Anti-Nogo-A antibody infusion 24 hours after experimental stroke improved behavioral outcome and corticospinal plasticity in normotensive and spontaneously hypertensive rats

Out of the core: the impact of focal ischemia in regions beyond the penumbra

The changes in the necrotic core and the penumbra following induction of focal ischemia have been the focus of attention for some time. However, evidence shows, that ischemic injury is not confined to the primarily affected structures and may influence the remote areas as well. Yet many studies fail to probe into the structures beyond the penumbra, and possibly do not even find any significant results due to their short-term design, as secondary damage occurs later. This slower reaction can be perceived as a therapeutic opportunity, in contrast to the ischemic core defined as irreversibly damaged tissue, where the window for salvation is comparatively short. The pathologies in remote structures occur relatively frequently and are clearly linked to the post-stroke neurological outcome. In order to develop efficient therapies, a deeper understanding of what exactly happens in the exo-focal regions is necessary. The mechanisms of glia contribution to the ischemic damage in core/penumbra are relatively well described and include impaired ion homeostasis, excessive cell swelling, glutamate excitotoxic mechanism, release of pro-inflammatory cytokines and phagocytosis or damage propagation via astrocytic syncytia. However, little is known about glia involvement in post-ischemic processes in remote areas. In this literature review, we discuss the definitions of the terms "ischemic core", "penumbra" and "remote areas." Furthermore, we present evidence showing the array of structural and functional changes in the more remote regions from the primary site of focal ischemia, with a special focus on glia and the extracellular matrix. The collected information is compared with the processes commonly occurring in the ischemic core or in the penumbra. Moreover, the possible causes of this phenomenon and the approaches for investigation are described, and finally, we evaluate the efficacy of therapies, which have been studied for their anti-ischemic effect in remote areas in recent years.

Corticospinal tract: a new hope for the treatment of post-stroke spasticity

Stroke is the third leading cause of death and disability worldwide. Post-stroke spasticity (PSS) is the most common complication of stroke but represents only one of the many manifestations of upper motor neuron syndrome. As an upper motor neuron, the corticospinal tract (CST) is the only direct descending motor pathway that innervates the spinal motor neurons and is closely related to the recovery of limb function in patients with PSS. Therefore, promoting axonal remodeling in the CST may help identify new therapeutic strategies for PSS. In this review, we outline the pathological mechanisms of PSS, specifically their relationship with CST, and therapeutic strategies for axonal regeneration of the CST after stroke. We found it to be closely associated with astroglial scarring produced by astrocyte activation and its secretion of neurotrophic factors, mainly after the onset of cerebral ischemia. We hope that this review offers insight into the relationship between CST and PSS and provides a basis for further studies.

Anti-Nogo-A Antibody Therapy Improves Functional Outcome Following Traumatic Brain Injury

BACKGROUND

Traumatic brain injury (TBI) can cause sensorimotor deficits, and recovery is slow and incomplete. There are no effective pharmacological treatments for recovery from TBI, but research indicates potential for anti-Nogo-A antibody (Ab) therapy. This Ab neutralizes Nogo-A, an endogenous transmembrane protein that inhibits neuronal plasticity and regeneration.

OBJECTIVE

We hypothesized that anti-Nogo-A Ab treatment following TBI results in disinhibited axonal growth from the contralesional cortex, the establishment of new compensatory neuronal connections, and improved function.

METHODS

We modeled TBI in rats using the controlled cortical impact method, resulting in focal brain damage and motor deficits like those observed in humans with a moderate cortical TBI. Rats were trained on the skilled forelimb reaching task and the horizontal ladder rung walking task. They were then given a TBI, targeting the caudal forelimb motor cortex, and randomly divided into 3 groups: TBI-only, TBI + Anti-Nogo-A Ab, and TBI + Control Ab. Testing resumed 3 days after TBI and continued for 8 weeks, when rats received an injection of the anterograde neuronal tracer, biotinylated dextran amine (BDA), into the corresponding area contralateral to the TBI.

RESULTS

We observed significant improvement in rats that received anti-Nogo-A Ab treatment post-TBI compared to controls. Analysis of BDA-positive axons revealed that anti-Nogo-A Ab treatment resulted in cortico-rubral plasticity to the deafferented red nucleus. Conclusions. Anti-Nogo-A Ab treatment may improve functional recovery via neuronal plasticity to brain areas important for skilled movements, and this treatment shows promise to improve outcomes in humans who have suffered a TBI.

Advances in Antibody-Based Therapeutics for Cerebral Ischemia

Cerebral ischemia is an acute disorder characterized by an abrupt reduction in blood flow that results in immediate deprivation of both glucose and oxygen. The main types of cerebral ischemia are ischemic and hemorrhagic stroke. When a stroke occurs, several signaling pathways are activated, comprising necrosis, apoptosis, and autophagy as well as glial activation and white matter injury, which leads to neuronal cell death. Current treatments for strokes include challenging mechanical thrombectomy or tissue plasminogen activator, which increase the danger of cerebral bleeding, brain edema, and cerebral damage, limiting their usage in clinical settings. Monoclonal antibody therapy has proven to be effective and safe in the treatment of a variety of neurological disorders. In contrast, the evidence for stroke therapy is minimal. Recently, Clone MTS510 antibody targeting toll-like receptor-4 (TLR4) protein, ASC06-IgG1 antibody targeting acid sensing ion channel-1a (ASIC1a) protein, Anti-GluN1 antibodies targeting N-methyl-D-aspartate (NMDA) receptor associated calcium influx, GSK249320 antibody targeting myelin-associated glycoprotein (MAG), anti-High Mobility Group Box-1 antibody targeting high mobility group box-1 (HMGB1) are currently under clinical trials for cerebral ischemia treatment. In this article, we review the current antibody-based pharmaceuticals for neurological diseases, the use of antibody drugs in stroke, strategies to improve the efficacy of antibody therapeutics in cerebral ischemia, and the recent advancement of antibody drugs in clinical practice. Overall, we highlight the need of enhancing blood-brain barrier (BBB) penetration for the improvement of antibody-based therapeutics in the brain, which could greatly enhance the antibody medications for cerebral ischemia in clinical practice.

Modulation of the Microglial Nogo-A/NgR Signaling Pathway as a Therapeutic Target for Multiple Sclerosis

Current therapeutics targeting chronic phases of multiple sclerosis (MS) are considerably limited in reversing the neural damage resulting from repeated inflammation and demyelination insults in the multi-focal lesions. This inflammation is propagated by the activation of microglia, the endogenous immune cell aiding in the central nervous system homeostasis. Activated microglia may transition into polarized phenotypes; namely, the classically activated proinflammatory phenotype (previously categorized as M1) and the alternatively activated anti-inflammatory phenotype (previously, M2). These transitional microglial phenotypes are dynamic states, existing as a continuum. Shifting microglial polarization to an anti-inflammatory status may be a potential therapeutic strategy that can be harnessed to limit neuroinflammation and further neurodegeneration in MS. Our research has observed that the obstruction of signaling by inhibitory myelin proteins such as myelin-associated inhibitory factor, Nogo-A, with its receptor (NgR), can regulate microglial cell function and activity in pre-clinical animal studies. Our review explores the microglial role and polarization in MS pathology. Additionally, the potential therapeutics of targeting Nogo-A/NgR cellular mechanisms on microglia migration, polarization and phagocytosis for neurorepair in MS and other demyelination diseases will be discussed.

