Constraint-Induced Movement Therapy Enhanced Neurogenesis and Behavioral Recovery after Stroke in Adult Rats

Early, Intense Rehabilitation Fails to Improve Outcome After Intra-Striatal Hemorrhage in Rats

BACKGROUND

The formation and degradation of an intracerebral hemorrhage causes protracted cell death, and an extended window for intervention. Experimental studies find that rehabilitation mitigates late cell death, with accelerated hematoma clearance as a potential mechanism.

OBJECTIVE

We assessed whether early, intense, enriched rehabilitation (ER, environmental enrichment and massed skills training) enhances functional benefit, reduces brain injury, and augments hematoma clearance.

METHODS

In experiment 1, rats (n = 56) were randomized to intervention in the light (-L) or dark phase (-D) of their housing cycle, then to 10 days of ER or control (CON) treatment after collagenase-induced striatal intracerebral hemorrhage (ICH). ER rats were treated from 5 to 14 days after ICH. Behavior and residual hematoma volume was assessed on day 14. In experiment 2, rats (n = 72) were randomized to ER-D10, ER-D20, or CON-D. ER rats completed 10 or 20 days of training in the dark. Rats were euthanized on day 60 for histology. In both experiments, behavioral assessment was completed pre-ICH, pre-ER (day 4 post-ICH), and post-ER (experiment 1: days 13-14; experiment 2: days 16-17 and 30-31).

RESULTS

Reaching intensity was high but similar between ER-D10 and ER-L10. Unlike previous work, rehabilitation did not alter skilled reaching or hematoma resolution. Varying ER duration also did not affect reaching success or lesion volume.

CONCLUSIONS

In contrast to others, and under these conditions, our findings show that striatal ICH was generally unresponsive to rehabilitation. This highlights the difficulty of replicating and extending published work, perhaps owing to small inter-study differences.

Targeting the Erk1/2 and autophagy signaling easily improved the neurobalst differentiation and cognitive function after young transient forebrain ischemia compared to old gerbils

The hippocampal neurogenesis occurs constitutively throughout adulthood in mammalian species, but declines with age. In this study, we overtly found that the neuroblast proliferation and differentiation in the subgranular zone and the maturation into fully functional and integrated neurons in the granule-cell layer in young gerbils following cerebral ischemia/reperfusion was much more than those in old gerbils. The neurological function and cognitive and memory-function rehabilitation in the young gerbils improved faster than those in the old one. These results demonstrated that, during long term after cerebral ischemia/reperfusion, the ability of neurogenesis and recovery of nerve function in young animals were significantly higher than that in the old animals. We found that, after 14- and 28-day cerebral ischemia/reperfusion, the phosphorylation of MEK1/2, ERK1/2, p90RSK, and MSK1/2 protein levels in the hippocampus of young gerbils was significantly much higher than that of old gerbils. The levels of autophagy-related proteins, including Beclin-1, Atg3, Atg5, and LC3 in the hippocampus were effectively maintained and elevated at 28 days after cerebral ischemia/reperfusion in the young gerbils compared with those in the old gerbils. These results indicated that an increase or maintenance of the phosphorylation of ERK1/2 signal pathway and autophagy-related proteins was closely associated with the neuroblast proliferation and differentiation and the process of maturation into neurons. Further, we proved that neuroblast proliferation and differentiation in the dentate gyrus and cognitive function were significantly reversed in young cerebral ischemic gerbils by administering the ERK inhibitor (U0126) and autophagy inhibitor (3MA). In brief, following experimental young ischemic stroke, the long-term promotion of the neurogenesis in the young gerbil’s hippocampal dentate gyrus by upregulating the phosphorylation of ERK signaling pathway and maintaining autophagy-related protein levels, it overtly improved the neurological function and cognitive and memory function.

Contralesional plasticity following constraint-induced movement therapy benefits outcome: contributions of the intact hemisphere to functional recovery

Stroke is a leading cause of death and disability worldwide. A common, chronic deficit after stroke is upper limb impairment, which can be exacerbated by compensatory use of the nonparetic limb. Resulting in learned nonuse of the paretic limb, compensatory reliance on the nonparetic limb can be discouraged with constraint-induced movement therapy (CIMT). CIMT is a rehabilitative strategy that may promote functional recovery of the paretic limb in both acute and chronic stroke patients through intensive practice of the paretic limb combined with binding, or otherwise preventing activation of, the nonparetic limb during daily living exercises. The neural mechanisms that support CIMT have been described in the lesioned hemisphere, but there is a less thorough understanding of the contralesional changes that support improved functional outcome following CIMT. Using both human and non-human animal studies, the current review explores the role of the contralesional hemisphere in functional recovery of stroke as it relates to CIMT. Current findings point to a need for a better understanding of the functional significance of contralesional changes, which may be determined by lesion size, location, and severity as well stroke chronicity.

