Three steps of neural stem cells development in gerbil dentate gyrus after transient ischemia

Adeno-associated Virus-mediated Ezh2 Knockdown Reduced the Increment of Newborn Neurons Induced by Forebrain Ischemia in Gerbil Dentate Gyrus

It is established that neurogenesis of dentate gyrus is increased after ischemic insult, although the regulatory mechanisms have not yet been elucidated. In this study, we focused on Ezh2 which suppresses gene expression through catalyzing trimethylation of lysine 27 of histone 3. Male gerbils were injected with adeno-associated virus (AAV) carrying shRNA targeting to Ezh2 into right dentate gyrus 2 weeks prior to forebrain ischemia. One week after ischemia, animals were injected with thymidine analogue to label proliferating cells. Three weeks after ischemia, animals were killed for histological analysis. AAV-mediated knockdown of Ezh2 significantly decreased the ischemia-induced increment of proliferating cells, and the proliferated cells after ischemia showed significantly longer migration from subgranular zone (SGZ), compared to the control group. Furthermore, the number of neural stem cells in SGZ significantly decreased after ischemia with Ezh2 knockdown group. Of note, Ezh2 knockdown did not affect the number of proliferating cells or the migration from SGZ in the non-ischemic condition. Our data showed that, specifically after ischemia, Ezh2 knockdown shifted the balance between self-renewal and differentiation toward differentiation in adult dentate gyrus.

Comparative insight into the regenerative mechanisms of the adult brain in zebrafish and mouse: highlighting the importance of the immune system and inflammation in successful regeneration

Regeneration, the complex process of restoring damaged or absent cells, tissues, and organs, varies considerably between species. The zebrafish is a remarkable model organism for its impressive regenerative abilities, particularly in organs such as the heart, fin, retina, spinal cord, and brain. Unlike mammals, zebrafish can regenerate with limited or absent scarring, a phenomenon closely linked to the activation of stem cells and immune cells. This review examines the unique roles played by the immune response and inflammation in zebrafish and mouse during regeneration, highlighting the cellular and molecular mechanisms behind their divergent regenerative capacities. By focusing on zebrafish telencephalic regeneration and comparing it to that of the rodents, this review highlights the importance of a well-controlled, acute, and non-persistent immune response in zebrafish, which promotes an environment conducive to regeneration. The knowledge gained from understanding the mechanisms of zebrafish regeneration holds great promises for the treatment of human neurodegenerative diseases and brain damage (stroke and traumatic brain injuries), as well as for the advancement of regenerative medicine approaches.

Neuregulin-1/PI3K signaling effects on oligodendrocyte proliferation, remyelination and behaviors deficit in a male mouse model of ischemic stroke

In this study, we investigated the effect of neuregulin-1 (NRG1) on demyelination and neurological function in an ischemic stroke model, and further explored its neuroprotective mechanisms. Adult male ICR mice underwent photothrombotic ischemia surgery and were injected with NRG1 beginning 30 min after ischemia. Cylinder and grid walking tests were performed to evaluate the forepaw function. In addition, the effect of NRG1 on neuronal damage/death (Cresyl violet, CV), neuronal nuclei (NeuN), nestin, doublecortin (DCX), myelin basic protein (MBP), non-phosphorylated neurofilaments (SMI-32), adenomatous polyposis coli (APC), erythroblastic leukemia viral oncogene homolog (ErbB) 2, 4 and serine-threonine protein kinase (Akt) in cortex were evaluated using immunohistochemistry, immunofluorescence and western blot. The cylinder and grid walking tests exposed that treatment of NRG1 observably regained the forepaw function. NRG1 treatment reduced cerebral infarction, restored forepaw function, promoted proliferation and differentiation of neuron and increased oligodendrogliogenesis. The neuroprotective effect of NRG1 is involved in its activation of PI3K/Akt signaling pathway via ErbB2, as shown by the suppression of the effect of NRG1 by the PI3K inhibitor LY294002. Our results demonstrate that NRG1 is effective in ameliorating the both acute phase neuroprotection and long-term neurological functions via resumption of neuronal proliferation and differentiation and oligodendrogliogenesis in a male mouse model of ischemic stroke.

Cuprizone Affects Hypothermia-Induced Neuroprotection and Enhanced Neuroblast Differentiation in the Gerbil Hippocampus after Ischemia

In the present study, we investigated the effects of cuprizone on cell death, glial activation, and neuronal plasticity induced by hypothermia after ischemia in gerbils. Food was supplemented with cuprizone at 0.2% ad libitum for eight weeks. At six weeks after diet feeing, gerbils received transient forebrain ischemia with or without hypothermic preconditioning. Cuprizone treatment for 8 weeks increased the number of astrocytes, microglia, and pro-inflammatory cytokine levels in the hippocampus. In addition, cuprizone treatment significantly decreased the number of proliferating cells and neuroblasts in the dentate gyrus. Brain ischemia caused cell death, disruption of myelin basic proteins, and reactive gliosis in CA1. In addition, ischemia significantly increased pro-inflammatory cytokines and the number of proliferating cells and differentiating neuroblasts in the dentate gyrus. In contrast, hypothermic conditioning attenuated these changes in CA1 and the dentate gyrus. However, cuprizone treatment decreased cell survival induced by hypothermic preconditioning after ischemia and increased the number of reactive microglia and astrocytes in CA1 as well as that of macrophages in the subcallosal zone. These changes occurred because the protective effect of hypothermia in ischemic damage was disrupted by cuprizone administration. Furthermore, cuprizone decreased ischemia-induced proliferating cells and neuroblasts in the dentate gyrus.

Differential roles of exogenous protein disulfide isomerase A3 on proliferating cell and neuroblast numbers in the normal and ischemic gerbils

INTRODUCTION

We examined the effects of exogenous protein disulfide isomerase A3 (PDIA3) on hippocampal neurogenesis in gerbils under control and ischemic damage.

METHODS

To facilitate the delivery of PDIA3 to the brain, we constructed Tat-PDIA3 protein and administered vehicle (10% glycerol) or Tat-PDIA3 protein once a day for 28 days. On day 24 of vehicle or Tat-PDIA3 treatment, ischemia was transiently induced by occlusion of both common carotid arteries for 5 min.

RESULTS

Administration of Tat-PDIA3 significantly reduced ischemia-induced spontaneous motor activity, and the number of NeuN-positive nuclei in the Tat-PDIA3-treated ischemic group was significantly increased in the CA1 region compared to that in the vehicle-treated ischemic group. Ki67- and DCX-immunoreactive cells were significantly higher in the Tat-PDIA3-treated group compared to the vehicle-treated control group. In vehicle- and Tat-PDIA3-treated ischemic groups, the number of Ki67- and DCX-immunoreactive cells was significantly higher as compared to those in the vehicle- and Tat-PDIA3-treated control groups, respectively. In the dentate gyrus, the numbers of Ki67-immunoreactive cells were comparable between vehicle- and Tat-PDIA3-treated ischemic groups, while more DCX-immunoreactive cells were observed in the Tat-PDIA3-treated group. Transient forebrain ischemia increased the expression of phosphorylated cAMP-response element-binding protein (pCREB) in the dentate gyrus, but the administration of Tat-PDIA3 robustly increased pCREB-positive nuclei in the normal gerbils, but not in the ischemic gerbils. Brain-derived neurotrophic factor (BDNF) mRNA expression was significantly increased in the Tat-PDIA3-treated group compared to that in the vehicle-treated group. Transient forebrain ischemic increased BDNF mRNA levels in both vehicle- and Tat-PDIA3-treated groups, and there were no significant differences between groups.

