Basic advances and new avenues in therapy of spinal cord injury

A novel minimally invasive and versatile kyphoplasty balloon-based model of porcine spinal cord injury

Introduction

Spinal cord injury (SCI) animal models often utilize an open surgical laminectomy, which results in animal morbidity and also leads to changes in spinal canal diameter, spinal cord perfusion, cerebrospinal fluid flow dynamics, and spinal stability which may confound SCI research. Moreover, the use of open surgical laminectomy for injury creation lacks realism when considering human SCI scenarios.

Methods

We developed a novel, image-guided, minimally invasive, large animal model of SCI which utilizes a kyphoplasty balloon inserted into the epidural space via an interlaminar approach without the need for open surgery.

Results

The model was validated in 5 Yucatán pigs with imaging, neurofunctional, histologic, and electrophysiologic findings consistent with a mild compression injury.

Discussion

Few large animal models exist that have the potential to reproduce the mechanisms of spinal cord injury (SCI) commonly seen in humans, which in turn limits the relevance and applicability of SCI translational research. SCI research relies heavily on animal models, which typically involve an open surgical, dorsal laminectomy which is inherently invasive and may have untoward consequences on animal morbidity and spinal physiology that limit translational impact. We developed a minimally invasive, large animal model of spinal cord injury which utilizes a kyphoplasty balloon inserted percutaneously into the spinal epidural space. Balloon inflation results in a targeted, compressive spinal cord injury with histological and electrophysiological features directly relevant to human spinal cord injury cases without the need for invasive surgery. Balloon inflation pressure, length of time that balloon remains inflated, and speed of inflation may be modified to achieve variations in injury severity and subtype.

Robotic locomotor training in a low-resource setting: a randomized pilot and feasibility trial

PURPOSE

Activity-based Training (ABT) represents the current standard of neurological rehabilitation. Robotic Locomotor Training (RLT), an innovative technique, aims to enhance rehabilitation outcomes. This study aimed to conduct a randomized pilot and feasibility trial of a locomotor training program within South Africa.

MATERIALS AND METHODS

Individuals with chronic traumatic motor incomplete tetraplegia (n = 16). Each intervention involved 60-minute sessions, 3x per week, for 24-weeks. Outcomes included feasibility measures and functional capacity.

RESULTS

17 out of 110 individuals initiated the program (recruitment rate = 15.4%) and 16 completed the program (drop-out rate = 5.8%) and attended sessions (attendance rate = 93.9%). Both groups showed a significant increase in upper extremity motor score (MS) and abdominal strength post intervention. Only the RLT group showed a significant change in lower extremity MS, with a mean increase of 3.00 [0.00; 16.5] points over time. Distance walked in the Functional Ambulatory Inventory (SCI-FAI) increased significantly (p = 0.02) over time only for the RLT group.

CONCLUSIONS

Feasibility rates of the intervention and functional outcomes justify a subsequent powered RCT comparing RLT to ABT as an effective rehabilitation tool for potentially improving functional strength and walking capacity in people with incomplete SCI.

BCI system with lower-limb robot improves rehabilitation in spinal cord injury patients through short-term training: a pilot study

In the recent years, the increasing applications of brain-computer interface (BCI) in rehabilitation programs have enhanced the chances of functional recovery for patients with neurological disorders. We presented and validated a BCI system with a lower-limb robot for short-term training of patients with spinal cord injury (SCI). The cores of this system included: (1) electroencephalogram (EEG) features related to motor intention reported through experiments and used to drive the robot; (2) a decision tree to determine the training mode provided for patients with different degrees of injuries. Seven SCI patients (one American Spinal Injury Association Impairment Scale (AIS) A, three AIS B, and three AIS C) participated in the short-term training with this system. All patients could learn to use the system rapidly and maintained a high intensity during the training program. The strength of the lower limb key muscles of the patients was improved. Four AIS A/B patients were elevated to AIS C. The cumulative results indicate that clinical application of the BCI system with lower-limb robot is feasible and safe, and has potentially positive effects on SCI patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11571-022-09801-6.

Systemic Administration of Allogeneic Cord Blood Mononuclear Cells in Adults with Severe Acute Contusion Spinal Cord Injury: Phase I/IIa Pilot Clinical Study - Safety and Primary Efficacy Evaluation

OBJECTIVES

Current Phase I part of SUBSCI I/IIa study was focused on safety and primary efficacy of multiple systemic infusions of allogeneic unrelated human umbilical cord blood mononuclear cells in patients with severe acute spinal cord contusion having severe neurological deficit. The primary endpoint was safety. The secondary endpoint was the fact of restoration of motor and sensory function in lower limbs within 1-year period.

METHODS

Ten subjects with acute contusion SCI and ASIA A/B deficit were enrolled into Phase I part. Subjects were treated with 4 infusions of group- and rhesus-matched cord blood samples following primary surgery within 3 days post-SCI. All patients were followed-up for 12 months post-SCI. Safety was assessed using adverse events classification depending on severity and relation to cell therapy. Primary efficacy was assessed using dynamics of deficit (ASIA scale).

RESULTS

The overall number of AEs reached 419 in 10 subjects. Only 2 of them were estimated as possibly related to cell therapy, other 417 were definitely unrelated. Both AEs were mild and clinically insignificant. No signs of immunization were found in participants. Analysis of clinical outcomes also demonstrated that cell therapy promotes significant functional restoration of motor function.

CONCLUSIONS

Obtained data suggest that systemic administration of allogenic, non-HLA matched HUCB cells is safe and demonstrates primary efficacy in adults with severe acute contusion SCI and ASIA A/B deficit.

Automated lever task with minimum antigravity movement for rats with cervical spinal cord injury

BACKGROUND

Although there is currently no cure for paralysis due to spinal cord injury (SCI), the highest treatment priority is restoring arm and hand function for people with cervical SCI. Preclinical animal models provide an opportunity to test innovative treatments, but severe cervical injury models require significant time and effort to assess responses to novel interventions. Moreover, there is no behavioral task that can assess forelimb movement in rats with severe cervical SCI unable to perform antigravity movements.

NEW METHOD

We developed a novel lever pressing task for rats with severe cervical SCI. We employed an automated adaptive algorithm to train animals using open-source software and commercially available hardware. We found that using the adaptive training required only 13.3 ± 2.5 training days to achieve behavioral proficiency. The lever press task could quantify immediate and long-term improvements in severely impaired forelimb function effectively. This behavior platform has potential to facilitate rehabilitative training and assess effects of therapeutic modalities following SCI.

COMPARISON WITH EXISTING METHODS

There is no existing assessment aiming to quantify forelimb extension movement in rodents without function against gravity. We found that the new lever press task in the antigravity position could assess the severity of cervical SCI as well as the compensatory movement in the proximal forelimb less affected by the injury.

