Novel Stroke Therapeutics: Unraveling Stroke Pathophysiology and Its Impact on Clinical Treatments

Cortical Reshaping and Functional Recovery Induced by Silk Fibroin Hydrogels-Encapsulated Stem Cells Implanted in Stroke Animals

The restitution of damaged circuitry and functional remodeling of peri-injured areas constitute two main mechanisms for sustaining recovery of the brain after stroke. In this study, a silk fibroin-based biomaterial efficiently supports the survival of intracerebrally implanted mesenchymal stem cells (mSCs) and increases functional outcomes over time in a model of cortical stroke that affects the forepaw sensory and motor representations. We show that the functional mechanisms underlying recovery are related to a substantial preservation of cortical tissue in the first days after mSCs-polymer implantation, followed by delayed cortical plasticity that involved a progressive functional disconnection between the forepaw sensory (FLs₁) and caudal motor (cFLm₁) representations and an emergent sensory activity in peri-lesional areas belonging to cFLm₁. Our results provide evidence that mSCs integrated into silk fibroin hydrogels attenuate the cerebral damage after brain infarction inducing a delayed cortical plasticity in the peri-lesional tissue, this later a functional change described during spontaneous or training rehabilitation-induced recovery. This study shows that brain remapping and sustained recovery were experimentally favored using a stem cell-biomaterial-based approach.

RNA-Sequencing Analysis Revealed a Distinct Motor Cortex Transcriptome in Spontaneously Recovered Mice After Stroke

Background and Purpose- Many restorative therapies have been used to study brain repair after stroke. These therapeutic-induced changes have revealed important insights on brain repair and recovery mechanisms; however, the intrinsic changes that occur in spontaneously recovery after stroke is less clear. The goal of this study is to elucidate the intrinsic changes in spontaneous recovery after stroke, by directly investigating the transcriptome of primary motor cortex in mice that naturally recovered after stroke. Methods- Male C57BL/6J mice were subjected to transient middle cerebral artery occlusion. Functional recovery was evaluated using the horizontal rotating beam test. A novel in-depth lesion mapping analysis was used to evaluate infarct size and locations. Ipsilesional and contralesional primary motor cortices (iM1 and cM1) were processed for RNA-sequencing transcriptome analysis. Results- Cluster analysis of the stroke mice behavior performance revealed 2 distinct recovery groups: a spontaneously recovered and a nonrecovered group. Both groups showed similar lesion profile, despite their differential recovery outcome. RNA-sequencing transcriptome analysis revealed distinct biological pathways in the spontaneously recovered stroke mice, in both iM1 and cM1. Correlation analysis revealed that 38 genes in the iM1 were significantly correlated with improved recovery, whereas 74 genes were correlated in the cM1. In particular, ingenuity pathway analysis highlighted the involvement of cAMP signaling in the cM1, with selective reduction of Adora2a (adenosine receptor A2A), Drd2 (dopamine receptor D2), and Pde10a (phosphodiesterase 10A) expression in recovered mice. Interestingly, the expressions of these genes in cM1 were negatively correlated with behavioral recovery. Conclusions- Our RNA-sequencing data revealed a panel of recovery-related genes in the motor cortex of spontaneously recovered stroke mice and highlighted the involvement of contralesional cortex in spontaneous recovery, particularly Adora2a, Drd2, and Pde10a-mediated cAMP signaling pathway. Developing drugs targeting these candidates after stroke may provide beneficial recovery outcome.

2-Methyl-5H-benzo[d]pyrazolo[5,1-b][1,3]oxazin-5-imine, an edaravone analog, exerts neuroprotective effects against acute ischemic injury via inhibiting oxidative stress

Oxidative stress plays an indispensable role in the pathogenesis of cerebral ischemia. Inhibiting oxidative stress has been considered as an effective approach for stroke treatment. Edaravone, a free radical scavenger, has been shown to prevent cerebral ischemic injury. However, the clinical efficacy of edaravone is limited because it has a low scavenging activity for superoxide anions (O₂^·-). Here, we report that 2-methyl-5H-benzo[d]pyrazolo[5,1-b][1,3]oxazin-5-imine, a novel small-molecule compound structurally related to edaravone, showed a stronger inhibitory effect on oxidative stress in vitro. In vivo, 2-methyl-5H-benzo[d]pyrazolo[5,1-b][1,3]oxazin-5-imine reversed transient middle cerebral artery occlusion-induced dysfunctions of superoxide dismutases and malondialdehyde, two proteins crucial for oxidative stress, suggesting a strengthened antioxidant system. Moreover, 2-methyl-5H-benzo[d]pyrazolo[5,1-b][1,3]oxazin-5-imine decreased blood brain barrier permeability. Then, we found that 2-methyl-5H-benzo[d]pyrazolo[5,1-b][1,3]oxazin-5-imine had a stronger neuroprotective effect than edaravone. More importantly, 2-methyl-5H-benzo[d]pyrazolo[5,1-b][1,3]oxazin-5-imine decreased not only infarct size and neurological deficits in the acute phase but also modified neurological severity score and escape latency in Morris water maze task in the delayed period, indicating enhanced neuroprotection, sensorimotor function and spatial memory. Together, these findings suggest that 2-methyl-5H-benzo[d]pyrazolo[5,1-b][1,3]oxazin-5-imine could be a preferable option for stroke treatment.

Activated protein C, protease activated receptor 1, and neuroprotection

Protein C is a plasma serine protease zymogen whose active form, activated protein C (APC), exerts potent anticoagulant activity. In addition to its antithrombotic role as a plasma protease, pharmacologic APC is a pleiotropic protease that activates diverse homeostatic cell signaling pathways via multiple receptors on many cells. Engineering of APC by site-directed mutagenesis provided a signaling selective APC mutant with 3 Lys residues replaced by 3 Ala residues, 3K3A-APC, that lacks >90% anticoagulant activity but retains normal cell signaling activities. This 3K3A-APC mutant exerts multiple potent neuroprotective activities, which require the G-protein-coupled receptor, protease activated receptor 1. Potent neuroprotection in murine ischemic stroke models is linked to 3K3A-APC-induced signaling that arises due to APC's cleavage in protease activated receptor 1 at a noncanonical Arg46 site. This cleavage causes biased signaling that provides a major explanation for APC's in vivo mechanism of action for neuroprotective activities. 3K3A-APC appeared to be safe in ischemic stroke patients and reduced bleeding in the brain after tissue plasminogen activator therapy in a recent phase 2 clinical trial. Hence, it merits further clinical testing for its efficacy in ischemic stroke patients. Recent studies using human fetal neural stem and progenitor cells show that 3K3A-APC promotes neurogenesis in vitro as well as in vivo in the murine middle cerebral artery occlusion stroke model. These recent advances should encourage translational research centered on signaling selective APC's for both single-agent therapies and multiagent combination therapies for ischemic stroke and other neuropathologies.

Recent Advances in the Therapeutic and Diagnostic Use of Liposomes and Carbon Nanomaterials in Ischemic Stroke

The complexity of the central nervous system (CNS), its limited self-repairing capacity and the ineffective delivery of most CNS drugs to the brain contribute to the irreversible and progressive nature of many neurological diseases and also the severity of the outcome. Therefore, neurological disorders belong to the group of pathologies with the greatest need of new technologies for diagnostics and therapeutics. In this scenario, nanotechnology has emerged with innovative and promising biomaterials and tools. This review focuses on ischemic stroke, being one of the major causes of death and serious long-term disabilities worldwide, and the recent advances in the study of liposomes and carbon nanomaterials for therapeutic and diagnostic purposes. Ischemic stroke occurs when blood flow to the brain is insufficient to meet metabolic demand, leading to a cascade of physiopathological events in the CNS including local blood brain barrier (BBB) disruption. However, to date, the only treatment approved by the FDA for this pathology is based on the potentially toxic tissue plasminogen activator. The techniques currently available for diagnosis of stroke also lack sensitivity. Liposomes and carbon nanomaterials were selected for comparison in this review, because of their very distinct characteristics and ranges of applications. Liposomes represent a biomimetic system, with composition, structural organization and properties very similar to biological membranes. On the other hand, carbon nanomaterials, which are not naturally encountered in the human body, exhibit new modes of interaction with biological molecules and systems, resulting in unique pharmacological properties. In the last years, several neuroprotective agents have been evaluated under the encapsulated form in liposomes, in experimental models of stroke. Effective drug delivery to the brain and neuroprotection were achieved using stealth liposomes bearing targeting ligands onto their surface for brain endothelial cells and ischemic tissues receptors. Carbon nanomaterials including nanotubes, fullerenes and graphene, started to be investigated and potential applications for therapy, biosensing and imaging have been identified based on their antioxidant action, their intrinsic photoluminescence, their ability to cross the BBB, transitorily decrease the BBB paracellular tightness, carry oligonucleotides and cells and induce cell differentiation. The potential future developments in the field are finally discussed.