Neural recovery after cortical injury: Effects of MSC derived extracellular vesicles on motor circuit remodeling in rhesus monkeys

Reorganization of motor circuits in the cortex and corticospinal tract are thought to underlie functional recovery after cortical injury, but the mechanisms of neural plasticity that could be therapeutic targets remain unclear. Recent work from our group have shown that systemic treatment with mesenchymal stem cell derived (MSCd) extracellular vesicles (EVs) administered after cortical damage to the primary motor cortex (M1) of rhesus monkeys resulted in a robust recovery of fine motor function and reduced chronic inflammation. Here, we used immunohistochemistry for cfos, an activity-dependent intermediate early gene, to label task-related neurons in the surviving primary motor and premotor cortices, and markers of axonal and synaptic plasticity in the spinal cord. Compared to vehicle, EV treatment was associated with a greater density of cfos⁺ pyramidal neurons in the deep layers of M1, greater density of cfos⁺ inhibitory interneurons in premotor areas, and lower density of synapses on MAP2+ lower motor neurons in the cervical spinal cord. These data suggest that the anti-inflammatory effects of EVs may reduce injury-related upper motor neuron damage and hyperexcitability, as well as aberrant compensatory re-organization in the cervical spinal cord to improve motor function.

Nogo-A Is a Potential Prognostic Marker for Spinal Cord Injury

Objective

Spinal cord injury (SCI) has become prevalent worldwide in recent years, and its prognosis is poor and the pathological mechanism has not been fully elucidated. Nogo-A is one of the isoforms of the neurite outgrowth inhibitory protein reticulon 4. The purpose of this study was to determine whether Nogo-A could be used as a marker for predicting the prognosis of SCI.

Methods

We screened eligible SCI patients and controls based on inclusion and exclusion criteria. We also collected baseline clinical information and peripheral venous blood of the enrolled population. Participants' baseline serum Nogo-A levels were measured by enzyme-linked immunosorbent assay (ELISA). The American Spinal Injury Association (ASIA) scale was used to evaluate the prognosis of SCI patients after 3 months.

Results

Baseline clinical information (age; gender; smoking; drinking; SBP, systolic blood pressure; DBP, diastolic blood pressure; fasting blood glucose; WBC, white blood cells; CRP, C-reactive protein) of SCI patients and controls were not statistically significant academic differences (p > 0.05). The baseline serum Nogo-A levels of SCI patients and controls were 192.7 ± 13.9 ng/ml and 263.1 ± 22.4 ng/ml, respectively, and there was a statistically significant difference between the two groups (p < 0.05). We divided SCI patients into 4 groups according to their baseline serum Nogo-A quartile levels and analyzed their relationship with ASIA scores. The trend test results showed that with the increase of Nogo-A level, the ASIA sensation score and ASIA motor score were significantly decreased (p < 0.001). Multivariate regression analysis showed that serum Nogo-A levels remained a potential cause affecting the prognosis of SCI after adjusting for confounding factors in multiple models.

Conclusions

Serum Nogo-A levels were significantly elevated in SCI patients. Moreover, elevated Nogo-A levels often indicate poor prognosis and can be used as a marker to predict the prognosis of SCI.

Inflammatory Response and Secondary White Matter Damage to the Corpus Callosum after Focal Striatal Stroke in Rats

Stroke is one of the leading causes of death and long-term disabilities worldwide, resulting in a debilitating condition occasioned by disturbances in the cerebral vasculature. Primary damage due to metabolic collapse is a quick outcome following stroke, but a multitude of secondary events, including excitotoxicity, inflammatory response, and oxidative stress cause further cell death and functional impairment. In the present work, we investigated whether a primary ischemic damage into the dorsal striatum may cause secondary damage in the circumjacent corpus callosum (CC). Animals were injected with endothelin-1 and perfused at 3, 7, 14, and 30 post-lesion days (PLD). Sections were stained with Cresyl violet for basic histopathology and immunolabeled by antibodies against astrocytes (anti-GFAP), macrophages/microglia (anti-IBA1/anti MHC-II), oligodendrocytes (anti-TAU) and myelin (anti-MBP), and Anti-Nogo. There were conspicuous microgliosis and astrocytosis in the CC, followed by later oligodendrocyte death and myelin impairment. Our results suggest that secondary white matter damage in the CC follows a primary focal striatal ischemia in adult rats.

Biotechnology-based therapeutics for management of cerebral stroke

Cerebral stroke, commonly caused due to hindrance in blood flow, is broadly classified into two categories-ischemic and haemorrhagic strokes. The onset of stroke triggers multiple mechanisms causing inflammation, generation of free radicals and protein damage leading to apoptosis of neuronal cells. The current therapies available for cerebral strokes involve use of complex surgical treatments and tissue plasminogen activator which increases the risk of internal bleeding, brain edema and cerebral damage, thereby restricting their use in clinical setting. The alarming need to develop safe, effective, target specific systems which, promote neuronal growth and reduce cerebral inflammation can be accomplished with use of biotechnological approaches. The article gives an insight to biotechnology-based advancements for tissue plasminogen activators, cell penetrating peptides, growth factors, ribonucleic acid systems and monoclonal antibodies for cerebral stroke. We also emphasis on challenges and future perspective of biotechnology-based therapeutics for better management of stroke.

NogoA-expressing astrocytes limit peripheral macrophage infiltration after ischemic brain injury in primates

Astrocytes play critical roles after brain injury, but their precise function is poorly defined. Utilizing single-nuclei transcriptomics to characterize astrocytes after ischemic stroke in the visual cortex of the marmoset monkey, we observed nearly complete segregation between stroke and control astrocyte clusters. Screening for the top 30 differentially expressed genes that might limit stroke recovery, we discovered that a majority of astrocytes expressed RTN4A/ NogoA, a neurite-outgrowth inhibitory protein previously only associated with oligodendrocytes. NogoA upregulation on reactive astrocytes post-stroke was significant in both the marmoset and human brain, whereas only a marginal change was observed in mice. We determined that NogoA mediated an anti-inflammatory response which likely contributes to limiting the infiltration of peripheral macrophages into the surviving parenchyma.

Inflammatory Cytokines are in Action: Brain Plasticity and Recovery after Brain Ischemia Due to Delayed Melatonin Administration

OBJECTIVES

Post-ischemic inflammation leads to apoptosis as an indirect cause of functional disabilities after the stroke. Melatonin may be a good candidate for the stroke recovery because of its anti-inflammatory effects. Therefore, we investigated the effect of melatonin on inflammation in the functional recovery of brain by evaluating ipsilesional and contralesional alterations.

MATERIALS AND METHODS

Melatonin (4 mg/kg/day) was intraperitoneally administered into the mice from the 3^rd to the 55^th day of the post-ischemia after 30 min of middle cerebral artery occlusion.

RESULTS

Melatonin produced a functional recovery by reducing the emigration of the circulatory leukocytes and the local microglial activation within the ischemic brain. Overall, the expression of the inflammation-related genes reduced upon melatonin treatment in the ischemic hemisphere. On the other hand, the expression level of the inflammatory cytokine genes raised in the contralateral hemisphere at the 55^th day of the post-ischemia. Furthermore, melatonin triggers an increase in the iNOS expression and a decrease in the nNOS expression in the ipsilateral hemisphere at the earlier times in the post-ischemic recovery. At the 55^th day of the post-ischemic recovery, melatonin administration enhanced the eNOS and nNOS protein expressions.

CONCLUSIONS

The present molecular, biological, and histological data have revealed broad anti-inflammatory effects of melatonin in both hemispheres with distinct temporal and spatial patterns at different phases of post-stroke recovery. These outcomes also established that melatonin act recruitment of contralesional rather than of ipsilesional.

