Pharmacological approaches to repair the injured spinal cord

Current status of acute spinal cord injury pathophysiology and emerging therapies: promise on the horizon

This review summarizes the current understanding of spinal cord injury pathophysiology and discusses important emerging regenerative approaches that have been translated into clinical trials or have a strong potential to do so. The pathophysiology of spinal cord injury involves a primary mechanical injury that directly disrupts axons, blood vessels, and cell membranes. This primary mechanical injury is followed by a secondary injury phase involving vascular dysfunction, edema, ischemia, excitotoxicity, electrolyte shifts, free radical production, inflammation, and delayed apoptotic cell death. Following injury, the mammalian central nervous system fails to adequately regenerate due to intrinsic inhibitory factors expressed on central myelin and the extracellular matrix of the posttraumatic gliotic scar. Regenerative approaches to block inhibitory signals including Nogo and the Rho-Rho-associated kinase pathways have shown promise and are in early stages of clinical evaluation. Cell-based strategies including using neural stem cells to remyelinate spared axons are an attractive emerging approach.

Magnesium efficacy in a rat spinal cord injury model

Object

Magnesium has been shown to have neuroprotective properties in short-term spinal cord injury (SCI) studies. The authors evaluated the efficacy of magnesium, methylprednisolone, and magnesium plus methylprednisolone in a rat SCI model.

Methods

A moderate-to-severe SCI was produced at T9–10 in rats, which then received saline, magnesium, methylprednisolone, or magnesium plus methylprednisolone within 10 minutes of injury. The Basso-Beattie-Bresnahan (BBB) motor score was evaluated weekly, beginning on postinjury Day 1. After 4 weeks, the rats' spinal cords were evaluated histologically to determine myelin index and gross white matter sparing. A second experiment was conducted to evaluate the effect of delayed administration (8, 12, or 24 hours postinjury) of magnesium on recovery.

Results

The mean BBB scores at 4 weeks showed that rats in which magnesium was administered (BBB Score 6.9 ± 3.9) recovered better than controls (4.2 ± 2.0, p < 0.01). Insufficient numbers of animals receiving methylprednisolone were available for analysis because of severe weight loss. The rats given magnesium within 8 hours of injury had better motor recovery at 4 weeks than control animals (13.8 ± 3.7 vs 8.6 ± 5.1, p < 0.01) or animals in which magnesium was administered at 12 or 24 hours after injury (p < 0.01).

Steroids (30.2%), magnesium (32.3%), and a combination of these (42.3%) had a significant effect on white matter sparing (p < 0.05), but the effect was not synergistic (p > 0.8). Neither steroids nor magnesium had a significant effect on the myelin index (p > 0.1).

Conclusions

The rats receiving magnesium had significantly better BBB motor scores and white matter sparing 4 weeks after moderate-to-severe SCI than control animals. In addition, the groups given steroids only or magnesium and steroids had improved white matter sparing, although the limited numbers of animals reaching the study end point makes it difficult to draw firm conclusions about the utility of steroids in this model. The optimal timing of magnesium administration appears to be within 8 hours of injury.

The efficacy of erythropoietin on acute spinal cord injury. An experimental study on a rat model

INTRODUCTION

The accumulated knowledge of erythropoietin (EPO) interaction in neural injury has led to potentially novel therapeutic strategies. Previous experimental studies of recombinant human EPO (rhEPO) administration have shown favorable results after central and peripheral neural injury. In the present study we used the aneurysmal clip model to evaluate the efficacy of two different regimes of rhEPO administration on the functional outcome after severe acute spinal cord injury (ASCI).

MATERIALS AND METHODS

Thirty rats were operated on with posterior laminectomy at thoracic 10th vertebra. Spinal cord trauma produced by extradural placement of the aneurysm clip, for 1 min. Animals were divided into three groups; the first group received a low total EPO dose (EPO-L), (2 doses of 1,000 IU each s.c.). The second group was administered the high total EPO dose (EPO-H), (14 doses of 1,000 IU each s.c.), and the third was the Control group, which received normal saline in the same time fashion with EPO-H group. Follow-up was for 6 weeks. Estimation of the functional progress of each rat was calculated using the locomotor rating scale of Basso et al, with a range from 0 to 21.

