Increased expression of neurotrophins and their receptors in the mechanically compressed spinal cord of the spinal hyperostotic mouse (twy/twy)

Restoration of spinal cord injury: From endogenous repairing process to cellular therapy

Spinal cord injury (SCI) disrupts neurological pathways and impacts sensory, motor, and autonomic nerve function. There is no effective treatment for SCI currently. Numerous endogenous cells, including astrocytes, macrophages/microglia, and oligodendrocyte, are involved in the histological healing process following SCI. By interfering with cells during the SCI repair process, some advancements in the therapy of SCI have been realized. Nevertheless, the endogenous cell types engaged in SCI repair and the current difficulties these cells confront in the therapy of SCI are poorly defined, and the mechanisms underlying them are little understood. In order to better understand SCI and create new therapeutic strategies and enhance the clinical translation of SCI repair, we have comprehensively listed the endogenous cells involved in SCI repair and summarized the six most common mechanisms involved in SCI repair, including limiting the inflammatory response, protecting the spared spinal cord, enhancing myelination, facilitating neovascularization, producing neurotrophic factors, and differentiating into neural/colloidal cell lines.

Comprehensive analysis of m6A methylation modification in chronic spinal cord injury in mice

Chronic spinal cord injury (CSCI) is a catastrophic disease of the central nervous system (CNS), resulting in partial or complete loss of neurological function. N6-methyladenosine (m6A) is the most common form of reversible posttranslational modification at the RNA level. However, the role of m6A modification in CSCI remains unknown. In this study, we established a CSCI model using a water-absorbable polyurethane polymer, with behavioral assessment, electrophysiological analysis, and histochemical staining for validation. Methylated RNA immunoprecipitation sequencing (meRIP-seq) and messenger RNA sequencing (mRNA-seq) were jointly explored to compare the differences between CSCI spinal tissue and normal spinal tissue. Furthermore, real-time quantitative reverse transcription pcr (qRT-PCR), western blot analysis, and immunofluorescence staining were used to analyze m6A modification-related proteins. We found that water-absorbable polyurethane polymer simulated well chronic spinal cord compression. Basso mouse scale scores and electrophysiological analysis showed continuous neurological function decline after chronic compression of the spinal cord. meRIP-seq identified 642 differentially modified m6A genes, among which 263 genes were downregulated and 379 genes were upregulated. mRNA-seq showed that 1544 genes were upregulated and 290 genes were downregulated after CSCI. Gene Ontology terms and enriched Kyoto Encyclopedia of Genes and Genomes pathways were also identified. qRT-PCR, western blotting, and immunofluorescence staining showed that Mettl14, Ythdf1, and Ythdf3 were significantly upregulated after CSCI. Our study revealed a comprehensive profile of m6A modifications in CSCI which may act as a valuable key for future research on CSCI.

The Pathophysiology of Degenerative Cervical Myelopathy and the Physiology of Recovery Following Decompression

Background: Degenerative cervical myelopathy (DCM), also known as cervical spondylotic myelopathy is the leading cause of spinal cord compression in adults. The mainstay of treatment is surgical decompression, which leads to partial recovery of symptoms, however, long term prognosis of the condition remains poor. Despite advances in treatment methods, the underlying pathobiology is not well-known. A better understanding of the disease is therefore required for the development of treatments to improve outcomes following surgery. Objective: To systematically evaluate the pathophysiology of DCM and the mechanism underlying recovery following decompression. Methods: A total of 13,808 published articles were identified in our systematic search of electronic databases (PUBMED, WEB OF SCIENCE). A total of 51 studies investigating the secondary injury mechanisms of DCM or physiology of recovery in animal models of disease underwent comprehensive review. Results: Forty-seven studies addressed the pathophysiology of DCM. Majority of the studies demonstrated evidence of neuronal loss following spinal cord compression. A number of studies provided further details of structural changes in neurons such as myelin damage and axon degeneration. The mechanisms of injury to cells included direct apoptosis and increased inflammation. Only four papers investigated the pathobiological changes that occur in spinal cords following decompression. One study demonstrated evidence of axonal plasticity following decompressive surgery. Another study demonstrated ischaemic-reperfusion injury following decompression, however this phenomenon was worse when decompression was delayed. Conclusions: In preclinical studies, the pathophysiology of DCM has been poorly studied and a number of questions remain unanswered. The physiological changes seen in the decompressed spinal cord has not been widely investigated and it is paramount that researchers investigate the decompressed spinal cord further to enable the development of therapeutic tools, to enhance recovery following surgery.

BDNF, COMT, and DRD2 polymorphisms and ability to return to work in adult patients with low- and high-grade glioma

BACKGROUND

Cognitive and language dysfunction is common among patients with glioma and has a significant impact on survival and health-related quality of life (HRQOL). Little is known about the factors that make individual patients more or less susceptible to the cognitive sequelae of the disease. A better understanding of the individual and population characteristics related to cognitive function in glioma patients is required to appropriately stratify patients, prognosticate, and develop more efficacious treatment regimens. There is evidence that allelic variation among genes involved in neurotransmission and synaptic plasticity are related to neurocognitive performance in states of health and neurologic disease.

METHODS

We studied the association of single-nucleotide polymorphism variations in brain-derived neurotrophic factor (BDNF, rs6265), dopamine receptor 2 (DRD2, rs1076560), and catechol-O-methyltransferase (COMT, rs4680) with neurocognitive function and ability to return to work in glioma patients at diagnosis and at 3 months. We developed a functional score based on the number of high-performance alleles that correlates with the capacity for patients to return to work.

RESULTS

Patients with higher-performing alleles have better scores on neurocognitive testing with the Repeatable Battery for the Assessment of Neuropsychological Status and Stroop test, but not the Trail Making Test.

CONCLUSIONS

A better understanding of the genetic contributors to neurocognitive performance in glioma patients and capacity for functional recovery is necessary to develop improved treatment strategies based on patient-specific factors.

Genetic factors of cervical spondylotic myelopathy-a systemic review

BACKGROUND

Cervical spondylotic myelopathy (CSM) is a degenerative disorder of the neck. Recent studies have reported the roles of single nucleotide polymorphisms and abnormal gene expression in the etiology and development of CSM. However, a systemic review of these findings is currently unavailable.

