Effects of chronic baclofen use on active movement in an individual with a spinal cord injury

Multi-session transcutaneous spinal cord stimulation prevents chloride homeostasis imbalance and the development of hyperreflexia after spinal cord injury in rat

Spasticity is a complex and multidimensional disorder that impacts nearly 75% of individuals with spinal cord injury (SCI) and currently lacks adequate treatment options. This sensorimotor condition is burdensome as hyperexcitability of reflex pathways result in exacerbated reflex responses, co-contractions of antagonistic muscles, and involuntary movements. Transcutaneous spinal cord stimulation (tSCS) has become a popular tool in the human SCI research field. The likeliness for this intervention to be successful as a noninvasive anti-spastic therapy after SCI is suggested by a mild and transitory improvement in spastic symptoms following a single stimulation session, but it remains to be determined if repeated tSCS over the course of weeks can produce more profound effects. Despite its popularity, the neuroplasticity induced by tSCS also remains widely unexplored, particularly due to the lack of suitable animal models to investigate this intervention. Thus, the basis of this work was to use tSCS over multiple sessions (multi-session tSCS) in a rat model to target spasticity after SCI and identify the long-term physiological improvements and anatomical neuroplasticity occurring in the spinal cord. Here, we show that multi-session tSCS in rats with an incomplete (severe T9 contusion) SCI (1) decreases hyperreflexia, (2) increases the low frequency-dependent modulation of the H-reflex, (3) prevents potassium-chloride cotransporter isoform 2 (KCC2) membrane downregulation in lumbar motoneurons, and (4) generally augments motor output, i.e., EMG amplitude in response to single pulses of tSCS, particularly in extensor muscles. Together, this work displays that multi-session tSCS can target and diminish spasticity after SCI as an alternative to pharmacological interventions and begins to highlight the underlying neuroplasticity contributing to its success in improving functional recovery.

Multi-session transcutaneous spinal cord stimulation prevents chloridehomeostasis imbalance and the development of spasticity after spinal cordinjury in rat

Spasticity is a complex and multidimensional disorder that impacts nearly 75% of individuals with spinal cord injury (SCI) and currently lacks adequate treatment options. This sensorimotor condition is burdensome as hyperexcitability of reflex pathways result in exacerbated reflex responses, co-contractions of antagonistic muscles, and involuntary movements. Transcutaneous spinal cord stimulation (tSCS) has become a popular tool in the human SCI research field. The likeliness for this intervention to be successful as a noninvasive anti-spastic therapy after SCI is suggested by a mild and transitory improvement in spastic symptoms following a single stimulation session, but it remains to be determined if repeated tSCS over the course of weeks can produce more profound effects. Despite its popularity, the neuroplasticity induced by tSCS also remains widely unexplored, particularly due to the lack of suitable animal models to investigate this intervention. Thus, the basis of this work was to use tSCS over multiple sessions (multi-session tSCS) in a rat model to target spasticity after SCI and identify the long-term physiological improvements and anatomical neuroplasticity occurring in the spinal cord. Here, we show that multi-session tSCS in rats with an incomplete (severe T9 contusion) SCI (1) decreases hyperreflexia, (2) increases the low frequency-dependent modulation of the H-reflex, (3) prevents potassium-chloride cotransporter isoform 2 (KCC2) membrane downregulation in lumbar motoneurons, and (4) generally augments motor output, i.e., EMG amplitude in response to single pulses of tSCS, particularly in extensor muscles. Together, this work displays that multi-session tSCS can target and diminish spasticity after SCI as an alternative to pharmacological interventions and begins to highlight the underlying neuroplasticity contributing to its success in improving functional recovery.

Bumetanide increases postsynaptic inhibition after chronic SCI and decreases presynaptic inhibition with step-training