RESULTS

After surgery the animals suffered paraplegia with urinary disturbances. Rats that received EPO demonstrated statistically significant functional improvement compared to the Control group, throughout study interval. On the last follow-up at 6 weeks the EPO-L rats achieved a mean score 17.3 +/- 1.15, the EPO-H 14.7 +/- 1.82, and the control group 8.2 +/- 0.78. Comparison between the two EPO groups reveals superior final outcome of the group treated with lower total dose.

CONCLUSION

Our study supports current knowledge, that EPO administration has a positive effect on functional recovery after experimental ASCI. These data reflect the positive impact of EPO on the pathophysiologic cascade of secondary neural damage. However, we observed a dose-related effect on functional recovery. Interestingly, large doses do not seem to favor the neurological recovery as lower doses do.

Nanoparticle-mediated local delivery of Methylprednisolone after spinal cord injury

Systemic administration of a high-dose of Methylprednisolone (MP) can reduce neurological deficits after acute spinal cord injury (SCI). However, the use of high-dose MP in treating acute SCI is controversial due to significant dose related side effects and relatively modest improvements in neurological function. Here, using a rat model of SCI, we compare the efficacy of controlled, nanoparticle-enabled local delivery of MP to the injured spinal cord with systemic delivery of MP, and a single local injection of MP without nanoparticles. Based on histological and behavioral data, we report that local, sustained delivery of MP via nanoparticles is significantly more effective than systemic delivery. Relative to systemic delivery, MP-nanoparticle therapy significantly reduced lesion volume and improved behavioral outcomes. Nanoparticle-enabled delivery of MP presents an effective method for introducing MP locally after SCI and significantly enhances therapeutic effectiveness compared to bare MP administered either systemically or locally.

Role of extracellular factors in axon regeneration in the CNS: implications for therapy

The glial scar that forms after an injury to the CNS contains molecules that are inhibitory to axon growth. Understanding of the mechanisms of inhibition has allowed the development of therapeutic strategies aimed at promoting axon regeneration. Promising results have been obtained in animal models, and some therapies are undergoing clinical trials. This offers great hope for achievement of functional recovery after CNS injury.

The international standards for neurological classification of spinal cord injury: intra-rater agreement of total motor and sensory scores in the pediatric population

BACKGROUND

The International Standards for Neurological Classification of Spinal Cord Injury (ISCSCI) is the gold standard for evaluating and classifying the neurological consequence of spinal cord injury (SCI).

OBJECTIVE

To determine the within-rater agreement for total scores of light touch (LT), pin prick (PP), and total motor (TM) in children and youth.

DESIGN

Part of a larger cross-sectional study to determine the intra-rater reliability of the standards when applied to children and youth.

PARTICIPANTS/METHODS

A total of 187 subjects participated in 2 repeated examinations performed by the same rater. A total of 7 raters participated in this study. Intraclass correlations coefficients (ICCs), with 95% CI were calculated to determine agreement between the 2 examinations for LT, PP, and TM.

RESULTS

With the exception of subjects younger than 6 years, agreement on repeated total PP, LT, and TM scores were good to excellent, as shown by ICC values of 0.92 or higher. Although agreement was high for the youngest age group for LT (ICC = 0.920), PP (ICC = 0.957), and TM (ICC = 0.971), all of the lower 95% CI values fell well below 0.66, indicating poor precision. All subgroups had good to high agreement for total PP, LT, and TM scores, as indicated by ICC values of 0.87 and higher. There were lower 95% CI (LCI) values for the 6- to 11-year-old group with incomplete paraplegia due to the low number of subjects in that subgroup (N=4). The LCI values were poor for PP for the subgroups with 6- to 11-year-olds with incomplete tetraplegia (LCI = 0.675) and the 12- to 15-year-old group with incomplete paraplegia (LCI = 0.707) and for TM for 16- to 21-year-old group with complete paraplegia (LCI = 0.706).

CONCLUSIONS

In children as young as 6 years, within-rater agreement on LT, PP, and TM exceeded recommended values for clinical measures. With the exception of 6- to 11-year-olds with incomplete injuries, type of injury and severity of injury were not factors in agreement. Although more work is needed to define the lower age limit in which the ISCSCI have utility, these data represent growing evidence supporting the use of the ISCSCI when evaluating the neurological consequence of SCI in children.