CONCLUSIONS

These results suggest that Tat-PDIA3 enhances cell proliferation and neuroblast numbers in the dentate gyrus in normal, but not in ischemic gerbils, by increasing BDNF mRNA and phosphorylation of pCREB.

Therapeutic Potential of Neurotrophins for Repair After Brain Injury: A Helping Hand From Biomaterials

Stroke remains the leading cause of long-term disability with limited options available to aid in recovery. Significant effort has been made to try and minimize neuronal damage following stroke with use of neuroprotective agents, however, these treatments have yet to show clinical efficacy. Regenerative interventions have since become of huge interest as they provide the potential to restore damaged neural tissue without being limited by a narrow therapeutic window. Neurotrophins, such as brain-derived neurotrophic factor (BDNF), and their high affinity receptors are actively produced throughout the brain and are involved in regulating neuronal activity and normal day-to-day function. Furthermore, neurotrophins are known to play a significant role in both protection and recovery of function following neurodegenerative diseases such as stroke and traumatic brain injury (TBI). Unfortunately, exogenous administration of these neurotrophins is limited by a lack of blood-brain-barrier (BBB) permeability, poor half-life, and rapid degradation. Therefore, we have focused this review on approaches that provide a direct and sustained neurotrophic support using pharmacological therapies and mimetics, physical activity, and potential drug delivery systems, including discussion around advantages and limitations for use of each of these systems. Finally, we discuss future directions of biomaterial drug-delivery systems, including the incorporation of heparan sulfate (HS) in conjunction with neurotrophin-based interventions.

Neurogenesis changes and the fate of progenitor cells after subarachnoid hemorrhage in rats

BACKGROUND

Subarachnoid hemorrhage (SAH) is a devastating cerebrovascular disease that leads to poor outcomes. Neurogenesis, an essential recovery mechanism after brain injury, has not been fully elucidated after SAH.

METHODS

A total of 122 SD rats were used in this study. For experiment one, the rats were randomly divided into six groups: sham and SAH with different time points (1,3,5,7,14 days) (n = 12/group). An endovascular perforation method was conducted for SAH model. Rats were injected with 5-Bromo-2'-deoxyuridine (BrdU, 50 mg/kg) 24 h before euthanasia at different time points after SAH. The BrdU labeled cells were detected by immunohistochemistry; Doublecortin (DCX) and glial fibrillary acidic protein (GFAP) were measured by western blot and immunohistochemistry. For experiment two, rats were randomly divided into five groups: sham and SAH with different time points (1, 2, 4, 8 weeks) (n = 6/group). Rats received BrdU (50 mg/kg) once daily for 7 days after the induction of SAH. Double immunofluorescence staining was used to verify proliferation, differentiation and migration of progenitor cells. Rotarod test and water maze used to test the neurobehavioral recovery.

RESULTS

Our results showed that BrdU positive cells in hippocampus changed overtime after SAH. BrdU positive cells decreased as early as 1 day reaching lowest levels at 3 days after SAH, after which it gradually recovered. Similar change patterns were observed with DCX, which was reversed with GFAP. In addition, BrdU did not co-localize with cleaved caspase-3. The BrdU positive cells mainly differentiated into immature neurons for short-term fate, whereas they differentiated into mature neurons for long-term fate but not astrocytes, which facilitated neurobehavioral recovery after SAH.

CONCLUSION

Neurogenesis in the hippocampus changes overtime after SAH. The neuronal progenitor cells may play an essential role in the neurobehavioral recovery after brain injury induced by SAH, since short-term progenitors helped with the recovery of immature neurons in the hippocampus, whereas long-term progenitors differentiated into mature neurons.

Positive effects of α-asarone on transplanted neural progenitor cells in a murine model of ischemic stroke

BACKGROUND

Some traditional Oriental herbal medicines, such as Acorus tatarinowii and Acorus gramineus, produce beneficial effects for cognition enhancement. An active compound in rhizomes and the bark of these plants is α-asarone.

PURPOSE

This study investigated the effects of α-asarone on the proliferation and differentiation of neural progenitor cells (NPCs) in a primary culture and a murine model of ischemic stroke.

METHODS

NPCs were isolated from mouse fetal cerebral cortices on embryonic day 15, and all experiments were performed using passage 3 NPCs. We utilized a cell counting kit-8 assay, flow cytometry, western blot, and immunohistochemical analysis to assess proliferation and differentiation of NPCs and employed α-asarone in NPC transplanted ischemic stroke mice to evaluate stroke-related functional recovery using behavioral and immunohistochemical analysis.

RESULT

Treatment with 1 µM, 3 µM, or 10 μM α-asarone induced significant NPC proliferation compared to vehicle treatment. Induced NPCs expressed the neuronal marker neuronal nuclei (NeuN) or the astrocyte marker S100 calcium-binding protein B (S100β). Both immunohistochemistry and flow cytometry revealed that treatment with α-asarone increased the number of NeuN-immunoreactive cells and decreased the number of S100β-immunoreactive cells. Treatment with α-asarone also increased the expression of β-catenin, cyclin D1, and phosphorylated extracellular signal-regulated kinase (ERK) compared to vehicle treatment. In a murine model of ischemic stroke, treatment with α-asarone and transplanted NPCs alleviated stroke-related functional impairments. The corner and rotarod test results revealed that treatment with α-asarone in the NPC transplanted group had greater-than-additive effects on sensorimotor function and motor balance. Moreover, α-asarone treatment promoted the differentiation of transplanted NPCs into NeuN-, glial fibrillary acidic protein (GFAP)-, platelet-derived growth factor-α (PDGFR-α)-, and 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNPase)-immunoreactive cells.

CONCLUSION

α-asarone may promote NPC proliferation and differentiation into neuron-lineage cells by activating β-catenin, cyclin D1, and ERK. Moreover, α-asarone treatment facilitated neurofunctional recovery after NPC transplantation in a murine model of ischemic stroke. Therefore, α-asarone is a potential adjunct treatment to NPC therapy for functional restoration after brain injuries such as ischemic stroke.