Engineered stem cell mimics to enhance stroke recovery

Currently, no medical therapies exist to augment stroke recovery. Stem cells are an intriguing treatment option being evaluated, but cell-based therapies have several challenges including developing a stable cell product with long term reproducibility. Since much of the improvement observed from cellular therapeutics is believed to result from trophic factors the stem cells release over time, biomaterials are well-positioned to deliver these important molecules in a similar fashion. Here we show that essential trophic factors secreted from stem cells can be effectively released from a multi-component hydrogel system into the post-stroke environment. Using our polymeric system to deliver VEGF-A and MMP-9, we improved recovery after stroke to an equivalent degree as observed with traditional stem cell treatment in a rodent model. While VEGF-A and MMP-9 have many unique mechanisms of action, connective tissue growth factor (CTGF) interacts with both VEGF-A and MMP-9. With our hydrogel system as well as with stem cell delivery, the CTGF pathway is shown to be downregulated with improved stroke recovery.

Neural stem cell therapies and hypoxic-ischemic brain injury

Hypoxic-ischemic brain injury is a significant cause of morbidity and mortality in the adult as well as in the neonate. Extensive pre-clinical studies have shown promising therapeutic effects of neural stem cell-based treatments for hypoxic-ischemic brain injury. There are two major strategies of neural stem cell-based therapies: transplanting exogenous neural stem cells and boosting self-repair of endogenous neural stem cells. Neural stem cell transplantation has been proved to improve functional recovery after brain injury through multiple by-stander mechanisms (e.g., neuroprotection, immunomodulation), rather than simple cell-replacement. Endogenous neural stem cells reside in certain neurogenic niches of the brain and response to brain injury. Many molecules (e.g., neurotrophic factors) can stimulate or enhance proliferation and differentiation of endogenous neural stem cells after injury. In this review, we first present an overview of neural stem cells during normal brain development and the effect of hypoxic-ischemic injury on the activation and function of endogenous neural stem cells in the brain. We then summarize and discuss the current knowledge of strategies and mechanisms for neural stem cell-based therapies on brain hypoxic-ischemic injury, including neonatal hypoxic-ischemic brain injury and adult ischemic stroke.

Allogeneic Umbilical Cord Blood Infusion for Adults with Ischemic Stroke: Clinical Outcomes from a Phase I Safety Study

Stroke is a major cause of death and long‐term disability, affecting one in six people worldwide. The only currently available approved pharmacological treatment for ischemic stroke is tissue plasminogen activator; however, relatively few patients are eligible for this therapy. We hypothesized that intravenous (IV) infusion of banked unrelated allogeneic umbilical cord blood (UCB) would improve functional outcomes in patients with ischemic stroke. To investigate this, we conducted a phase I open‐label trial to assess the safety and feasibility of a single IV infusion of non‐human leukocyte antigen (HLA) matched, ABO matched, unrelated allogeneic UCB into adult stroke patients. Ten participants with acute middle cerebral artery ischemic stroke were enrolled. UCB units were matched for blood group antigens and race but not HLA, and infused 3–9 days post‐stroke. The adverse event (AE) profile over a 12 month postinfusion period indicated that the treatment was well‐tolerated in these stroke patients, with no serious AEs directly related to the study product. Study participants were also assessed using neurological and functional evaluations, including the modified Rankin Score (mRS) and National Institute of Health Stroke Scale (NIHSS). At 3 months post‐treatment, all participants had improved by at least one grade in mRS (mean 2.8 ± 0.9) and by at least 4 points in NIHSS (mean 5.9 ± 1.4), relative to baseline. Together, these data suggest that a single i.v. dose of allogeneic non‐HLA matched human UCB cells is safe in adults with ischemic stroke, and support the conduct of a randomized, placebo‐controlled phase 2 study. stemcellstranslationalmedicine2018;7:521–529

The application of nanoparticles for neuroprotection in acute ischemic stroke

Stroke still represents one of the most common causes of death and disability worldwide. Acute ischemic stroke (AIS), caused by brain arterial occlusion resulting from a thrombus or embolus, is the most common form of stroke. However, current therapies in AIS are inadequate, and the only US FDA approved treatment is the thrombolytic drug Alteplase. Therefore, establishing effective therapeutic strategies for AIS is urgently needed. Using nanoparticle-based technologies to deliver neuroprotective agents to the ischemic area has attracted increasing attention of late. In this review, the important molecular pathological mechanisms in cerebral ischemia are briefly summarized, the potential of nanoparticulate drug-delivery systems for AIS intervention and recovery are introduced and problems in the medical application of nanoparticles will also be discussed.

Up-regulation of miR-122 protects against neuronal cell death in ischemic stroke through the heat shock protein 70-dependent NF-κB pathway by targeting FOXO3

Dysfunction of the microRNA (miRNA) network has been emerging as a main regulator in ischemic stroke. Recently, studies have linked the deregulation of miR-122 to ischemic stroke. However, the specific role and molecular mechanism of miR-122 in ischemic stroke remain to be further investigated. Here, we found that miR-122 was decreased in mouse N2A neuroblastoma (N2A) cells after oxygen-glucose deprivation (OGD) and mouse brain after transient middle cerebral artery occlusion (MCAO). OGD treatment significantly increased N2A cell death and Caspase-3 activity, and decreased Bcl-2 protein expression. In addition, MCAO treatment induced severe mouse brain infarction, mitochondrial reactive oxygen species (ROS) production, and long-term neurological deficit. Gain-of-miR-122 function significantly suppressed OGD- and MCAO-induced injures in vitro and in vivo. Subsequently, miR-122 was validated to directly bind to the predicted 3'-untranslated region (3'-UTR) of FOXO3 gene, and the inhibitory effects of miR-122 on ischemic injury in vitro and in vivo were overturned by FOXO3 overexpression. Moreover, our results further revealed that miR-122-FOXO3 axis functioned via the heat shock protein 70 (HSP-70)-mediated NF-κB pathway. Collectively, our data suggest that miR-122 inhibits ischemic neuronal death through the HSP-70-dependent NF-κB pathway by targeting FOXO3. These findings raise the possibility that this regulatory net may contribute to the pathogenesis of the ischemic brain injury in stroke.

Exosomes in Acquired Neurological Disorders: New Insights into Pathophysiology and Treatment

Exosomes are endogenous nanovesicles that play critical roles in intercellular signaling by conveying functional genetic information and proteins between cells. Exosomes readily cross the blood-brain barrier and have promise as therapeutic delivery vehicles that have the potential to specifically deliver molecules to the central nervous system (CNS). This unique feature also makes exosomes attractive as biomarkers in diagnostics, prognostics, and therapeutics in the context of multiple significant public health conditions, including acquired neurological disorders. The purpose of this review is to summarize the state of the science surrounding the relevance of extracellular vesicles (EVs), particularly exosomes, to acquire neurological disorders, specifically traumatic brain injury (TBI), spinal cord injury (SCI), and ischemic stroke. In total, ten research articles were identified that examined exosomes in the context of TBI, SCI, or stroke; these manuscripts were reviewed and synthesized to further understand the current role of exosomes in the context of acquired neurological disorders. Of the ten published studies, four focused exclusively on TBI, one on both TBI and SCI, and five on ischemic stroke; notably, eight of the ten studies were limited to pre-clinical samples. The present review is the first to discuss the current body of knowledge surrounding the role of exosomes in the pathophysiology, diagnosis, and prognosis, as well as promising therapeutic strategies in TBI, SCI, and stroke research.

