Neuroprotective effects of a novel NMDA antagonist, Gacyclidine, after experimental contusive spinal cord injury in adult rats

Effects of combined treatment of minocycline and methylprednisolone on the expression of tumor necrosis factor alpha and interleukine-6 in experimental spinal cord injury: a light and electron microscopic study

Spinal cord injury (SCI) is an important health problem, and there is no universal treatment protocol for it today. Following SCI pro-inflammatory mediators such as tumor necrosis factor- alpha (TNF-α) and interleukin-6 (IL-6) increase at the lesion site and play important roles in secondary tissue damage. Methylprednisolone (MP) is a glucocorticoid, and minocycline is a tetracycline-derived antibiotic both with neuroprotective effects on central nervous system trauma. However, there are limited studies on their effects on SCI. In this study, we aimed to evaluate effects of MP+minocycline combined treatment on cellular distribution and localization of TNF-α And IL-6 after SCI. Eighty Wistar rats were divided into three main groups as the intact control group, sham operation group, and experimental control group that received spinal cord compression injury. Following the injury, the experimental control group was subdivided into four groups as control, methylprednisolone treatment, minocycline treatment and, MP+minocycline combined treatment groups. Tissue samples were obtained from all groups at 24 hours and 72 hours after the injury. We found a significant decrease in TNF-α And IL-6 expressions in combined treatment group at 24 hours after injury. Also, there was a significant decrease in MDA and increase in SOD levels in this group. Furthermore, decreased lipid peroxidation and neuronal and glial cell death were also observed in combined treatment group. These results suggest that MP+minocycline combined treatment promotes functional recovery and, it should be considered as an effective treatment protocol following SCI.

A Review on the Etiology and Management of Pediatric Traumatic Spinal Cord Injuries

CONTEXT

Pediatric traumatic spinal cord injury (SCI) is an uncommon presentation in the emergency department. Severe injuries are associated with devastating outcomes and complications, resulting in high costs to both the society and the economic system.

EVIDENCE ACQUISITION

The data on pediatric traumatic spinal cord injuries has been narratively reviewed.

RESULTS

Pediatric SCI is a life-threatening emergency leading to serious outcomes and high mortality in children if not managed promptly. Pediatric SCI can impose many challenges to neurosurgeons and caregivers because of the lack of large studies with high evidence level and specific guidelines in terms of diagnosis, initial management and of in-hospital treatment options. Several novel potential treatment options for SCI have been developed and are currently under investigation. However, research studies into this field have been limited by the ethical and methodological challenges.

CONCLUSION

Future research is needed to investigate the safety and efficacy of the recent uprising neurodegenerative techniques in SCI population. Owing to the current limitations, there is a need to develop novel trial methodologies that can overcome the current methodological and ethical limitations.

Spinal cord injury: pathophysiology, treatment strategies, associated challenges, and future implications

Axonal regeneration and formation of tripartite (axo-glial) junctions at damaged sites is a prerequisite for early repair of injured spinal cord. Transplantation of stem cells at such sites of damage which can generate both neuronal and glial population has gained impact in terms of recuperation upon infliction with spinal cord injury. In spite of the fact that a copious number of pre-clinical studies using different stem/progenitor cells have shown promising results at acute and subacute stages, at the chronic stages of injury their recovery rates have shown a drastic decline. Therefore, developing novel therapeutic strategies are the need of the hour in order to assuage secondary morbidity and effectuate improvement of the spinal cord injury (SCI)-afflicted patients' quality of life. The present review aims at providing an overview of the current treatment strategies and also gives an insight into the potential cell-based therapies for the treatment of SCI.

Clinical Trials in Traumatic Spinal Cord Injury

Traumatic spinal cord injury (SCI) results in impaired neurologic function that for many individuals is permanent and significantly impacts health, function, quality of life, and life expectancy. Many efforts have been taken to develop effective treatments for SCI; nevertheless, proven therapies targeting neurologic regeneration and functional recovery have been limited. Existing therapeutic approaches, including early surgery, strict blood pressure control, and consideration of treatment with steroids, remain debated and largely focus on mitigating secondary injury after the primary trauma has occurred. Today, there is more research being performed in SCI than ever before. Current clinical trials are exploring pharmacologic, cell-based, physiologic, and rehabilitation approaches to reduce secondary injury and also overcome barriers to neurorecovery. In the future, it is likely that tailored treatments combining many of these strategies will offer significant benefits for persons with SCI. This article aims to review key past, current and emerging neurologic and rehabilitation therapeutic approaches for adults with traumatic SCI.

Pharmacological, Cell, and Gene Therapy Strategies to Promote Spinal Cord Regeneration

In this review, recent studies using pharmacological treatment, cell transplantation, and gene therapy to promote regeneration of the injured spinal cord in animal models will be summarized. Pharmacological and cell transplantation treatments generally revealed some degree of effect on the regeneration of the injured ascending and descending tracts, but further improvements to achieve a more significant functional recovery are necessary. The use of gene therapy to promote repair of the injured nervous system is a relatively new concept. It is based on the development of methods for delivering therapeutic genes to neurons, glia cells, or nonneural cells. Direct in vivo gene transfer or gene transfer in combination with (neuro)transplantation (ex vivo gene transfer) appeared powerful strategies to promote neuronal survival and axonal regrowth following traumatic injury to the central nervous system. Recent advances in understanding the cellular and molecular mechanisms that govern neuronal survival and neurite outgrowth have enabled the design of experiments aimed at viral vector-mediated transfer of genes encoding neurotrophic factors, growth-associated proteins, cell adhesion molecules, and antiapoptotic genes. Central to the success of these approaches was the development of efficient, nontoxic vectors for gene delivery and the acquirement of the appropriate (genetically modified) cells for neurotransplantation. Direct gene transfer in the nervous system was first achieved with herpes viral and E1-deleted adenoviral vectors. Both vector systems are problematic in that these vectors elicit immunogenic and cytotoxic responses. Adeno-associated viral vectors and lentiviral vectors constitute improved gene delivery systems and are beginning to be applied in neuroregeneration research of the spinal cord. Ex vivo approaches were initially based on the implantation of genetically modified fibroblasts. More recently, transduced Schwann cells, genetically modified pieces of peripheral nerve, and olfactory ensheathing glia have been used as implants into the injured spinal cord.

Localized delivery of methylprednisolone sodium succinate with polymeric nanoparticles in experimental injured spinal cord model

With important social and economic consequences, spinal cord injuries (SCIs) still exist among major health problems. Although many therapeutic agents and methods investigated for the treatment of acute SCI, only high dose methylprednisolone (MP) is being used currently in practice. Due to the serious side effects, high dose systemic MP administration after SCI is a critical issue that is mostly considered controversial. In our study, it is aimed to develop a nanoparticle-gel combined drug delivery system for localization of MP on trauma site and eliminating dose-dependent side effects by lowering the administered dose. For this purpose, methyl prednisolone sodium succinate (MPSS) loaded polycaprolactone based nanoparticles were developed and embedded in an implantable fibrin gel. The effects of MPSS delivery system are evaluated on an acute SCI rat model, by quantification the levels of three inflammatory cytokines (interleukin-1β, interleukin-6 and caspase-3) and assessment of the damage on ultrastructural level by transmission electron microscopy. Developed NP-gel system showed very similar results with systemic high dose of MPSS. It is believed that developed system may be used as a tool for the safe and effective localized delivery of several other therapeutic molecules on injured spinal cord cases.

