A systematic review of exercise training to promote locomotor recovery in animal models of spinal cord injury

The effect of early mobilisation (< 14 days) on pathophysiological and functional outcomes in animals with induced spinal cord injury: a systematic review with meta-analysis

INTRODUCTION

The optimum time to mobilise (standing, walking) following spinal cord injury (SCI) is unknown but may have implications for patient outcomes. There are no high-quality experimental studies that examine this issue, with a paucity of guidance for clinicians. Pre-clinical studies lead research in this field and can contribute to knowledge and support future clinical practice.

OBJECTIVE

to evaluate the effect of early compared to no mobilisation on pathophysiological and functional outcomes in animals with induced SCI.

METHODS

A systematic review with meta-analysis was conducted by searching pre-clinical literature in MEDLINE (PubMed), Embase (Ovid), Web of Science, OpenGrey, and EThOS (June 2023). Studies were included of any research method giving numerical results comparing pathophysiological and functional outcomes in rats and mice mobilised within 14-days of induced SCI to those that did not mobilise. Data were synthesised using random-effects meta-analyses. The quality of the evidence was assessed using the CAMARADES checklist. The certainty of findings was reported using the GRADE approach. This study is registered on PROSPERO (CRD42023437494).

RESULTS

Seventeen studies met the inclusion criteria. Outcomes found that Brain Derived Neurotrophic Factor levels were greater in those that initiated mobilisation within 14-days of SCI compared to the groups that did not. Mobilisation initiated within 14-days of SCI was also associated with statistically significant functional gains: (Basso, Beattie and Bresnahan locomotor rating score (BBB) = 2.13(0-21), CI 1.43, 2.84, Ladder Rung Walking Task = - 12.38(0-100), CI 20.01, - 4.76). Meta-analysis identified the greatest functional gains when mobilisation was initiated within 3 days of SCI (BBB = 3.00, CI 2.31-3.69, p < 0.001), or when delivered at low intensity (BBB = 2.88, CI 2.03-3.70, p < 0.001). Confidence in the findings from this review was low to moderate due to the risk of bias and mixed methodological quality.

CONCLUSION

Mobilisation instigated within 14-days of injury, may be an effective way of improving functional outcomes in animal models following SCI, with delays potentially detrimental to recovery. Outcomes from this study support further research in this field to guide future clinical practice.

Body Weight Support Treadmill Training Combined With Sciatic Nerve Electrical Stimulation Ameliorating Motor Function by Enhancing PI3K/Akt Proteins Expression via BDNF/TrkB Signaling Pathway in Rats with Spinal Cord Injury

OBJECTIVE

To investigate the effects of body weight support treadmill training (BWSTT) and sciatic nerve electrical stimulation (SNES) on motor function recovery in spinal cord injury (SCI) rats and its possible mechanism.

METHODS

Modified Allen's method was utilized for T10 incomplete SCI. The Basso-Beattie-Bresnahan (BBB) score and modified Tarlov score were applied to assess motor function. Pathologic alterations of the spinal cord and muscles were observed by hematoxylin and eosin (HE) staining. The positive staining region of collagen fibers was assessed with Masson staining. Immunofluorescence was applied to count the positive cells of brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB). BDNF, TrkB, phosphatidylinositol-3-kinase (PI3K), and protein kinase B (Akt) relative mRNA and protein expressions were evaluated by reverse transcription polymerase chain reaction (RT-PCR) and Western blotting.

RESULTS

On the 21st day of the intervention, the motor scores in SNES and BWSTT + SNES groups were higher than that in SCI group (P < 0.05). Compared with SCI group, mRNA and protein expressions of BDNF/TrkB and PI3K/Akt were more significant on the 21st day of the intervention in SNES and BWSTT + SNES groups (P < 0.05), but there was no difference in BWSTT group (P > 0.05).

CONCLUSIONS

This experiment demonstrated that BWSTT combined with SNES contributed to alleviating spinal cord tissue injury, delaying muscle atrophy and improving locomotion. One of the possible mechanisms may be related to the regulation of the BDNF/TrkB signaling pathway, which changes the expression of PI3K/Akt protein. Furthermore, it was discovered that the ultra-early BWSTT may not be conducive to recovery.

Early-phase rotator training impairs tissue repair and functional recovery after spinal cord injury

Spinal cord injury (SCI) is a devastating disorder that often results in severe sensorimotor function impairment with limited recovery of function. In recent years, rehabilitation training for spinal cord injury has gradually emerged, and some of them play an important role in the repair of spinal cord injury However, the optimal training regimen for SCI remains to be determined. In this study, we explore the effects of rotarod training (began at 7 days post-injury) on the recovery of motor function after SCI, as well as its possible repair mechanism from the aspects of function and histopathological changes, the behaviors of specific trophic factors and cytokines, and the expression profile of specific genes. Multiple functional assessments showed that rotarod training initiated at 7 days post-injury is unsuitable for promoting neuro-electrophysiological improvement and trunk stability, but impaired functional coordination and motor recovery. In addition, rotarod training has negative effects on spinal cord repair after SCI, which is manifested as an increase of lesion area, a decrease in neuronal viability, a deterioration in immuno-microenvironment and remyelination, a significant reduction in the expression of trophic factors and an increase in the expression of pro-inflammatory factors. RNA sequencing suggested that the genes associated with angiogenesis and synaptogenesis were significantly downregulated and the PI3K-AKT pathway was inhibited, which was detrimental to spinal cord repair and impeded nerve regeneration. These results indicate that immediate rotarod training after SCI is currently unsuitable for rehabilitation in mice.

A Review of Treatment Methods Focusing on Human Induced Pluripotent Stem Cell-Derived Neural Stem/Progenitor Cell Transplantation for Chronic Spinal Cord Injury

Cell transplantation therapy using human induced pluripotent stem cell-derived neural stem/progenitor cells (hiPSC-NS/PCs) has attracted attention as a regenerative therapy for spinal cord injury (SCI), and its efficacy in treating the subacute phase of SCI has been reported in numerous studies. However, few studies have focused on treatment in the chronic phase, which accounts for many patients, suggesting that there are factors that are difficult to overcome in the treatment of chronic SCI. The search for therapeutic strategies that focus on chronic SCI is fraught with challenges, and the combination of different therapies is thought to be the key to a solution. In addition, many issues remain to be addressed, including the investigation of therapeutic approaches for more severe injury models of chronic SCI and the acquisition of practical motor function. This review summarizes the current progress in regenerative therapy for SCI and discusses the prospects for regenerative medicine, particularly in animal models of chronic SCI.

Construction of a searchable database for gene expression changes in spinal cord injury experiments

Spinal cord injury (SCI) is a debilitating disease resulting in an estimated 18,000 new cases in the United States on an annual basis. Significant behavioral research on animal models has led to a large amount of data, some of which has been catalogued in the Open Data Commons for Spinal Cord Injury (ODC-SCI). More recently, high throughput sequencing experiments have been utilized to understand molecular mechanisms associated with SCI, with nearly 6,000 samples from over 90 studies available in the Sequence Read Archive. However, to date, no resource is available for efficiently mining high throughput sequencing data from SCI experiments. Therefore, we have developed a protocol for processing RNA-Seq samples from high-throughput sequencing experiments related to SCI resulting in both raw and normalized data that can be efficiently mined for comparisons across studies as well as homologous discovery across species. We have processed 1,196 publicly available RNA-seq samples from 50 bulk RNA-Seq studies across nine different species, resulting in an SQLite database that can be used by the SCI research community for further discovery. We provide both the database as well as a web-based front-end that can be used to query the database for genes of interest, differential gene expression, genes with high variance, and gene set enrichments.

Motor rehabilitation as a therapeutic tool for spinal cord injury: New perspectives in immunomodulation

Traumatic spinal cord injury (SCI) is a devastating condition that significantly impacts motor, sensory and autonomic function in patients. Despite advances in therapeutic approaches, there is still no curative therapy currently available. Neuroinflammation is a persisting event of the secondary injury phase of SCI that affects functional recovery, and modulation of the inflammatory response towards a beneficial anti-inflammatory state can improve recovery in preclinical SCI models. In human SCI patients, rehabilitative exercise, or motor rehabilitation as we will refer to it from here on out, remains the cornerstone of treatment to increase functional capacity and prevent secondary health implications. Motor rehabilitation is known to have anti-inflammatory effects; however, current literature is lacking in the description of the effect of motor rehabilitation on inflammation in the context of SCI. Understanding the effect on different inflammatory markers after SCI should enable the optimization of motor rehabilitation as a therapeutic regime. This review extensively describes the effect of motor rehabilitation on selected inflammatory mediators in both preclinical and human SCI studies. Additionally, we summarize how the type, duration, and intensity of motor rehabilitation can affect the inflammatory response after SCI. In doing so, we introduce a new perspective on how motor rehabilitation can be optimized as an immunomodulatory therapy to improve patient outcome after SCI.