Electrically Conductive Scaffold to Modulate and Deliver Stem Cells

Stem cell therapy has emerged as an exciting stroke therapeutic, but the optimal delivery method remains unclear. While the technique of microinjection has been used for decades to deliver stem cells in stroke models, this technique is limited by the lack of ability to manipulate the stem cells prior to injection. This paper details a method of using an electrically conductive polymer scaffold for stem cell delivery. Electrical stimulation of stem cells using a conductive polymer scaffold alters the stem cell's genes involved in cell survival, inflammatory response, and synaptic remodeling. After electrical preconditioning, the stem cells on the scaffold are transplanted intracranially in a distal middle cerebral artery occlusion rat model. This protocol describes a powerful technique to manipulate stem cells via a conductive polymer scaffold and creates a new tool to further develop stem cell-based therapy.

The NAD+-Dependent Family of Sirtuins in Cerebral Ischemia and Preconditioning

SIGNIFICANCE

Sirtuins are an evolutionarily conserved family of NAD+-dependent lysine deacylases and ADP ribosylases. Their requirement for NAD+ as a cosubstrate allows them to act as metabolic sensors that couple changes in the energy status of the cell to changes in cellular physiological processes. NAD+ levels are affected by several NAD+-producing and NAD+-consuming pathways as well as by cellular respiration. Thus their intracellular levels are highly dynamic and are misregulated in a spectrum of metabolic disorders including cerebral ischemia. This, in turn, compromises several NAD+-dependent processes that may ultimately lead to cell death. Recent Advances: A number of efforts have been made to replenish NAD+ in cerebral ischemic injuries as well as to understand the functions of one its important mediators, the sirtuin family of proteins through the use of pharmacological modulators or genetic manipulation approaches either before or after the insult. Critical Issues and Future Directions: The results of these studies have regarded the sirtuins as promising therapeutic targets for cerebral ischemia. Yet, additional efforts are needed to understand the role of some of the less characterized members and to address the sex-specific effects observed with some members. Sirtuins also exhibit cell-type-specific expression in the brain as well as distinct subcellular and regional localizations. As such, they are involved in diverse and sometimes opposing cellular processes that can either promote neuroprotection or further contribute to the injury; which also stresses the need for the development and use of sirtuin-specific pharmacological modulators. Antioxid. Redox Signal. 28, 691-710.

Cistanche deserticola polysaccharides protects PC12 cells against OGD/RP-induced injury

Ischemia stroke is a disease with high morbidity and mortality. Cistanche deserticola polysaccharides (CDP) possess a wide range of beneficial effects, including hepatoprotection and immune homeostasis. As far as we know, the protective effect of CDP on neurons injured by oxygen-glucose deprivation/reperfusion (OGD/RP) has not been investigated. In this study, OGD/RP injured a PC12 cell model. Briefly, CDP (0.05, 0.5 and 5??g/ml) was administered before reperfusion. The protective effect of CDP was then evaluated on the basis of cell viability, lactate dehydrogenase (LDH) leakage, [Ca²⁺]_i, mitochondrial membrane potential (MMP)and cell apoptosis, and redox status after reperfusion was evaluated by assaying reactive oxygen species (ROS), catalase (CAT), glutathione peroxidase (GSH-Px) and total antioxidant capacity. Basing on the fact that Parkinson's disease-associated protein DJ-1 participates in endogenous antioxidation and performs neuroprotective effects after ischemia stroke, we investigated the interaction between CDP and DJ-1. DJ-1 expression was detected through ELISA and Western blot analysis, and the translocation of DJ-1 was evaluated through immunofluorescence. Result showed that CDP (0.05, 0.5 and 5??g/ml) attenuated PC12 cell death, preserved MMP and calcium homeostasis; inhibited oxidative stress and decreased cell apoptosis. Moreover, CDP (5??g/ml) markedly stimulated DJ-1 secretion and expression. Overall, the results suggested that CDP exerts neuroprotective effect against OGD/RP-induced injury by inhibiting oxidative stress and regulating the DJ-1 pathway.

Neurons Generated by Mouse ESCs with Hippocampal or Cortical Identity Display Distinct Projection Patterns When Co-transplanted in the Adult Brain

The capability of generating neural precursor cells with distinct types of regional identity in vitro has recently opened new opportunities for cell replacement in animal models of neurodegenerative diseases. By manipulating Wnt and BMP signaling, we steered the differentiation of mouse embryonic stem cells (ESCs) toward isocortical or hippocampal molecular identity. These two types of cells showed different degrees of axonal outgrowth and targeted different regions when co-transplanted in healthy or lesioned isocortex or in hippocampus. In hippocampus, only precursor cells with hippocampal molecular identity were able to extend projections, contacting CA3. Conversely, isocortical-like cells were capable of extending long-range axonal projections only when transplanted in motor cortex, sending fibers toward both intra- and extra-cortical targets. Ischemic damage induced by photothrombosis greatly enhanced the capability of isocortical-like cells to extend far-reaching projections. Our results indicate that neural precursors generated by ESCs carry intrinsic signals specifying axonal extension in different environments.

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Wnt signaling induces hippocampal fate in neuralized mouse ESCs

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Transplanted cortical and hippocampal neurons target distinct regions in adult brain

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Photothrombotic lesion favors neurite elongation of cortical transplanted cells

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Cortical cell transplantation improves the motor performance after ischemic damage

Hydrogels-Assisted Cell Engraftment for Repairing the Stroke-Damaged Brain: Chimera or Reality

The use of advanced biomaterials as a structural and functional support for stem cells-based therapeutic implants has boosted the development of tissue engineering applications in multiple clinical fields. In relation to neurological disorders, we are still far from the clinical reality of restoring normal brain function in neurodegenerative diseases and cerebrovascular disorders. Hydrogel polymers show unique mechanical stiffness properties in the range of living soft tissues such as nervous tissue. Furthermore, the use of these polymers drastically enhances the engraftment of stem cells as well as their capacity to produce and deliver neuroprotective and neuroregenerative factors in the host tissue. Along this article, we review past and current trends in experimental and translational research to understand the opportunities, benefits, and types of tentative hydrogel-based applications for the treatment of cerebral disorders. Although the use of hydrogels for brain disorders has been restricted to the experimental area, the current level of knowledge anticipates an intense development of this field to reach clinics in forthcoming years.

Neuroprotective Effects of neuroEPO Using an In Vitro Model of Stroke

Erythropoietin (EPO) is a glycoprotein initially identified as a hormone synthesized and secreted by the kidney that regulates erythropoiesis. EPO, and a group of its derivatives, are being evaluated as possible neuroprotective agents in cerebral ischemia. The objective of this study, using an in vitro model, was to determine how neuroEPO—which is a variant of EPO with a low sialic acid content—protects neurons from the toxic action of glutamate. Primary neuronal cultures were obtained from the forebrains of Wistar rat embryos after 17 days of gestation. Excitotoxicity was induced after nine days of in vitro culture by treatment with a medium containing 100 µM glutamate for 15 min. After this time, a new medium containing 100 ng of neuroEPO/mL was added. Morphological cell change was assessed by phase-contrast microscopy. Oxidative stress was analysed by measuring antioxidant and oxidant activity. After 24 h, the treatment with 100 ng of neuroEPO/mL showed a significant (p < 0.01) decrease in mortality, compared to cells treated with glutamate alone. neuroEPO treatment decreased mortality and tended to reproduce the morphological characteristics of the control. The oxidative stress induced by glutamate is reduced after neuroEPO treatment. These results confirm that neuroEPO has a protective effect against neuronal damage induced by excitotoxicity, improving antioxidant activity in the neuron, and protecting it from oxidative stress.

