Locomotor Recovery Research Articles

Small extracellular vesicles released by infused mesenchymal stromal cells target M2 macrophages and promote TGF-β upregulation, microvascular stabilization and functional recovery in a rodent model of severe spinal cord injury.

Intravenous (IV) infusion of bone marrow‐derived mesenchymal stem/stromal cells (MSCs) stabilizes the blood‐spinal cord barrier (BSCB) and improves functional recovery in experimental models of spinal cord injury (SCI). Although IV delivered MSCs do not traffic to the injury site, IV delivered small extracellular vesicles (sEVs) derived from MSCs (MSC‐sEVs) do and are taken up by a subset of M2 macrophages. To test whether sEVs released by MSCs are responsible for the therapeutic effects of MSCs, we tracked sEVs produced by IV delivered DiR‐labelled MSCs (DiR‐MSCs) after transplantation into SCI rats. We found that sEVs were released by MSCs in vivo, trafficked to the injury site, associated specifically with M2 macrophages and co‐localized with exosome markers. Furthermore, while a single MSC injection was sufficient to improve locomotor recovery, fractionated dosing of MSC‐sEVs over 3 days (F‐sEVs) was required to achieve similar therapeutic effects. Infusion of F‐sEVs mimicked the effects of single dose MSC infusion on multiple parameters including: increased expression of M2 macrophage markers, upregulation of transforming growth factor‐beta (TGF‐β), TGF‐β receptors and tight junction proteins, and reduction in BSCB permeability. These data suggest that release of sEVs by MSCs over time induces a cascade of cellular responses leading to improved functional recovery.

Contralateral Axon Sprouting but Not Ipsilateral Regeneration Is Responsible for Spontaneous Locomotor Recovery Post Spinal Cord Hemisection

Spinal cord injury (SCI) usually results in permanent functional impairment and is considered a worldwide medical problem. However, both motor and sensory functions can spontaneously recover to varying extents in humans and animals with incomplete SCI. This study observed a significant spontaneous hindlimb locomotor recovery in Sprague-Dawley rats at four weeks after post-right-side spinal cord hemisection at thoracic 8 (T8). To verify whether the above spontaneous recovery derives from the ipsilateral axonal or neuronal regeneration to reconnect the lesion site, we resected either the scar tissue or right side T7 spinal cord at five weeks post-T8 hemisected injury. The results showed that the spontaneously achieved right hindlimb locomotor function had little change after resection. Furthermore, when T7 left hemisection was performed five weeks after the initial injury, the spontaneously achieved right hindlimb locomotor function was dramatically abolished. A similar result could also be observed when T7 transection was performed after the initial hemisection. The results indicated that it might be the contralateral axonal remolding rather than the ipsilateral axonal or neuronal regeneration beyond the lesion site responsible for the spontaneous hindlimb locomotor recovery. The immunostaining analyses and corticospinal tracts (CSTs) tracing results confirmed this hypothesis. We detected no substantial neuronal and CST regeneration throughout the lesion site; however, significantly more CST fibers were observed to sprout from the contralateral side at the lumbar 4 (L4) spinal cord in the hemisection model rats than in intact ones. In conclusion, this study verified that contralateral CST sprouting, but not ipsilateral CST or neuronal regeneration, is primarily responsible for the spontaneous locomotor recovery in hemisection SCI rats.

Engineered basic fibroblast growth factor-overexpressing human umbilical cord-derived mesenchymal stem cells improve the proliferation and neuronal differentiation of endogenous neural stem cells and functional recovery of spinal cord injury by activating the PI3K-Akt-GSK-3\u03b2 signaling pathway

