Locomotor improvement of spinal cord-injured rats through treadmill training by forced plantar placement of hind paws

Exoskeleton-Assisted Rehabilitation and Neuroplasticity in Spinal Cord Injury

Spinal cord injury (SCI) results in neurological deficits below the level of injury, causing motor dysfunction and various severe multisystem complications. Rehabilitative training plays a crucial role in the recovery of individuals with SCI, and exoskeleton serves as an emerging and promising tool for rehabilitation, especially in promoting neuroplasticity and alleviating SCI-related complications. This article reviews the classifications and research progresses of medical exoskeletons designed for SCI patients and describes their performances in practical application separately. Meanwhile, we discuss their mechanisms for enhancing neuroplasticity and functional remodeling, as well as their palliative impacts on secondary complications. The potential trends in exoskeleton design are raised according to current progress and requirements on SCI rehabilitation.

The Impact of Treadmill Training on Tissue Integrity, Axon Growth, and Astrocyte Modulation

Spinal cord injury (SCI) presents a complex challenge in neurorehabilitation, demanding innovative therapeutic strategies to facilitate functional recovery. This study investigates the effects of treadmill training on SCI recovery, emphasizing motor function enhancement, neural tissue preservation, and axonal growth. Our research, conducted on a rat model, demonstrates that controlled treadmill exercises significantly improve motor functions post-SCI, as evidenced by improved scores on the Basso, Beattie, and Bresnahan (BBB) locomotor rating scale and enhanced electromyography readings. Notably, the training facilitates the preservation of spinal cord tissue, effectively reducing secondary damage and promoting the maintenance of neural fibers in the injured area. A key finding is the significant stimulation of axonal growth around the injury epicenter in trained rats, marked by increased growth-associated protein 43 (GAP43) expression. Despite these advancements, the study notes a limited impact of treadmill training on motoneuron adaptation and highlights minimal changes in the astrocyte and neuron-glial antigen 2 (NG2) response. This suggests that, while treadmill training is instrumental in functional improvements post-SCI, its influence on certain neural cell types and glial populations is constrained.

Krishnan L, Abelson KSP. Refinement of the motorised laminectomy-assisted rat spinal cord injury model by analgesic treatment

Usage and reporting of analgesia in animal models of spinal cord injury (SCI) have been sparse and requires proper attention. The majority of experimental SCI research uses rats as an animal model. This study aimed to probe into the effects of some commonly used regimens with NSAIDs and opioids on well-being of the rats as well as on the functional outcome of the model. This eight-week study used forty-two female Wistar rats (Crl: WI), randomly and equally divided into 6 treatment groups, viz. I) tramadol (5mg/kg) and buprenorphine (0.05mg/kg); II) carprofen (5mg/kg) and buprenorphine (0.05mg/kg); III) carprofen (5mg/kg); IV) meloxicam (1mg/kg) and buprenorphine (0.05mg/kg); V) meloxicam (1mg/kg); and VI) no analgesia (0.5 ml sterile saline). Buprenorphine was administered twice daily whereas other treatments were given once daily for five days post-operatively. Injections were given subcutaneously. All animals underwent dental burr-assisted laminectomy at the T10-T11 vertebra level. A custom-built calibrated spring-loaded 200 kilodynes force deliverer was used to induce severe SCI. Weekly body weight scores, Rat Grimace Scale (RGS), and dark-phase home cage activity were used as markers for well-being. Weekly Basso Beattie and Bresnahan (BBB) scores served as markers for functionality together with Novel Object Recognition test (NOR) at week 8 and terminal histopathology using area of vacuolisation and live neuronal count from the ventral horns of spinal cord. It was concluded that the usage of analgesia improved animal wellbeing while having no effects on the functional aspects of the animal model in comparison to the animals that received no analgesics.

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.

Effect of a Corset on the Gait of Healthy Beagle Dogs

Simple Summary

In recent years, corsets have been used in the prevention of nerve diseases in dogs and in their rehabilitation following surgery. The Anifull Dog’s Corset Pro, made by Daiya Industry Co., Ltd., is manufactured and sold for this purpose, but no studies have yet been conducted to verify its effectiveness. To evaluate the effects of the corset, we analyzed the gait of healthy beagle dogs that were or were not wearing the Anifull Dog’s Corset Pro. We found no difference in the walking speed of the dogs, but wearing the corset reduced the horizontal sway of the back. In conclusion, this corset does not affect the gait of dogs and may help body stability. Therefore, the Anifull Dog’s Corset Pro may be useful for the treatment of dog nerve conditions.