Constraint-induced movement therapy enhances AMPA receptor-dependent synaptic plasticity in the ipsilateral hemisphere following ischemic stroke

Constraint-induced movement therapy (CIMT) can promote the recovery of motor function in injured upper limbs following stroke, which may be associated with upregulation of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) at synapses in the ipsilateral sensorimotor cortex in our previous study. However, AMPAR distribution is tightly regulated, and only AMPARs on the postsynaptic membrane can mediate synaptic transmission. We speculated that synaptic remodeling induced by movement-associated synaptic activity can promote functional recovery from stroke. To test this hypothesis, we compared AMPAR expression on the postsynaptic membrane surface in a rat model of ischemic stroke induced by middle cerebral artery occlusion (MCAO) with versus without CIMT, which consisted of daily running wheel training for 2 weeks starting on day 7 after MCAO. The results showed that CIMT increased the number of glutamate receptor (GluR)2-containing functional synapses in the ipsilateral sensorimotor cortex, and reduced non-GluR2 AMPARs in the ipsilateral sensorimotor cortex and hippocampal CA3 region. In addition, CIMT enhanced AMPAR expression on the surface of post-synaptic membrane in the ipsilateral sensorimotor cortex and hippocampus. Thus, CIMT promotes the recovery of motor function of injured upper limbs following stroke by enhancing AMPAR-mediated synaptic transmission in the ischemic hemisphere. These findings provide supporting evidence for the clinical value of CIMT for restoring limb movement in stroke patients. All experimental procedures and protocols were approved by the Department of Laboratory Animal Science of Fudan University, China (approval No. 201802173S) on March 3, 2018.

Constraint-induced movement therapy promotes motor recovery after neonatal stroke in the absence of neural precursor activation

Neonatal stroke is a leading cause of long-term disability and currently available rehabilitation treatments are insufficient to promote recovery. Activating neural precursor cells (NPCs) in adult rodents, in combination with rehabilitation, can accelerate functional recovery following stroke. Here, we describe a novel method of constraint-induced movement therapy (CIMT) in a rodent model of neonatal stroke that leads to improved functional outcomes, and we asked whether the recovery was correlated with expansion of NPCs. A hypoxia/ischemia (H/I) injury was induced on postnatal day 8 (PND8) via unilateral carotid artery ligation followed by systemic hypoxia. One week and two weeks post-H/I, CIMT was administered in the form of 3 botulinum toxin (Botox) injections, which induced temporary paralysis in the unaffected limb. Functional recovery was assessed using the foot fault task. NPC proliferation was assessed using the neurosphere assay and EdU immunohistochemistry. We found that neonatal H/I injury alone expands the NPC pool by >2.5-fold relative to controls. We determined that using Botox injections as a method to provide CIMT results in significant functional motor recovery after H/I. However, CIMT does not lead to enhanced NPC activation or migration into the injured parenchyma in vivo. At the time of functional recovery, increased numbers of proliferating inflammatory cells were found within the injured motor cortex. Together, these findings suggest that NPC activation following CIMT does not account for the observed functional improvement and suggests that CIMT-mediated modification of the CNS inflammatory response may play a role in the motor recovery.

Neurobiology of Recovery of Motor Function after Stroke: The Central Nervous System Biomarker Effects of Constraint-Induced Movement Therapy

Recovery of motor function after stroke involves many biomarkers. This review attempts to identify the biomarker effects responsible for recovery of motor function following the use of Constraint-Induced Movement Therapy (CIMT) and discuss their implications for research and practice. From the studies reviewed, the biomarker effects identified include improved perfusion of motor areas and brain glucose metabolism; increased expression of proteins, namely, Brain-Derived Neurotrophic Factor (BDNF), Vascular Endothelial Growth Factor (VEGF), and Growth-Associated Protein 43 (GAP-43); and decreased level of Gamma-Aminobutyric Acid (GABA). Others include increased cortical activation, increased motor map size, and decreased interhemispheric inhibition of the ipsilesional hemisphere by the contralesional hemisphere. Interestingly, the biomarker effects correlated well with improved motor function. However, some of the biomarker effects have not yet been investigated in humans, and they require that CIMT starts early on poststroke. In addition, one study seems to suggest the combined use of CIMT with other rehabilitation techniques such as Transcortical Direct Stimulation (tDCs) in patients with chronic stroke to achieve the biomarker effects. Unfortunately, there are few studies in humans that implemented CIMT during early poststroke. Thus, it is important that more studies in humans are carried out to determine the biomarker effects of CIMT especially early on poststroke, when there is a greater opportunity for recovery. Furthermore, it should be noted that these effects are mainly in ischaemic stroke.

Constraint-induced movement therapy improves functional recovery after ischemic stroke and its impacts on synaptic plasticity in sensorimotor cortex and hippocampus

Constraint-induced movement therapy (CIMT) has proven to be an effective way to restore functional deficits following stroke in human and animal studies, but its underlying neural plasticity mechanism remains unknown. Accumulating evidence indicates that rehabilitation after stroke is closely associated with synaptic plasticity. We therefore investigated the impact of CIMT on synaptic plasticity in ipsilateral and contralateral brain of rats following stroke. Rats were subjected to 90 minutes of transient middle cerebral artery occlusion (MCAO). CIMT was performed from 7 days after stroke and lasted for two weeks. Modified Neurology Severity Score (mNSS) and the ladder rung walking task tests were conducted at 7,14 and 21 days after stroke. Golgi-Cox staining was used to observe the plasticity changes of dendrites and dendritic spines. The expression of glutamate receptors (GluR1, GluR2 and NR1) were examined by western blot. Our data suggest that the dendrites and dendritic spines are damaged to varying degrees in bilateral sensorimotor cortex and hippocampus after acute stroke. CIMT treatment enhances the plasticity of dendrites and dendritic spines in the ipsilateral and contralateral sensorimotor cortex, increases the expression of synaptic GluR2 in ipsilateral sensorimotor cortex, which may be mechanisms for CIMT to improve functional recovery after ischemic stroke.