Multi-targeting effects of a new synthetic molecule (JM-20) in experimental models of cerebral ischemia

Ischemic stroke is a major cause of death and disability worldwide. Thrombolysis by tissue plasminogen activator is the only pharmacological treatment approved for clinical practice, but has a narrow therapeutic window and poor efficacy when the cell death cascade is activated. Numerous drugs that are thought to protect neurons against injury have previously failed in human trials despite showing efficacy in experimental models of stroke. Herein, we reviewed the main pre-clinical results of the neuroprotective effects of JM-20, a new hybrid molecule, against brain ischemia. JM-20 appears to protect the brain from ischemic damage by interfering with several elements of the ischemic cascade: antiexcitotoxic, anticalcic, antioxidant, antiapoptotic, and anti-inflammatory. Its ability to protect not only neurons but also glial cells together with its ability to target and preserve mitochondrial function makes JM-20 a promising molecule that may be able to shield the whole neurovascular unit. The multimodal and multi-cell action of JM-20 may explain the high degree of protection observed in a rat model of brain ischemia, as assayed through histological (hematoxylin-eosin, and luxol fast blue staining), neurochemical (glutamate and aspartate levels in cerebrospinal fluid), mitochondrial functionality and behavioural (neurological scale) analysis at doses of 4 and 8mg/kg. Furthermore, the wide therapeutic window of JM-20 of 8h also suggests that this molecule could be of potential interest in situations where brain perfusion is compromised.

Attenuation of reactive gliosis in stroke-injured mouse brain does not affect neurogenesis from grafted human iPSC-derived neural progenitors

Induced pluripotent stem cells (iPSCs) or their progeny, derived from human somatic cells, can give rise to functional improvements after intracerebral transplantation in animal models of stroke. Previous studies have indicated that reactive gliosis, which is associated with stroke, inhibits neurogenesis from both endogenous and grafted neural stem/progenitor cells (NSPCs) of rodent origin. Here we have assessed whether reactive astrocytes affect the fate of human iPSC-derived NSPCs transplanted into stroke-injured brain. Mice with genetically attenuated reactive gliosis (deficient for GFAP and vimentin) were subjected to cortical stroke and cells were implanted adjacent to the ischemic lesion one week later. At 8 weeks after transplantation, immunohistochemical analysis showed that attenuated reactive gliosis did not affect neurogenesis or commitment towards glial lineage of the grafted NSPCs. Our findings, obtained in a human-to-mouse xenograft experiment, provide evidence that the reactive gliosis in stroke-injured brain does not affect the formation of new neurons from intracortically grafted human iPSC-derived NSPCs. However, for a potential clinical translation of these cells in stroke, it will be important to clarify whether the lack of effect of reactive gliosis on neurogenesis is observed also in a human-to-human experimental setting.

The Proliferation Capacity of Cultured Neural Stem Cells Promoted by CSF Collected from SAH Patients Correlates to Clinical Outcome

Neurogenesis from endogenous neural stem cells (NSCs) might contribute to functional recovery after stroke based on animal studies; however, the relationship between neurogenesis and post-stroke outcome has rarely been demonstrated in humans. We prospectively collected cerebrospinal fluid (CSF) from 36 patients with subarachnoid hemorrhage (SAH). The CSF was added to the culture medium of the rat NSCs to test the effects on proliferation (proliferation index [PI], percentage of Ki-67 immunoreactive cells). We correlated the PI with functional outcome based on the modified Rankin Scale at 3 months post-SAH. Treatment with the CSF samples collected from SAH patients showed a higher PI compared with those collected from patients with normal pressure hydrocephalus and untreated controls (20.3 ± 8.8 vs. 8.2 ± 5.1 and 7.8 ± 3.0, P < 0.001), indicating proliferation-promoting factors in CSF after SAH. The PI was positively correlated with SAH volume (p = 0.025). For patients with lower SAH volume, patients with favorable outcome had a higher PI than those with poor outcome (20.8 ± 6.9 vs. 14.6 ± 4.3, p = 0.047). Using multivariable logistic regression analysis, the PI was a positive determinant for favorable outcome (odds ratio, 1.17; 95% confidence interval, 1.00 to 1.36) that more proliferation-promoting factors in CSF was associated with better functional outcome in SAH patients.

Cell Death Mechanisms in Stroke and Novel Molecular and Cellular Treatment Options

As a result of ischemia or hemorrhage, blood supply to neurons is disrupted which subsequently promotes a cascade of pathophysiological responses resulting in cell loss. Many mechanisms are involved solely or in combination in this disorder including excitotoxicity, mitochondrial death pathways, and the release of free radicals, protein misfolding, apoptosis, necrosis, autophagy and inflammation. Besides neuronal cell loss, damage to and loss of astrocytes as well as injury to white matter contributes also to cerebral injury. The core problem in stroke is the loss of neuronal cells which makes recovery difficult or even not possible in the late states. Acute treatment options that can be applied for stroke are mainly targeting re-establishment of blood flow and hence, their use is limited due to the effective time window of thrombolytic agents. However, if the acute time window is exceeded, neuronal loss starts due to the activation of cell death pathways. This review will explore the most updated cellular death mechanisms leading to neuronal loss in stroke. Ischemic and hemorrhagic stroke as well as subarachnoid hemorrhage will be debated in the light of cell death mechanisms and possible novel molecular and cellular treatment options will be discussed.

Biomaterials Developments for Brain Tissue Engineering

The Central Nervous System (CNS) is a highly complex organ that works as the control centre of the body, managing vital and non-vital functions. Neuro-diseases can lead to the degeneration of neural tissue, breakage of the neuronal networks which can affect vital functions and originate cognitive deficits. The complexity of the neural networks, their components and the low regenerative capacity of the CNS are on the basis for the lack of recovery, having the need for therapies that can promote tissue repair and recovery. Most brain processes are mediated through molecules (e.g. cytokines, neurotransmitters) and cells response accordingly and to surrounding cues, either biological or physical, which offers molecule administration and/or cell transplantation a great potential for use in brain recovery. Biomaterials and in particular, of natural-origin are attractive candidates owed to their intrinsic biological cues and biocompatibility and degradability. Through the use of biomaterials, it is possible to protect the cells/molecules from body clearance, enzymatic degradation while maintaining the components in a place of interest. Moreover, by means of combining several components, it is possible to obtain a more targeted and controlled delivery, to image the biomaterial implantation and its degradation over time and tackling simultaneously occurring events (cell death and inflammation) in brain diseases. In this chapter, it is reviewed some brain-affecting diseases and the current developments on tissue engineering approaches for a functional recovery of the brain from those diseases.

Dexpramipexole improves bioenergetics and outcome in experimental stroke

BACKGROUND AND PURPOSE

Dexpramipexole, a drug recently tested in patients with amyotrophic lateral sclerosis (ALS,) is able to bind F1Fo ATP synthase and increase mitochondrial ATP production. Here, we have investigated its effects on experimental ischaemic brain injury.

EXPERIMENTAL APPROACH

The effects of dexpramipexole on bioenergetics, Ca2+ fluxes, electrophysiological functions and death were evaluated in primary neural cultures and hippocampal slices exposed to oxygen-glucose deprivation (OGD). Effects on infarct volumes and neurological functions were also evaluated in mice following proximal or distal middle cerebral artery occlusion (MCAo). Distribution of dexpramipexole within the ischaemic brain was evaluated by means of mass spectrometry imaging.

KEY RESULTS

Dexpramipexole increased mitochondrial ATP production in cultured neurons or glia and reduces energy failure, prevents intracellular Ca2+ overload and affords cytoprotection when cultures are exposed to OGD. This compound also counteracted ATP depletion, mitochondrial swelling, anoxic depolarization, loss of synaptic activity and neuronal death in hippocampal slices subjected to OGD. Post-ischaemic treatment with dexpramipexole, at doses consistent with those already used in ALS patients, reduced brain infarct size and ameliorated neuroscore in mice subjected to transient or permanent MCAo. Notably, the concentrations of dexpramipexole reached within the ischaemic penumbra equalled those found neuroprotective in vitro.