Current anti-spastic medication significantly compromises motor recovery after spinal cord injury (SCI), indicating a critical need for alternative interventions. Because a shift in chloride homeostasis decreases spinal inhibition and contributes to hyperreflexia after SCI, we investigated the effect of bumetanide, an FDA-approved sodium-potassium-chloride intruder (NKCC1) antagonist, on presynaptic and postsynaptic inhibition. We compared its effect with step-training as it is known to improve spinal inhibition by restoring chloride homeostasis. In SCI rats, a prolonged bumetanide treatment increased postynaptic inhibition but not presynaptic inhibition of the plantar H-reflex evoked by posterior biceps and semitendinosus (PBSt) group I afferents. By using in vivo intracellular recordings of motoneurons, we further show that a prolonged bumetanide increased postsynaptic inhibition by hyperpolarizing the reversal potential for inhibitory postsynaptic potentials (IPSPs) after SCI. However, in step-trained SCI rats an acute delivery of bumetanide decreased presynaptic inhibition of the H-reflex, but not postsynaptic inhibition. These results suggest that bumetanide might be a viable option to improve postsynaptic inhibition after SCI, but it also decreases the recovery of presynaptic inhibition with step-training. We discuss whether the effects of bumetanide are mediated by NKCC1 or by off-target effects. KEY POINTS: After spinal cord injury (SCI), chloride homeostasis is dysregulated over time in parallel with the decrease in presynaptic inhibition of Ia afferents and postsynaptic inhibition of motoneurons, and the development of spasticity. While step-training counteracts these effects, it cannot always be implemented in the clinic because of comorbidities. An alternative intervention is to use pharmacological strategies to decrease spasticity without hindering the recovery of motor function with step-training. Here we found that, after SCI, a prolonged bumetanide (an FDA-approved antagonist of the sodium-potassium-chloride intruder, NKCC1) treatment increases postsynaptic inhibition of the H-reflex, and it hyperpolarizes the reversal potential for inhibitory postsynaptic potentials in motoneurons. However, in step-trained SCI, an acute delivery of bumetanide decreases presynaptic inhibition of the H-reflex, but not postsynaptic inhibition. Our results suggest that bumetanide has the potential to decrease spastic symptoms related to a decrease in postsynaptic but not presynaptic inhibition after SCI.

Intrathecal and Oral Baclofen Use in Adults With Spinal Cord Injury: A Systematic Review of Efficacy in Spasticity Reduction, Functional Changes, Dosing, and Adverse Events

OBJECTIVE

To examine the efficacy, dosing, and safety profiles of intrathecal and oral baclofen in treating spasticity after spinal cord injury (SCI).

DATA SOURCES

PubMed and Cochrane Databases were searched from 1970-2018 with keywords baclofen, spinal cord injury, and efficacy.

STUDY SELECTION

The database search yielded 588 sources and 10 additional relevant publications. After removal of duplicates, 398 publications were screened.

DATA EXTRACTION

Data were extracted using the following population, intervention, comparator, outcomes, and study designs criteria: studies including adult patients with SCI with spasticity; the intervention could be oral or intrathecal administration of baclofen; selection was inclusive for control groups, surgical management, rehabilitation, and alternative pharmaceutical agents; outcomes were efficacy, dosing, and adverse events. Randomized controlled trials, observational studies, and case reports were included. Meta-analyses and systematic reviews were excluded.

DATA SYNTHESIS

A total of 98 studies were included with 1943 patients. Only 4 randomized, double-blinded, and placebo-controlled trials were reported. Thirty-nine studies examined changes in the Modified Ashworth Scale (MAS; 34 studies) and Penn Spasm scores (Penn Spasm Frequency; 19 studies), with average reductions of 1.7±1.3 and 1.6±1.4 in individuals with SCI, respectively. Of these data, a total of 6 of the 34 studies (MAS) and 2 of the 19 studies (Penn Spasm Frequency) analyzed oral baclofen. Forty-three studies addressed adverse events with muscle weakness and fatigue frequently reported.

CONCLUSIONS

Baclofen is the most commonly-prescribed antispasmodic after SCI. Surprisingly, there remains a significant lack of large, placebo-controlled, double-blinded clinical trials, with most efficacy data arising from small studies examining treatment across different etiologies. In the studies reviewed, baclofen effectively improved spasticity outcome measures, with increased efficacy through intrathecal administration. Few studies assessed how reduced neural excitability affected residual motor function and activities of daily living. A host of adverse events were reported that may negatively affect quality of life. Comparative randomized controlled trials of baclofen and alternative treatments are warranted because these have demonstrated promise in relieving spasticity with reduced adverse events and without negatively affecting residual motor function.