CONCLUSIONS

This study demonstrates that the new behavioral task is capable of tracking the functional changes with various therapies in rats with severe forelimb impairments in a cost- and time-efficient manner.

Characterization of Spinal Sensorimotor Network Using Transcutaneous Spinal Stimulation during Voluntary Movement Preparation and Performance

Transcutaneous electrical spinal stimulation (TSS) can be used to selectively activate motor pools based on their anatomical arrangements in the lumbosacral enlargement. These spatial patterns of spinal motor activation may have important clinical implications, especially when there is a need to target specific muscle groups. However, our understanding of the net effects and interplay between the motor pools projecting to agonist and antagonist muscles during the preparation and performance of voluntary movements is still limited. The present study was designed to systematically investigate and differentiate the multi-segmental convergence of supraspinal inputs on the lumbosacral neural network before and during the execution of voluntary leg movements in neurologically intact participants. During the experiments, participants (N = 13) performed isometric (1) knee flexion and (2) extension, as well as (3) plantarflexion and (4) dorsiflexion. TSS consisting of a pair pulse with 50 ms interstimulus interval was delivered over the T12-L1 vertebrae during the muscle contractions, as well as within 50 to 250 ms following the auditory or tactile stimuli, to characterize the temporal profiles of net spinal motor output during movement preparation. Facilitation of evoked motor potentials in the ipsilateral agonists and contralateral antagonists emerged as early as 50 ms following the cue and increased prior to movement onset. These results suggest that the descending drive modulates the activity of the inter-neuronal circuitry within spinal sensorimotor networks in specific, functionally relevant spatiotemporal patterns, which has a direct implication for the characterization of the state of those networks in individuals with neurological conditions.

Robot-Assisted Gait Training in Patients with Multiple Sclerosis: A Randomized Controlled Crossover Trial

Background and Objectives: Gait disorders represent one of the most disabling aspects in multiple sclerosis (MS) that strongly influence patient quality of life. The improvement of walking ability is a primary goal for rehabilitation treatment. The aim of this study is to evaluate the effectiveness of robot-assisted gait training (RAGT) in association with physiotherapy treatment in patients affected by MS in comparison with ground conventional gait training. Study design: Randomized controlled crossover trial. Materials and Methods: Twenty-seven participants affected by MS with EDSS scores between 3.5 and 7 were enrolled, of whom seventeen completed the study. They received five training sessions per week over five weeks of conventional gait training with (experimental group) or without (control group) the inclusion of RAGT. The patients were prospectively evaluated before and after the first treatment session and, after the crossover phase, before and after the second treatment session. The evaluation was based on the 25-foot walk test (25FW, main outcome), 6 min walk test (6MWT), Tinetti Test, Modified Ashworth Scale, and modified Motricity Index for lower limbs. We also measured disability parameters using Functional Independence Measure and Quality of Life Index, and instrumental kinematic and gait parameters: knee extensor strength, double-time support, step length ratio; 17 patients reached the final evaluation. Results: Both groups significantly improved on gait parameters, motor abilities, and autonomy recovery in daily living activities with generally better results of RAGT over control treatment. In particular, the RAGT group improved more than control group in the 25FW (p = 0.004) and the 6MWT (p = 0.022). Conclusions: RAGT is a valid treatment option that in association with physiotherapy could induce positive effects in MS-correlated gait disorders. Our results showed greater effectiveness in recovering gait speed and resistance than conventional gait training.

Insulin-like Growth Factor-1 Receptor Dictates Beneficial Effects of Treadmill Training by Regulating Survival and Migration of Neural Stem Cell Grafts in the Injured Spinal Cord

Survival and migration of transplanted neural stem cells (NSCs) are prerequisites for therapeutic benefits in spinal cord injury. We have shown that survival of NSC grafts declines after transplantation into the injured spinal cord, and that combining treadmill training (TMT) enhances NSC survival via insulin-like growth factor-1 (IGF-1). Here, we aimed to obtain genetic evidence that IGF-1 signaling in the transplanted NSCs determines the beneficial effects of TMT. We transplanted NSCs heterozygous (+/-) for Igf1r, the gene encoding IGF-1 receptor, into the mouse spinal cord after injury, with or without combining TMT. We analyzed the influence of genotype and TMT on locomotor recovery and survival and migration of NSC grafts. In vitro experiments were performed to examine the potential roles of IGF-1 signaling in the migratory ability of NSCs. Mice receiving +/- NSC grafts showed impaired locomotor recovery compared with those receiving wild-type (+/+) NSCs. Locomotor improvement by TMT was more pronounced with +/+ grafts. Deficiency of one allele of Igf1r significantly reduced survival and migration of the transplanted NSCs. Although TMT did not significantly influence NSC survival, it substantially enhanced the extent of migration for only +/+ NSCs. Cultured neurospheres exhibited dynamic motility with cytoplasmic protrusions, which was regulated by IGF-1 signaling. IGF-1 signaling in transplanted NSCs may be essential in regulating their survival and migration. Furthermore, TMT may promote NSC graft-mediated locomotor recovery via activation of IGF-1 signaling in transplanted NSCs. Dynamic NSC motility via IGF-1 signaling may be the cellular basis for the TMT-induced enhancement of migration.

Loss of inhibitory synapses causes locomotor network dysfunction of the rat spinal cord during prolonged maintenance in vitro

The isolated spinal cord of the neonatal rat is widely employed to clarify the basic mechanisms of network development or the early phase of degeneration after injury. Nevertheless, this preparation survives in Krebs solution up to 24 h only, making it desirable to explore approaches to extend its survival for longitudinal studies. The present report shows that culturing the spinal cord in oxygenated enriched Basal Medium Eagle (BME) provided excellent preservation of neurons (including motoneurons), glia and primary afferents (including dorsal root ganglia) for up to 72 h. Using DMEM medium was unsuccessful. Novel characteristics of spinal networks emerged with strong spontaneous activity, and deficit in fictive locomotion patterns with stereotypically slow cycles. Staining with markers for synaptic proteins synapsin 1 and synaptophysin showed thoroughly weaker signal after 3 days in vitro. Immunohistochemical staining of markers for glutamatergic and glycinergic neurons indicated significant reduction of the latter. Likewise, there was lower expression of the GABA-synthesizing enzyme GAD65. Thus, malfunction of locomotor networks appeared related to loss of inhibitory synapses. This phenomenon did not occur in analogous opossum preparations of the spinal cord kept in vitro. In conclusion, despite histological data suggesting that cultured spinal cords were undamaged (except for inhibitory biomarkers), electrophysiological data revealed important functional impairment. Thus, the downregulation of inhibitory synapses may account for the progressive hyperexcitability of rat spinal networks despite apparently normal histological appearance. Our observations may help to understand the basis of certain delayed effects of spinal injury like chronic pain and spasticity.