Effects of CXCR7-neutralizing antibody on neurogenesis in the hippocampal dentate gyrus and cognitive function in the chronic phase of cerebral ischemia

Stromal cell-derived factor-1 and its receptor CXCR4 are essential regulators of the neurogenesis that occurs in the adult hippocampal dentate gyrus. However, the effects of CXCR7, a new atypical receptor of stromal cell-derived factor-1, on hippocampal neurogenesis after a stroke remain largely unknown. Our study is the first to investigate the effect of a CXCR7-neutralizing antibody on neurogenesis in the dentate gyrus and the associated recovery of cognitive function of rats in the chronic stage of cerebral ischemia. The rats were randomly divided into sham, sham + anti-CXCR7, ischemia and ischemia + anti-CXCR7 groups. Endothelin-1 was injected in the ipsilateral motor cortex and striatum to induce focal cerebral ischemia. Sham group rats were injected with saline instead of endothelin-1 via intracranial injection. Both sham and ischemic rats were treated with intraventricular infusions of CXCR7-neutralizing antibodies for 6 days 1 week after surgery. Immunofluorescence staining with doublecortin, a marker for neuronal precursors, was performed to assess the neurogenesis in the dentate gyrus. We found that anti-CXCR7 antibody infusion enhanced the proliferation and dendritic development of doublecortin-labeled cells in the dentate gyrus in both ischemic and sham-operated rats. Spatial learning and memory functions were assessed by Morris water maze tests 30–32 days after ischemia. CXCR7-neutralizing antibody treatment significantly reduced the escape latency of the spatial navigation trial and increased the time spent in the target quadrant of spatial probe trial in animals that received ischemic insult, but not in sham operated rats. These results suggest that CXCR7-neutralizing antibody enhances the neurogenesis in the dentate gyrus and improves the cognitive function after cerebral ischemia in rats. All animal experimental protocols and procedures were approved by the Institutional Animal Care and Use Committee of China Medical University (CMU16089R) on December 8, 2016.

Region-specific and activity-dependent regulation of SVZ neurogenesis and recovery after stroke

Recovery after stroke involves remodeling in brain tissue adjacent to the stroke site. In this remodeling, neurogenesis after stroke involves the formation of new neurons. The role of neurogenesis in stroke recovery and the role of brain and behavioral activity in this process remain undefined. Using orthogonal transgenic mouse tracing and rabies virus approaches, we demonstrate that brain regions unexpectedly compete for new neurons after stroke and that the behavioral or cellular activity establishes this competition. These new neurons synaptically integrate into cortex, and this integration is necessary for poststroke recovery.

Stroke is the leading cause of adult disability. Neurogenesis after stroke is associated with repair; however, the mechanisms regulating poststroke neurogenesis and its functional effect remain unclear. Here, we investigate multiple mechanistic routes of induced neurogenesis in the poststroke brain, using both a forelimb overuse manipulation that models a clinical neurorehabilitation paradigm, as well as local manipulation of cellular activity in the peri-infarct cortex. Increased activity in the forelimb peri-infarct cortex via either modulation drives increased subventricular zone (SVZ) progenitor proliferation, migration, and neuronal maturation in peri-infarct cortex. This effect is sensitive to competition from neighboring brain regions. By using orthogonal tract tracing and rabies virus approaches in transgenic SVZ-lineage-tracing mice, SVZ-derived neurons synaptically integrate into the peri-infarct cortex; these effects are enhanced with forelimb overuse. Synaptic transmission from these newborn SVZ-derived neurons is critical for spontaneous recovery after stroke, as tetanus neurotoxin silencing specifically of the SVZ-derived neurons disrupts the formation of these synaptic connections and hinders functional recovery after stroke. SVZ-derived neurogenesis after stroke is activity-dependent, region-specific, and sensitive to modulation, and the synaptic connections formed by these newborn cells are functionally critical for poststroke recovery.

Constraint Induced Movement Therapy as a Rehabilitative Strategy for Ischemic Stroke-Linking Neural Plasticity with Restoration of Skilled Movements

BACKGROUND

Stroke leads to devastating impact on health as well as quality of life making it one of the leading causes of disability. Restoring the functions of upper extremities after ischemic (ISC) stroke is one of the challenges for rehabilitation. Lack of trained professionals and accessibility to rehabilitation centers are limited in many counties. Constraint induced movement therapy (CIMT) has been practiced in regaining the functional activity following stroke. CIMT can be practiced with minimum clinical set up which makes it cost effective. However, the neural plasticity mechanism underlying the recovery with CIMT is not well understood.

METHODS

In the current study, we sought to investigate the extent to which CIMT helps in ameliorating neurological deficits in rat model of ISC stroke, induced by Endothelin-1 (ET-1). As well as to understand the cortical plasticity with Golgi-Cox staining and interhemispheric interaction with biotinylated dextran amine (BDA) following CIMT. Neurological deficits were identified within 24 hours of ET-1 infusion.

RESULTS

CIMT restored the impaired skilled movements after ISC stroke and improved the quality of fine movements. Golgi-Cox staining showed significant decrease in dendritic arborization in the injured motor cortex following ISC stroke. CIMT was efficient in reversing this effect as indicated by increased dendritic arborization especially in layer III pyramidal neurons. Also, the stroke induced asymmetry in dendritic length across both hemispheres was found to be reduced with CIMT. BDA tracing showed a re-establishment of the axonal connections between the hemispheres after CIMT.

CONCLUSIONS

Implications of CIMT can be one of the promising and low cost rehabilitative technique for the individuals with upper limb movement deficits.

