A characterization of white matter pathology following spinal cord compression injury in the rat

Novel Therapeutic Effects in Rat Spinal Cord Injuries: Recovery of the Definitive and Early Spinal Cord Injury by the Administration of Pentadecapeptide BPC 157 Therapy

Recently, marked therapeutic effects pertaining to the recovery of injured rat spinal cords (1 min compression injury of the sacrocaudal spinal cord (S2-Co1) resulting in tail paralysis) appeared after a single intraperitoneal administration of the stable gastric pentadecapeptide BPC 157 at 10 min post-injury. Besides the demonstrated rapid and sustained recovery (1 year), we showed the particular points of the immediate effect of the BPC 157 therapy that began rapidly after its administration, (i) soon after injury (10 min), or (ii) later (4 days), in the rats with a definitive spinal cord injury. Specifically, in counteracting spinal cord hematoma and swelling, (i) in rats that had undergone acute spinal cord injury, followed by intraperitoneal BPC 157 application at 10 min, we focused on the first 10–30 min post-injury period (assessment of gross, microscopic, and gene expression changes). Taking day 4 post-injury as the definitive injury, (ii) we focused on the immediate effects after the BPC 157 intragastric application over 20 min of the post-therapy period. Comparable long-time recovery was noted in treated rats which had definitive tail paralysis: (iii) the therapy was continuously given per orally in drinking water, beginning at day 4 after injury and lasting one month after injury. BPC 157 rats presented only discrete edema and minimal hemorrhage and increased Nos1, Nos2, and Nos3 values (30 min post-injury, (i)) or only mild hemorrhage, and only discrete vacuolation of tissue (day 4, (ii)). In the day 4–30 post-injury study (iii), BPC 157 rats rapidly presented tail function recovery, and no demyelination process (Luxol fast blue staining).

Temporal Progression of Acute Spinal Cord Injury Mechanisms in a Rat Model: Contusion, Dislocation, and Distraction

Traumatic spinal cord injuries (SCIs) occur due to different spinal column injury patterns, including burst fracture, dislocation, and flexion-distraction. Pre-clinical studies modeling different SCI mechanisms have shown distinct histological differences between these injuries both acutely (3 h and less) and chronically (8 weeks), but there remains a temporal gap. Different rates of injury progression at specific regions of the spinal cord may provide insight into the pathologies that are initiated by specific SCI mechanisms. Therefore, the objective of this study was to evaluate the temporal progression of injury at specific tracts within the white matter, for time-points of 3 h, 24 h, and 7 days, for three distinct SCI mechanisms. In this study, 96 male Sprague Dawley rats underwent one of three SCI mechanisms: contusion, dislocation, or distraction. Animals were sacrificed at one of three times post-injury: 3 h, 24 h, or 7 days. Histological analysis using eriochrome cyanide and immunostaining for MBP, SMI-312, neurofilament-H (NF-H), and β-III tubulin were used to characterize white matter sparing and axon and myelinated axon counts. The regions analyzed were the gracile fasciculus, cuneate fasciculus, dorsal corticospinal tract, and ventrolateral white matter. Contusion, dislocation, and distraction SCIs demonstrated distinct damage patterns that progressed differently over time. Myelinated axon counts were significantly reduced after dislocation and contusion injuries in most locations and time-points analyzed (compared with sham). This indicates early myelin damage often within 3 h. Myelinated axon counts after distraction dropped early and did not demonstrate any significant progression over the next 7 days. Important differences in white matter degeneration were identified between injury types, with distraction injuries showing the least variability across time-points These findings and the observation that white matter injury occurs early, and in many cases, without much dynamic change, highlight the importance of injury type in SCI research-both clinically and pre-clinically.

An injectable and self-healing hydrogel with controlled release of curcumin to repair spinal cord injury

The harsh local micro-environment following spinal cord injury (SCI) remains a great challenge for neural regeneration. Local reconstitution of a favorable micro-environment by biocompatible scaffolds with desirable functions has thus been an area of concern. Herein, a hybrid hydrogel was developed using Fmoc-grafted chitosan (FC) and Fmoc peptide (FI). Dynamic reversible π-π stacking interactions of the fluorenyl rings enabled the FC/FI hybrid hydrogel to exhibit excellent injectable and self-healing properties, as characterized by visual appearances and rheological tests. Furthermore, the FC/FI hybrid hydrogel showed a slow and persistent release of curcumin (Cur), which was named as FC/FI-Cur hydrogel. In vitro studies confirmed that with the support of FC/FI-Cur hydrogel, neurite outgrowth was promoted, and Schwann cell (SC) migration away from dorsal root ganglia (DRG) spheres with enhanced myelination was substantiated. The FC/FI-Cur hydrogel well reassembled extracellular matrix at the lesion site of rat spinal cord and exerted outstanding effects in modulating local inflammatory reaction by regulating the phenotypes of infiltrated inflammatory cells. In addition, endogenous SCs were recruited in the FC/FI-Cur graft and participated in the remyelination process of the regenerated nerves. These outcomes favored functional recovery, as evidenced by improved hind limbs movement and enhanced electrophysiological properties. Thus, our study not only advanced the development of multifunctional hydrogels but also provided insights into comprehensive approaches for SCI repair.