Combination of Electroacupuncture and Constraint-Induced Movement Therapy Enhances Functional Recovery After Ischemic Stroke in Rats

Both electroacupuncture and constraint-induced movement therapy have been reported to produce therapeutic effects on the recovery of ischemic stroke. The combined use of these two therapies is not rare clinically, although its effectiveness is not yet clear. We aimed to evaluate the efficacy of the combination of electroacupuncture and constraint-induced movement therapy in ischemic stroke rats, and to explore the potential molecular mechanisms. Ischemic stroke rat models were established by middle cerebral artery occlusion. Then, the rats were assigned to receive one of the following interventions: sole electroacupuncture, sole constraint-induced movement therapy, the combination of both therapies, and no treatment. Functional recovery was assessed with the beam balance test and rotarod test. The infarct volume of the brain and the expression of the molecules Nogo-A, P75^NTR, NGF, BDNF, and VEGF in the brain tissue were investigated. The results demonstrated that the combination of the two therapies significantly improved neurological functional recovery in ischemic stroke rats compared to each therapy alone (P < 0.01). We also observed a significant decrease in infarct volume in rats receiving the combined treatment. Nogo-A and P75^NTR were downregulated and NGF, BDNF, and VEGF were upregulated in the combined treatment rats compared to the control rats. In conclusion, the combination of electroacupuncture and constraint-induced movement therapy enhanced functional recovery after ischemic stroke in rats, and it is a promising treatment strategy in the rehabilitation of stroke. The anti-Nogo-A effect of electroacupuncture may explain its good compatibility with CIMT in ischemic stroke rats.

Environmental enrichment during the chronic phase after experimental stroke promotes functional recovery without synergistic effects of EphA4 targeted therapy

Worldwide, stroke is the main cause of long-term adult disability. After the initial insult, most patients undergo a subacute period with intense plasticity and rapid functional improvements. This period is followed by a chronic phase where recovery reaches a plateau that is only partially modifiable by rehabilitation. After experimental stroke, various subacute rehabilitation paradigms improve recovery. However, in order to reach the best possible outcome, a combination of plasticity-promoting strategies and rehabilitation might be necessary. EphA4 is a negative axonal guidance regulator during development. After experimental stroke, reduced EphA4 levels improve functional outcome with similar beneficial effects upon the inhibition of EphA4 downstream targets. In this study, we assessed the effectiveness of a basic enriched environment in the chronic phase after photothrombotic stroke in mice as well as the therapeutic potential of EphA4 targeted therapy followed by rehabilitation. Our findings show that environmental enrichment in the chronic phase improves functional outcome up to 2 months post-stroke. Although EphA4 levels increase after experimental stroke, subacute EphA4 inhibition followed by environmental enrichment does not further increase recovery. In conclusion, we show that environmental enrichment during the chronic phase of stroke improves functional outcome in mice with no synergistic effects of the used EphA4 targeted therapy.

Acute spinal cord injury: Pathophysiology and pharmacological intervention (Review)

Spinal cord injury (SCI) is one of the most debilitating of all the traumatic conditions that afflict individuals. For a number of years, extensive studies have been conducted to clarify the molecular mechanisms of SCI. Experimental and clinical studies have indicated that two phases, primary damage and secondary damage, are involved in SCI. The initial mechanical damage is caused by local impairment of the spinal cord. In addition, the fundamental mechanisms are associated with hyperflexion, hyperextension, axial loading and rotation. By contrast, secondary injury mechanisms are led by systemic and cellular factors, which may also be initiated by the primary injury. Although significant advances in supportive care have improved clinical outcomes in recent years, a number of studies continue to explore specific pharmacological therapies to minimize SCI. The present review summarized some important pathophysiologic mechanisms that are involved in SCI and focused on several pharmacological and non‑pharmacological therapies, which have either been previously investigated or have a potential in the management of this debilitating injury in the near future.

MiR-17-92 enriched exosomes derived from multipotent mesenchymal stromal cells enhance axon-myelin remodeling and motor electrophysiological recovery after stroke

MiR-17-92 cluster enriched exosomes derived from multipotent mesenchymal stromal cells (MSCs) increase functional recovery after stroke. Here, we investigate the mechanisms underlying this recovery. At 24 h (h) post transient middle cerebral artery occlusion, rats received control liposomes or exosomes derived from MSCs infected with pre-miR-17-92 expression lentivirus (Exo-miR-17-92⁺) or control lentivirus (Exo-Con) intravenously. Compared to the liposomes, exosomes significantly reduced the intracortical microstimulation threshold current of the contralateral cortex for evoking impaired forelimb movements (day 21), increased the neurite and myelin density in the ischemic boundary area, and contralesional axonal sprouting into the caudal forelimb area of ipsilateral side and in the denervated spinal cord (day 28), respectively. The Exo-miR-17-92⁺ further enhanced axon-myelin remodeling and electrophysiological recovery compared with the EXO-Con. Ex vivo cultured rat brain slice data showed that myelin and neuronal fiber density were significantly increased by Exo-miR-17-92⁺, while significantly inhibited by application of the PI3K/Akt/mTOR pathway inhibitors. Our studies suggest that the miR-17-92 cluster enriched MSC exosomes enhanced neuro-functional recovery of stroke may be attributed to an increase of axonal extension and myelination, and this enhanced axon-myelin remodeling may be mediated in part via the activation of the PI3K/Akt/mTOR pathway induced by the downregulation of PTEN.

Axonal remodeling of the corticospinal tract during neurological recovery after stroke

Stroke remains the leading cause of long-term disability. Hemiparesis is one of the most common post-stroke motor deficits and is largely attributed to loss or disruption of the motor signals from the affected motor cortex. As the only direct descending motor pathway, the corticospinal tract (CST) is the primary pathway to innervate spinal motor neurons, and thus, forms the neuroanatomical basis to control the peripheral muscles for voluntary movements. Here, we review evidence from both experimental animals and stroke patients, regarding CST axonal damage, functional contribution of CST axonal integrity and remodeling to neurological recovery, and therapeutic approaches aimed to enhance CST axonal remodeling after stroke. The new insights gleaned from preclinical and clinical studies may encourage the development of more rational therapeutics with a strategy targeted to promote axonal rewiring for corticospinal innervation, which will significantly impact the current clinical needs of subacute and chronic stroke treatment.

Extracellular DNA-A Danger Signal Triggering Immunothrombosis

Clotting and inflammation are effective danger response patterns positively selected by evolution to limit fatal bleeding and pathogen invasion upon traumatic injuries. As a trade-off, thrombotic, and thromboembolic events complicate severe forms of infectious and non-infectious states of acute and chronic inflammation, i.e., immunothrombosis. Factors linked to thrombosis and inflammation include mediators released by platelet granules, complement, and lipid mediators and certain integrins. Extracellular deoxyribonucleic acid (DNA) was a previously unrecognized cellular component in the blood, which elicits profound proinflammatory and prothrombotic effects. Pathogens trigger the release of extracellular DNA together with other pathogen-associated molecular patterns. Dying cells in the inflamed or infected tissue release extracellular DNA together with other danger associated molecular pattern (DAMPs). Neutrophils release DNA by forming neutrophil extracellular traps (NETs) during infection, trauma or other forms of vascular injury. Fluorescence tissue imaging localized extracellular DNA to sites of injury and to intravascular thrombi. Functional studies using deoxyribonuclease (DNase)-deficient mouse strains or recombinant DNase show that extracellular DNA contributes to the process of immunothrombosis. Here, we review rodent models of immunothrombosis and the evolving evidence for extracellular DNA as a driver of immunothrombosis and discuss challenges and prospects for extracellular DNA as a potential therapeutic target.