Enhancing KCC2 activity decreases hyperreflexia and spasticity after chronic spinal cord injury

After spinal cord injury (SCI), the majority of individuals develop spasticity, a debilitating condition involving involuntary movements, co-contraction of antagonistic muscles, and hyperreflexia. By acting on GABAergic and Ca2+-dependent signaling, current anti-spastic medications lead to serious side effects, including a drastic decrease in motoneuronal excitability which impairs motor function and rehabilitation efforts. Exercise, in contrast, decreases spastic symptoms without decreasing motoneuron excitability. These functional improvements coincide with an increase in expression of the chloride co-transporter KCC2 in lumbar motoneurons. Thus, we hypothesized that spastic symptoms can be alleviated directly through restoration of chloride homeostasis and endogenous inhibition by increasing KCC2 activity. Here, we used the recently developed KCC2 enhancer, CLP257, to evaluate the effects of acutely increasing KCC2 extrusion capability on spastic symptoms after chronic SCI. Sprague Dawley rats received a spinal cord transection at T12 and were either bike-trained or remained sedentary for 5 weeks. Increasing KCC2 activity in the lumbar enlargement improved the rate-dependent depression of the H-reflex and reduced both phasic and tonic EMG responses to muscle stretch in sedentary animals after chronic SCI. Furthermore, the improvements due to this pharmacological treatment mirror those of exercise. Together, our results suggest that pharmacologically increasing KCC2 activity is a promising approach to decrease spastic symptoms in individuals with SCI. By acting to directly restore endogenous inhibition, this strategy has potential to avoid severe side effects and improve the quality of life of affected individuals.

Zinc promotes autophagy and inhibits apoptosis through AMPK/mTOR signaling pathway after spinal cord injury

Autophagy is a intracellular biological process that controls the homeostasis of nutrition deprivation and starvation and has been associated with the development of traumatic diseases. Zinc, an important chemical element involved in life activities, has improved nerve recovery effects through intraperitoneal injection. The purpose of this study was to probe the possible modulation of autophagy and apoptosis from the injured spinal cord and neurons by zinc administration. It was shown that zinc significantly induced the level of Beclin1 and LC3B by activating adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway. In addition, zinc suppressed apoptosis in the injured spinal cord. Taken together, these findings suggested that zinc through promoting neurons autophagy and inhibiting apoptosis.

Rehabilitation Decreases Spasticity by Restoring Chloride Homeostasis through the Brain-Derived Neurotrophic Factor-KCC2 Pathway after Spinal Cord Injury

Activity-based therapy is routinely integrated in rehabilitation programs to facilitate functional recovery after spinal cord injury (SCI). Among its beneficial effects is a reduction of hyperreflexia and spasticity, which affects ∼75% of the SCI population. Unlike current anti-spastic pharmacological treatments, rehabilitation attenuates spastic symptoms without causing an active depression in spinal excitability, thus avoiding further interference with motor recovery. Understanding how activity-based therapies contribute to decrease spasticity is critical to identifying new pharmacological targets and to optimize rehabilitation programs. It was recently demonstrated that a decrease in the expression of KCC2, a neuronal Cl- extruder, contributes to the development spasticity in SCI rats. Although exercise can decrease spinal hyperexcitability and increase KCC2 expression on lumbar motoneurons after SCI, a causal effect remains to be established. Activity-dependent processes include an increase in brain-derived neurotrophic factor (BDNF) expression. Interestingly, BDNF is a regulator of KCC2 but also a potent modulator of spinal excitability. Therefore, we hypothesized that after SCI, the activity-dependent increase in KCC2 expression: 1) functionally contributes to reduce hyperreflexia, and 2) is regulated by BDNF. SCI rats chronically received VU0240551 (KCC2 blocker) or TrkB-IgG (BDNF scavenger) during the daily rehabilitation sessions and the frequency-dependent depression of the H-reflex, a monitor of hyperreflexia, was recorded 4 weeks post-injury. Our results suggest that the activity-dependent increase in KCC2 functionally contributes to H-reflex recovery and critically depends on BDNF activity. This study provides a new perspective in understanding how exercise impacts hyperreflexia by identifying the biological basis of the recovery of function.