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FC/FI hydrogel exhibited excellent injectable, self-healing properties, and performed well in releasing curcumin (Cur).

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FC/FI-Cur hydrogel promoted neurite outgrowth and myelination in vitro.

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FC/FI-Cur modulated local inflammatory reaction and recruited Schwann cells to repair spinal cord injury.

Time-Course Changes of Extracellular Matrix Encoding Genes Expression Level in the Spinal Cord Following Contusion Injury-A Data-Driven Approach

The involvement of the extracellular matrix (ECM) in lesion evolution and functional outcome is well recognized in spinal cord injury. Most attention has been dedicated to the “core” area of the lesion and scar formation, while only scattered reports consider ECM modification based on the temporal evolution and the segments adjacent to the lesion. In this study, we investigated the expression profile of 100 genes encoding for ECM proteins at 1, 8 and 45 days post-injury, in the spinal cord segments rostral and caudal to the lesion and in the scar segment, in a rat model. During both the active lesion phases and the lesion stabilization, we observed an asymmetric gene expression induced by the injury, with a higher regulation in the rostral segment of genes involved in ECM remodeling, adhesion and cell migration. Using bioinformatic approaches, the metalloproteases inhibitor Timp1 and the hyaluronan receptor Cd44 emerged as the hub genes at all post-lesion times. Results from the bioinformatic gene expression analysis were then confirmed at protein level by tissue analysis and by cell culture using primary astrocytes. These results indicated that ECM regulation also takes place outside of the lesion area in spinal cord injury.

Quantification of Myelinated Nerve Fraction and Degeneration in Spinal Cord Neuropil by SHIFT MRI

BACKGROUND

Neurodegeneration is a complex cellular process linked to prompt changes in myelin integrity and gradual neuron loss. Current imaging techniques offer estimations of myelin volumes in lesions/remyelinated areas but are limited to detect subtle injury.

PURPOSE

To investigate whether measurements detected by a signal hierarchically isolated as a function of time-to-echo (SHIFT) MRI technique can determine changes in myelin integrity and fiber axolemma.

STUDY TYPE

Prospective animal model.

ANIMAL MODEL

Surgically demyelinated spinal cord (SC) injury model in rodents (n = 6).

FIELD STRENGTH/SEQUENCE

Gradient-echo spin-echo at 3T.

ASSESSMENT

Multicompartment T₂ relaxations were computed by SHIFT MRI in 75-microns-resolution images of the SC injury penumbra region 2 weeks post-trauma. G-ratio and axolemma delamination were assessed by transmission electron microscopy (TEM) in intact and injured samples. SC myelinated nerve fraction was computed by SHIFT MRI prospectively and assessed histologically.

STATISTICAL TESTS

Relations between SHIFT-isolated T₂ -components and TEM measurements were studied using linear regression and t-tests. Pearson's correlation and significance were computed to determine the SHIFT's sensitivity to detect myelinated fibers ratio in gray matter. Regularized least-squares-based ranking analysis was employed to determine SHIFT MRI's ability to discern intact and injured myelinated nerves.

RESULTS

Biexponential signals isolated by SHIFT MRI for intact vs. lesion penumbra exhibited changes in T₂ , shifting from intermediate components (25 ± 2 msec) to long (43 ± 11 msec) in white matter, and similarly in gray matter regions-of-interest (31 ± 2 to 46 ± 16 msec). These changes correlated highly with TEM g-ratio and axon delamination measurements (P < 0.05). Changes in short T₂ components were observed but not statistically significant (8.5 ± 0.5 to 7 ± 3 msec, P = 0.445, and 4.0 ± 0.9 to 7 ± 3 msec, P = 0.075, respectively). SHIFT MRI's ability to detect myelinated fibers within gray matter was confirmed (P < 0.001).

DATA CONCLUSION

Changes detected by SHIFT MRI are associated with abnormal intermembrane spaces formed upon mild injury, directly correlated with early neuro integrity loss. Level of Evidence 1 Technical Efficacy Stage 2.

The Parietal Atrophy Score on Brain Magnetic Resonance Imaging is a Reliable Visual Scale

Aims

The purpose of the study was to evaluate the reliability of our new visual scale for a quick atrophy assessment of parietal lobes on brain Magnetic Resonance Imaging (MRI) among different professionals. A good agreement would justify its use for differential diagnosis of neurodegenerative dementias, especially early-onset Alzheimer’s Disease (AD), in clinical settings.

Methods

The visual scale named the Parietal Atrophy Score (PAS) is based on a semi-quantitative assessment ranging from 0 (no atrophy) to 2 (prominent atrophy) in three parietal structures (sulcus cingularis posterior, precuneus, parietal gyri) on T1-weighted MRI coronal slices through the whole parietal lobes. We used kappa statistics to evaluate intra-rater and inter-rater agreement among four raters who independently scored parietal atrophy using PAS. Rater 1 was a neuroanatomist (JM), rater 2 was an expert in MRI acquisition and analysis (II), rater 3 was a medical student (OP) and rater 4 was a neurologist (DS) who evaluated parietal atrophy twice in a 3-month interval to assess intra-rater agreement. All raters evaluated the same 50 parietal lobes on brain MRI of 25 cognitively normal individuals with even distribution across all atrophy degrees from none to prominent according to the neurologist’s rating.