CONCLUSION AND IMPLICATIONS

Dexpramipexole, a compound able to increase mitochondrial F1Fo ATP-synthase activity reduced ischaemic brain injury. These findings, together with the excellent brain penetration and favourable safety profile in humans, make dexpramipexole a drug with realistic translational potential for the treatment of stroke.

LINKED ARTICLES

This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.

Neuroprotective effect of baicalin on focal cerebral ischemia in rats

Baicalin, a flavonoid compound from the root of the herb Scutellaria baicalensis Georgi, has been widely used to treat patients with inflammatory disease. The aim of this study was to assess the efficacy of baicalin in a rat model of focal cerebral ischemia. Adult male Sprague-Dawley rat models of cerebral artery occlusion were established and then randomly and equally divided into three groups: ischemia (cerebral ischemia and reperfusion), valproic acid (cerebral ischemia and reperfusion + three intraperitoneal injections of valproic acid; positive control), and baicalin (cerebral ischemia and reperfusion + intraperitoneal injection of baicalin for 21 days). Neurological deficits were assessed using the postural reflex test and forelimb placing test at 3, 7, 14, and 21 days after ischemia. Rat cerebral infarct volume was measured using 2,3,5-triphenyltetrazolium chloride (TTC) staining method. Pathological change of ischemic brain tissue was assessed using hematoxylin-eosin staining. In the baicalin group, rat neurological function was obviously improved, cerebral infarct volume was obviously reduced, and the pathological impairment of ischemic brain tissue was obviously alleviated compared to the ischemia group. Cerebral infarct volume was similar in the valproic acid and baicalin groups. These findings suggest that baicalin has a neuroprotective effect on cerebral ischemia.

Long non-coding RNA MEG3 functions as a competing endogenous RNA to regulate ischemic neuronal death by targeting miR-21/PDCD4 signaling pathway

Long non-coding RNA (lncRNA) maternally expressed gene 3 (MEG3) has been demonstrated as an important regulator in diverse human cancers. However, its function and regulatory mechanism in ischemic stroke remains largely unknown. Here, we report that MEG3 is physically associated with microRNA-21 (miR-21), while miR-21 is downregulated following ischemia in the ischemic core in vitro and in vivo, which is opposite to MEG3. Besides, overexpression of miR-21 protects oxygen–glucose deprivation and reoxygenation (OGD/R)-induced apoptotic cell death. Furthermore, MEG3 functions as a competing endogenous RNAs (ceRNAs) and competes with programmed cell death 4 (PDCD4) mRNA for directly binding to miR-21, which mediates ischemic neuronal death. Knockdown of MEG3 protects against ischemic damage and improves overall neurological functions in vivo. Thus, our data uncovers a novel mechanism of lncRNA MEG3 as a ceRNA by targeting miR-21/PDCD4 signaling pathway in regulating ischemic neuronal death, which may help develop new strategies for the therapeutic interventions in cerebral ischemic stroke.

Acute connexin43 temporal and spatial expression in response to ischemic stroke

Connexin43 (Cx43) gap junctions expressed in astrocytes can significantly impact neuronal survival in stroke. However, little is known regarding Cx43 spatial and temporal expression during the initial stages of brain ischemia. Using immunohistochemistry and Western blot analysis, we examined Cx43 spatial and temporal expression as a function of neuronal injury within the first 24 h after permanent middle cerebral artery occlusion (pMCAO). Western blot analysis showed a significant increase in Cx43 protein expression in the core ischemic area at 2 and 3 h after pMCAO. However, after 6 h of pMCAO Cx43 levels were significantly reduced. This reduction was due to cell death and concomitant Cx43 degradation in the expanding focal ischemic region, while the peri-infarct zone revealed intense Cx43 staining. The neuronal cell-death marker Fluoro-Jade C labeled injured neurons faintly at 1 h post-pMCAO with a time-dependent increase in both intensity and size of punctate staining. In addition, decreased microtubule-associated protein 2 (MAP2) immunoreactivity and thionin staining similarly indicated cell damage beginning at 1 h after pMCAO. Taken together, Cx43 expression is sensitive to neuronal injury and can be detected as early as 2 h post-pMCAO. These findings underscore Cx43 gap junction as a potential early target for therapeutic intervention in ischemic stroke.

Transplantation of feeder-free human induced pluripotent stem cell-derived cortical neuron progenitors in adult male Wistar rats with focal brain ischemia

The use of human induced pluripotent stem cells (hiPSCs) eliminates the ethical issues associated with fetal or embryonic materials, thus allowing progress in cell therapy research for ischemic stroke. Strict regulation of cell therapy development requires the xeno-free condition to eliminate clinical complications. Maintenance of hiPSCs with feeder-free condition presents a higher degree of spontaneous differentiation in comparison with conventional cultures. Therefore, feeder-free derivation might be not ideal for developing transplantable hiPSC derivatives. We developed the feeder-free condition for differentiation of cortical neurons from hiPSCs. Then, we evaluated the cells' characteristics upon transplantation into the sham and focal brain ischemia on adult male Wistar rats. Grafts in lesioned brains demonstrated polarized reactivity toward the ischemic border, indicated by directional preferences in axonal outgrowth and cellular migration, with no influence on graft survival. Following the transplantation, forelimb asymmetry was better restored compared with controls. Herein, we provide evidence to support the use of the xeno-free condition for the development of cell therapy for ischemic stroke.

Slower EEG alpha generation, synchronization and "flow"-possible biomarkers of cognitive impairment and neuropathology of minor stroke

Background

We investigated EEG rhythms, particularly alpha activity, and their relationship to post-stroke neuropathology and cognitive functions in the subacute and chronic stages of minor strokes.

Methods

We included 10 patients with right middle cerebral artery (MCA) ischemic strokes and 11 healthy controls. All the assessments of stroke patients were done both in the subacute and chronic stages. Neurological impairment was measured using the National Institute of Health Stroke Scale (NIHSS), whereas cognitive functions were assessed using the Montreal Cognitive Assessment (MoCA) and MoCA memory index (MoCA-MIS). The EEG was recorded using a 19 channel EEG system with standard EEG electrode placement. In particular, we analyzed the EEGs derived from the four lateral frontal (F3, F7, F4, F8), and corresponding lateral posterior (P3, P4, T5, T6) electrodes. Quantitative EEG analysis included: the group FFT spectra, the weighted average of alpha frequency (αAVG), the group probability density distributions of all conventional EEG frequency band relative amplitudes (EEG microstructure), the inter- and intra-hemispheric coherences, and the topographic distribution of alpha carrier frequency phase potentials (PPs). Statistical analysis was done using a Kruskal–Wallis ANOVA with a post-hoc Mann–Whitney U two-tailed test, and Spearman’s correlation.

Results

We demonstrated transient cognitive impairment alongside a slower alpha frequency (αAVG) in the subacute right MCA stroke patients vs. the controls. This slower alpha frequency showed no amplitude change, but was highly synchronized intra-hemispherically, overlying the ipsi-lesional hemisphere, and inter-hemispherically, overlying the frontal cortex. In addition, the disturbances in EEG alpha activity in subacute stroke patients were expressed as a decrease in alpha PPs over the frontal cortex and an altered “alpha flow”, indicating the sustained augmentation of inter-hemispheric interactions. Although the stroke induced slower alpha was a transient phenomenon, the increased alpha intra-hemispheric synchronization, overlying the ipsi-lesional hemisphere, the increased alpha F3–F4 inter-hemispheric synchronization, the delayed alpha waves, and the newly established inter-hemispheric “alpha flow” within the frontal cortex, remained as a permanent consequence of the minor stroke. This newly established frontal inter-hemispheric “alpha flow” represented a permanent consequence of the “hidden” stroke neuropathology, despite the fact that cognitive impairment has been returned to the control values. All the detected permanent changes at the EEG level with no cognitive impairment after a minor stroke could be a way for the brain to compensate for the lesion and restore the lost function.