Abstract

The prognosis for intervertebral disc disease (IVDD), a common neurologic disease in dogs, varies, with some cases requiring long-term rehabilitation. Corsets are used as part of the physical rehabilitation of dogs, and one of these, the Anifull Dog’s Corset Pro, is manufactured and sold by Daiya Industry Co., Ltd. This corset is used to relieve pain caused by spinal cord and vertebral diseases, and to prevent neurological conditions from worsening, by limiting spinal movement. However, the effect of the Anifull Dog’s Corset Pro on gait has not yet been clarified. Therefore, we aimed to evaluate the effects of this corset on the gait of dogs using kinematic and kinetic analyses. Five healthy beagle dogs wearing corsets were trotted, kinematic and kinetic parameters were measured using motion capture and force plates, and the results were compared to those obtained when the dogs were not wearing a corset. The range of motion of the angle formed by the 13th thoracic vertebra and the 7th lumbar vertebra at the apex of the 7th cervical vertebra was significantly reduced in the corset-wearing dogs. Thus, the Anifull Dog’s Corset Pro may improve trunk stability without affecting gait.

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.

Water treadmill training protects the integrity of the blood-spinal cord barrier following SCI via the BDNF/TrkB-CREB signalling pathway

Following spinal cord injury (SCI), destruction of the blood-spinal cord barrier (BSCB) leads to increased microvascular permeability and tissue oedema. The BSCB, formed by a dense network of tight junctions (TJs) and adhesion junctions (AJs) is considered a therapeutic target. Most studies have focused on the effect of drug therapy on the neurovascular system after SCI, ignoring the protection and functional recovery of the vascular system by exercise training. Previously, we indicated that water treadmill training (TT) has a protective effect on the BSCB after SCI, but the specific molecular mechanism of the effect of TT on BSCB is still not clear. In this study, we used a specific inhibitor of TrkB (ANA-12) to explore whether the BDNF/TrkB-CREB signalling pathway is involved in TT-mediated BSCB protection after SCI. A New York University (NYU) impactor was used to establish the SCI model. Rats in the SI (Sham + ANA-12), IM (SCI + ANA-12) and ITM (SCI + TT + ANA-12) groups were injected with ANA-12 (0.5 mg/kg) daily, and rats in TM (SCI + TT) and ITM (SCI + TT + ANA-12) groups were treated with water TT for 7 or 14 d. The degree of neurological deficit, water content, BSCB permeability, protein expression and ultrastructure of vascular endothelial cells were assessed by the Basso-Beattie-Bresnahan (BBB) motor rating scale, Evans blue (EB), Western blot (WB) experiments, immunofluorescence and transmission electron microscopy (TEM). Our results suggest that TT upregulates the BDNF/TrkB-CREB signalling pathway following SCI. The BDNF/TrkB-CREB signalling pathway is involved in the protection of the BSCB. Application of the inhibitor blocked the protective effect of TT on the BSCB. We concluded that TT ameliorated SCI-induced BSCB impairment by upregulating the BDNF/TrkB-CREB signalling pathways.

Combined treatment with enteric neural stem cells and chondroitinase ABC reduces spinal cord lesion pathology

BACKGROUND

Spinal cord injury (SCI) presents a significant challenge for the field of neurotherapeutics. Stem cells have shown promise in replenishing the cells lost to the injury process, but the release of axon growth-inhibitory molecules such as chondroitin sulfate proteoglycans (CSPGs) by activated cells within the injury site hinders the integration of transplanted cells. We hypothesised that simultaneous application of enteric neural stem cells (ENSCs) isolated from the gastrointestinal tract, with a lentivirus (LV) containing the enzyme chondroitinase ABC (ChABC), would enhance the regenerative potential of ENSCs after transplantation into the injured spinal cord.

METHODS

ENSCs were harvested from the GI tract of p7 rats, expanded in vitro and characterised. Adult rats bearing a contusion injury were randomly assigned to one of four groups: no treatment, LV-ChABC injection only, ENSC transplantation only or ENSC transplantation+LV-ChABC injection. After 16 weeks, rats were sacrificed and the harvested spinal cords examined for evidence of repair.