Altered mental status and end organ damage associated with the use of gacyclidine: a case series

INTRODUCTION

Over the past decade, there has been a sharp increase in the number of newly identified synthetic drugs. These new drugs are often derivatives of previously abused substances but have unpredictable toxicity. One of these drugs is gacyclidine, a derivative of phencyclidine (PCP). Gacyclidine has been studied as a neuroprotective agent in trauma and as a therapy of soman toxicity. There are no previous reports of its use as a drug of abuse.

CASE REPORTS

During a two-month period in the summer of 2013, a series of patients with severe agitation and end-organ injury were identified in an urban academic Emergency Department (ED). A urine drug of abuse screen was performed on all patients, and serum samples were sent for comprehensive toxicology analysis. A total of five patients were identified as having agitation, rhabdomyolysis, and elevated troponin (Table 1). Three of the five patients reported use of methamphetamine, and all five patients had urine drug screens positive for amphetamine. Comprehensive serum analysis identified methamphetamine in three cases, cocaine metabolites in one case, and a potential untargeted match for gacyclidine in all five cases. No other drugs of abuse were identified.

DISCUSSION

This is the first series of cases describing possible gacyclidine intoxication. The possible source of the gacyclidine is unknown but it may have been an adulterant in methamphetamine as all patients who were questioned reported methamphetamine use. These cases highlight the importance of screening for new drugs of abuse when patients present with atypical or severe symptoms. Gacyclidine has the potential to become a drug of abuse both by itself and in conjunction with other agents and toxicity from gacyclidine can be severe. It is the role of the medical toxicology field to identify new agents such as gacyclidine early and to attempt to educate the community on the dangers of these new drugs of abuse.

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

Spinal cord injury (SCI) leads to social and psychological problems in patients and requires costly treatment and care. In recent years, various pharmacological agents have been tested for acute SCI. Large scale, prospective, randomized, controlled clinical trials have failed to demonstrate marked neurological benefit in contrast to their success in the laboratory. Today, the most important problem is ineffectiveness of nonsurgical treatment choices in human SCI that showed neuroprotective effects in animal studies. Recently, attempted cellular therapy and transplantations are promising. A better understanding of the pathophysiology of SCI started in the early 1980s. Research had been looking at neuroprotection in the 1980s and the first half of 1990s and regeneration studies started in the second half of the 1990s. A number of studies on surgical timing suggest that early surgical intervention is safe and feasible, can improve clinical and neurological outcomes and reduce health care costs, and minimize the secondary damage caused by compression of the spinal cord after trauma. This article reviews current evidence for early surgical decompression and nonsurgical treatment options, including pharmacological and cellular therapy, as the treatment choices for SCI.

Sex differences in mitochondrial (dys)function: Implications for neuroprotection

Decades of research have revealed numerous differences in brain structure size, connectivity and metabolism between males and females. Sex differences in neurobehavioral and cognitive function after various forms of central nervous system (CNS) injury are observed in clinical practice and animal research studies. Sources of sex differences include early life exposure to gonadal hormones, chromosome compliment and adult hormonal modulation. It is becoming increasingly apparent that mitochondrial metabolism and cell death signaling are also sexually dimorphic. Mitochondrial metabolic dysfunction is a common feature of CNS injury. Evidence suggests males predominantly utilize proteins while females predominantly use lipids as a fuel source within mitochondria and that these differences may significantly affect cellular survival following injury. These fundamental biochemical differences have a profound impact on energy production and many cellular processes in health and disease. This review will focus on the accumulated evidence revealing sex differences in mitochondrial function and cellular signaling pathways in the context of CNS injury mechanisms and the potential implications for neuroprotective therapy development.

Spinal NMDA receptor activation constrains inactivity-induced phrenic motor facilitation in Charles River Sprague-Dawley rats

Reduced spinal synaptic inputs to phrenic motor neurons elicit a unique form of spinal plasticity known as inactivity-induced phrenic motor facilitation (iPMF). iPMF requires tumor necrosis factor-α (TNF-α) and atypical protein kinase C (aPKC) activity within spinal segments containing the phrenic motor nucleus to stabilize early, transient increases in phrenic burst amplitude into long-lasting iPMF. Here we tested the hypothesis that spinal N-methyl-d-aspartate receptor (NMDAR) activation constrains long-lasting iPMF in some rat substrains. Phrenic motor output was recorded in anesthetized, ventilated Harlan (HSD) and Charles River (CRSD) Sprague-Dawley rats exposed to a 30-min central neural apnea. HSD rats expressed a robust, long-lasting (>60 min) increase in phrenic burst amplitude (i.e., long-lasting iPMF) when respiratory neural activity was restored. By contrast, CRSD rats expressed an attenuated, transient (∼15 min) iPMF. Spinal NMDAR inhibition with DL-2-amino-5-phosphonopentanoic acid (APV) before neural apnea or shortly (4 min) prior to the resumption of respiratory neural activity revealed long-lasting iPMF in CRSD rats that was phenotypically similar to that in HSD rats. By contrast, APV did not alter iPMF expression in HSD rats. Spinal TNF-α or aPKC inhibition impaired long-lasting iPMF enabled by NMDAR inhibition in CRSD rats, suggesting that similar mechanisms give rise to long-lasting iPMF in CRSD rats with NMDAR inhibition as those giving rise to long-lasting iPMF in HSD rats. These results suggest that NMDAR activation can impose constraints on TNF-α-induced aPKC activation after neural apnea, impairing stabilization of transient iPMF into long-lasting iPMF. These data may have important implications for understanding differential responses to reduced respiratory neural activity in a heterogeneous human population.

Overexpression of the astrocyte glutamate transporter GLT1 exacerbates phrenic motor neuron degeneration, diaphragm compromise, and forelimb motor dysfunction following cervical contusion spinal cord injury

A major portion of spinal cord injury (SCI) cases affect midcervical levels, the location of the phrenic motor neuron (PhMN) pool that innervates the diaphragm. While initial trauma is uncontrollable, a valuable opportunity exists in the hours to days following SCI for preventing PhMN loss and consequent respiratory dysfunction that occurs during secondary degeneration. One of the primary causes of secondary injury is excitotoxic cell death due to dysregulation of extracellular glutamate homeostasis. GLT1, mainly expressed by astrocytes, is responsible for the vast majority of functional uptake of extracellular glutamate in the CNS, particularly in spinal cord. We found that, in bacterial artificial chromosome-GLT1-enhanced green fluorescent protein reporter mice following unilateral midcervical (C4) contusion SCI, numbers of GLT1-expressing astrocytes in ventral horn and total intraspinal GLT1 protein expression were reduced soon after injury and the decrease persisted for ≥6 weeks. We used intraspinal delivery of adeno-associated virus type 8 (AAV8)-Gfa2 vector to rat cervical spinal cord ventral horn for targeting focal astrocyte GLT1 overexpression in areas of PhMN loss. Intraspinal delivery of AAV8-Gfa2-GLT1 resulted in transduction primarily of GFAP(+) astrocytes that persisted for ≥6 weeks postinjury, as well as increased intraspinal GLT1 protein expression. Surprisingly, we found that astrocyte-targeted GLT1 overexpression increased lesion size, PhMN loss, phrenic nerve axonal degeneration, and diaphragm neuromuscular junction denervation, and resulted in reduced functional diaphragm innervation as assessed by phrenic nerve-diaphragm compound muscle action potential recordings. These results demonstrate that GLT1 overexpression via intraspinal AAV-Gfa2-GLT1 delivery exacerbates neuronal damage and increases respiratory impairment following cervical SCI.