Results

Intra-rater agreement was almost perfect with the kappa value of 0.90. Inter-rater agreement was moderate to substantial with kappa values ranging from 0.43-0.86.

Conclusion

The Parietal Atrophy Score is the reliable visual scale among raters of different professions for a quick evaluation of parietal lobes on brain MRI within 1-2 minutes. We believe it could be used as an adjunct measure in differential diagnosis of dementias, especially early-onset AD.

Engineering Microenvironment for Endogenous Neural Regeneration after Spinal Cord Injury by Reassembling Extracellular Matrix

The formation of a fluid-filled cystic cavity after spinal cord injury (SCI) is a major obstacle for neural regeneration. In this study, the post-SCI cavity was bridged by a functional self-assembling peptide (F-SAP) nanofiber hydrogel coupled with growth factor "cocktail". A sustained release of growth factors was achieved by carefully tailoring the physical hindrances and charge-induced interactions between the growth factors and the peptide nanofibers. Such an engineering microenvironment elicited axon regeneration, as determined by tracing of the descending pathway in the dorsal columns and immunochemical detection of regenerating axons beyond the lesion. Furthermore, the dynamic spatiotemporal activation line of endogenous NSCs (eNSCs) after severe SCI was thoroughly investigated. The results indicated that the growth factor-coupled F-SAP greatly facilitated eNSC proliferation, neuronal differentiation, maturation, myelination, and more importantly, the formation of interconnection with severed descending corticospinal tracts. The robust endogenous neurogenesis essentially led to the recovery of locomotion and electrophysiological properties. In conclusion, the growth factor-coupled F-SAP nanofiber hydrogel elucidated the therapeutic effect of eliciting endogenous neurogenesis by locally reassembling an extracellular matrix.

Therapeutic target for external beam x-irradiation in experimental spinal cord injury

OBJECTIVE

X-irradiation has been shown to be beneficial to recovery from spinal cord injury (SCI); however, the optimal therapeutic target has not been defined. Experiments were designed to determine the optimal target volume within the injured spinal cord for improving functional recovery and sparing tissue with stereotactic x-irradiation.

METHODS

SCI was produced in rats at the T10 level. A 20-Gy dose of radiation was delivered with a single, 4-mm-diameter, circular radiation beam centered either on the injury epicenter or 4 or 8 mm caudal or rostral to the injury epicenter. Locomotor function was determined for 6 weeks with the Basso, Beattie, and Bresnahan locomotor scale and tissue sparing by histological analysis of transverse sections along the spinal cords.

RESULTS

X-irradiation of spinal cord segments at 4 mm, but not 8 mm, caudal or rostral to the contusion epicenter resulted in increases in locomotor recovery. Consistently, significant tissue sparing also occurred with x-irradiation centered at those sites, although irradiation centered 4 mm rostral to the epicenter led to tissue sparing along the greatest length of the spinal cord. Interestingly, regression analysis of these variables demonstrated that the quantitative relationship between the amount of tissue spared and the improvement in locomotion recovery was greatest in a region several millimeters rostral to the injury epicenter.

CONCLUSIONS

These results indicate that x-irradiation in a region rostral to the injury epicenter is optimal for recovery from SCI. This minimal target should be attractive for therapeutic application since it allows a greatly reduced target volume so that uninjured tissue is not needlessly irradiated.

Neuroprotective potential of Spirulina platensis on lesioned spinal cord corticospinal tract under experimental conditions in rat models

Spinal cord injury (SCI) results from penetrating or compressive traumatic injury to the spine in humans or by the surgical compression of the spinal cord in experimental animals. In this study, the neuroprotective potential of Spirulina platensis was investigated on ultrastructural and functional recovery of the spinal cord following surgical-induced injury. Twenty-four Sprague-Dawley rats were divided into three groups; sham group, control (trauma) group, and experimental (S. platensis) group (180 mg/kg) of eight rats each. For each group, the rats were then subdivided into two groups to allow measurement at two different timepoints (day 14 and 28) for the microscopic analysis. Rats in the control and experimental S. platensis groups were subjected to partial crush injury at the level of T12 with Inox number 2 modified forceps by compressing on the spinal cord for 30 s. Pairwise comparisons of ultrastructural grading mean scores difference between the control and experimental S. platensis groups reveals that there were significant differences on the axonal ultrastructure, myelin sheath and BBB Score on Day 28; these correlate with the functional locomotor recovery at this timepoint. The results suggest that supplementation with S. platensis induces functional recovery and effective preservation of the spinal cord ultrastructure after SCI. These findings will open new potential avenue for further research into the mechanism of S. platensis-mediated spinal cord repair.

Stable gastric pentadecapeptide BPC 157 can improve the healing course of spinal cord injury and lead to functional recovery in rats

BACKGROUND

We focused on the therapeutic effects of the stable gastric pentadecapeptide BPC 157 in spinal cord injury using a rat model. BPC 157, of which the LD1 has not been achieved, has been implemented as an anti-ulcer peptide in inflammatory bowel disease trials and recently in a multiple sclerosis trial. In animals, BPC 157 has an anti-inflammatory effect and therapeutic effects in functional recovery and the rescue of somatosensory neurons in the sciatic nerve after transection, upon brain injury after concussive trauma, and in severe encephalopathies. Additionally, BPC 157 affects various molecular pathways.