Tetramethylpyrazine nitrone activates the BDNF/Akt/CREB pathway to promote post-ischaemic neuroregeneration and recovery of neurological functions in rats

BACKGROUND AND PURPOSE

Neuronal regeneration from endogenous precursors is an attractive strategy for the treatment of ischaemic stroke. However, most stroke-generated newborn neurons die over time. Therefore, a drug that is both neuroprotective and pro-neurogenic may be beneficial after stroke. Here, we assessed the neurogenic and oligodendrogenic effects of tetramethylpyrazine nitrone (TBN), a neuroprotective drug candidate for stroke, in a rat model of ischaemic stroke.

EXPERIMENTAL APPROACH

We used Sprague Dawley rats with middle cerebral artery occlusion (MCAO). TBN was administered by tail vein injection beginning at 3 h post ischaemia. Therapeutic effect of TBN was evaluated by neurological behaviour and cerebral infarction. Promotion of neurogenesis and oligodendrogenesis was determined by double immunofluorescent staining and Western blotting analyses. Primary cultures of cortical neurons were used to assess the effect of TBN on neuronal differentiation in vitro.

KEY RESULTS

TBN reduced cerebral infarction, preserved and/or restored neurological function and promoted neurogenesis and oligodendrogenesis in rats after MCAO. In addition, TBN stimulated neuronal differentiation on primary culture of cortical neurons in vitro. Pro-neurogenic effects of TBN were attributed to its activation of the AKT/cAMP responsive element-binding protein through increasing brain-derived neurotrophic factor (BDNF) expression, as shown by the abolition of the effects of TBN by a specific inhibitor of BDNF receptor ANA-12 and by the PI3K inhibitor LY294002.

CONCLUSION AND IMPLICATIONS

As TBN can simultaneously provide neuroprotection and pro-neurogenic effects, it may be a promising treatment for both acute phase neuroprotection and long-term functional recovery after ischaemic stroke.

Molecular imaging of nestin in neuroinflammatory conditions reveals marked signal induction in activated microglia

Background

Nestin is a known marker of neuronal progenitor cells in the adult brain. Following neuro- and gliogenesis, nestin is replaced by cell type-specific intermediate filaments, e.g., neurofilaments for panneuronal expression and glial fibrillary acidic protein as a specific marker of mature astrocytes. While previous work have been mostly focused on the neuronal fate of nestin-positive progenitors, in the present study, we sought to investigate in real time how nestin signals and cellular expression patterns are controlled in the context of neuroinflammatory challenge and ischemic brain injury.

Methods

To visualize effects of neuroinflammation on neurogenesis/gliogenesis, we created a transgenic model bearing the dual reporter system luciferase and GFP under transcriptional control of the murine nestin promoter. In this model, transcriptional activation of nestin was visualized from the brains of living animals using biophotonic/bioluminescence molecular imaging and a high resolution charged coupled device camera. Nestin induction profiles in vivo and in tissue sections were analyzed in two different experimental paradigms: middle cerebral artery occlusion and lipopolysaccharide-induced innate immune stimuli.

Results

We report here a context- and injury-dependent induction and cellular expression profile of nestin. While in the baseline conditions the nestin signal and/or GFP expression was restricted to neuronal progenitors, the cellular expression patterns of nestin following innate immune challenge and after stroke markedly differed shifting the cellular expression patterns towards activated microglia/macrophages and astrocytes.

Conclusions

Our results suggest that nestin may serve as a context-dependent biomarker of inflammatory response in glial cells including activated microglia/macrophages.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0816-7) contains supplementary material, which is available to authorized users.

Function of neural stem cells in ischemic brain repair processes

Hypoxic/ischemic injury is the single most important cause of disabilities in infants, while stroke remains a leading cause of morbidity in children and adults around the world. The injured brain has limited repair capacity, and thereby only modest improvement of neurological function is evident post injury. In rodents, embryonic neural stem cells in the ventricular zone generate cortical neurons, and adult neural stem cells in the ventricular-subventricular zone of the lateral ventricle produce new neurons through animal life. In addition to generation of new neurons, neural stem cells contribute to oligodendrogenesis. Neurogenesis and oligodendrogenesis are essential for repair of injured brain. Much progress has been made in preclinical studies on elucidating the cellular and molecular mechanisms that control and coordinate neurogenesis and oligodendrogenesis in perinatal hypoxic/ischemic injury and the adult ischemic brain. This article will review these findings with a focus on the ventricular-subventricular zone neurogenic niche and discuss potential applications to facilitate endogenous neurogenesis and thereby to improve neurological function post perinatal hypoxic/ischemic injury and stroke.

Wuweizi protects against liver cirrhosis by promoting endogenous stem cell proliferation

AIM: To investigate the mechanism for Wuweizi to treat liver cirrhosis.

METHODS: A rat model of liver cirrhosis was developed with CCl₄. Rats were randomly divided into five groups: three treatment groups [small dose Wuweizi group (A1), middle dose group (A2) and high dose group (A3)], a blank group (C) and a model group (M). Except group C, liver cirrhosis was induced in all other groups. Groups A1, A2 and A3 were given 1.0, 1.5 and 2.0 mg/200 g Wuweizi, respectively. After treatment, histopathology, liver function [aspartate transaminase (AST), alanine transaminase (ALT) and albumin (ALB)], hepatic fibrosis, stem cell proliferation, and the expression ofCK-18, ALB and α-fetoprotein (AFP) were assessed.

RESULTS: In the treatment groups, there was an improvement in the degree of hepatic fibrosis and the condition of liver cell degeneration and necrosis, as revealed by HE staining and Masson staining, and the liver fibrosis scores were different among each treatment group (P < 0.05). Compared with group M, the liver fibrosis score of group A2 was improved most obviously (P < 0.01). Immunohistochemistry analysis showed that the expression of CK-18, ALB and AFP was different between each treatment group (P < 0.05). By labeling liver tissue stem cells with BrdU, the proliferation and division of stem cells were observed through the method of "regional coexistence". Immunofluorescence analysis revealed that the expression of CK-18, ALB and AFP were different among each treatment group (P < 0.01), with group A2 having the most prominent expression (P < 0.01). Liver function was improved differently in each treatment group (P < 0.05). Compared with group M, AST and ALT were decreased most significantly and ALB increased most obviously in group A2 (P < 0.01).

CONCLUSION: Wuweizi has a protective effect on injured liver cells. Wuweizi could delay the process of liver cirrhosis via mechanisms possibly related to promoting the proliferation of endogenous stem cells.

Critical Role of the Sphingolipid Pathway in Stroke: a Review of Current Utility and Potential Therapeutic Targets

Sphingolipids are a series of cell membrane-derived lipids which act as signaling molecules and play a critical role in cell death and survival, proliferation, recognition, and migration. Sphingosine-1-phosphate acts as a key signaling molecule and regulates lymphocyte trafficking, glial cell activation, vasoconstriction, endothelial barrier function, and neuronal death pathways which plays a critical role in numerous neurological conditions. Stroke is a second leading cause of death all over the world and effective therapies are still in great demand, including ischemic stroke and hemorrhagic stroke as well as poststroke repair. Significantly, sphingolipid activities change after stroke and correlate with stroke outcome, which has promoted efforts to testify whether the sphingolipid pathway could be a novel therapeutic target in stroke. The sphingolipid metabolic pathway, the connection between the pathway and stroke, as well as therapeutic interventions to manipulate the pathway to reduce stroke-induced brain injury are discussed in this review.