Lycopsamine Exerts Protective Effects and Improves Functional Outcome After Spinal Cord Injury in Rats by Suppressing Cell Death

Background

Spinal cord injury (SCI) is an injury-triggered event that is associated with permanent neurologic deficit. The deficit instigated by SCI leads to medical co-morbidity, not only affecting sensory and motor capabilities, but also having an impact on the physiological and economic condition of the patient. Against this backdrop, the present study was carried out to investigate the effect of lycopsamine, a plant-derived alkaloid in SCI rats.

Material/Methods

The traumatic SCI injury in rats was created using a force-calibrated weight-drop device. The Basso-Beattie-Bresnahan (BBB) locomotor rating scale was used to investigate the functional consequences of SCI. DAPI (4′,6-diamidino-2-phenylindole) and Tunnel staining were used to detect apoptosis. Western blot and qRT-PCR was used to examine the protein and gene expressions, respectively.

Results

The results revealed that lycopsamine significantly (p<0.01) improved locomotory function in SCI rats. Lycopsamine also significantly (p<0.01) decreased the lesion area of the SCI rats. Investigation of the effect of lycopsamine on cell death following SCI revealed that lycopsamine reduces apoptotic cell death following SCI. The lycopsamine-induced reduction in apoptosis was allied with downregulation of calpain, cleaved caspase 3 and 9, and Bax. However, the expression of BCl-2 was significantly upregulated. Furthermore, lycopsamine significantly (p<0.01) upregulated the expression of interleukin-10 (IL-10) and decreased the expression of tumor necrosis factor-α (TNF-α).

Conclusions

Lycopsamine exerts protective effects in PCI rats by improving functional recovery and suppressing apoptosis.

Inhibition of the Ras/Raf/extracellular signal-regulated kinase 1/2 signaling pathway by compounds of natural origin for possible treatment of spinal cord injury: An in silico approach

Spinal cord injury (SCI) is a severe disease associated with permanent neurological deficit. Recent studies in the treatment of SCI have demonstrated that the Ras/Raf/extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway serves an important role in the disease etiology, and that upregulation of this signaling pathway is associated with the development of SCI. In the present study, inhibition of Ras protein was employed in order to downregulate the Ras/Raf/ERK1/2 signaling pathway using compounds of natural origin from the Interbioscreen natural compound database. To the best of our knowledge, this is the first study using a chemical-computational approach in order to identify novel small molecule inhibitors for Ras. A database of ~50,000 compounds was selected for virtual screening, setting a free energy binding bias of −7 kcal/mol to limit the number of compounds. The subset of compounds generated by virtual screening was further limited by subjecting these to the Lipinski's rule of five parameters. A total of five shortlisted compounds were subjected to molecular docking simulation. The compounds were docked into the GTP binding site of Ras, and the inhibition of this site was examined as a promising strategy for the downregulation of Ras/Raf/ERK1/2 signaling pathway. The compounds bound to the GTP binding site through hydrogen bonds and hydrophobic interactions. The identified lead compound was then subjected to molecular dynamics simulation, and the results revealed that GLY60 in the GTP binding site of Ras protein was the optimal binding site during a 100 nsec run.

Efficacy and safety of 9 nonoperative regimens for the treatment of spinal cord injury: A network meta-analysis

OBJECTIVE

This network meta-analysis aims to compare the efficacy and safety of 9 nonoperative regimens (placebo, pregabalin, GM-1 ganglioside, venlafaxine extended-release [venlafaxine XR], fampridine, conventional over-ground training [OT], body-weight-supported treadmill training [BWSTT], robotic-assisted gait training [RAGT] + OT and body-weight-supported over-ground training [BWSOT]) in treating spinal cord injury (SCI).

METHODS

Clinical controlled trials of 9 nonoperative regimens for SCI were retrieved in the electronic database. Traditional pairwise and Bayesian network meta-analyses were performed to compare the efficacy and safety of 9 nonoperative regimens for the treatment of SCI. Weighted mean difference (WMD), odds ratios (OR), and surface under the cumulative ranking curve (SUCRA) were calculated using the Markov Chain Monte Carlo engine Open BUGS (V.3.4.0) and R (V.3.2.1) package gemtc (V.0.6).

RESULTS

A total of 9 clinical controlled trials meeting the inclusion criteria were selected in this meta-analysis. On the aspect of efficacy, the results of pairwise meta-analysis indicated that the RAGT + OT and BWSOT might have the best efficacy in SCI patients in terms of a lower extremity motor score (LEMS) compared with conventional OT; the efficacy of RAGT + OT on SCI patients was relatively better than that of conventional OT in terms of walking index for spinal cord injury (WISCI). With the aspect of safety, the constipation rate of placebo on SCI patients was relatively higher than that of venlafaxine XR; however, with respect to headache and urinary tract infection, there was no significant difference in the safety of placebo, pregabalin, GM-1 ganglioside, venlafaxine XR, and fampridine on SCI patients. The results of SUCRA values suggested that BWSOT had the highest SUCRA value (75.25%) of LEMS; RAGT + OT had the highest SUCRA value (88.50%) of WISCI; venlafaxine XR had the highest SUCRA value (94.00%) of constipation; venlafaxine XR had the highest SUCRA value (80.00%) of headache; GM-1 ganglioside had the highest SUCRA value (87.75%) of urinary tract infection.

CONCLUSION

Our results provide evidence that the RAGT + OT and BWSOT might have the best efficacy in the treatment of SCI, and the venlafaxine XR and GM-1 ganglioside showed adequate safety for SCI.

Gene silencing NMII promotes axonal regeneration against contusive spinal cord injury in rats

There are drastic changes that occur in the impaired regions after spinal cord injury (SCI), however, improvement of the detrimental pathological process after injury is limited in the mammalian adult, which is due a large part to the failure of local axons to grow. Non-muscle myosin II (NMII) has been proved having essential role in the regulation of cytoskeletal structure and genetic silencing NMII markedly accelerates axon growth in vitro. Our purpose is to explore the association between phosphorylated NMII expression and axonal regeneration after SCI in rats and determine whether gene silencing NMII can improve the locomotor function in rats with SCI. The results showed that phosphorylated NMII level was up regulated after SCI and may even play important role in inhibiting neuronal survival and axonal regeneration. After silencing NMII, the viability of neurons, proliferation of axons, synaptic connection and locomotor functional recovery were promoted significantly after SCI. Our study provides an effective way by direct regulation of neuron viability, the proliferation of axons and synaptic connection for treating SCI, which may be a novel method for repairing SCI. However, the specific signaling pathway mechanisms about the recovery require further study.