Protracted Morphological Changes in the Corticospinal Tract Within the Cervical Spinal Cord After Intracerebral Hemorrhage in the Right Striatum of Mice

Intracerebral hemorrhage (ICH) is associated with high morbidity and mortality rates. Currently, there is no promising treatment that improves prognosis significantly. While a thorough investigation of the pathological process within the primary site of injury in the brain has been conducted by the research field, the focus was mainly on gray matter injury, which partly accounted for the failure of discovery of clinically efficacious treatments. It is not until recent years that white matter (WM) injury in the brain after subcortical ICH was examined. As WM tracts form networks between different regions, damage to fibers should impair brain connectivity, resulting in functional impairment. Although WM changes have been demonstrated in the brain after ICH, alterations distant from the initial injury site down in the spinal cord are unclear. This longitudinal study, for the first time, revealed prolonged morphological changes of the contralesional dorsal corticospinal tract (CST) in the spinal cord 5 weeks after experimental ICH in mice by confocal microscopy and transmission electron microscopy, implying that the structural integrity of the CST was compromised extensively after ICH. Given the important role of CST in motor function, future translational studies targeting motor recovery should delineate the treatment effects on CST integrity.

Antibody signatures in patients with histopathologically defined multiple sclerosis patterns

Early active multiple sclerosis (MS) lesions can be classified histologically into three main immunopathological patterns of demyelination (patterns I–III), which suggest pathogenic heterogeneity and may predict therapy response. Patterns I and II show signs of immune-mediated demyelination, but only pattern II is associated with antibody/complement deposition. In pattern III lesions, which include Baló’s concentric sclerosis, primary oligodendrocyte damage was proposed. Serum antibody reactivities could reflect disease pathogenesis and thus distinguish histopathologically defined MS patterns. We established a customized microarray with more than 700 peptides that represent human and viral antigens potentially relevant for inflammatory demyelinating CNS diseases, and tested sera from 66 patients (pattern I n = 12; II n = 29; III n = 25, including 8 with Baló’s), healthy controls, patients with Sjögren’s syndrome and stroke patients. Cell-based assays were performed for aquaporin 1 (AQP1) and AQP4 antibody detection. No single peptide showed differential binding among study cohorts. Because antibodies can react with different peptides from one protein, we also analyzed groups of peptides. Patients with pattern II showed significantly higher reactivities to Nogo-A peptides as compared to patterns I (p = 0.02) and III (p = 0.02). Pattern III patients showed higher reactivities to AQP1 (compared to pattern I p = 0.002, pattern II p = 0.001) and varicella zoster virus (VZV, compared to pattern II p = 0.05). In patients with Baló’s, AQP1 reactivity was also significantly higher compared to patients without Baló’s (p = 0.04), and the former revealed distinct antibody signatures. Histologically, Baló’s patients showed loss of AQP1 and AQP4 in demyelinating lesions, but no antibodies binding conformational AQP1 or AQP4 were detected. In summary, higher reactivities to Nogo-A peptides in pattern II patients could be relevant for enhanced axonal repair and remyelination. Higher reactivities to AQP1 peptides in pattern III patients and its subgroup of Baló’s patients possibly reflect astrocytic damage. Finally, latent VZV infection may cause peripheral immune activation.

Blockade of Nogo-A/Nogo-66 receptor 1 (NgR1) Inhibits Autophagic Activation and Prevents Secondary Neuronal Damage in the Thalamus after Focal Cerebral Infarction in Hypertensive Rats

Focal cerebral infarction leads to autophagic activation, which contributes to secondary neuronal damage in the ipsilateral thalamus. Although Nogo-A deactivation enhances neuronal plasticity, its role in autophagic activation in the thalamus after ischemic stroke remains unclear. This study aimed to investigate the potential roles of Nogo-A/Nogo-66 receptor 1 (NgR1) in autophagic activation in the ipsilateral thalamus after cerebral infarction. Focal neocortical infarction was established using the middle cerebral artery occlusion (MCAO) method. Secondary damage in the ipsilateral thalamus was assessed by Nissl staining and immunostaining. The expression of Nogo-A, NgR1, Rho-A and Rho-associated coiled-coil containing protein kinase 1 (ROCK1) as well as autophagic flux were evaluated by immunofluorescence and immunoblotting. The roles of Nogo-A-NgR1 signaling in autophagic activation were determined by intraventricular delivery of an NgR1 antagonist peptide, NEP1-40, at 24 h after MCAO. The results showed that Nogo-A and NgR1 overexpression temporally coincided with marked increases in the levels of Beclin1, LC3-II and sequestosome 1 (SQSTM1)/p62 in the ipsilateral thalamus at seven and fourteen days after MCAO. In contrast, NEP1-40 treatment significantly reduced the expression of Rho-A and ROCK1 which was accompanied by marked reductions of LC3-II conversion as well as the levels of Beclin1 and SQSTM1/p62. Furthermore, NEP1-40 treatment significantly reduced neuronal loss and gliosis in the ipsilateral thalamus, and accelerated somatosensory recovery at the observed time-points after MCAO. These results suggest that blockade of Nogo-A-NgR1 signaling inhibits autophagic activation, attenuates secondary neuronal damage in the ipsilateral thalamus, and promotes functional recovery after focal cerebral cortical infarction.

Opportunities and Limitations of Vascular Risk Factor Models in Studying Plasticity-Promoting and Restorative Ischemic Stroke Therapies

Major efforts are currently made promoting neuronal plasticity and brain remodeling in the postacute stroke phase. Experimental studies evaluating new stroke therapies are mostly performed in rodents, which compared to humans exhibit a short lifespan. These studies widely employ young, otherwise healthy, rodents that lack the vascular risk factors and comorbidities of stroke patients. These risk factors compromise postischemic neurological recovery and brain plasticity and in several contexts reduce the brain responsiveness to recovery-inducing plasticity-promoting treatments. By examining risk factor models, which have hitherto been used for studying experimentally induced ischemic stroke, this review outlines the possibilities and limitations of risk factor models in the evaluation of plasticity-promoting and restorative stroke treatments.

Bundled Three-Dimensional Human Axon Tracts Derived from Brain Organoids

Reestablishing cerebral connectivity is a critical part of restoring neuronal network integrity and brain function after trauma, stroke, and neurodegenerative diseases. Creating transplantable axon tracts in the laboratory is an unexplored strategy for overcoming the common barriers limiting axon regeneration in vivo, including growth-inhibiting factors and the limited outgrowth capacity of mature neurons in the brain. We describe the generation, phenotype, and connectivity of constrained three-dimensional human axon tracts derived from brain organoids. These centimeter-long constructs are encased in an agarose shell that permits physical manipulation and are composed of discrete cellular regions spanned by axon tracts, mirroring the separation of cerebral gray and white matter. Features of cerebral cortex also are emulated, as evidenced by the presence of neurons with different cortical layer phenotypes. This engineered neural tissue represents a first step toward potentially reconstructing brain circuits by physically replacing neuronal populations and long-range axon tracts in the brain.