ObjectivesTo investigate the safety for clinic use and therapeutic effects of basic fibroblast growth factor (bFGF)-overexpressing human umbilical cord-derived mesenchymal stem cells (HUCMSCs) in mice with completely transected spinal cord injury (SCI).MethodsStable bFGF-overexpressing HUCMSCs clones were established by electrotransfection and then subjected to systematic safety evaluations. Then, bFGF-overexpressing and control HUCMSCs were used to treat mice with completely transected SCI by tail intravenous injection. Therapeutic outcomes were then investigated, including functional recovery of locomotion, histological structures, nerve regeneration, and recovery mechanisms.ResultsStable bFGF-overexpressing HUCMSCs met the standards and safety of MSCs for clinic use. In the mouse SCI model, stable bFGF-overexpressing HUCMSCs markedly improved therapeutic outcomes such as reducing glial scar formation, improving nerve regeneration and proliferation of endogenous neural stem cells (NSCs), and increasing locomotion functional recovery of posterior limbs compared with the control HUCMSCs group. Furthermore, bFGF-overexpressing HUCMSCs promoted the proliferation and neuronal differentiation of NSCs in vitro through the PI3K-Akt-GSK-3β pathway.ConclusionbFGF-overexpressing HUCMSCs meet the requirements of clinical MSCs and improve evident therapeutic outcomes of mouse SCI treatment, which firmly supports the safety and efficacy of gene-modified MSCs for clinical application.

Surgical Aspects of the Possover LION Procedure: An Emerging Procedure for Recovery of Visceral Functions and Locomotion in Paraplegics

Surgical Aspects of the Possover LION Procedure: An Emerging Procedure for Recovery of Visceral Functions and Locomotion in Paraplegics

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.

Disrupting RhoA activity by blocking Arhgef3 expression mitigates microglia-induced neuroinflammation post spinal cord contusion

Excess inflammatory microglia activation deteriorates the pathological degree of spinal cord injury (SCI). We here employed microglia samples in vitro and murine model in vivo to trace the role of inhibition of Arhgef3 in inflammatory response post SCI. From the specimen analysis of lipopolysaccharide (LPS)-induced inflammatory microglia, we found that Arhgef3 expression was positively relative to microglia activation. In vitro, LPS caused the microglia inflammatory activation and induced upregulation of the Arhgef3 expression. Interestingly, presence of Arhgef3 could activate RhoA through promoting Rho GTPases, but silencing of Arhgef3 decreased RhoA activation and inhibited the microglia inflammation. Moreover, disruption of Arhgef3 inhibited the GTP-RhoA, resulted in a suppression of proinflammatory cytokines, and alleviated the LPS-elicited inflammatory genes expression. Moreover, artificially decreasing Arhgef3 expression remarkedly reduced ROS generation after LPS treatment. In vivo of a mouse mechanical contusion-induced SCI model, inhibition of Arhgef3 reduced the ratio of GTP-RhoA/Total-RhoA, and prevented SCI via mitigating the microglial inflammatory phenotype and decreased secondary neurological injury. Besides, inhibition of Arhgef3 prevented alleviated the degree of demyelination but did not affect neuronal regeneration. Meaningfully, absence of Arhgef3 improved mouse locomotor recovery post SCI. Taken together, Arhgef3 involves the microglial activation and inflammatory response following neural injury, and targeted disrupting of which may indicate a promising therapeutic direction in preventing SCI.

Adequate expression of neuropeptide Y is essential for the recovery of zebrafish motor function following spinal cord injury

In strong contrast to limited repair within the mammalian central nervous system, the spinal cord of adult zebrafish is capable of almost complete recovery following injury. Understanding the mechanism underlying neural repair and functional recovery in zebrafish may lead to innovative therapies for human spinal cord injury (SCI). Since neuropeptide Y (NPY) plays a protective role in the pathogenesis of several neurological diseases, in the present study, we evaluated the effects of NPY on neuronal repair and subsequent recovery of motor function in adult zebrafish following SCI. Real-time quantitative PCR (qRT-PCR), in situ hybridization and immunostaining for NPY revealed decreased NPY expression at 12 hours (h), 6 and 21 days (d) after SCI. Double-immunostaining for NPY and islet-1, a motoneuron marker, showed that NPY was expressed in spinal cord motoneurons. Morpholino (MO) treatment for suppressing the expression of NPY inhibited supraspinal axon regrowth and locomotor recovery, in which double-staining for proliferating cell nuclear antigen (PCNA) and islet-1 showed a reduction in motoneuron proliferation. Similarly, a downregulated mRNA level of Y1 receptor of NPY (NPY1R) was also detected at 12 h, 6 and 21 d after injury. Immunostaining for NPY and in situ hybridization for NPY1R revealed that NPY1R was co-localized with NPY. Collectively, the results suggest that NPY expression in motoneurons promotes descending axon regeneration and locomotor recovery in adult zebrafish after SCI, possibly by regulating motoneuron proliferation through activation of NPY1R.