Gacyclidine improves the survival and reduces motor deficits in a mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder typified by a massive loss of motor neurons with few therapeutic options. The exact cause of neuronal degeneration is unknown but it is now admitted that ALS is a multifactorial disease with several mechanisms involved including glutamate excitotoxicity. More specifically, N-methyl-D-aspartate (NMDA)-mediated cell death and impairment of the glutamate-transport has been suggested to play a key role in ALS pathophysiology. Thus, evaluating NMDAR antagonists is of high therapeutic interest. Gacyclidine, also named GK11, is a high affinity non-competitive NMDAR antagonist that may protect against motor neuron death in an ALS context. Moreover, GK11 presents a low intrinsic neurotoxicity and has already been used in two clinical trials for CNS lesions. In the present study, we investigated the influence of chronic administration of two doses of GK11 (0.1 and 1 mg/kg) on the survival and the functional motor activity of hSOD1(G93A) mice, an animal model of ALS. Treatment started at early symptomatic age (60 days) and was applied bi-weekly until the end stage of the disease. We first confirmed that functional alteration of locomotor activity was evident in the hSOD1(G93A) transgenic female mice by 60 days of age. A low dose of GK11 improved the survival of the mice by 4.3% and partially preserved body weight. Improved life span was associated with a delay in locomotor function impairment. Conversely, the high dose treatment worsened motor functions. These findings suggest that chronic administration of GK11 beginning at early symptomatic stage may be beneficial for patients with ALS.

From basics to clinical: a comprehensive review on spinal cord injury

Spinal cord injury (SCI) is a devastating neurological disorder that affects thousands of individuals each year. Over the past decades an enormous progress has been made in our understanding of the molecular and cellular events generated by SCI, providing insights into crucial mechanisms that contribute to tissue damage and regenerative failure of injured neurons. Current treatment options for SCI include the use of high dose methylprednisolone, surgical interventions to stabilize and decompress the spinal cord, and rehabilitative care. Nonetheless, SCI is still a harmful condition for which there is yet no cure. Cellular, molecular, rehabilitative training and combinatorial therapies have shown promising results in animal models. Nevertheless, work remains to be done to ascertain whether any of these therapies can safely improve patient's condition after human SCI. This review provides an extensive overview of SCI research, as well as its clinical component. It starts covering areas from physiology and anatomy of the spinal cord, neuropathology of the SCI, current clinical options, neuronal plasticity after SCI, animal models and techniques to assess recovery, focusing the subsequent discussion on a variety of promising neuroprotective, cell-based and combinatorial therapeutic approaches that have recently moved, or are close, to clinical testing.

Spinal cord injury: a review of current therapy, future treatments, and basic science frontiers

The incidence of acute and chronic spinal cord injury (SCI) in the United States is more than 10,000 per year, resulting in 720 cases per million persons enduring permanent disability each year. The economic impact of SCI is estimated to be more than 4 billion dollars annually. Preclinical studies, case reports, and small clinical trials suggest that early treatment may improve neurological recovery. To date, no proven therapeutic modality exists that has demonstrated a positive effect on neurological outcome. Emerging data from recent preclinical and clinical studies offer hope for this devastating condition. This review gives an overview of current basic research and clinical studies for the treatment of SCI.

Neuroprotective effects of racemic ketamine and (S)-ketamine on spinal cord injury in rat

BACKGROUND

The aim of this study was to investigate and to compare the potential neuroprotective effects of racemic ketamine, (S)-ketamine and methylprednisolone after an experimental spinal cord injury model in rats.

METHODS

Fifty-nine Wistar albino rats were divided into three main groups as acute stage (A), subacute stage (SA) and sham groups and then acute and subacute stage groups were divided into four groups regarding the used drug as control (CONT), racemic ketamine (RK), (S)-ketamine (SK) and methylprednisolone (MP) groups. A dorsal laminectomy was performed; and spinal cord injury was induced by using a temporary aneurysm clip. Four hours later from the clip compression, except those of the sham and control groups, the drugs (60 mg/kg racemic ketamine, 60 mg/kg (S)-ketamine or 30 mg/kg methylprednisolone) were administered intraperitoneally. At 72th h and 7th days of the study, the spinal cords of rats were removed from T8 level to the conus medullaris level. The specimens were and evaluated histopathologically, tissue lipid peroxidation (LPO) and myeloperoxidation (MPO) levels were measured and biochemically.

RESULTS

The histopathological results were similar both in the acute and in the subacute stage groups. There was a statistically significant difference among all groups regarding the tissue LPO levels (p<0.001). There was a statistically significant difference between the CONT-A group and the MP-A, RK-A and SK-A groups (p=0.004, p<0.001 and p=0.007, respectively) in acute stage and between the CONT-SA group and SK-SA group (p=0.002) in subacute stage. There was a statistically significant difference among all groups regarding the tissue MPO levels (p=0.001). The median MPO levels were similar among acute stage groups (p=0.057), but there was a statistical difference among subacute stage groups (p=0.046).

CONCLUSION

(S)-ketamine is more effective than methylprednisolone and racemic ketamine to reduce the LPO levels in subacute stage of spinal cord injury in rats. And, it is as effective as methylprednisolone in preventing secondary spinal cord injury histopathologically.

Spinal cord injury clinical trials translational process, review of past and proposed acute trials with reference to recommended trial guidelines

Within the past few years there has been increasing interest in the translation of experimental therapeutic interventions to improve functional outcomes after spinal cord injury (SCI). The number of reported successes using preclinical animal models has been substantial and this has encouraged the development of several clinical trial programs. We will briefly discuss a desired process for the translation of preclinical therapeutic discoveries, as well as the design and conduct of valid human SCI studies. Past SCI trials are examined and current ongoing human studies are outlined. We identify some of the confounding factors that can influence the accurate interpretation of study outcomes. The discussion here will be restricted to treatment strategies that involve drug administration and cell transplants, not that these are currently the most beneficial treatments, but cell transplants are already being offered to patients without completing a valid clinical trial program.