Identification of miRNomes associated with adult neurogenesis after stroke using Argonaute 2-based RNA sequencing

Neurogenesis is associated with functional recovery after stroke. However, the underlying molecular mechanisms have not been fully investigated. Using an Ago2-based RNA immunoprecipitation to immunoprecipated Ago2-RNA complexes followed by RNA sequencing (Ago2 RIP-seq) approach, we profiled the miRNomes in neural progenitor cells (NPCs) harvested from the subventricular zone (SVZ) of the lateral ventricles of young adult rats. We identified more than 7 and 15 million reads in normal and ischemic NPC libraries, respectively. We found that stroke substantially changed Ago2-associated miRNA profiles in NPCs compared to those in non-ischemic NPCs. We also discovered a new complex repertoire of isomiRs and multiple miRNA-miRNA* pairs and numerous novel miRNAs in the non-ischemic and ischemic NPCs. Among them, pc-3p-17172 significantly regulated NPC proliferation and neuronal differentiation. Collectively, the present study reveals profiles of Ago2-associated miRNomes in non-ischemic and ischemic NPCs, which provide a molecular basis to further investigate the role of miRNAs in mediating adult neurogenesis under physiological and ischemic conditions.

Dietary supplementation with omega-3 polyunsaturated fatty acids robustly promotes neurovascular restorative dynamics and improves neurological functions after stroke

Stroke is a devastating neurological disease with no satisfactory therapies to preserve long-term neurological function, perhaps due to the sole emphasis on neuronal survival in most preclinical studies. Recent studies have revealed the importance of protecting multiple cell types in the injured brain, such as oligodendrocytes and components of the neurovascular unit, before long-lasting recovery of function can be achieved. For example, revascularization in the ischemic penumbra is critical to provide various neurotrophic factors that enhance the survival and activity of neurons and other progenitor cells, such as oligodendrocyte precursor cells. In the present study, we hypothesized that chronic dietary supplementation with fish oil promotes post-stroke angiogenesis, neurogenesis, and oligodendrogenesis, thereby leading to long-term functional improvements. Mice received dietary supplementation with n-3 PUFA-enriched fish oil for three months before and up to one month after stroke. As expected, dietary n-3 PUFAs significantly increased levels of n-3 PUFAs in the brain and improved long-term behavioral outcomes after cerebral ischemia. n-3 PUFAs also robustly improved revascularization and angiogenesis and boosted the survival of NeuN/BrdU labeled newborn neurons up to 35days after stroke injury. Furthermore, these pro-neurogenic effects were accompanied by robust oligodendrogenesis. Thus, this is the first study to demonstrate that chronic dietary intake of n-3 PUFAs is an effective prophylactic measure not only to protect against ischemic injury for the long term but also to actively promote neurovascular restorative dynamics and brain repair.

Fish oil supplementation associated with decreased cellular degeneration and increased cellular proliferation 6 weeks after middle cerebral artery occlusion in the rat

Anti-inflammatory long-chain omega-3 polyunsaturated fatty acids (n-3-LC-PUFAs) are both neuroprotective and have antidepressive effects. However the influence of dietary supplemented n-3-LC-PUFAs on inflammation-related cell death and proliferation after middle cerebral artery occlusion (MCAo)-induced stroke is unknown. We have previously demonstrated that anxiety-like and hyperactive locomotor behaviors are reduced in n-3-LC-PUFA-fed MCAo animals. Thus in the present study, male hooded Wistar rats were exposed to MCAo or sham surgeries and examined behaviorally 6 weeks later, prior to euthanasia and examination of lesion size, cell death and proliferation in the dentate gyrus, cornu ammonis region of the hippocampus of the ipsilesional hemispheres, and the thalamus of the ipsilesional and contralesional hemispheres. Markers of cell genesis and cell degeneration in the hippocampus or thalamus of the ipsilesional hemisphere did not differ between surgery and diet groups 6 weeks post MCAo. Dietary supplementation with n-3-LC-PUFA decreased cell degeneration and increased cell proliferation in the thalamic region of the contralesional hemisphere. MCAo-associated cell degeneration in the hippocampus and thalamus positively correlated with anxiety-like and hyperactive locomotor behaviors previously reported in these animals. These results suggest that anti-inflammatory n-3-LC-PUFA supplementation appears to have cellular protective effects after MCAo in the rat, which may affect behavioral outcomes.

Maintenance and neuronal cell differentiation of neural stem cells C17.2 correlated to medium availability sets design criteria in microfluidic systems

BACKGROUND

Neural stem cells (NSCs) play an important role in developing potential cell-based therapeutics for neurodegenerative disease. Microfluidics has proven a powerful tool in mechanistic studies of NSC differentiation. However, NSCs are prone to differentiate when the nutrients are limited, which occurs unfavorable by fast medium consumption in miniaturized culture environment. For mechanistic studies of NSCs in microfluidics, it is vital that neuronal cell differentiation is triggered by controlled factors only. Thus, we studied the correlation between available cell medium and spontaneous neuronal cell differentiation of C17.2 NSCs in standard culture medium, and proposed the necessary microfluidic design criteria to prevent undesirable cell phenotype changes.

METHODOLOGY/PRINCIPAL FINDINGS

A series of microchannels with specific geometric parameters were designed to provide different amount of medium to the cells over time. A medium factor (MF, defined as the volume of stem cell culture medium divided by total number of cells at seeding and number of hours between medium replacement) successfully correlated the amount of medium available to each cell averaged over time to neuronal cell differentiation. MF smaller than 8.3×10(4) µm3/cell⋅hour produced significant neuronal cell differentiation marked by cell morphological change and significantly more cells with positive β-tubulin-III and MAP2 staining than the control. When MF was equal or greater than 8.3×10(4) µm3/cell⋅hour, minimal spontaneous neuronal cell differentiation happened relative to the control. MF had minimal relation with the average neurite length.

SIGNIFICANCE

MFs can be controlled easily to maintain the stem cell status of C17.2 NSCs or to induce spontaneous neuronal cell differentiation in standard stem cell culture medium. This finding is useful in designing microfluidic culture platforms for controllable NSC maintenance and differentiation. This study also offers insight about consumption rate of serum molecules involved in maintaining the stemness of NSCs.