Spinal cord injury: epidemiologycal study of 386 cases with emphasis on those patients admitted more than four hours after the trauma

We studied 386 cases of spinal cord injury to analyze the follow up of the patients admitted most of the time more than four hours, the majority of the injuries happening far from the attending health service and first specialized care received long after the accident. This is a clinical study based on data collected during hospitalization of the patients, operated or not, in a Brazilian public health service. The lesion mainly seen was fracture and dislocation, isolated or on multiple levels, and the most important clinical complications were due to respiratory failure and hypotension, especially because 73.8% were from outside and they were admitted more then four hours after the trauma. The mortality rate was 11.9%, but just 2.1% had undergone a surgery. The complications resulted in major risk of death when the trauma was at the cervical level and the patients were over 50 years old, especially when admitted more than four hours after the trauma. We emphasize the importance of the first health care concerning the clinical treatment, aiming to reduce the mortality rate.

GABAA and strychnine-sensitive glycine receptors modulate N-methyl-D-aspartate-evoked acetylcholine release from rat spinal motoneurons: a possible role in neuroprotection

Increasing experimental and clinical evidence suggests that abnormal glutamate transmission might play a major role in a vast number of neurological disorders. As a measure of glutamatergic excitation, we have studied the acetylcholine (ACh) release induced by N-methyl-D-aspartate (NMDA) receptor stimulation in primary cultured rat ventral horn spinal neurons and we have evaluated the possibility to limit the consequences of the hyperactivation of glutamatergic receptors, by recruiting the inhibitory transmission mediated by GABA and glycine. For this purpose, we have exposed cell cultures, previously loaded with [(3)H]choline, to NMDA, which increased the spontaneous tritium efflux in a concentration-dependent manner. Tritium release is dependent upon external Ca(2+), tetrodotoxin, Cd(2+) ions and omega-conotoxin GVIA, but not on omega-conotoxin MVIIC nor nifedipine, suggesting the involvement of N-type voltage-sensitive calcium channels. NMDA-mediated [(3)H]ACh release was completely prevented by MK-801, 5,7-diclorokynurenic acid and ifenprodil, while it was strongly inhibited by a lower external pH, suggesting that the involved NMDA receptors contain NR1 and NR2B subunits. Muscimol inhibited NMDA-evoked [(3)H]ACh release and its effect was antagonized by SR95531 and potentiated by diazepam, indicating the involvement of benzodiazepine-sensitive GABA(A) receptors. Also glycine, via strychnine-sensitive receptors, inhibited the effect of NMDA. It is concluded that glutamate acts on the NMDA receptors situated on spinal motoneurons to evoke ACh release, which can be inhibited through the activation of GABA(A) and glycine receptors present on the same neurons. These data suggest that glutamatergic overload of receptors located onto spinal cord motoneurons might be decreased by activating GABA(A) and glycine receptors.

Ankylosing spondylitis and spinal cord injury: origin, incidence, management, and avoidance

Ankylosing spondylitis (AS) is a chronic inflammatory rheumatic disease that primarily affects the vertebral column and sacroiliac joints. Over time, the disease process promotes extensive remodeling of the spinal axis via ligamentous ossification, vertebral joint fusion, osteoporosis, and kyphosis. These pathological changes result in a weakened vertebral column with increased susceptibility to fractures and spinal cord injury (SCI). Spinal cord injury is often exacerbated by the highly unstable nature of vertebral column fractures in AS. A high incidence of missed fractures in the ankylosed spine as well as an increased incidence of spinal epidural hematoma also worsens the severity of SCI. Spinal cord injury in AS is a complex problem associated with high morbidity and mortality rates, which can be attributed to the severity of the injury, associated medical comorbidities, and the advanced age of most patients with AS who suffer an SCI. In this paper the authors outline the factors that increase the incidence of vertebral column fractures and SCI in AS and discuss the management of SCI in patients with AS. Primary prevention strategies for SCI in patients with AS are outlined as well.

Nerve repair using acidic fibroblast growth factor in human cervical spinal cord injury: a preliminary Phase I clinical study

Object

The aim of this study was to assess functional outcomes of nerve repair using acidic fibroblast growth factor (FGF) in patients with cervical spinal cord injury (SCI).

Methods

Nine patients who had cervical SCI for longer than 5 months were included in pre- and postoperative assessments of their neurological function. The assessments included evaluating activities of daily living, associated functional ability, and degree of spasticity, motor power, sensation, and pain perception. After the first set of assessments, the authors repaired the injured segment of the spinal cord using a total laminectomy followed by the application of fibrin glue containing acidic FGF. Clinical evaluations were conducted 1, 2, 3, 4, 5, and 6 months after the surgery. Preoperative versus postoperative differences in injury severity and grading of key muscle power and sensory points were calculated using the Wilcoxon signed-rank test.

