by immunomodulation

Following spinal cord injury (SCI), the innate immune response of microglia and infiltrating macrophages clears up cellular debris and promotes tissue repair, but it also inflicts secondary injury from inflammatory responses. Immunomodulation aimed at maximizing the beneficial effects while minimizing the detrimental roles of the innate immunity may aid functional recovery after SCI. However, intracellular drivers of global reprogramming of the inflammatory gene networks in the innate immune cells are poorly understood. Here we show that SCI resulted in an upregulation of histone deacetylase 3 (HDAC3) in the innate immune cells at the injury site. Remarkably, blocking HDAC3 with a selective small molecule inhibitor shifted microglia/macrophage responses towards inflammatory suppression, resulting in neuroprotective phenotypes and improved functional recovery in SCI model. Mechanistically, HDAC3 activity is largely responsible for histone deacetylation and inflammatory responses of primary microglia to classic inflammatory stimuli. Our results reveal a novel function of HDAC3 inhibitor in promoting functional recovery after SCI by dampening inflammatory cytokines, thus pointing towards a new direction of immunomodulation for SCI repair.

Neuroprotective effects of estrogen in CNS injuries: insights from animal models

Among the estrogens that are biosynthesized in the human body, 17β-estradiol (estradiol or E2) is the most common and the best estrogen for neuroprotection in animal models of the central nervous system (CNS) injuries such as spinal cord injury (SCI), traumatic brain injury (TBI), and ischemic brain injury (IBI). These CNS injuries are not only serious health problems, but also enormous economic burden on the patients, their families, and the society at large. Studies from animal models of these CNS injuries provide insights into the multiple neuroprotective mechanisms of E2 and also suggest the possibility of translating the therapeutic efficacy of E2 in the treatment SCI, TBI, and IBI in humans in the near future. The pathophysiology of these injuries includes loss of motor function in the limbs, arms and their extremities, cognitive deficit, and many other serious consequences including life-threatening paralysis, infection, and even death. The potential application of E2 therapy to treat the CNS injuries may become a trend as the results are showing significant therapeutic benefits of E2 for neuroprotection when administered into the animal models of SCI, TBI, and IBI. This article describes the plausible mechanisms how E2 works with or without the involvement of estrogen receptors and provides an overview of the known neuroprotective effects of E2 in these three CNS injuries in different animal models. Because activation of estrogen receptors has profound implications in maintaining and also affecting normal physiology, there are notable impediments in translating E2 therapy to the clinics for neuroprotection in CNS injuries in humans. While E2 may not yet be the sole molecule for the treatment of CNS injuries due to the controversies surrounding it, the neuroprotective effects of its metabolite and derivative or combination of E2 with another therapeutic agent are showing significant impacts in animal models that can potentially shape the new treatment strategies for these CNS injuries in humans.

Does vitamin C have the ability to augment the therapeutic effect of bone marrow-derived mesenchymal stem cells on spinal cord injury?

Methylprednisolone (MP) is currently the only drug confirmed to exhibit a neuroprotective effect on acute spinal cord injury (SCI). Vitamin C (VC) is a natural water-soluble antioxidant that exerts neuroprotective effects through eliminating free radical damage to nerve cells. Bone marrow mesenchymal stem cells (BMMSCs), as multipotent stem cells, are promising candidates in SCI repair. To evaluate the therapeutic effects of MP, VC and BMMSCs on traumatic SCI, 80 adult male rats were randomly divided into seven groups: control, SCI (SCI induction by weight-drop method), MP (SCI induction, followed by administration of 30 mg/kg MP via the tail vein, once every other 6 hours, for five times), VC (SCI induction, followed by intraperitoneal administration of 100 mg/kg VC once a day, for 28 days), MP + VC (SCI induction, followed by administration of MP and VC as the former), BMMSCs (SCI induction, followed by injection of 3 × 10⁶ BMMSCs at the injury site), and BMMSCs + VC (SCI induction, followed by BMMSCs injection and VC administration as the former). Locomotor recovery was assessed using the Basso Mouse Scale. Injured spinal cord tissue was evaluated using hematoxylin-eosin staining and immunohistochemical staining. Expression of transforming growth factor-beta, tumor necrosis factor-alpha, and matrix metalloproteinase-2 genes was determined using real-time quantitative PCR. BMMSCs intervention better promoted recovery of nerve function of rats with SCI, mitigated nerve cell damage, and decreased expression of transforming growth factor-beta, tumor necrosis factor-alpha, and matrix metalloproteinase-2 genes than MP and/or VC. More importantly, BMMSCs in combination with VC induced more obvious improvements. These results suggest that VC can enhance the neuroprotective effects of BMMSCs against SCI.