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Transplantable 3D axon tracts are tissue engineered from human brain organoids

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Growth of organoid axons in a hydrogel column is enhanced compared with planar culture

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Organoids within engineered columns can maintain a laminar cortical architecture

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Functional connectivity across the construct is demonstrated using calcium imaging

Improved functional outcome after chronic stroke with delayed anti-Nogo-A therapy: A clinically relevant intention-to-treat analysis

Many preclinical treatment strategies for stroke have failed when tested in human trials. Although the reasons for these translation failures are multifactorial, one potential concern is the statistical analysis of the preclinical data. One way to rigorously evaluate new therapies is to use an intention-to-treat analysis in preclinical studies. Therefore, in this study, we set out to evaluate the treatment efficacy of a potential clinically relevant therapeutic agent for stroke, i.e., anti-Nogo-A immunotherapy, using an intention-to-treat analysis. Adult rats were trained on the skilled forelimb reaching task and subsequently underwent an ischemic stroke. Nine weeks later, the rats either received intracerebroventricular anti-Nogo-A antibody, control antibody, or no treatment. Skilled reaching performance was assessed by a non-linear model using both an intention-to-treat and per-protocol analysis. Following testing, dendritic complexity was evaluated in the contralesional and perilesional sensorimotor cortex. Both intention-to-treat and per-protocol analysis showed that anti-Nogo-A immunotherapy resulted in statistically significant improved recovery on the skilled forelimb reaching task, although treatment effect was less (though statistically significant) in the intention-to-treat group. Improved functional performance was not shown to be associated with dendritic changes. In conclusion, this study provides evidence for the importance of using intention-to-treat paradigms in testing preclinical therapeutic strategies.

Low-Dose Evans Blue Dye for Near-Infrared Fluorescence Imaging in Photothrombotic Stroke Model

Background: Evans blue dye (EBD) is the most common indicator to analyze the extent of blood-brain barrier (BBB) breakdown in several neurological disease models. However, the high-dose of EBD (51.9 mg/kg) is usually required for visualization of blue color by the human eye that brings potential safety issues. Methods: To solve this problem, low-dose of EBD was applied for the near-infrared (NIR) fluorescence-assisted quantitation of BBB breakdown in photothrombotic stoke model. Animals were allocated to seven dose groups ranging from 1.35 nmol (5.19 μg/kg) to 13.5 μmol (51.9 mg/kg) EBD. Results: EBD was undetectable in the non-ischemic brain tissue, and the fluorescence signals in the infarcted hemisphere seemed proportional to the injected dose in the dose range. Although the maximum fluorescence signals in brain tissue were obtained with the injections of 1.35 nmol ~ 13.5 μmol EBD, the background signals in the neighboring brain tissues were significantly increased as well. Since the high concentration of EBD is necessary for color-based identification of the infarcted lesion in brain tissues, even 10-fold diluted could not be distinguished visually by naked eye. Conclusions: NIR fluorescence-assisted method could potentially provide new opportunities to study BBB leakage just using small amount of EBD in different pathological conditions and to test the efficacy of various therapeutic strategies to protect the BBB.

LOTUS overexpression accelerates neuronal plasticity after focal brain ischemia in mice

Nogo receptor-1 (NgR1) and its ligands inhibit neuronal plasticity and limit functional recovery after brain damage such as ischemic stroke. We have previously shown that lateral olfactory tract usher substance (LOTUS) antagonizes NgR1-mediated signaling. Here, we investigated whether LOTUS enhances neuronal plasticity and functional recovery after brain focal ischemia in adult mice. Focal ischemic infarcts were induced in wild-type and LOTUS-overexpressing transgenic mice via middle cerebral artery occlusion. Endogenous LOTUS expression was increased in brain and cervical spinal cord of the contralateral side of ischemia in the chronic phase after brain ischemia. LOTUS overexpression accelerated midline-crossing axonal sprouting from the contralateral side to the ipsilateral side of ischemia in the medullar reticular formation and gray matter of denervated cervical spinal cord. Importantly, LOTUS overexpression improved neurological score highly correlated with laterality ratio of corticoreticular fibers of the medulla oblongata, indicating that LOTUS overexpression may overcome the inhibitory environment induced by NgR1 signaling for damaged motor pathway reconstruction after ischemic stroke. Thus, our data suggest that LOTUS overexpression accelerates neuronal plasticity in the brainstem and cervical spinal cord after stroke and LOTUS administration is useful for future therapeutic strategies.

NogoA Neutralization Promotes Axonal Restoration After White Matter Injury In Subcortical Stroke

Blocking axonal growth inhibitor NogoA has been of great interest for promoting axonal recovery from neurological diseases. The present study investigates the therapeutic effects of blocking NogoA, inducing functional recovery and promoting white matter repair in an experimental animal model of stroke. Adult male rats were subjected to white matter injury by subcortical ischemic stroke. Twenty-four hours after surgery, 250 ug of anti-NogoA or anti-IgG-1 were administered through the tail vein. The quantity of NogoA protein was determined by immunohistochemistry in the brain and peripheral organs. In addition, functional status, lesion size, fiber tract integrity, axonal sprouting and white matter repair markers were analyzed. Moreover, an in vitro study was performed in order to strengthen the results obtained in vivo. A lower quantity of NogoA protein was found in the brain and peripheral organs of the animals that received anti-NogoA treatment. The animals receiving anti-NogoA treatment showed significantly better results in terms of functional recovery, fiber tract integrity, axonal sprouting and white matter repair markers compared with the control group at 28 days. White matter integrity was in part restored by antibody-mediated inhibition of NogoA administration in those animals that were subjected to an axonal injury by subcortical stroke. This white matter restoration triggered functional recovery.

The Involvement of the Myelin-Associated Inhibitors and Their Receptors in CNS Plasticity and Injury

The limited capacity for the central nervous system (CNS) to repair itself was first described over 100 years ago by Spanish neuroscientist Ramon Y. Cajal. However, the exact mechanisms underlying this failure in neuronal regeneration remain unclear and, as such, no effective therapeutics yet exist. Numerous studies have attempted to elucidate the biochemical and molecular mechanisms that inhibit neuronal repair with increasing evidence suggesting that several inhibitory factors and repulsive guidance cues active during development actually persist into adulthood and may be contributing to the inhibition of repair. For example, in the injured adult CNS, there are various inhibitory factors that impede the outgrowth of neurites from damaged neurons. One of the most potent of these neurite outgrowth inhibitors is the group of proteins known as the myelin-associated inhibitors (MAIs), present mainly on the membranes of oligodendroglia. Several studies have shown that interfering with these proteins can have positive outcomes in CNS injury models by promoting neurite outgrowth and improving functional recovery. As such, the MAIs, their receptors, and downstream effectors are valid drug targets for the treatment of CNS injury. This review will discuss the current literature on MAIs in the context of CNS development, plasticity, and injury. Molecules that interfere with the MAIs and their receptors as potential candidates for the treatment of CNS injury will additionally be introduced in the context of preclinical and clinical trials.

ZW800-1 for Assessment of Blood-Brain Barrier Disruption in a Photothrombotic Stroke Model

Background: Since it is known that serum albumin-bound dyes can cross the blood-brain barrier (BBB) after ischemia, Evans Blue dye is commonly used to assess BBB disruption because of its rapid binding to serum albumin. In addition, indocyanine green (ICG), a clinically available dye, binds to serum proteins that could also be used for assessment of BBB impairment. Unlike these near-infrared (NIR) dyes, zwitterionic NIR fluorophore (ZW800-1) shows no serum binding, ultralow non-specific tissue uptake, and rapid elimination from the body via renal filtration. In this study, we report the use of ZW800-1 as a NIR fluorescence imaging agent for detecting BBB disruption in rat stroke models. Methods: Three types of NIR fluorophores, Evans Blue, ICG, and ZW800-1, were administered intraperitoneally into rat photothrombotic stroke models by using 4% concentration of each NIR dye. The NIR fluorescence signals in the infarcted brain tissue and biodistribution were observed in real-time using the Mini-FLARE^® imaging system up to 24 h post-injection. Results: ZW800-1 provided successful visualization of the ischemic injury site in the brain tissue, while the remaining injected dye was clearly excreted from the body within a certain period of time. Although Evans Blue and ICG provided mapping of the infarcted brain lesions, they exhibited high non-specific uptake in most of the tissues and organs and persisted in the body over 24 h post-injection. Conclusion: Our results suggest the promising application of ZW800-1 as a new strategy in BBB experiments and future therapeutic development.