Transplantation of Hematopoietic Stem Cells Promotes Functional Improvement Associated with NT-3-MEK-1 Activation in Spinal Cord-Transected Rats

Transected spinal cord injury (SCT) is a devastating clinical disease that strongly affects a patient’s daily life and remains a great challenge for clinicians. Stem-cell therapy has been proposed as a potential therapeutic modality for SCT. To investigate the effects of hematopoietic stem cells (HSCs) on the recovery of structure and function in SCT rats and to explore the mechanisms associated with recovery, 57 adult Sprague-Dawley rats were randomly divided into sham (n = 15), SCT (n = 24), and HSC transplantation groups (n = 15). HSCs (passage 3) labeled by Hoechst 33342, were transplanted intraspinally into the rostral, scar and caudal sites of the transected lesion at 14 days post-operation. Both in vitro and in vivo, HSCs exhibited a capacity for cell proliferation and differentiation. Following HSC transplantation, the animals’ Basso, Beattie, and Bresnahan (BBB). locomotion scale scores increased significantly between weeks 4 and 24 post-SCT, which corresponded to an increased number of 5-hydroxytryptamine (5-HT) fibers and oligodendrocytes. The amount of astrogliosis indicated by immunohistochemical staining, was markedly decreased. Moreover, the decreased expression of neurotrophin- 3 (NT-3) and mitogen-activated protein kinase kinase-1 (MEK-1) after SCT was effectively restored by HSC transplantation. The data from the current study indicate that intraspinally administered HSCs in the chronic phase of SCT results in an improvement in neurological function. Further, the results indicate that intraspinally administered HSCs benefit the underlying mechanisms involved in the enhancement of 5-HT-positive fibers and oligogenesis, the suppression of excessive astrogliosis and the upregulation of NT3-regulated MEK-1 activation in the spinal cord. These crucial findings reveal not only the mechanism of cell therapy, but may also contribute to a novel therapeutic target for the treatment of spinal cord injury (SCI).

A ventral root avulsion injury model for neurogenic underactive bladder studies

Detrusor underactivity (DU) is defined as a contraction of reduced strength and/or duration during bladder emptying and results in incomplete and prolonged bladder emptying. The clinical diagnosis of DU is challenging when present alone or in association with other bladder conditions such as detrusor overactivity, urinary retention, detrusor hyperactivity with impaired contractility, aging, and neurological injuries. Several etiologies may be responsible for DU or the development of an underactive bladder (UAB), but the pathobiology of DU or UAB is not well understood. Therefore, new clinically relevant and interpretable models for studies of UAB are much needed in order to make progress towards new treatments and preventative strategies. Here, we review a neuropathic cause of DU in the form of traumatic injuries to the cauda equina (CE) and conus medullaris (CM) portions of the spinal cord. Lumbosacral ventral root avulsion (VRA) injury models in rats mimic the clinical phenotype of CM/CE injuries. Bilateral VRA injuries result in bladder areflexia, whereas a unilateral lesion results in partial impairment of lower urinary tract and visceromotor reflexes. Surgical re-implantation of avulsed ventral roots into the spinal cord and pharmacological strategies can augment micturition reflexes. The translational research need for the development of a large animal model for UAB studies is also presented, and early studies of lumbosacral VRA injuries in rhesus macaques are discussed.

A study of cannabinoid-1 receptors during the early phase of excitotoxic damage to rat spinal locomotor networks in vitro

Endocannabinoids acting on cannabinoid-1 receptors (CB1Rs) are proposed to protect brain and spinal neurons from excitotoxic damage. The ability to recover from spinal cord injury (SCI), in which excitotoxicity is a major player, is usually investigated at late times after modulation of CB1Rs whose role in the early phases of SCI remains unclear. Using the rat spinal cord in vitro as a model for studying SCI initial pathophysiology, we investigated if agonists or antagonists of CB1Rs might affect SCI induced by the excitotoxic agent kainate (KA) within 24h from a transient (1h) application of this glutamate agonist. The CB1 agonist anandamide (AEA or pharmacological block of its degradation) did not limit excitotoxic depolarization of spinal networks: cyclic adenosine monophosphate (cAMP) assay demonstrated that CB1Rs remained functional 24h later and similarly expressed among dead or survived cells. Locomotor-like network activity recorded from ventral roots could not recover with such treatments and was associated with persistent depression of synaptic transmission. Motoneurons, that are particularly vulnerable to KA, were not protected by AEA. Application of 2-arachidonoylglycerol also did not attenuate the electrophysiological and histological damage. The intensification of damage by the CB1 antagonist AM251 suggested that endocannabinoids were operative after excitotoxic stimulation, yet insufficient to contrast it efficiently. The present data indicate that the early phases of excitotoxic SCI could not be arrested by pharmacologically exploiting the endocannabinoid system, consistent with the notion that AEA and its derivatives are more useful to treat late SCI phases.

Neuroprotective effect of propofol against excitotoxic injury to locomotor networks of the rat spinal cord in vitro

Although neuroprotection to contain the initial damage of spinal cord injury (SCI) is difficult, multicentre studies show that early neurosurgery under general anaesthesia confers positive benefits. An interesting hypothesis is that the general anaesthetic itself might largely contribute to neuroprotection, although in vivo clinical settings hamper studying this possibility directly. To further test neuroprotective effects of a widely used general anaesthetic, we studied if propofol could change the outcome of a rat isolated spinal cord SCI model involving excitotoxicity evoked by 1 h application of kainate with delayed consequences on neurons and locomotor network activity. Propofol (5 μm; 4-8 h) enhanced responses to GABA and depressed those to NMDA together with decrease in polysynaptic reflexes that partly recovered after 1 day washout. Fictive locomotion induced by dorsal root stimuli or NMDA and serotonin was weaker the day after propofol application. Kainate elicited a significant loss of spinal neurons, especially motoneurons, whose number was halved. When propofol was applied for 4-8 h after kainate washout, strong neuroprotection was observed in all spinal areas, including attenuation of motoneuron loss. Although propofol had minimal impact on recovery of electrophysiological characteristics 24 h later, it did not further depress network activity. A significant improvement in disinhibited burst periodicity suggested potential to ameliorate neuronal excitability in analogy to histological data. Functional recovery of locomotor networks perhaps required longer time due to the combined action of excitotoxicity and anaesthetic depression at 24 h. These results suggest propofol could confer good neuroprotection to spinal circuits during experimental SCI.