Bioactivity of Y2O3 and CeO2 doped SiO2-SrO-Na2O glass-ceramics

The bioactivity of yttrium and cerium are investigated when substituted for Sodium (Na) in a 0.52SiO2-0.24SrO-0.24 -xNa2O- xMO glass-ceramics (where x = 0.08 and MO = Y2O3 or CeO2). Bioactivity is monitored through pH and inductively coupled plasma-optical emission spectrometry where pH of simulated body fluid ranged from 7.5 to 7.6 and increased between 8.2 and 10.0 after 14-day incubation with the glass-ceramic disks. Calcium (Ca) and phosphorus (P) levels in simulated body fluid after incubation with yttrium and cerium containing disks show a continual decline over the 14-day period. In contrast, Con disks (not containing yttrium or cerium) caused the elimination of Ca in solution after 1 day and throughout the incubation period, and initially showed a decline in P levels followed by an increase at 14 days. Scanning electron microscopy and energy dispersive spectroscopy confirmed the presence of Ca and P on the surface of the simulated body fluid-incubated disks and showed precipitates on Con and HCe (8 mol% cerium) samples. Cell viability of MC3T3 osteoblasts was not significantly affected at a 9% extract concentration. Optical microscopy after 24 h cell incubation with disks showed that Con samples do not support osteoblast or Schwann cell growth, while all yttrium and cerium containing disks have direct contact with osteoblasts spread across the wells. Schwann cells attached in all wells, but only showed spreading with the HY-S (8 mol% yttrium, heated to sintering temperature) and YCe (4 mol% yttrium and cerium) disks. Scanning electron microscopy of the compatible disks shows osteoblast and sNF96.2 Schwann cells attachment and spreading directly on the disk surfaces.

The use of autologous neurogenically-induced bone marrow-derived mesenchymal stem cells for the treatment of paraplegic dogs without nociception due to spinal trauma

The aim of this study was to investigate the effects of percutaneous transplanted autologous neurogenically-induced bone marrow-derived mesenchymal stem cells (NIBM-MSCs) in paraplegic dogs without deep pain perception (DPP) secondary to external spinal trauma. Thirteen client owned dogs that had failed in improvement neurologically at least 42 days after conservative management, decompression and decompression-stabilization were included in the study. Each dog received two doses of autologous 5.0 × 10⁶ NIBM-MSCs suspension, which were positive to 2',3'-Cyclic-nucleotide-3'-phosphodiesterase (CNPase) and Microtubule-associated protein 2 (MAP-2), as well as to Glial fibrillary acidic protein (GFAP) and beta III tubulin. The cells were injected into the spinal cord through the hemilaminectomy or laminectomy defects percutaneously with 21 days interval for 2 times. The results were evaluated using Texas Spinal Cord Injury Scale (TSCIS), somatosensory evoked potentials (SEP) and motor evoked potentials (MEP) at the admission time, cell transplantation procedures and during 2, 5, 7 and 12th months after the second cell transplantation. Improvement after cell transplantation in gait, nociception, proprioception, SEP and MEP results was observed in just 2 cases, and only gait score improvement was seen in 6 cases, and no improvement was recorded in 5 cases. All progresses were observed until 2nd month after the second cell transplantation, however, there was no improvement after this period. In conclusion, percutaneous transplantation of autologous NIBM-MSCs is a promising candidate modality for cases with spinal cord injury after spinal trauma and poor prognosis.

