Increased proliferation of neural progenitor cells but reduced survival of newborn cells in the contralateral hippocampus after focal cerebral ischemia in 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.

Wirelessly Powered-Electrically Conductive Polymer System for Stem Cell Enhanced Stroke Recovery

Effective stroke recovery therapeutics remain limited. Stem cell therapies have yielded promising results, but the harsh ischemic environment of the post-stroke brain reduces their therapeutic potential. Previously, we developed a conductive polymer scaffold system that enabled stem cell delivery with simultaneous electrical modulation of the cells and surrounding neural environment. This wired polymer scaffold proved efficacious in optimizing ideal conditions for stem cell mediated motor improvements in a rodent model of stroke. To further enable preclinical studies and enhance translational potential, we identified a method to improve this system by eliminating its dependence upon a tethered power source. We have herein developed a wirelessly powered, electrically conductive polymer system that eases therapeutic application and enables full mobility. As a proof of concept, we demonstrate that the wirelessly powered scaffold is able to stimulate neural stem cells in vitro, as well as in vivo in a rodent model of stroke. This system modulates the stroke microenvironment and increases the production of endogenous stem cells. In summation, this novel, wirelessly powered conductive scaffold can serve as a mobile platform for a wide variety of therapeutics involving electrical stimulation.

Stem Cell Therapy for Acute/Subacute Ischemic Stroke with a Focus on Intraarterial Stem Cell Transplantation: From Basic Research to Clinical Trials

Stem cell therapy for ischemic stroke holds great promise for the treatment of neurological impairment and has moved from the laboratory into early clinical trials. The mechanism of action of stem cell therapy includes the bystander effect and cell replacement. The bystander effect plays an important role in the acute to subacute phase, and cell replacement plays an important role in the subacute to chronic phase. Intraarterial (IA) transplantation is less invasive than intraparenchymal transplantation and can provide more cells in the affected brain region than intravenous transplantation. However, transplanted cell migration was reported to be insufficient, and few transplanted cells were retained in the brain for an extended period. Therefore, the bystander effect was considered the main mechanism of action of IA stem cell transplantation. In most clinical trials, IA transplantation was performed during the acute and subacute phases. Although clinical trials of IA transplantation demonstrated safety, they did not demonstrate satisfactory efficacy in improving patient outcomes. To increase efficacy, increased migration of transplanted cells and production of long surviving and effective stem cells would be crucial. Given the lack of knowledge on this subject, we review and summarize the mechanisms of action of transplanted stem cells and recent advancements in preclinical and clinical studies to provide information and guidance for further advancement of acute/subacute phase IA stem cell transplantation therapy for ischemic stroke.

RNA-binding protein signaling in adult neurogenesis

The process of neurogenesis in the brain, including cell proliferation, differentiation, survival, and maturation, results in the formation of new functional neurons. During embryonic development, neurogenesis is crucial to produce neurons to establish the nervous system, but the process persists in certain brain regions during adulthood. In adult neurogenesis, the production of new neurons in the hippocampus is accomplished via the division of neural stem cells. Neurogenesis is regulated by multiple factors, including gene expression at a temporal scale and post-transcriptional modifications. RNA-binding Proteins (RBPs) are known as proteins that bind to either double- or single-stranded RNA in cells and form ribonucleoprotein complexes. The involvement of RBPs in neurogenesis is crucial for modulating gene expression changes and posttranscriptional processes. Since neurogenesis affects learning and memory, RBPs are closely associated with cognitive functions and emotions. However, the pathways of each RBP in adult neurogenesis remain elusive and not clear. In this review, we specifically summarize the involvement of several RBPs in adult neurogenesis, including CPEB3, FXR2, FMRP, HuR, HuD, Lin28, Msi1, Sam68, Stau1, Smaug2, and SOX2. To understand the role of these RBPs in neurogenesis, including cell proliferation, differentiation, survival, and maturation as well as posttranscriptional gene expression, we discussed the protein family, structure, expression, functional domain, and region of action. Therefore, this narrative review aims to provide a comprehensive overview of the RBPs, their function, and their role in the process of adult neurogenesis as well as to identify possible research directions on RBPs and neurogenesis.

Four Decades of Ischemic Penumbra and Its Implication for Ischemic Stroke

The ischemic penumbra defined four decades ago has been the main battleground of ischemic stroke. The evolving ischemic penumbra concept has been providing insight for the development of vascular and cellular approaches as well as diagnostic tools for the treatment of ischemic stroke. rt-PA thrombolytic therapy to prevent the transition of ischemic penumbra to core has been approved for acute ischemic stroke within 3 h and was later recommended to extend to 4.5 h after symptom onset. Mechanical thrombectomy was introduced for the treatment of acute ischemic stroke with a therapeutic window of up to 24 h after stroke onset. Multiple modalities brain imaging techniques have been developed that provide guidance to define ischemic penumbra for reperfusion therapy in clinical practice. Cellular and molecular dissection of ischemic penumbra has been providing targets for the development of neuroprotective therapy for ischemic stroke. However, the dynamic nature of ischemic penumbra implicates that infarct core eventually expands into penumbra over time without reperfusion, dictating relative short therapeutic windows and limiting the impact of current reperfusion intervention. Entering the 5^th decade since the introduction, ischemic penumbra remains the main focus of ischemic stroke research and clinical practice. In this review, we summarized the evolving ischemic penumbra concept and its implication in the development of vascular and cellular interventions as well as diagnostic tools for acute ischemic stroke. In addition, we discussed future perspectives on expansion of the campaign beyond ischemic penumbra to develop treatment for ischemic stroke.

Microglia-mediated phagocytosis of apoptotic nuclei is impaired in the adult murine hippocampus after stroke

Following stroke, neuronal death takes place both in the infarct region and in brain areas distal to the lesion site including the hippocampus. The hippocampus is critically involved in learning and memory processes and continuously generates new neurons. Dysregulation of adult neurogenesis may be associated with cognitive decline after a stroke lesion. In particular, proliferation of precursor cells and the formation of new neurons are increased after lesion. Within the first week, many new precursor cells die during development. How dying precursors are removed from the hippocampus and to what extent phagocytosis takes place after stroke is still not clear. Here, we evaluated the effect of a prefrontal stroke lesion on the phagocytic activity of microglia in the dentate gyrus (DG) of the hippocampus. Three-months-old C57BL/6J mice were injected once with the proliferation marker BrdU (250 mg/kg) 6 hr after a middle cerebral artery occlusion or sham surgery. The number of apoptotic cells and the phagocytic capacity of the microglia were evaluated by means of immunohistochemistry, confocal microscopy, and 3D-reconstructions. We found a transient but significant increase in the number of apoptotic cells in the DG early after stroke, associated with impaired removal by microglia. Interestingly, phagocytosis of newly generated precursor cells was not affected. Our study shows that a prefrontal stroke lesion affects phagocytosis of apoptotic cells in the DG, a region distal to the lesion core. Whether disturbed phagocytosis might contribute to inflammatory- and maladaptive processes including cognitive impairment following stroke needs to be further investigated.

The Extracellular Matrix Glycoprotein Tenascin C and Adult Neurogenesis

Tenascin C (TnC) is a glycoprotein highly expressed in the extracellular matrix (ECM) during development and in the adult central nervous system (CNS) in regions of active neurogenesis, where neuron development is a tightly regulated process orchestrated by extracellular matrix components. In addition, newborn cells also communicate with glial cells, astrocytes and microglia, indicating the importance of signal integration in adult neurogenesis. Although TnC has been recognized as an important molecule in the regulation of cell proliferation and migration, complete regulatory pathways still need to be elucidated. In this review we discuss the formation of new neurons in the adult hippocampus and the olfactory system with specific reference to TnC and its regulating functions in this process. Better understanding of the ECM signaling in the niche of the CNS will have significant implications for regenerative therapies.