METHODS

A systemic review of genetic factors of CSM was conducted through searching PubMed and EMbase databases. A total of 9 studies were included in this study, which included 8 genes: brain derived neurotrophic factor (BDNF), osteopontin (OPN), bone morphogenic protein (BMP) 4, collagen IX, vitamin D receptor (VDR), apolipoprotein E (ApoE), hypoxia-inducible factor α (HIF-1α), and cyclooxygenase 2 (COX-2).

RESULTS

The polymorphisms of 6 genes (OPN, BMP-4, collagen IX, VDR, HIF-1α) showed significant association with the susceptibility to or risk of CSM. The polymorphisms of 3 genes (BMP-4, ApoE4, HIF-1α) were significantly associated with the postoperative outcome. The polymorphism of BDNF, VDR, and expression of COX-2 were associated with the severity of disease.

CONCLUSION

This review demonstrates that 8 genes were associated with CSM although there is no repeated study. This review also suggests that large scale and high quality studies are needed to provide more reliable evidence for future evaluation.

Changes in compressed neurons from dogs with acute and severe cauda equina constrictions following intrathecal injection of brain-derived neurotrophic factor-conjugated polymer nanoparticles

This study established a dog model of acute multiple cauda equina constriction by experimental constriction injury (48 hours) of the lumbosacral central processes in dorsal root ganglia neurons. The repair effect of intrathecal injection of brain-derived neurotrophic factor with 15 mg encapsulated biodegradable poly(lactide-co-glycolide) nanoparticles on this injury was then analyzed. Dorsal root ganglion cells (L₇) of all experimental dogs were analyzed using hematoxylin-eosin staining and immunohistochemistry at 1, 2 and 4 weeks following model induction. Intrathecal injection of brain-derived neurotrophic factor can relieve degeneration and inflammation, and elevate the expression of brain-derived neurotrophic factor in sensory neurons of compressed dorsal root ganglion. Simultaneously, intrathecal injection of brain-derived neurotrophic factor obviously improved neurological function in the dog model of acute multiple cauda equina constriction. Results verified that sustained intraspinal delivery of brain-derived neurotrophic factor encapsulated in biodegradable nanoparticles promoted the repair of histomorphology and function of neurons within the dorsal root ganglia in dogs with acute and severe cauda equina syndrome.

Beneficial Effect of Human Induced Pluripotent Stem Cell-Derived Neural Precursors in Spinal Cord Injury Repair

Despite advances in our understanding and research of induced pluripotent stem cells (iPSCs), their use in clinical practice is still limited due to lack of preclinical experiments. Neural precursors (NPs) derived from a clone of human iPSCs (IMR90) were used to treat a rat spinal cord lesion 1 week after induction. Functional recovery was evaluated using the BBB, beam walking, rotarod, and plantar tests. Lesion morphology, endogenous axonal sprouting, graft survival, and iPSC-NP differentiation were analyzed immunohistochemically. Quantitative polymerase chain reaction (qPCR) was used to evaluate the effect of transplanted iPSC-NPs on endogenous regenerative processes and also to monitor their behavior after transplantation. Human iPSC-NPs robustly survived in the lesion, migrated, and partially filled the lesion cavity during the entire period of observation. Transplanted animals displayed significant motor improvement already from the second week after the transplantation of iPSC-NPs. qPCR revealed the increased expression of human neurotrophins 8 weeks after transplantation. Simultaneously, the white and gray matter were spared in the host tissue. The grafted cells were immunohistochemically positive for doublecortin, MAP2, βIII-tubulin, GFAP, and CNPase 8 weeks after transplantation. Human iPSC-NPs further matured, and 17 weeks after transplantation differentiated toward interneurons, dopaminergic neurons, serotoninergic neurons, and ChAT-positive motoneurons. Human iPSC-NPs possess neurotrophic properties that are associated with significant early functional improvement and the sparing of spinal cord tissue. Their ability to differentiate into tissue-specific neurons leads to the long-term restoration of the lesioned tissue, making the cells a promising candidate for future cell-based therapy of SCI.

The prevalence and phenotype of activated microglia/macrophages within the spinal cord of the hyperostotic mouse (twy/twy) changes in response to chronic progressive spinal cord compression: implications for human cervical compressive myelopathy

Background

Cervical compressive myelopathy, e.g. due to spondylosis or ossification of the posterior longitudinal ligament is a common cause of spinal cord dysfunction. Although human pathological studies have reported neuronal loss and demyelination in the chronically compressed spinal cord, little is known about the mechanisms involved. In particular, the neuroinflammatory processes that are thought to underlie the condition are poorly understood. The present study assessed the localized prevalence of activated M1 and M2 microglia/macrophages in twy/twy mice that develop spontaneous cervical spinal cord compression, as a model of human disease.

Methods

Inflammatory cells and cytokines were assessed in compressed lesions of the spinal cords in 12-, 18- and 24-weeks old twy/twy mice by immunohistochemical, immunoblot and flow cytometric analysis. Computed tomography and standard histology confirmed a progressive spinal cord compression through the spontaneously development of an impinging calcified mass.

Results

The prevalence of CD11b-positive cells, in the compressed spinal cord increased over time with a concurrent decrease in neurons. The CD11b-positive cell population was initially formed of arginase-1- and CD206-positive M2 microglia/macrophages, which later shifted towards iNOS- and CD16/32-positive M1 microglia/macrophages. There was a transient increase in levels of T helper 2 (Th2) cytokines at 18 weeks, whereas levels of Th1 cytokines as well as brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF) and macrophage antigen (Mac) −2 progressively increased.

Conclusions

Spinal cord compression was associated with a temporal M2 microglia/macrophage response, which may act as a possible repair or neuroprotective mechanism. However, the persistence of the neural insult also associated with persistent expression of Th1 cytokines and increased prevalence of activated M1 microglia/macrophages, which may lead to neuronal loss and demyelination despite the presence of neurotrophic factors. This understanding of the aetiopathology of chronic spinal cord compression is of importance in the development of new treatment targets in human disease.