Locomotor recovery after spinal cord injury: intimate dependence between axonal regeneration and re-connection.

Locomotor recovery after spinal cord injury: intimate dependence between axonal regeneration and re-connection.

Skilled reach training enhances robotic gait training to restore overground locomotion following spinal cord injury in rats

Rehabilitative training has been shown to improve motor function following spinal cord injury (SCI). Unfortunately, these gains are primarily task specific; where reach training only improves reaching, step training only improves stepping and stand training only improves standing. More troublesome is the tendency that the improvement in a trained task often comes at the expense of an untrained task. However, the task specificity of training does not preclude the benefits of combined rehabilitative training. Here we show that robot assisted gait training alone can partially reduce the deficits in unassisted overground locomotion following a C4/5 overhemisection injury in rats. When robot-assisted gait training is done in conjunction with skilled forelimb training, we observe a much greater level of recovery of unassisted overground locomotion. In order to provide reach training that would not interfere with our robotic gait training schedule, we prompted rats to increase the use of their forelimbs by replacing the standard overhead feeder with a custom made, deep welled hopper that dispensed nutritionally equivalent small milled pellets. We speculate that the increase in recovery from combined training is due to a more robust interneuronal relay network around the injury site. in vivo manganese-enhanced magnetic resonance imaging of the spinal cord indicated that there was no increase in the cellular activity, however ex vivo diffusion tensor imaging (DTI) suggested an increase in collateralization around the injury site in rats that received both reach training and robot assisted gait training.

Activation of Neuroprotective Microglia and Astrocytes at the Lesion Site and in the Adjacent Segments Is Crucial for Spontaneous Locomotor Recovery after Spinal Cord Injury.

Microglia and astrocytes play an important role in the regulation of immune responses under various pathological conditions. To detect environmental cues associated with the transformation of reactive microglia (M1) and astrocytes (A1) into their polarization states (anti-inflammatory M2 and A2 phenotypes), we studied time-dependent gene expression in naive and injured spinal cord. The relationship between astrocytes and microglia and their polarization states were studied in a rat model after Th9 compression (40 g/15 min) in acute and subacute stages at the lesion site, and both cranially and caudally. The gene expression of microglia/macrophages and M1 microglia was strongly up-regulated at the lesion site and caudally one week after SCI, and attenuated after two weeks post-SCI. GFAP and S100B, and A1 astrocytes were profoundly expressed predominantly two weeks post-SCI at lesion site and cranially. Gene expression of anti-inflammatory M2a microglia (CD206, CHICHI, IL1rn, Arg-1), M2c microglia (TGF-β, SOCS3, IL4R α) and A2 astrocytes (Tgm1, Ptx3, CD109) was greatly activated at the lesion site one week post-SCI. In addition, we observed positive correlation between neurological outcome and expression of M2a, M2c, and A2 markers. Our findings indicate that the first week post-injury is critical for modulation of reactive microglia/astrocytes into their neuroprotective phenotypes.

Galvanic Vestibular Stimulation Improves Spatial Cognition After Unilateral Labyrinthectomy in Mice.