Impact of Heat Shock Protein A 12B Overexpression on Spinal Astrocyte Survival Against Oxygen-Glucose-Serum Deprivation/Restoration in Primary Cultured Astrocytes

Heat shock protein A 12B (HSPA12B) is a newly discovered member of the heat shock protein 70 family. Preclinical evidence indicates that HSPA12B helps protect the brain from ischemic injury, although its specific function remains unclear. The aim of this study is to investigate whether HSPA12B overexpression can protect astrocytes from oxygen-glucose-serum deprivation/restoration (OGD/R) injury. We analyzed the effects of HSPA12B overexpression on spinal cord ischemia-reperfusion injury and spinal astrocyte survival. After ischemia-reperfusion injury, we found that HSPA12B overexpression decreased spinal cord water content and infarct volume. MTT assay showed that HSPA12B overexpression increased astrocyte survival after OGD/R treatment. Flow cytometry results showed a marked inhibition of OGD/R-induced astrocyte apoptosis. Western blot assay showed that HSPA12B overexpression significantly increased regulatory protein B-cell lymphocyte 2 (Bcl-2) levels, whereas it decreased expression of the Bax protein, which forms a heterodimer with Bcl-2. Measurements of the level of activation of caspase-3 by Caspase-Glo®3/7 Assay kit showed that HSPA12B overexpression markedly inhibited caspase-3 activation. Notably, we demonstrated that the effects of HSPA12B on spinal astrocyte survival depended on activation of the PI3K/Akt signal pathway. These findings indicate that HSPA12B protects against spinal cord ischemia-reperfusion injury and may represent a potential treatment target.

Inhibition of Epidermal Growth Factor Receptor Improves Myelination and Attenuates Tissue Damage of Spinal Cord Injury

Preventing demyelination and promoting remyelination of denuded axons are promising therapeutic strategies for spinal cord injury (SCI). Epidermal growth factor receptor (EGFR) inhibition was reported to benefit the neural functional recovery and the axon regeneration after SCI. However, its role in de- and remyelination of axons in injured spinal cord is unclear. In the present study, we evaluated the effects of EGFR inhibitor, PD168393 (PD), on the myelination in mouse contusive SCI model. We found that expression of myelin basic protein (MBP) in the injured spinal cords of PD treated mice was remarkably elevated. The density of glial precursor cells and oligodendrocytes (OLs) was increased and the cell apoptosis in lesions was attenuated after PD168393 treatment. Moreover, PD168393 treatment reduced both the numbers of OX42 + microglial cells and glial fibrillary acidic protein + astrocytes in damaged area of spinal cords. We thus conclude that the therapeutic effects of EGFR inhibition after SCI involves facilitating remyelination of the injured spinal cord, increasing of oligodendrocyte precursor cells and OLs, as well as suppressing the activation of astrocytes and microglia/macrophages.

A study of methylprednisolone neuroprotection against acute injury to the rat spinal cord in vitro

Methylprednisolone sodium succinate (MPSS) has been proposed as a first-line treatment for acute spinal cord injury (SCI). Its clinical use remains, however, controversial because of the modest benefits and numerous side-effects. We investigated if MPSS could protect spinal neurons and glia using an in vitro model of the rat spinal cord that enables recording reflexes, fictive locomotion and morphological analysis of damage. With this model, a differential lesion affecting mainly either neurons or glia can be produced via kainate-evoked excitotoxicity or application of a pathological medium (lacking O2 and glucose), respectively. MPSS (6-10 μM) applied for 24 h after 1-h pathological medium protected astrocytes and oligodendrocytes especially in the ventrolateral white matter. This effect was accompanied by the return of slow, alternating oscillations (elicited by NMDA and 5-hydroxytryptamine (5-HT)) reminiscent of a sluggish fictive locomotor pattern. MPSS was, however, unable to reverse even a moderate neuronal loss and the concomitant suppression of fictive locomotion evoked by kainate (0.1 mM; 1 h). These results suggest that MPSS could, at least in part, contrast damage to spinal glia induced by a dysmetabolic state (associated to oxygen and glucose deprivation) and facilitate reactivation of spinal networks. Conversely, when even a minority of neurons was damaged by excitotoxicity, MPSS did not protect them nor did it restore network function in the current experimental model.