The retrograde delivery of adenovirus vector carrying the gene for brain-derived neurotrophic factor protects neurons and oligodendrocytes from apoptosis in the chronically compressed spinal cord of twy/twy mice

STUDY DESIGN

The twy/twy mouse undergoes spontaneous chronic mechanical compression of the spinal cord; this in vivo model system was used to examine the effects of retrograde adenovirus (adenoviral vector [AdV])-mediated brain-derived neurotrophic factor (BDNF) gene delivery to spinal neural cells.

OBJECTIVE

To investigate the targeting and potential neuroprotective effect of retrograde AdV-mediated BDNF gene transfection in the chronically compressed spinal cord in terms of prevention of apoptosis of neurons and oligodendrocytes.

SUMMARY OF BACKGROUND DATA

Several studies have investigated the neuroprotective effects of neurotrophins, including BDNF, in spinal cord injury. However, no report has described the effects of retrograde neurotrophic factor gene delivery in compressed spinal cords, including gene targeting and the potential to prevent neural cell apoptosis.

METHODS

AdV-BDNF or AdV-LacZ (as a control gene) was injected into the bilateral sternomastoid muscles of 18-week old twy/twy mice for retrograde gene delivery via the spinal accessory motor neurons. Heterozygous Institute of Cancer Research mice (+/twy), which do not undergo spontaneous spinal compression, were used as a control for the effects of such compression on gene delivery. The localization and cell specificity of β-galactosidase expression (produced by LacZ gene transfection) and BDNF expression in the spinal cord were examined by coimmunofluorescence staining for neural cell markers (NeuN, neurons; reactive immunology protein, oligodendrocytes; glial fibrillary acidic protein, astrocytes; OX-42, microglia) 4 weeks after gene injection. The possible neuroprotection afforded by retrograde AdV-BDNF gene delivery versus AdV-LacZ-transfected control mice was assessed by scoring the prevalence of apoptotic cells (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling-positive cells) and immunoreactivity to active caspases -3, -8, and -9, p75, neurofilament 200 kD (NF), and for the oligodendroglial progenitor marker, NG2. RESULTS.: Four weeks after injection, the retrograde delivery of the LacZ marker gene was identified in cervical spinal neurons and some glial cells, including oligodendrocytes in the white matter of the spinal cord, in both the twy/twy mouse and the heterozygous Institute of Cancer Research mouse (+/twy). In the compressed spinal cord of twy/twy mouse, AdV-BDNF gene transfection resulted in a significant decrease in the number of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling-positive cells present in the spinal cord and a downregulation in the caspase apoptotic pathway compared with AdV-LacZ (control) gene transfection. There was a marked and significant increase in the areas of the spinal cord of AdV-BDNF-injected mice that were NF- and NG2-immunopositive compared with AdV-LacZ-injected mice, indicating the increased presence of neurons and oligodendrocytes in response to BDNF transfection.

CONCLUSION

Our results demonstrate that targeted retrograde BDNF gene delivery suppresses apoptosis in neurons and oligodendrocytes in the chronically compressed spinal cord of twy/twy mouse. Further work is required to establish whether this method of gene delivery may provide neuroprotective effects in other situations of compressive spinal cord injury.

Cervical spondylotic myelopathy: the clinical phenomenon and the current pathobiology of an increasingly prevalent and devastating disorder

Cervical spondylotic myelopathy (CSM) is a common disorder involving chronic progressive compression of the cervical spinal cord due to degenerative disc disease, spondylosis, or other degenerative pathology. CSM is the most common form of spinal cord impairment and causes functional decline leading to reduced independence and quality of life. Despite a sound understanding of the disease process, clinical presentation and management, a universal definition of CSM and a standardized index of severity are not currently used universally. Work is required to develop a definition and establish clinical predictors of progression to improve management of CSM. Despite advances in decompressive and reconstructive surgery, patients are often left with residual disability. Gaps in knowledge of the pathobiology of CSM have limited therapeutic advances to complement surgery. Although the histopathologic and pathophysiologic similarities between CSM and traumatic spinal cord injury have long been acknowledged, the unique pathomechanisms of CSM remain unexplored. Increased efforts to elucidate CSM pathobiology could lead to the discovery of novel therapeutic targets for human CSM and other spinal cord diseases. Here, the natural history of CSM, epidemiology, clinical presentation, and current methods of clinical management are reported, along with the current state of basic scientific research in the field.

An in vivo characterization of trophic factor production following neural precursor cell or bone marrow stromal cell transplantation for spinal cord injury

Cellular transplantation strategies for repairing the injured spinal cord have shown consistent benefit in preclinical models, and human clinical trials have begun. Interactions between transplanted cells and host tissue remain poorly understood. Trophic factor secretion is postulated a primary or supplementary mechanism of action for many transplanted cells, however, there is little direct evidence to support trophin production by transplanted cells in situ. In the present study, trophic factor expression was characterized in uninjured, injured-untreated, injured-treated with transplanted cells, and corresponding control tissue from the adult rat spinal cord. Candidate trophic factors were identified in a literature search, and primers were designed for these genes. We examined in vivo trophin expression in 3 paradigms involving transplantation of either brain or spinal cord-derived neural precursor cells (NPCs) or bone marrow stromal cells (BMSCs). Injury without further treatment led to a significant elevation of nerve growth factor (NGF), leukemia inhibitory factor (LIF), insulin-like growth factor-1 (IGF-1), and transforming growth factor-β1 (TGF-β1), and lower expression of vascular endothelial growth factor isoform A (VEGF-A) and platelet-derived growth factor-A (PDGF-A). Transplantation of NPCs led to modest changes in trophin expression, and the co-administration of intrathecal trophins resulted in significant elevation of the neurotrophins, glial-derived neurotrophic factor (GDNF), LIF, and basic fibroblast growth factor (bFGF). BMSCs transplantation upregulated NGF, LIF, and IGF-1. NPCs isolated after transplantation into the injured spinal cord expressed the neurotrophins, ciliary neurotrophic factor (CNTF), epidermal growth factor (EGF), and bFGF at higher levels than host cord. These data show that trophin expression in the spinal cord is influenced by injury and cell transplantation, particularly when combined with intrathecal trophin infusion. Trophins may contribute to the benefits associated with cell-based repair strategies for spinal cord injury.