Unintentional Effects from Housing Enhancement Resulting in Functional Improvement in Spinal Cord-Injured Mice

It is well established that both positive and negative housing conditions of laboratory animals can affect behavioral, biochemical, and physiological responses. Housing enhancements have been shown to have beneficial effects on locomotor outcomes in rodents with spinal cord injury (SCI). Subsequent to an unplanned housing enhancement of the addition of a balcony to home cages by animal care personnel at a research facility, a retrospective analysis of multiple SCI studies was performed to determine whether outcomes differed before (four studies, N = 28) and after (four studies, N = 23) the addition of the balcony. Locomotor and morphological differences were compared after a mild-moderate T9 spinal cord contusion injury in wild-type mice. Post-injury assessments of locomotor function for 6 weeks included Basso Mouse Scale (BMS) and treadmill kinematic assessments (week 6). Balcony-housed mice showed greater improvements not only in basic locomotor functions (weight-supported stepping, balance) compared to those in standard housing, but also surpassed mice in standard housing without the balcony in higher-order locomotor recovery outcomes, including BMS late-stage recovery measures (paw, tail, and trunk indices). Additionally, balcony-housed mice had overall higher BMS scores, consistently attained more BMS subscores, and had better treadmill track width and stride length compared to those with no balcony. The housing enhancement of a balcony led to unforeseen consequences and unexpected higher recovery outcomes compared to mice in standard housing. This retrospective study highlights the importance of housing conditions in the key outcomes of locomotor recovery after incomplete contusive SCIs in mice.

Mechanism of skeletal muscle atrophy after spinal cord injury: A narrative review

Spinal cord injury leads to loss of innervation of skeletal muscle, decreased motor function, and significantly reduced load on skeletal muscle, resulting in atrophy. Factors such as braking, hormone level fluctuation, inflammation, and oxidative stress damage accelerate skeletal muscle atrophy. The atrophy process can result in skeletal muscle cell apoptosis, protein degradation, fat deposition, and other pathophysiological changes. Skeletal muscle atrophy not only hinders the recovery of motor function but is also closely related to many systemic dysfunctions, affecting the prognosis of patients with spinal cord injury. Extensive research on the mechanism of skeletal muscle atrophy and intervention at the molecular level has shown that inflammation and oxidative stress injury are the main mechanisms of skeletal muscle atrophy after spinal cord injury and that multiple pathways are involved. These may become targets of future clinical intervention. However, most of the experimental studies are still at the basic research stage and still have some limitations in clinical application, and most of the clinical treatments are focused on rehabilitation training, so how to develop more efficient interventions in clinical treatment still needs to be further explored. Therefore, this review focuses mainly on the mechanisms of skeletal muscle atrophy after spinal cord injury and summarizes the cytokines and signaling pathways associated with skeletal muscle atrophy in recent studies, hoping to provide new therapeutic ideas for future clinical work.

Evaluation of a treatment protocol in dogs with intraspinal spirocercosis

OBJECTIVE

To evaluate the efficiency and safety of a doramectin-based treatment protocol in dogs affected by intraspinal spirocercosis (Spirocerca lupi).

ANIMALS

Client-owned dogs that were admitted to a veterinary hospital during 2021 to 2022 with acute onset of neurological signs and diagnosed with intraspinal spirocercosis. All dogs underwent complete neurological evaluation, CSF analysis, PCR confirmation of CNS S lupi infection, and follow-up evaluation of at least 6 months.

PROCEDURES

Upon diagnosis, dogs were treated with doramectin at a dose of 400 μg/kg, SC, q 24 h for 3 consecutive days, followed by the same dose once a week for 6 weeks. Prednisone was administered at a dose of 1 mg/kg, PO, q 24 h and tapered every 3 days. Antimicrobial clindamycin was administered at a dose of 12.5 mg/kg, PO, q 12 h for 7 days to reduce the risk of secondary spinal cord infection. Short- and long-term outcomes (1 week to 56 months) were recorded.

RESULTS

8 dogs fulfilled the inclusion criteria, 7 of which presented with neurological deficits and 1 with cervical pain. Initiation of treatment was associated with stopping the deterioration in 7 of 8 dogs. Seven dogs improved and 6 recovered ambulation. One dog was euthanized due to lack of improvement. Six of the recovered dogs were still ataxic on the last follow-up examination at 6 to 56 months. No adverse effects of the drug were noted.

CLINICAL RELEVANCE

Frequent administration of doramectin was found to be safe and effective in preventing neurological deterioration in dogs with intraspinal spirocercosis.

A Narrative Review of Advances in Neural Precursor Cell Transplantation Therapies for Spinal Cord Injury

A spinal cord injury (SCI) is a destructive event that causes a permanent deficit in neurological function because of poor regenerative potential. Transplantation therapies have attracted attention for restoration of the injured spinal cord, and transplantation of neural precursor cells (NPCs) has been studied worldwide. Several groups have demonstrated functional recovery via this therapeutic intervention due to the multiple beneficial effects of NPC transplantation, such as reconstruction of neuronal circuits, remyelination of axons, and neuroprotection by trophic factors. Our group developed a method to induce NPCs from human induced pluripotent stem cells (hiPSCs) and established a transplantation strategy for SCI. Functional improvement in SCI animals treated with hiPSC-NPCs was observed, and the safety of transplanting these cells was evaluated from multiple perspectives. With selection of a safe cell line and pretreatment of the cells to encourage maturation and differentiation, hiPSC-NPC transplantation therapy is now in the clinical phase of testing for subacute SCI. In addition, a research challenge will be to expand the efficacy of transplantation therapy for chronic SCI. More comprehensive strategies involving combination treatments are required to treat this problematic situation.

Resistance exercise promotes functional test via sciatic nerve regeneration, and muscle atrophy improvement through GAP-43 regulation in animal model of traumatic nerve injuries

Resistance training improves muscle strength through a combination of neural plasticity and muscle hypertrophy. This study aimed to evaluate the effects of resistance exercise on sciatic nerve regeneration and histology, growth-associated protein 43 (GAP-43) expressions, and soleus muscle atrophy following traumatic nerve injuries in Wistar rats. In the present study, 40 male Wistar rats were randomly assigned into four groups: healthy control (HC) as a sham group was exposed to the surgical procedures without any sciatic nerve compression, lesioned control (LC), resistance training (RT,non-lesioned), and lesioned rats+RT (LRT) (n=10 in each). The RT group performed a resistance-training program 5 days/week for 4 weeks. Sciatic functional index (SFI) score, beam score and Basso, Beattie, and Bresnahan (BBB) score decreased and the hot plate time increased significantly in the LC‌ group compared to the HC (p<0.05) group. However, the LRT‌ group showed a significant increase in the SFI score (p=0.001) and a significant decrease in hot plate time (p=0.0232) compared to the LC group. The LC group also showed neurological morphological damage and muscle atrophy and a decrease in GAP-43 in nerve tissue. In comparison to the LC group, a significant increase in sciatic nerve caliber, diameter, number of muscle fibers, and the expression of GAP-43‌ (p<0.05) was observed in the LRT group. Doing resistance training even for four weeks seems to affect sciatic nerve lesions and injuries. It can also repair and regenerate nerve tissue by upregulating GAP-43 expression‌, improving motor behavioral tests, and controlling muscle atrophy.

Bioinformatics analysis of the wheel treadmill test on motor function recovery after spinal cord injury

This study aimed to explore the possible target and mechanism of the wheel treadmill (WTM) test for motor function recovery of spinal cord injury (SCI). Rats were divided into sham, control and WTM groups to establish an SCI mode. Rats in the WTM group were trained on the WTM test, and Basso-Beattie-Bresnahan (BBB) scores were determined. The samples were collected, and mRNA sequencing was conducted to determine the changes in gene expression. The coexpressed genes were screened to construct a protein-protein interaction (PPI), followed by the Kyoto Encyclopedia of Genes and Genomes pathway and Gene Ontology function enrichment analysis, and the differentially expressed genes (DEGs) volcano map and hub gene expression heat map were constructed using R language. The BBB scores in the control and WTM groups increased with time, with the WTM group scoring higher than the control group. The results of rat spinal cord tissue sequencing showed that a total of 1679 DEGs were screened in the sham and control groups; 928 DEGs and 731 overlapping genes were screened in the WTM and control groups. The key genes were identified by PPI analysis. One hundred and thirty-three genes were found to be overlapping by combined analysis of spinal cord sequencing data and BBB scores of rats at Week 7. The top 10 DEGs from high to low were Tyrobp, Rac2, Cd68, C1qb, Aif1, Cd74, Spi1, Fcer1g, RT1-DA, and Ccl4. The terms with the highest enrichment scores were microglia-mediated positive regulation of cytotoxicity and major histocompatibility complex class II protein complexes. Treatment with the WTM test promotes recovery of motor function after SCI in rats by modulating intercellular communication and immune function.

Long-term rehabilitation reduces task error variability in cervical spinal cord contused rats

To promote skilled forelimb function following a spinal cord injury, we have evaluated whether long-term voluntary sensorimotor rehabilitation can promote substantial reaching and grasping recovery. Long-Evans rats were trained to reach single pellets and then received a moderate 100 kdyn contusion to the C5 lateral funiculi. During the first eight months post-injury, a group of animals was enrolled in daily skilled reaching rehabilitation consisting of grabbing and manipulating seeds from the bottom of a grid. Single-pellet reaching and grasping recovery was tested biweekly throughout the functional follow-up and the recovery was compared to a second group of contused but non-rehabilitated animals. Following the injury, reaching and grasping success dropped to zero in both groups and remained absent for three months post-injury, followed by a slight recovery that remained constant until the end of the follow-up. No differences in reaching success were found between groups. Nevertheless, the type of gesture errors in the failed attempts were categorized and scored. The errors ranged from the animal's inability to lift the paw and initiate the movement to the final stage of the attempt, in which the pellet falls during grasping and retraction of the paw towards the mouth. Both groups of animals exhibited similar types of errors but the animals with rehabilitation showed less error variability and those that occurred at the latest stages of the attempt predominated compared to those performed by the non-trained animals. Histological examination of the injury showed that injury severity was similar between groups and that the damage was circumscribed to the site of impact, affecting mainly the dorsal and medial region of the lateral funiculi, with preservation of the dorsal component of the corticospinal tract and the interneurons and motoneurons of the spinal segments beyond the site of injury. The results indicate that activity-dependent plasticity driven by voluntary rehabilitation decreases task error variability and drives the recovery of the movement gestures. However, the plasticity achieved is insufficient to attain full functional recovery to successfully reach, grasp and release the pellets in the mouth, indicating the necessity for additional interventional therapies to promote repair.