Constrained-induced movement therapy promotes motor function recovery by enhancing the remodeling of ipsilesional corticospinal tract in rats after stroke

Constraint-induced movement therapy (CIMT), which forces the use of the impaired limb by restraining the unaffected limb, has been used extensively for the recovery of limb motor function after stroke. However, the underlying mechanism of CIMT remains unclear. Diffusion tensor imaging (DTI) is a well-known neuroimaging technique that reflects the microstructure of white matter tracts and potential changes associated with different treatments. The aim of this study is to use DTI imaging to determine how corticospinal tract (CST) fibers remodel in ischemic rats with CIMT. In the present study, rats were randomly divided into three groups: a middle cerebral artery occlusion group (MCAO), a therapeutic group (MCAO + CIMT), and a sham-operated group (sham). A plaster cast was used to restrict the unaffected limb of the rats in the MCAO + CIMT group for 14 days. The Catwalk system was used to assess the limb motor function of rats. Fractional anisotropy (FA) and the average diffusion coefficient (ADC) of the CST were quantified through DTI. The expression of the c-Jun-N-terminal kinase signaling pathway (JNK) was examined after 14 days of CIMT. We found that CIMT could accelerate and enhance motor function recovery, and the MCAO + CIMT group showed significantly increased FA values in the ipsilesional posterior limb of internal capsule (PLIC) compared with the MCAO group. In addition, we found no significant difference in the ratio of phosphorylated-JNK/total-JNK among the three groups, whereas the expression of P-JNK decreased significantly in the chronic phase of stroke. In conclusion, CIMT-induced functional recovery following ischemic stroke through facilitation of the remodeling of ipsilesional CST, and restoration after ischemic stroke may be associated with the declining value of the ratio of P-JNK/JNK.

Training of the impaired forelimb after traumatic brain injury enhances hippocampal neurogenesis in the Emx1 null mice lacking a corpus callosum

Unilateral brain injury is known to disrupt the balance between the two cortices, as evidenced by an abnormally high interhemispheric inhibitory drive from motor cortex M1_intact to M1_lesioned transmitted transcallosally. Our previous work has shown that the deletion of homeobox gene Emx1 not only led to the agenesis of the corpus callosum (cc), but also to reduced hippocampal neurogenesis. The current study sought to determine whether lacking the cc affected the recovery of forelimb function and hippocampal plasticity following training of the affected limb in mice with unilateral traumatic brain injuries (TBI). One week after TBI, produced by a controlled cortical impact to impair the preferred limb, Emx1 wild type (WT) and knock out (KO) mice were subjected to the single-pellet reaching task with the affected limb for 4 weeks. Both TBI and Emx1 deletion had overall adverse effects on the successful rate of reaching. However, TBI significantly affected reaching performance only in the WT mice and not in the KO mice. Both TBI and Emx1 gene deletion also negatively affected hippocampal neurogenesis, demonstrated by a reduction in doublecortin (DCX)-expressing immature neurons, while limb training enhanced DCX expression. However, limb training increased DCX cells in KO mice only in the TBI-treated group, whereas it induced neurogenesis in both WT mice groups regardless of the treatment. Our finding also suggests that limb training enhances neuroplasticity after brain injury at functionally remote regions including the hippocampus, which may have implications for promoting overall recovery of function after TBI.

Constraint-induced movement therapy in treatment of acute and sub-acute stroke: a meta-analysis of 16 randomized controlled trials

OBJECTIVE:

The aim of this meta-analysis was to evaluate the clinical efficacy of constraint-induced movement therapy in acute and sub-acute stroke.

DATA SOURCES:

The key words were stroke, cerebrovascular accident, constraint-induced therapy, forced use, and randomized controlled trial. The databases, including China National Knowledge Infrastructure, WanFang, Weipu Information Resources System, Chinese Biomedical Literature Database, PubMed, Medline, Embase, the Cochrane Central Register of Controlled Trials, and the Cochrane Database of Systematic Reviews, were searched for studies on randomized controlled trials for treating acute or sub-acute stroke published before March 2016.

DATA SELECTION:

We retrieved relevant randomized controlled trials that compared constraint-induced movement therapy in treatment of acute or sub-acute stroke with traditional rehabilitation therapy (traditional occupational therapy). Patients were older than 18 years, had disease courses less than 6 months, and were evaluated with at least one upper extremity function scale. Study quality was evaluated, and data that met the criteria were extracted. Stata 11.0 software was used for the meta-analysis.

OUTCOME MEASURES:

Fugl-Meyer motor assessment of the arm, the action research-arm test, a motor activity log for amount of use and quality of movement, the Wolf motor function test, and a modified Barthel index.

RESULTS:

A total of 16 prospective randomized controlled trials (379 patients in the constraint-induced movement-therapy group and 359 in the control group) met inclusion criteria. Analysis showed significant mean differences in favor of constraint-induced movement therapy for the Fugl–Meyer motor assessment of the arm (weighted mean difference (WMD) = 10.822; 95% confidence intervals (95% CI): 7.419–14.226), the action research-arm test (WMD = 10.718; 95% CI: 5.704–15.733), the motor activity log for amount of use and quality of movement (WMD = 0.812; 95% CI: 0.331–1.293) and the modified Barthel index (WMD = 10.706; 95% CI: 4.417–16.966).

CONCLUSION:

Constraint-induced movement therapy may be more beneficial than traditional rehabilitation therapy for improving upper limb function after acute or sub-acute stroke.

CXCR4 antagonist AMD3100 reverses the neurogenesis and behavioral recovery promoted by forced limb-use in stroke rats

PURPOSE

Forced limb-use can enhance neurogenesis and behavioral recovery as well as increasing the level of stromal cell-derived factor-1 (SDF-1) in stroke rats. We examined whether the SDF-1/CXCR4 pathway is involved in the enhanced neurogenesis and promoted behavioral recovery induced by forced limb-use in the chronic phase of stroke.