High-mobility group box-1 and its receptors contribute to proinflammatory response in the acute phase of spinal cord injury in rats

STUDY DESIGN

To examine the localization and expression of high-mobility group box-1 (HMGB-1) protein and its receptors after rat spinal cord injury.

OBJECTIVE

To elucidate the contribution of HMGB-1 and its receptors as potential candidates in a specific upstream pathway to the proinflammatory response leading to a cascade of secondary tissue damage after spinal cord injury.

SUMMARY OF BACKGROUND DATA

HMGB-1 was recently characterized as a key cytokine with a potential role in nucleosome formation and regulation of gene transcription. No studies have investigated the role of HMGB-1 in spinal cord injury.

METHODS

Injured thoracic spinal cord from 62 rats aged 8 to 12 weeks and spinal cord from 20 control rats were examined. HMGB-1 was localized by immunofluorescence staining, costaining with cell markers, and by immunoelectron microscopy. The expression of HMGB-1 and its receptors, receptor for advanced glycation end products (RAGE), toll-like receptor (TLR)2, and TLR4 were also examined by immunohistochemistry.

RESULTS

HMGB-1 expression appeared earlier than that of tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 in the spinal cord injury rats, with the HMGB-1 produced by both macrophages and neurons. HMGB-1 translocated from nucleus to cytoplasm in some neurons at an early stage after neural injury. Increased expression of HMGB-1, RAGE, and TLRs was observed after injury, and interaction of HMGB-1 with RAGE or TLRs, particularly in macrophage, was confirmed at 3 days after injury.

CONCLUSION

Our results demonstrated an earlier onset in the expression of HMGB-1 than in tumor necrosis factor-α, IL-1β, and IL-6 after spinal cord injury. The release of HMGB-1 from neurons and macrophages is mediated through the HMGB-1/RAGE or TLR pathways. HMGB-1 seems to play at least some roles in the proinflammatory cascade originating the secondary damage after the initial spinal cord injury.

Apoptosis of neurons and oligodendrocytes in the spinal cord of spinal hyperostotic mouse (twy/twy): possible pathomechanism of human cervical compressive myelopathy

Introduction

Cervical compressive myelopathy is the most serious complication of cervical spondylosis or ossification of the posterior longitudinal ligament (OPLL) and the most frequent cause of spinal cord dysfunction. There is little information on the exact pathophysiological mechanism responsible for the progressive loss of neural tissue in the spinal cord of such patients. In this study, we used the spinal hyperostotic mouse (twy/twy) as a suitable model of human spondylosis, and OPLL to investigate the cellular and molecular changes in the spinal cord. Mutant twy/twy mouse developed ossification of the ligamentum flavum at C2–C3 and exhibited progressive paralysis.

Materials and methods

The mutant twy/twy mice, aged 16 and 24 weeks, were used in the present study. The cervical spinal cord was analyzed histologically and immunohistochemically.

Results

We observed that a significant correlation between the proportion of apoptotic oligodendrocytes in the compressed area of the spinal cord and the magnitude of cord compression. Immunohistochemical analysis indicated overexpression of TNFR1, CD95, and p75^NTR in the twy/twy mice, which was localized by the immunofluorescence in the neurons and oligodendrocytes.

Conclusion

The expression of such factors seems to play at least some role in the apoptotic process, which probably contributes to axonal degeneration and demyelination in the twy/twy mice spinal cords with severe compression.

Electronic supplementary material

The online version of this article (doi:10.1007/s00586-011-2025-x) contains supplementary material, which is available to authorized users.

Genetic influences on neural plasticity

Neural plasticity refers to the capability of the brain to alter function or structure in response to a range of events and is a crucial component of both functional recovery after injury and skill learning in healthy individuals. A number of factors influence neural plasticity and recovery of function after brain injury. The current review considers the impact of genetic factors. Polymorphisms in the human genes coding for brain-derived neurotrophic factor and apolipoprotein E have been studied in the context of plasticity and stroke recovery and are discussed here in detail. Several processes involved in plasticity and stroke recovery, such as depression or pharmacotherapy effects, are modulated by other genetic polymorphisms and are also discussed. Finally, new genetic polymorphisms that have not been studied in the context of stroke are proposed as new directions for study. A better understanding of genetic influences on recovery and response to therapy might allow improved treatment after a number of forms of central nervous system injury.

Management of cervical spondylotic myelopathy with insights from metabolic imaging of the spinal cord and brain

PURPOSE OF REVIEW

Cervical spondylotic myelopathy (CSM) is a potentially debilitating disorder primarily related to spinal cord injury caused by degenerative changes of the spine. As the population continues to age and live longer, it is likely that this disorder will be encountered with increasing frequency.

RECENT FINDINGS

Surgical management continues to be a mainstay of treatment of CSM patients, but some studies have indicated that nonoperative treatment may be equivalent to surgical management in some patients. Recent advances in neuroimaging of the spinal cord and brain have provided novel information regarding the pathogenesis of CSM, as well as compensatory mechanisms to preserve neurological function.

SUMMARY

CSM is a complex disorder whose incidence is likely to increase in coming years. Prospective, randomized studies are required to help establish the optimal treatment paradigm. Recent advances such as novel neuroimaging techniques and the continued development of neural repair strategies to treat the secondary biological injury associated with this disorder are likely to play key roles in the future management of CSM.

Microarray analysis of expression of cell death-associated genes in rat spinal cord cells exposed to cyclic tensile stresses in vitro

Background

The application of mechanical insults to the spinal cord results in profound cellular and molecular changes, including the induction of neuronal cell death and altered gene expression profiles. Previous studies have described alterations in gene expression following spinal cord injury, but the specificity of this response to mechanical stimuli is difficult to investigate in vivo. Therefore, we have investigated the effect of cyclic tensile stresses on cultured spinal cord cells from E15 Sprague-Dawley rats, using the FX3000^® Flexercell Strain Unit. We examined cell morphology and viability over a 72 hour time course. Microarray analysis of gene expression was performed using the Affymetrix GeneChip System^®, where categorization of identified genes was performed using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) systems. Changes in expression of 12 genes were validated with quantitative real-time reverse transcription polymerase chain reaction (RT-PCR).