A Controlled Clinical Study of Intensive Neurorehabilitation in Post-Surgical Dogs with Severe Acute Intervertebral Disc Extrusion

Simple Summary

This study explores the potential intensive neurorehabilitation plasticity effects in post-surgical paraplegic dogs with severe acute intervertebral disc extrusion aiming to achieve ambulatory status. The intensive neurorehabilitation protocol translated in 99.4% (167/168) of recovery in deep pain perception-positive dogs and 58.5% (55/94) in deep pain perception-negative dogs. There was 37.3% (22/59) spinal reflex locomotion, obtained within a maximum period of 3 months. Thus, intensive neurorehabilitation may be a useful approach for this population of dogs, avoiding future euthanasia and promoting an estimated time window of 3 months to recover.

Abstract

This retrospective controlled clinical study aimed to verify if intensive neurorehabilitation (INR) could improve ambulation faster than spontaneous recovery or conventional physiotherapy and provide a possible therapeutic approach in post-surgical paraplegic deep pain perception-positive (DPP⁺) (with absent/decreased flexor reflex) and DPP-negative (DDP⁻) dogs, with acute intervertebral disc extrusion. A large cohort of T10-L3 Spinal Cord Injury (SCI) dogs (n = 367) were divided into a study group (SG) (n = 262) and a control group (CG) (n = 105). The SG was based on prospective clinical cases, and the CG was created by retrospective medical records. All SG dogs performed an INR protocol by the hospitalization regime based on locomotor training, electrical stimulation, and, for DPP⁻, a combination with pharmacological management. All were monitored throughout the process, and measuring the outcome for DPP⁺ was performed by OFS and, for the DPP⁻, by the new Functional Neurorehabilitation Scale (FNRS-DPP⁻). In the SG, DPP⁺ dogs had an ambulation rate of 99.4% (n = 167) and, in DPP⁻, of 58.5% (n = 55). Moreover, in DPP⁺, there was a strong statistically significant difference between groups regarding ambulation (p < 0.001). The same significant difference was verified in the DPP^– dogs (p = 0.007). Furthermore, a tendency toward a significant statistical difference (p = 0.058) regarding DPP recovery was demonstrated between groups. Of the 59 dogs that did not recover DPP, 22 dogs achieved spinal reflex locomotion (SRL), 37.2% within a maximum of 3 months. The progressive myelomalacia cases were 14.9% (14/94). Therefore, although it is difficult to assess the contribution of INR for recovery, the results suggested that ambulation success may be improved, mainly regarding time.

Functional Neurorehabilitation in Dogs with an Incomplete Recovery 3 Months following Intervertebral Disc Surgery: A Case Series

Simple Summary

A non-invasive neurorehabilitation multimodal protocol (NRMP) may be applicable to chronic T3-L3 dogs 3 months after undergoing surgery for acute Intervertebral Disc Disease (IVDD) Hansen type I; this protocol has been shown to be safe, feasible, and potentially effective at improving ambulation in both open field score (OFS) 0 and OFS 1 dogs. The specific sample population criteria limit the number of dogs included, mainly due to owners withdrawing over time. Thus, the present case series study aimed to demonstrate that an NRMP could contribute to a functional treatment possibly based on synaptic and anatomic reorganization of the spinal cord.

Abstract

This case series study aimed to evaluate the safety, feasibility, and positive outcome of the neurorehabilitation multimodal protocol (NRMP) in 16 chronic post-surgical IVDD Hansen type I dogs, with OFS 0/DPP− (n = 9) and OFS 1/DPP+ (n = 7). All were enrolled in the NRMP for a maximum of 90 days and were clinically discharged after achieving ambulation. The NRMP was based on locomotor training, functional electrical stimulation, transcutaneous electrical spinal cord stimulation, and 4-aminopyridine (4-AP) pharmacological management. In the Deep Pain Perception (DPP)+ dogs, 100% recovered ambulation within a mean period of 47 days, reaching OFS ≥11, which suggests that a longer period of time is needed for recovery. At follow-up, all dogs presented a positive evolution with voluntary micturition. Of the DPP− dogs admitted, all achieved a flexion/extension locomotor pattern within 30 days, and after starting the 4-AP, two dogs were discharged at outcome day 45, with 78% obtaining Spinal Reflex Locomotion (SRL) and automatic micturition within a mean period of 62 days. At follow-up, all dogs maintained their neurological status. After the NRMP, ambulatory status was achieved in 88% (14/16) of dogs, without concurrent events. Thus, an NRMP may be an important therapeutic option to reduce the need for euthanasia in the clinical setting.

Sigma 1 receptor agonist cutamesine promotes plasticity of serotonergic boutons in lumbar enlargement in spinal cord injured rats

Cutamesine, a sigma-1 receptor agonist, functions in both neuroprotection and neurite outgrowth. We assessed the therapeutic effects of cutamesine in a rodent spinal cord injury (SCI) model to demonstrate pre-clinical proof-of-concept. First of all, in order to determine optimal cutamesine dose, cutamesine was administered to normal rats and BDNF protein levels in the lumbar spinal cord were assessed by Western blot. Next, for the SCI model, spinal cords of adult female Sprague-Dawley rats were contused using an Infinite Horizon Impactor. Two weeks post-injury, rats were randomly assigned to receive daily subcutaneous injections of either cutamesine (3.0 mg/kg/day) or saline (as a control) for another two weeks. Immunohistochemistry for BDNF and 5-HT was assessed at four and twelve weeks post-injury in the lumbar spinal cord. Locomotor function was assessed weekly using the BBB locomotor scale until twelve weeks after SCI and CatWalk XT 10.5 gait analysis was conducted at twelve weeks after SCI. In normal rats, cutamesine treatment (3.0 mg/kg/day) significantly up-regulated BDNF expression in the lumbar spinal cord. In SCI rats, cutamesine treatment (3.0 mg/kg/day) significantly increased the fluorescence intensity of neuronal BDNF and serotonin boutons in the injured spinal cord compared to saline. However, cutamesine treatment did not promote significant locomotor recovery. Recent work indicates that cutamesine treatment alone did not promote locomotor recovery in spite of immunohistological changes. Future work will explore the influence of combining cutamesine with other treatment promoting plasticity (e.g. rehabilitative training) in SCI rats.

Treadmill training based on the overload principle promotes locomotor recovery in a mouse model of chronic spinal cord injury

Rehabilitative treatment, including treadmill training, is considered an important strategy for restoring motor function after spinal cord injury (SCI). However, many unexplained problems persist regarding the appropriate rehabilitative method and the mechanism underlying the beneficial effects of rehabilitation. Moreover, only a few preclinical studies have been performed on rehabilitative interventions for chronic SCI, although most patients have chronic injuries. In fact, several preclinical studies reported that rehabilitative training was less effective when applied during the chronic phase than when applied sooner. While numerous studies have examined the effects of treadmill training during the subacute phase, the training conditions vary considerably among preclinical reports. Therefore, establishing a standard training protocol is essential for achieving beneficial rehabilitation effects at the chronic stage. Since the difficulty of applying an appropriate training load hinders training at constant speeds, it is important to adjust the training intensity in accordance with the exercise tolerance of an individual animal to provide further functional recovery benefits. Here, we created a novel quadrupedal treadmill training protocol based on the overload principle for mice with incomplete thoracic SCI. We subjected SCI model mice to rehabilitative training according to the protocol for two consecutive weeks starting at 42 days after injury. We examined the treadmill speeds at which the mice were able to run based on the severity of paresis and investigated the impact of the protocol on functional recovery. Assessment of running speed changes during the treadmill training period revealed faster treadmill speeds for mice with mild paresis than for those with severe paresis. The training parameters, including the speed and distance traveled, were positively correlated with the changes in motor function. These results suggest that the most suitable running speed during treadmill training differs according to the level of motor dysfunction and that running longer distances has a positive impact on motor functional recovery. Based on this established protocol, we compared functional and histological results between the chronic SCI groups with and without rehabilitation. The gait analyses showed significantly better functional improvement in the rehabilitation group than in the nonrehabilitation group. Histological analyses revealed that the BDNF- and VGLUT1-positive areas of lumbar enlargement were significantly increased in the rehabilitation group. These findings implied that rehabilitation promoted not only motor performance but also motor control, including forelimb-hindlimb coordination, even in chronic SCI, resulting in functional improvement by treadmill training alone. Therefore, rehabilitative training based on the overload principle appears to be one of the appropriate treatment options for incomplete thoracic SCI, and evidence of its efficacy exists in actual clinical settings.

Effects of Repetitive Transcranial Magnetic Stimulation (rTMS) and Treadmill Training on Recovery of Motor Function in a Rat Model of Partial Spinal Cord Injury

Background

This study aimed to investigate the effects of repetitive transcranial magnetic stimulation (rTMS) and treadmill training (TT) on motor function recovery in rats with partial spinal cord injury (SCI).