A ginkgo biloba extract promotes proliferation of endogenous neural stem cells in vascular dementia rats

The ginkgo biloba extract EGb761 improves memory loss and cognitive impairments in patients with senile dementia. It also promotes proliferation of neural stem cells in the subventricular zone in Parkinson's disease model mice and in the hippocampal zone of young epileptic rats. However, it remains unclear whether EGb761 enhances proliferation of endogenous neural stem cells in the brain of rats with vascular dementia. In this study, a vascular dementia model was established by repeatedly clipping and reperfusing the bilateral common carotid arteries of rats in combination with an intraperitoneal injection of a sodium nitroprusside solution. Seven days after establishing the model, rats were intragastrically given EGb761 at 50 mg/kg per day. Learning and memory abilities were assessed using the Morris water maze and proliferation of endogenous neural stem cells in the subventricular zone and dentate gyrus were labeled by 5-bromo-2-deoxyuridine immunofluorescence in all rats at 15 days, and 1, 2, and 4 months after model establishment. The escape latencies in Morris water maze tests of rats with vascular dementia after EGb761 treatment were significantly shorter than the model group. Immunofluorescence staining showed that the number and proliferation of 5-bromo-2-deoxyuridine-positive cells in the subventricular zone and dentate gyrus of the EGb761-treated group were significantly higher than in the model group. These experimental findings suggest that EGb761 enhances proliferation of neural stem cells in the subventricular zone and dentate gyrus, and significantly improves learning and memory in rats with vascular dementia.

Buyang Huanwu Decoction regulates neural stem cell behavior in ischemic brain

The traditional Chinese medicine Buyang Huanwu Decoction has been shown to improve the neu-rological function of patients with stroke. However, the precise mechanisms underlying its effect remain poorly understood. In this study, we established a rat model of cerebral ischemia by middle cerebral artery occlusion and intragastrically administered 5 g/kg Buyang Huanwu Decoction, once per day, for 1, 7, 14 and 28 days after cerebral ischemia. Immunohistochemical staining revealed a number of cells positive for the neural stem cell marker nestin in the cerebral cortex, the subven-tricular zone and the ipsilateral hippocampal dentate gyrus in rat models of cerebral ischemia. Buyang Huanwu Decoction significantly increased the number of cells positive for 5-bromodeoxyuridine (BrdU), a cell proliferation-related marker, microtubule-associated protein-2, a marker of neuronal differentiation, and growth-associated protein 43, a marker of synaptic plasticity in the ischemic rat cerebral regions. The number of positive cells peaked at 14 and 28 days after intragastric administration of Buyang Huanwu Decoction. These findings suggest that Buyang Huanwu Decoction can promote the proliferation and differentiation of neural stem cells and hance synaptic plasticity in ischemic rat brain tissue.

Daucosterol promotes the proliferation of neural stem cells

Neural stem cells (NSCs) are self-regenerating cells, but their regenerative capacity is limited. The present study was conducted to investigate the effect of daucosterol (a sterolin) on the promotion of NSC proliferation and determine the corresponding molecular mechanism. Results of cell counting kit-8 (CCK-8) assay showed that daucosterol significantly increased the quantity of viable cells and the effectiveness of daucosterol was similar to that of basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF). Flow cytometry detection of CFSE-labeled (CFSE, carboxyfluorescein diacetate succinimidyl ester) NSCs showed that Div Index (or the average number of cell divisions) and % Divided (or the percentage of cells that divided at least once) of the cells were increased, indicating that daucosterol increased the percentage of NSCs re-entering the cell cycle. mRNA microarray analysis showed that 333 genes that are mostly involved in the mitotic cell cycle were up-regulated. By contrast, 627 genes that are mostly involved in differentiation were down-regulated. In particular, insulin-like growth factor I (IGF1) was considered as an important regulatory gene that functionally promoted NSC proliferation, and the increased expression of IGF1 protein was validated by ELISA. In addition, the phosphorylation of AKT was increased, indicating that the proliferation-enhancing activity of daucosterol may be involved in IGF1-AKT pathway. Our study provided information about daucosterol as an efficient and inexpensive growth factor alternative that could be used in clinical medicine and research applications.

Electroacupuncture promotes post-stroke functional recovery via enhancing endogenous neurogenesis in mouse focal cerebral ischemia

To investigate the question of whether electroacupuncture (EA) promotes functional recovery via enhancement of proliferation and differentiation of neuronal stem cells (NSCs) in ischemic stroke, EA stimulation with 2 Hz was applied at bilateral acupoints to Baihui (GV20) and Dazhui (GV14) in middle cerebral artery occlusion (MCAO) mice. EA stimulation improved neuromotor function and cognitive ability after ischemic stroke. EA stimulation resulted in an increase in the number of proliferated cells, especially in the subventricular zone (SVZ) of the ipsilateral hemisphere. Although a very limited number of NSCs survived and differentiated into neurons or astrocytes, EA treatment resulted in a significant increase in the number of proliferative cells and differentiated cells in the hippocampus and SVZ of the ipsilateral hemisphere compared to MCAO mice. EA stimulation resulted in significantly increased mRNA expression of brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF). Protein levels of these factors were confirmed in the ipsilateral hippocampus and SVZ by immunohistochemical and Western blotting analyses. Expression of phosphorylated phosphatidylinositol-3-kinase, BDNF, and VEGF-mediated down-stream were enhanced by EA stimulation in newly formed neuroblasts. These results indicate that EA treatment after ischemic stroke may promote post-stroke functional recovery by enhancement of proliferation and differentiation of NSCs via the BDNF and VEGF signaling pathway.

Microarray Analysis of mRNA and MicroRNA Expression Profile Reveals the Role of β -Sitosterol-D-glucoside in the Proliferation of Neural Stem Cell

Neural stem cells (NSCs) are self-regenerating cells, but their regenerative capacity is limited. The present study was conducted to investigate the effect of β-sitosterol-D-glucoside (BSSG) on the proliferation of hippocampal NSCs and to determine the corresponding molecular mechanism. Results of CCK-8 assay showed that BSSG significantly increased NSC proliferation and the effectiveness of BSSG was similar to that of basic fibroblast growth factor and epidermal growth factor. mRNA expression profiling showed that 960 genes were differentially expressed after NSCs were treated with BSSG. Among the 960 genes, IGF1 is considered as a key regulatory gene that functionally promotes NSC proliferation. MicroRNA (miRNA) expression profiling indicated that 30 and 84 miRNAs were upregulated and downregulated, respectively. miRNA-mRNA relevance analysis revealed that numerous mRNAs including IGF1 mRNA were negatively regulated by miRNAs with decreased expression, thereby increasing the corresponding mRNA expression. The increased expression of IGF1 protein was validated by ELISA. Picropodophyllin (PPP, an inhibitor of IGF-1R) inhibition test confirmed that the proliferation-enhancing effect depended on IGF1. This study provided information about BSSG as an efficient and inexpensive growth factor alternative, of which the effect is closely involved in IGF1.

MicroRNAs in cerebral ischemia-induced neurogenesis

Cerebral ischemia induces neurogenesis, including proliferation and differentiation of neural progenitor cells and migration of newly generated neuroblasts. MicroRNAs (miRNAs) are small noncoding RNAs that decrease gene expression through mRNA destabilization and/or translational repression. Emerging data indicate that miRNAs have a role in mediating processes of proliferation and differentiation of adult neural progenitor cells. This article reviews recent findings on miRNA profile changes in neural progenitor cells after cerebral infarction and the contributions of miRNAs to their ischemia-induced proliferation and differentiation. We highlight interactions between the miR-124 and the miR17-92 cluster and the Notch and Sonic hedgehog signaling pathways in mediating stroke-induced neurogenesis.