RESULTS

ENSC cultures contained a variety of neuronal subtypes suitable for replenishing cells lost through SCI. Following injury, transplanted ENSC-derived cells survived and ChABC successfully degraded CSPGs. We observed significant reductions in the injured tissue and cavity area, with the greatest improvements seen in the combined treatment group. ENSC-derived cells extended projections across the injury site into both the rostral and caudal host spinal cord, and ENSC transplantation significantly increased the number of cells extending axons across the injury site. Furthermore, the combined treatment resulted in a modest, but significant functional improvement by week 16, and we found no evidence of the spread of transplanted cells to ectopic locations or formation of tumours.

CONCLUSIONS

Regenerative effects of a combined treatment with ENSCs and ChABC surpassed either treatment alone, highlighting the importance of further research into combinatorial therapies for SCI. Our work provides evidence that stem cells taken from the adult gastrointestinal tract, an easily accessible source for autologous transplantation, could be strongly considered for the repair of central nervous system disorders.

Water treadmill training attenuates blood-spinal cord barrier disruption in rats by promoting angiogenesis and inhibiting matrix metalloproteinase-2/9 expression following spinal cord injury

Background

The permeability of the blood-spinal cord barrier (BSCB) is mainly determined by junction complexes between adjacent endothelial cells (ECs), including tight junctions (TJs) and adherens junctions (AJs), which can be severely damaged after spinal cord injury (SCI). Exercise training is a recognized method for the treatment of SCI. The destruction of the BSCB mediated by matrix metalloproteinases (MMPs) leads to inflammation, neurotoxin production, and neuronal apoptosis. The failure of new blood vessels to effectively regenerate is also an important cause of delayed recovery after SCI. For the first time, we introduced water treadmill training (TT) to help SCI rats successfully exercise and measured the effects of TT in promoting recovery after SCI and the possible mechanisms involved.

Methods

Sprague-Dawley (200–250 g) rats were randomly divided into the following three groups: sham operated, SCI, and SCI + TT. Animals were sacrificed at 7 or 14 days post-surgery. The degree of neurological deficit, tissue morphology and BSCB permeability were assessed by the Basso-Beattie-Bresnahan (BBB) motor function scale and appropriate staining protocols, and apoptosis, protein expression and vascular EC ultrastructure were assessed by TUNEL staining, Western blotting, immunofluorescence and transmission electron microscopy (TEM).

Results

Our experiments showed that TT reduced permeability of the BSCB and decreased structural tissue damage. TT significantly improved functional recovery when compared with that in the SCI group; TJ and AJ proteins expression increased significantly after TT, and training reduced apoptosis induced by SCI. TT could promote angiogenesis, and MMP-2 and MMP-9 expression was significantly inhibited by TT.

Conclusions

The results of this study indicate that TT promotes functional recovery for the following reasons: TT (1) protects residual BSCB structure from further damage, (2) promotes vascular regeneration, and (3) inhibits MMP-2/9 expression to mitigate BSCB damage.

Multimodal treatment for spinal cord injury: a sword of neuroregeneration upon neuromodulation

Spinal cord injury is linked to the interruption of neural pathways, which results in irreversible neural dysfunction. Neural repair and neuroregeneration are critical goals and issues for rehabilitation in spinal cord injury, which require neural stem cell repair and multimodal neuromodulation techniques involving personalized rehabilitation strategies. Besides the involvement of endogenous stem cells in neurogenesis and neural repair, exogenous neural stem cell transplantation is an emerging effective method for repairing and replacing damaged tissues in central nervous system diseases. However, to ensure that endogenous or exogenous neural stem cells truly participate in neural repair following spinal cord injury, appropriate interventional measures (e.g., neuromodulation) should be adopted. Neuromodulation techniques, such as noninvasive magnetic stimulation and electrical stimulation, have been safely applied in many neuropsychiatric diseases. There is increasing evidence to suggest that neuromagnetic/electrical modulation promotes neuroregeneration and neural repair by affecting signaling in the nervous system; namely, by exciting, inhibiting, or regulating neuronal and neural network activities to improve motor function and motor learning following spinal cord injury. Several studies have indicated that fine motor skill rehabilitation training makes use of residual nerve fibers for collateral growth, encourages the formation of new synaptic connections to promote neural plasticity, and improves motor function recovery in patients with spinal cord injury. With the development of biomaterial technology and biomechanical engineering, several emerging treatments have been developed, such as robots, brain-computer interfaces, and nanomaterials. These treatments have the potential to help millions of patients suffering from motor dysfunction caused by spinal cord injury. However, large-scale clinical trials need to be conducted to validate their efficacy. This review evaluated the efficacy of neural stem cells and magnetic or electrical stimulation combined with rehabilitation training and intelligent therapies for spinal cord injury according to existing evidence, to build up a multimodal treatment strategy of spinal cord injury to enhance nerve repair and regeneration.