Results

The application of cyclic tensile stress reduced the viability of cultured spinal cord cells significantly in a dose- and time-dependent manner. Increasing either the strain or the strain rate independently was associated with significant decreases in spinal cord cell survival. There was no clear evidence of additive effects of strain level with strain rate. GO analysis identified 44 candidate genes which were significantly related to "apoptosis" and 17 genes related to "response to stimulus". KEGG analysis identified changes in the expression levels of 12 genes of the mitogen-activated protein kinase (MAPK) signaling pathway, which were confirmed to be upregulated by RT-PCR analysis.

Conclusions

We have demonstrated that spinal cord cells undergo cell death in response to cyclic tensile stresses, which were dose- and time-dependent. In addition, we have identified the up regulation of various genes, in particular of the MAPK pathway, which may be involved in this cellular response. These data may prove useful, as the accurate knowledge of neuronal gene expression in response to cyclic tensile stress will help in the development of molecular-based therapies for spinal cord injury.

Motor cortex reorganization across the lifespan

The brain is a highly dynamic structure with the capacity for profound structural and functional change. Such neural plasticity has been well characterized within motor cortex and is believed to represent one of the neural mechanisms for acquiring and modifying motor behaviors. A number of behavioral and neural signals have been identified that modulate motor cortex plasticity throughout the lifespan in both the intact and damaged brain. Specific signals discussed in this review include: motor learning in the intact brain, motor relearning in the damaged brain, cortical stimulation, stage of development and genotype. Clinicians are encouraged to harness these signals in the development and implementation of treatment so as to maximally drive neural plasticity and functional improvements in speech, language and swallowing.

LEARNING OUTCOMES

Readers will be able to: (1) describe a set of behavioral and neural signals that modulate motor cortex plasticity in the intact and damaged brain; (2) describe the influence of stage of development on plasticity and functional outcomes; and (3) identify a known genotype that alters the capacity for motor learning and brain plasticity.

Serial changes in bladder, locomotion, and levels of neurotrophic factors in rats with spinal cord contusion

The aims of this study were to evaluate the evolution of the neurogenic bladder after spinal cord contusion and to correlate changes in bladder function with locomotor function and levels of neurotrophic factors. The MASCIS impactor was used to cause a mild contusion injury of the lower thoracic spinal cord of Sprague-Dawley rats. Rats were divided into four groups according to the length of time from injury to sacrifice, at 4, 14, 28, and 56 days after injury. Gait analysis was performed each week, and urodynamic study was performed just before sacrifice. Basso, Beattie, and Bresnahan (BBB) and coupling scores showed gradual recovery, as did the urinary voiding pattern and bladder volume; some parameters of micturition reached normal ranges. Brain-derived neurotrophic factor (BDNF) levels in the spinal cord, as detected by enzyme-linked immunosorbent assay, decreased with time, whereas neurotrophin-3 (NT-3) levels remained unchanged. The micturition pattern, bladder volume, and locomotor function continued to recover during the time of observation; BDNF levels in the spinal cord and bladder were inversely correlated with BBB scores and the restoration of bladder volume. We conclude that urodynamic changes in the bladder correlate with locomotion recovery but not with the levels of BDNF or NT-3 after modified mild contusion injury in rats.

Tumor necrosis factor-alpha and its receptors contribute to apoptosis of oligodendrocytes in the spinal cord of spinal hyperostotic mouse (twy/twy) sustaining chronic mechanical compression

STUDY DESIGN.: To examine the distribution of apoptotic cells and expression of tumor necrosis factor (TNF)-alpha and its receptors in the spinal hyperostotic mouse (twy/twy) with chronic cord compression using immunohistochemical methods. OBJECTIVE.: To study the mechanisms of apoptosis, particularly in oligodendrocytes, which could contribute to degenerative change and demyelination in chronic mechanical cord compression. SUMMARY OF BACKGROUND DATA.: TNF-alpha acts as an external signal initiating apoptosis in neurons and oligodendrocytes after spinal cord injury. Chronic spinal cord compression caused neuronal loss, myelin destruction, and axonal degeneration. However, the biologic mechanisms of apoptosis in chronically compressed spinal cord remain unclear. METHODS.: The cervical spinal cord of 34 twy mice aged 20 to 24 weeks and 11 control animals were examined. The apoptotic cells were detected by the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) staining. The expression and the localization of TNF-alpha, TNF receptor 1 (TNFR1), and TNF receptor 2 (TNFR2) were examined using immunoblot and immnohistochemical analysis. RESULTS.: The number of TUNEL-positive cells in the white matter increased with the severity of compression, which was further increased bilaterally in the white matter of twy/twy mice. Double immunofluorescence staining showed that the number of cells positive for TUNEL and RIP, a marker of oligodendrocytes, increased in the white matter with increased severity of cord compression. Immunoblot analysis demonstrated overexpression of TNF-alpha, TNFR1, and TNFR2 in severe compression. The expression of TNF-alpha appeared in local cells including microglia while that of TNFR1 and TNFR2 was noted in apoptotic oligodendrocytes. CONCLUSION.: Our results suggested that the proportion of apoptotic oligodendrocytes, causing spongy axonal degeneration and demyelination, correlated with the magnitude of cord compression and that overexpression of TNF-alpha, TNFR1, and TNFR2 seems to participate in apoptosis of such cells in the chronically compressed spinal cord.

Brain plasticity and genetic factors

Brain plasticity refers to changes in brain function and structure that arise in a number of contexts. One area in which brain plasticity is of considerable interest is recovery from stroke, both spontaneous and treatment-induced. A number of factors influence these poststroke brain events. The current review considers the impact of genetic factors. Polymorphisms in the human genes coding for brain-derived neurotrophic factor (BDNF) and apolipoprotein E (ApoE) have been studied in the context of plasticity and/or stroke recovery and are discussed here in detail. Several other genetic polymorphisms are indirectly involved in stroke recovery through their modulating influences on processes such as depression and pharmacotherapy effects. Finally, new genetic polymorphisms that have not been studied in the context of stroke are proposed as new directions for study. A better understanding of genetic influences on recovery and response to therapy might allow improved treatment after stroke.