Temporal profile of neural stem cell proliferation in the subventricular zone after ischemia/hypoxia in the neonatal rat brain

OBJECTIVES

Ischemia/hypoxia (I/H) causes severe neonatal brain injury, such as periventricular leukomaracia and hypoxic/ischemic encephalopathy. Neural stem cell research could lead to a treatment for such disorders. In order to elucidate the dynamic changes in neural stem cells in the neonatal brain after I/H, we investigated the proliferation of new cells in the subventricular zone (SVZ).

METHODS

Seven-day-old Wister rats were subjected to ligation of the left carotid artery followed by 2 hours of hypoxic stress (8% O(2) and 92% N(2), at 33 degrees C). In order to elucidate the dynamic change of neural stem cells in the SVZ, single bromodeoxyuridine (BrdU; 50 mg/kg) was administered 2 hours before death 1, 7, 14 and 21 days after I/H. Immunohistochemical and immunofluorescent studies for BrdU and doublecortin (DCX) were carried out. As a control, a group of rats was subjected to sham surgery (incision of skin, but no ligation of the carotid artery) and no I/H.

RESULTS

The numbers of BrdU-labeled cells in the SVZ, for both the ipsilateral side and the contralateral side of the I/H brain, were twice the level of the control at 7 days after I/H, but the numbers for both sides returned to the control level at 21 days. In the ipsilateral side of the I/H brain, the number of BrdU-labeled cells in the SVZb (lining the upper wall of lateral ventricle) was 4-fold at 7 days and 15-fold at 21 days after I/H compared with the control level. This chronological pattern is very similar to the pattern for I/H results of the posterior periventricle (pPV). DCX appeared in most BrdU-labeled cells in the SVZb and pPV.

DISCUSSION

These findings indicate that I/H enhances neural stem cell proliferation in the SVZ, and some newborn cells migrate as neural precursors to the SVZb and pPV after I/H in the neonatal rat brain.

Acute inflammation alters adult hippocampal neurogenesis in a multiple sclerosis mouse model

Neural precursor cells (NPCs) located in the subgranular zone (SGZ) of the dentate gyrus (DG) give rise to thousands of new cells every day, mainly hippocampal neurons, which are integrated into existing neuronal circuits. Aging and chronic degenerative disorders have been shown to impair hippocampal neurogenesis, but the consequence of inflammation is somewhat controversial. The present study demonstrates that the inflammatory environment prevailing in the brain of experimental autoimmune encephalomyelitis (EAE) mice enhances the proliferation of NPCs in SGZ of the dorsal DG and alters the proportion between radial glial cells and newborn neuroblasts. The injection protocol of the cell cycle marker bromodeoxyuridine and the immunohistochemical techniques that were employed revealed that the proliferation of NPCs is increased approximately twofold in the SGZ of the dorsal DG of EAE mice, at the acute phase of the disease. However, although EAE animals exhibited significant higher percentage of newborn radial-glia-like NPCs, the mean percentage of newborn neuroblasts rather was decreased, indicating that the robust NPCs proliferation is not followed by a proportional production of newborn neurons. Significant positive correlations were detected between the number of proliferating cells in the SGZ and the clinical score or degree of brain inflammation of diseased animals. Finally, enhanced neuroproliferation in the acute phase of EAE was not found to trigger compensatory apoptotic mechanisms. The possible causes of altered neurogenesis observed in this study emphasize the need to understand more precisely the mechanisms regulating adult neurogenesis under both normal and pathological conditions.

[iPS cell transplantation for ischemic brain]

Stroke is a major neurologic disorder. Induced pluripotent stem (iPS) cells can be produced from basically any part of patients, with high reproduction ability and pluripotency to differentiate into various types of cells, suggesting that iPS cells can provide a hopeful therapy for cell transplantation. However, transplantation of iPS cells into ischemic brain has not been reported. In this study, we showed that the iPS cells fate in a mouse model of transient middle cerebral artery occlusion (MCAO). Undifferentiated iPS cells (5×10(5)) were transplanted into ipsilateral striatum and cortex at 24 h after 30 mins of transient MCAO. Behavioral and histologic analyses were performed at 28 day after the cell transplantation. To our surprise, the transplanted iPS cells expanded and formed much larger tumors in mice postischemic brain than in sham-operated brain. The clinical recovery of the MCAO+iPS group was delayed as compared with the MCAO+PBS (phosphate-buffered saline) group. iPS cells formed tridermal teratoma, but could supply a great number of Dcx-positive neuroblasts and a few mature neurons in the ischemic lesion. iPS cells have a promising potential to provide neural cells after ischemic brain injury, if tumorigenesis is properly controlled.

Stem cell therapy for cerebral ischemia: from basic science to clinical applications

Recent stem cell technology provides a strong therapeutic potential not only for acute ischemic stroke but also for chronic progressive neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis with neuroregenerative neural cell replenishment and replacement. In addition to resident neural stem cell activation in the brain by neurotrophic factors, bone marrow stem cells (BMSCs) can be mobilized by granulocyte-colony stimulating factor for homing into the brain for both neurorepair and neuroregeneration in acute stroke and neurodegenerative diseases in both basic science and clinical settings. Exogenous stem cell transplantation is also emerging into a clinical scene from bench side experiments. Early clinical trials of intravenous transplantation of autologous BMSCs are showing safe and effective results in stroke patients. Further basic sciences of stem cell therapy on a neurovascular unit and neuroregeneration, and further clinical advancements on scaffold technology for supporting stem cells and stem cell tracking technology such as magnetic resonance imaging, single photon emission tomography or optical imaging with near-infrared could allow stem cell therapy to be applied in daily clinical applications in the near future.

Potential treatment strategies for enhancing neuroplasticity and regeneration after ischemic stroke

Strokes are a major cause of death and result in a drastic reduction in quality of life. Novel therapeutic strategies for patients suffering from stroke are thus required. Two possible strategies can be proposed for treating ischemic stroke: enhancing neuroplasticity, allowing the surviving neuronal cells to compensate for stroke-related impairment through brain reorganization, sprouting and rewiring of neuronal cells, or regeneration of neuronal cells, including enhancement of intrinsic neurogenesis and stem cell transplantation therapy with neural stem cells, embryonic stem cells or induced pluripotent stem cells. Endogenous neurogenesis or transplanted neural stem cells, embryonic stem cells or induced pluripotent stem cell-derived cells are able to not only supply newborn neurons integrated into a damaged neuronal network, but also produce growth factors into the recovering brains. These secretory factors enhance sprouting and angiogenesis and may be important in neuroplasticity and recovery in the poststroke brain.