Reduction in expression of the astrocyte glutamate transporter, GLT1, worsens functional and histological outcomes following traumatic spinal cord injury

The astrocyte glutamate transporter, GLT1, is responsible for the vast majority of glutamate uptake in the adult central nervous system (CNS), thereby regulating extracellular glutamate homeostasis and preventing excitotoxicity. Glutamate dysregulation plays a central role in outcome following traumatic spinal cord injury (SCI). To determine the role of GLT1 in secondary cell loss following SCI, mice heterozygous for the GLT1 astrocyte glutamate transporter (GLT1+/-) and wild-type mice received thoracic crush SCI. Compared with wild-type controls, GLT1+/- mice had an attenuated recovery in hindlimb motor function, increased lesion size, and decreased tissue sparing. GLT1+/- mice showed a decrease in intraspinal GLT1 protein and functional glutamate uptake compared with wild-type mice, accompanied by increased apoptosis and neuronal loss following crush injury. These results suggest that astrocyte GLT1 plays a role in limiting secondary cell death following SCI, and also show that compromise of key astrocyte functions has significant effects on outcome following traumatic CNS injury. These findings also suggest that increasing intraspinal GLT1 expression may represent a therapeutically relevant target for SCI treatment.

MK801 attenuates secondary injury in a mouse experimental compression model of spinal cord trauma

BACKGROUND

Glutamergic excitotoxicity has been shown to play a deleterious role in the pathophysiology of spinal cord injury (SCI). The aim of this study was to investigate the neuroprotective effect of dizocilpine maleate, MK801 (2 mg/Kg, 30 min and 6 hours after injury) in a mice model of SCI. The spinal cord trauma was induced by the application of vascular clips to the dura via a four-level T5-T8 laminectomy.

RESULTS

Spinal cord injury in mice resulted in severe trauma characterized by edema, neutrophil infiltration and apoptosis. In this study we clearly demonstrated that administration of MK801 attenuated all inflammatory parameters. In fact 24 hours after injury, the degree of spinal cord inflammation and tissue injury (evaluated as histological score), infiltration of neutrophils, NF-κB activation, iNOS, cytokines levels (TNF-α and IL-1β), neurotrophin expression were markedly reduced by MK801 treatment. Moreover, in a separate set of experiments, we have demonstrated that MK801 treatment significantly improved the recovery of locomotory function.

CONCLUSIONS

Blockade of NMDA by MK801 lends support to the potential importance of NMDA antagonists as therapeutic agents in the treatment of acute spinal cord injury.

Spatial and temporal changes in promoter activity of the astrocyte glutamate transporter GLT1 following traumatic spinal cord injury

After traumatic spinal cord injury (SCI), there is an opportunity for preserving function by attenuating secondary cell loss. Astrocytes play crucial roles in the adult CNS and are responsible for the vast majority of glutamate buffering, potentially preventing excitotoxic loss of neurons and oligodendrocytes. We examined spatial and temporal changes in gene expression of the major astrocyte glutamate transporter GLT1 following moderate thoracic contusion SCI using transgenic BAC-GLT1-eGFP promoter reporter mice. In dorsal column white matter, total intensity of GLT1-eGFP expression per region was significantly reduced following SCI at both lesion epicenter and at rostral and caudal areas where no tissue loss occurred. This regional decrease in GLT1 expression was due to significant loss of GLT1-eGFP(+) cells, partially accounted for by apoptosis of eGFP(+) /GFAP(+) astrocytes in both white and gray matter. There were also decreased numbers of GLT1-eGFP-expressing cells in multiple gray matter regions following injury; nevertheless, there was sustained or even increased regional GLT1-eGFP expression in gray matter as a result of up-regulation in astrocytes that continued to express GLT1-eGFP. Although there were increased numbers of GFAP(+) cells both at the lesion site and in surrounding intact spinal cord following SCI, the majority of proliferating Ki67(+) /GFAP(+) astrocytes did not express GLT1-eGFP. These findings demonstrate that spatial and temporal alterations in GLT1 expression observed after SCI result from both astrocyte death and gene expression changes in surviving astrocytes. Results also suggest that following SCI a significant portion of astrocytes lacks GLT1 expression, possibly compromising the important role of astrocytes in glutamate homeostasis.

Delayed administration of dapsone protects from tissue damage and improves recovery after spinal cord injury

After spinal cord injury (SCI), a complex cascade of pathophysiological processes increases the primary damage. The inflammatory response plays a key role in this pathology. Recent evidence suggests that myeloperoxidase (MPO), an enzyme produced and released by neutrophils, is of special importance in spreading tissue damage. Dapsone (4,4'-diaminodiphenylsulfone) is an irreversible inhibitor of MPO. Recently, we demonstrated, in a model of brain ischemia/reperfusion, that dapsone has antioxidant, antiinflammatory, and antiapoptotic effects. The effects of dapsone on MPO activity, lipid peroxidation (LP) processes, motor function recovery, and the amount of spared tissue were evaluated in a rat model of SCI. MPO activity had increased 24.5-fold 24 hr after SCI vs. the sham group, and it had diminished by 38% and 19% in the groups treated with dapsone at 3 and 5 hr after SCI, respectively. SCI increased LP by 45%, and this increase was blocked by dapsone. In rats treated with dapsone, a significant motor function recovery (Basso-Beattie-Bresnahan score, BBB) was observed beginning during the first week of evaluation and continuing until the end of the study. Spontaneous recovery 8 weeks after SCI was 9.2 ± 1.12, whereas, in the dapsone-treated groups, it reached 13.6 ± 1.04 and 12.9 ± 1.17. Spared tissue increased by 42% and 33% in the dapsone-treated groups (3 and 5 hr after SCI, respectively) vs. SCI without treatment. Dapsone significantly prevented mortality. The results show that inhibition of MPO by dapsone significantly protected the spinal cord from tissue damage and enhanced motor recovery after SCI.

Emerging repair, regeneration, and translational research advances for spinal cord injury

STUDY DESIGN

Literature review of basic scientific and clinical research in spinal cord injury (SCI).

OBJECTIVE

To provide physicians with an overview of the neurobiologic challenges of SCI, the current status of investigation for novel therapies that have been translated to human clinical trials, and the preclinical, scientific basis for each of these therapies.

SUMMARY OF BACKGROUND DATA

An abundance of recent scientific and clinical research activity has revealed numerous insights into the neurobiology of SCI, and has generated an abundance of potential therapies. An increasing number of such therapies are being translated into human SCI trials. Clinicians who attend to SCI patients are increasingly asked about potential treatments and clinical trials.

METHODS

Published data review of novel treatments that are either currently in human clinical trials for acute SCI or about to initiate clinical evaluation.

RESULTS

A number of treatments have bridged the "translational gap" and are currently either in the midst of human SCI trials, or are about to begin such clinical evaluation. These include minocycline, Cethrin, anti-Nogo antibodies, systemic hypothermia, Riluzole, magnesium chloride in polyethylene glycol, and human embryonic stem cell derived oligodendrocyte progenitors. A systematic review of the preclinical literature on these specific therapies reveals promising results in a variety of different SCI injury models.

CONCLUSION

The SCI community is encouraged by the progression of novel therapies from "bench to bedside" and the initiation of clinical trials for a number of different treatments. The task of clinical evaluation, however, is substantial, and many years will be required before the actual efficacy of the treatments currently in evaluation will be determined.