Results

The preoperative degree of injury severity, as measured using the American Spinal Injury Association (ASIA) scoring system, showed that preoperative motor (52.4 ± 25.9 vs 68.6 ± 21.5), pinprick (61.0 ± 34.9 vs 71.6 ± 31.0), and light touch scores (57.3 ± 33.9 vs 71.9 ± 30.2) were significantly lower than the respective postoperative scores measured 6 months after surgery (p = 0.005, 0.012, and 0.008, respectively).

Conclusions

Based on the significant difference in ASIA motor and sensory scale scores between the preoperative status and the 6-month postoperative follow-up, this novel nerve repair strategy of using acidic FGF may have a role in the repair of human cervical SCI. Modest nerve regeneration occurred in all 9 patients after this procedure without any observed adverse effects. This repair strategy thus deserves further investigation, clinical consideration, and refinement.

Cell death after dorsal root injury

Flow cytometry and terminal deoxynucleotidyl transferase-mediated biotinylated uridine triphosphate nick end-labelling (TUNEL) immunohistochemistry have been used to assess cell death in the dorsal root ganglia (DRG) or spinal cord 1, 2 or 14 days after multiple lumbar dorsal root rhizotomy or dorsal root avulsion injury in adult rats. Neither injury induced significant cell death in the DRG compared to sham-operated or naïve animals at any time point. In the spinal cord, a significant increase in death was seen at 1-2 days, but not 14 days, post injury by both methods. TUNEL staining revealed that more apoptotic cells were present in the dorsal columns and dorsal horn of avulsion animals compared to rhizotomised animals. This suggests that avulsion injury, which can often partially damage the spinal cord, has more severe effects on cell survival than rhizotomy, a surgical lesion which does not affect the spinal cord. The location of TUNEL positive cells suggests that both neuronal and non-neuronal cells are dying.

International standards for neurological classification of spinal cord injury: training effect on accurate classification

OBJECTIVE

To evaluate the accuracy and agreement of International Standards for Neurological Classification of Spinal Cord Injury (ISCSCI) classification and to determine the effectiveness of formal training for pediatric clinicians.

STUDY POPULATION

Participants (N = 28) in a formal 90-minute classification training session.

OUTCOME MEASURE

Pre/post-training examination of 10 case examples of a variety of neurological classifications.

RESULTS

Regardless of years of experience with the ISCSCI, a statistically significant improvement (P < 0.05) in classification was achieved after formal training. Before training, 27% (539 of 1,960) of the questions were answered incorrectly. After training, the percentage of incorrect classifications decreased to 11% (198 of 1,960) incorrect (P < 0.05). After training, the percentage of incorrect motor level classifications decreased by 23% (42% to 19% incorrect; P< 0.05). Post-training improvements were also demonstrated (P< 0.05) in classifying sensory levels (9% to 3% incorrect), neurological levels (31% to 6% incorrect), and severity of injury (9% to 0% incorrect). After training, reductions in classification errors (P < 0.05) were demonstrated in American Spinal Injury Association (ASIA) Impairment Scale (AIS) A (from 20% to 7%), B (50% to 11%), C (71% to 46%), and D (63% to 16%).

CONCLUSIONS

This study demonstrated the benefits of formal, standardized training for accurate classification of the ISCSCI. Effective training programs must emphasize the guidelines and decision algorithms used to determine motor level and ASIA AIS designations because these remained problematic after training and are often a concern of patients/parents and are primary endpoints in clinical trials for neurological recovery.

Spinal cord injury: time to move?

This symposium aims at summarizing some of the scientific bases for current or planned clinical trials in patients with spinal cord injury (SCI). It stems from the interactions of four researchers involved in basic and clinical research who presented their work at a dedicated Symposium of the Society for Neuroscience in San Diego. After SCI, primary and secondary damage occurs and several endogenous processes are triggered that may foster or hinder axonal reconnection from supralesional structures. Studies in animals show that some of these processes can be enhanced or decreased by exogenous interventions using drugs to diminish repulsive barriers (anti-Nogo, anti-Rho) that prevent regeneration and/or sprouting of axons. Cell grafts are also envisaged to enhance beneficial immunological mechanisms (autologous macrophages, vaccines) or remyelinate axons (oligodendrocytes derived from stem cells). Some of these treatments could be planned concurrently with neurosurgical approaches that are themselves beneficial to decrease secondary damage (e.g., decompression/reconstructive spinal surgery). Finally, rehabilitative approaches based on the presence of functional networks (i.e., central pattern generator) below the lesion combined with the above neurobiological approaches may produce significant functional recovery of some sensorimotor functions, such as locomotion, by ensuring an optimal function of endogenous spinal networks and establishing new dynamic interactions with supralesional structures. More work is needed on all fronts, but already the results offer great hope for functional recovery after SCI based on sound basic and clinical neuroscience research.