Stem cells in canine spinal cord injury--promise for regenerative therapy in a large animal model of human disease

The use of cell transplantation for spinal cord injury is a rapidly evolving field in regenerative medicine. Numerous animal models are currently being used. However, translation to human patients is still a challenging step. Dogs are of increasing importance as a translational model for human disease since there is a greater awareness of the need to increase the quality of preclinical data. The use of dogs ultimately brings benefit to both human and veterinary medicine. In this review we analyze experimental and clinical studies using cell transplantation for canine spinal cord injury. Overall, in experimental studies, transplantation groups showed improvement over control groups. Improvements were measured at the functional, electrophysiological, histological, RNA and protein levels. Most clinical studies support beneficial effects of cell transplantation despite the fact that methodological limitations preclude definitive conclusions. However, the mechanisms of action and underlying the behavior of transplanted cells in the injured spinal cord remain unclear. Overall, we conclude here that stem cell interventions are a promising avenue for the treatment of spinal cord injury. Canines are a promising model that may help bridge the gap between translational research and human clinical trials.

The Impact of Prestretch Induced Surface Anisotropy on Axon Regeneration

Nerve regeneration after spinal cord injury requires proper axon alignment to bridge the lesion site and myelination to achieve functional recovery. Significant effort has been invested in developing engineering approaches to induce axon alignment with less focus on myelination. Topological features, such as aligned fibers and channels, have been shown to induce axon alignment, but do not enhance axon thickness. We previously demonstrated that surface anisotropy generated through mechanical prestretch induced mesenchymal stem cells to align in the direction of prestretch. In this study, we demonstrate that static prestretch-induced anisotropy promotes dorsal root ganglion (DRG) neurons to extend thicker axon aggregates along the stretched direction and form aligned fascicular-like axon tracts. Moreover, Schwann cells, when cocultured with DRG neurons on the prestretched surface colocalized with the aligned axons and expressed P0 protein, are indicative of myelination of the aligned axons, thereby demonstrating that prestretch-induced surface anisotropy is beneficial in enhancing axon alignment, growth, and myelination.

Local Delivery of High-Dose Chondroitinase ABC in the Sub-Acute Stage Promotes Axonal Outgrowth and Functional Recovery after Complete Spinal Cord Transection

Chondroitin sulfate proteoglycans (CSPGs) are glial scar-associated molecules considered axonal regeneration inhibitors and can be digested by chondroitinase ABC (ChABC) to promote axonal regeneration after spinal cord injury (SCI). We previously demonstrated that intrathecal delivery of low-dose ChABC (1 U) in the acute stage of SCI promoted axonal regrowth and functional recovery. In this study, high-dose ChABC (50 U) introduced via intrathecal delivery induced subarachnoid hemorrhage and death within 48 h. However, most SCI patients are treated in the sub-acute or chronic stages, when the dense glial scar has formed and is minimally digested by intrathecal delivery of ChABC at the injury site. The present study investigated whether intraparenchymal delivery of ChABC in the sub-acute stage of complete spinal cord transection would promote axonal outgrowth and improve functional recovery. We observed no functional recovery following the low-dose ChABC (1 U or 5 U) treatments. Furthermore, animals treated with high-dose ChABC (50 U or 100 U) showed decreased CSPGs levels. The extent and area of the lesion were also dramatically decreased after ChABC treatment. The outgrowth of the regenerating axons was significantly increased, and some partially crossed the lesion site in the ChABC-treated groups. In addition, retrograde Fluoro-Gold (FG) labeling showed that the outgrowing axons could cross the lesion site and reach several brain stem nuclei involved in sensory and motor functions. The Basso, Beattie and Bresnahan (BBB) open field locomotor scores revealed that the ChABC treatment significantly improved functional recovery compared to the control group at eight weeks after treatment. Our study demonstrates that high-dose ChABC treatment in the sub-acute stage of SCI effectively improves glial scar digestion by reducing the lesion size and increasing axonal regrowth to the related functional nuclei, which promotes locomotor recovery. Thus, our results will aid in the treatment of spinal cord injury.

Reliability and validity of the capabilities of upper extremity test (CUE-T) in subjects with chronic spinal cord injury

OBJECTIVE

To determine the reliability and validity of the capabilities of upper extremity test (CUE-T), a measure of functional limitations, in patients with chronic tetraplegia.

DESIGN

Repeated measures.

SETTING

Outpatient rehabilitation center.

PARTICIPANTS

Fifty subjects (36 male/14 female) with spinal cord injury (SCI) of ≥1-year duration participated. Subjects were 17-81 years old (mean 48.1 ± 18.2); neurological levels ranged from C2 through T6, American Spinal Injury Association Impairment Scale grades A-D.

INTERVENTIONS

Not applicable.