BDNF val66met polymorphism influences motor system function in the human brain

Brain-derived neurotrophic factor (BDNF) is important to brain functions such as plasticity and repair. A single nucleotide polymorphism for this growth factor, val(66)met, is common and associated with decreased activity-dependent BDNF release. The current study evaluated the effects of this polymorphism in relation to human brain motor system function, short-term plasticity, and learning. Functional magnetic resonance imaging (fMRI) scanning during right index finger movement (n = 24) identified activation in a broad sensorimotor network. However, subjects with the polymorphism showed smaller activation volume within several brain regions as compared with subjects without the polymorphism. Repeat fMRI after 25 min of right index finger training found that the 2 genotype groups modulated brain activation differently. In several brain regions, subjects with the polymorphism showed greater activation volume reduction, whereas subjects without the polymorphism showed greater activation volume expansion. On a driving-based motor learning task (independent cohort, n = 29), subjects with the polymorphism showed greater error during short-term learning and poorer retention over 4 days, relative to subjects without the polymorphism. The presence of this BDNF polymorphism is associated with differences in brain motor system function, altered short-term plasticity, and greater error in short-term motor learning. The broader implications of these findings are considered.

Role of Neurotrophin 3 in spinal neuroplasticity in rats subjected to cord transection

That neuroplasticity occurs in mammalian spinal cord is well known, though the underlying mechanism still awaits elucidation. This study evaluated the role of endogenous Neurotrophin-3 (NT-3) in the spinal neuroplasticity. Following cord transection at the junction between T9 and T10, the hindlimb locomotor functions of rats showed gradual but significant improvement from 7 to 28 days post-operation. Corresponding to this was a significant increase in the level of NT-3 in the cord segments caudal to injury site. Significantly, after NT-3-antibody administration, the spinal transected rats displayed poor hindlimb locomotor functions and a decrease in the number of neurons in spinal laminae VIII-IX. Whether NT-3-antibody was administered, corticospinal tract regeneration and somatosensory evoked potentials could not be detected. Our findings suggested that endogenous NT-3 could play an important role in spinal plasticity in adult spinal cords subjected to transection, possibly through a regulation of neuronal activity in the local circuitry.

High-resolution magnetic resonance imaging and 18FDG-PET findings of the cervical spinal cord before and after decompressive surgery in patients with compressive myelopathy

STUDY DESIGN

Evaluation of cervical spinal cord (CSC) of patients with compressive myelopathy by magnetic resonance imaging (MRI) and high-resolution (18F)fluoro-deoxyglucose (18FDG) positron emission tomography (PET).

OBJECTIVE

To determine changes in morphology, intramedullary signal intensity, and glucose metabolic rate in CSC after decompression, and to assess the utility of 18FDG-PET in evaluation of patients with cervical myelopathy.

SUMMARY OF BACKGROUND DATA

The significance of CSC enlargement after decompression and signal intensity changes within the cord remain elusive. No data are available on metabolic activity of the compressed CSC. Only a few studies have examined correlation between high-resolution MRI and 18FDG-PET neuroimaging in cervical myelopathy.

METHODS

We studied 24 patients who underwent cervical decompressive surgery in terms of postoperative neurologic improvement and changes in MRI and 18FDG-PET. Neurologic status was assessed by the Japanese Orthopedic Association scoring system (17-point scale). Signal intensity change in the cord was qualitatively assessed on both T1- and T2-weighted images. The transverse area of the CSC on MRIs and glucose metabolic rate (standardized uptake value [SUV]) from 18FDG-PET were measured digitally.

RESULTS

Neurologic improvement correlated with preoperative CSC transverse area at maximal compression (P < 0.01) and at follow-up (P < 0.001) and with mean SUV before surgery (P < 0.01) and at follow-up (P < 0.05). Preoperative signal intensity change on MRIs (low intramedullary signal intensity abnormality on T1-weighted image and high intramedullary on T2-weighted image) correlated negatively with neurologic improvement rate (P < 0.05). The transverse area of the CSC was significantly smaller after surgery in patients with preoperative MRI signal intensity changes (P < 0.05). The SUV at follow-up tended to normalize in association with neurologic improvement.

CONCLUSION

Our results showed that postoperative neurologic improvement in patients with cervical compressive myelopathy correlated with increased transverse area of the spinal cord, signal intensity change on both T1- and T2-weighted image, and the mean SUV.

Gene expression profiles of neurotrophic factors in rat cultured spinal cord cells under cyclic tensile stress

STUDY DESIGN

An experimental study to investigate the in vitro gene expression of neurotrophic factors and receptors in cultured rat spinal cord cells subjected to cyclic mechanical stretch forces.

OBJECTIVE

We evaluated in vitro expression of neurotrophic factors and receptors in cultured rat spinal cord cells under cyclic tensile stress.

SUMMARY OF BACKGROUND DATA

Application of compressive mechanical stress to the spinal cord results in multiple changes making it difficult to examine the expression of neurotrophic factors and their receptors. There are no in vitro studies that investigated the biologic responses of cultured spinal cord cells to tensile stress.

METHODS

Spinal cord cells were isolated for culture from 15-day Sprague-Dawley rat embryos. We used the FX3000 Flexercell Strain Unit to induce mechanical stress. We analyzed the effects of mechanical stress on cell morphology, mRNA expression levels of various neurotrophic factors, and their immunoreactivities at 0, 2, 6, 12, 24, and 36 hours.

RESULTS

Tensile stress for 6 hours resulted in reduction of spinal cord cells and loss of neurites. Cells that survived 24-hours stress showed swollen irregular-shaped soma, bleb formation, and fragmented neurites. The cell survival rate decreased, whereas lactate dehydrogenase release increased significantly at 6 hours. There were significant increases in mRNA expression levels of nerve growth factor, brain-derived neurotrophic factor, trkB, p75 neurotrophin receptor (p75), glial cell line-derived neurotrophic factor, and caspase-9 during the early period after application of tensile stress.