METHODS

The CXCR4 antagonist, AMD3100, was used to block the SDF-1/CXCR4 pathway in the ischemic rats. Brain ischemia was induced by endothelin-1. One week after ischemia, the unimpaired forelimb of rats was immobilized for 3 weeks. The proliferation, migration, and survival of DCX-positive cells in the subventricular zone (SVZ), and the dendritic complexity of DCX-positive cells in the dentate gyrus (DG), as well as the inflammatory response in the infarcted striatum were analyzed by immunohistochemistry. Functional recovery was assessed in beam-walking and water maze tests.

RESULTS

Forced limb-use enhanced the proliferation, migration, dendritic complexity and the survival of newborn neurons. Furthermore, forced limb-use suppressed the inflammatory response and improved both motor and cognitive functions after stroke. AMD3100 significantly abrogated the enhanced neurogenesis and behavioral recovery induced by forced limb-use without influencing the inflammatory response.

CONCLUSIONS

SDF-1/CXCR4 pathway seems to be involved in the enhancement of neurogenesis and behavioral recovery induced by post-stroke forced limb-use.

Constraint-induced movement therapy promotes motor function recovery and downregulates phosphorylated extracellular regulated protein kinase expression in ischemic brain tissue of rats

Motor function impairment is a common outcome of stroke. Constraint-induced movement therapy (CIMT) involving intensive use of the impaired limb while restraining the unaffected limb is widely used to overcome the effects of 'learned non-use' and improve limb function after stroke. However, the underlying mechanism of CIMT remains unclear. In the present study, rats were randomly divided into a middle cerebral artery occlusion (model) group, a CIMT + model (CIMT) group, or a sham group. Restriction of the affected limb by plaster cast was performed in the CIMT and sham groups. Compared with the model group, CIMT significantly improved the forelimb functional performance in rats. By western blot assay, the expression of phosphorylated extracellular regulated protein kinase in the bilateral cortex and hippocampi of cerebral ischemic rats in the CIMT group was significantly lower than that in the model group, and was similar to sham group levels. These data suggest that functional recovery after CIMT may be related to decreased expression of phosphorylated extracellular regulated protein kinase in the bilateral cortex and hippocampi.

Promoting recovery from ischemic stroke

Over recent decades, experimental and clinical stroke studies have identified a number of neurorestorative treatments that stimulate neural plasticity and promote functional recovery. In contrast to the acute stroke treatments thrombolysis and endovascular thrombectomy, neurorestorative treatments are still effective when initiated days after stroke onset, which makes them applicable to virtually all stroke patients. In this article, selected physical, pharmacological and cell-based neurorestorative therapies are discussed, with special emphasis on interventions that have already been transferred from the laboratory to the clinical setting. We explain molecular and structural processes that promote neural plasticity, discuss potential limitations of neurorestorative treatments, and offer a speculative viewpoint on how neurorestorative treatments will evolve.

CXCR4 Antagonist AMD3100 Suppresses the Long-Term Abnormal Structural Changes of Newborn Neurons in the Intraventricular Kainic Acid Model of Epilepsy

Abnormal hippocampal neurogenesis is a prominent feature of temporal lobe epilepsy (TLE) models, which is thought to contribute to abnormal brain activity. Stromal cell-derived factor-1 (SDF-1) and its specific receptor CXCR4 play important roles in adult neurogenesis. We investigated whether treatment with the CXCR4 antagonist AMD3100 suppressed aberrant hippocampal neurogenesis, as well as the long-term consequences in the intracerebroventricular kainic acid (ICVKA) model of epilepsy. Adult male rats were randomly assigned as control rats, rats subjected to status epilepticus (SE), and post-SE rats treated with AMD3100. Animals in each group were divided into two subgroups (acute stage and chronic stage). We used immunofluorescence staining of BrdU and DCX to analyze the hippocampal neurogenesis on post-SE days 10 or 74. Nissl staining and Timm staining were used to evaluate hippocampal damage and mossy fiber sprouting, respectively. On post-SE day 72, the frequency and mean duration of spontaneous seizures were measured by electroencephalography (EEG). Cognitive function was evaluated by Morris water maze testing on post-SE day 68. The ICVKA model of TLE resulted in aberrant neurogenesis such as altered proliferation, abnormal dendrite development of newborn neurons, as well as spontaneous seizures and spatial learning impairments. More importantly, AMD3100 treatment reversed the aberrant neurogenesis seen after TLE, which was accompanied by decreased long-term seizure activity, though improvement in spatial learning was not seen. AMD3100 could suppress long-term seizure activity and alter adult neurogenesis in the ICVKA model of TLE, which provided morphological evidences that AMD3100 might be beneficial for treating chronic epilepsy.

The potential for stem cell therapies to have an impact on cerebral palsy: opportunities and limitations

Cerebral palsy (CP) is a chronic childhood disorder described by a group of motor and cognitive impairments and results in a substantial socio-economic burden to the individual, family, and healthcare system. With no effective biological interventions, therapies for CP are currently restricted to supportive and management strategies. Cellular transplantation has been suggested as a putative intervention for neural pathology, as mesenchymal and neural stem cells, as well as olfactory ensheathing glia and Schwann cells, have shown some regenerative and functional efficacy in experimental central nervous system disorders. This review describes the most common cell types investigated and delineates their purported mechanisms in vivo. Furthermore, it provides a cogent summary of both current early-phase clinical trials using neural precursor cells (NPCs) and the state of stem cell therapies for neurodegenerative conditions. Although NPCs are perhaps the most promising candidates for cell replacement therapy in the context of CP, much still remains to be understood regarding safety, efficacy, timing, dose, and route of transplantation, as well as the capacity for combinatorial strategies.