Post-stroke Neurogenesis: Friend or Foe?

The substantial clinical burden and disability after stroke injury urges the need to explore therapeutic solutions. Recent compelling evidence supports that neurogenesis persists in the adult mammalian brain and is amenable to regulation in both physiological and pathological situations. Its ability to generate new neurons implies a potential to contribute to recovery after brain injury. However, post-stroke neurogenic response may have different functional consequences. On the one hand, the capacity of newborn neurons to replenish the damaged tissue may be limited. In addition, aberrant forms of neurogenesis have been identified in several insult settings. All these data suggest that adult neurogenesis is at a crossroads between the physiological and the pathological regulation of the neurological function in the injured central nervous system (CNS). Given the complexity of the CNS together with its interaction with the periphery, we ultimately lack in-depth understanding of the key cell types, cell-cell interactions, and molecular pathways involved in the neurogenic response after brain damage and their positive or otherwise deleterious impact. Here we will review the evidence on the stroke-induced neurogenic response and on its potential repercussions on functional outcome. First, we will briefly describe subventricular zone (SVZ) neurogenesis after stroke beside the main evidence supporting its positive role on functional restoration after stroke. Then, we will focus on hippocampal subgranular zone (SGZ) neurogenesis due to the relevance of hippocampus in cognitive functions; we will outline compelling evidence that supports that, after stroke, SGZ neurogenesis may adopt a maladaptive plasticity response further contributing to the development of post-stroke cognitive impairment and dementia. Finally, we will discuss the therapeutic potential of specific steps in the neurogenic cascade that might ameliorate brain malfunctioning and the development of post-stroke cognitive impairment in the chronic phase.

p53 upregulated mediator of apoptosis (Puma) deficiency increases survival of adult neural stem cells generated physiologically in the hippocampus, but does not protect stem cells generated in surplus after an excitotoxic lesion

OBJECTIVES

Neurogenesis occurs in the mammalian brain throughout adulthood and increases in response to metabolic, toxic or traumatic insults. To remove potentially superfluous or unwanted neural stem cells/neuronal progenitors, their rate of proliferation and differentiation is fine-tuned against their rate of apoptosis. Apoptosis requires the transcriptional and posttranslational activation of Bcl-2-homolgy domain 3 (BH3)-only proteins. Previously, we demonstrated that the BH3-only protein p53-upregulated mediator of apoptosis (Puma) controls the physiological rate of apoptosis of neural precursor cells in the adult mouse hippocampus. Puma's role in controlling a lesion-induced increase in neural stem cells is currently not known.

METHODS

We employed a model of local, N-methyl-D-asparte (NMDA)-induced excitotoxic injury to the CA1 hippocampal subfield and immunofluorescence labelling to produce increased neural stem cell proliferation/ neurogenesis in the dentate gyrus at two survival times following the excitotoxic lesion.

RESULTS

Deletion of puma failed to rescue any NMDA-induced increase in adult born cells as assessed by BrdU or Doublecortin labelling in the long-term. No difference in the proportion of BrdU/NeuN-positive cells comparing the different genotypes and treatments suggested that the phenotypic fate of the cells was preserved regardless of the genotype and the treatment.

CONCLUSIONS

While neurogenesis is up-regulated in puma-deficient animals following NMDA-induced excitotoxicity to the hippocampal CA1 subfield, puma deficiency could not protect this surplus of newly generated cells from apoptotic cell death.

Protective Mechanism and Treatment of Neurogenesis in Cerebral Ischemia

Stroke is the fifth leading cause of death worldwide and is a main cause of disability in adults. Neither currently marketed drugs nor commonly used treatments can promote nerve repair and neurogenesis after stroke, and the repair of neurons damaged by ischemia has become a research focus. This article reviews several possible mechanisms of stroke and neurogenesis and introduces novel neurogenic agents (fibroblast growth factors, brain-derived neurotrophic factor, purine nucleosides, resveratrol, S-nitrosoglutathione, osteopontin, etc.) as well as other treatments that have shown neuroprotective or neurogenesis-promoting effects.

Antagonism between the RNA-binding protein Musashi1 and miR-137 and its potential impact on neurogenesis and glioblastoma development

RNA-binding proteins (RBPs) and miRNAs are critical gene expression regulators that interact with one another in cooperative and antagonistic fashions. We identified Musashi1 (Msi1) and miR-137 as regulators of a molecular switch between self-renewal and differentiation. Msi1 and miR-137 have opposite expression patterns and functions, and Msi1 is repressed by miR-137. Msi1 is a stem-cell protein implicated in self-renewal while miR-137 functions as a proneuronal differentiation miRNA. In gliomas, miR-137 functions as a tumor suppressor while Msi1 is a prooncogenic factor. We suggest that the balance between Msi1 and miR-137 is a key determinant in cell fate decisions and disruption of this balance could contribute to neurodegenerative diseases and glioma development. Genomic analyses revealed that Msi1 and miR-137 share 141 target genes associated with differentiation, development, and morphogenesis. Initial results pointed out that these two regulators have an opposite impact on the expression of their target genes. Therefore, we propose an antagonistic model in which this network of shared targets could be either repressed by miR-137 or activated by Msi1, leading to different outcomes (self-renewal, proliferation, tumorigenesis).

Juvenile cerebral ischemia reveals age-dependent BDNF-TrkB signaling changes: Novel mechanism of recovery and therapeutic intervention

Global ischemia in childhood often leads to poor neurologic outcomes, including learning and memory deficits. Using our novel model of childhood cardiac arrest/cardiopulmonary resuscitation (CA/CPR), we investigate the mechanism of ischemia-induced cognitive deficits and recovery. Memory is impaired seven days after juvenile CA/CPR and completely recovers by 30 days. Consistent with this remarkable recovery not observed in adults, hippocampal long-term potentiation (LTP) is impaired 7-14 days after CA/CPR, recovering by 30 days. This recovery is not due to the replacement of dead neurons (neurogenesis), but rather correlates with brain-derived neurotrophic factor (BDNF) expression, implicating BDNF as the molecular mechanism underlying impairment and recovery. Importantly, delayed activation of TrkB receptor signaling reverses CA/CPR-induced LTP deficits and memory impairments. These data provide two new insights (1) endogenous recovery of memory and LTP through development may contribute to improved neurological outcome in children compared to adults and (2) BDNF-enhancing drugs speed recovery from pediatric cardiac arrest during the critical school ages.

Neurotransplantation therapy

Neurotransplantation may be a promising approach for therapy of cerebellar diseases characterized by a substantial loss of neurons. Neurotransplantation could rescue neurons from degeneration and maintain cerebellar reserve, facilitate cerebellar compensation, or help reconstruct damaged neural circuits by cell substitution. These mechanisms of action can be of varying importance according to the type of cerebellar disease. Neurotransplantation therapy in cerebellar ataxias is still at the stage of experimental studies. There is currently little knowledge regarding cerebellar patients. Nevertheless, data provided by experiments in animal models of cerebellar degeneration and both clinical studies and experiences in patients with other neurologic diseases enable us to suggest basic principles, expectations, limitations, and future directions of neurotransplantation therapy for cerebellar diseases.