METHODS

Therefore, BPC 157 therapy was administered by a one-time intraperitoneal injection (BPC 157 (200 or 2 μg/kg) or 0.9% NaCl (5 ml/kg)) 10 min after injury. The injury procedure involved laminectomy (level L2-L3) and a 60-s compression (neurosurgical piston (60-66 g) of the exposed dural sac of the sacrocaudal spinal cord). Assessments were performed at 1, 4, 7, 15, 30, 90, 180, and 360 days after injury.

RESULTS

All of the injured rats that received BPC 157 exhibited consistent clinical improvement, increasingly better motor function of the tail, no autotomy, and resolved spasticity by day 15. BPC 157 application largely counteracted changes at the microscopic level, including the formation of vacuoles and the loss of axons in the white matter, the formation of edema and the loss of motoneurons in the gray matter, and a decreased number of large myelinated axons in the rat caudal nerve from day 7. EMG recordings showed a markedly lower motor unit potential in the tail muscle.

CONCLUSION

Axonal and neuronal necrosis, demyelination, and cyst formation were counteracted. The functional rescue provided by BPC 157 after spinal cord injury implies that BPC 157 therapy can impact all stages of the secondary injury phase.

Axonal degeneration and demyelination following traumatic spinal cord injury: A systematic review and meta-analysis

The pathophysiology of spinal cord injury (SCI) related processes of axonal degeneration and demyelination are poorly understood. The present systematic review and meta-analysis were performed such to establish quantitative results of animal studies regarding the role of injury severity, SCI models and level of injury on the pathophysiology of axon and myelin sheath degeneration. 39 related articles were included in the analysis. The compiled data showed that the total number of axons, number of myelinated axons, myelin sheath thickness, axonal conduction velocity, and internode length steadily decreased as time elapsed from the injury (P_{for trend}<0.0001). The rate of axonal retrograde degeneration was affected by SCI model and severity of the injury. Axonal degeneration was higher in injuries of the thoracic region. The SCI model and the site of the injury also affected axonal retrograde degeneration. The number of myelinated axons in the caudal region of the injury was significantly higher than the lesion site and the rostral region. The findings of the present meta-analysis show that the pathophysiology of axons and myelin sheath differ in various phases of SCI and are affected by multiple factors related to the injury.

Mesenchymal stem cells and the neuronal microenvironment in the area of spinal cord injury

Cell-based technologies are used as a therapeutic strategy in spinal cord injury (SCI). Mesenchymal stem cells (MSCs), which secrete various neurotrophic factors and cytokines, have immunomodulatory, anti-apoptotic and anti-inflammatory effects, modulate reactivity/phenotype of astrocytes and the microglia, thereby promoting neuroregeneration seem to be the most promising. The therapeutic effect of MSCs is due to a paracrine mechanism of their action, therefore the survival of MSCs and their secretory phenotype is of particular importance. Nevertheless, these data are not always reported in efficacy studies of MSC therapy in SCI. Here, we provide a review with summaries of preclinical trials data evaluating the efficacy of MSCs in animal models of SCI. Based on the data collected, we have tried (1) to establish the behavior of MSCs after transplantation in SCI with an evaluation of cell survival, migration potential, distribution in the area of injured and intact tissue and possible differentiation; (2) to determine the effects MSCs on neuronal microenvironment and correlate them with the efficacy of functional recovery in SCI; (3) to ascertain the conditions under which MSCs demonstrate their best survival and greatest efficacy.

Testing Pathological Variation of White Matter Tract in Adult Rats after Severe Spinal Cord Injury with MRI

The purpose of this study was to assess the pathological variation in white matter tracts in the adult severe thoracic contusion spinal cord injury (SCI) rat models combined with in vivo magnetic resonance imaging (MRI), as well as the effect of spared white matter (WM) quantity on hindlimb motor function recovery. 7.0T MRI was conducted for all experimental animals before SCI and 1, 3, 7, and 14 days after SCI. The variation in the white matter tract in different regions of the spinal cord after SCI was examined by luxol fast blue (LFB) staining, NF200 immunochemistry, and diffusion tensor imaging (DTI) parameters, including fraction anisotropy, mean diffusivity, axial diffusion, and radial diffusivity. Meanwhile, Basso-Beattie-Bresnahan (BBB) open-field scoring was performed to evaluate the behavior of the paraplegic hind limbs. The quantitative analysis showed that spared white matter measures assessed by LFB and MRI had a close correlation (R² = 0.8508). The percentage of spared white matter area was closely correlated with BBB score (R² = 0.8460). After SCI, spared white matter in the spinal cord, especially the ventral column WM, played a critical role in motor function restoration. The results suggest that the first three days provides a key time window for SCI protection and treatment; spared white matter, especially in the ventral column, plays a key role in motor function recovery in rats. Additionally, DTI may be an important noninvasive technique to diagnose acute SCI degree as well as a tool to evaluate functional prognosis. During the transition from nerve protection toward clinical treatment after SCI, in vivo DTI may serve as an emerging noninvasive technique to diagnose acute SCI degree and predict the degree of spontaneous functional recovery after SCI.