Noninvasive strategies to promote functional recovery after stroke

Stroke is a common and disabling global health-care problem, which is the third most common cause of death and one of the main causes of acquired adult disability in many countries. Rehabilitation interventions are a major component of patient care. In the last few years, brain stimulation, mirror therapy, action observation, or mental practice with motor imagery has emerged as interesting options as add-on interventions to standard physical therapies. The neural bases for poststroke recovery rely on the concept of plasticity, namely, the ability of central nervous system cells to modify their structure and function in response to external stimuli. In this review, we will discuss recent noninvasive strategies employed to enhance functional recovery in stroke patients and we will provide an overview of neural plastic events associated with rehabilitation in preclinical models of stroke.

Constraint-Induced Movement Therapy Overcomes the Intrinsic Axonal Growth–Inhibitory Signals in Stroke Rats

Background and Purpose—

Constraint-induced movement therapy (CIMT) improves functional outcome in patients with stroke possibly through structural plasticity. We hypothesized that CIMT could enhance axonal growth by overcoming the intrinsic growth–inhibitory signals, leading eventually to improved behavioral performance in stroke rats.

Methods—

Focal cerebral ischemia was induced by intracerebral injection of endothelin-1. Adult Wistar rats were divided into a sham-operated group, an ischemic group, and an ischemic group treated with CIMT. CIMT started at postoperative day 7 and continued for 3 weeks. Biotinylated dextran amine was injected into the contralateral sensorimotor cortex at postoperative day 14 to trace crossing axons at the cervical spinal cord. The expressions of Nogo-A, Nogo receptor, RhoA, and Rho-associated kinase in the peri-infarct cortex, and the expressions of biotinylated dextran amine, growth associated protein-43, synaptophysin, vGlut1, and postsynaptic density-95 in the denervated spinal cord were measured by immunohistochemistry and Western blots. Behavioral recovery was analyzed at postoperative days 29 to 32.

Results—

Infarct volumes were not different between groups after stroke. CIMT significantly increased the length and the number of midline crossings of contralateral corticospinal axons to the denervated cervical spinal cord. CIMT significantly decreased the expressions of Nogo-A/Nogo receptor and RhoA/Rho-associated kinase in the peri-infarct cortex, and increased the expressions of growth associated protein-43, synaptophysin, vGlut1, and postsynaptic density-95 in the denervated cervical spinal cord. Behavioral performances assessed by the beam-walking test and the water maze test were improved significantly by CIMT.

Conclusions—

CIMT promoted poststroke synaptic plasticity and axonal growth at least partially by overcoming the intrinsic growth–inhibitory signaling, leading to improved behavioral outcome.

Structural neuroplastic change after constraint-induced movement therapy in children with cerebral palsy

Research from the present laboratory with adult stroke patients showed that structural neuroplastic changes are correlated with clinical improvements due to constraint-induced movement (CI) therapy. This pilot study evaluated whether comparable changes occur in children receiving CI therapy. Ten children (6 boys) with congenital hemiparesis (mean age: 3 years, 3 months) underwent MRI scans 3 weeks before, immediately before, and immediately after receiving 3 weeks of CI therapy. Longitudinal voxel-based morphometry was performed on MRI scans to determine gray matter change. In addition, the Pediatric Motor Activity Log-Revised was administered at these time points to assess arm use in daily life before and after treatment. Children exhibited large improvements after CI therapy in spontaneous use of the more-affected arm (P < .001, d' = 3.24). A significant increase in gray matter volume occurred in the sensorimotor cortex contralateral to the more-affected arm (P = .04); there was a trend for these changes to be correlated with motor improvement (r = 0.63, P = .063). Trends were also observed for increases in gray matter volume in the ipsilateral motor cortex (P = .055) and contralateral hippocampus (P = .1). No significant gray matter change was seen during the 3 weeks before treatment. These findings suggest that CI therapy produces gray matter increases in the developing nervous system and provide additional evidence that CI therapy is associated with structural remodeling of the human brain while producing motor improvement in patients with disabling central nervous system diseases.

Effect of a contralateral lesion on neurological recovery from stroke in rats

PURPOSE

Clinical studies suggest a correlation between changes in activity of the contralesional cerebral cortex and spontaneous recovery from stroke, but whether this is a causal relationship is uncertain.

METHODS

Young adult Sprague-Dawley male rats underwent unilateral or bilateral permanent distal middle cerebral artery occlusion (dMCAO). Infarct volume was determined by 2,3,5-triphenyltetrazolium chloride (TTC) staining 24 hr after dMCAO, and functional outcome was assessed 1-28 days after dMCAO using the ladder rung walking and limb placing tests.

RESULTS

Infarct volume was unchanged, but functional neurological deficits were reduced 1 day after bilateral compared to unilateral dMCAO.

CONCLUSIONS

Activity in the contralesional cerebral cortex may inhibit functional motor recovery after experimental stroke.