Material/Methods

Sixty rats with moderate partial SCI at the 9^th thoracic vertebral level induced by a Louisville Injury System Apparatus impactor were randomly allocated to 5 groups: Sham surgery (Intact); Sham rTMS without TT (S-rTMS/Non-TT); Sham rTMS with TT (S-rTMS/TT); rTMS without TT (rTMS/Non-TT); and rTMS with TT (rTMS/TT). Interventions commenced 8 days after SCI and continued for 8 weeks. Outcomes studied were Basso, Beattie, and Bresnahan locomotor scale scores, grid walking test, and biochemical analysis of the brain-derived neurotrophic factor (BDNF), synapsin I (SYN), and postsynaptic density protein-95 (PSD-95) in the motor cortex and spinal cord.

Results

The rTMS/TT contributed to greater Basso, Beattie, and Bresnahan scores compared with the S-rTMS/Non-TT (P<0.01), S-rTMS/TT (P<0.05), and rTMS/Non-TT (P<0.05), and showed obviously reduced numbers of foot drops compared with the S-rTMS/Non-TT (P<0.05). The rTMS/TT significantly increased the expressions of BDNF, SYN, and PSD-95 compared with the S-rTMS/Non-TT, both in the motor cortex (P<0.01, P<0.01, P<0.001, respectively) and spinal cord (P<0.001, P<0.01, P<0.05, respectively).

Conclusions

In a modified rat model of SCI, combined rTMS with TT improved motor function, indicating that this combined approach promoted adaptive neuroplasticity between the motor cortex and the spinal cord. A combined app roach to improving motor function following SCI requires further evaluation to determine the possible clinical applications.

Timing and dosage of FES cycling early after acute spinal cord injury: A case series report

OBJECTIVE

To understand the progression in parameters of functional electrical stimulation (FES) cycling dosage (including duration, velocity, stimulation amplitudes, power output), and the resulting changes in muscle mass early after acute spinal cord injury (SCI).

METHODS

Three participants, 24-38 years old, with neurological injury level C4-T4, severity AIS (American Spinal Injury Association Impairment Scale) A-C, started FES cycling 16-20 days post injury while admitted at a level-1 trauma center in Canada, and continued for 8-13 weeks in a rehabilitation hospital. They performed three sessions/week of 15-45 min FES cycling, supine or sitting. FES parameters, cycling performance, and muscle cross-sectional area (CSA) in thighs and calves were measured every 2 weeks.

RESULTS

Progression in power output, but not in session duration, was limited in two participants who experienced stimulation-associated referred pain or apprehension, requiring limitation of stimulation amplitudes for up to 65 days after the start of FES cycling. Participants started with 15 min cycling at 20 RPM with no resistance (0 W), and progressed to 30-45 min at 30 RPM producing 8.8-19.0 W average power/session after 2-3 months. Initially, muscle CSA decreased in all 3 participants (up to 16% after 6 weeks), and recovered later after a variable period of FES cycling (up to 16% at 13.3 weeks).

CONCLUSION

Progression of FES cycling in the first 3 months after injury required a highly individualized approach, guided by participant response, rather than standardized increments in stimulation intensity or duration. Changes in muscle CSA did not always correspond with the dose of FES cycling.

Functional electrical stimulation cycling exercise after spinal cord injury: a systematic review of health and fitness-related outcomes

OBJECTIVES

The objective of this review was to summarize and appraise evidence on functional electrical stimulation (FES) cycling exercise after spinal cord injury (SCI), in order to inform the development of evidence-based clinical practice guidelines.

METHODS

PubMed, the Cochrane Central Register of Controlled Trials, EMBASE, SPORTDiscus, and CINAHL were searched up to April 2021 to identify FES cycling exercise intervention studies including adults with SCI. In order to capture the widest array of evidence available, any outcome measure employed in such studies was considered eligible. Two independent reviewers conducted study eligibility screening, data extraction, and quality appraisal using Cochranes' Risk of Bias or Downs and Black tools. Each study was designated as a Level 1, 2, 3 or 4 study, dependent on study design and quality appraisal scores. The certainty of the evidence for each outcome was assessed using GRADE ratings ('High', 'Moderate', 'Low', or 'Very low').

RESULTS

Ninety-two studies met the eligibility criteria, comprising 999 adults with SCI representing all age, sex, time since injury, lesion level and lesion completeness strata. For muscle health (e.g., muscle mass, fiber type composition), significant improvements were found in 3 out of 4 Level 1-2 studies, and 27 out of 32 Level 3-4 studies (GRADE rating: 'High'). Although lacking Level 1-2 studies, significant improvements were also found in nearly all of 35 Level 3-4 studies on power output and aerobic fitness (e.g., peak power and oxygen uptake during an FES cycling test) (GRADE ratings: 'Low').

CONCLUSION

Current evidence indicates that FES cycling exercise improves lower-body muscle health of adults with SCI, and may increase power output and aerobic fitness. The evidence summarized and appraised in this review can inform the development of the first international, evidence-based clinical practice guidelines for the use of FES cycling exercise in clinical and community settings of adults with SCI. Registration review protocol: CRD42018108940 (PROSPERO).

Locomotor deficits induced by lumbar muscle inflammation involve spinal microglia and are independent of KCC2 expression in a mouse model of complete spinal transection

Spinal cord injury (SCI) is associated with damage to musculoskeletal tissues of the spine. Recent findings show that pain and inflammatory processes caused by musculoskeletal injury mediate plastic changes in the spinal cord. These changes could impede the adaptive plastic changes responsible for functional recovery. The underlying mechanism remains unclear, but may involve the microglia-BDNF-KCC2 pathway, which is implicated in sensitization of dorsal horn neurons in neuropathic pain and in the regulation of spinal excitability by step-training. In the present study, we examined the effects of step-training and lumbar muscle inflammation induced by complete Freund's adjuvant (CFA) on treadmill locomotion in a mouse model of complete spinal transection. The impact on locomotor recovery of each of these interventions alone or in combination were examined in addition to changes in microglia and KCC2 expression in the dorsal and ventral horns of the sublesional spinal cord. Results show that angular motion at the hip, knee and ankle joint during locomotion were decreased by CFA injection and improved by step-training. Moreover, CFA injection enhanced the expression of the microglial marker Iba1 in both ventral and dorsal horns, with or without step-training. However, this change was not associated with a modulation of KCC2 expression, suggesting that locomotor deficits induced by inflammation are independent of KCC2 expression in the sublesional spinal cord. These results indicate that musculoskeletal injury hinders locomotor recovery after SCI and that microglia is involved in this effect.

Outcome in Cats with Acute Onset of Severe Thoracolumbar Spinal Cord Injury Following Physical Rehabilitation

The literature is lacking data concerning the prognosis in cats suffering from naturally occurring acute onset of thoracolumbar (TL) spinal cord injury that are undergoing rehabilitation therapy. Therefore, we investigated the effect of physical rehabilitation in cats suffering from naturally occurring TL spinal cord injury. The medical records of 36 cats with acute onset of TL spinal cord injury that were selected for rehabilitation treatment were reviewed. Twenty-nine cats underwent an intensive physical rehabilitation protocol in the clinic (group 1), whereas the owners of seven cats declined physical rehabilitation (group 2). In group 1, seven cats had pelvic limb deep pain perception (DPP), which was significantly associated with the functional recovery of voluntary ambulatory status (p = 0.010) and voluntary micturition (p < 0.001). Spinal walking was achieved in 10/22 (45%) of the cats without DPP, and none regained voluntary micturition. In group 2, no cats regained ambulatory status or voluntary micturition, although pelvic limb DPP was present in three patients. Treatment with a clinic-based rehabilitation program and the presence of a crossed extensor reflex were significantly associated with a higher possibility of regaining functional ambulatory status (p < 0.010), but there was no difference in the recovery of voluntary micturition between the groups. Thus, cats with severe, naturally occurring, acute onset of TL spinal cord injury may benefit from physical rehabilitation. In the case of the loss of DPP, the acquisition of spinal walking is possible, despite the high possibility of a persistent neurologically dysfunctional bladder.

Self-directed rehabilitation training intensity thresholds for efficient recovery of skilled forelimb function in rats with cervical spinal cord injury

Task specific rehabilitation training is commonly used to treat motor dysfunction after neurological injures such as spinal cord injury (SCI), yet the use of task specific training in preclinical animal studies of SCI is not common. This is due in part to the difficulty in training animals to perform specific motor tasks, but also due to the lack of knowledge about optimal rehabilitation training parameters to maximize recovery. The single pellet reaching, grasping and retrieval (SPRGR) task (a.k.a. single pellet reaching task or Whishaw task) is a skilled forelimb motor task used to provide rehabilitation training and test motor recovery in rodents with cervical SCI. However, the relationships between the amount, duration, intensity, and timing of training remain poorly understood. In this study, using automated robots that allow rats with cervical SCI ad libitum access to self-directed SPRGR rehabilitation training, we show clear relationships between the total amount of rehabilitation training, the intensity of training (i.e., number of attempts/h), and performance in the task. Specifically, we found that rats naturally segregate into High and Low performance groups based on training strategy and performance in the task. Analysis of the different training strategies showed that more training (i.e., increased number of attempts in the SPRGR task throughout rehabilitation training) at higher intensities (i.e., number of attempts per hour) increased performance in the task, and that improved performance in the SPRGR task was linked to differences in corticospinal tract axon collateral densities in the injured spinal cords. Importantly, however, our data also indicate that rehabilitation training becomes progressively less efficient (i.e., less recovery for each attempt) as both the amount and intensity of rehabilitation training increases. Finally, we found that Low performing animals could increase their training intensity and transition to High performing animals in chronic SCI. These results highlight the rehabilitation training strategies that are most effective to regain skilled forelimb motor function after SCI, which will facilitate pre-clinical rehabilitation studies using animal models and could be beneficial in the development of more efficient clinical rehabilitation training strategies.