Neurodegeneration and Glial Response after Acute Striatal Stroke: Histological Basis for Neuroprotective Studies

Stroke is a leading cause of death and neurological disability worldwide and striatal ischemic stroke is frequent in humans due to obstruction of middle cerebral artery. Several pathological events underlie damage progression and a comprehensive description of the pathological features following experimental stroke in both acute and chronic survival times is a necessary step for further functional studies. Here, we explored the patterns of microglial activation, astrocytosis, oligodendrocyte damage, myelin impairment, and Nogo-A immunoreactivity between 3 and 30 postlesion days (PLDs) after experimental striatal stroke in adult rats induced by microinjections of endothelin-1 (ET-1). The focal ischemia induced tissue loss concomitant with intense microglia activation between 3 and 14 PLDs (maximum at 7 PLDs), decreasing afterward. Astrocytosis was maximum around 7 PLDs. Oligodendrocyte damage and Nogo-A upregulation were higher at 3 PLDs. Myelin impairment was maximum between 7 and 14 PLDs. Nogo-A expression was higher in the first week in comparison to control. The results add important histopathological features of ET-1 induced stroke in subacute and chronic survival times. In addition, the establishment of the temporal evolution of these neuropathological events is an important step for future studies seeking suitable neuroprotective drugs targeting neuroinflammation and white matter damage.

Surgical Approach for Middle Cerebral Artery Occlusion and Reperfusion Induced Stroke in Mice

Stroke is a leading cause of death worldwide and continues to be one of the major causes of long-term adult disabilities. About 87% of strokes are ischemic in origin and occur in the territory of the middle cerebral artery (MCA). Currently the only Food and Drug Administration (FDA) approved drug for the treatment of this devastating disease is tissue plasminogen activator (tPA). However, tPA has a small therapeutic window for administration (3 - 6 hr), and is only effective in 4% of the patients who actually receive it. Current research focuses on understanding the pathophysiology of stroke in order to find potential therapeutic targets. Thus, reliable models are crucial, and the MCA occlusion (MCAo) model (also termed the intraluminal filament or suture model) is deemed to be the most clinically relevant surgical model of ischemic stroke, and is fairly non-invasive and easily reproducible. Typically the MCAo model is used with rodents, especially with mice due to all the genetic variations available for this species. Here we describe (and present in the video) how to successfully perform the MCAo model (with reperfusion) in mice to generate reliable and reproducible data.

Anti-Nogo-A Immunotherapy Does Not Alter Hippocampal Neurogenesis after Stroke in Adult Rats

Ischemic stroke is a leading cause of adult disability, including cognitive impairment. Our laboratory has previously shown that treatment with function-blocking antibodies against the neurite growth inhibitory protein Nogo-A promotes functional recovery after stroke in adult and aged rats, including enhancing spatial memory performance, for which the hippocampus is critically important. Since spatial memory has been linked to hippocampal neurogenesis, we investigated whether anti-Nogo-A treatment increases hippocampal neurogenesis after stroke. Adult rats were subject to permanent middle cerebral artery occlusion followed 1 week later by 2 weeks of antibody treatment. Cellular proliferation in the dentate gyrus was quantified at the end of treatment, and the number of newborn neurons was determined at 8 weeks post-stroke. Treatment with both anti-Nogo-A and control antibodies stimulated the accumulation of new microglia/macrophages in the dentate granule cell layer, but neither treatment increased cellular proliferation or the number of newborn neurons above stroke-only levels. These results suggest that anti-Nogo-A immunotherapy does not increase post-stroke hippocampal neurogenesis.

Regulation of Caveolin-1 Expression Determines Early Brain Edema After Experimental Focal Cerebral Ischemia

Background and Purpose—

Most patients with cerebral infarction die of brain edema because of the breakdown of the blood–brain barrier (BBB) in ischemic tissue. Caveolins (a group of proteins) are key modulators of vascular permeability; however, a direct role of caveolin-1 (Cav-1) in the regulation of BBB permeability during ischemic injury has yet to be identified.

Methods—

Cav-1 expression was measured by immunoblotting after photothrombotic ischemia. A direct functional role of Cav-1 in cerebral edema and BBB permeability during cerebral ischemia was investigated by genetic manipulation (gene disruption and re-expression) of Cav-1 protein expression in mice.

Results—

There was a significant correlation between the extent of BBB disruption and the Cav-1 expression. In Cav-1–deficient (Cav-1 −/− ) mice, the extent of BBB disruption after cerebral ischemia was increased compared with wild-type (Cav-1 +/+ ) mice, whereas the increase in cerebral edema volume was ameliorated by lentiviral-mediated re-expression of Cav-1. Furthermore, Cav-1 −/− mice had significantly higher degradation of tight junction proteins and proteolytic activity of matrix metalloproteinase than Cav-1 +/+ mice. Conversely, re-expression of Cav-1 in Cav-1 −/− mice restored tight junction protein expression and reduced matrix metalloproteinase proteolytic activity.

Conclusions—

These results indicate that Cav-1 is a critical determinant of BBB permeability. Strategies for regulating Cav-1 represent a novel therapeutic approach to controlling BBB disruption and subsequent neurological deterioration during cerebral ischemia.

Optogenetic modulation in stroke recovery

Stroke is one of the leading contributors to morbidity, mortality, and health care costs in the United States. Although several preclinical strategies have shown promise in the laboratory, few have succeeded in the clinical setting. Optogenetics represents a promising molecular tool, which enables highly specific circuit-level neuromodulation. Here, the conceptual background and preclinical body of evidence for optogenetics are reviewed, and translational considerations in stroke recovery are discussed.

Nogo-A Neutralization Improves Graft Function in a Rat Model of Parkinson's Disease

Transplantation of fetal human ventral mesencephalic (VM) dopaminergic neurons into the striatum is a promising strategy to compensate for the characteristic dopamine deficit observed in Parkinson’s disease (PD). This therapeutic approach, however, is currently limited by the high number of fetuses needed for transplantation and the poor survival and functional integration of grafted dopaminergic neurons into the host brain. Accumulating evidence indicates that contrasting inhibitory signals endowed in the central nervous system (CNS) might support neuronal regeneration. Hence, in the present study we aimed at improving survival and integration of grafted cells in the host brain by neutralizing Nogo-A, one of the most potent neurite growth inhibitors in the CNS. For that purpose, VM tissue cultures were transplanted into rats with a partial 6-hydroxydopamine (6-OHDA) lesion causing a hemi-PD model and concomitantly treated for 2 weeks with intra-ventricular infusion of neutralizing anti-Nogo-A antibodies. Motor behavior using the cylinder test was assessed prior to and after transplantation as functional outcome. At the end of the experimental period the number of dopaminergic fibers growing into the host brain, the number of surviving dopaminergic neurons in the grafts as well as graft size was examined. We found that anti-Nogo-A antibody infusion significantly improved the asymmetrical forelimb use observed after lesions as compared to controls. Importantly, a significantly three-fold higher dopaminergic fiber outgrowth from the transplants was detected in the Nogo-A antibody treated group as compared to controls. Furthermore, Nogo-A neutralization showed a tendency for increased survival of dopaminergic neurons (by two-fold) in the grafts. No significant differences were observed for graft volume and the number of dopaminergic neurons co-expressing G-protein-coupled inward rectifier potassium channel subunit two between groups. In sum, our findings support the view that neutralization of Nogo-A in the host brain may offer a novel and therapeutically meaningful intervention for cell transplantation approaches in PD.

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.