Sirt1 mediates improvement in cognitive defects induced by focal cerebral ischemia following hyperbaric oxygen preconditioning in rats

Hyperbaric oxygen preconditioning (HBO-PC) has been proposed as a safe and practical approach for neuroprotection in ischemic stroke. However, it is not known whether HPO-PC can improve cognitive deficits induced by cerebral ischemia, and the mechanistic basis for any beneficial effects remains unclear. We addressed this in the present study using rats subjected to middle cerebral artery occlusion (MCAO) as an ischemic stroke model following HBO-PC. Cognitive function and expression of phosphorylated neurofilament heavy polypeptide (pNF-H) and doublecortin (DCX) in the hippocampus were evaluated 14 days after reperfusion and after short interfering RNA-mediated knockdown of sirtuin1 (Sirt1). HBO-PC increased pNF-H and DCX expression and mitigated cognitive deficits in MCAO rats. However, these effects were abolished by Sirt1 knockdown. Our results suggest that HBO-PC can protect the brain from injury caused by ischemia-reperfusion and that Sirt1 is a potential molecular target for therapeutic approaches designed to minimize cognitive deficits caused by cerebral ischemia.

Astrocytic Calcium Waves Signal Brain Injury to Neural Stem and Progenitor Cells

Brain injuries, such as stroke or trauma, induce neural stem cells in the subventricular zone (SVZ) to a neurogenic response. Very little is known about the molecular cues that signal tissue damage, even over large distances, to the SVZ. Based on our analysis of gene expression patterns in the SVZ, 48 hr after an ischemic lesion caused by middle cerebral artery occlusion, we hypothesized that the presence of an injury might be transmitted by an astrocytic traveling calcium wave rather than by diffusible factors or hypoxia. Using a newly established in vitro system we show that calcium waves induced in an astrocytic monolayer spread to neural stem and progenitor cells and increase their self-renewal as well as migratory behavior. These changes are due to an upregulation of the Notch signaling pathway. This introduces the concept of propagating astrocytic calcium waves transmitting brain injury signals over long distances.

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gene profiling after MCAO suggests a role of calcium-binding proteins

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Novel in vitro system to study the effects of astrocytic calcium waves on NSPCs

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Astrocytic calcium waves enhance self-renewal and migration capacity of NSPCs

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The Notch signaling pathway mediates effects of elevated calcium levels on NSPCs

Neurogenesis upregulation on the healthy hemisphere after stroke enhances compensation for age-dependent decrease of basal neurogenesis

Stroke is a leading cause of death and disability worldwide with no treatment for the chronic phase available. Interestingly, an endogenous repair program comprising inflammation and neurogenesis is known to modulate stroke outcome. Several studies have shown that neurogenesis decreases with age but the therapeutic importance of endogenous neurogenesis for recovery from cerebral diseases has been indicated as its ablation leads to stroke aggravation and worsened outcome. A detailed characterization of the neurogenic response after stroke related to ageing would help to develop novel and targeted therapies. In an innovative approach, we used the DCX-Luc mouse, a transgenic model expressing luciferase in doublecortin-positive neuroblasts, to monitor the neurogenic response following middle cerebral artery occlusion over three weeks in three age groups (2, 6, 12months) by optical imaging while the stroke lesion was monitored by quantitative MRI. The individual longitudinal and noninvasive time profiles provided exclusive insight into age-dependent decrease in basal neurogenesis and neurogenic upregulation in response to stroke which are not accessible by conventional BrdU-based measures of cell proliferation. For cortico-striatal strokes the maximal upregulation occurred at 4days post stroke followed by a continuous decrease to basal levels by three weeks post stroke. Older animals effectively compensated for reduced basal neurogenesis by an enhanced sensitivity to the cerebral lesion, resulting in upregulated neurogenesis levels approaching those measured in young mice. In middle aged and older mice, but not in the youngest ones, additional upregulation of neurogenesis was observed in the contralateral healthy hemisphere. This further substantiates the increased propensity of older brains to respond to lesion situation. Our results clearly support the therapeutic relevance of endogenous neurogenesis for stroke recovery and particularly in older brains.

Bumetanide promotes neural precursor cell regeneration and dendritic development in the hippocampal dentate gyrus in the chronic stage of cerebral ischemia

Bumetanide has been shown to lessen cerebral edema and reduce the infarct area in the acute stage of cerebral ischemia. Few studies focus on the effects of bumetanide on neuroprotection and neurogenesis in the chronic stage of cerebral ischemia. We established a rat model of cerebral ischemia by injecting endothelin-1 in the left cortical motor area and left corpus striatum. Seven days later, bumetanide 200 µg/kg/day was injected into the lateral ventricle for 21 consecutive days with a mini-osmotic pump. Results demonstrated that the number of neuroblasts cells and the total length of dendrites increased, escape latency reduced, and the number of platform crossings increased in the rat hippocampal dentate gyrus in the chronic stage of cerebral ischemia. These findings suggest that bumetanide promoted neural precursor cell regeneration, dendritic development and the recovery of cognitive function, and protected brain tissue in the chronic stage of ischemia.

Adult neural stem cell behavior underlying constitutive and restorative neurogenesis in zebrafish

Adult Neural Stem Cells (aNSCs) generate new neurons that integrate into the pre-existing networks in specific locations of the Vertebrate brain. Moreover, aNSCs contribute with new neurons to brain regeneration in some non-mammalian Vertebrates. The similarities and the differences in the cellular and molecular processes governing neurogenesis in the intact and regenerating brain are still to be assessed. Toward this end, we recently established a protocol for non-invasive imaging of aNSC behavior in their niche in vivo in the adult intact and regenerating zebrafish telencephalon. We observed different modes of aNSC division in the intact brain and a novel mode of neurogenesis by direct conversion, which contributes to stem cell depletion with age. After injury, the generation of neurons is increased both by the activation of additional aNSCs and a shift in the division mode of aNSCs, thereby contributing to the successful neuronal regeneration. The cellular behavior we observed opens new questions regarding long-term aNSC maintenance in homeostasis and in regeneration. In this commentary we discuss our data and new questions arising in the context of aNSC behavior, not only in zebrafish but also in other species, including mammals.

Mechanisms and Functional Significance of Stroke-Induced Neurogenesis

Stroke affects one in every six people worldwide, and is the leading cause of adult disability. After stroke, some limited spontaneous recovery occurs, the mechanisms of which remain largely unknown. Multiple, parallel approaches are being investigated to develop neuroprotective, reparative and regenerative strategies for the treatment of stroke. For years, clinical studies have tried to use exogenous cell therapy as a means of brain repair, with varying success. Since the rediscovery of adult neurogenesis and the identification of adult neural stem cells in the late nineties, one promising field of investigation is focused upon triggering and stimulating this self-repair system to replace the neurons lost following brain injury. For instance, it is has been demonstrated that the adult brain has the capacity to produce large numbers of new neurons in response to stroke. The purpose of this review is to provide an updated overview of stroke-induced adult neurogenesis, from a cellular and molecular perspective, to its impact on brain repair and functional recovery.