The effects of walking training onset on motor evoked potentials after acute spinal cord injury

AIM

The purposes of this study were to explore the optimal time for starting walking training in the first month after spinal cord injury (SCI) in rats and to discuss the relationship between changes in motor function and transcranial electrical motor evoked potentials (tceMEPs).

METHODS

Four groups of rats with SCI (BSWTT-3, 7, 14, 12) performed body-weight-supported treadmill training (BWSTT) for three weeks beginning at 3, 7, 14, and 21 days after SCI, respectively. The Basso, Beattie, and Bresnahan (BBB) score and tceMEPs were assessed weekly. Weekly repeated measures and multiple comparisons between groups were performed to identify differences in motor function and tceMEPs. Correlation analysis was performed to clarify the relationship between BBB scores and tceMEPs over time.

RESULTS

Although there was no significant difference between the BWSTT-14 group and the other three BWSTT groups at the end of the experiment in terms of BBB scores and the latency of tceMEPs, the BWSTT-14 group obtained the best trends in improvement of BBB scores and the latencies and amplitudes of tceMEPs over time. The BBB scores of rats with SCI were strongly negatively correlated with tceMEPs latency. The BBB scores of rats with SCI, except for the rats in the BWSTT-3 group, were strongly positively correlated with the tceMEPs amplitude.

CONCLUSIONS

The preliminary conclusion was that based on a rat model, 14 days after SCI was the optimal time for starting BWSTT. tceMEPs were an objective indicator of spinal cord nerve function, which was strongly correlated with motor function recovery. However, one limitation of this study was that the rats in the Sham group did not undergo BWSTT, which made the training itself a confounding factor for the results.

Blood glutamate scavengers and exercises as an effective neuroprotective treatment in mice with spinal cord injury

OBJECTIVE

Excitotoxicity due to neuronal damage and glutamate release is one of the first events that leads to the progression of neuronal degeneration and functional impairment. This study is based on a paradigm shift in the therapeutic approach for treating spinal cord injury (SCI). The authors tested a new treatment targeting removal of CNS glutamate into the blood circulation by injection of the blood glutamate scavengers (BGSs) recombinant enzyme glutamate-oxaloacetate transaminase (rGOT1) and its cosubstrate oxaloacetic acid (OxAc). Their primary objective was to investigate whether BGS treatment, followed by treadmill exercises in mice with SCI, could attenuate excitotoxicity, inflammation, scarring, and axonal degeneration and, at a later time point, improve functional recovery.

METHODS

A pharmacokinetic experiment was done in C57BL/6 naive mice to verify rGOT1/OxAc blood activity and to characterize the time curve of glutamate reduction in the blood up to 24 hours. The reduction of glutamate in CSF after BGS administration in mice with SCI was confirmed by high-performance liquid chromatography. Next, SCI (left hemisection) was induced in the mice, and the mice were randomly assigned to one of the following groups at 1 hour postinjury: control (underwent SCI and received PBS), treadmill exercises, rGOT1/OxAc treatment, or rGOT1/OxAc treatment followed by treadmill exercises. Treatment started 1 hour postinjury with an injection of rGOT1/OxAc and continued for 5 consecutive days. Starting 1 week after SCI, the exercises and the combined treatment groups recommenced the treadmill exercise regimen 5 days a week for 3 months. Locomotor function was assessed for 3 months using the horizontal grid walking test and CatWalk. Axonal anterograde and wallerian degenerations were evaluated using tetramethylrhodamine dextran. Tissue sections were immunofluorescently stained for Iba1, GFAP, GAP-43, synaptophysin, and NeuN.

RESULTS

BGS treatment decreased the CSF glutamate level up to 50%, reduced axonal wallerian degeneration, and increased axonal survival and GAP-43 expression in neuronal cells. Combined treatment reduced inflammation, scarring, and lesion size. Additionally, the combination of BGS treatment and exercises increased synapses around motor neurons and enhanced axonal regeneration through the lesion site. This resulted in motor function improvement 3 months post-SCI.

CONCLUSIONS

As shown by biochemical, immunohistochemical, and functional analysis, BGSs exhibit a substantial neuroprotective effect by reducing excitotoxicity and secondary damage after SCI. Furthermore, in combination with exercises, they reduced axonal degeneration and scarring and resulted in improved functional recovery.

Delayed Injection of a Physically Cross-Linked PNIPAAm-g-PEG Hydrogel in Rat Contused Spinal Cord Improves Functional Recovery

Spinal cord injury is a main health issue, leading to multiple functional deficits with major consequences such as motor and sensitive impairment below the lesion. To date, all repair strategies remain ineffective. In line with the experiments showing that implanted hydrogels, immunologically inert biomaterials, from natural or synthetic origins, are promising tools and in order to reduce functional deficits, to increase locomotor recovery, and to reduce spasticity, we injected into the lesion area, 1 week after a severe T10 spinal cord contusion, a thermoresponsive physically cross-linked poly(N-isopropylacrylamide)-poly(ethylene glycol) copolymer hydrogel. The effect of postinjury intensive rehabilitation training was also studied. A group of male Sprague-Dawley rats receiving the hydrogel was enrolled in an 8 week program of physical activity (15 min/day, 5 days/week) in order to verify if the combination of a treadmill step-training and hydrogel could lead to better outcomes. The data obtained were compared to those obtained in animals with a spinal lesion alone receiving a saline injection with or without performing the same program of physical activity. Furthermore, in order to verify the biocompatibility of our designed biomaterial, an inflammatory reaction (interleukin-1β, interleukin-6, and tumor necrosis factor-α) was examined 15 days post-hydrogel injection. Functional recovery (postural and locomotor activities and sensorimotor coordination) was assessed from the day of injection, once a week, for 9 weeks. Finally, 9 weeks postinjection, the spinal reflexivity (rate-dependent depression of the H-reflex) was measured. The results indicate that the hydrogel did not induce an additional inflammation. Furthermore, we observed the same significant locomotor improvements in hydrogel-injected animals as in trained saline-injected animals. However, the combination of hydrogel with exercise did not show higher recovery compared to that evaluated by the two strategies independently. Finally, the H-reflex depression recovery was found to be induced by the hydrogel and, albeit to a lesser degree, exercise. However, no recovery was observed when the two strategies were combined. Our results highlight the effectiveness of our copolymer and its high therapeutic potential to preserve/repair the spinal cord after lesion.

Neuropathic pain after spinal cord injury and physical exercise in animal models: A systematic review and meta-analysis

The aim of this systematic review was to summarize the effects of physical exercise on neuropathic pain (NP) in animal models of SCI. The search was conducted in Medline and Science Direct to identify experimental preclinical studies involving animal models of SCI, physical exercise as an intervention and the assessment of NP. Fifteen articles met the eligibility criteria. The review shows that in studies of NP involving animal models of SCI, rodents are the most common species. Thoracic contusion is the most common injury and mechanical and thermal nociception are the most frequently assessed NP components. The benefits of physical exercise vary according to its starting period and total duration. In addition, there is considerable heterogeneity regarding the type and intensity of exercise capable of alleviating NP after SCI. Furthermore, physical exercise has beneficial effects on mechanical, thermal and cold nociception, and spontaneous pain. These results are weakened by the paucity of studies involving these pain outcomes. The review protocol is published for free access on the SyRF platform (http://syrf.org.uk/protocols/).

Locomotor training with adjuvant testosterone preserves cancellous bone and promotes muscle plasticity in male rats after severe spinal cord injury

Loading and testosterone may influence musculoskeletal recovery after spinal cord injury (SCI). Our objectives were to determine (a) the acute effects of bodyweight-supported treadmill training (TM) on hindlimb cancellous bone microstructure and muscle mass in adult rats after severe contusion SCI and (b) whether longer-term TM with adjuvant testosterone enanthate (TE) delivers musculoskeletal benefit. In Study 1, TM (40 min/day, 5 days/week, beginning 1 week postsurgery) did not prevent SCI-induced hindlimb cancellous bone loss after 3 weeks. In Study 2, TM did not attenuate SCI-induced plantar flexor muscles atrophy nor improve locomotor recovery after 4 weeks. In our main study, SCI produced extensive distal femur and proximal tibia cancellous bone deficits, a deleterious slow-to-fast fiber-type transition in soleus, lower muscle fiber cross-sectional area (fCSA), impaired muscle force production, and levator ani/bulbocavernosus (LABC) muscle atrophy after 8 weeks. TE alone (7.0 mg/week) suppressed bone resorption, attenuated cancellous bone loss, constrained the soleus fiber-type transition, and prevented LABC atrophy. In comparison, TE+TM concomitantly suppressed bone resorption and stimulated bone formation after SCI, produced near-complete cancellous bone preservation, prevented the soleus fiber-type transition, attenuated soleus fCSA atrophy, maintained soleus force production, and increased LABC mass. 75% of SCI+TE+TM animals recovered voluntary over-ground hindlimb stepping, while no SCI and only 20% of SCI+TE animals regained stepping ability. Positive associations between testosterone and locomotor function suggest that TE influenced locomotor recovery. In conclusion, short-term TM alone did not improve bone, muscle, or locomotor recovery in adult rats after severe SCI, while longer-term TE+TM provided more comprehensive musculoskeletal benefit than TE alone.