Dorsal and ventral horn atrophy is associated with clinical outcome after spinal cord injury

OBJECTIVE

To investigate whether gray matter pathology above the level of injury, alongside white matter changes, also contributes to sensorimotor impairments after spinal cord injury.

METHODS

A 3T MRI protocol was acquired in 17 tetraplegic patients and 21 controls. A sagittal T2-weighted sequence was used to characterize lesion severity. At the C2-3 level, a high-resolution T2*-weighted sequence was used to assess cross-sectional areas of gray and white matter, including their subcompartments; a diffusion-weighted sequence was used to compute voxel-based diffusion indices. Regression models determined associations between lesion severity and tissue-specific neurodegeneration and associations between the latter with neurophysiologic and clinical outcome.

RESULTS

Neurodegeneration was evident within the dorsal and ventral horns and white matter above the level of injury. Tract-specific neurodegeneration was associated with prolonged conduction of appropriate electrophysiologic recordings. Dorsal horn atrophy was associated with sensory outcome, while ventral horn atrophy was associated with motor outcome. White matter integrity of dorsal columns and corticospinal tracts was associated with daily-life independence.

CONCLUSION

Our results suggest that, next to anterograde and retrograde degeneration of white matter tracts, neuronal circuits within the spinal cord far above the level of injury undergo transsynaptic neurodegeneration, resulting in specific gray matter changes. Such improved understanding of tissue-specific cord pathology offers potential biomarkers with more efficient targeting and monitoring of neuroregenerative (i.e., white matter) and neuroprotective (i.e., gray matter) agents.

Melatonin for the treatment of spinal cord injury

Spinal cord injury (SCI) from trauma or disease severely impairs sensory and motor function. Neurorehabilitation after SCI is a complex medical process that focuses on improving neurologic function and repairing damaged connections in the central nervous system. An increasing number of preclinical studies suggest that melatonin may be useful for the treatment of SCI. Melatonin is an indolamine that is primarily secreted by the pineal gland and known to be regulated by photoperiodicity. However, it is also a versatile hormone with antioxidative, antiapoptotic, neuroprotective, and anti-inflammatory properties. Here, we review the neuroprotective properties of melatonin and the potential mechanisms by which it might be beneficial in the treatment of SCI. We also describe therapies that combine melatonin with exercise, oxytetracycline, and dexamethasone to attenuate the secondary injury after SCI and limit potential side effects. Finally, we discuss how injury at different spinal levels may differentially affect the secretion of melatonin.

Neuroprotective effect of local hypothermia in a computer-controlled compression model in minipig: Correlation of tissue sparing along the rostro-caudal axis with neurological outcome

This study investigated the neuroprotective efficacy of local hypothermia in a minipig model of spinal cord injury (SCI) induced by a computer-controlled impactor device. The tissue integrity observed at the injury epicenter, and up to 3 cm cranially and caudally from the lesion site correlated with motor function. A computer-controlled device produced contusion lesions at L3 level with two different degrees of tissue sparing, depending upon pre-set impact parameters (8N- and 15N-force impact). Hypothermia with cold (4°C) saline or Dulbecco's modified Eagle's medium (DMEM)/F12 culture medium was applied 30 min after SCI (for 5 h) via a perfusion chamber (flow 2 ml/min). After saline hypothermia, the 8N-SCI group achieved faster recovery of hind limb function and the ability to walk from one to three steps at nine weeks in comparison with non-treated animals. Such improvements were not observed in saline-treated animals subjected to more severe 15N-SCI or in the group treated with DMEM/F12 medium. It was demonstrated that the tissue preservation in the cranial and caudal segments immediately adjacent to the lesion, and neurofilament protection in the lateral columns may be essential for modulation of the key spinal microcircuits leading to a functional outcome. Tissue sparing observed only in the caudal sections, even though significant, was not sufficient for functional improvement in the 15N-SCI model.

Fractional anisotropy is a marker in early-stage spinal cord injury

This study was designed to investigate whether fractional anisotropy (FA) contributes to study pathologic changes in SCI. Here rats were divided into a control group and three injury groups. Those in the injury groups were administered a mild, moderate, and severe contusion injury at the T10 vertebral level, respectively. Three rats were randomly selected from each group at 6, 24 and 72h after SCI for imaging examination. Magnetic resonance diffusion tensor imaging was FA and tractography. Once magnetic resonance was completed, blood was collected and serum levels of neuron specific enolase (NSE) and soluble protein-100β (S-100β) were determined. Then animals were sacrificed and histopathologic examination was conducted. The spinal cord in the SCI model rats produced prominent tissue damages characterized by neuronal injury in the affected regions. An obvious decrease in FA happened 24h after SCI, and at 72h, FA tended to be stable. There were significant differences in the serum levels of NSE and S-100β between 6h and 24h, respectively. FA significantly related with the serum testing results at 24h. FA may be used as a marker for different severities of SCI. The optimal time for examination is at 24h post-injury in rat.