Cell Transplantation and Neuroengineering Approach for Spinal Cord Injury Treatment: A Summary of Current Laboratory Findings and Review of Literature

Spinal cord injury (SCI) can cause severe traumatic injury to the central nervous system (CNS). Current therapeutic effects achieved for SCI in clinical medicine show that there is still a long way to go to reach the desired goal of full or significant functional recovery. In basic medical research, however, cell transplantation, gene therapy, application of cytokines, and biomaterial scaffolds have been widely used and investigated as treatments for SCI. All of these strategies when used separately would help rebuild, to some extent, the neural circuits in the lesion area of the spinal cord. In light of this, it is generally accepted that a combined treatment may be a more effective strategy. This review focuses primarily on our recent series of work on transplantation of Schwann cells and adult stem cells, and transplantation of stem cell-derived neural network scaffolds with functional synapses. Arising from this, an artificial neural network (an exogenous neuronal relay) has been designed and fabricated by us—a biomaterial scaffold implanted with Schwann cells modified by the neurotrophin-3 (NT-3) gene and adult stem cells modified with the TrkC (receptor of NT-3) gene. More importantly, experimental evidence suggests that the novel artificial network can integrate with the host tissue and serve as an exogenous neuronal relay for signal transfer and functional improvement of SCI.

Novel Method for Neuronal Nanosurgical Connection

Neuronal injury may cause an irreversible damage to cellular, organ and organism function. While preventing neural injury is ideal, it is not always possible. There are multiple etiologies for neuronal injury including trauma, infection, inflammation, immune mediated disorders, toxins and hereditary conditions. We describe a novel laser application, utilizing femtosecond laser pulses, in order to connect neuronal axon to neuronal soma. We were able to maintain cellular viability, and demonstrate that this technique is universal as it is applicable to multiple cell types and media.

The change tendency of PI3K/Akt pathway after spinal cord injury

Spinal cord injury (SCI) refers to the damage of spinal cord's structure and function due to a variety of causes. At present, many scholars have confirmed that apoptosis is the main method of secondary injury in spinal cord injury. In view of understanding the function of PI3K/Akt pathway on spinal cord injury, this study observed the temporal variation of key molecules (PI3K, Akt, p-Akt) in the PI3K/Akt pathway after spinal cord injury by immunohistochemistry and Western-blot. The results showed that the expression of PI3K, Akt and p-Akt display a sharp increase one day after the spinal cord injury, and then it decreased gradually with the time passing by, but the absolute expression was certainly higher than the normal group. These results indicate that the PI3K/Akt signaling pathway is involved in the spinal cord injury and the mechanism may be related to apoptosis.

Neurogenesis and growth factors expression after complete spinal cord transection in Pleurodeles waltlii

Following spinal lesion, connections between the supra-spinal centers and spinal neuronal networks can be disturbed, which causes the deterioration or even the complete absence of sublesional locomotor activity. In mammals, possibilities of locomotion restoration are much reduced since descending tracts either have very poor regenerative ability or do not regenerate at all. However, in lower vertebrates, there is spontaneous locomotion recuperation after complete spinal cord transection at the mid-trunk level. This phenomenon depends on a translesional descending axon re-growth originating from the brainstem. On the other hand, cellular and molecular mechanisms underlying spinal cord regeneration and in parallel, locomotion restoration of the animal, are not well known. Fibroblast growth factor 2 (FGF-2) plays an important role in different processes such as neural induction, neuronal progenitor proliferation and their differentiation. Studies had shown an over expression of this growth factor after tail amputation. Nestin, a protein specific for intermediate filaments, is considered an early marker for neuronal precursors. It has been recently shown that its expression increases after tail transection in urodeles. Using this marker and western blots, our results show that the number of FGF-2 and FGFR2 mRNAs increases and is correlated with an increase in neurogenesis especially in the central canal lining cells immediately after lesion. This study also confirms that spinal cord re-growth through the lesion site initially follows a rostrocaudal direction. In addition to its role known in neuronal differentiation, FGF-2 could be implicated in the differentiation of ependymal cells into neuronal progenitors.

Survival of neural stem cell grafts in the lesioned spinal cord is enhanced by a combination of treadmill locomotor training via insulin-like growth factor-1 signaling

Combining cell transplantation with activity-based rehabilitation is a promising therapeutic approach for spinal cord repair. The present study was designed to investigate potential interactions between the transplantation (TP) of neural stem cells (NSCs) obtained at embryonic day 14 and treadmill training (TMT) in promoting locomotor recovery and structural repair in rat contusive injury model. Combination of TMT with NSC TP at 1 week after injury synergistically improved locomotor function. We report here that combining TMT increased the survival of grafted NSCs by >3-fold and >5-fold at 3 and 9 weeks after injury, respectively. The number of surviving NSCs was significantly correlated with the extent of locomotor recovery. NSCs grafted into the injured spinal cord were under cellular stresses induced by reactive nitrogen or oxygen species, which were markedly attenuated by TMT. TMT increased the concentration of insulin-like growth factor-1 (IGF-1) in the CSF. Intrathecal infusion of neutralizing IGF-1 antibodies, but not antibodies against either BDNF or Neurotrophin-3 (NT-3), abolished the enhanced survival of NSC grafts by TMT. The combination of TP and TMT also resulted in tissue sparing, increased myelination, and restoration of serotonergic fiber innervation to the lumbar spinal cord to a larger extent than that induced by either TP or TMT alone. Therefore, we have discovered unanticipated beneficial effects of TMT in modulating the survival of grafted NSCs via IGF-1. Our study identifies a novel neurobiological basis for complementing NSC-based spinal cord repair with activity-based neurorehabilitative approaches.

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

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

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.

Chordin-like protein 1 promotes neuronal differentiation by inhibiting bone morphogenetic protein-4 in neural stem cells

In the present study, the effects of chordin‑like protein 1 (CHRDL1) overexpression, together with bone morphogenetic protein‑4 (BMP‑4) treatment, on the differentiation of rat spinal cord‑derived neural stem cells (NSCs) was investigated. Adult rat spinal cord‑derived NSCs were cultured in serum‑free medium. The recombined eukaryotic expression vector pSecTag2/Hygro B‑CHRDL1 was transfected into adult rat spinal cord‑derived NSCs using a lipid‑based transfection reagent and protein expression was assessed by western blot analysis. Differentiation of transfected NSCs following BMP‑4 treatment was determined by immunocytochemistry. The percentage of microtubule‑associated protein‑2 (MAP‑2)‑positive cells in the BMP‑4‑treated (B) group was found to be significantly lower compared with that in the non‑transfected control (N) group. The percentage of MAP‑2‑positive cells in the pSecTag2/Hygro B‑CHRDL1‑transfected, BMP‑4‑treated group was identified to be significantly higher compared with that in group B, however, no significant difference was observed between group N and the transfected, non‑BMP‑4‑treated control group. The current study indicates that CHRDL1 protein antagonizes BMP‑4 activity and induces spinal cord‑derived NSCs to differentiate into neurons.