Omega-3 fatty acids and neurological injury

Studies with omega-3 polyunsaturated fatty acids (PUFA) have shown that these compounds have therapeutic potential in several indications in neurology and psychiatry. Acute spinal cord injury (SCI) is an event with devastating consequences, and no satisfactory treatment is available at present. The pathogenetic mechanisms associated with SCI include excitotoxicity, increased oxidation and inflammation. We review here our recent studies, which suggest that omega-3 PUFA have significant neuroprotective potential in spinal cord trauma. In a first study, we administered an intravenous bolus of alpha-linolenic acid (LNA) or docosahexaenoic acid (DHA) 30 min after spinal cord hemisection injury in adult rats. The omega-3 PUFA led to increased neuronal and glial survival, and a significantly improved neurological outcome. In subsequent studies, we tested DHA in a more severe compression model of SCI. We also explored a combined acute and chronic treatment regime using DHA. Saline or DHA was administered intravenously 30 min after compression of the spinal cord. After injury, the saline group received a standard control diet, whereas DHA-injected animals received either a control or a DHA-enriched diet for 6 weeks following injury. We assessed locomotor recovery and analysed markers for cell survival and axonal damage, and we also investigated the effects of the treatment on the inflammatory reaction and the oxidative stress that follow SCI. We showed that the acute DHA treatment is neuroprotective after compression SCI, even if the treatment is delayed up to an hour after injury. The DHA injection led to an increased neuronal and glial cell survival, and the effect of the DHA injection was amplified by addition of DHA to the diet. Rats treated with a DHA injection and a DHA-enriched diet performed significantly better at 6 weeks in terms of neurological outcome. The analysis of the tissue after DHA administration showed that the fatty acid significantly reduced lipid peroxidation, protein oxidation and RNA/DNA oxidation, and the induction of COX-2. Parallel studies in a facial nerve injury model in mice also showed pro-regenerative effects of chronic dietary administration of DHA after nerve lesion. These observations suggest that treatment with omega-3 PUFA could represent a promising therapeutic approach in the management of neurological injury.

The neuroprotective potential of phase II enzyme inducer on motor neuron survival in traumatic spinal cord injury in vitro

(1) Phase II enzyme inducer is a kind of compound which can promote the expression of antioxidative enzymes through nuclear factor erythroid 2-related factor 2 (Nrf2) activation. Recently, it has been reported that these compounds show neuroprotective effect via combating oxidative stress. The purpose of this study is to determine whether phase II enzyme inducers have neuroprotective effects on traumatic spinal cord injury. (2) An organotypic spinal cord culture system was used, Phase II enzyme inducers were added to culture medium for 1 week, motor neurons were counted by SMI-32 staining, glutamate, Nrf2, and Heme oxygenase-1(HO-1) mRNA were tested. (3) This study showed motor neuron loss within 1 week in culture. After 1 week in culture, the system was stable. Moreover, Glutamate was increased when in culture 48 h and decreased after 1 week in culture. There was no significant change between 1 and 4 weeks in culture. Necrotic motor neuron and damaged mitochondrial were observed in culture 48 h. Furthermore, phase II enzyme inducers: tert-butyhydroquinone (t-BHQ), 3H-1,2-dithiole-3-thione (D3T), and 5,6-dihydrocyclopenta-1,2-dithiole-3-thione (CPDT) were shown to promote motor neuron survival after dissection, it was due to increasing Nrf2 and HO-1 mRNA expression and protecting mitochondrial not due to decreasing glutamate level. (4) The loss of motor neuron due to dissection can mimic severe traumatic spinal cord injury. These results demonstrate that glutamate excitotoxicity and the damage of mitochondrial is possibly involve in motor neuron death after traumatic spinal cord injury and phase II enzyme inducers show neuroprotective potential on motor neuron survival in traumatic spinal cord injury in vitro.