Exercise therapy augments the ischemia-induced proangiogenic state and results in sustained improvement after stroke

The induction of angiogenesis will stimulate endogenous recovery mechanisms, which are involved in the long-term repair and restoration process of the brain after an ischemic event. Here, we tested whether exercise influences the pro-angiogenic factors and outcomes after cerebral infarction in rats. Wistar rats were exposed to two hours of middle-cerebral artery occlusion and reperfusion. Different durations of treadmill training were performed on the rats. The expression of matrix metalloproteinase 2 (MMP2) and vascular endothelial growth factor (VEGF)-related genes and proteins were higher over time post-ischemia, and exercise enhanced their expression. Sixteen days post-ischemia, the regional cerebral blood flow in the ischemic striatum was significantly increased in the running group over the sedentary. Although no difference was seen in infarct size between the running and sedentary groups, running evidently improved the neurobehavioral score. The effects of running on MMP2 expression, regional cerebral blood flow and outcome were abolished when animals were treated with bevacizumab (BEV), a VEGF-targeting antibody. Exercise therapy improves long-term stroke outcome by MMP2-VEGF-dependent mechanisms related to improved cerebral blood flow.

Aberrant neurogenesis after stroke: a retroviral cell labeling study

BACKGROUND AND PURPOSE

Adult neurogenesis in the dentate gyrus is a unique form of brain plasticity that is strongly stimulated after stroke. We investigate the morphological properties of new granule cells, which are born and develop after the ischemic insult, and query whether these adult-born neurons properly integrate into the pre-existing hippocampal circuitries.

METHODS

Two well-established models were used to induce either small cortical infarcts (photothrombosis model) or large territorial infarcts (transient middle cerebral artery occlusion model). New granule cells were labeled 4 days after the initial insult by intrahippocampal injection of a retroviral vector encoding green fluorescent protein and newborn neurons were morphologically analyzed using a semiautomatic Neurolucida system and confocal laser scanning microscopy at 6 weeks.

RESULTS

Approximately 5% to 10% of newborn granule cells displayed significant morphological abnormalities comprising additional basal dendrites and, after middle cerebral artery occlusion, also ectopic cell position. The extent of morphological abnormalities was higher after large territorial infarcts and seems to depend on the severity of ischemic damage. An increased portion of mushroom spines in aberrant neurons suggests stable synaptic integration. However, poststroke generated granule cells with regular appearance also demonstrate alterations in dendritic complexity and spine morphology.

CONCLUSIONS

The remarkable stimulation of dentate neurogenesis after stroke coincides with an increased rate of aberrantly integrated neurons, which may contribute to functional impairments and, hypothetically, favor pathogenesis of adjustment disorders, cognitive deficits, or epilepsy often seen in stroke patients.

Exploring the efficacy of constraint in animal models of stroke: meta-analysis and systematic review of the current evidence

BACKGROUND

Constraint-induced movement therapy (CIMT) is used to counteract learned nonuse observed following stroke in humans and has been shown to improve function. Variations of CIMT used in animal models of stroke have the potential to inform and improve our understanding of this intervention.

OBJECTIVE

To conduct a systematic review of studies investigating constraint in experimental stroke. The authors aimed to assess the quality and establish the efficacy of constraint on neurobehavior, cognitive function, infarct size, and stress and mortality and to determine the optimal dose or time to administration.

METHODS

Systematic review with meta-analysis was used. Data were analyzed using DerSimonian and Laird weighted-mean-difference random effects meta-analysis.

RESULTS

The quality scores of the 8 articles (15 studies) included were moderate (median 5/10; interquartile range, 4.8-6.0). There was a trend for animals with constraint to have worse neurobehavioral scores (-10% worse; 95% confidence interval [CI] = -20 to 0; P = .06). Infarct volumes were not significantly different between groups (-3% larger with constraint; 95% CI = -15 to 9; P = .63). Cognitive function was significantly better after constraint, although this estimate was based on only 28 animals from 2 studies. Insufficient data prevented analysis of the effect of constraint on stress and mortality.

CONCLUSIONS

This meta-analysis showed no benefit of constraint on neurobehavioral scores, which is at odds with some human studies. Animal models may help us efficiently explore the biological basis of rehabilitation interventions; however, review of the data in this study raise uncertainty about its effectiveness in humans.

Delayed intensive acquisition training alleviates the lesion-induced place learning deficits after fimbria-fornix transection in the rat

This study evaluates the effects of two learning paradigms, intensive vs. baseline, on the posttraumatic acquisition of a water maze based place learning task. Rats were subjected either to a control operation (Sham) or to a fimbria-fornix (FF) transection, which renders the hippocampus dysfunctional and disrupts the acquisition of allocentric place learning. All animals were administered 30 post-lesion acquisition sessions, which spanned either 10 or 30days. The acquisition period was followed by a 7day pause after which a retention probe was administered. The lesioned animals were divided into 3 groups: i) Baseline Acquisition Paradigm (BAP) once daily for 30days starting 1week post-surgery; ii) Early Intensive Acquisition Paradigm (EIAP) 3 times daily for 10days starting 1week post-surgery; and iii) Late Intensive Acquisition Paradigm (LIAP) 3 times daily for 10days starting 3weeks post-surgery. Within the control animals, one group followed the schedule of BAP, and one group followed the schedule of Intensive Acquisition Paradigm (IAP). All lesioned animals showed an impaired task acquisition. LIAP was beneficial in FF animals, in that it led to a better acquisition of the place learning task than the two other acquisition paradigms. The FF/EIAP group did not show improved acquisition compared to the FF/BAP group. The control animals were not differentially affected by the two learning schedules. The findings have implications for cognitive rehabilitation after brain injury and support the assumption that intensive treatment can lead to an improved learning, even when the neural structures underlying such a process are compromised. However, the timing of intensive treatment needs to be considered further.