Discussion

Our study indicates slower EEG alpha generation, synchronization and “flow” as potential biomarkers of cognitive impairment onset and/or compensatory post-stroke re-organizational processes.

Can adjunctive therapies augment the efficacy of endovascular thrombolysis? A potential role for activated protein C

In the management of acute ischemic stroke, vessel recanalization correlates with functional status, mortality, cost, and other outcome measures. Thrombolysis with intravenous tissue plasminogen activator has many limitations that restrict its applicability, but recent advances in the development of mechanical thrombectomy devices as well as improved systems of stroke care have resulted in greater likelihood of vessel revascularization. Nonetheless, there remains substantial discrepancy between rates of recanalization and rates of favorable outcome. The poor neurological recovery among some stroke patients despite successful recanalization confirms the need for adjuvant pharmacological therapy for neuroprotection and/or neurorestoration. Prior clinical trials of such drugs may have failed due to the inability of the agent to access the ischemic tissue beyond the occluded artery. A protocol that couples revascularization with concurrent delivery of a neuroprotectant drug offers the potential to enhance the benefit of thrombolysis. Analogs of activated protein C (APC) exert pleiotropic anti-inflammatory, anti-apoptotic, antithrombotic, cytoprotective, and neuroregenerative effects in ischemic stroke and thus appear to be promising candidates for this novel approach. A multicenter, prospective, double-blinded, dose-escalation Phase 2 randomized clinical trial has enrolled 110 patients to assess the safety, pharmacokinetics, and efficacy of human recombinant 3K3A-APC following endovascular thrombolysis. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

An Increase of Sigma-1 Receptor in the Penumbra Neuron after Acute Ischemic Stroke

BACKGROUND

Penumbra salvage from infarction by early reperfusion within the time window is the target of acute ischemic stroke therapies. Although the penumbral imaging is potently usable in clinic trial, additional work needs to be performed to advancing the field with better-defined, evaluated, and validated imaging measures.

METHODS

Mice were subjected to permanent stroke by right middle cerebral artery (MCA) occlusion. Multimodel magnetic resonance imaging (MRI) method was assessed to define the penumbra as that brain region in which the perfusion and diffusion-weighted MR images are mismatched (perfusion-weighted imaging [PWI]-diffusion-weighted imaging [DWI] mismatch). MRI measurements were performed at 1 hour after MCA occlusion (MCAO). Sigma-1 receptor expression was assessed by immunoblotting and immunostaining in PWI-DWI-defined penumbra and core compared with sham or contralateral slice. Penumbral sigma-1 receptor identified the correlation with the neuron, astrocyte, and microglia by immuno-colocalization.

RESULTS

Sigma-1 receptor was significantly upregulated in penumbra or peri-infarct compared with sham and core tissue at 1 hour and 24 hours after MCAO. There was a colocalization of sigma-1 receptor and neuron in penumbra at 1 hour after stroke. Sigma-1 receptor is specifically increased in ischemic penumbral neuron at 1 hour after MCAO.

CONCLUSIONS

Sigma-1 receptor may act as an endogenous marker of penumbra after acute ischemic stroke.

Methods of reactivation and reprogramming of neural stem cells for neural repair

Research on the biology of adult neural stem cells (NSCs) and induced NSCs (iNSCs), as well as NSC-based therapies for diseases in central nervous system (CNS) has started to generate the expectation that these cells may be used for treatments in CNS injuries or disorders. Recent technological progresses in both NSCs themselves and their derivatives have brought us closer to therapeutic applications. Adult neurogenesis presents in particular regions in mammal brain, known as neurogenic niches such as the dental gyrus (DG) in hippocampus and the subventricular zone (SVZ), within which adult NSCs usually stay for long periods out of the cell cycle, in G0. The reactivation of quiescent adult NSCs needs orchestrated interactions between the extrinsic stimulis from niches and the intrinsic factors involving transcription factors (TFs), signaling pathway, epigenetics, and metabolism to start an intracellular regulatory program, which promotes the quiescent NSCs exit G0 and reenter cell cycle. Extrinsic and intrinsic mechanisms that regulate adult NSCs are interconnected and feedback on one another. Since endogenous neurogenesis only happens in restricted regions and steadily fails with disease advances, interest has evolved to apply the iNSCs converted from somatic cells to treat CNS disorders, as is also promising and preferable. To overcome the limitation of viral-based reprogramming of iNSCs, bioactive small molecules (SM) have been explored to enhance the efficiency of iNSC reprogramming or even replace TFs, making the iNSCs more amenable to clinical application. Despite intense research efforts to translate the studies of adult and induced NSCs from the bench to bedside, vital troubles remain at several steps in these processes. In this review, we examine the present status, advancement, pitfalls, and potential of the two types of NSC technologies, focusing on each aspects of reactivation of quiescent adult NSC and reprogramming of iNSC from somatic cells, as well as on progresses in cell-based regenerative strategies for neural repair and criteria for successful therapeutic applications.

Safety and effectiveness of stem cell therapies in early-phase clinical trials in stroke: a systematic review and meta-analysis

Stem cells have demonstrated encouraging potential as reparative therapy for patients suffering from post-stroke disability. Reperfusion interventions in the acute phase of stroke have shown significant benefit but are limited by a narrow window of opportunity in which they are beneficial. Thereafter, rehabilitation is the only intervention available. The current review summarises the current evidence for use of stem cell therapies in stroke from early-phase clinical trials. The safety and feasibility of administering different types of stem cell therapies in stroke seem to be reasonably proven. However, the effectiveness needs still to be established through bigger clinical trials with more pragmatic clinical trial designs that address the challenges raised by the heterogeneous nature of stroke per se, as well those due to unique characteristics of stem cells as therapeutic agents.

Stroke triggers nigrostriatal plasticity and increases alcohol consumption in rats

Excessive alcohol consumption is a known risk factor for stroke, but the effect of stroke on alcohol intake is unknown. The dorsomedial striatum (DMS) and midbrain areas of the nigrostriatal circuit are critically associated to stroke and alcohol addiction. Here we sought to explore the influence of stroke on alcohol consumption and to uncover the underlying nigrostriatal mechanism. Rats were trained to consume alcohol using a two-bottle choice or operant self-administration procedure. Retrograde beads were infused into the DMS or midbrain to label specific neuronal types, and ischemic stroke was induced in the dorsolateral striatum (DLS). Slice electrophysiology was employed to measure excitability and synaptic transmission in DMS and midbrain neurons. We found that ischemic stroke-induced DLS infarction produced significant increases in alcohol preference, operant self-administration, and relapse. These increases were accompanied by enhanced excitability of DMS and midbrain neurons. In addition, glutamatergic inputs onto DMS D1-neurons was potentiated, whereas GABAergic inputs onto DMS-projecting midbrain dopaminergic neurons was suppressed. Importantly, systemic inhibition of dopamine D1 receptors attenuated the stroke-induced increase in operant alcohol self-administration. Our results suggest that the stroke-induced DLS infarction evoked abnormal plasticity in nigrostriatal dopaminergic neurons and DMS D1-neurons, contributing to increased post-stroke alcohol-seeking and relapse.

Synaptic inputs from stroke-injured brain to grafted human stem cell-derived neurons activated by sensory stimuli

Transplanted neurons derived from stem cells have been proposed to improve function in animal models of human disease by various mechanisms such as neuronal replacement. However, whether the grafted neurons receive functional synaptic inputs from the recipient's brain and integrate into host neural circuitry is unknown. Here we studied the synaptic inputs from the host brain to grafted cortical neurons derived from human induced pluripotent stem cells after transplantation into stroke-injured rat cerebral cortex. Using the rabies virus-based trans-synaptic tracing method and immunoelectron microscopy, we demonstrate that the grafted neurons receive direct synaptic inputs from neurons in different host brain areas located in a pattern similar to that of neurons projecting to the corresponding endogenous cortical neurons in the intact brain. Electrophysiological in vivo recordings from the cortical implants show that physiological sensory stimuli, i.e. cutaneous stimulation of nose and paw, can activate or inhibit spontaneous activity in grafted neurons, indicating that at least some of the afferent inputs are functional. In agreement, we find using patch-clamp recordings that a portion of grafted neurons respond to photostimulation of virally transfected, channelrhodopsin-2-expressing thalamo-cortical axons in acute brain slices. The present study demonstrates, for the first time, that the host brain regulates the activity of grafted neurons, providing strong evidence that transplanted human induced pluripotent stem cell-derived cortical neurons can become incorporated into injured cortical circuitry. Our findings support the idea that these neurons could contribute to functional recovery in stroke and other conditions causing neuronal loss in cerebral cortex.