Neurient: an algorithm for automatic tracing of confluent neuronal images to determine alignment

A goal of neural tissue engineering is the development and evaluation of materials that guide neuronal growth and alignment. However, the methods available to quantitatively evaluate the response of neurons to guidance materials are limited and/or expensive, and may require manual tracing to be performed by the researcher. We have developed an open source, automated Matlab-based algorithm, building on previously published methods, to trace and quantify alignment of fluorescent images of neurons in culture. The algorithm is divided into three phases, including computation of a lookup table which contains directional information for each image, location of a set of seed points which may lie along neurite centerlines, and tracing neurites starting with each seed point and indexing into the lookup table. This method was used to obtain quantitative alignment data for complex images of densely cultured neurons. Complete automation of tracing allows for unsupervised processing of large numbers of images. Following image processing with our algorithm, available metrics to quantify neurite alignment include angular histograms, percent of neurite segments in a given direction, and mean neurite angle. The alignment information obtained from traced images can be used to compare the response of neurons to a range of conditions. This tracing algorithm is freely available to the scientific community under the name Neurient, and its implementation in Matlab allows a wide range of researchers to use a standardized, open source method to quantitatively evaluate the alignment of dense neuronal cultures.

Herpes simplex virus vector-mediated expression of interleukin-10 reduces below-level central neuropathic pain after spinal cord injury

BACKGROUND

Neuroimmune activation in the spinal dorsal horn plays an important role in the pathogenesis of chronic pain after peripheral nerve injury.

OBJECTIVE

The aim of this study was to examine the role of neuroimmune activation in below-level neuropathic pain after traumatic spinal cord injury (SCI).

METHODS

Right hemilateral SCI was created in male Sprague-Dawley rats by controlled blunt impact through a T12 laminectomy. Pain-related behaviors were assessed using both evoked reflex responses and an operant conflict-avoidance test. Neuroimmune activation was blocked by the anti-inflammatory cytokine interleukin-10 (IL-10) delivered by a nonreplicating herpes simplex virus (HSV)-based gene transfer vector (vIL10). Markers of neuroimmune activation were assessed using immunohistochemistry and Western blot.

RESULTS

One week after SCI, injured animals demonstrated mechanical allodynia, thermal hyperalgesia, and mechanical hyperalgesia in the hind limbs below the level of injury. Animals inoculated with vIL10 had a statistically significant reduction in all of these measures compared to injured rats or injured rats inoculated with control vector. Conflict-avoidance behavior of injured rats inoculated with vIL10 was consistent with significantly reduced pain compared with injured rats injected with control vector. These behavioral results correlated with a significant decrease in spinal tumor necrosis factor α (mTNFα) expression assessed by Western blot and astrocyte activation assessed by glial fibrillary acidic protein immunohistochemistry.

CONCLUSION

Below-level pain after SCI is characterized by neuroimmune activation (increase mTNFα and astrocyte activation). Blunting of the neuroimmune response by HSV-mediated delivery of IL-10 reduced pain-related behaviors, and may represent a potential novel therapeutic agent.

Human umbilical cord blood-derived mesenchymal stem cell therapy promotes functional recovery of contused rat spinal cord through enhancement of endogenous cell proliferation and oligogenesis

Numerous studies have shown the benefits of mesenchymal stem cells (MSCs) on the repair of spinal cord injury (SCI) model and on behavioral improvement, but the underlying mechanisms remain unclear. In this study, to investigate possible mechanisms by which MSCs contribute to the alleviation of neurologic deficits, we examined the potential effect of human umbilical cord blood-derived MSCs (hUCB-MSCs) on the endogenous cell proliferation and oligogenesis after SCI. SCI was injured by contusion using a weight-drop impactor and hUCB-MSCs were transplanted into the boundary zone of the injured site. Animals received a daily injection of bromodeoxyuridine (BrdU) for 7 days after treatment to identity newly synthesized cells of ependymal and periependymal cells that immunohistochemically resembled stem/progenitor cells was evident. Behavior analysis revealed that locomotor functions of hUCB-MSCs group were restored significantly and the cavity volume was smaller in the MSCs-transplanted rats compared to the control group. In MSCs-transplanted group, TUNEL-positive cells were decreased and BrdU-positive cells were significantly increased rats compared with control group. In addition, more of BrdU-positive cells expressed neural stem/progenitor cell nestin and oligo-lineage cell such as NG2, CNPase, MBP and glial fibrillary acidic protein typical of astrocytes in the MSC-transplanted rats. Thus, endogenous cell proliferation and oligogenesis contribute to MSC-promoted functional recovery following SCI.

Spinal cord injury and its treatment: current management and experimental perspectives

Clinical management of spinal cord injury (SCI) has significantly improved its general prognosis. However, to date, traumatic paraplegia and tetraplegia remain incurable, despite massive research efforts. Current management focuses on surgical stabilisation of the spine, intensive neurological rehabilitation, and the prevention and treatment of acute and chronic complications. Prevention remains the most efficient strategy and should be the main focus of public health efforts. Nevertheless, major advances in the understanding of the pathophysiological mechanisms of SCI open promising new therapeutic perspectives. Even if complete recovery remains elusive due to the complexity of spinal cord repair, a strategy combining different approaches may result in some degree of neurological improvement after SCI. Even slight neurological recovery can have high impact on the daily functioning of severely handicapped patients and, thus, result in significant improvements in quality of life.The main investigated strategies are: [1] initial neuroprotection, in order to decrease secondary injury to the spinal cord parenchyma after the initial insult; [2] spinal cord repair, in order to bridge the lesion site and reestablish the connection between the supraspinal centres and the deafferented cord segment below the lesion; and [3] re-training and enhancing plasticity of the central nervous system circuitry that was preserved or rebuilt after the injury.Now and in the future, treatment strategies that have both a convincing rationale and seen their efficacy confirmed reproducibly in the experimental setting must carefully be brought from bench to bedside. In order to obtain clinically significant results, their introduction into clinical research must be guided by scientific rigour, and their coordination must be rationally structured in a long-term perspective.