Objectives: To investigate the deficits of spatial memory and navigation from unilateral vestibular deafferentation (UVD) and to determine the efficacy of galvanic vestibular stimulation (GVS) for recovery from these deficits using a mouse model of unilateral labyrinthectomy (UL).Methods: Thirty-six male C57BL/6 mice were allocated into three groups that comprise a control group and two experimental groups, UVD with (GVS group) and without GVS intervention (non-GVS group). In the experimental groups, we assessed the locomotor and cognitive behavioral function before (baseline) and 3, 7, and 14 days after surgical UL, using the open field (OF), Y maze, and Morris water maze (MWM) tests. In the GVS group, the stimulations were applied for 30 min daily from postoperative day (POD) 0–4 via the electrodes inserted subcutaneously close to both bony labyrinths.Results: Locomotion and spatial cognition were significantly impaired in the mice with UVD non-GVS group compared to the control group. GVS significantly accelerated recovery of locomotion compared to the control and non-GVS groups on PODs 3 (p < 0.001) and 7 (p < 0.05, Kruskal–Wallis and Mann–Whitney U tests) in the OF and Y maze tests. The mice in the GVS group were better in spatial working memory assessed with spontaneous alternation performance and spatial reference memory assessed with place recognition during the Y maze test than those in the non-GVS group on POD 3 (p < 0.001). In addition, the recovery of long-term spatial navigation deficits during the MWM, as indicated by the escape latency and the probe trial, was significantly better in the GVS group than in the non-GVS group 2 weeks after UVD (p < 0.01).Conclusions: UVD impairs spatial memory, navigation, and motor coordination. GVS accelerated recoveries in short- and long-term spatial memory and navigation, as well as locomotor function in mice with UVD, and may be applied to the patients with acute unilateral vestibular failure.

Oscillating field stimulation promotes recovery from spinal cord injury in rats by regulating the differentiation of endogenous neural stem cells.

The mammalian spinal cord (SC) has a limited self-repair capacity and exogenous treatments are yet to produce substantial functional recovery following SC injury (SCI). The SC contains endogenous neural stem cells (NSCs) with multi-lineage differentiation potential and it may be possible to restore function via interventions that promote NSC differentiation following SCI. Oscillating field stimulation (OFS) has been reported to regulate the Wnt signaling pathway, a known modulator of NSC differentiation. However, the effects of OFS on NSC differentiation following SCI and associated functional recovery have not been previously examined. In the current study, the Basso-Beattie-Bresnahan (BBB) score was used to assess locomotion recovery following SCI in rats and immunofluorescence double-staining was used to examine the regeneration of neurons and oligodendrocytes derived from NSCs. Furthermore, Nissl staining was performed to assess the viability and survival of neurons following SCI, while recovery of the myelin sheath was examined by uranium-lead staining under transmission electron microscopy. OFS delivered via an implanted stimulator enhanced the differentiation of NSCs into neurons and oligodendrocytes and accelerated the regeneration of myelinated axons. Additionally, BBB scores revealed superior locomotion recovery in OFS-treated rats compared with SCI controls. Collectively, these results indicated that OFS may be a feasible strategy to promote SCI recovery by regulating the differentiation of endogenous NSCs.

Transneuronal delivery of designer cytokines: perspectives for spinal cord injury.

Transneuronal delivery of designer cytokines: perspectives for spinal cord injury.

Extracorporeal shockwave therapy in spinal cord injury, early to advance to clinical trials? A systematic review and meta-analysis on animal studies.

As there is no consensus over the efficacy of extracorporeal shockwave therapy in the management of spinal cord injury complications, the current meta-analysis aims to investigate preclinical evidence on the matter. The search strategy was developed based on keywords related to 'spinal cord injury' and 'extracorporeal shockwave therapy'. A primary search was conducted in Medline, Embase, Scopus and Web of Science until the end of 2020. Studies which administered extracorporeal shockwave therapy on spinal cord injury animal models and evaluated motor function and/or histological findings were included. The standardised mean difference with a 95% confidence interval (CI) were calculated. Seven articles were included. Locomotion was significantly improved in the extracorporeal shockwave therapy treated group (standardised mean difference 1.68, 95% CI 1.05-2.31, P=0.032). It seems that the efficacy of extracorporeal shockwave therapy with an energy flux density of 0.1 mJ/mm2 is higher than 0.04 mJ/mm2 (P=0.044). Shockwave therapy was found to increase axonal sprouting (standardised mean difference 1.31, 95% CI 0.65, 1.96), vascular endothelial growth factor tissue levels (standardised mean difference 1.36, 95% CI 0.54, 2.18) and cell survival (standardised mean difference 2.49, 95% CI 0.93, 4.04). It also significantly prevents axonal degeneration (standardised mean difference 2.25, 95% CI 1.47, 3.02). Extracorporeal shockwave therapy significantly improves locomotor recovery in spinal cord injury animal models through neural tissue regeneration. Nonetheless, in spite of the promising results and clinical application of extracorporeal shockwave therapy in various conditions, current evidence implies that designing clinical trials on extracorporeal shockwave therapy in the management of spinal cord injury may not be soon. Hence, further preclinical studies with the effort to reach the safest and the most efficient treatment protocol are needed.