Comparison of neurogenesis in the dentate gyrus between the adult and aged gerbil following transient global cerebral ischemia

In the present study, we compared differences in cell proliferation, neuroblast differentiation and neuronal maturation in the hippocampal dentate gyrus (DG) between the adult and aged gerbil induced by 5 min of transient global cerebral ischemia using Ki-67 and BrdU (markers for cell proliferation), doublecortin (DCX, a marker for neuroblast differentiation) and neuronal nuclei (NeuN, a marker for mature neuron). The number of Ki-67-immunoreactive (⁺) cells in the DG of both the groups peaked 7 days after ischemia/reperfusion (I/R). However, the number in the aged DG was 40.6 ± 1.8% of that in the adult DG. Thereafter, the number decreased with time. After ischemic damage, DCX immunoreactivity and its protein level in the adult and aged DG peaked at 10 and 15 days post-ischemia, respectively. However, DCX immunoreactivity and its protein levels in the aged DG were much lower than those in the adult. DCX immunoreactivity and its protein level in the aged DG were 11.1 ± 0.6% and 34.4 ± 2.1% of the adult DG, respectively. In addition, the number of Ki-67⁺ cells and DCX immunoreactivity in both groups were similar to those in the sham at 60 days postischemia. At 30 days post-ischemia, the number of BrdU⁺ cells and BrdU⁺/NeuN⁺ cells in the adult-group were much higher (281.2 ± 23.4% and 126.4 ± 7.4%, respectively) than the aged-group (35.6 ± 6.8% and 79.5 ± 6.1%, respectively). These results suggest that the ability of neurogenesis in the ischemic aged DG is much lower than that in the ischemic adult DG.

Neuroprotective and Angiogenic Effects of Bone Marrow Transplantation Combined With Granulocyte Colony-Stimulating Factor in a Mouse Model of Amyotrophic Lateral Sclerosis

Bone marrow (BM) cells from amyotrophic lateral sclerosis (ALS) patients show significantly reduced expression of several neurotrophic factors. Monotherapy with either wild-type (WT) BM transplantation (BMT) or granulocyte colony-stimulating factor (GCSF) has only a small clinical therapeutic effect in an ALS mouse model, due to the phenomenon of neuroprotection. In this study, we investigated the clinical benefits of combination therapy using BMT with WT BM cells, plus GCSF after disease onset in ALS mice [transgenic mice expressing human Cu/Zn superoxide dismutase (SOD1) bearing a G93A mutation]. Combined treatment with BMT and GCSF delayed disease progression and prolonged the survival of G93A mice, whereas BMT or GCSF treatment alone did not. Histological study of the ventral horns of lumbar cords from G93A mice treated with BMT and GCSF showed a reduction in motor neuron loss coupled with induced neuronal precursor cell proliferation, increased expression of neurotrophic factors (glial cell line-derived neurotrophic factor, brain-derived neurotrophic factor, vascular endothelial growth factor and angiogenin), and neovascularization compared with controls (vehicle only). Compared with G93A microglial cells, most BM-derived WT cells differentiated into microglial cells and strongly expressed neurotrophic factors, combined BMT and GCSF treatment led to the replacement of G93A microglial cells with BM-derived WT cells. These results indicate combined treatment with BMT and GCSF has potential neuroprotective and angiogenic effects in ALS mice, induced by the replacement of G93A microglial cells with BM-derived WT cells. Furthermore, this is the first report showing the effects of combined BMT and GCSF treatment on blood vessels in ALS.

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.

Relation among neuronal death, cell proliferation and neuronal differentiation in the gerbil main olfactory bulb after transient cerebral ischemia

Neurogenesis occurs during the embryonic stage and throughout life. Brain injuries such as ischemic insults enhance cell proliferation in some areas of the brain. We examined proliferation of newly generated cells in each layer of the gerbil main olfactory bulb (MOB) after 5 min of transient cerebral ischemia using bromodeoxyuridine (BrdU) immunohistochemistry. Ischemia-related neuronal death in the MOB was not detected using Fluoro-Jade B histofluorescence and TUNEL staining. Many BrdU-positive ((+)) cells were found in the rostral migratory stream in control and ischemic MOBs. Significant increase of BrdU(+) cells was observed in the granule cell layer (GCL) and glomerular layer (GL) from 15 days post-ischemia, and BrdU(+) cells were very much higher than those of the control group 30 days post-ischemia. At this time point after ischemia/reperfusion, a few BrdU(+) cells in the GL and GCL were co-localized with calretinin(+) cells, and many BrdU(+) cells expressed doublecortin, a marker of immature neurons. These results indicate that cell proliferation is increased in the GCL and GL without apparent neuronal loss from 15 days after transient cerebral ischemia in gerbils.

Enhanced expression of SOCS-2 in the rat hippocampus after transient forebrain ischemia

Suppressor of cytokine signaling-2 (SOCS-2) has recently been identified as an important regulator involved in neuronal differentiation and maturation. However, the role of SOCS-2 in ischemia-induced hippocampal neurogenesis remains to be clarified. Here we investigated the spatiotemporal expression of SOCS-2 in the rat hippocampus following transient forebrain ischemia, and particular attention was paid to changes in the dentate gyrus. SOCS-2 mRNA was constitutively expressed in hippocampal neurons and astrocytes in control animals. However, its upregulation occurred specifically in reactive astrocytes in the hippocampus proper, in particular the CA1 and dentate hilar regions, at day 3 after reperfusion, and was sustained for more than 2 weeks. In addition to the CA1 and hilar regions, SOCS-2 was transiently increased in the subgranular zone (SGZ) of the dentate gyrus on days 3-7 after reperfusion. This correlated with the post-ischemic upregulation of SOCS-2 in the CA1 or dentate gyrus subfield, including the SGZ detected by semiquantitative reverse transcriptase-polymerase chain reaction analysis. The majority of the SOCS-2-expressing cells in the SGZ were co-labeled with glial fibrillary acidic protein (GFAP), and a subpopulation of GFAP/SOCS-2 double-labeled cells in the SGZ co-expressed the neural progenitor marker nestin, or the proliferation marker proliferating cellular nuclear antigen. In addition, a subset of SOCS-2-labeled cells in the SGZ expressed the immature neuronal marker polysialic acid-neural cell adhesion molecule. These data suggest that SOCS-2 may be involved in glial reactions, and possibly adult hippocampal neurogenesis during ischemic insults.

Brain plasticity after ischemic episode

Brain plasticity describes the potential of the organ for adaptive changes involved in various phenomena in health and disease. A substantial amount of experimental evidence, received in animal and cell models, shows that a cascade of plastic changes at the molecular, cellular, and tissue levels, is initiated in different regions of the postischemic brain. Underlying mechanisms include neurochemical alterations, functional changes in excitatory and inhibitory synapses, axonal and dendritic sprouting, and reorganization of sensory and motor central maps. Multiple lines of evidence indicate numerous points in which the process of postischemic recovery may be influenced with the aim to restore the full capacity of the brain tissue injured by an ischemic episode.