Rehabilitative Training in Animal Models of Spinal Cord Injury

Rehabilitative motor training is currently one of the most widely used approaches to promote moderate recovery following injuries of the central nervous system. Such training is generally applied in the clinical setting, whereas it is not standard in preclinical research. This is a concern as it is becoming increasingly apparent that neuroplasticity enhancing treatments require training or some form of activity as a co-therapy to promote functional recovery. Despite the importance of training and the many open questions regarding its mechanistic consequences, its use in preclinical animal models is rather limited. Here we review approaches, findings and challenges when training is applied in animal models of spinal cord injury, and we suggest recommendations to facilitate the integration of training using an appropriate study design, into pre-clinical studies.

Outcome heterogeneity and bias in acute experimental spinal cord injury: A meta-analysis

OBJECTIVE

To determine whether and to what degree bias and underestimated variability undermine the predictive value of preclinical research for clinical translation.

METHODS

We investigated experimental spinal cord injury (SCI) studies for outcome heterogeneity and the impact of bias. Data from 549 preclinical SCI studies including 9,535 animals were analyzed with meta-regression to assess the effect of various study characteristics and the quality of neurologic recovery.

RESULTS

Overall, the included interventions reported a neurobehavioral outcome improvement of 26.3% (95% confidence interval 24.3-28.4). Response to treatment was dependent on experimental modeling paradigms (neurobehavioral score, site of injury, and animal species). Applying multiple outcome measures was consistently associated with smaller effect sizes compared with studies applying only 1 outcome measure. More than half of the studies (51.2%) did not report blinded assessment, constituting a likely source of evaluation bias, with an overstated effect size of 7.2%. Assessment of publication bias, which extrapolates to identify likely missing data, suggested that between 2% and 41% of experiments remain unpublished. Inclusion of these theoretical missing studies suggested an overestimation of efficacy, reducing the effect sizes by between 0.9% and 14.3%.

CONCLUSIONS

We provide empirical evidence of prevalent bias in the design and reporting of experimental SCI studies, resulting in overestimation of the effectiveness. Bias compromises the internal validity and jeopardizes the successful translation of SCI therapies from the bench to bedside.

Improvement of motor function induced by skeletal muscle contraction in spinal cord-injured rats

BACKGROUND

The involvement of neurotrophic factors such as brain-derived neurotrophic factor (BDNF) in functional recovery after spinal cord injury (SCI) by treadmill training has been suggested. The precise mechanism is poorly understood. However, muscle-derived bioactive molecules (myokines) are known to be produced by muscle contraction. Although BDNF is a myokine and is considered to be a potential mediator of neuroplasticity following exercise, its contribution to motor function recovery after SCI has not yet been described in detail.

PURPOSE

To investigate the role of muscle contraction in motor function recovery after SCI, with a focus on BDNF.

STUDY DESIGN

Male Sprague-Dawley rats (aged 8-9 weeks) were used to establish the SCI model. Percutaneous electrical muscle stimulation (10 mA, 2 Hz, 10 minutes) was applied to both hindlimbs of the rats immediately after SCI. The stimulation was performed once per day for 4 weeks. The sham, SCI only (SCI), and SCI with electrical muscle stimulation (SCI+ES) groups were compared.

METHODS

Spinal cord injury was induced by dropping a 20 g rod with an apex diameter of 2 mm from a height of 25 mm onto the spine of an anesthetized rat at the T9 level. Motor function was assessed using the Basso-Beattie-Bresnahan Locomotor Scale, inclined plane test, and rotarod test. One week after injury, terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells were counted at the injury epicenter, and the level of BDNF was measured in both the spinal cord and the anterior tibial muscle. Four weeks after injury, the cavity volume of the epicenter and the level of phosphorylated growth-associated protein 43 in the spinal cord were measured.

RESULTS

Significantly improved Basso-Beattie-Bresnahan scores and inclined plane test results were observed in the SCI+ES group compared with those in the SCI group at 4 weeks post-SCI. We also observed a decrease in the cavity volume and an increase in phosphorylated growth-associated protein 43 levels in the SCI+ES group. Electrical muscle stimulation decreased the numbers of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells in the epicenter and increased the levels of BDNF in the spinal cord and lower limb muscles at 1 week post-SCI.

CONCLUSIONS

Electrical muscle stimulation improved motor function and increased BDNF levels in both the muscles and the spinal cords of rats subjected to SCI. Muscle contraction-induced BDNF expression might be involved in motor recovery during rehabilitation.

CLINICAL RELEVANCE

Our study provides experimental evidence for a possible therapeutic role of peripheral electrical muscle stimulation to enhance motor recovery after SCI.

Multifunctionalized hydrogels foster hNSC maturation in 3D cultures and neural regeneration in spinal cord injuries

Cells reside in 3D microenvironments in living tissues; consequently, 3D cultures gained great interest because they better mimic the natural conditions of cells. Self-assembling peptides (SAPs) are synthetic bioabsorbable biomaterials that can provide customized 3D microenvironments regulating cell functionalities and tissue repair. Here we introduce a SAP-hydrogel designed to support human neural stem cell (hNSC) differentiation in 3D serum-free conditions, generating mature and active human neurons in vitro. We also demonstrate its functional neurorigenerative potential in rat spinal cord injuries, peaking when seeded with hNSCs progeny predifferentiated in vitro for 6 weeks. Despite these promising results, this approach should be confirmed in the future with medium-size animal models and with additional and refined behavioral tests before entering a clinical trial.

Three-dimensional cell cultures are leading the way to the fabrication of tissue-like constructs useful to developmental biology and pharmaceutical screenings. However, their reproducibility and translational potential have been limited by biomaterial and culture media compositions, as well as cellular sources. We developed a construct comprising synthetic multifunctionalized hydrogels, serum-free media, and densely seeded good manufacturing practice protocol-grade human neural stem cells (hNSC). We tracked hNSC proliferation, differentiation, and maturation into GABAergic, glutamatergic, and cholinergic neurons, showing entangled electrically active neural networks. The neuroregenerative potential of the “engineered tissue” was assessed in spinal cord injuries, where hNSC-derived progenitors and predifferentiated hNSC progeny, embedded in multifunctionalized hydrogels, were implanted. All implants decreased astrogliosis and lowered the immune response, but scaffolds with predifferentiated hNSCs showed higher percentages of neuronal markers, better hNSC engraftment, and improved behavioral recovery. Our hNSC-construct enables the formation of 3D functional neuronal networks in vitro, allowing novel strategies for hNSC therapies in vivo.

Locomotor Training Increases Synaptic Structure With High NGL-2 Expression After Spinal Cord Hemisection

BACKGROUND

We previously demonstrated that step training leads to reorganization of neuronal networks in the lumbar spinal cord of rodents after a hemisection (HX) injury and step training, including increases excitability of spinally evoked potentials in hindlimb motor neurons.

METHODS

In this study, we investigated changes in RNA expression and synapse number using RNA-Seq and immunohistochemistry of the lumbar spinal cord 23 days after a mid-thoracic HX in rats with and without post-HX step training.

RESULTS

Gene Ontology (GO) term clustering demonstrated that expression levels of 36 synapse-related genes were increased in trained compared with nontrained rats. Many synaptic genes were upregulated in trained rats, but Lrrc4 (coding NGL-2) was the most highly expressed in the lumbar spinal cord caudal to the HX lesion. Trained rats also had a higher number of NGL-2/synaptophysin synaptic puncta in the lumbar ventral horn.

CONCLUSIONS

Our findings demonstrate clear activity-dependent regulation of synapse-related gene expression post-HX. This effect is consistent with the concept that activity-dependent phenomena can provide a mechanistic drive for epigenetic neuronal group selection in the shaping of the reorganization of synaptic networks to learn the locomotion task being trained after spinal cord injury.

The combined effect of granulocyte-colony stimulating factor (G-CSF) treatment and exercise in rats with spinal cord injury

Objective: To identify that the combined G-CSF and treadmill exercise is more effective in functional recovery after spinal cord injury (SCI).Design: Rats were divided into 4 groups: a SCI group treated with G-CSF (G-CSF group, n = 6), a SCI group treated with treadmill exercise plus G-CSF (G-CSF/exercise group, n = 6), a SCI group with treadmill exercise (exercise group, n = 6), and a SCI group without treatments (control group, n = 6). We performed laminectomy at the T8-10 spinal levels with compression injury of the spinal cord in all rats. G-CSF (20 μg/ml) was administered intraperitoneally for 5 consecutive days after SCI in G-CSF and G-CSF/exercise groups. From one week after surgery, animals in G-CSF/exercise and exercise groups received 30 min of exercise 5 days per week for 4 weeks. Functional recoveries were assessed using the Basso, Beattie, and Bresnahan (BBB) scale and the inclined plane test. Five weeks after SCI, hematoxylin and eosin staining for cavity size and immunohistochemistry for glial scar formation and neuro-regeneration factor expression were conducted.Setting: Inha University School of medicine, Incheon, KoreaResults: Rats in G-CSF/exercise group showed the most effective functional recovery in the BBB scale and the inclined plane test, and spinal cord cavity size by injury were the smallest, and immunohistochemistry revealed expression of higher BDNF (brain-derived neurotrophic factor) and VEGF (vascular endothelial growth factor) and lower GFAP (glial fibrillary acidic protein) than others.Conclusion: Combined treatment provided more effective neuroplasty and functional recovery than individual treatments.