A Comparison Between Body Weight-Supported Treadmill Training and Conventional Over-Ground Training in Dogs With Incomplete Spinal Cord Injury.

In human medicine there was no evidence registered of a significant difference in recovery between body weight-supported treadmill training (BWSTT) and conventional over-ground (COGI). There isn't any similar study in veterinary medicine. Thus, this study aimed to compare the locomotor recovery obtained in incomplete SCI (T11–L3 Hansen type I) post-surgical dogs following BWSTT or COGI protocols, describing their evolution during 7 weeks in regard to OFS classifications. At admission, dogs were blindly randomized in two groups but all were subjected to the same protocol (underwater treadmill training) for the first 2 weeks. After, they were divided in the BWSTT group (n = 10) and the COGI group (n = 10) for the next 2 weeks, where they performed different training. In both groups locomotor training was accompanied by functional electrical stimulation (FES) protocols. Results reported statistically significant differences between all OFS evaluations time-points (p < 0.001) and between the two groups (p < 0.001). In particular with focus on T1 to T3 a two-way repeated measures ANOVA was performed and similar results were obtained (p = 0.007). Functional recovery was achieved in 90% (17/19) of all dogs and 100% recovered bladder function. The BWSTT group showed 100% (10/10) recovery within a mean time of 4.6 weeks, while the COGI group had 78% (7/9) within 6.1 weeks. Therefore, BWSTT leads to a faster recovery with a better outcome in general.

Viscous field training induces after effects but hinders recovery of overground locomotion following spinal cord injury in rats

Robotic-assisted gait training was able to improve the unassisted overground locomotion of rats following a cervical spinal cord injury. Specifically, four weeks of daily step training in the Robomedica Rodent Robotic Motor Performance System, where the device actively guided the hindlimbs through a pre-injury stepping pattern while the rats walked over a moving treadmill belt in a quadrupedal posture, was able to improve unassisted overground locomotion as measured by the CatWalk gait analysis device. Unfortunately the improvements were minimal. In fact, control animals that received only body weight supported treadmill training and no active robotic forces showed an even greater restoration of unassisted overground locomotion. This led us to further investigate the effects of the specific forces used in rehabilitative training. The robotic training device was modified to apply assistive (negative viscosity) or resistive (viscous) fields in lieu of the standard active guidance. Within the device, daily training with a viscous field resulted in small, constrained steps that were similar to pre-injury steps. However, when the robot was off for weekly assessments, the steps opened up and deviated away from pre-injury levels. Training in a negative viscosity field produced the opposite effect; large open steps that were unlike pre-injury during daily training, and constrained steps that were more like pre-injury during weekly assessment. These training induced after-effects washed out 2 weeks after the cessation of training. Additionally, these distinct after effects seen in the training device did not translate to distinct differences in the recovery of unassisted overground locomotion, with the body weight supported treadmill training controls showing the greatest recovery of overground locomotion. Still, the fact that different applied forces can induce different after effects has interesting implications for rehabilitative training – is it better to have healthy looking steps during training only to induce abnormal after effects, or have abnormal performance during training but with desirable after effects? The data presented here is the first step in addressing this question.