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.

Astrocyte-selective AAV-ADAMTS4 gene therapy combined with hindlimb rehabilitation promotes functional recovery after spinal cord injury

Chondroitin sulphate proteoglycans (CSPGs) are inhibitors to axon regeneration and plasticity. A disintegrin and metalloproteinase with thrombospondin motifs-4 (ADAMTS4) is a human enzyme that catalyses the proteolysis of CSPG protein cores. Infusion of ADAMTS4 into the damaged spinal cord was previously shown to improve functional recovery SCI, however, this therapy is limited in its enzyme form. Adeno-associated viral (AAV) vector gene therapy has emerged as the vector of choice for safe, robust and long-term transgene expression in the central nervous system. Here, an AAV expression cassette containing ADAMTS4 under the control of the astrocytic GfaABC₁D promoter was packaged into an AAV5 vector. Sustained expression of ADAMTS4 was achieved in vitro and in vivo leading to degradation of CSPGs. Compared to a contusion only group, AAV-ADAMTS4 resulted in significantly decreased lesion size, increased sprouting of hindlimb corticospinal tract axons, increased serotonergic fiber density caudal to a contusive spinal cord injury. Hindlimb-specific exercise rehabilitation was used to drive neuroplasticity towards improving functional connections. The combination of hindlimb rehabilitation with AAV-ADAMTS4 led to functional recovery after SCI compared to a contusion only group. Thus, long-term degradation of CSPGs through AAV-ADAMTS4 gene therapy in a combinational approach with rehabilitation represents a candidate for further preclinical development.

5-Nonyloxytryptamine oxalate-embedded collagen-laminin scaffolds augment functional recovery after spinal cord injury in mice

Polysialic acid (PSA) is crucial for the induction and maintenance of nervous system plasticity and repair after injury. In order to exploit the immense therapeutic potential of PSA, previous studies have focused on the identification and development of peptide-based or synthetic PSA mimetics. 5-Nonyloxytryptamine (5-NOT) has been previously reported as a PSA-mimicking compound for promoting functional recovery after spinal cord injury in mice. In order to explore the neuroregeneration potential of 5-NOT, the current study was based on a biomaterial approach using collagen-laminin (C/L) scaffolds. In in vitro studies, 5-NOT was observed to promote neurite outgrowth, migration, and fasciculation in cerebellar neuronal cells, whereas in 3D cell cultures it showed more ramification and complex Sholl profiles. 5-NOT promoted the survival and neurite length of cortical neurons when cocultured with glutamate-challenged astrocytes. In in vivo studies, spinal cord compression injury mice were used with immediate application of C/L hydrogels impregnated with 5-NOT. C/L + 5-NOT-treated mice demonstrated ∼75% of motor recovery 14 days after injury. Furthermore, this effect was shown to be dependent on the ERK-MAPK pathway and augmentation of cell survival. Thus, based on a biomaterial approach, our current study provides new insight for 5-NOT-containing hydrogels as a promising candidate to speed up recovery after central nervous system injuries.

Intramuscular Injection of Adenoassociated Virus Encoding Human Neurotrophic Factor 3 and Exercise Intervention Contribute to Reduce Spasms after Spinal Cord Injury

Limb spasms are phenomena of hyperreflexia that occur after spinal cord injury. Currently, the clinical treatment is less than ideal. Our goal is to develop a combination therapy based on individualized medicine to reduce spasticity after spinal cord injury. In this study, rats received a severe contusive injury at the T9 segment of the spinal cord, followed by gene therapy with adenoassociated virus encoding human neurotrophic factor 3 (AAV-NT3) and a 2-week exercise program starting at 4 weeks after injury. We quantified the frequency of spasms during a swimming test at 4 and 6 weeks after injury and confirmed the results of the swimming test by measuring the H-reflex of the plantar muscle. We obtained weekly hind limb exercise scores to assess the effect of the interventions in hind limb motor function improvement. Then, we used immunofluorescence to observe the immunoreactivity of spinal motor neurons, synaptophysin, cholinergic interneurons, and GABAergic interneurons. We also measured the expression of KCC2 in the spinal cord by western blot. We found that AAV-NT3 gene therapy, exercise, and combination therapy all attenuated the frequency of spasms in the swimming test conducted at 6 weeks after spinal cord injury and increased rate-dependent depression of H-reflex. Combination therapy was significantly superior to AAV-NT3 alone in protecting motor neurons. Recovery of KCC2 expression was significantly greater in rats treated with combination therapy than in the exercise group. Combination therapy was also significantly superior to individual therapies in remodeling spinal cord neurons. Our study shows that the combination of AAV-NT3 gene therapy and exercise can alleviate muscle spasm after spinal cord injury by altering the excitability of spinal interneurons and motor neurons. However, combination therapy did not show a significant additive effect, which needs to be improved by adjusting the combined strategy.