Biomaterials for Local, Controlled Drug Delivery to the Injured Spinal Cord

Affecting approximately 17,000 new people each year, spinal cord injury (SCI) is a devastating injury that leads to permanent paraplegia or tetraplegia. Current pharmacological approaches are limited in their ability to ameliorate this injury pathophysiology, as many are not delivered locally, for a sustained duration, or at the correct injury time point. With this review, we aim to communicate the importance of combinatorial biomaterial and pharmacological approaches that target certain aspects of the dynamically changing pathophysiology of SCI. After reviewing the pathophysiology timeline, we present experimental biomaterial approaches to provide local sustained doses of drug. In this review, we present studies using a variety of biomaterials, including hydrogels, particles, and fibers/conduits for drug delivery. Subsequently, we discuss how each may be manipulated to optimize drug release during a specific time frame following SCI. Developing polymer biomaterials that can effectively release drug to target specific aspects of SCI pathophysiology will result in more efficacious approaches leading to better regeneration and recovery following SCI.

Vitamin D and remyelination in multiple sclerosis

INTRODUCTION

Several studies have found an association between multiple sclerosis and vitamin D (VD) deficiency, which suggests that VD may play a role in the immune response. However, few studies have addressed its role in remyelination.

DEVELOPMENT

The VD receptor and the enzymes transforming VD into metabolites which activate the VD receptor are expressed in central nervous system (CNS) cells, which suggests a potential effect of VD on the CNS. Both in vitro and animal model studies have shown that VD may play a role in myelination by acting on factors that influence the microenvironment which promotes both proliferation and differentiation of neural stem cells into oligodendrocyte progenitor cells and oligodendrocytes. It remains unknown whether the mechanisms of internalisation of VD in the CNS are synergistic with or antagonistic to the mechanisms that facilitate the entry of VD metabolites into immune cells.

CONCLUSIONS

VD seems to play a role in the CNS and our hypothesis is that VD is involved in remyelination. Understanding the basic mechanisms of VD in myelination is necessary to manage multiple sclerosis patients with VD deficiency.

Amyloid Proteins and Their Role in Multiple Sclerosis. Considerations in the Use of Amyloid-PET Imaging

Thioflavin T derivatives are used in positron-emission tomography (PET) studies to detect amyloid protein deposits in patients with Alzheimer disease. These tracers bind extensively to white matter, which suggests that they may be useful in studies of multiple sclerosis (MS), and that proteins resulting from proteolytic processing of the amyloid precursor protein (APP) may contribute to MS. This article reviews data from both clinical and preclinical studies addressing the role of these proteins, whether they are detected in CSF studies or using PET imaging. APP is widely expressed in demyelinated axons and may have a protective effect in MS and in experimental allergic encephalomyelitis in animals. Several mechanisms associated with this increased expression may affect the degree of remyelination in MS. Amyloid-PET imaging may help determine the degree of demyelination and provide information on the molecular changes linked to APP proteolytic processing experienced by patients with MS.

Longitudinal study on diffusion tensor imaging and diffusion tensor tractography following spinal cord contusion injury in rats

INTRODUCTION

Diffusion tensor imaging (DTI) as a potential technology has been used in spinal cord injury (SCI) studies, but the longitudinal evaluation of DTI parameters after SCI, and the correlation between DTI parameters and locomotor outcomes need to be defined.

METHODS

Adult Wistar rats (n = 6) underwent traumatic thoracic cord contusion by an NYU impactor. DTI and Basso-Beattie-Bresnahan datasets were collected pre-SCI and 1, 3, 7, 14, and 84 days post-SCI. Diffusion tensor tractography (DTT) of the spinal cord was also generated. Fractional anisotropy (FA) and connection rate of fibers at the injury epicenter and at 5 mm rostral/caudal to the epicenter were calculated. The variations of these parameters after SCI were observed by one-way analysis of variance and the correlations between these parameters and motor function were explored by Pearson's correlation.

RESULTS

FA at the epicenter decreased most remarkably on day 1 post-SCI (from 0.780 ± 0.012 to 0.330 ± 0.015), and continued to decrease slightly by day 3 post-SCI (0.313 ± 0.015), while other parameters decreased significantly over the first 3 days after SCI. DTT showed residual fibers concentrated on ventral and ventrolateral sides of the cord. Moreover, FA at the epicenter exhibited the strongest correlation (r = 0.887, p = 0.000) with the locomotion performance.

CONCLUSION

FA was sensitive to degeneration in white matter and DTT could directly reflect the distribution of the residual white matter. Moreover, days 1 to 3 post-SCI may be the optimal time window for SCI examination and therapy.

Tamoxifen Promotes Axonal Preservation and Gait Locomotion Recovery after Spinal Cord Injury in Cats

We performed experiments in cats with a spinal cord penetrating hemisection at T13-L1 level, with and without tamoxifen treatment. The results showed that the numbers of the ipsilateral and contralateral ventral horn neurons were reduced to less than half in the nontreated animals compared with the treated ones. Also, axons myelin sheet was preserved to almost normal values in treated cats. On the contrary, in the untreated animals, their myelin sheet was reduced to 28% at 30 days after injury (DAI), in both the ipsilateral and contralateral regions of the spinal cord. Additionally, we made hindlimb kinematics experiments to study the effects of tamoxifen on cat locomotion after the injury: at 4, 16, and 30 DAI. We observed that the ipsilateral hindlimb angular displacement (AD) of the pendulum-like movements (PLM) during gait locomotion was recovered to almost normal values in treated cats. Contralateral PLM acquired similar values to those obtained in intact cats. At 4 DAI, untreated animals showed a compensatory increment of PLM occurring in the contralateral hindlimb, which was partially recovered at 30 DAI. Our findings indicate that tamoxifen exerts a neuroprotective effect and preserves or produces myelinated axons, which could benefit the locomotion recovery in injured cats.