CONCLUSION

Our results suggest survival of spinal cord neuronal cells under injurious tensile stress with increased synthesis and utilization of several neurotrophic factors, receptors, and expression of proteins related to cell apoptosis.

Rescue of rat anterior horn neurons after spinal cord injury by retrograde transfection of adenovirus vector carrying brain-derived neurotrophic factor gene

We investigated the efficacy of retrograde gene delivery via the sternomastoid muscle of recombinant adenovirus vector (AdV) carrying brain-derived neurotrophic factor (BDNF) gene for the rescue of injured rat spinal cord. One hundred-thirty five adult Sprague-Dawley rats were used in the study with a standard weight-compression technique to produce spinal cord injury. AdV-BDNF gene or AdV-beta-galactosidase (AdV-LacZ) gene was injected into the sternomastoid muscle immediately after traumatic C4 segment spinal cord injury. AdV-BDNF was successfully appeared in the injured cervical spinal cord following injection into the sternomastoid muscle. BDNF expression in the anterior horn neurons of the cervical spinal cord reached peak levels at 1-2 weeks; and the expression persisted at significant levels for approximately 4 weeks after injury. AdV-BDNF transfection was associated with increased numbers of intact neurons as confirmed by Nissl, cholineacetyltransferase (ChAT), and acetylcholine esterase (AChE) staining especially from 2 weeks after injury, compared with the AdV-LacZ injected rats. Our results suggest that in vivo targeted retrograde AdV-BDNF-gene delivery may enhance neuronal survival following traumatic injury of the spinal cord.

Toluene inhalation induced neuronal damage in the spinal cord and changes of neurotrophic factors in rat

We investigated the effects of toluene inhalation on neurons and neurotrophic factors in the spinal cord and the relationship between them. Male Wistar rats were exposed to toluene (1500ppm for 4h per day) for 7 days. To observe damage of the neurons in spinal cord with the toluene, expression of microtubule associated protein 2 (MAP2) and 70kDa heat shock protein (HSP70) in spinal cord were performed by immunohistochemistry. MAP2 was degraded and HSP70-immunoreactivity was enhanced in nerve cell bodies of the gray matter in toluene inhalation group. Immunoreactivity of glial fibrillary acidic protein (GFAP), a marker of astrocytes, was enhanced in the toluene-treated group. Furthermore, glial cell line-derived neurotrophic factor (GDNF)- and brain-derived neurotrophic factor (BDNF)-immunoreactivity in spinal cord were slightly decreased in the treated group. In addition, the concentrations of GDNF and BDNF in the spinal cord were determined using enzyme linked immunosorbent assay (ELISA). Concentration of GDNF was reduced significantly by toluene exposure. BDNF also reduced, but not significantly. The toluene inhalation caused the damage of the neuron in the spinal cord, which was accompanied by the decrease in the neurotrophic factors, such as BDNF and GDNF.

β-Tubulin Is a More Suitable Internal Control thanβ-Actin in Western Blot Analysis of Spinal Cord Tissues after Traumatic Injury

Western blot is a widely used method for determining specific protein levels. To control and correct for loading error, an internal control is often used. To date, two housekeeping geneâcoded proteins (i.e., beta-actin and beta-tubulin) are widely used as internal controls in the Western blot analysis. However, no information is available concerning the stability of their expressions in response to a traumatic injury to the central nervous system (CNS). If so, their use as an internal control may have a negative impact on data acquisition, analysis, and interpretation. Using Western blot analysis, we demonstrated that spinal cord injury (SCI) induced a significant increase in beta-actin expression which peaked at 7 days post-SCI (2.48-fold). Coefficient of variation (CV) analysis showed that the CV of beta-actin expression was 43.79 +/- 4.67%, significantly higher than that of six loadings from a single sample (6.5 +/- 0.9%, p < 0.01), indicating that increased expression of beta-actin was a result of SCI, instead of a loading error. In contrast, no statistically significant difference was found in beta- tubulin expression following SCI, compared with sham-operated controls. The CV of beta-tubulin expression following SCI was 14.3 beta 3.96%, significantly less than that of the beta-actin expression (43.79 +/- 4.67%; p < 0.01). Taken together, our study suggests that beta-actin whose expression increases following SCI is not a suitable internal control for Western blot analysis of spinal cord tissues following a traumatic injury. In contrast, beta-tubulin, whose expression was not significantly affected by SCI, is a better choice for the internal control.

Neuronal loss and expression of neurotrophic factors in a model of rat chronic compressive spinal cord injury

STUDY DESIGN

An experimental animal study about neuronal loss and the expression of neurotrophic factors in the chronic compressive spinal cords.

OBJECTIVES

To investigate neuronal loss and the expression of neurotrophic factors in the chronic compressive spinal cords of rats, and to evaluate effects of decompressive procedures for the neuronal loss.

SUMMARY OF BACKGROUND DATA

Chronic compression of spinal cords induces the loss of motor neurons in the anterior horn. However, the precise mechanism of this neuronal loss is not still understood completely. Furthermore, it is uncertain whether decompressive procedures prevent this neuronal loss or not.

METHODS

A thin expanding polymer sheet was implanted microsurgically underneath T7 laminae of rats. After 6, 9, 12, and 15 weeks, the thoracic spinal cord was harvested and examined histopathologically. The expression of neurotrophic factors, including NGF, BDNF, NT-3, GDNF, CNTF, and VEGF, was analyzed using semiquantitative RT-PCR, enzyme immunoassay, and immunohistochemistry. Decompressive surgery was performed through the removal of T7 laminae and the compression materials 6, 9, and 12 weeks after starting compression. Three weeks later, respectively, the neuronal loss in the anterior horn was estimated.

RESULTS

The spinal cords were progressively flattened by the expanding of the implanted polymer sheet, and the number of motor neurons in the anterior horn decreased, especially from 6 to 9 weeks after starting compression. Semiquantitative RT-PCR analysis showed that the expression of NGF and BDNF mRNAs was decreased significantly in the spinal cords of 12-week compression group compared with the 6-week compression group and that NGF mRNA expression was up-regulated significantly in the 6-week compression group relative to the 6-week control group. Any changes of expression of other neurotrophic factors were not significant. Since BDNF, not NGF, has been known to be one of the powerful survival factors for spinal motoneurons, we investigated the levels of BDNF protein in the compressive spinal cords using enzyme immunoassay and immunohistochemistry. We demonstrated the level of BDNF protein in the compressive spinal cords was increased 6 weeks after compression but declined after 12 weeks. The decompressive procedure in the 6 weeks after compression prevented neuronal loss, but the same procedure in the 9 or 12 weeks was ineffective.