The longitudinal spinal cord injury: lessons from intraspinal plexus, cauda equina and medullary conus lesions

Spinal nerve root avulsion injury interrupts the transverse segmental spinal cord nerve fibers. There is degeneration of sensory, motor, and autonomic axons, loss of synapses, deterioration of local segmental connections, nerve cell death, and reactions among non neuronal cells with central nerve system (CNS) scar formation, i.e., a cascade of events similar to those known to occur in any injury to the spinal cord. This is the longitudinal spinal cord injury (SCI). For function to be restored, nerve cells must survive and there must be regrowth of new nerve fibers along a trajectory consisting of CNS growth-inhibitory tissue in the spinal cord as well as peripheral nervous system (PNS) growth-promoting tissue in nerves. Basic science results have been translated into a successful surgical strategy to treat root avulsion injuries in man. In humans, this technique is currently the most promising treatment of any spinal cord injury, with return of useful muscle function together with pain alleviation. Experimental studies have also identified potential candidates for adjunctive therapies that, together with surgical replantation of avulsed roots after brachial plexus and cauda equina injuries, can restore not only motor but also autonomic and sensory trajectories to augment the recovery of neurological function. This is the first example of a spinal cord lesion that can be treated surgically, leading to restoration of somatic and autonomic activity and alleviation of pain.

Studies of locomotor network neuroprotection by the selective poly(ADP-ribose) polymerase-1 inhibitor PJ-34 against excitotoxic injury to the rat spinal cord in vitro

Delayed neuronal destruction after acute spinal injury is attributed to excitotoxicity mediated by hyperactivation of poly(ADP-ribose) polymerase-1 (PARP-1) that induces 'parthanatos', namely a non-apoptotic cell death mechanism. With an in vitro model of excitotoxicity, we have previously observed parthanatos of rat spinal cord locomotor networks to be decreased by a broad spectrum PARP-1 inhibitor. The present study investigated whether the selective PARP-1 inhibitor N-(6-oxo-5,6-dihydrophenanthridin-2-yl)-(N,N-dimethylamino)acetamide.HCl (PJ-34) not only protected networks from kainate-evoked excitotoxicity, but also prevented loss of locomotor patterns recorded as fictive locomotion from lumbar (L) ventral roots (VRs) 24 h later. PJ-34 (60 μm) blocked PARP-1 activation and preserved dorsal, central and ventral gray matter with maintained reflex activity even after a large dose of kainate. Fictive locomotion could not, however, be restored by either electrical stimulation or bath-applied neurochemicals (N-methyl-D-aspartate plus 5-hydroxytryptamine). A low kainate concentration induced less histological damage that was widely prevented by PJ-34. Nonetheless, fictive locomotion was observed in just over 50% of preparations whose histological profile did not differ (except for the dorsal horn) from those lacking such a rhythm. Our data show that inhibition of PARP-1 could amply preserve spinal network histology after excitotoxicity, with return of locomotor patterns only when the excitotoxic stimulus was moderate. These results demonstrated divergence between histological and functional outcome, implying a narrow borderline between loss of fictive locomotion and neuronal preservation. Our data suggest that either damage of a few unidentified neurons or functional network inhibition was critical for ensuring locomotor cycles.

Anti-Nogo-A and training: can one plus one equal three?

Following spinal cord injury (SCI) the adult central nervous system (CNS) has a limited but substantial capacity for repair and plastic reorganisation. The degree of reorganisation is determined by a number of factors such as the extent and location of the lesion, the remaining circuit activity within the CNS and the age at injury. However, even in the best cases this spontaneous reorganisation does not lead to full recovery of the affected behaviour but instead often results in a functionally successful but compensatory strategy. Current SCI research focuses on enhancing fibre tract (re-)growth and recovery processes. Two currently promising approaches are the neutralisation of CNS growth inhibitory factors, and rehabilitative training of remaining networks. Independently, both approaches can lead to substantial functional recovery and anatomical reorganisation. In this review we focus on Nogo-A, a neurite growth inhibitory protein present in the adult CNS, and its role in regenerative and plastic growth following SCI. We then discuss the efforts of rehabilitative training and the potential combination of the two therapies.

What can the spinal cord teach us about learning and memory?

The work of recent decades has shown that the nervous system changes continually throughout life. Activity-dependent central nervous system (CNS) plasticity has many different mechanisms and involves essentially every region, from the cortex to the spinal cord. This new knowledge radically changes the challenge of explaining learning and memory and greatly increases the relevance of the spinal cord. The challenge is now to explain how continual and ubiquitous plasticity accounts for the initial acquisition and subsequent stability of many different learned behaviors. The spinal cord has a key role because it is the final common pathway for all behavior and is a site of substantial plasticity. Furthermore, because it is simple, accessible, distant from the rest of the CNS, and directly connected to behavior, the spinal cord is uniquely suited for identifying sites and mechanisms of plasticity and for determining how they account for behavioral change. Experimental models based on spinal cord reflexes facilitate study of the gradual plasticity that makes possible most rapid learning phenomena. These models reveal principles and generate concepts that are likely to apply to learning and memory throughout the CNS. In addition, they offer new approaches to guiding activity-dependent plasticity so as to restore functions lost to injury or disease.

Toward a whole-body neuroprosthetic

Brain-machine interfaces (BMIs) hold promise for the restoration of body mobility in patients suffering from devastating motor deficits caused by brain injury, neurological diseases, and limb loss. Considerable progress has been achieved in BMIs that enact arm movements, and initial work has been done on BMIs for lower limb and trunk control. These developments put Duke University Center for Neuroengineering in the position to develop the first BMI for whole-body control. This whole-body BMI will incorporate very large-scale brain recordings, advanced decoding algorithms, artificial sensory feedback based on electrical stimulation of somatosensory areas, virtual environment representations, and a whole-body exoskeleton. This system will be first tested in nonhuman primates and then transferred to clinical trials in humans.

Future developments in brain-machine interface research

Neuroprosthetic devices based on brain-machine interface technology hold promise for the restoration of body mobility in patients suffering from devastating motor deficits caused by brain injury, neurologic diseases and limb loss. During the last decade, considerable progress has been achieved in this multidisciplinary research, mainly in the brain-machine interface that enacts upper-limb functionality. However, a considerable number of problems need to be resolved before fully functional limb neuroprostheses can be built. To move towards developing neuroprosthetic devices for humans, brain-machine interface research has to address a number of issues related to improving the quality of neuronal recordings, achieving stable, long-term performance, and extending the brain-machine interface approach to a broad range of motor and sensory functions. Here, we review the future steps that are part of the strategic plan of the Duke University Center for Neuroengineering, and its partners, the Brazilian National Institute of Brain-Machine Interfaces and the École Polytechnique Fédérale de Lausanne (EPFL) Center for Neuroprosthetics, to bring this new technology to clinical fruition.