The Ubiquitin-Proteasome System: Potential Therapeutic Targets for Alzheimer's Disease and Spinal Cord Injury

The ubiquitin-proteasome system (UPS) is a crucial protein degradation system in eukaryotes. Herein, we will review advances in the understanding of the role of several proteins of the UPS in Alzheimer’s disease (AD) and functional recovery after spinal cord injury (SCI). The UPS consists of many factors that include E3 ubiquitin ligases, ubiquitin hydrolases, ubiquitin and ubiquitin-like molecules, and the proteasome itself. An extensive body of work links UPS dysfunction with AD pathogenesis and progression. More recently, the UPS has been shown to have vital roles in recovery of function after SCI. The ubiquitin hydrolase (Uch-L1) has been proposed to increase cellular levels of mono-ubiquitin and hence to increase rates of protein turnover by the UPS. A low Uch-L1 level has been linked with Aβ accumulation in AD and reduced neuroregeneration after SCI. One likely mechanism for these beneficial effects of Uch-L1 is reduced turnover of the PKA regulatory subunit and consequently, reduced signaling via CREB. The neuron-specific F-box protein Fbx2 ubiquitinates β-secretase thus targeting it for proteasomal degradation and reducing generation of Aβ. Both Uch-L1 and Fbx2 improve synaptic plasticity and cognitive function in mouse AD models. The role of Fbx2 after SCI has not been examined, but abolishing ß-secretase reduces neuronal recovery after SCI, associated with reduced myelination. UBB+1, which arises through a frame-shift mutation in the ubiquitin gene that adds 19 amino acids to the C-terminus of ubiquitin, inhibits proteasomal function and is associated with increased neurofibrillary tangles in patients with AD, Pick’s disease and Down’s syndrome. These advances in understanding of the roles of the UPS in AD and SCI raise new questions but, also, identify attractive and exciting targets for potential, future therapeutic interventions.

NT3-chitosan elicits robust endogenous neurogenesis to enable functional recovery after spinal cord injury

Neural stem cells (NSCs) in the adult mammalian central nervous system (CNS) hold the key to neural regeneration through proper activation, differentiation, and maturation, to establish nascent neural networks, which can be integrated into damaged neural circuits to repair function. However, the CNS injury microenvironment is often inhibitory and inflammatory, limiting the ability of activated NSCs to differentiate into neurons and form nascent circuits. Here we report that neurotrophin-3 (NT3)-coupled chitosan biomaterial, when inserted into a 5-mm gap of completely transected and excised rat thoracic spinal cord, elicited robust activation of endogenous NSCs in the injured spinal cord. Through slow release of NT3, the biomaterial attracted NSCs to migrate into the lesion area, differentiate into neurons, and form functional neural networks, which interconnected severed ascending and descending axons, resulting in sensory and motor behavioral recovery. Our study suggests that enhancing endogenous neurogenesis could be a novel strategy for treatment of spinal cord injury.

A nutrient combination designed to enhance synapse formation and function improves outcome in experimental spinal cord injury

Spinal cord injury leads to major neurological impairment for which there is currently no effective treatment. Recent clinical trials have demonstrated the efficacy of Fortasyn® Connect in Alzheimer's disease. Fortasyn® Connect is a specific multi-nutrient combination containing DHA, EPA, choline, uridine monophosphate, phospholipids, and various vitamins. We examined the effect of Fortasyn® Connect in a rat compression model of spinal cord injury. For 4 or 9 weeks following the injury, rats were fed either a control diet or a diet enriched with low, medium, or high doses of Fortasyn® Connect. The medium-dose Fortasyn® Connect-enriched diet showed significant efficacy in locomotor recovery after 9 weeks of supplementation, along with protection of spinal cord tissue (increased neuronal and oligodendrocyte survival, decreased microglial activation, and preserved axonal integrity). Rats fed the high-dose Fortasyn® Connect-enriched diet for 4 weeks showed a much greater enhancement of locomotor recovery, with a faster onset, than rats fed the medium dose. Bladder function recovered quicker in these rats than in rats fed the control diet. Their spinal cord tissues showed a smaller lesion, reduced neuronal and oligodendrocyte loss, decreased neuroinflammatory response, reduced astrocytosis and levels of inhibitory chondroitin sulphate proteoglycans, and better preservation of serotonergic axons than those of rats fed the control diet. These results suggest that this multi-nutrient preparation has a marked therapeutic potential in spinal cord injury, and raise the possibility that this original approach could be used to support spinal cord injured patients.