Rehabilitation following spinal cord injury: how animal models can help our understanding of exercise-induced neuroplasticity

Spinal cord injury is a devastating condition that is followed by long and often unsuccessful recovery after trauma. The state of the art approach to manage paralysis and concomitant impairments is rehabilitation, which is the only strategy that has proven to be effective and beneficial for the patients over the last decades. How rehabilitation influences the remodeling of spinal axonal connections in patients is important to understand, in order to better target these changes and define the optimal timing and onset of training. While clinically the answers to these questions remain difficult to obtain, rodent models of rehabilitation like bicycling, treadmill training, swimming, enriched environments or wheel running that mimic clinical rehabilitation can be helpful to reveal the axonal changes underlying motor recovery. This review will focus on the different animal models of spinal cord injury rehabilitation and the underlying changes in neuronal networks that are improved by exercise and rehabilitation.

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.

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.

Effects of Treadmill Training Combined with Serotonergic Interventions on Spasticity after Contusive Spinal Cord Injury

Spasticity usually emerges during the course of recovery from spinal cord injury (SCI). While medications and physical rehabilitation are prescribed to alleviate spastic symptoms, the insufficiency of their effects remains an important problem to be addressed. Given the challenges associated with increasing the dose of medication, we hypothesized that a combination therapy with medication and physical rehabilitation can be effective. Therefore, we examined the effects of treadmill training (TMT) along with serotonergic medication using a spastic rat model after contusive injury. Spasticity-strong SCI rats were selected 4 weeks after SCI and received one of the following interventions for 2 weeks: only TMT, TMT with fluoxetine (a selective serotonin re-uptake inhibitor), TMT with cyproheptadine (a 5-HT₂ receptor antagonist), only fluoxetine, or only cyproheptadine. We performed the swimming test to quantify the frequency of spastic behaviors. We also evaluated hindlimb locomotor functions every week. At the end of the intervention, we examined the Hoffman reflex from the plantar muscle and the immunoreactivity of the 5-HT_2A receptor in spinal cord tissues. While the TMT group and cyproheptadine-treated groups showed decreased spastic behaviors and reduction in spinal hyperreflexia, the fluoxetine-treated group showed the opposite effect, even with TMT. Moreover, TMT suppressed the expression of the 5-HT_2A receptor in the lumbar spinal motor neurons, while cyproheptadine treatment did not change it. We did not observe any differences in locomotor functions between the groups. Taken together, our findings indicate that TMT and cyproheptadine significantly alleviated spastic symptoms, but did not show synergistic or additive effects.

Effects of Transplanted Heparin-Poloxamer Hydrogel Combining Dental Pulp Stem Cells and bFGF on Spinal Cord Injury Repair

Spinal cord injury (SCI) is one of serious traumatic diseases of the central nervous system and has no effective treatment because of its complicated pathophysiology. Tissue engineering strategy which contains scaffolds, cells, and growth factors can provide a promising treatment for SCI. Hydrogel that has 3D network structure and biomimetic microenvironment can support cellular growth and embed biological macromolecules for sustaining release. Dental pulp stem cells (DPSCs), derived from cranial neural crest, possess mesenchymal stem cell (MSC) characteristics and have an ability to provide neuroprotective and neurotrophic properties for SCI treatment. Basic fibroblast growth factor (bFGF) is able to promote cell survival and proliferation and also has beneficial effect on neural regeneration and functional recovery after SCI. Herein, a thermosensitive heparin-poloxamer (HP) hydrogel containing DPSCs and bFGF was prepared, and the effects of HP-bFGF-DPSCs on neuron restoration after SCI were evaluated by functional recovery tests, western blotting, magnetic resonance imaging (MRI), histology evaluation, and immunohistochemistry. The results suggested that transplanted HP hydrogel containing DPSCs and bFGF had a significant impact on spinal cord repair and regeneration and may provide a promising strategy for neuron repair, functional recovery, and tissue regeneration after SCI.