Electroacupuncture promotes neural stem cell proliferation and neurogenesis in the dentate gyrus of rats following stroke via upregulation of Notch1 expression

Neural stem cells (NSCs) are important in rehabilitation following stroke. Electroacupuncture (EA) treatment has been observed to promote the recovery of neurological functions subsequent to stroke, however, the effects of EA on the proliferation and differentiation of NSCs and its potential mechanisms remain to be elucidated. In the present study, rats, in which a stroke was induced through middle cerebral artery occlusion (MCAO), were treated with EA or control manipulation for 21 days. The modified Neurological Severity score and Morris water maze tests were used to assess the neurological functions of the rats. Bromodeoxyuridine (BrdU)/glial fibrillary acidic protein (GFAP) or BrdU/neuronal marker (NeuN) double immunofluorescence staining were used to examine the proliferation and differentiation of the NSCs. Reverse transcription quantitative polymerase chain reaction (RT‑qPCR) and western blot analyses were performed to detect the expression levels of Notch1 and Hes1 in the dentate gyrus (DG) of the hippocampus of rats following MCAO. The results demonstrated that EA treatment significantly improved the neurological functional recovery of rats following stroke. A significant increase was observed in the number of BrdU+/GAFP+ and BrdU+/NeuN+ cells in the DG area in the EA‑treated rats compared with that of the control group. RT‑qPCR analysis revealed that EA treatment significantly increased the expression levels of Notch1 and Hes1, which may account for the enhanced proliferation and differentiation of NSCs. In conclusion, to the best of our knowledge, the present study was the first to demonstrate that EA treatment promoted NSC proliferation and neurogenesis in the DG area through the upregulation of Notch signaling following a stroke; therefore, EA may be a useful novel therapeutic strategy in future stroke treatment.

Post-stroke transplantation of adult subventricular zone derived neural progenitor cells--A comprehensive analysis of cell delivery routes and their underlying mechanisms

With neuroprotective approaches having failed until recently, current focus on experimental stroke research has switched towards manipulation of post-ischemic neuroregeneration. Transplantation of subventricular zone (SVZ) derived neural progenitor cells (NPCs) is a promising strategy for promotion of neurological recovery. Yet, fundamental questions including the optimal cell delivery route still have to be addressed. Consequently, male C57BL6 mice were exposed to transient focal cerebral ischemia and allowed to survive for as long as 84 days post-stroke. At 6h post-stroke, NPCs were grafted using six different cell delivery routes, i.e., intravenous, intraarterial, ipsilateral intrastriatal, contralateral intrastriatal, ipsilateral intraventricular and ipsilateral intracortical injection. Control mice received PBS only using the aforementioned delivery routes. Intralesional numbers of GFP(+) NPCs were high only after ipsilateral intrastriatal transplantation, whereas other injection paradigms only yielded comparatively small numbers of grafted cells. However, acute neuroprotection and improved functional outcome were observed after both systemic (i.e., intraarterial and intravenous) and ipsilateral intrastriatal transplantation only. Whereas systemic cell delivery induced acute and long-term neuroprotection, reduction of brain injury after ipsilateral intrastriatal cell grafting was only temporary, in line with the loss of transplanted NPCs in the brain. Both systemic and ipsilateral intrastriatal NPC delivery reduced microglial activation and leukocyte invasion, thus reducing free radical formation within the ischemic brain. On the contrary, only systemic NPC administration stabilized the blood-brain-barrier and reduced leukocytosis in the blood. Although intraarterial NPC transplantation was as effective as intravenous cell grafting, mortality of stroke mice was high using the intraarterial delivery route. Consequently, intravenous delivery of native NPCs in our experimental model is an attractive and effective strategy for stroke therapy that deserves further proof-of-concept studies.

Ulinastatin inhibits cerebral ischemia-induced apoptosis in the hippocampus of gerbils

Ulinastatin is a urinary trypsin inhibitor, originally extracted and purified from human urine. Ulinastatin has cytoprotective effects against ischemic injury in several organs. In the present study, the neuroprotective effects of ulinastatin following ischemic cerebral injury in the hippocampus of gerbils was investigated. To induce transient global ischemia in gerbils, the common carotid arteries were occluded using aneurysm clips for 5 min, and the clips were then removed. Ulinastatin was subcutaneously injected into the gerbils once a day for 7 days at doses of 50,000 or 100,000 U/kg. The gerbils were confronted with a step-down avoidance task, following which tissue samples from the gerbils were examined using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining, western blot analysis for B-cell lymphoma (Bcl-2) and Bcl-2-associated X protein (Bax), immunohistochemistry for caspase-3 and immunofluorescence for 5-bromo-2′-deoxyuridine. The numbers of TUNEL-positive and caspase-3-positive cells in the hippocampal CA1 region increased following cerebral ischemia. The expression of Bax in the hippocampus increased, while the expression of Bcl-2 in the hippocampus decreased following cerebral ischemia. These results confirmed that apoptosis in the hippocampus was enhanced following cerebral ischemia in gerbils. The levels of cell proliferation in the hippocampal dentate gyrus were also enhanced by ischemia, which is possibly an adaptive mechanism to compensate for excessive levels of apoptosis. Ulinastatin treatment inhibited ischemia-induced apoptosis by suppressing apoptosis-associated molecules, and thus ameliorated ischemia-induced short-term memory impairment. The cell proliferation in the hippocampus was also suppressed following ulinastatin treatment. These results suggested the use of ulinastatin as a therapeutic agent for patients with cerebral stroke.

The Role of the Two-Pore Domain Potassium Channel TREK-1 in the Therapeutic Effects of Escitalopram in a Rat Model of Poststroke Depression

AIM

Poststroke depression (PSD) is one of the most common neuropsychiatric complications after stroke. TREK-1, a two-pore-domain potassium channel, has been implicated in the pathogenesis of stroke and depression. The aim of this study was to investigate whether TREK-1 plays a role in the therapeutic effects of the selective serotonin reuptake inhibitor (SSRI) escitalopram in a rat PSD model.

METHODS

The whole-cell patch-clamp technique was performed to assess the effect of escitalopram on recombinant TREK-1 currents in HEK293 cells. The expression of TREK-1 mRNA and protein was measured in the hippocampus and prefrontal cortex (PFC), and neural stem cell (NSC) proliferation was detected in the hippocampal dentate gyrus (DG) in PSD rats after 3 weeks of escitalopram administration.

RESULTS

Escitalopram reversibly inhibited TREK-1 currents in a concentration-dependent manner. Chronic treatment with escitalopram significantly reversed the reductions in weight gain, locomotor activity, and sucrose preference in PSD rats. The expressions of TREK-1 mRNA and protein were significantly increased in hippocampal CA1, CA3, DG, and PFC in PSD rats, with the exception of TREK-1 mRNA in hippocampal CA1. NSC proliferation was significantly decreased in hippocampal DG of PSD rats. Escitalopram significantly reversed the regional increases of TREK-1 expression and the reduction of hippocampal NSC proliferation in PSD rats.

CONCLUSION

TREK-1 plays an important role in the therapeutic effects of the SSRI escitalopram in PSD model, making TREK-1 an attractive candidate molecule for further understanding the pathophysiology and treatment of PSD.

In vivo imaging of endogenous neural stem cells in the adult brain

The discovery of endogenous neural stem cells (eNSCs) in the adult mammalian brain with their ability to self-renew and differentiate into functional neurons, astrocytes and oligodendrocytes has raised the hope for novel therapies of neurological diseases. Experimentally, those eNSCs can be mobilized in vivo, enhancing regeneration and accelerating functional recovery after, e.g., focal cerebral ischemia, thus constituting a most promising approach in stem cell research. In order to translate those current experimental approaches into a clinical setting in the future, non-invasive imaging methods are required to monitor eNSC activation in a longitudinal and intra-individual manner. As yet, imaging protocols to assess eNSC mobilization non-invasively in the live brain remain scarce, but considerable progress has been made in this field in recent years. This review summarizes and discusses the current imaging modalities suitable to monitor eNSCs in individual experimental animals over time, including optical imaging, magnetic resonance tomography and-spectroscopy, as well as positron emission tomography (PET). Special emphasis is put on the potential of each imaging method for a possible clinical translation, and on the specificity of the signal obtained. PET-imaging with the radiotracer 3’-deoxy-3’-[¹⁸F]fluoro-L-thymidine in particular constitutes a modality with excellent potential for clinical translation but low specificity; however, concomitant imaging of neuroinflammation is feasible and increases its specificity. The non-invasive imaging strategies presented here allow for the exploitation of novel treatment strategies based upon the regenerative potential of eNSCs, and will help to facilitate a translation into the clinical setting.