Toll-Like Receptors and Dectin-1, a C-Type Lectin Receptor, Trigger Divergent Functions in CNS Macrophages

Spinal cord injury (SCI) activates macrophages, endowing them with both reparative and pathological functions. The mechanisms responsible for these divergent functions are unknown but are likely controlled through stochastic activation of different macrophage receptor subtypes. Various danger-associated molecular patterns released from dying cells in the injured spinal cord likely activate distinct subtypes of macrophage pattern recognition receptors, including bacterial toll-like receptors (TLRs) and fungal C-type lectin receptors (e.g., dectin-1). To determine the in vivo consequences of activating these receptors, ligands specific for TLR2 or dectin-1 were microinjected, alone or in combination, into intact spinal cord. Both ligands elicit a florid macrophage reaction; however, only dectin-1 activation causes macrophage-mediated demyelination and axonal injury. Coactivating TLR2 reduced the injurious effects of dectin-1 activation. When injected into traumatically injured spinal cord, TLR2 agonists enhance the endogenous macrophage reaction while conferring neuroprotection. Indeed, dieback of axons was reduced, leading to smaller lesion volumes at the peak of the macrophage response. Moreover, the density of NG2+ cells expressing vimentin increased in and near lesions that were enriched with TLR2-activated macrophages. In dectin-1-null mutant (knock-out) mice, dieback of corticospinal tract axons also is reduced after SCI. Collectively, these data support the hypothesis that the ability of macrophages to create an axon growth-permissive microenvironment or cause neurotoxicity is receptor dependent and it may be possible to exploit this functional dichotomy to enhance CNS repair.

SIGNIFICANCE STATEMENT

There is a growing appreciation that macrophages exert diverse functions in the injured and diseased CNS. Indeed, both macrophage-mediated repair and macrophage-mediated injury occur, and often these effector functions are elicited simultaneously. Understanding the mechanisms governing the reparative and pathological properties of activated macrophages is at the forefront of neuroscience research. In this report, using in vitro and in vivo models of relevance to traumatic spinal cord injury (SCI), new data indicate that stochastic activation of toll-like and c-type lectin receptors on macrophages causes neuroprotection or neurotoxicity, respectively. Although this manuscript focuses on SCI, these two innate immune receptor subtypes are also involved in developmental processes and become activated in macrophages that respond to various neurological diseases.

Therapeutic Hypothermia in Spinal Cord Injury: The Status of Its Use and Open Questions

Spinal cord injury (SCI) is a major health problem and is associated with a diversity of neurological symptoms. Pathophysiologically, dysfunction after SCI results from the culmination of tissue damage produced both by the primary insult and a range of secondary injury mechanisms. The application of hypothermia has been demonstrated to be neuroprotective after SCI in both experimental and human studies. The myriad of protective mechanisms of hypothermia include the slowing down of metabolism, decreasing free radical generation, inhibiting excitotoxicity and apoptosis, ameliorating inflammation, preserving the blood spinal cord barrier, inhibiting astrogliosis, promoting angiogenesis, as well as decreasing axonal damage and encouraging neurogenesis. Hypothermia has also been combined with other interventions, such as antioxidants, anesthetics, alkalinization and cell transplantation for additional benefit. Although a large body of work has reported on the effectiveness of hypothermia as a neuroprotective approach after SCI and its application has been translated to the clinic, a number of questions still remain regarding its use, including the identification of hypothermia's therapeutic window, optimal duration and the most appropriate rewarming rate. In addition, it is necessary to investigate the neuroprotective effect of combining therapeutic hypothermia with other treatment strategies for putative synergies, particularly those involving neurorepair.

Exercise promotes motor functional recovery in rats with corticospinal tract injury: anti-apoptosis mechanism

Studies have shown that exercise interventions can improve functional recovery after spinal cord injury, but the mechanism of action remains unclear. To investigate the mechanism, we established a unilateral corticospinal tract injury model in rats by pyramidotomy, and used a single pellet reaching task and horizontal ladder walking task as exercise interventions postoperatively. Functional recovery of forelimbs and forepaws in the rat models was noticeably enhanced after the exercises. Furthermore, TUNEL staining revealed significantly fewer apoptotic cells in the spinal cord of exercised rats, and western blot analysis showed that spinal cord expression of the apoptosis-related protein caspase-3 was significantly lower, and the expression of Bcl-2 was significantly higher, while the expression of Bax was not signifiantly changed after exercise, compared with the non-exercised group. Expression of these proteins decreased with time after injury, towards the levels observed in sham-operated rats, however at 4 weeks postoperatively, caspase-3 expression remained significantly greater than in sham-operated rats. The present findings indicate that a reduction in apoptosis is one of the mechanisms underlying the improvement of functional recovery by exercise interventions after corticospinal tract injury.

Click-crosslinked injectable hyaluronic acid hydrogel is safe and biocompatible in the intrathecal space for ultimate use in regenerative strategies of the injured spinal cord

Traumatic spinal cord injury (SCI) causes damage and degeneration at and around the lesion site resulting in a loss of function. SCI presents a complex regenerative problem due to the multiple aspects of growth inhibition and the heterogeneity in size, shape and extent of injury. Currently, there is no widely accepted treatment strategy available and delivering biomolecules to the central nervous system remains a challenge. With a view towards achieving local release, we designed a hydrogel that can be injected into the intrathecal space. Here we describe the synthesis and characterization of a click-crosslinked hyaluronic acid hydrogel and demonstrate controlled in vitro release of bioactive brain derived neurotrophic factor. Importantly, we demonstrate that this new hydrogel is both biocompatible in the intrathecal space based on immunohistochemistry of the host tissue response and safe based on behavioral analysis of locomotor function.