Peroxynitrite formed during a transient episode of brain ischaemia increases endothelium-derived hyperpolarization-type dilations in thromboxane/prostaglandin receptor-stimulated rat cerebral arteries

AIM

Increased thromboxane A₂ and peroxynitrite are hallmarks of cerebral ischaemia/reperfusion (I/R). Stimulation of thromboxane/prostaglandin receptors (TP) attenuates endothelium-derived hyperpolarization (EDH). We investigated whether EDH-type middle cerebral artery (MCA) relaxations following TP stimulation are altered after I/R and the influence of peroxynitrite.

METHODS

Vascular function was determined by wire myography after TP stimulation with the thromboxane A₂ mimetic 9,11-dideoxy-9α, 11α -methano-epoxy prostaglandin F2α (U46619) in MCA of Sprague Dawley rats subjected to MCA occlusion (90 min)/reperfusion (24 h) or sham operation, and in non-operated (control) rats. Some rats were treated with saline or the peroxynitrite decomposition catalyst 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato iron (III) (20 mg kg^-1 ). Protein expression was evaluated in MCA and in human microvascular endothelial cells submitted to hypoxia (overnight)/reoxygenation (24 h) (H/R) using immunofluorescence and immunoblotting.

RESULTS

In U46619-pre-constricted MCA, EDH-type relaxation by the proteinase-activated receptor 2 agonist serine-leucine-isoleucine-glycine-arginine-leucine-NH₂ (SLIGRL) was greater in I/R than sham rats due to an increased contribution of small-conductance calcium-activated potassium channels (SK_Ca ), which was confirmed by the enlarged relaxation to the SK_Ca activator N-cyclohexyl-N-2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-4-pyrimidinamine. I/R and H/R induced endothelial protein tyrosine nitration and filamentous-actin disruption. In control MCA, either cytochalasin D or peroxynitrite disrupted endothelial filamentous-actin and augmented EDH-type relaxation. Furthermore, peroxynitrite decomposition during I/R prevented the increase in EDH-type responses.

CONCLUSION

Following TP stimulation in MCA, EDH-type relaxation to SLIGRL is greater after I/R due to endothelial filamentous-actin disruption by peroxynitrite, which prevents TP-induced block of SK_Ca input to EDH. These results reveal a novel mechanism whereby peroxynitrite could promote post-ischaemic brain injury.

Identification of IL-17A-derived neural cell type and dynamic changes of IL-17A in serum/CSF of mice with ischemic stroke

BACKGROUND

Interleukin (IL)-17A was reported to be involved in the development of post-ischemic stroke inflammatory response and functional recovery. However, the IL-17A dynamic changes in serum/cerebrospinal fluid (CSF) and its role in neuronal injury following ischemic stroke are unclear.

METHODS

In vivo ischemic stroke was induced by 1 h of middle cerebral artery occlusion (MCAO) and 6 h-7 d reperfusion (R) in mice, while in vitro stroke was induced by 1 h oxygen-glucose deprivation (OGD)/24 h reoxygenation (R) in cultured cortical neurons. Enzyme-linked immunosorbent assay (ELISA) and double-labeled immunofluorescence of IL-17A with neuron (NeuN), astrocyte (GFAP) and microglia (Iba-1)-specific markers were used to determine the IL-17A levels in serum/CSF and neural cell type.

RESULTS

The ELISA results showed that IL-17A significantly increased both in peri-infarct region (p < 0.001) and CSF (p < 0.05) following 1 h MCAO/R 12 h. The levels of IL-17A in serum increased at R 1 d (p < 0.05) and peaked at R 3 d (p < 0.001) after 1 h MCAO. Immunofluorescent staining demonstrated that IL-17A co-localized with GFAP in peri-infarct regions. In addition, recombinant rIL-17A could aggravate ischemic injuries at dose-dependent manner in 1 h OGD/R 24 h-treated neurons companying with the increase of IL-17A receptor il-17RA mRNA (p < 0.001) and IL-17R protein levels.

CONCLUSION

We firstly reported astrocytic IL-17A peaks in CSF within 12 h and in serum at 3 d reperfusion after ischemic stroke. IL-17A may exaggerate neuronal injuries through its receptor IL-17R at early stage of ischemic stroke.

Interleukin-1 primes human mesenchymal stem cells towards an anti-inflammatory and pro-trophic phenotype in vitro

Background

Inflammation is a key contributor to central nervous system (CNS) injury such as stroke, and is a major target for therapeutic intervention. Effective treatments for CNS injuries are limited and applicable to only a minority of patients. Stem cell-based therapies are increasingly considered for the treatment of CNS disease, because they can be used as in-situ regulators of inflammation, and improve tissue repair and recovery. One promising option is the use of bone marrow-derived mesenchymal stem cells (MSCs), which can secrete anti-inflammatory and trophic factors, can migrate towards inflamed and injured sites or can be implanted locally. Here we tested the hypothesis that pre-treatment with inflammatory cytokines can prime MSCs towards an anti-inflammatory and pro-trophic phenotype in vitro.

Methods

Human MSCs from three different donors were cultured in vitro and treated with inflammatory mediators as follows: interleukin (IL)-1α, IL-1β, tumour necrosis factor alpha (TNF-α) or interferon-γ. After 24 h of treatment, cell supernatants were analysed by ELISA for expression of granulocyte-colony stimulating factor (G-CSF), IL-10, brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), IL-1 receptor antagonist (IL-1Ra) and vascular endothelial growth factor (VEGF). To confirm the anti-inflammatory potential of MSCs, immortalised mouse microglial BV2 cells were treated with bacterial lipopolysaccharide (LPS) and exposed to conditioned media (CM) of naïve or IL-1-primed MSCs, and levels of secreted microglial-derived inflammatory mediators including TNF-α, IL-10, G-CSF and IL-6 were measured by ELISA.

Results

Unstimulated MSCs constitutively expressed anti-inflammatory cytokines and trophic factors (IL-10, VEGF, BDNF, G-CSF, NGF and IL-1Ra). MSCs primed with IL-1α or IL-1β showed increased secretion of G-CSF, which was blocked by IL-1Ra. Furthermore, LPS-treated BV2 cells secreted less inflammatory and apoptotic markers, and showed increased secretion of the anti-inflammatory IL-10 in response to treatment with CM of IL-1-primed MSCs compared with CM of unprimed MSCs.

Conclusions

Our results demonstrate that priming MSCs with IL-1 increases expression of trophic factor G-CSF through an IL-1 receptor type 1 (IL-1R1) mechanism, and induces a reduction in the secretion of inflammatory mediators in LPS-activated microglial cells. The results therefore support the potential use of preconditioning treatments of stem cells in future therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0531-4) contains supplementary material, which is available to authorized users.

The cerebral circulation and cerebrovascular disease III: Stroke

In this paper, our review series on cerebrovascular disease anatomy, physiology, and pathology ends with a thorough discussion of the most significant cerebrovascular pathology: stroke. This discussion proceeds through two layers of organization. First, stroke is divided up into its main etiologic categories (ischemic stroke/transient ischemic attack, hemorrhagic stroke, and ischemic to hemorrhagic transformation). Then, the epidemiological, pathophysiological, clinical, and therapeutic (employed currently as well as emerging) aspects of each etiology are explored; emphasis is placed upon the therapeutic aspects. Finally, once we have covered all aspects of each etiologic category, we end our review with a defense of the thesis that there is much hope for the future of stroke treatment to be derived from familiarity with the literature on emerging therapies.