Cell replacement therapy: lessons from teleost fish

Many disorders of the CNS are characterized by a massive loss of neurons. A promising therapeutic strategy to cure such conditions is based on the activation of endogenous stem cells. Implementation of this strategy will benefit from a better understanding of stem cell dynamics and the local CNS microenvironment in regeneration-competent vertebrate model systems. Using a spinal cord injury paradigm in zebrafish larvae, Briona and Dorsky (2014) have provided evidence for the existence of two distinct neural stem cell populations. One population has the characteristics of radial glia and expresses the homeobox transcription factor Dbx. The other lacks Dbx but expresses Olig2. These results are placed in the context of other studies that also support the notion of heterogeneity of adult stem cells in the CNS. The implication that differences among stem cell populations, in combination with specific factors from the local cellular microenvironment, might have a decisive impact on the fate choices of the new cells, is discussed. Reviewed evidence suggests that rather few modifications in the signaling pathways involved in the control of stem cell behavior have led, in the course of evolution, to the pronounced differences between mammals and regeneration-competent organisms. As a consequence, rather minor pharmacological manipulations may be sufficient to reactivate the hidden neurogenic potential of the mammalian CNS, and thus make it available for therapeutic applications.

Neurogenesis and inflammation after ischemic stroke: what is known and where we go from here

This review covers the pathogenesis of ischemic stroke and future directions regarding therapeutic options after injury. Ischemic stroke is a devastating disease process affecting millions of people worldwide every year. The mechanisms underlying the pathophysiology of stroke are not fully understood but there is increasing evidence demonstrating the contribution of inflammation to the drastic changes after cerebral ischemia. This inflammation not only immediately affects the infarcted tissue but also causes long-term damage in the ischemic penumbra. Furthermore, the interaction between inflammation and subsequent neurogenesis is not well understood but the close relationship between these two processes has garnered significant interest in the last decade or so. Current approved therapy for stroke involving pharmacological thrombolysis is limited in its efficacy and new treatment strategies need to be investigated. Research aimed at new therapies is largely about transplantation of neural stem cells and using endogenous progenitor cells to promote brain repair. By understanding the interaction between inflammation and neurogenesis, new potential therapies could be developed to further establish brain repair mechanisms.

Electrical stimulation of cerebellar fastigial nucleus: mechanism of neuroprotection and prospects for clinical application against cerebral ischemia

For around two decades, electrical fastigial nucleus stimulation (FNS) has been demonstrated to induce neuroprotection involving multiple mechanisms. In this review, we summarize the protective effects of FNS against cerebral ischemia through the inhibition of electrical activity around the lesion, excitotoxic damage on neurons, and brain inflammatory response, as well as apoptosis. Moreover, FNS has been reported to promote nerve tissue repair, reconstruction, and neurological rehabilitation and improve stroke-related complications including poststroke cognitive dysfunction, depression, and abnormal heart rate variability. We thus further discuss the potential of FNS for clinical applications. Given the absence of any risk of inducing sublethal damage, FNS may offer a new approach to preconditioned neuroprotection against cerebral ischemia.

The expression of FOXJ1 in neurogenesis after transient focal cerebral ischemia

OBJECTIVE AND BACKGROUND

FOXJ1 is a member of the Forkhead/winged-helix (Fox) family of transcription factors, which is required for the differentiation of the cells acting as adult neural stem cells which participate in neurogenesis and give rise to neurons, astrocytes, oligodendrocytes. The expression pattern of FOXJ1 in the brain after cerebral ischemia has so far not been described. In the current study, we investigated the expression pattern of FOXJ1 in the rat brain after cerebral ischemia by animal model.

METHODS

We performed a middle cerebral artery occlusion (MCAO) model in adult rats and investigated the expression of FOXJ1 in the brain by Western blotting and immunochemistry; double immunofluorescence staining was used to analyze FOXJ1's co-expression with Ki67.

RESULTS

Western blot analysis showed that the expression of FOXJ1 was lower than normal and sham-operated brain after cerebral ischemia, but the level of FOXJ1 gradually increased from Day 1 to Day 14. Immuohistochemical staining suggested that the immunostaining of FOXJ1 deposited strongly in the ipsilateral and contralateral hemisphere in the cortical penumbra (CP). There was no FOXJ1 expression in the ischemic core (IC). The positive cells in the cortical penumbra might migrate to the ischemic core. In addition, double immunofluorescence staining revealed that FOXJ1 was co-expressed with mAP-2 and gFAP, and Ki67 had the colocalization with NeuN, GFAP, and FOXJ1.

CONCLUSIONS

All our findings suggest that FOXJ1 plays an important role on neuronal production and neurogenesis in the adult brain after cerebral ischemia.

Perinatal supplementation with omega-3 polyunsaturated fatty acids improves sevoflurane-induced neurodegeneration and memory impairment in neonatal rats

Objectives

To investigate if perinatal Omega-3 polyunsaturated fatty acids (n-3 PUFAs) supplementation can improve sevoflurane-induced neurotoxicity and cognitive impairment in neonatal rats.

Methods

Female Sprague-Dawley rats (n = 3 each group) were treated with or without an n-3 PUFAs (fish oil) enriched diet from the second day of pregnancy to 14 days after parturition. The offspring rats (P7) were treated with six hours sevoflurane administration (one group without sevoflurane/prenatal n-3 PUFAs supplement as control). The 5-bromodeoxyuridine (Brdu) was injected intraperitoneally during and after sevoflurane anesthesia to assess dentate gyrus (DG) progenitor proliferation. Brain tissues were harvested and subjected to Western blot and immunohistochemistry respectively. Morris water maze spatial reference memory, fear conditioning, and Morris water maze memory consolidation were tested at P35, P63 and P70 (n = 9), respectively.

Results

Six hours 3% sevoflurane administration increased the cleaved caspase-3 in the thalamus, parietal cortex but not hippocampus of neonatal rat brain. Sevoflurane anesthesia also decreased the neuronal precursor proliferation of DG in rat hippocampus. However, perinatal n-3 PUFAs supplement could decrease the cleaved caspase-3 in the cerebral cortex of neonatal rats, and mitigate the decrease in neuronal proliferation in their hippocampus. In neurobehavioral studies, compared with control and n-3 PUFAs supplement groups, we did not find significant spatial cognitive deficit and early long-term memory impairment in sevoflurane anesthetized neonatal rats at their adulthood. However, sevoflurane could impair the immediate fear response and working memory and short-term memory. And n-3 PUFAs could improve neurocognitive function in later life after neonatal sevoflurane exposure.

Conclusion

Our study demonstrated that neonatal exposure to prolonged sevoflurane could impair the immediate fear response, working memory and short-term memory of rats at their adulthood, which may through inducing neuronal apoptosis and decreasing neurogenesis. However, these sevoflurane-induced unfavorable neuronal effects can be mitigated by perinatal n-3 PUFAs supplementation.