Enhanced Voluntary Exercise Improves Functional Recovery following Spinal Cord Injury by Impacting the Local Neuroglial Injury Response and Supporting the Rewiring of Supraspinal Circuits

Recent reports suggest that rehabilitation measures that increase physical activity of patients can improve functional outcome after incomplete spinal cord injuries (iSCI). To investigate the structural basis of exercise-induced recovery, we examined local and remote consequences of voluntary wheel training in spinal cord injured female mice. In particular, we explored how enhanced voluntary exercise influences the neuronal and glial response at the lesion site as well as the rewiring of supraspinal tracts after iSCI. We chose voluntary exercise initiated by providing mice with free access to running wheels over "forced overuse" paradigms because the latter, at least in some cases, can lead to worsening of functional outcomes after SCI. Our results show that mice extensively use their running wheels not only before but also after injury reaching their pre-lesion exercise levels within five days after injury. Enhanced voluntary exercise improved their overall and skilled motor function after injury. In addition, exercising mice started to recover earlier and reached better sustained performance levels. These improvements in motor performance are accompanied by early changes of axonal and glial response at the lesion site and persistent enhancements of the rewiring of supraspinal connections that resulted in a strengthening of both indirect and direct inputs to lumbar motoneurons.

Eliciting inflammation enables successful rehabilitative training in chronic spinal cord injury

Rehabilitative training is one of the most successful therapies to promote motor recovery after spinal cord injury, especially when applied early after injury. Polytrauma and management of other medical complications in the acute post-injury setting often preclude or complicate early rehabilitation. Therefore, interventions that reopen a window of opportunity for effective motor training after chronic injury would have significant therapeutic value. Here, we tested whether this could be achieved in rats with chronic (8 weeks) dorsolateral quadrant sections of the cervical spinal cord (C4) by inducing mild neuroinflammation. We found that systemic injection of a low dose of lipopolysaccharide improved the efficacy of rehabilitative training on forelimb function, as assessed using a single pellet reaching and grasping task. This enhanced recovery was found to be dependent on the training intensity, where a high-intensity paradigm induced the biggest improvements. Importantly, in contrast to training alone, the combination of systemic lipopolysaccharide and high-intensity training restored original function (reparative plasticity) rather than enhancing new motor strategies (compensatory plasticity). Accordingly, electrophysiological and tract-tracing studies demonstrated a recovery in the cortical drive to the affected forelimb muscles and a restructuration of the corticospinal innervation of the cervical spinal cord. Thus, we propose that techniques that can elicit mild neuroinflammation may be used to enhance the efficacy of rehabilitative training after chronic spinal cord injury.

Activity-Based Physical Rehabilitation with Adjuvant Testosterone to Promote Neuromuscular Recovery after Spinal Cord Injury

Neuromuscular impairment and reduced musculoskeletal integrity are hallmarks of spinal cord injury (SCI) that hinder locomotor recovery. These impairments are precipitated by the neurological insult and resulting disuse, which has stimulated interest in activity-based physical rehabilitation therapies (ABTs) that promote neuromuscular plasticity after SCI. However, ABT efficacy declines as SCI severity increases. Additionally, many men with SCI exhibit low testosterone, which may exacerbate neuromusculoskeletal impairment. Incorporating testosterone adjuvant to ABTs may improve musculoskeletal recovery and neuroplasticity because androgens attenuate muscle loss and the slow-to-fast muscle fiber-type transition after SCI, in a manner independent from mechanical strain, and promote motoneuron survival. These neuromusculoskeletal benefits are promising, although testosterone alone produces only limited functional improvement in rodent SCI models. In this review, we discuss the (1) molecular deficits underlying muscle loss after SCI; (2) independent influences of testosterone and locomotor training on neuromuscular function and musculoskeletal integrity post-SCI; (3) hormonal and molecular mechanisms underlying the therapeutic efficacy of these strategies; and (4) evidence supporting a multimodal strategy involving ABT with adjuvant testosterone, as a potential means to promote more comprehensive neuromusculoskeletal recovery than either strategy alone.

A randomized, blinded, prospective clinical trial of postoperative rehabilitation in dogs after surgical decompression of acute thoracolumbar intervertebral disc herniation

BACKGROUND

Experimental evidence shows benefit of rehabilitation after spinal cord injury (SCI) but there are limited objective data on the effect of rehabilitation on recovery of dogs after surgery for acute thoracolumbar intervertebral disc herniations (TL-IVDH).

OBJECTIVE

Compare the effect of basic and intensive post-operative rehabilitation programs on recovery of locomotion in dogs with acute TL-IVDH in a randomized, blinded, prospective clinical trial.

ANIMALS

Thirty non-ambulatory paraparetic or paraplegic (with pain perception) dogs after decompressive surgery for TL-IVDH.

METHODS

Blinded, prospective clinical trial. Dogs were randomized (1:1) to a basic or intensive 14-day in-house rehabilitation protocol. Fourteen-day open field gait score (OFS) and coordination (regulatory index, RI) were primary outcomes. Secondary measures of gait, post-operative pain, and weight were compared at 14 and 42 days.

RESULTS

Of 50 dogs assessed, 32 met inclusion criteria and 30 completed the protocol. There were no adverse events associated with rehabilitation. Median time to walking was 7.5 (2 - 37) days. Mean change in OFS by day 14 was 6.13 (confidence intervals: 4.88, 7.39, basic) versus 5.73 (4.94, 6.53, intensive) representing a treatment effect of -0.4 (-1.82, 1.02) which was not significant, P=.57. RI on day 14 was 55.13 (36.88, 73.38, basic) versus 51.65 (30.98, 72.33, intensive), a non-significant treatment effect of -3.47 (-29.81, 22.87), P = .79. There were no differences in secondary outcomes between groups.

CONCLUSIONS

Early postoperative rehabilitation after surgery for TL-IVDH is safe but doesn't improve rate or level of recovery in dogs with incomplete SCI.

Effective robotic assistive pattern of treadmill training for spinal cord injury in a rat model

The purpose of the present study was to establish an effective robotic assistive stepping pattern of body-weight-supported treadmill training based on a rat spinal cord injury (SCI) model and assess the effect by comparing this with another frequently used assistive stepping pattern. The recorded stepping patterns of both hind limbs of trained intact rats were edited to establish a 30-sec playback normal rat stepping pattern (NRSP). Step features (step length, step height, step number and swing duration), BBB scores, latencies, and amplitudes of the transcranial electrical motor-evoked potentials (tceMEPs) and neurofilament 200 (NF200) expression in the spinal cord lesion area during and after 3 weeks of body-weight-supported treadmill training (BWSTT) were compared in rats with spinal contusion receiving NRSP assistance (NRSPA) and those that received manual assistance (MA). Hind limb stepping performance among rats receiving NRSPA during BWSTT was greater than that among rats receiving MA in terms of longer step length, taller step height, and longer swing duration. Furthermore a higher BBB score was also indicated. The rats in the NRSPA group achieved superior results in the tceMEPs assessment and greater NF200 expression in the spinal cord lesion area compared with the rats in the MA group. These findings suggest NRSPA was an effective assistive pattern of treadmill training compared with MA based on the rat SCI model and this approach could be used as a new platform for animal experiments for better understanding the mechanisms of SCI rehabilitation.

Human dental pulp stem cells transplantation combined with treadmill training in rats after traumatic spinal cord injury

Spinal cord injury (SCI) is a disabling condition resulting in deficits of sensory and motor functions, and has no effective treatment. Considering that protocols with stem cell transplantation and treadmill training have shown promising results, the present study evaluated the effectiveness of stem cells from human exfoliated deciduous teeth (SHEDs) transplantation combined with treadmill training in rats with experimental spinal cord injury. Fifty-four Wistar rats were spinalized using NYU impactor. The rats were randomly distributed into 5 groups: Sham (laminectomy with no SCI, n=10); SCI (laminectomy followed by SCI, n=12); SHEDs (SCI treated with SHEDs, n=11); TT (SCI treated with treadmill training, n=11); SHEDs+TT (SCI treated with SHEDs and treadmill training; n=10). Treatment with SHEDs alone or in combination with treadmill training promoted functional recovery, reaching scores of 15 and 14, respectively, in the BBB scale, being different from the SCI group, which reached 11. SHEDs treatment was able to reduce the cystic cavity area and glial scar, increase neurofilament. Treadmill training alone had no functional effectiveness or tissue effects. In a second experiment, the SHEDs transplantation reduced the TNF-α levels in the cord tissue measured 6 h after the injury. Contrary to our hypothesis, treadmill training either alone or in combination, caused no functional improvement. However, SHEDs showed to be neuroprotective, by the reduction of TNF-α levels, the cystic cavity and the glial scar associated with the improvement of motor function after SCI. These results provide evidence that grafted SHEDs might be an effective therapy to spinal cord lesions, with possible anti-inflammatory action.

Training to Improve Walking after Pediatric Spinal Cord Injury: A Systematic Review of Parameters and Walking Outcomes

Walking or locomotor training is often initiated following pediatric spinal cord injury (SCI). There is no synthesis of the literature on interventions targeting walking for pediatric SCI, although this would assist future clinical trials and interventions. To address this need, we completed a systematic review to summarize the who, what, when, and how of walking interventions in children with SCI. Participant characteristics, training parameters, and walking outcomes with training in pediatric SCI were identified and compared with training parameters and outcomes in adults with SCI. The PubMed, Medline, AMED, Embase, PsycInfo, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and CINAHL databases were searched for studies that included participants aged 1-17 years with a SCI acquired post-birth, physical interventions, and pre- and post-training walking measures. Two researchers evaluated each study's risk of bias using a domain-based approach. Training parameters and walking outcomes were extracted. Total training duration (duration × frequency × number of weeks) was calculated. Thirteen pediatric studies (n = 43 children) were included; all but one were case series/reports. Risk of bias was high in the pediatric studies. A 2012 adult review was updated (11 studies added). As with adults, the training durations, frequencies, and modes used with the children varied; however, overground walking practice was included in 10/13 pediatric studies. Improvements in walking capacity, speed, and distance were comparable between children and adults. There was a trend for greater gains with greater total training durations. There is a paucity of high-quality research examining interventions targeting walking after pediatric SCI; however, intensive training, including practice overground, results in notable improvements.