OUTCOME MEASURES

Intraclass correlation coefficients (ICC), weighted kappa and repeatability values for CUE-T; Spearman correlations of CUE-T with upper extremity motor scores (UEMS), and self-care and mobility portions of the Spinal Cord Independence Measure, vIII (SCIM III).

RESULTS

Score ranges for UEMS were 8-50, CUE-T 7-135, self-care SCIM 0-20, and mobility SCIM 0-40. The ICC values for total, right, and left side scores were excellent (0.97-0.98; 95% confidence interval 0.96-0.99). Item weighted kappa values were ≥0.60 for all but five items, four of which were right and left pronation and supination. Repeatability of total score was 10.8 points, right and left sides 6.3 and 6.1 points. Spearman correlations of the total CUE-T with the UEMS and SCIM self-care and mobility scores were 0.83, 0.70, and 0.55 respectively.

CONCLUSIONS

The CUE-T displays excellent test-retest reliability, and good-excellent correlation with impairment and capacity measures in persons with chronic SCI. After revising pronation and supination test procedures, the sensitivity to change should be determined.

Current therapeutic strategies for inflammation following traumatic spinal cord injury

Damage from spinal cord injury occurs in two phases – the trauma of the initial mechanical insult and a secondary injury to nervous tissue spared by the primary insult. Apart from damage sustained as a result of direct trauma to the spinal cord, the post-traumatic inflammatory response contributes significantly to functional motor deficits exacerbated by the secondary injury. Attenuating the detrimental aspects of the inflammatory response is a promising strategy to potentially ameliorate the secondary injury, and promote significant functional recovery. This review details how the inflammatory component of secondary injury to the spinal cord can be treated currently and in the foreseeable future.

Persistent beneficial impact of H-reflex conditioning in spinal cord-injured rats

Operant conditioning of a spinal cord reflex can improve locomotion in rats and humans with incomplete spinal cord injury. This study examined the persistence of its beneficial effects. In rats in which a right lateral column contusion injury had produced asymmetric locomotion, up-conditioning of the right soleus H-reflex eliminated the asymmetry while down-conditioning had no effect. After the 50-day conditioning period ended, the H-reflex was monitored for 100 [±9 (SD)] (range 79-108) more days and locomotion was then reevaluated. After conditioning ended in up-conditioned rats, the H-reflex continued to increase, and locomotion continued to improve. In down-conditioned rats, the H-reflex decrease gradually disappeared after conditioning ended, and locomotion at the end of data collection remained as impaired as it had been before and immediately after down-conditioning. The persistence (and further progression) of H-reflex increase but not H-reflex decrease in these spinal cord-injured rats is consistent with the fact that up-conditioning improved their locomotion while down-conditioning did not. That is, even after up-conditioning ended, the up-conditioned H-reflex pathway remained adaptive because it improved locomotion. The persistence and further enhancement of the locomotor improvement indicates that spinal reflex conditioning protocols might supplement current therapies and enhance neurorehabilitation. They may be especially useful when significant spinal cord regeneration becomes possible and precise methods for retraining the regenerated spinal cord are needed.

Canine epidermal neural crest stem cells: characterization and potential as therapy candidate for a large animal model of spinal cord injury

The discovery of multipotent neural crest-derived stem cells, named epidermal neural crest stem cells (EPI-NCSC), that persist postnatally in an easy-to-access location-the bulge of hair follicles-opens a spectrum of novel opportunities for patient-specific therapies. We present a detailed characterization of canine EPI-NCSC (cEPI-NCSC) from multiple dog breeds and protocols for their isolation and ex vivo expansion. Furthermore, we provide novel tools for research in canines, which currently are still scarce. In analogy to human and mouse EPI-NCSC, the neural crest origin of cEPI-NCSC is shown by their expression of the neural crest stem cell molecular signature and other neural crest-characteristic genes. Similar to human EPI-NCSC, cEPI-NCSC also expressed pluripotency genes. We demonstrated that cEPI-NCSC can generate all major neural crest derivatives. In vitro clonal analyses established multipotency and self-renewal ability of cEPI-NCSC, establishing cEPI-NCSC as multipotent somatic stem cells. A critical analysis of the literature on canine spinal cord injury (SCI) showed the need for novel treatments and suggested that cEPI-NCSC represent viable candidates for cell-based therapies in dog SCI, particularly for chondrodystrophic dogs. This notion is supported by the close ontological relationship between neural crest stem cells and spinal cord stem cells. Thus, cEPI-NCSC promise to offer not only a potential treatment for canines but also an attractive and realistic large animal model for human SCI. Taken together, we provide the groundwork for the development of a novel cell-based therapy for a condition with extremely poor prognosis and no available effective treatment.