Effects of acupuncture on the intrastriatal hemorrhage-induced caspase3 expression and newly cell birth in rats

BACKGROUND

Intracerebral hemorrhage is one of the most devastating types of stroke. Caspases are essential players in apoptotic cell death both as initiators and executioners. The v-Fos FBJ murine osteosarcoma viral oncogene homolog (Fos, c-Fos) is an immediate early gene, and Fos expression is sometimes used as a marker for stimuli-induced changes in the metabolic activity of neurons. The expressions of caspase3 and Fos are enhanced with neuroregeneration and with neuronal cell death, respectively. Cells proliferation the dentate gyrus of adult rodents is enhanced by certain pathologic events as seizures and ischemic insult, and such up-regulation of cell proliferation occurring during pathologic situations is thought to be a compensatory response to lesion-induced cell death in the brain. In the present study, we investigated the effects of acupuncture on the intrastriatal hemorrhage-induced caspase3 expression in the striatum and on the Fos expression and cell proliferation in the dentate gyrus of rats.

METHODS

For this study, immunohistochemistry for caspase3, Fos and 5-bromo-2'-deoxyuridine (BrdU) was performed.

RESULTS

Caspase3 expression in the striatum was increased by intrastriatal hemorrhage. Fos expression and cell proliferation in the dentate gyrus of rats with intracerebral hemorrhage were also increased. Acupunctural treatment, especially at the ST36 acupoint, suppressed the intracerebral hemorrhage-induced caspase3 expression in the stratum, and it also inhibited expression of Fos and cell proliferation in the dentate gyrus.

CONCLUSION

In the present study, we have shown that acupuncture treatment has a neuroprotective effect on intrastrstriatal hemorrhage-induced neuronal cell death, and this suggests that acupuncture can aid in the recovery of the central nervous system following stroke.

Temporal changes of neurogenesis in the mouse hippocampus after experimental subarachnoid hemorrhage

Recent studies indicate the existence of progenitor cells and their potential for neurogenesis in the subventricular zone (SVZ) and the hippocampus dentate gyrus (DG) of normal adult mammalian brain. Increased neurogenesis has been shown following cerebral ischemia and traumatic brain injury; however, the involvement of neurogenesis in subarachnoid hemorrhage (SAH) has not been examined. Adult male CD-1 mice were subjected to SAH by endovascular perforation of the left anterior cerebral artery. Mice received intraperitoneal injections of the cell proliferation-specific marker 5'-bromodeoxyuridine (BrdU) after SAH induction. BrdU incorporation was examined from 1 to 30 days after SAH by immunohistochemistry. The BrdU-positive cells were detected in SVZ and DG of normal control brain, and were significantly decreased in both areas three days after SAH. The number of these cells had recovered to its control level seven days after SAH. Double staining with BrdU and NeuN indicated that the majority of the BrdU-positive cells migrating into the granular cell layer of the DG became NeuN-positive 30 days after SAH. In conclusion, temporal changes of the neurogenesis as shown in the present study suggest that neurogenesis in the hippocampus may affect functional outcome after SAH. The induction of the neurogenesis can provide therapeutic value against SAH.

Intraperitoneal treatment with S100B enhances hippocampal neurogenesis in juvenile mice and after experimental brain injury

BACKGROUND

Neurogenesis is documented in adult mammals including humans, is promoted by neurotrophic factors, and constitutes an innate repair mechanism following brain injury. The glial neurotrophic protein S100B is released following various types of brain injuries, enhances hippocampal neurogenesis and improves cognitive function following brain injury in rats when applied intrathecally. The present study was designed to elucidate whether the beneficial effect of S100B on injury-induced neurogenesis can be confirmed in mice when applied intraperitoneally (i.p.), and whether this effect is dose-dependent.

METHODS

Male juvenile mice were subjected to a unilateral parietal cryolesion or sham injury, and treated with S100B at 20nM, 200nM or vehicle i.p. once daily. Hippocampal progenitor cell proliferation was quantified following labelling with bromo-deoxyuridine (BrdU, 50 mg/KG i.p.) in the germinative area of the dentate gyrus, the subgranular zone (SGZ), on day 4 as well as on cell survival and migration to the granular cell layer (GCL) on day 28. Progenitor cell differentiation was assessed following colabelling with the glial marker GFAP and the neuronal marker NeuN.

RESULTS

S100B enhanced significantly the early progenitor cell proliferation in the SGZ as well as cell survival and migration to the GCL, and promoted neuronal differentiation. While these effects were predominately dose-dependent, 200nM S100B failed to enhance the proliferation in the SGZ on day 4 post-injury.

CONCLUSION

We conclude that S100B participates in hippocampal neurogenesis after injury at lower nanomolar concentrations. Therefore S100B may serve as a potential adjunct treatment to promote neuroregeneration following brain damage.

The early stage formation of PI3K-AMPAR GluR2 subunit complex facilitates the long term neuroprotection induced by propofol post-conditioning in rats

Previously, we have shown that the phosphoinositide-3-kinase (PI3K) mediated acute (24 h) post-conditioning neuroprotection induced by propofol. We also found that propofol post-conditioning produced long term neuroprotection and inhibited the internalization of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor GluR2 subunit up to 28 days post middle cerebral artery occlusion (MCAO). However, the relationship between PI3K with AMPA receptor GluR2 subunit trafficking in propofol post-conditioning has never been explored. Here we showed that propofol post-conditioning promoted the binding of PI3K to the C-terminal of AMPA receptor GluR2 subunit and formed a complex within 1 day after transient MCAO. Interestingly, the enhanced activity of PI3K was observed in the hippocampus of post-conditioning rats at day 1 post ischemia, whereas the decrease of AMPA receptor GluR2 subunit internalization was found up to 28 days in the same group. Administration of PI3K selective antagonist wortmannin inhibited the improvement of spatial learning memory and the increase of neurogenesis in the dentate gyrus up to 28 days post ischemia. It also reversed the inhibition of AMPA receptor GluR2 internalization induced by propofol post-conditioning. Together, our data indicated the critical role of PI3K in regulating the long term neuroprotection induced by propofol post-conditioning. Moreover, this role was established by first day activation of PI3K and formation of PI3K-AMPA receptor GluR2 complex, thus stabilized the structure of postsnaptic AMPA receptor and inhibited the internalization of GluR2 subunit during the early stage of propofol post-conditioning.

Amomum villosum induces longitudinal bone growth in adolescent female rats

OBJECTIVE

This study was conducted to evaluate the effect of Amomum villosum on longitudinal bone growth.

METHODS

Adolescent female Sprague-Dawley rats were divided into 3 groups and treated for 4 days: control (distilled water, p.o.), recombinant human growth hormone (rhGH; 100 microg/kg, s.c.), and A. villosum (500 mg/kg, p.o.) groups. On day 3, tetracycline (20 g/kg, i.p.) was injected for growth plate identification. On days 2, and 4, 5-bromo-2'-deoxyuridine (BrdU) (50 mg/kg, i.p.) was injected to label proliferating cells. On day 5, tibias were dissected and fixed in 4% paraformaldehyde, dehydrated, and sectionedfor immunohistochemistry and histomorphometry.

RESULTS

The rate of bone growth in the A. villosum and rhGH groups increased to (410 +/- 44) and (389 +/- 46) microm/day (P<0.01), respectively, as compared with the control (330.7 +/- 34.7) microm/day. The thickness of the growth plates also increased to (591 +/- 37) and (598 +/- 32) microm, respectively, as compared with the control (524 +/- 89) microm (P<0.001). The number of BrdU-positive cells in the chondrocytes of the A. villosum and rhGH groups was also significantly higher (126 +/- 24) and (143 +/- 18) cells/mm2, respectively) than in the control (109 +/- 25) mm2 (P<0.05). Insulin-like growth factor-1 and bone morphogenetic protein-2 in the A. villosum and rhGH groups were highly expressed in the growth plate as compared with the control samples, indicating increased bone formation.