The use of Organotypic Hippocampal Slice Cultures to Evaluate Protection by Non-competitive NMDA Receptor Antagonists against Excitotoxicity

There is great interest in testing neuroprotectants which inhibit the neurodegeneration that results from excessive activation of N-methyl-D-aspartate (NMDA) receptors. As an alternative to in vivo testing in animal models, we demonstrate here the use of a complex in vitro model to compare the efficacy and toxicity of NMDA receptor inhibitors. Organotypic hippocampal slice cultures were used to compare the effectiveness of the Alzheimer's disease drug, memantine, the Parkinson's disease drug, procyclidine, and the novel neuroprotectant, gacyclidine (GK11), against NMDA-induced toxicity. All three drugs are non-competitive NMDA receptor open-channel blockers that inhibit excitotoxic injury, and their neuroprotective capacities have been extensively investigated in vivo in animal models. They have also been evaluated as potential countermeasure agents against organophosphate poisoning. Quantitative densitometric image analysis of propidium iodide uptake in hippocampal regions CA1, CA3 and DG, showed that, after exposure to 10μM NMDA for 24 hours, GK11 was the most potent of the three drugs, with an IC50 of about 50nM and complete protection at 250nM. When applied at high doses, GK11 was still the more potent neuroprotectant, and also the least cytotoxic. These findings are consistent with those from in vivo tests in rodents. We conclude that the slice culture model provides valuable pre-clinical data, and that applying the model to the screening of neuroprotectants might significantly limit the use of in vivo tests in animals.

Modelo experimental de trauma medular agudo produzido por aparelho estereotáxico modificado

Foram utilizados 55 ratos machos da espécie Rattus novergicus, variedade Wistar, com o objetivo de propor um modelo experimental de trauma medular produzido por aparelho estereotáxico modificado, capaz de reproduzir clinicamente lesões medulares padronizadas. Após realização de laminectomia dorsal de T13, utilizou-se peso compressivo de 50,5g (25 animais - grupo I) ou 70,5g (30 animais - grupo II), durante cinco minutos, comprimindo a medula espinhal. Os animais foram assistidos durante oito dias, por meio de testes comportamentais para avaliar a sensibilidade dolorosa, a capacidade motora, o posicionamento tátil e proprioceptivo e a capacidade de manter-se em plano inclinado. No grupo I, observaram-se déficits neurológicos moderados e transitórios, que variaram entre os animais. No grupo II, foi possível obter um trauma padronizado, caracterizado por paraplegia bilateral e simétrica dos membros posteriores, perda de propriocepção e da sensibilidade dolorosa de todos os animais. A utilização do aparelho estereotáxico desenvolvido permite reproduzir clinicamente trauma medular padronizado em ratos, de maneira simples, econômica e satisfatória, o que poderá proporcionar avanços nas investigações terapêuticas, abrangendo doenças neurodegenerativas, como é o caso do trauma medular agudo.

Early functional outcomes and histological analysis after spinal cord compression injury in rats

Object

Neuroprotective and repair strategies in spinal cord injuries (SCIs) have been so far largely unsuccessful. One of the prerequisites is the use of appropriate preclinical models to decipher pathophysiological mechanisms; another is the identification of optimal time windows for therapeutic interventions. The authors undertook this study to characterize early motor, sensory, autonomic, and histological outcomes after balloon compression of the spinal cord at the T8–9 level in adult rats.

Methods

A total of 91 rats were used in this study. Spinal cord balloon compression was performed at T8–9 in adult rats by inflation of a 2 Fr Fogarty catheter into the epidural space. The authors first characterized early motor, sensory, and autonomic outcomes of 2 volumes of compression (10 and 15 μl) using behavioral tests and then examined histological outcomes in the spinal cord using Luxol fast blue staining. To further substantiate the characterization of the epidural balloon-compression model, they used a noncompetitive N-methyl-d-aspartate antagonist, GK11, and demonstrated the involvement of excitotoxicity in this model.

Results

Proportional and reproducible functional impairment resulted from compression caused by balloon inflation with either 10 or 15 μl of water and corresponded to the extent of the lesion. Indeed, during the early phase following SCI (1 week postinjury), recovery of locomotor function and bladder control correlated with the volume of inflation, whereas outcomes with respect to sensory function and reflexes were independent of compression severity. Treatment with GK11 significantly improved motor function in all groups of rats 1 week after injury and bladder voiding in the 10-μl injured rats compared to the 15-μl injured rats.

Conclusions

The results of this study demonstrate that spinal balloon-compression injury in the rat is a well-characterized, reproducible, and predictable model to analyze early events following SCI.

A remotely controlled model of spinal cord compression injury in mice: toward real-time analysis

OBJECT

To date, there has been no efficient therapeutic approach to spinal cord injuries (SCIs). This may be attributable, at least in part, to difficulties in forming predictive and accurate experimental animal models. The authors' previous studies have identified 2 relevant conditions of such a model. The first condition is the ability to compare data derived from rat models of SCI by developing mouse models of SCI that permit access to a large range of transgenic models. The second condition is that the exploration of the consequences of each mechanism of spinal trauma requires modeling the different etiologic aspects of the injury.

METHODS

To fulfill these 2 conditions a new model of mouse spinal cord compression injury was devised using a thread-driven olive-shaped compressive device. The authors characterized early motor, sensory, and histological outcomes using 3 olive diameters and different compression durations.

RESULTS

A gradual and reproducible functional severity that correlated with lesion extension was demonstrated in 76 mice. To further substantiate the characterization of this model, a noncompetitive N-methyl-d-aspartate antagonist was administered in 30 mice, which demonstrated the involvement of excitotoxicity in this model.

CONCLUSIONS

The study demonstrated that spinal olive-compression injury in the mouse is a reproducible, well-characterized, and predictable model for analyzing early events after SCI. The nonmagnetic and remotely controlled design of this model will allow completion of the lesion while the animal is in the MR imaging apparatus, thus permitting further real-time MR imaging studies that will provide insights into the characterization of early events in the spatial and temporal evolution of SCI. Moreover, this model lays the foundation for future in vivo studies of functional and histological outcomes following SCI in genetically engineered animals.

Protection and repair of the injured spinal cord: a review of completed, ongoing, and planned clinical trials for acute spinal cord injury

Over the past 2 decades, advances in understanding the pathophysiology of spinal cord injury (SCI) have stimulated the recent emergence of several therapeutic strategies that are being examined in Phase I/II clinical trials. Ten randomized controlled trials examining methylprednisolone sodium succinate, tirilizad mesylate, monosialotetrahexosylganglioside, thyrotropin releasing hormone, gacyclidine, naloxone, and nimodipine have been completed. Although the primary outcomes in these trials were laregely negative, a secondary analysis of the North American Spinal Cord Injury Study II demonstrated that when administered within 8 hours of injury, methylprednisolone sodium succinate was associated with modest clinical benefits, which need to be weighed against potential complications. Thyrotropin releasing hormone (Phase II trial) and monosialotetrahexosylganglioside (Phase II and III trials) also showed some promise, but we are unaware of plans for future trials with these agents. These studies have, however, yielded many insights into the conduct of clinical trials for SCI. Several current or planned clinical trials are exploring interventions such as early surgical decompression (Surgical Treatment of Acute Spinal Cord Injury Study) and electrical field stimulation, neuroprotective strategies such as riluzole and minocycline, the inactivation of myelin inhibition by blocking Nogo and Rho, and the transplantation of various cellular substrates into the injured cord. Unfortunately, some experimental and poorly characterized SCI therapies are being offered outside a formal investigational structure, which will yield findings of limited scientific value and risk harm to patients with SCI who are understandably desperate for any intervention that might improve their function. Taken together, recent advances suggest that optimism for patients and clinicians alike is justified, as there is real hope that several safe and effective therapies for SCI may become available over the next decade.