Insulin-like growth factor-1 enhances neuroprotective effects of neural stem cell exosomes after spinal cord injury via an miR-219a-2-3p/YY1 mechanism

Spinal cord injury (SCI) remains the most common cause of paralysis, and there are no effective therapies for SCI patients. Neural stem cell (NSC)-derived exosomes can attenuate apoptosis and neuroinflammation after traumatic spinal cord injury, but the mechanisms underlying these effects remain unclear. Here, we examined the efficacy of miRNAs isolated from exosomes as treatments for SCI and characterized their mechanisms of action. Furthermore, we evaluated the effects of exosomes formed in the presence of insulin growth factor-1 (IFG-1, IGF-Exo), which promotes neural proliferation and regeneration, as well as normal exosomes (Nor-Exo) and compared control and H₂O₂-treated groups both in vitro and in vivo. Using microRNA sequencing and qRT-PCR, we identified miR-219a-2-3p, levels of which were higher in the IGF-Exo than Nor-Exo group and played crucial anti-inflammatory and anti-apoptosis roles. Additional experiments revealed that IGF-Exo inhibits YY1 expression through up-regulation of miR-219a-2-3p. This in turn inhibits the NF-κB pathway, partly inhibiting neuroinflammation and promoting the neuroprotective effects after SCI.

SCIPA Full-On: A Randomized Controlled Trial Comparing Intensive Whole-Body Exercise and Upper Body Exercise After Spinal Cord Injury

Background. While upper body training has been effective for improving aerobic fitness and muscle strength after spinal cord injury (SCI), activity-based therapies intended to activate the paralyzed extremities have been reported to promote neurological improvement. Objective. To compare the effectiveness of intensive whole-body exercise compared with upper body exercise for people with chronic SCI. Methods. A parallel-group randomized controlled trial was conducted. Participants with a range of SCI levels and severity were randomized to either full-body exercise (FBE) or upper body exercise (UBE) groups (3 sessions per week over 12 weeks). FBE participants underwent locomotor training, functional electrical stimulation-assisted leg cycling, and trunk and lower extremity exercises, while UBE participants undertook upper body strength and aerobic fitness training only. The primary outcome measure was the American Spinal Injury Association (ASIA) motor score for upper and lower extremities. Adverse events were systematically recorded. Results. A total of 116 participants were enrolled and included in the primary analysis. The adjusted mean between-group difference was −0.04 (95% CI −1.12 to 1.04) for upper extremity motor scores, and 0.90 (95% CI −0.48 to 2.27) for lower extremity motor scores. There were 15 serious adverse events in UBE and 16 in FBE, but only one of these was definitely related to the experimental intervention (bilateral femoral condyle and tibial plateau subchondral fractures). No significant between-group difference was found for adverse events, or functional or behavioral variables. Conclusions. Full-body training did not lead to improved ASIA motor scores compared with upper body training in people with chronic SCI.

Antispasmodic medications may be associated with reduced recovery during inpatient rehabilitation after traumatic spinal cord injury

OBJECTIVE

To determine whether antispasmodic medications are associated with neurological and functional outcomes during the first year after traumatic spinal cord injury (SCI).

DESIGN/METHODS

Retrospective analysis of prospectively collected data from six inpatient SCI rehabilitation centers. Baseline-adjusted outcomes at discharge and one-year follow-up were compared using analysis of covariance between patients who received antispasmodic medication on at least 5 days during inpatient rehabilitation and patients who did not.

OUTCOME MEASURES

Rasch-transformed motor subscore of the Functional Independence Measure (FIM); International Standards for Neurological Classification of Spinal Cord Injury motor scores, grade, and level.

RESULTS

Of 1,259 patients, 59.8%, 35.4%, and 4.8% were injured at the cervical, thoracic, and lumbosacral levels, respectively. 65.6% had motor complete injury. Rasch-transformed motor FIM score at admission averaged 23.3 (95% confidence interval (CI) 22.4-24.2). Total motor score averaged 39.2 (95% CI 37.8-40.6). 685 patients (54.4%) received one or more antispasmodic medications on at least 5 days. After controlling for demographic and injury variables at admission, Rasch-transformed motor FIM scores at discharge were significantly lower (P = 0.018) in patients receiving antispasmodic medications than in those who did not. This trend persisted in secondary analyses for cervical, thoracic, and lumbosacral subgroups. Multivariate regression showed that receiving antispasmodic medication significantly contributed to discharge motor FIM outcome. At one-year follow-up, no outcomes significantly differed between patients ON or OFF antispasmodics.

CONCLUSIONS

Antispasmodic medications may be associated with decreased functional recovery at discharge from inpatient traumatic SCI rehabilitation. Randomized prospective studies are needed to directly evaluate the effects of antispasmodic medication on recovery.