Successful regeneration after experimental stroke by granulocyte-colony stimulating factor is not further enhanced by constraint-induced movement therapy either in concurrent or in sequential combination therapy

BACKGROUND AND PURPOSE

Both application of granulocyte-colony stimulating factor (G-CSF) and constraint-induced movement therapy (CIMT) have been shown to improve outcome after experimental stroke. The aim of the present study was to determine whether concurrent or sequential combination of both therapies will further enhance therapeutic benefit and whether specific modifications in the abundance of various neurotransmitter receptors do occur.

METHODS

Adult male Wistar rats were subjected to photothrombotic ischemia and assigned to the following treatment groups (n=20 each): (1) ischemic control (saline); (2) CIMT (CIMT between poststroke Days 2 and 11; (3) G-CSF (10 μg/kg G-CSF daily between poststroke Days 2 and 11; (4) combined concurrent group (CIMT plus 10 μg/kg G-CSF daily between poststroke Days 2 and 11; and (5) combined sequential group (CIMT between poststroke Days 2 and 11 and 10 μg/kg G-CSF daily between poststroke Days 12 and 21, respectively). Rats were functionally tested before and up to 4 weeks after ischemia. Quantitative receptor autography was performed for N-methyl-d-aspartate, AMPA, and GABA(A) receptors.

RESULTS

Significant improvement of functional outcome was seen in all groups treated with G-CSF alone and in either combination with CIMT, whereas CIMT alone failed to enhance recovery. Infarct sizes and remaining cortical tissue did not differ in the various treatment groups. Failure of significant benefit in the CIMT group was associated with a shift toward inhibition in perilesional and remote cortical regions.

CONCLUSIONS

Our findings disclose G-CSF as the major player for enhanced recovery after experimental stroke, preventing a shift toward inhibition as seen in the CIMT group.

Does the endogenous neurogenic response alter behavioral recovery following stroke?

In response to stroke, the adult brain has the remarkable ability to enhance the proliferation of new cells, which form new neurons in restricted regions. This review focuses on studies that have directly tested the hypothesis that neurogenesis contributes to post-stroke behavioral recovery. The translational potential of this area of research is critically assessed with respect to the selection of appropriate stroke models, subjects, neurogenic regions examined, behavioral tests used, and experimental timecourse. Building upon those studies that suggest an association between endogeneous neurogenesis and improved stroke recovery, we are nonetheless left with the challenge to demonstrate a causal link between neurogenesis and behavioral recovery using new technology.

Effects of constraint-induced movement therapy on neurogenesis and functional recovery after early hypoxic-ischemic injury in mice

AIM

Constraint-induced movement therapy (CIMT) has emerged as a promising therapeutic strategy for improving affected upper limb function in children with hemiplegic cerebral palsy (CP). However, little is known about the changes in the brain that are induced by CIMT. This study was designed to investigate these changes and behavioural performance after CIMT intervention in mice with neonatal hypoxic-ischemic brain injury.

METHOD

We utilized the neonatal hypoxic-ischemic brain injury model established in mice pups. Three weeks after the injury, the mice were randomly assigned to the following three groups: the control group (n = 15), the enriched-environment group (n = 17), and the CIMT with an enriched-environment group (CIMT-EE, n = 15). 5-bromo-2-deoxyuridine (BrdU) was injected daily to label proliferating cells during the 2 weeks of intervention.

RESULTS

The CIMT-EE group showed better fall rate in the horizontal ladder rung walking test (mean 5.4%, SD 3.6%) than either the control (mean 14.3%, SD 7.3%; p = 0.001) or enriched-environment (mean 12.4%, SD 7.7%; p = 0.010) groups 2 weeks after the end of intervention. The CIMT-EE group also showed more neurogenesis (mean 7069 cells/mm³, SD 4017 cells/mm³) than either the control group (mean 1555 cells/mm³, SD 1422 cells/mm³; p < 0.001) or enriched-environment group (mean 2994 cells/mm³, SD 3498 cells/mm³; p = 0.001) in the subventricular zone. In the striatum, neurogenesis in the CIMT-EE group (mean 534 cells/mm³, SD 441 cells/mm³) was greater than in the control group (mean 95 cells/mm³, SD 133 cells/mm³; p = 0.001).

INTERPRETATION

There was CIMT-EE enhanced neurogenesis in the brain along with functional benefits in mice after early hypoxic-ischemic brain injury. This is the first study to demonstrate the effects of CIMT on neurogenesis and functional recovery after experimental injury to an immature brain.

Contribution of constitutively proliferating precursor cell subtypes to dentate neurogenesis after cortical infarcts

Background

It is well known that focal ischemia increases neurogenesis in the adult dentate gyrus of the hippocampal formation but the cellular mechanisms underlying this proliferative response are only poorly understood. We here investigated whether precursor cells which constitutively proliferate before the ischemic infarct contribute to post-ischemic neurogenesis. To this purpose, transgenic mice expressing green fluorescent protein (GFP) under the control of the nestin promoter received repetitive injections of the proliferation marker bromodeoxyuridine (BrdU) prior to induction of cortical infarcts. We then immunocytochemically analyzed the fate of these BrdU-positive precursor cell subtypes from day 4 to day 28 after the lesion.

Results

Quantification of BrdU-expressing precursor cell populations revealed no alteration in number of radial glia-like type 1 cells but a sequential increase of later precursor cell subtypes in lesioned animals (type 2a cells at day 7, type 3 cells/immature neurons at day 14). These alterations result in an enhanced survival of mature neurons 4 weeks postinfarct.

Conclusions

Focal cortical infarcts recruit dentate precursor cells generated already before the infarct and significantly contribute to an enhanced neurogenesis. Our findings thereby increase our understanding of the complex cellular mechanisms of postlesional neurogenesis.