CONCLUSIONS

A. villosum could be used to treat growth retardation during adolescence.

Effect of BDNF-plasma-collagen matrix controlled delivery system on the behavior of adult rats neural stem cells

The neurogenesis amount in central nervous system (CNS) stimulated by the injury or diseases is so small that neural stem cells (NSCs) cannot specifically differentiate into the ideal phenotypes to repair the injured CNS. The transplanted exogenous NSCs also have such problems as poor survival and insufficient neuronal differentiation. In this study, the behavior of NSCs from the spinal cord of adult rats was compared at the neurosphere level after the respective addition of the brain-derived neurotrophic factor (BDNF) daily, the BDNF-loaded plasma-collagen matrix, the plasma-collagen matrix alone, or the defined medium alone. The results suggested that the BDNF, either in the control release form or in the soluble form, initiated NSCs proliferation and differentiation by activating receptors Trk B and p75NTR. BDNF also increased the differentiation percentage of adult NSCs into neurons and supported the long-term cell survival and growth. The BDNF was stably released by the plasma-collagen matrix for up to 21 days. The plasma-collagen matrix alone showed its biocompatibility with cells by facilitating the adhesion, survival, and differentiation of NSCs. The NSCs in the defined medium alone group showed poor survival and a very low level of neuronal differentiation and proliferation abilities than above three groups. This study suggested that the BDNF-loaded plasma-collagen matrix may provide a promising means to resolve either the poor survival and insufficient neuronal differentiation of transplanted exogenous NSCs, or stimulating the intrinsic NSCs to proliferate and differentiate into neurons so as to repair the injured adult CNS.

Neuroprotection targeting ischemic penumbra and beyond for the treatment of ischemic stroke

Neuroprotection to attenuate or block the ischemic cascade and salvage neuronal damage has been extensively explored for the treatment of ischemic stroke. In the last two decades, neuroprotective strategy has been evolving from targeting a signal pathway in neurons to protecting all neurovascular components and improving cell-cell and cell-extracellular matrix interaction that ultimately benefits the brain recovery after ischemic stroke. The progression from potentially reversible to irreversible injury in the ischemic penumbra has provided the opportunity to develop therapies to attenuate the ischemic stroke damage. Thus, the ischemic penumbra has been the main target for the current neuroprotective intervention. However, despite our increasing knowledge of the physiologic, mechanistic, and imaging characterizations of the ischemic penumbra, no effective neuroprotective therapy has been found so far for the treatment of ischemic stroke. The current acute neuroprotective approach focusing on the damaging mechanisms at the ischemic penumbra is greatly limited by the rapid evolution of the deleterious cascades in the ischemic penumbra. Neuroprotective intervention attempts to promote endogenous repairing in the transition zone of the penumbra for the therapeutic purposes may overcome the unrealistic therapeutic windows under the current neuroprotective strategy. In addition, increasing evidence has indicated ischemic stroke could induce long-lasing cellular and hemodynamic changes beyond the ischemic territory. It is unclear whether and how the global responses induced by the ischemic cascade contribute to the progression of cognitive impairment after ischemic stroke. The prolonged pathophysiological cascades induced by ischemic stroke beyond the ischemic penumbra might provide novel therapeutic opportunities for the neuroprotective intervention, which could prevent or slow down the progression of vascular dementia after ischemic stroke.

Human neural stem cell replacement therapy for amyotrophic lateral sclerosis by spinal transplantation

Background

Mutation in the ubiquitously expressed cytoplasmic superoxide dismutase (SOD1) causes an inherited form of Amyotrophic Lateral Sclerosis (ALS). Mutant synthesis in motor neurons drives disease onset and early disease progression. Previous experimental studies have shown that spinal grafting of human fetal spinal neural stem cells (hNSCs) into the lumbar spinal cord of SOD1^G93A rats leads to a moderate therapeutical effect as evidenced by local α-motoneuron sparing and extension of lifespan. The aim of the present study was to analyze the degree of therapeutical effect of hNSCs once grafted into the lumbar spinal ventral horn in presymptomatic immunosuppressed SOD1^G93A rats and to assess the presence and functional integrity of the descending motor system in symptomatic SOD1^G93A animals.

Methods/Principal Findings

Presymptomatic SOD1^G93A rats (60–65 days old) received spinal lumbar injections of hNSCs. After cell grafting, disease onset, disease progression and lifespan were analyzed. In separate symptomatic SOD1^G93A rats, the presence and functional conductivity of descending motor tracts (corticospinal and rubrospinal) was analyzed by spinal surface recording electrodes after electrical stimulation of the motor cortex. Silver impregnation of lumbar spinal cord sections and descending motor axon counting in plastic spinal cord sections were used to validate morphologically the integrity of descending motor tracts. Grafting of hNSCs into the lumbar spinal cord of SOD1^G93A rats protected α-motoneurons in the vicinity of grafted cells, provided transient functional improvement, but offered no protection to α-motoneuron pools distant from grafted lumbar segments. Analysis of motor-evoked potentials recorded from the thoracic spinal cord of symptomatic SOD1^G93A rats showed a near complete loss of descending motor tract conduction, corresponding to a significant (50–65%) loss of large caliber descending motor axons.

Conclusions/Significance

These data demonstrate that in order to achieve a more clinically-adequate treatment, cell-replacement/gene therapy strategies will likely require both spinal and supraspinal targets.

Effects of minocycline on endogenous neural stem cells after experimental stroke

Minocycline has been reported to reduce infarct size after focal cerebral ischemia, due to an attenuation of microglia activation and prevention of secondary damage from stroke-induced neuroinflammation. We here investigated the effects of minocycline on endogenous neural stem cells (NSCs) in vitro and in a rat stroke model. Primary cultures of fetal rat NSCs were exposed to minocycline to characterize its effects on cell survival and proliferation. To assess these effects in vivo, permanent cerebral ischemia was induced in adult rats, treated systemically with minocycline or placebo. Imaging 7 days after ischemia comprised (i) Magnetic Resonance Imaging (MRI), assessing the extent of infarcts, (ii) Positron Emission Tomography (PET) with [(11)C]PK11195, characterizing neuroinflammation, and (iii) PET with 3'-deoxy-3'-[(18)F]fluoro-L-thymidine ([(18)F]FLT), detecting proliferating endogenous NSCs. Immunohistochemistry was used to verify ischemic damage and characterize cellular inflammatory and repair processes in more detail. In vitro, specific concentrations of minocycline significantly increased NSC numbers without increasing their proliferation, indicating a positive effect of minocycline on NSC survival. In vivo, endogenous NSC activation in the subventricular zone (SVZ) measured by [(18)F]FLT PET correlated well with infarct volumes. Similar to in vitro findings, minocycline led to a specific increase in endogenous NSC activity in both the SVZ as well as the hippocampus. [(11)C]PK11195 PET detected neuroinflammation in the infarct core as well as in peri-infarct regions, with both its extent and location independent of the infarct size. The data did not reveal an effect of minocycline on stroke-induced neuroinflammation. We show that multimodal PET imaging can be used to characterize and quantify complex cellular processes occurring after stroke, as well as their modulation by therapeutic agents. We found minocycline, previously implied in attenuating microglial activation, to have positive effects on endogenous NSC survival. These findings hold promise for the development of novel treatments in stroke therapy.