Effects of Activity-Based Therapy Interventions on Mobility, Independence, and Quality of Life for People with Spinal Cord Injuries: A Systematic Review and Meta-Analysis

The aim of this study was to review the literature about the effects of activity-based therapy (ABT) interventions on mobility, functional independence, and quality of life for people with a spinal cord injury (SCI). A systematic review with meta-analysis of randomized and non-randomized trials was performed, including adults with a non-progressive SCI at any level. The intervention of interest was ABT, defined as any intervention that sought to improve muscle activation or sensory function below the level of injury in the spinal cord and does not rely on compensatory mechanisms for improving function. The comparison was either no intervention or conventional physical interventions targeted to regions above the level of injury. The outcome measures were quality-of-life questionnaires, mobility assessments, and functional independence scales. Nineteen trials were included in this systematic review. Three compared ABT to no intervention and 16 to conventional physical rehabilitation. The methodological quality of the trials was assessed using the PEDro scale as moderate. Six studies investigated the effects of ABT interventions for the upper limbs, 11 investigated gait-related interventions, and two applied multi-modal interventions. Compared with no intervention, the meta-analysis found that ABT was not more effective for improving independence or lower limb mobility, but conferred a large positive effect on upper limb function. Compared with conventional physical interventions, there was no significant effect of ABT on lower limb mobility, independence, or quality of life; however, it had positive effects on upper limbs. In conclusion, there is evidence that ABT can improve independence and functional ability when applied to the upper limbs in people with SCI. However, it is not superior to conventional physical interventions when applied to the lower limbs.

SCIPA Switch-On: A Randomized Controlled Trial Investigating the Efficacy and Safety of Functional Electrical Stimulation–Assisted Cycling and Passive Cycling Initiated Early After Traumatic Spinal Cord Injury

Background. Substantial skeletal muscle atrophy after spinal cord injury (SCI) carries significant repercussions for functional recovery and longer-term health. Objective. To compare the efficacy, safety, and feasibility of functional electrical stimulation–assisted cycling (FESC) and passive cycling (PC) to attenuate muscle atrophy after acute SCI. Methods. This multicenter, assessor-blinded phase I/II trial randomized participants at 4 weeks post-SCI to FESC or PC (4 sessions per week, 1 hour maximum per session, over 12 weeks). The primary outcome measure was mean maximum cross-sectional area (CSA) of thigh and calf muscles (magnetic resonance imaging), and secondary outcome measures comprised body composition (dual energy X-ray absorptiometry), anthropometry, quality of life, and adverse events (AEs). Results. Of 24 participants, 19 completed the 12-week trial (10 FESC, 9 PC, 18 male). Those participants completed >80% of training sessions (FESC, 83.5%; PC, 85.9%). No significant between-group difference in postintervention muscle CSA was found. No significant between-group difference was found for any other tissue, anthropometric parameter, or behavioral variable or AEs. Six participants experienced thigh hypertrophy (FESC = 3; PC = 3). Atrophy was attenuated (<30%) in 15 cases (FESC = 7; PC = 8). Conclusions. Both cycle ergometry regimens examined were safe, feasible, and well tolerated early after SCI. No conclusions regarding efficacy can be drawn from our data. Further investigation of both modalities early after SCI is required.

Acquisition of Involuntary Spinal Locomotion (Spinal Walking) in Dogs with Irreversible Thoracolumbar Spinal Cord Lesion: 81 Dogs

BACKGROUND

Spinal walking (SW) is described as the acquisition of an involuntary motor function in paraplegic dogs and cats without pain perception affected by a thoracolumbar lesion. Whereas spinal locomotion is well described in cats that underwent training trials after experimental spinal cord resection, less consistent information is available for dogs.

HYPOTHESIS

Paraplegic dogs affected by a thoracolumbar complete spinal cord lesion undergoing intensive physical rehabilitation could acquire an autonomous SW gait under field conditions.

ANIMALS

Eighty-one acute paraplegic thoracolumbar dogs without pelvic limb pain perception.

METHODS

Retrospective study of medical records of dogs selected for intensive rehabilitation treatment in paraplegic dogs with absence of pain perception on admission and during the whole treatment. Binary regression and multivariate logistic regression were used to analyze potential associations with the development of SW.

RESULTS

Autonomous SW was achieved in 48 dogs (59%). Median time to achieve SW was of 75.5 days (range: 16-350 days). On univariate analysis, SW gait was associated with younger age (P = .002) and early start of physiotherapy (P = .024). Multivariate logistic regression showed that younger age (≤60 months) and lightweight (≤7.8 kg) were positively associated with development of SW (P = .012 and P < .001, respectively). BCS, full-time hospitalization, and type and site of the lesion were not significantly associated with development of SW.

CONCLUSIONS

Dogs with irreversible thoracolumbar lesion undergoing intensive physiotherapic treatment can acquire SW. Younger age and lightweight are positively associated with the development of SW gait.

Animal models of spinal cord injury: a systematic review

STUDY DESIGN

PRISMA-guided systematic review.

OBJECTIVES

To provide a comprehensive framework of the current animal models for investigating spinal cord injury (SCI) and categorize them based on the aims, patterns and levels of injury, and outcome measurements as well as animal species.

SETTING

Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran.

METHODS

An electronic search of the Medline database for literature describing animal models of SCI was performed on 1 January 2016 using the following keywords: 'spinal cord injuries' and 'animal models'. The search retrieved 2870 articles. Reviews and non-original articles were excluded. Data extraction was independently performed by two reviewers.

RESULTS

Among the 2209 included studies, testing the effects of drug's or growth factor's interventions was the most common aim (36.6%) followed by surveying pathophysiologic changes (30.2%). The most common spinal region involved was thoracic (81%). Contusion was the most common pattern of injury (41%) followed by transection (32.5%) and compression (19.4%). The most common species involved in animal models of SCI was the rat (72.4%). Two or more types of outcome assessments were used in the majority of the studies, and the most common assessment method was biological plus behavioral (50.8%).

CONCLUSIONS

Prior to choosing an animal model, the objectives of the proposed study must precisely be defined. Contusion and compression models better simulate the biomechanics and neuropathology of human injury, whereas transection models are valuable to study anatomic regeneration. Rodents are the most common and probably best-suited species for preliminary SCI studies.

What Did We Learn from the Animal Studies of Body Weight-Supported Treadmill Training and Where Do We Go from Here?

Body weight-supported treadmill training (BWSTT) developed from animal studies of spinal cord injury (SCI). Evidence that spinal cats (i.e., cats that have a complete surgical transection of the cord) could regain the ability to step on a moving treadmill indicated a vast potential for spinal circuits to generate walking without the brain. BWSTT represented a means to unlock that potential. As the technique was adapted as a rehabilitation intervention for humans with SCI, shortcomings in the translation to walking in the real world were exposed. Evidence that BWSTT has not been as successful for humans with SCI leads us to revisit key animal studies. In this short review, we describe the task-specific nature of BWSTT and discuss how this specificity may pose limits on the recovery of overground walking. Also discussed are more recent studies that have introduced new strategies and tools that adapt BWSTT ideas to more functionally-relevant tasks. We introduce a new device for weight-supported overground walking in rats called Circular BART (Body weight supported Ambulatory Rat Trainer) and demonstrate that it is relatively easy and inexpensive to produce. Future animal studies will benefit from the development of simple tools that facilitate training and testing of overground walking.

What Is Being Trained? How Divergent Forms of Plasticity Compete To Shape Locomotor Recovery after Spinal Cord Injury

Spinal cord injury (SCI) is a devastating syndrome that produces dysfunction in motor and sensory systems, manifesting as chronic paralysis, sensory changes, and pain disorders. The multi-faceted and heterogeneous nature of SCI has made effective rehabilitative strategies challenging. Work over the last 40 years has aimed to overcome these obstacles by harnessing the intrinsic plasticity of the spinal cord to improve functional locomotor recovery. Intensive training after SCI facilitates lower extremity function and has shown promise as a tool for retraining the spinal cord by engaging innate locomotor circuitry in the lumbar cord. As new training paradigms evolve, the importance of appropriate afferent input has emerged as a requirement for adaptive plasticity. The integration of kinematic, sensory, and loading force information must be closely monitored and carefully manipulated to optimize training outcomes. Inappropriate peripheral input may produce lasting maladaptive sensory and motor effects, such as central pain and spasticity. Thus, it is important to closely consider the type of afferent input the injured spinal cord receives. Here we review preclinical and clinical input parameters fostering adaptive plasticity, as well as those producing maladaptive plasticity that may undermine neurorehabilitative efforts. We differentiate between passive (hindlimb unloading [HU], limb immobilization) and active (peripheral nociception) forms of aberrant input. Furthermore, we discuss the timing of initiating exposure to afferent input after SCI for promoting functional locomotor recovery. We conclude by presenting a candidate rapid synaptic mechanism for maladaptive plasticity after SCI, offering a pharmacological target for restoring the capacity for adaptive spinal plasticity in real time.