Motoneuron intrinsic properties, but not their receptive fields, recover in chronic spinal injury

Proper movement execution relies on precise input processing by spinal motoneurons (MNs). Spinal MNs are activated by limb joint rotations. Typically, their movement-related receptive fields (MRRFs) are sharply focused and joint-specific. After acute spinal transection MRRFs become wide, but their manifestation is not apparent, as intrinsic excitability, primarily resulting from the loss of persistent inward currents (PICs), dramatically decreases. PICs undergo a remarkable recovery with time after injury. Here we investigate whether MRRFs undergo a recovery that parallels that of the PIC. Using the chronic spinal cat in acute terminal decerebrate preparations, we found that MRRFs remain expanded 1 month after spinal transaction, whereas PICs recovered to >80% of their preinjury amplitudes. These recovered PICs substantially amplified the expanded inputs underlying the MRRFs. As a result, we show that single joint rotations lead to the activation of muscles across the entire limb. These results provide a potential mechanism for the propagation of spasms throughout the limb.

Remote neurodegeneration: multiple actors for one play

Remote neurodegeneration significantly influences the clinical outcome in many central nervous system (CNS) pathologies, such as stroke, multiple sclerosis, and traumatic brain and spinal cord injuries. Because these processes develop days or months after injury, they are accompanied by a therapeutic window of opportunity. The complexity and clinical significance of remote damage is prompting many groups to examine the factors of remote degeneration. This research is providing insights into key unanswered questions, opening new avenues for innovative neuroprotective therapies. In this review, we evaluate data from various remote degeneration models to describe the complexity of the systems that are involved and the importance of their interactions in reducing damage and promoting recovery after brain lesions. Specifically, we recapitulate the current data on remote neuronal degeneration, focusing on molecular and cellular events, as studied in stroke and brain and spinal cord injury models. Remote damage is a multifactorial phenomenon in which many components become active in specific time frames. Days, weeks, or months after injury onset, the interplay between key effectors differentially affects neuronal survival and functional outcomes. In particular, we discuss apoptosis, inflammation, oxidative damage, and autophagy-all of which mediate remote degeneration at specific times. We also review current findings on the pharmacological manipulation of remote degeneration mechanisms in reducing damage and sustaining outcomes. These novel treatments differ from those that have been proposed to limit primary lesion site damage, representing new perspectives on neuroprotection.

Locomotor impact of beneficial or nonbeneficial H-reflex conditioning after spinal cord injury

When new motor learning changes neurons and synapses in the spinal cord, it may affect previously learned behaviors that depend on the same spinal neurons and synapses. To explore these effects, we used operant conditioning to strengthen or weaken the right soleus H-reflex pathway in rats in which a right spinal cord contusion had impaired locomotion. When up-conditioning increased the H-reflex, locomotion improved. Steps became longer, and step-cycle asymmetry (i.e., limping) disappeared. In contrast, when down-conditioning decreased the H-reflex, locomotion did not worsen. Steps did not become shorter, and asymmetry did not increase. Electromyographic and kinematic analyses explained how H-reflex increase improved locomotion and why H-reflex decrease did not further impair it. Although the impact of up-conditioning or down-conditioning on the H-reflex pathway was still present during locomotion, only up-conditioning affected the soleus locomotor burst. Additionally, compensatory plasticity apparently prevented the weaker H-reflex pathway caused by down-conditioning from weakening the locomotor burst and further impairing locomotion. The results support the hypothesis that the state of the spinal cord is a "negotiated equilibrium" that serves all the behaviors that depend on it. When new learning changes the spinal cord, old behaviors undergo concurrent relearning that preserves or improves their key features. Thus, if an old behavior has been impaired by trauma or disease, spinal reflex conditioning, by changing a specific pathway and triggering a new negotiation, may enable recovery beyond that achieved simply by practicing the old behavior. Spinal reflex conditioning protocols might complement other neurorehabilitation methods and enhance recovery.