Prospects of modeling poststroke epileptogenesis

This Review describes the current status of poststroke epilepsy (PSE) with an emphasis on poststroke epileptogenesis modeling for testing new therapeutic agents. Stroke is a leading cause of epilepsy in an aging population. Late-onset "epileptic" seizures have been reported in up to 30% cases after stroke. Nevertheless, the overall prevalence of PSE is 2-4%. Rodent models of stroke have contributed to our understanding of the relationship between seizures and the underlying ischemic damage to neurons. To understand whether acutely generated stroke events lead to a chronic phenotype more closely resembling PSE with recurrent seizures, a limited variety of approaches emerged in early 2000s. These limited methods of causing an occlusion in mice and rats show different infarct size and neurological deficits. The most often employed procedure for inducing focal ischemia is the middle cerebral artery occlusion. This mimics the pathophysiology seen in humans in terms of extent of damage to cortex and striatum. Photothrombosis and endothelin-1 models can similarly evoke episodes of ischemic stroke. These models are well suited to studying mechanisms and biomarkers of epileptogenesis or optimizing novel drug discoveries. However, modeling of PSE is tedious, is highly variable, and lacks validity; therefore, it is not widely implemented in epilepsy research. Moreover, the relevance of ischemic models to specific forms of human stroke remains unclear. Stroke modeling in young male rodents lacks clinical relevance to elderly populations and especially to women, likely as a result of sex differences. Nevertheless, because of the neuronal damage and epileptogenic insult that these models trigger, they are helpful tools in studying acquired epilepsy and prophylactic drug therapy. © 2016 Wiley Periodicals, Inc.

Neurorestoration after stroke

Recent advancements in stem cell biology and neuromodulation have ushered in a battery of new neurorestorative therapies for ischemic stroke. While the understanding of stroke pathophysiology has matured, the ability to restore patients' quality of life remains inadequate. New therapeutic approaches, including cell transplantation and neurostimulation, focus on reestablishing the circuits disrupted by ischemia through multidimensional mechanisms to improve neuroplasticity and remodeling. The authors provide a broad overview of stroke pathophysiology and existing therapies to highlight the scientific and clinical implications of neurorestorative therapies for stroke.

Reduced Synaptic Vesicle Recycling during Hypoxia in Cultured Cortical Neurons

Improvement of neuronal recovery in the ischemic penumbra, an area around the core of a brain infarct with some remaining perfusion, has a large potential for the development of therapy against acute ischemic stroke. However, mechanisms that lead to either recovery or secondary damage in the penumbra largely remain unclear. Recent studies in cultured networks of cortical neurons showed that failure of synaptic transmission (referred to as synaptic failure) is a critical factor in the penumbral area, but the mechanisms that lead to synaptic failure are still under investigation. Here we used a Styryl dye, FM1-43, to quantify endocytosis and exocytosis in cultures of rat cortical neurons under normoxic and hypoxic conditions. Hypoxia in cultured cortical networks rapidly depressed endocytosis and, to a lesser extent, exocytosis. These findings support electrophysiological findings that synaptic failure occurs quickly after the induction of hypoxia, and confirms that the failing processes are at least in part presynaptic.

Lack of collagen XV is protective after ischemic stroke in mice

Collagens are key structural components of basement membranes, providing a scaffold for other components or adhering cells. Collagens and collagen-derived active fragments contribute to biological activities such as cell growth, differentiation and migration. Here, we report that collagen XV knock-out (ColXV KO) mice are resistant to experimental ischemic stroke. Interestingly, the infarcts of ColXV KO mice were as small as those of wild-type (WT) mice thrombolysed with recombinant tissue plasminogen activator (rtPA), the actual treatment for ischemic stroke. Importantly, there were no differences in the architecture of cerebrovascular anatomy between WT and ColXV KO mice. We found a twofold increase of the most potent pro-angiogenic factor, type A vascular growth endothelial factor (VEGF-A) in the ipsilateral cortex of rtPA-treated ischemic WT mice compared with untreated ischemic and sham-operated counterparts. A similar increase of VEGF-A was also found in both rtPA and untreated ischemic ColXV KO mice compared with sham ColXV KO mice. Finally, we evidenced that the levels of ColXV were increased in the plasma of WT mice treated with rtPA compared with untreated ischemic counterparts. Altogether, this study indicates that the lack ColXV is protective after stroke and that the degradation of endothelial ColXV may contribute to the beneficial effect of rtPA after ischemic stroke. The neuroprotection observed in ColXV KO mice may be attributed to the increased VEGF-A production following stroke in the ischemic territory.

Soluble cpg15 from Astrocytes Ameliorates Neurite Outgrowth Recovery of Hippocampal Neurons after Mouse Cerebral Ischemia

The present study focuses on the function of cpg15, a neurotrophic factor, in ischemic neuronal recovery using transient global cerebral ischemic (TGI) mouse model and oxygen-glucose deprivation (OGD)-treated primary cultured cells. The results showed that expression of cpg15 proteins in astrocytes, predominantly the soluble form, was significantly increased in mouse hippocampus after TGI and in the cultured astrocytes after OGD. Addition of the medium from the cpg15-overexpressed astrocytic culture into the OGD-treated hippocampal neuronal cultures reduces the neuronal injury, whereas the recovery of neurite outgrowths of OGD-injured neurons was prevented when cpg15 in the OGD-treated astrocytes was knocked down, or the OGD-treated-astrocytic medium was immunoadsorbed by cpg15 antibody. Furthermore, lentivirus-delivered knockdown of cpg15 expression in mouse hippocampal astrocytes diminishes the dendritic branches and exacerbates injury of neurons in CA1 region after TGI. In addition, treatment with inhibitors of MEK1/2, PI3K, and TrkA decreases, whereas overexpression of p-CREB, but not dp-CREB, increases the expression of cpg15 in U118 or primary cultured astrocytes. Also, it is observed that the Flag-tagged soluble cpg15 from the astrocytes transfected with Flag-tagged cpg15-expressing plasmids adheres to the surface of neuronal bodies and the neurites. In conclusion, our results suggest that the soluble cpg15 from astrocytes induced by ischemia could ameliorate the recovery of the ischemic-injured hippocampal neurons via adhering to the surface of neurons. The upregulated expression of cpg15 in astrocytes may be activated via MAPK and PI3K signal pathways, and regulation of CREB phosphorylation.SIGNIFICANCE STATEMENT Neuronal plasticity plays a crucial role in the amelioration of neurological recovery of ischemic injured brain, which remains a challenge for clinic treatment of cerebral ischemia. cpg15 as a synaptic plasticity-related factor may participate in promoting the recovery process; however, the underlying mechanisms are still largely unknown. The objective of this study is to reveal the function and mechanism of neuronal-specific cpg15 expressed in astrocytes after ischemia induction, in promoting the recovery of injured neurons. Our findings provided new mechanistic insight into the neurological recovery, which might help develop novel therapeutic options for cerebral ischemia via astrocytic-targeting interference of gene expression.

Transplantation of reprogrammed neurons for improved recovery after stroke

Somatic cells such as fibroblasts, reprogrammed to induced pluripotent stem cells, can be used to generate neural stem/progenitor cells or neuroblasts for transplantation. In this review, we summarize recent studies demonstrating that when grafted intracerebrally in animal models of stroke, reprogrammed neurons improve function, probably by several different mechanisms, e.g., trophic actions, modulation of inflammation, promotion of angiogenesis, cellular and synaptic plasticity, and neuroprotection. In our own work, we have shown that human skin-derived reprogrammed neurons, fated to cortical progeny, integrate in stroke-injured neuronal network and form functional afferent synapses with host neurons, responding to peripheral sensory stimulation. However, whether neuronal replacement plays a role for the improvement of sensory, motor, and cognitive deficits after transplantation of reprogrammed neurons is still unclear. We conclude that further preclinical studies are needed to understand the therapeutic potential of grafted reprogrammed neurons and to define a road map for their clinical translation in stroke.