New perspectives for the treatment options in spinal cord injury

Spinal cord injury (SCI) is a serious clinical disorder that leads to lifetime disability for which no suitable therapeutic agents are available so far. Further research is needed to understand the basic mechanisms of spinal cord pathology that results in permanent disability and poses a heavy burden on our society. In the past, a lot of effort was placed on improving functional outcome with the help of various therapeutic agents, however less attention has been paid on the development and propagation of spinal cord pathology over time. Thus, it is still unclear whether improvement of functional outcome is related to spinal cord pathology or vice versa. Few drugs are able to influence functional outcome without having any improvement on cord pathology. Some drugs, however, can lessen cord pathology but fail to influence the functional outcome. The goal of future treatment options for SCI is therefore to find suitable new drugs or a combination of existing drugs and to use various cellular transplants, neurotrophic factors, myelin-inhibiting factors, tissue engineering and nano-drug delivery to improve both the functional and the pathological outcome in the inured patient. This review deals with the key aspects of the latest treatments for SCI and suggests some possible future therapeutic measures to enhance healthcare in clinical situations.

The distribution of tissue damage in the spinal cord is influenced by the contusion velocity

STUDY DESIGN

A rat model of thoracic spinal cord contusion was used to examine the effect of velocity on the primary injury.

OBJECTIVES

The overall objective of this study was to determine the effect of the contusion velocity (slow vs. fast) on damage to the spinal cord immediately following mechanical injury. Secondary objectives were to demarcate between damage in the gray and white matters and to observe damage to the mechanical elements of the neurons (i.e., neurofilaments).

SUMMARY OF BACKGROUND DATA

Although studies have explored the effect of impact velocity on spinal cord damage and functional deficits, no study has addressed regional tissue damage of the primary injury (e.g., between the gray and white matter) as a function of velocity.

METHODS

A modified Spinal Cord Injury Research System generated 1 mm contusions in 24 male, Sprague-Dawley rats (210-320 g) at T10, using slow (3 mm/s) and fast (300 mm/s) velocities. The primary lesion (<2 minutes postinjury) was assessed using hematoxylin and eosin staining for hemorrhage volume and immunostaining for nonphosphorylated heavy neurofilament damage.

RESULTS

The volume of hemorrhage in the white matter was significantly increased following fast impact (fast = 0.61 mm3, slow = 0.24 mm3, P = 0.013) whereas the total hemorrhage volume (fast = 1.51 mm, slow = 1.21 mm, P = 0.22) showed no effect. Complete axonal disruption was evident in the fast injury group around the injury epicenter. A significant increase in nonphosphorylated neurofilament staining (P = 0.013) was observed for fast impacts. Hemorrhage in the gray matter was similar between the slow and fast groups, but an increase in neurofilament dephosphorylation was observed in the gray matter following fast contusion (P = 0.03).

CONCLUSION

We conclude that contusion velocity has an effect on the magnitude of injury within the white matter during spinal cord injury and the amount of neuronal damage in the gray matter. The results of this study demonstrate the importance of including high impact velocity as a variable in models of spinal cord injury.

FK1706, a novel non-immunosuppressant neurophilin ligand, ameliorates motor dysfunction following spinal cord injury through its neuroregenerative action

Injured spinal cord axons fail to regenerate in part due to a lack of trophic support. While various methods for replacing neurotrophins have been pursued, clinical uses of these methods face significant barriers. FK1706, a non-immunosuppressant neurophilin ligand, potentiates nerve growth factor signaling, suggesting therapeutic potential for functional deficits following spinal cord injury. Here, we demonstrate that FK1706 significantly improves behavioral outcomes in animal models of spinal cord hemisection and contusion injuries in rats. Furthermore, we show that FK1706 is effective even if administration is delayed until 1 week after injury, suggesting that FK1706 has a reasonable therapeutic time-window. Morphological analysis of injured axons in the dorsal corticospinal tract showed an increase in the radius and perimeter of stained axons, which were reduced by FK1706 treatment, suggesting that axonal swelling and retraction balls observed in injured spinal cord were improved by the neurotrophic effect of FK1706. Taken together, FK1706 improves both behavioral motor function and the underlying morphological changes, suggesting that FK1706 may have therapeutic potential in meeting the significant unmet needs in spinal cord injury.

Comparison of the pharmacological properties of GK11 and MK801, two NMDA receptor antagonists: towards an explanation for the lack of intrinsic neurotoxicity of GK11

Over-stimulation of NMDA receptors (NMDARs) is involved in many neurodegenerative disorders. Thus, developing safe NMDAR antagonists is of high therapeutic interest. GK11 is a high affinity uncompetitive NMDAR antagonist with low intrinsic neurotoxicity, shown to be promising for treating CNS trauma. In the present study, we investigated the molecular basis of its interaction with NMDARs and compared this with the reference molecule MK801. We show, on primary cultures of hippocampal neurons, that GK11 exhibits neuroprotection properties similar to those of MK801, but in contrast with MK801, GK11 is not toxic to neurons. Using patch-clamp techniques, we also show that on NR1a/NR2B receptors, GK11 totally blocks the NMDA-mediated currents but has a six-fold lower IC(50) than MK801. On NR1a/NR2A receptors, it displays similar affinity but fails to totally prevent the currents. As NR2A is preferentially localized at synapses and NR2B at extrasynaptic sites, we investigated, using calcium imaging and patch-clamp approaches, the effects of GK11 on either synaptic or extrasynaptic NMDA-mediated responses. Here we demonstrate that in contrast with MK801, GK11 better preserve the synaptic NMDA-mediated currents. Our study supports that the selectivity of GK11 for NR2B containing receptors accounts contributes, at least partially, for its safer pharmacological profile.

Management of spinal injury

Spinal injury often affects young adults and results in debilitating neurological status, which in turn places a significant burden on society. This review article describes the current practice and controversies surrounding the management of spinal injury. General principles of pre-hospital management, resuscitation, medical treatment, surgical intervention and future advancement are reviewed.