Combination of dexamethasone and etanercept reduces secondary damage in experimental spinal cord trauma

The aim of our study was to evaluate the therapeutic efficacy of combination therapy with etanercept and dexamethasone (DEX) in vivo in experimental murine model of spinal cord trauma, which was induced by the application of vascular clips (force of 24 g) to the dura via a four-level T5-T8 laminectomy. Spinal cord injury in mice resulted in severe trauma characterized by edema, neutrophil infiltration, and cytokine production followed by recruitment of other inflammatory cells, production of inflammation mediators, tissue damage, apoptosis and disease. Treatment of the mice with etanercept (1.25 mg/kg) and DEX (0.025 mg/kg) when administered as a combination therapy but not as a single treatment significantly reduced the degree of (1) spinal cord inflammation and tissue injury (histological score), (2) infiltration of neutrophils (MPO evaluation), (3) inducible nitric oxide synthase, nitrotyrosine, and cytokines expression (tumor necrosis factor-alpha and interleukin-1 beta), (4) and apoptosis (Terminal deoxynucleotidyltransferase-mediated UTP end labeling staining, Fas-ligand expression and Bax and Bcl-2 expression). In a separate set of experiments we have also clearly demonstrated that the combination therapy significantly ameliorated the recovery of limb function (evaluated by motor recovery score). Taken together, our results clearly demonstrate for the first time that strategies targeting multiple proinflammatory pathways may be more effective than a single effector molecule for the treatment of spinal cord trauma.

Aortic cross-clamping-induced spinal cord oxidative stress in rabbits: the role of a novel antioxidant adrenomedullin

BACKGROUND

Spinal cord injury remains a devastating complication of thoracic and thoracoabdominal aortic operations. We aim to investigate the neuro-protective role of adrenomedullin (AM) administered to rabbits before ischemia and during reperfusion against ischemia-reperfusion (I/R) injury.

MATERIALS AND METHODS

Occlusion of the abdominal aorta was applied to adult rabbits, followed by removal of aortic clamp and reperfusion. The abdominal aortas of New Zealand white albino rabbits were occluded for 30 min. Experimental groups were as follows: control group (sham operation group, n = 10), I/R group (n = 9) undergoing occlusion but receiving no pharmacologic intervention, AM-treated group (n = 8) receiving 0.05 microg/kg/min AM intravenously 10 min before ischemia and during reperfusion. Neurological status was assessed at 6, 24, and 48 h after the operation. All animals were killed at 48 h after the operation. Spinal cords were harvested for histopathologic and biochemical analyses.

RESULTS

According to Tarlov's scale, neurological status of the rabbits at postoperative hour 48 was better in the AM-treated group compared to the I/R group (P < 0.05). Decreased tissue and serum malondialdehyde levels and increased tissue and serum glutathione levels were observed in the AM-treated group (P < 0.05). In the same group tissue and serum nitrate levels were decreased (P < 0.05). Histopathologic analyses demonstrated typical morphological changes characteristic of necrosis in the I/R group. AM attenuated ischemia-induced necrosis.

CONCLUSION

To our knowledge, this is the first study that shows the effects of AM administered both preischemic and during reperfusion on induced oxidative damage to injured spinal cords. AM administration may significantly reduce the incidence of spinal cord injury following temporary aortic occlusion.

Antiapoptotic therapies in the treatment of spinal cord injury

Mechanical trauma to the spinal cord triggers events resulting in the death of neurons and glia over several weeks following the initial injury. It has been suggested that the prevention of delayed apoptosis after spinal cord injury (SCI) is likely to have a beneficial effect by reducing the extent of neuronal and oligodendroglial death, which would translate into better functional outcomes. Drugs acting at different levels in the apoptotic cascade (i.e., caspase inhibitors and antiapoptotic Bcl-xL) have been shown to decrease apoptotic cell death, but benefits in functional outcomes result only when inflammation is also decreased. Furthermore, long-term antiapoptotic therapy can result in nonapoptotic death with necrotic features, which will further increase inflammation and worsen outcome. Even though neuroprotective therapies are one of the targets for the promotion of functional recovery after SCI, targeting only post-SCI apoptosis is unlikely to be as successful as more integrated interventions that also target inflammation.