CONCLUSIONS

From the point of view of neuronal loss, decompressive surgery at an earlier stage, when compensatory mechanisms including the up-regulation of BDNF might be still effective, could provide better therapeutic results against chronic mechanical compressive spinal cord lesions.

Targeted retrograde transfection of adenovirus vector carrying brain-derived neurotrophic factor gene prevents loss of mouse (twy/twy) anterior horn neurons in vivo sustaining mechanical compression

STUDY DESIGN

Immunohistochemical analysis after adenovirus (AdV)-mediated BDNF gene transfer in and around the area of mechanical compression in the cervical spinal cord of the hyperostotic mouse (twy/twy).

OBJECTIVE

To investigate the neuroprotective effect of targeted AdV-BDNF gene transfection in the twy mouse with spontaneous chronic compression of the spinal cord motoneurons.

SUMMARY OF BACKGROUND DATA

Several studies reported the neuroprotective effects of neurotrophins on injured spinal cord. However, no report has described the effect of targeted retrograde neurotrophic gene delivery on motoneuron survival in chronic compression lesions of the cervical spinal cord resembling lesions of myelopathy.

METHODS

LacZ marker gene using adenoviral vector (AdV-LacZ) was used to evaluate retrograde delivery from the sternomastoid muscle in adult twy mice (16-week-old) and (control). Four weeks after the AdV-LacZ or AdV-BDNF injection, the compressed cervical spinal cord was removed en bloc for immunohistologic investigation of b-galactosidase activity and immunoreactivity and immunoblot analyses of BDNF. The number of anterior horn neurons was counted using Nissl, ChAT and AChE staining.

RESULTS

Spinal accessory motoneurons between C1 and C3 segments were successfully transfected by AdV-LacZ in both twy and ICR mice after targeted intramuscular injection. Immunoreactivity to BDNF was significantly stronger in AdV-BDNF-gene transfected twy mice than in AdV-LacZ-gene transfected mice. At the cord level showing the maximum compression in AdV-BDNF-transfected twy mice, the number of anterior horn neurons was sinificantly higher in the topographic neuronal cell counting of Nissl-, ChAT-, and AChE-stained samples than in AdV-LacZ-injected twy mice.

CONCLUSION

Targeted AdV-BDNF-gene delivery significantly increased Nissl-stained anterior horn neurons and enhanced cholinergic enzyme activities in the twy. Our results suggest that targeted retrograde AdV-BDNF-gene in vivo delivery may enhance neuronal survival even under chronic mechanical compression.

Cruciate paralysis and hemiplegia cruciata: report of three cases

STUDY DESIGN

Report of three cases of cruciate paralysis and hemiplegia cruciata.

OBJECTIVE

To stress the importance of upper cervical spine lesions causing neurological symptoms and signs.

SETTING

Neuro-orthopedic service, Fukui University Hospital, Japan.

RESULTS

Three patients (all females; one with congenital anomaly at the occiput-atlas level, one with assimilation of the atlas, and one with rheumatoid arthritis-related proliferative synovium) had clinical features of cruciate paralysis and hemiplegia cruciata. All three cases underwent decompressive surgeries.

CONCLUSION

Neurological symptoms and signs of cruciate paralysis and hemiplegia cruciata should be carefully assessed, and surgical therapy should be based on the pathological condition.

Targeted retrograde gene delivery into the injured cervical spinal cord using recombinant adenovirus vector

Direct routes of gene administration (intrathecal, intracerebroventricular or intraparenchymal infusion) have been used for effective and sustained gene delivery, but serious concerns exist about possible traumatic injury as well as neural damage that may lead to further tissue necrosis, apoptosis and cell death. We evaluated targeted retrograde gene delivery through the sternomastoid muscle (innervated by the spinal accessory nerves) into the injured cervical spinal cord using a recombinant adenovirus vector. LacZ gene expression in the cervical spinal cord was noted from 3 days to 4 weeks after the injection of vector into the sternomastoid muscles of the rats. Recombinant adenovirus vector was transferred via a retrograde mechanism into the injured cervical spinal cord with high transduction efficacy (80.6--98.9%) over certain adenoviral titer and dosage. Transduction was less efficient when the vector was injected 1 and 2 weeks after spinal cord injury (44.2--56.8%). Our results indicate retrograde delivery of recombinant adenovirus vector is possible immediately after spinal cord injury, and that this method is promising for gene delivery because it is effective, selective, less invasive to the injured spinal cord, has long-lasting gene expression, and is potentially feasible treatment choice for spinal cord injury.

Metabolic neuroimaging of the cervical spinal cord in patients with compressive myelopathy: a high-resolution positron emission tomography study

OBJECT

The authors conducted a study to examine whether high-resolution [18F]fluorodeoxyglucose (FDG)-positron emission tomography (PET) could be used to visualize deterioration of cervical spinal cord function associated with various degrees of compression and to determine its potential usefulness during assessment of compressive myelopathy.

METHODS

In 23 patients requiring decompressive surgery for myelopathy FDG-PET was performed. The preoperative findings of high-resolution FDG-PET were compared with the neurological scores and magnetic resonance (MR) imaging findings. The preoperative standardized uptake value (SUV) of FDG utilization rate of the cervical cord correlated with the pre- (r = 0.497, p = 0.016) and postoperative neurological scores (r = 0.595, p = 0.003), as well as with the rate of neurological improvement postoperatively (r = 0.538, p = 0.008). The FDG utilization rate did not correlate with the high signal intensity on T2-weighted MR images.

CONCLUSIONS

Analysis of these results indicates that high-resolution FDG-PET imaging provides useful qualitative and quantitative estimates of impaired metabolic activity of the compromised cervical cord that correlate closely with the severity of neurological dysfunction.