Delayed intervention with transplants and neurotrophic factors supports recovery of forelimb function after cervical spinal cord injury in adult rats

The adult central nervous system is capable of considerable anatomical reorganization and functional recovery after injury. Functional outcomes, however, vary greatly, depending upon size and location of injury, type and timing of intervention, and type of recovery and plasticity evaluated. The present study was undertaken to assess the recovery of skilled and unskilled forelimb function in adult rats after a C5/C6 spinal cord over-hemisection and delayed intervention with fetal spinal cord transplants and neurotrophins. Recovery of forelimb function was evaluated during both target reaching (a skilled behavior) and vertical exploration (an unskilled behavior). Anatomical tracing and immunohistochemistry were used to assess the growth of descending raphespinal, corticospinal, and rubrospinal fibers at the injury site, tracts that normally confer forelimb function. Delayed intervention with transplants and either brain-derived neurotrophic factor (BDNF) or neurotrophin-3 (NT-3) restored skilled left forelimb reaching to pre-injury levels. Animals showed recovery of normal reaching movements rather than compensation with abnormal movements. Transplants and NT-3 also improved right forelimb use during an unskilled vertical exploration, but not skilled right reaching. Intervention with fetal transplant tissue supported the growth of descending serotonergic, corticospinal, and rubrospinal fibers into the transplant at the lesion site. The addition of neurotrophins, however, did not significantly increase axonal growth at the lesion site. These studies suggest that the recovery of skilled and unskilled forelimb use is possible after a large cervical spinal cord injury following delayed intervention with fetal spinal cord and neurotrophins. Plasticity of both spared and axotomized descending pathways likely contributes to the functional recovery observed.

Pharmacological approaches to repair the injured spinal cord

Acute traumatic spinal cord injury (SCI) results in a devastating loss of neurological function below the level of injury and adversely affects multiple systems within the body. The pathobiology of SCI involves a primary mechanical insult to the spinal cord and activation of a delayed secondary cascade of events, which ultimately causes progressive degeneration of the spinal cord. Whereas cell death from the mechanical injury is predominated by necrosis, secondary injury events trigger a continuum of necrotic and apoptotic cell death mechanisms. These secondary events include vascular abnormalities, ischemia-reperfusion, glutamate excitotoxicity and disturbances in ionic homeostasis, oxidative cell injury, and a robust inflammatory response. No gold standard therapy for SCI has been established, although clinical trials with methylprednisolone (NASCIS II and III) and GM-1 ganglioside (Maryland and Sygen) have demonstrated modest, albeit potentially important therapeutic benefits. In light of the overwhelming impact of SCI on the individual, other therapeutic interventions are urgently needed. A number of promising pharmacological therapies are currently under investigation for neuroprotective abilities in animal models of SCI. These include the sodium (Na+) channel blocker riluzole, the tetracycline derivative minocycline, the fusogen copolymer polyethylene glycol (PEG), and the tissue-protective hormone erythropoietin (EPO). Moreover, clinical trials investigating the putative neuroprotective and neuroregenerative properties ascribed to the Rho pathway antagonist, Cethrin (BioAxone Therapeutic, Inc.), and implantation of activated autologous macrophages (ProCord; Proneuron Biotechnologies) in patients with thoracic and cervical SCI are now underway. We anticipate that these studies will harken an era of renewed interest in translational clinical trials. Ultimately, due to the multi-factorial pathophysiology of traumatic SCI, effective therapies will require combined approaches.

Intrathecal bupivacaine protects against extension of lesions in an acute contusive spinal cord injury model

BACKGROUND AND OBJECTIVE

We recently demonstrated that intrathecal bupivacaine before or after acute photochemical spinal injury improved functional outcome in rats. However, the closest model to spinal trauma is the contusive weight-drop method. The aim of this study was to evaluate functional, electrophysiological and anatomical consequences of a contusive spinal-cord lesion in rats with or without an intrathecal injection of bupivacaine.

METHODS

Fifteen minutes before a contusive spinal lesion, 18 rats received intrathecally either 0.5% bupivacaine (Group T) or saline (Group C). During an 18-days period, motor and sensory functions were evaluated, and bladder voiding dysfunction was noted. Somatosensory evoked potential testings were performed at day 18. Then, the intact spinal cord area at the epicentre of the lesion and the extent of the lesion were measured.

RESULTS

Motor deficit was less and inclined-plane stability was better in treated animals at all times, the scores were statistically different from day 7. There were no differences concerning the sensory test. Despite no significant difference, there were less spinal bladders in the T group from day 7. Somatosensory evoked potential latencies were longer in T group, but only the first negative component (N1) was statistically significant. Amplitudes were higher in T group, but were not statistically different. The spinal cord intact area at the epicentre of the lesion was higher in the T group (1.23 +/- 0.8 mm(2) vs. 0.81 +/- 0.39 mm(2); P < 0.05). The extent of the lesion was higher in the C group (9.4 +/- 2.9 mm vs. 6.4 +/- 3.4 mm; P < 0.05).

CONCLUSION

Intrathecal 0.5% bupivacaine provide a neuroprotective effect by decreasing functional, electrophysiological and anatomical consequences after a contusive spinal cord injury.

Protective effects of extract of Ginkgo biloba (EGb 761) on nerve cells after spinal cord injury in rats

STUDY DESIGN

An experimental animal model was used to assess spinal cord injury following lateral hemitransection at thoracic spinal cord level.

OBJECTIVE

To determine whether extract of Ginkgo biloba (EGb) could have a neuroprotective effect in spinal cord injury (SCI) in rats.

SETTING

Department of Biological Sciences and Biotechnology, Tsinghua University, China.

METHODS

A total of 72 adult rats were divided randomly into three groups: the EGb group, normal saline (NS) group, and sham operation group (sham group). After thoracic spinal cord hemitransection was performed at the level of the 9th thoracic vertebra (T9), rats in the EGb group were given 100 mg/kg EGb 761 daily, while rats in the NS group received NS. The rats in the sham group only underwent laminectomy without spinal cord hemitransection. At various time points after surgery, thoracic spinal cords were sampled and sliced for histochemistry, immunohistochemistry of inducible nitric oxide synthase (iNOS), and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) of apoptotic cells.

RESULTS

Myelin staining showed that the area of cavities was small and the demyelinated zones were limited at and around the injury site of the spinal cord in the EGb group, while the area of cavities was large and the demyelinated zones were serious in the NS group. Nissl staining showed that the ratio of bilateral ventral horn neurons (transection side/uninjured side) in the EGb group was higher than that in the NS group (P<0.05). The apoptotic index and the percentage of iNOS-positive cells were lower in the EGb group than in the NS group. Furthermore, the percentage of iNOS-positive cells positively correlated with the apoptotic index (r( 2)=0.729, P<0.01) after SCI.

CONCLUSION

This study demonstrated that EGb 761 could inhibit iNOS expression and have neuroprotective effect by preventing nerve cells from apoptosis after SCI in rats.

Current status of clinical trials for acute spinal cord injury

Acute spinal cord injury (ASCI) occurs as a result of physical disruption of spinal cord axons through the epicenter of injury leading to deficits in motor, sensory, and autonomic function. This is a debilitating neurological disorder common in young adults that often requires life-long therapy and rehabilitative care, placing a significant burden on our healthcare system. While no cure exists, research has identified various pharmacological compounds that specifically antagonize primary and secondary mechanisms contributing to the etiology of ASCI. Several compounds including methylprednisolone (MPSS), GM-1 ganglio-side, thyrotropin releasing hormone (TRH), nimodipine, and gacyclidine have been tested in prospective randomized clinical trials of ASCI. MPSS and GM-1 ganglioside have shown evidence of modest benefits. Clearly trials of improved neuroprotective agents are required. Promising potential therapies for ASCI include riluzole, minocycline, erythropoietin, and the fusogen polyethylene glycol, as well as mild hypothermia.