New Insights into the Roles of Nogo-A in CNS Biology and Diseases

Nogos have become a hot topic for its well-known number Nogo-A's big role in clinical matters. It has been recognized that the expression of Nogo-A and the receptor NgR1 inhibit the neuron's growth after CNS injuries or the onset of the MS. The piling evidence supports the notion that the Nogo-A is also involved in the synaptic plasticity, which was shown to negatively regulate the strength of synaptic transmission. The occurrence of significant schizophrenia-like behavioral phenotypes in Nogo-A KO rats also added strong proof to this conclusion. This review mainly focuses on the structure of Nogo-A and its corresponding receptor-NgR1, its intra- and extra-cellular signaling, together with its major physiological functions such as regulation of migration and distribution and its related diseases like stroke, AD, ALS and so on.

Protective effect of a novel Rho kinase inhibitor WAR-5 in experimental autoimmune encephalomyelitis by modulating inflammatory response and neurotrophic factors

The Rho-kinase (ROCK) inhibitor Fasudil has proven beneficial in experimental autoimmune encephalomyelitis (EAE). Given the small safety window of Fasudil, we are looking for novel ROCK inhibitors, which have similar or stronger effect on EAE with greater safety. In this study, we report that WAR-5, a Y-27632 derivative, alleviates the clinical symptoms, attenuates myelin damage and reduces CNS inflammatory responses in EAE C57BL/6 mice at an extent similar to Fasudil, while exhibits less vasodilator and adverse reaction in vivo. WAR-5 inhibits ROCK activity, and selectively suppresses the expression of ROCK II in spleen, brain and spinal cord of EAE mice, especially in spinal cord, accompanied by decreased expression of Nogo. WAR-5 also regulates the imbalance of Th1/Th17 T cells and regulatory T cells, inhibits inflammatory microenvironment induced with NF-κB-IL-1β pathway. Importantly, WAR-5 converts M1 toward M2 microglia/macrophages that are positively correlated with BDNF and NT-3 production. Taken together, WAR-5 exhibits therapeutic potential in EAE by more selectively inhibits ROCK II, with a greater safety than Fasudil, and is worthy of further clinical study to clarify its clinical value.

Diffusion tensor imaging change in crus cerebri in striatocapsular infarction and correlation with upper extremity motor dysfunction

PURPOSE

There is limited information about the secondary changes in the pyramidal tract after some specific types of deep brain infarction including striatocapsular infarction. The aims of the current study were to investigate diffusion changes in the crus cerebri in patients with striatocapsular infarction using diffusion tensor imaging (DTI), and analyze the relationship between such changes and upper extremity motor dysfunction.

MATERIALS AND METHODS

Fifteen patients with acute onset of striatocapsular infarction and unilateral upper extremity motor dysfunction for the first time were studied prospectively. DTI was performed 2 weeks after disease onset, fractional anisotropy and mean diffusivity values of the bilateral crus cerebri were measured, the asymmetry indices of bilateral fractional anisotropy were calculated, and the relationship between the asymmetry index value and the Fugl-Meyer assessment score for the affected upper extremity function was evaluated.

RESULTS

Two weeks after disease onset, the fractional anisotropy value of the affected crus cerebri was reduced significantly compared with that of the unaffected crus cerebri (0.69 vs. 0.77; p < 0.001); there was no significant difference between bilateral mean diffusivity values. After correction for infarct size (448.93 ± 227.67 mm(2)) there was a negative correlation between the asymmetry index value and the Fugl-Meyer assessment score of the affected upper extremity (r = -0.78, p = 0.001).

CONCLUSIONS

DTI can detect the diffusion change in the crus cerebri in patients with striatocapsular infarction during the early stage of the disease and the integrity of the pyramidal tract in the crus cerebri is closely related to the motor function of the affected upper extremity.

Cortical selective neuronal loss, impaired behavior, and normal magnetic resonance imaging in a new rat model of true transient ischemic attacks

BACKGROUND AND PURPOSE

New-definition transient ischemic attacks (TIAs) are frequent but difficult to diagnose because magnetic resonance imaging (MRI)-negative by definition. However, hidden underlying cell damage might be present and account for the reported long-lasting cognitive impairment after TIAs. Most prior rodent models of true TIA targeted the striatum or have not been fully characterized. Here we present the MRI, behavioral, and quantitative cell changes characterizing a new rodent model of true TIA targeting the more behaviorally relevant cerebral cortex.

METHODS

Fifteen-minute distal middle cerebral artery occlusion was performed in 29 spontaneously hypertensive rats allowed to survive for 7 to 60 days. Behavior was assessed serially using both global neurological and fine sensorimotor tests. Diffusion- and T2-weighted MRI was obtained 20 min postreperfusion and again 7 to 60 days later, and then changes in neurons and microglia were quantified across the middle cerebral artery territory using immunohistochemistry.

RESULTS

No MRI changes or pan-necrosis were observed at any time point, but patchy cortical selective neuronal loss affected 28/29 rats, regardless of survival interval, together with topographically congruent microglial activation that gradually declined over time. The Neuroscore was unchanged, but there was marked contralateral sensorimotor impairment, still recovering by day 28.

CONCLUSIONS

Our new rodent model mimicking true cortical TIA is characterized by normal MRI, but consistent cortical selective neuronal loss and microglial activation and long-lasting sensorimotor deficits. By causing selective neuronal loss, TIAs and silent microemboli might affect neuronal reserve, thereby increasing long-term cognitive impairment risk. Selective neuronal loss and microglial activation might represent novel therapeutic targets that could be detectable in vivo after TIAs using appropriate imaging tracers.

Spinal cord regeneration

Three theories of regeneration dominate neuroscience today, all purporting to explain why the adult central nervous system (CNS) cannot regenerate. One theory proposes that Nogo, a molecule expressed by myelin, prevents axonal growth. The second theory emphasizes the role of glial scars. The third theory proposes that chondroitin sulfate proteoglycans (CSPGs) prevent axon growth. Blockade of Nogo, CSPG, and their receptors indeed can stop axon growth in vitro and improve functional recovery in animal spinal cord injury (SCI) models. These therapies also increase sprouting of surviving axons and plasticity. However, many investigators have reported regenerating spinal tracts without eliminating Nogo, glial scar, or CSPG. For example, many motor and sensory axons grow spontaneously in contused spinal cords, crossing gliotic tissue and white matter surrounding the injury site. Sensory axons grow long distances in injured dorsal columns after peripheral nerve lesions. Cell transplants and treatments that increase cAMP and neurotrophins stimulate motor and sensory axons to cross glial scars and to grow long distances in white matter. Genetic studies deleting all members of the Nogo family and even the Nogo receptor do not always improve regeneration in mice. A recent study reported that suppressing the phosphatase and tensin homolog (PTEN) gene promotes prolific corticospinal tract regeneration. These findings cannot be explained by the current theories proposing that Nogo and glial scars prevent regeneration. Spinal axons clearly can and will grow through glial scars and Nogo-expressing tissue under some circumstances. The observation that deleting PTEN allows corticospinal tract regeneration indicates that the PTEN/AKT/mTOR pathway regulates axonal growth. Finally, many other factors stimulate spinal axonal growth, including conditioning lesions, cAMP, glycogen synthetase kinase inhibition, and neurotrophins. To explain these disparate regenerative phenomena, I propose that the spinal cord has evolved regenerative mechanisms that are normally suppressed by multiple extrinsic and intrinsic factors but can be activated by injury, mediated by the PTEN/AKT/mTOR, cAMP, and GSK3b pathways, to stimulate neural growth and proliferation.