SiRNA in MSC-derived exosomes silences CTGF gene for locomotor recovery in spinal cord injury rats

BackgroundHow to obtain a small interfering RNA (siRNA) vector has become a moot point in recent years. Exosomes (Exo) show advantages of long survival time in vivo, high transmission efficiency, and easy penetration across the blood-spinal cord barrier, renowned as excellent carriers of bioactive substances.MethodsWe applied mesenchymal stem cell (MSC)-derived exosomes as the delivery of synthesized siRNA, which were extracted from rat bone marrow. We constructed exosomes-siRNA (Exo-siRNA) that could specifically silence CTGF gene in the injury sites by electroporation. During the administration, we injected Exo-siRNA into the tail vein of SCI rats,ResultsIn vivo and in vitro experiments showed that Exo-siRNA not only effectively inhibited the expressions of CTGF gene, but quenched inflammation, and thwarted neuronal apoptosis and reactive astrocytes and glial scar formation. Besides, it significantly upregulated several neurotrophic factors and anti-inflammatory factors, acting as a facilitator of locomotor recovery of rats with spinal cord injury (SCI).ConclusionsIn conclusion, this study has combined the thoroughness of gene therapy and the excellent drug-loading characteristics of Exo for the precise treatment of SCI, which will shed new light on the drug-loading field of Exo.

Dl-3-n-butylphthalide Attenuates Spinal Cord Injury via Regulation of MMPs and Junction Proteins in Mice.

As a serious trauma of the neurological system, spinal cord injury (SCI) results in permanent disability, gives rise to immediate vascular damage and a wide range of matters that induce the breakage of blood spinal cord barrier (BSCB). SCI activates the expression of MMP-2/9, which are considered to accelerate the disruption of BSCB. Recent research shows that Dl-3-n-butylphthalide (NBP) exerted protective effects on blood spinal cord barrier in animals after SCI, but the underlying molecular mechanism of NBP on the BSCB undergoing SCI is unknown. Here, our research show that NBP inhibited the expression of MMP-2/9, then improved the permeability of BSCB following SCI. After the T9 level of spinal cord performed with a moderate injury, NBP was managed by intragastric administration and further performed once a day. NBP remarkably improved the permeability of BSCB and junction proteins degration, then promoted locomotion recovery. The protective effect of NBP on BSCB destruction is related to the regulation of MMP-2/9 induced by SCI. Moreover, NBP obviously inhibited the MMP-2/9 expression and junction proteins degradation in microvascular endothelial cells. In conclusion, our results indicate that MMP-2/9 are relevant to the breakdown of BSCB, NBP impairs BSCB destruction through inhibiting MMP-2/9 and promotes functional recovery subjected to SCI. NBP is likely to become a new nominee as a therapeutic to treat SCI via a transigent BSCB.

Chronic inactivation of the contralesional hindlimb motor cortex after thoracic spinal cord hemisection impedes locomotor recovery in the rat

After incomplete spinal cord injury (SCI), cortical plasticity is involved in hindlimb locomotor recovery. Nevertheless, whether cortical activity is required for motor map plasticity and recovery remains unresolved. Here, we combined a unilateral thoracic spinal cord injury (SCI) with a cortical inactivation protocol that uncovered a functional role of contralesional cortical activity in hindlimb recovery and ipsilesional map plasticity. In adult rats, left hindlimb paralysis was induced by sectioning half of the spinal cord at the thoracic level (hemisection) and we used a continuous infusion of muscimol (GABAA agonist, 10 mM, 0.11 µl/h) delivered via implanted osmotic pump (n = 9) to chronically inactivate the contralesional hindlimb motor cortex. Hemisected rats with saline infusion served as a SCI control group (n = 8), and intact rats with muscimol infusion served as an inactivation control group (n = 6). Locomotion was assessed in an open field, on a horizontal ladder, and on a treadmill prior to and for three weeks after hemisection. Cortical inactivation after hemisection significantly impeded hindlimb locomotor recovery in all tasks and specifically disrupted the ability of rats to generate proper flexion of the affected hindlimb during stepping compared to SCI controls, with no significant effect of inactivation in intact rats. Chronic and acute (n = 4) cortical inactivation after hemisection also significantly reduced the representation of the affected hindlimb in the ipsilesional motor cortex derived with intracortical microsimulation (ICMS). Our results provide evidence that residual activity in the contralesional hindlimb motor cortex after thoracic hemisection contributes to spontaneous locomotor recovery and map plasticity.

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.