An Appraisal of Ongoing Experimental Procedures in Human Spinal Cord Injury

Clinicians and scientists in the field of spinal cord injury research and medicine are poised to begin translating promising new experimental findings into treatments for people. Advances in experimental regeneration research have led to several transplantation strategies that promote axonal regrowth and partial functional recovery in animal models of injury. In this review, we summarize current knowledge regarding various invasive experimental treatments that have been or are now being applied clinically. Various questions about the timeliness, safety, and benefits of the procedures are under discussion within the spinal cord injury (SCI) research community. We also describe guidelines for carrying out optimal clinical trials and efforts to establish specific international guidelines to translate preclinical treatment strategies into clinical trials in SCI. The clinical trial process and the role that clinical professionals have in advising individuals regarding participation in experimental procedures also is discussed.

Glutathione monoethyl ester improves functional recovery, enhances neuron survival, and stabilizes spinal cord blood flow after spinal cord injury in rats

Secondary damage after spinal cord (SC) injury remains without a clinically effective drug treatment. To explore the neuroprotective effects of cell-permeable reduced glutathione monoethyl ester (GSHE), rats subjected to SC contusion using the New York University impactor were randomly assigned to receive intraperitoneally GSHE (total dose of 12 mg/kg), methylprednisolone sodium succinate (total dose of 120 mg/kg), or saline solution as vehicle. Motor function, assessed using the Basso-Beattie-Bresnahan scale for 8 weeks, was significantly better in GSHE (11.2+/-0.6, mean+/-S.E.M., n=8, at 8 weeks) than methylprednisolone (9.3+/-0.6) and vehicle (9.4+/-0.7) groups. The number of neurons in the red nuclei labeled with FluoroRuby placed caudally to the injury site was significantly higher in GSHE (158+/-9.3 mean+/-S.E.M., n=4) compared with methylprednisolone (53+/-14.7) and vehicle (46+/-16.4) groups. Differences in the amount of spared SC tissue at the epicenter and neighboring areas were not significant among experimental groups. In a second series of experiments, using similar treatment groups (n=6), regional changes in microvascular SC blood flow were evaluated for 100 min by laser-Doppler flowmetry after clip compression injury. SC blood flow fell in vehicle-treated rats 20% below baseline and increased significantly with methylprednisolone approximately 12% above baseline; changes were not greater than 5% in rats given GSHE. In conclusion, GSHE given to rats early after moderate SC contusion/compression improves functional outcome and red nuclei neuron survival significantly better than methylprednisolone and vehicle, and stabilizes SC blood flow. These results support further investigation of reduced glutathione supplementation after acute SC injury for future clinical application.

Nuclear magnetic resonance microimaging of mouse spinal cord in vivo

The spinal cord is the site of traumatic injuries, the devastating consequences of which constitute a public health problem in our societies. So far, there is no efficient repair therapeutic approach, and this is mainly due to the great difficulty for elaborating predictive experimental models of this pathology. Up to now, most pathophysiological studies were based on postmortem evaluation of the quantity and extent of the lesions, and their comparison in-between human and rodent specimen. Recent progresses of magnetic resonance imaging provide new tools to examine in vivo rodent central nervous system, and eventually to monitor the progression of lesions. However, up to now, mice spinal cord has been inaccessible to such studies, due to specific physiological characteristics and to the small size of the cord. In this study, the first diffusion-weighted images depicting the mouse thoracic spinal cord in vivo are shown. Motion-related artifacts are significantly reduced by respiratory gating using a dedicated sensor. By changing the direction of diffusion-sensitizing gradients, different contrasts were obtained that are compared with ex vivo MRI and histological preparations. In addition, preliminary results obtained on pathological cords are presented.

Treatment with the neurosteroid dehydroepiandrosterone promotes recovery of motor behavior after moderate contusive spinal cord injury in the mouse

The neurosteroid dehydroepiandrosterone (DHEA) has neuroprotective properties after ischemic and excitatory insults to the brain. In the developing embryo, it is produced in discrete regions of the central nervous system (CNS), where it specifically promotes axonal growth of differentiated neurons. To test if DHEA could be beneficial after spinal cord injury (SCI), we used a model of moderate contusive SCI developed and characterized in the mouse. Immediately after surgery, we applied treatment with DHEA or with vehicle only and compared treatment groups (n = 12 in each group) over a 42-day period. Locomotor recovery was assessed in an open field using a standardized 21-point scale, according to gait analysis on paw print recordings and using foot fault analyses on an inclined ladder beam. The DHEA-treated group showed improved function compared to vehicle-treated animals in these tests. More strikingly, DHEA enhanced recovery of left-right coordination and fine motor control. In an attempt to correlate functional recovery with spinal cord neuropathology in the different experimental groups, we studied the area of spared white matter at the epicenter and reactive gliosis/scar formation 42 days post-injury (DPI). DHEA significantly increased the area of white matter spared at the epicenter and reduced the area of reactive gliosis surrounding the lesion. These data demonstrate the effectiveness of DHEA in promoting functional recovery in the adult murine injured spinal cord.

Excitotoxic and excitoprotective mechanisms: abundant targets for the prevention and treatment of neurodegenerative disorders

Activation of glutamate receptors can trigger the death of neurons and some types of glial cells, particularly when the cells are coincidentally subjected to adverse conditions such as reduced levels of oxygen or glucose, increased levels of oxidative stress, exposure to toxins or other pathogenic agents, or a disease-causing genetic mutation. Such excitotoxic cell death involves excessive calcium influx and release from internal organelles, oxyradical production, and engagement of programmed cell death (apoptosis) cascades. Apoptotic proteins such as p53, Bax, and Par-4 induce mitochondrial membrane permeability changes resulting in the release of cytochrome c and the activation of proteases, such as caspase-3. Events occurring at several subcellular sites, including the plasma membrane, endoplasmic reticulum, mitochondria and nucleus play important roles in excitotoxicity. Excitotoxic cascades are initiated in postsynaptic dendrites and may either cause local degeneration or plasticity of those synapses, or may propagate the signals to the cell body resulting in cell death. Cells possess an array of antiexcitotoxic mechanisms including neurotrophic signaling pathways, intrinsic stress-response pathways, and survival proteins such as protein chaperones, calcium-binding proteins, and inhibitor of apoptosis proteins. Considerable evidence supports roles for excitotoxicity in acute disorders such as epileptic seizures, stroke and traumatic brain and spinal cord injury, as well as in chronic age-related disorders such as Alzheimer's, Parkinson's, and Huntington's disease and amyotrophic lateral sclerosis. A better understanding of the excitotoxic process is not only leading to the development of novel therapeutic approaches for neurodegenerative disorders, but also to unexpected insight into mechanisms of synaptic plasticity.