Short- and long-term consequences of perinatal asphyxia: looking for neuroprotective strategies

Perinatal asphyxia constitutes a prototype of obstetric complications occurring when pulmonary oxygenation is delayed or interrupted. A primary insult is first produced by the length of the time without oxygenation, leading to hypoxia/ischemia and death if oxygenation is not promptly established. A second insult is produced by re-oxygenation, eliciting a cascade of biochemical events for restoring function, implying, however, improper homeostasis. The effects observed long after perinatal asphyxia can be explained by over-expression of sentinel proteins, such as poly(ADP-ribose) polymerase-1 (PARP-1), competing for oxidised nicotinamide adenine dinucleotide (NAD(+)) during re-oxygenation. Asphyxia also induces transcriptional activation of pro-inflammatory factors, including nuclear factor κB (NFκB) and its subunit p65, whose translocation to the nucleus is significantly increased in brain tissue from asphyxia-exposed animals, in tandem with PARP-1 overactivation, leading to the idea that sentinel protein inhibition constitutes a suitable therapeutic strategy. It is proposed that PARP-1 inhibition also down-regulates the expression of pro-inflammatory cytokines.Nicotinamide is a suitable PARP-1 inhibitor, whose effects have been studied in an experimental model of global perinatal asphyxia in rats, inducing the insult by immersing rat foetuses into a water bath for various periods of time. Following asphyxia, the pups are delivered, immediately treated, or given to surrogate dams for nursing, pending further experiments. Systemic administration of nicotinamide 1 h after the insult inhibited PARP-1 overactivity in peripheral and brain tissue, preventing several of the long-term consequences elicited by perinatal asphyxia, supporting the idea that it constitutes a lead for exploring compounds with similar or better pharmacological profiles.

HMG-CoA Reductase Inhibition Promotes Neurological Recovery, Peri-Lesional Tissue Remodeling, and Contralesional Pyramidal Tract Plasticity after Focal Cerebral Ischemia

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors are widely used for secondary stroke prevention. Besides their lipid-lowering activity, pleiotropic effects on neuronal survival, angiogenesis, and neurogenesis have been described. In view of these observations, we were interested whether HMG-CoA reductase inhibition in the post-acute stroke phase promotes neurological recovery, peri-lesional, and contralesional neuronal plasticity. We examined effects of the HMG-CoA reductase inhibitor rosuvastatin (0.2 or 2.0 mg/kg/day i.c.v.), administered starting 3 days after 30 min of middle cerebral artery occlusion for 30 days. Here, we show that rosuvastatin treatment significantly increased the grip strength and motor coordination of animals, promoted exploration behavior, and reduced anxiety. It was associated with structural remodeling of peri-lesional brain tissue, reflected by increased neuronal survival, enhanced capillary density, and reduced striatal and corpus callosum atrophy. Increased sprouting of contralesional pyramidal tract fibers crossing the midline in order to innervate the ipsilesional red nucleus was noticed in rosuvastatin compared with vehicle-treated mice, as shown by anterograde tract tracing experiments. Western blot analysis revealed that the abundance of HMG-CoA reductase was increased in the contralesional hemisphere at 14 and 28 days post-ischemia. Our data support the idea that HMG-CoA reductase inhibition promotes brain remodeling and plasticity far beyond the acute stroke phase, resulting in neurological recovery.

Axon growth inhibition by RhoA/ROCK in the central nervous system

Rho kinase (ROCK) is a serine/threonine kinase and a downstream target of the small GTPase Rho. The RhoA/ROCK pathway is associated with various neuronal functions such as migration, dendrite development, and axonal extension. Evidence from animal studies reveals that RhoA/ROCK signaling is involved in various central nervous system (CNS) diseases, including optic nerve and spinal cord injuries, stroke, and neurodegenerative diseases. Given that RhoA/ROCK plays a critical role in the pathophysiology of CNS diseases, the development of therapeutic agents targeting this pathway is expected to contribute to the treatment of CNS diseases. The RhoA/ROCK pathway mediates the effects of myelin-associated axon growth inhibitors—Nogo, myelin-associated glycoprotein (MAG), oligodendrocyte-myelin glycoprotein (OMgp), and repulsive guidance molecule (RGM). Blocking RhoA/ROCK signaling can reverse the inhibitory effects of these molecules on axon outgrowth, and promotes axonal sprouting and functional recovery in animal models of CNS injury. To date, several RhoA/ROCK inhibitors have been under development or in clinical trials as therapeutic agents for neurological disorders. In this review, we focus on the RhoA/ROCK signaling pathway in neurological disorders. We also discuss the potential therapeutic approaches of RhoA/ROCK inhibitors for various neurological disorders.

Human NgR-Fc decoy protein via lumbar intrathecal bolus administration enhances recovery from rat spinal cord contusion

Axonal growth and neurological recovery after traumatic spinal cord injury (SCI) is limited by the presence of inhibitory proteins in myelin, several of which act via the NgR1 protein in neurons. A truncated soluble ligand-binding fragment of NgR1 serves as a decoy and promotes recovery in acute and chronic rodent SCI models. To develop the translational potential of these observations, we created a human sequence-derived NgR1(310)-Fc protein. This protein is active in vitro. When the human NgR1 decoy is administered by continuous intracerebroventricular infusion to rats with a spinal contusion injury at doses of 0.09-0.53 mg/kg/d, neurological recovery is improved. Effective doses double the percentage of rats able to bear weight on their hindlimbs. Next, we considered the half-life and distribution of NgR1(310)-Fc after bolus delivery to the lumbar intrathecal space. The protein is found throughout the neuraxis and has a tissue half-life of approximately 2 days in the rat, and 5 days in the nonhuman primate. At an intermittent, once every 4 day, lumbar bolus dosing schedule of 0.14 mg/kg/d, NgR1(310)-Fc promoted locomotor rat recovery from spinal cord contusion at least as effectively as continuous infusion in open field and grid walking tasks. Moreover, the intermittent lumbar NgR1(310)-Fc treatment increased the growth of raphespinal axons into the lumbar spinal cord after injury. Thus, human NgR1(310)-Fc provides effective treatment for recovery from traumatic SCI in this preclinical model with a simplified administration regimen that facilitates clinical testing.

Baclofen facilitates sleep, neuroplasticity, and recovery after stroke in rats

OBJECTIVE

Sleep disruption in the acute phase after stroke has detrimental effects on recovery in both humans and animals. Conversely, the effect of sleep promotion remains unclear. Baclofen (Bac) is a known non-rapid eye movement (NREM) sleep-promoting drug in both humans and animals. The aim of this study was to investigate the effect of Bac on stroke recovery in a rat model of focal cerebral ischemia (isch).

METHODS

Rats, assigned to three experimental groups (Bac/isch, saline/isch, or Bac/sham), were injected twice daily for 10 consecutive days with Bac or saline, starting 24 h after induction of stroke. The sleep-wake cycle was assessed by EEG recordings and functional motor recovery by single pellet reaching test (SPR). In order to identify potential neuroplasticity mechanisms, axonal sprouting and neurogenesis were evaluated. Brain damage was assessed by Nissl staining.

RESULTS

Repeated Bac treatment after ischemia affected sleep, motor function, and neuroplasticity, but not the size of brain damage. NREM sleep amount was increased significantly during the dark phase in Bac/isch compared to the saline/isch group. SPR performance dropped to 0 immediately after stroke and was recovered slowly thereafter in both ischemic groups. However, Bac-treated ischemic rats performed significantly better than saline-treated animals. Axonal sprouting in the ipsilesional motor cortex and striatum, and neurogenesis in the peri-infarct region were significantly increased in Bac/isch group.

CONCLUSION

Delayed repeated Bac treatment after stroke increased NREM sleep and promoted both neuroplasticity and functional outcome. These data support the hypothesis of the role of sleep as a modulator of poststroke recovery.