An overview of tissue engineering approaches for management of spinal cord injuries

Severe spinal cord injury (SCI) leads to devastating neurological deficits and disabilities, which necessitates spending a great deal of health budget for psychological and healthcare problems of these patients and their relatives. This justifies the cost of research into the new modalities for treatment of spinal cord injuries, even in developing countries. Apart from surgical management and nerve grafting, several other approaches have been adopted for management of this condition including pharmacologic and gene therapy, cell therapy, and use of different cell-free or cell-seeded bioscaffolds. In current paper, the recent developments for therapeutic delivery of stem and non-stem cells to the site of injury, and application of cell-free and cell-seeded natural and synthetic scaffolds have been reviewed.

Influence of cross-linked hyaluronic acid hydrogels on neurite outgrowth and recovery from spinal cord injury

OBJECT

Therapies that use bioactive materials as replacement extracellular matrices may hold the potential to mitigate the inhibition of regeneration observed after central nervous system trauma. Hyaluronic acid (HA), a nonsulfated glycosaminoglycan ubiquitous in all tissues, was investigated as a potential neural tissue engineering matrix.

METHODS

Chick dorsal root ganglia were cultured in 3D hydrogel matrices composed of cross-linked thiol-modified HA or fibrin. Samples were cultured and images were acquired at 48-, 60-, and 192-hour time points. Images of all samples were analyzed at 48 hours of incubation to quantify the extent of neurite growth. Cultures in crosslinked thiolated HA exhibited more than a 50% increase in neurite length compared with fibrin samples. Furthermore, cross-linked thiolated HA supported neurites for the entire duration of the culture period, whereas fibrin cultures exhibited collapsed and degenerating extensions beyond 60 hours. Two concentrations of the thiolated HA (0.5 and 1%) were then placed at the site of a complete thoracic spinal cord transection in rats. The ability of the polymer to promote regeneration was tested using motor evoked potentials, retrograde axonal labeling, and behavioral assessments. There were no differences in any of the parameters between rats treated with the polymer and controls.

CONCLUSIONS

The use of a cross-linked HA scaffold promoted robust neurite outgrowth. Although there was no benefit from the polymer in a rodent spinal cord injury model, the findings in this study represent an early step in the development of semisynthetic extracellular matrice scaffolds for the treatment of neuronal injury.

Immediate Damage to The Blood-Spinal Cord Barrier Due to Mechanical Trauma

Primary damage to the blood-spinal cord barrier (BSCB) is a nearly universal consequence of spinal cord injury that contributes significantly to the overall pathology, including the introduction of reactive species that induce cytotoxicity as well as secondary insults on the BSCB itself. We have characterized quantitatively the extent and severity of primary, physical disruption of the BSCB in adult rats 5 min after graded trauma induced with the Impactor weight-drop model of spinal cord contusion. Animals were injured by dropping a 10-g mass 12.5, 25, or 50 mm (n(level) = 8) on to the exposed mid-thoracic spinal cord. The volume of extravasation of three markers of distinct size--fluorescently labeled hydrazide ( approximately 730 Da), fluorescently labeled bovine serum albumin ( approximately 70 kDa), and immunohistochemically labeled red blood cells ( approximately 5 microm in diameter)--were quantified in both the gray and white matter. The results indicate that spinal cord trauma causes immediate, non-specific vascular changes that are well-predicted by mechanical parameters. Extravasation volume increased significantly with increasing drop height and decreasing marker size. Extravasation volumes for all three markers were greater in gray matter than in white matter, and were better correlated to the rate of spinal cord compression than to the depth of spinal cord compression, which suggests that tissue-level strain rate effects contribute to primary spinal cord microvasculature pathology. The relationship between the response of the spinal cord and the injury pattern points towards opportunities to control the distribution and extent of injury patterns in animal models of spinal cord injury through a precise understanding of model and tissue biomechanics, as well as potential improvements in means of preventing spinal cord injury.

Therapeutic interventions after spinal cord injury

Spinal cord injury (SCI) can lead to paraplegia or quadriplegia. Although there are no fully restorative treatments for SCI, various rehabilitative, cellular and molecular therapies have been tested in animal models. Many of these have reached, or are approaching, clinical trials. Here, we review these potential therapies, with an emphasis on the need for reproducible evidence of safety and efficacy. Individual therapies are unlikely to provide a panacea. Rather, we predict that combinations of strategies will lead to improvements in outcome after SCI. Basic scientific research should provide a rational basis for tailoring specific combinations of clinical therapies to different types of SCI.