The role of exosomes derived from cerebrospinal fluid of spinal cord injury in neuron proliferation in vitro

Exosomes is a key component of cell paracrine secretion and can exert important effects in various disease models. However, the role of exosomes in neuron repair of spinal cord injury (SCI) has rarely been reported. In this study, Exosomes were isolated from cerebrospinal fluid of SCI and normal, and incubated neuron in vitro respectively to research its biological function in cell proliferation. The results demonstrated these exosomes all expressed CD9, CD63, CD81, Alix and Tsg101; however, only exosomes derived from cerebrospinal fluid of SCI could promote proliferation of neuron via ERK signaling pathway, and decrease cell apoptosis. Exosomes contain cytosolic content, including proteins, mRNAs and non-cording RNAs, and play a role in important biological function. Our research showed exosomes derived from cerebrospinal fluid of SCI, they can influence neuron cell proliferation in vitro, we did not observe these characters in exosome derived from normal cerebrospinal fluid.

Combination of melatonin and Wnt-4 promotes neural cell differentiation in bovine amniotic epithelial cells and recovery from spinal cord injury

Although melatonin has been shown to exhibit a wide variety of biological functions, its effects on promoting differentiation of neural cells remain unknown. Wnt signaling mediates major developmental processes during embryogenesis and regulates maintenance, self-renewal, and differentiation of adult mammalian stem cells. However, the role of the noncanonical Wnt pathway during neurogenesis remains poorly understood. In this study, the amniotic epithelial cells ( AECs) were isolated from bovine amnion and incubated with various melatonin concentrations (0.01, 0.1, 1, 10, or 100 μm) and 5 × 10(-5) m all-trans retinoic acid (RA) for screening optimum culture medium of neural differentiation, compared with each groups, 1 μm melatonin and 5 × 10(-5) m RA were selected to induce neural differentiation of AECs, and then siMT1, siMT2, oWnt-4, and siWnt-4 were expressed in AECs to research role of these genes in neural differentiation. Efficiency of neural differentiation was evaluated after expressed above genes using flow cytometry. Cell function of neural cells was demonstrated in vivo using spinal cord injury model after cell transplantation, and damage repair of spinal cord was assessed using cell tracking and Basso, Beattie, Bresnahan Locomotor Rating Scale scores. Results demonstrated that melatonin stimulated melatonin receptor 1, which subsequently increased bovine amniotic epithelial cell vitality and promoted differentiation into neural cells. This took place through cooperation with Wnt-4. Additionally, following cotreatment with melatonin and Wnt-4, neurogenesis gene expression was significantly altered. Furthermore, single inhibition of melatonin receptor 1 or Wnt-4 expression decreased expression of neurogenesis-related genes, and bovine amniotic epithelial cell-derived neural cells were successfully colonized into injured spinal cord, which suggested participation in tissue repair.

Exercise modulates chloride homeostasis after spinal cord injury

Activity-based therapies are routinely integrated in spinal cord injury (SCI) rehabilitation programs because they result in a reduction of hyperreflexia and spasticity. However, the mechanisms by which exercise regulates activity in spinal pathways to reduce spasticity and improve functional recovery are poorly understood. Persisting alterations in the action of GABA on postsynaptic targets is a signature of CNS injuries, including SCI. The action of GABA depends on the intracellular chloride concentration, which is determined largely by the expression of two cation-chloride cotransporters (CCCs), KCC2 and NKCC1, which serve as chloride exporters and importers, respectively. We hypothesized that the reduction in hyperreflexia with exercise after SCI relies on a return to chloride homeostasis. Sprague Dawley rats received a spinal cord transection at T12 and were assigned to SCI-7d, SCI-14d, SCI-14d+exercise, SCI-28d, SCI-28d+exercise, or SCI-56d groups. During a terminal experiment, H-reflexes were recorded from interosseus muscles after stimulation of the tibial nerve and the low-frequency-dependent depression (FDD) was assessed. We provide evidence that exercise returns spinal excitability and levels of KCC2 and NKCC1 toward normal levels in the lumbar spinal cord. Acutely altering chloride extrusion using the KCC2 blocker DIOA masked the effect of exercise on FDD, whereas blocking NKCC1 with bumetanide returned FDD toward intact levels after SCI. Our results indicate that exercise contributes to reflex recovery and restoration of endogenous inhibition through a return to chloride homeostasis after SCI. This lends support for CCCs as part of a pathway that could be manipulated to improve functional recovery when combined with rehabilitation programs.