Acute adaptive responses of central sensorimotor neurons after spinal cord injury

Spinal cord injury (SCI) can be a lifelong, devastating condition for both the patient and the caregiver, with a daunting incidence rate. Still, there are only limited available therapies and the effectiveness of precise regeneration within the central nervous system is minimal throughout postnatal life. Recently, improved regeneration after SCI was seen by manipulating a pathway in sensorimotor neocortices that is involved in phosphorylation of an RNA binding protein (RBP) required for mRNA translation, the Eukaryotic translation initiation factor 4E (eIF4E). Our data identifies rapid molecular alterations of eIF4E in the sensorimotor neocortices 1 and 3 days after a lateral hemisection SCI, used as a model for Brown-Séquard syndrome. The function of an RBP depends on both its distribution sites within the cell and its phosphorylation states. Indeed, we found both to be affected after SCI. There was a distinct subcellular redistribution of eIF4E and phosphorylated-eIF4E was reduced, indicating that the eIF4E’s translation was disrupted. Upon identification and analysis of the mRNA cargo of eIF4E in uninjured sensorimotor neocortices, we found that eIF4E binds both Importin-13 (Ipo13) and Parvalbumin (Pv) mRNAs, indicating a role in their translation. Remarkably, eIF4E’s interaction with both Ipo13 and Pv mRNAs was disrupted 1 and 3 days after SCI, despite preservation of total Ipo13 and Pv mRNA levels. Finally, we detected a selective loss of expression of both IPO13 and PV proteins in projection neurons of sensorimotor neocortices, as well as their disrupted dendritic polarity. Since IPO13 is predominantly expressed in neocortical projection neurons and PV in a subset of neocortical interneurons, these data suggest a strong acute effect of SCI on neocortical microcircuitry. Taken together, these data indicate that neocortical eIF4E and a subset of mRNAs may be rapidly recruited to translational machinery after SCI to promote adaptive regeneration response of sensorimotor neurons.

L1 cell adhesion molecule is essential for the maintenance of hyperalgesia after spinal cord injury

Spinal cord injury (SCI) results in a loss of normal motor and sensory function, leading to severe disability and reduced quality of life. A large proportion of individuals with SCI also suffer from neuropathic pain symptoms. The causes of abnormal pain sensations are not well understood, but can include aberrant sprouting and reorganization of injured or spared sensory afferent fibers. L1 is a cell adhesion molecule that contributes to axonal outgrowth, guidance and fasciculation in development as well as synapse formation and plasticity throughout life. In the present study, we used L1 knockout (KO) mice to determine whether this adhesion molecule contributes to sensory dysfunction after SCI. Both wild-type (WT) and KO mice developed heat hyperalgesia following contusion injury, but the KO mice recovered normal response latencies beginning at 4 weeks post-injury. Histological analyses confirmed increased sprouting of sensory fibers containing calcitonin-gene related peptide (CGRP) in the deep dorsal horn of the lumbar spinal cord and increased numbers of interneurons expressing protein kinase C gamma (PKCgamma) in WT mice 6 weeks after injury. In contrast, L1 KO mice had less CGRP(+) fiber sprouting, but even greater numbers of PKCgamma(+) interneurons at the 6 week time point. These data demonstrate that L1 plays a role in maintenance of thermal hyperalgesia after SCI in mice, and implicate CGRP(+) fiber sprouting and the upregulation of PKCgamma expression as potential contributors to this response.

Kainate and metabolic perturbation mimicking spinal injury differentially contribute to early damage of locomotor networks in the in vitro neonatal rat spinal cord

Acute spinal cord injury evolves rapidly to produce secondary damage even to initially spared areas. The result is loss of locomotion, rarely reversible in man. It is, therefore, important to understand the early pathophysiological processes which affect spinal locomotor networks. Regardless of their etiology, spinal lesions are believed to include combinatorial effects of excitotoxicity and severe stroke-like metabolic perturbations. To clarify the relative contribution by excitotoxicity and toxic metabolites to dysfunction of locomotor networks, spinal reflexes and intrinsic network rhythmicity, we used, as a model, the in vitro thoraco-lumbar spinal cord of the neonatal rat treated (1 h) with either kainate or a pathological medium (containing free radicals and hypoxic/aglycemic conditions), or their combination. After washout, electrophysiological responses were monitored for 24 h and cell damage analyzed histologically. Kainate suppressed fictive locomotion irreversibly, while it reversibly blocked neuronal excitability and intrinsic bursting induced by synaptic inhibition block. This result was associated with significant neuronal loss around the central canal. Combining kainate with the pathological medium evoked extensive, irreversible damage to the spinal cord. The pathological medium alone slowed down fictive locomotion and intrinsic bursting: these oscillatory patterns remained throughout without regaining their control properties. This phenomenon was associated with polysynaptic reflex depression and preferential damage to glial cells, while neurons were comparatively spared. Our model suggests distinct roles of excitotoxicity and metabolic dysfunction in the acute damage of locomotor networks, indicating that different strategies might be necessary to treat the various early components of acute spinal cord lesion.

Modulation of dendritic spine remodeling in the motor cortex following spinal cord injury: effects of environmental enrichment and combinatorial treatment with transplants and neurotrophin-3

Incomplete spinal cord injury (SCI) elicits structural plasticity of the spared motor system, including the motor cortex, which may underlie some of the spontaneous recovery of motor function seen after injury. Promoting structural plasticity may become an important component of future strategies to improve functional outcomes. We have recently observed dynamic changes in the density and morphology of dendritic spines in the motor cortex following SCI. The present study sought to test whether SCI-induced changes in spine density and morphology could be modulated by potential strategies to enhance functional recovery. We examined the effects of enriched environment, transplants, and neurotrophin-3 on the plasticity of synaptic structures in the motor cortex following SCI. Housing rats in an enriched environment increased spine density in the motor cortex regardless of injury. SCI led to a more slender and elongated spine morphology. Enriched housing mitigated the SCI-induced morphological alterations, suggesting that the environmental modification facilitates maturation of synaptic structures. Transplantation of embryonic spinal cord tissue and delivery of neurotrophin-3 at the injury site further increased spine density when combined with enriched housing. This combinatorial treatment completely abolished the injury-induced changes, restoring a preinjury pattern of spine morphology. These results demonstrated that remodeling of dendritic spines in the motor cortex after SCI can be modulated by enriched housing, and the combinatorial treatment with embryonic transplants and neurotrophin-3 can potentiate the effects of enriched housing. We suggest that synaptic remodeling processes in the motor cortex can be targeted for an intervention to enhance functional recovery after SCI.

Brain-computer interface systems: progress and prospects

Brain-computer interface (BCI) systems support communication through direct measures of neural activity without muscle activity. BCIs may provide the best and sometimes the only communication option for users disabled by the most severe neuromuscular disorders and may eventually become useful to less severely disabled and/or healthy individuals across a wide range of applications. This review discusses the structure and functions of BCI systems, clarifies terminology and addresses practical applications. Progress and opportunities in the field are also identified and explicated.