Suppression of astrocyte lineage in adult hippocampal progenitor cells expressing hippocampal cholinergic neurostimulating Peptide precursor in an in vivo ischemic model

Hippocampal cholinergic neurostimulating peptide (HCNP) is known to promote differentiation of septohippocampal cholinergic neurons. The HCNP precursor protein (HCNP-pp) may play several roles, for example, as an ATP-binding protein, a Raf kinase inhibitor protein, and a phosphatidylethanolamine-binding protein, as well as a precursor for HCNP. This study therefore aimed to elucidate the involvement of HCNP-pp in specific neural lineages after stroke using a hypoxic-ischemic (HI) rat model of brain ischemia. The specific neural lineages in the hippocampus were investigated 14 days after ischemia. Some bromodeoxyuridine (BrdU)(+) neural progenitor cells in the hippocampus of hypoxic, HI, or sham-operated rats expressed HCNP-pp. Almost half of the BrdU(+)/HCNP-pp(+) cells also expressed the oligodendrocyte lineage marker 2',3'-cyclic nucleotide 3'-phosphodiesterase, whereas only a few BrdU(+)/HCNP-pp(+) cells in the hippocampus in HI brains expressed the neuronal lineage marker, doublecortin (DCX). Interestingly, no BrdU(+)/HCNP-pp(+) progenitor cells in hypoxic, HI, or sham-operated brains expressed the astrocyte lineage marker, glial fibrillary acidic protein. Together with previous in vitro data, the results of this study suggest that the expression level of HCNP-pp regulates the differentiation of neural progenitor cells into specific neural lineages in the HI hippocampus, indicating that neural stem cell fate can be controlled via the HCNP-pp mediating pathway.

Posttraumatic hypothermia increases doublecortin expressing neurons in the dentate gyrus after traumatic brain injury in the rat

Previous studies have demonstrated that moderate hypothermia reduces histopathological damage and improves behavioral outcome after experimental traumatic brain injury (TBI). Further investigations have clarified the mechanisms underlying the beneficial effects of hypothermia by showing that cooling reduces multiple cell injury cascades. The purpose of this study was to determine whether hypothermia could also enhance endogenous reparative processes following TBI such as neurogenesis and the replacement of lost neurons. Male Sprague-Dawley rats underwent moderate fluid-percussion brain injury and then were randomized into normothermia (37°C) or hypothermia (33°C) treatment. Animals received injections of 5-bromo-2'-deoxyuridine (BrdU) to detect mitotic cells after brain injury. After 3 or 7 days, animals were perfusion-fixed and processed for immunocytochemistry and confocal analysis. Sections were stained for markers selective for cell proliferation (BrdU), neuroblasts and immature neurons (doublecortin), and mature neurons (NeuN) and then analyzed using non-biased stereology to quantify neurogenesis in the dentate gyrus (DG). At 7 days after TBI, both normothermic and hypothermic TBI animals demonstrated a significant increase in the number of BrdU-immunoreactive cells in the DG as compared to sham-operated controls. At 7 days post-injury, hypothermia animals had a greater number of BrdU (ipsilateral cortex) and doublecortin (ipsilateral and contralateral cortex) immunoreactive cells in the DG as compared to normothermia animals. Because adult neurogenesis following injury may be associated with enhanced functional recovery, these data demonstrate that therapeutic hypothermia sustains the increase in neurogenesis induced by TBI and this may be one of the mechanisms by which hypothermia promotes reparative strategies in the injured nervous system.

Propofol post-conditioning induced long-term neuroprotection and reduced internalization of AMPAR GluR2 subunit in a rat model of focal cerebral ischemia/reperfusion

We previously reported that propofol (20 mg/kg/h) post-conditioning provided acute (up to 24 h) neuroprotection in rats with transient middle cerebral artery occlusion. In this study, we extend these data by examining long-term protection and exploring underlying mechanisms involving AMPA receptor GluR2 subunit internalization. Rats were treated with propofol 20 mg/kg/h after 60 min of occlusion (beginning of reperfusion for 4 h). Propofol post-conditioning reduced infarct volume and improved spatial memory deficiencies (up to 28 days) induced by ischemia/reperfusion injury. Additionally, Propofol post-conditioning promoted neurogenesis in the dentate gyrus of hippocampus, as measured by bromodeoxyuridine and neuron-specific nuclear protein immunofluorescence-double staining at day 28 after reperfusion. Finally, propofol post-conditioning increased the surface expression of AMPA receptor GluR2 subunit, thus inhibited the internalization of this part until 28 days after stroke. In conclusion, our data suggest that propofol post-conditioning provides long-term protection against focal cerebral ischemia/reperfusion injury in rats. Furthermore, we found that the inhibition of AMPA receptor GluR2 subunit internalization may contributed to this long-term neuroprotection.

Injury-induced neurogenesis in the mammalian forebrain

It has been accepted that new neurons are added to the olfactory bulb and the hippocampal dentate gyrus throughout life in the healthy adult mammalian brain. Recent studies have clarified that brain insult raises the proliferation of neural stem cells/neural progenitor cells existing in the subventricular zone and the subgranular zone, which become sources of new neurons for the olfactory bulb and the dentate gyrus, respectively. Interestingly, convincing data has shown that brain insult invokes neurogenesis in various brain regions, such as the hippocampal cornu ammonis region, striatum, and cortex. These reports suggest that neural stem cells/neural progenitor cells, which can be activated by brain injury, might be broadly located in the adult brain or that new neurons may migrate widely from the neurogenic regions. This review focuses on brain insult-induced neurogenesis in the mammalian forebrain, especially in the neocortex.

The herbal formula HT042 induces longitudinal bone growth in adolescent female rats

The effect of HT042, a blend of three herbal extracts, on longitudinal bone growth was investigated in short- and long-term rat models. In the short-term model, we divided female Sprague-Dawley rats (3 weeks old) into six groups, according to treatment: vehicle, HT042 (100 mg/kg), Phlomis umbrosa (100 mg/kg), Astragalus membranaceus (100 mg/kg), and Eleutherococcus senticosus (100 mg/kg) were administered twice daily, and recombinant human growth hormone (rhGH) (1 IU) was subcutaneously injected once daily. Treatments were maintained for 4 days in each case. On day 3, tetracycline (20 mg/kg) was injected intraperitoneally (20 mg/kg) to form the fluorescent band on the growth plates. On days 2-4, 5-bromo-2'-deoxyuridine (BrdU) (50 mg/kg) was injected intraperitoneally to label proliferating cells. On day 5, the tibias were dissected and fixed in 30% sucrose. Dehydrated bone was sectioned at a thickness of 40 μm and observed. The bone growth in groups administered HT042 and rhGH was significantly increased to 433.50 ± 21.61 and 434.49 ± 15.21 μm/day, respectively, from 410.03 ± 17.4 μm/day (control). The height of the growth plates in the HT042 and rhGH groups was also significantly increased to 556.5 ± 21.1 and 544.2 ± 21.1 μm (P < .05), respectively, from 518.1 ± 4.1 μm (normal). The number of BrdU-positive cells in chondrocytes of the HT042 and rhGH groups was increased to 389 ± 36 and 627 ± 39 cells/mm² (P < .001), respectively, from 264 ± 17 cells/mm² (control). Insulin-like growth factor-1 and bone morphogenetic protein-2 in the HT042 group were highly expressed in the growth plate. In the long-term rat model, the body weight, nose-tail length, and nose-anus length were measured by microknemometry for 4 weeks. The body weight of the rhGH group was significantly increased. The nose-anus length of the HT042 and rhGH groups was significantly greater at 18.5 ± 0.3 and 18.7 ± 0.3 cm compared to 18.2 ± 0.2 cm (control).