Inflammation mediates varying effects in neurogenesis: relevance to the pathogenesis of brain injury and neurodegenerative disorders

Brain inflammation is a complex cellular and molecular response to stress, injury or infection of the CNS in attempt to defend against insults, clear dead and damaged neurons and return the CNS to a normal state. Inflammation in the CNS is driven by the activation of resident microglia, astrocytes and infiltrating peripheral macrophages, which release a plethora of anti- and pro-inflammatory cytokines, chemokines, neurotransmitters and reactive oxygen species. This inflammatory state inadvertently causes further bystander damage to neurons and produces both detrimental and favorable conditions for neurogenesis. Inflammatory factors have varying effects on neural progenitor cell proliferation, migration, differentiation, survival and incorporation of newly born neurons into the CNS circuitry. The unique profile of inflammatory factors, which depends on the severity of inflammation, can have varying consequences on neurogenesis. Inflammatory factors released during mild acute inflammation usually stimulate neurogenesis; where as the factors released by uncontrolled inflammation create an environment that is detrimental to neurogenesis. This review will provide a summary of current progress in this emerging field and examine the potential mechanisms through which inflammation affects neurogenesis during neurological complications.

Temporal profile of neurogenesis in the subventricular zone, dentate gyrus and cerebral cortex following transient focal cerebral ischemia

BACKGROUND

In the adult mammalian brain, it is considered that neurogenesis persists in limited regions such as the hippocampal dentate gyrus (DG) and the subventricular zone (SVZ) of the lateral ventricle. On the other hand, neurogenesis in the cortex after cerebral ischemia and its role in post-stroke recovery have not been clarified yet. In this study, we investigated neurogenesis in the cortex and the spatiotemporal profile of neural progenitors in SVZ and DG of rats subjected to transient focal cerebral ischemia.

MATERIALS AND METHODS

Male Sprague-Dawley rats (270-300 g) were subjected to 60 minute middle cerebral artery occlusion. Proliferating cells were labeled by the cumulative administration of BrdU 1, 2, 3, 4, 6 and 8 weeks after ischemia induction (at weeks 1-4, 6 and 8). Double labeling was also performed with antibodies against BrdU and NeuN.

RESULTS

BrdU-positive cells proliferated in DG and SVZ of the bilateral hemispheres, and their proliferation peaked at week 3 in SVZ and at week 4 in DG. In the peri-infarct zone of cerebral cortex, BrdU-positive cells co-expressed NeuN from weeks 3 to 8.

CONCLUSION

Neurogenesis was observed in the cerebral cortex and proliferation of neural progenitors occurred in SVZ and DG of rats subjected to transient focal cerebral ischemia. Our data might indicate that endogenous dormant neural stem cells residing in the cortex were activated by ischemic insult to induce the proliferation of neural progenitors and differentiation into mature neurons.

Ischemic stroke and neurogenesis in the subventricular zone

The subventricular zone (SVZ) of the lateral ventricle contains neural stem and progenitor cells that generate neuroblasts, which migrate to the olfactory bulb where they differentiate into interneurons. Ischemic stroke induces neurogenesis in the SVZ and these cells migrate to the boundary of the ischemic lesion. This article reviews current data on cytokinetics, signaling pathways and vascular niche that are involved in processes of proliferation, differentiation, and migration of neural progenitor cells after stroke.

Therapeutic window of hyperbaric oxygen therapy for hypoxic-ischemic brain damage in newborn rats

Previous studies showed that hyperbaric oxygen (HBO) promoted cell proliferation in hypoxic-ischemic (HI) neonate rats. Neural stem cells (NSC) existed in the brain lifelong and can be activated. This study was undertaken to assess whether HBO treatment promoted the proliferation of NSC and repaired the brain damage regardless of when it is started, thus to explore the therapeutic window of HBO treatment. Seven-day-old Sprague-Dawley rats underwent left carotid ligation followed by 2 h of hypoxic stress (8% O(2) at 37 degrees C). Hyperbaric oxygen therapy was administered 3, 6, 12, 24, and 72 h after HI. 5-bromo-2'-deoxyurindine and 5-bromo-2'-deoxyuridine/nestin were detected by immunofluorescence and nestin was examined by western blot analysis 10 days after HI. T-maze forced alternation, the foot-fault test, and the radial arm maze were conducted at P 22 days (14 days after HI), P 30 days, and P 34 days. Thereafter, cerebral morphology was examined by Nissl-staining 28 days after HI. There were remarkable increases in the proliferation of neural stem cells in the HBO-treated group, 3, 6, 12, and 24 h after HI, as compared with the HIBD group. The HBO-treated group, 3, 6, and 12 h after HI, performed better in the behavioral test and had less neural loss in the hippocampal CA1 region as compared with the HIBD group. The therapeutic window for effective HBO treatment could be delayed up to 12 h after HIBD, while the effect decreased 24 h after HI.

Stem cells and neonatal brain injury

Recent advances in regenerative medicine and in our understanding of neurogenesis may lead to new ways of recovering neuronal function lost or damaged during the perinatal period; such injuries are not amenable to conventional therapies. We review recent experimental studies based on immature rodental models of neonatal brain injury, especially hypoxic-ischemic encephalopathy. The developing brain is revealed to have considerable potential with respect to proliferation and migration to the injured site. However, the generation of fully differentiated neurons is extremely limited after brain injuries. Aggressive efforts to adjust the environment of the damaged brain in which tissue regeneration is occurring or more cautious stem cell transplantation will be required for the successful treatment of developmental brain injury.

Erythropoietin Promotes Neuronal Replacement Through Revascularization and Neurogenesis After Neonatal Hypoxia/Ischemia in Rats

BACKGROUND AND PURPOSE

Erythropoietin (EPO) has been well characterized and shown to improve functional outcomes after ischemic injury, but EPO may also have unexplored effects on neurovascular remodeling and neuronal replacement in the neonatal ischemic brain. The current study investigates the effects of exogenous administration of EPO on revascularization and neurogenesis, 2 major events thought to contribute to neuronal replacement, in the neonatal brain after hypoxia/ischemia (H/I).

METHODS

Seven-day-old rat pups were treated with recombinant human EPO or vehicle 20 minutes after H/I and again on postischemic days 2, 4, and 6. Rats were euthanized 7 or 28 days after H/I for evaluation of infarct volume, revascularization, neurogenesis, and neuronal replacement using bromodeoxyuridine incorporation, immunohistochemistry, and lectin labeling. Neurological function was assessed progressively for 28 days after H/I by gait testing, righting reflex and foot fault testing.

RESULTS

We demonstrate that exogenous EPO-enhanced revascularization in the ischemic hemisphere correlated with decreased infarct volume and improved neurological outcomes after H/I. In addition to vascular effects, EPO increased both neurogenesis in the subventricular zone and migration of neuronal progenitors into the ischemic cortex and striatum. A significant number of newly synthesized cells in the ischemic boundary expressed neuronal nuclei after EPO treatment, indicating that exogenous EPO led to neuronal replacement.

CONCLUSIONS

Our data suggest that treatment with EPO contributes to neurovascular remodeling after H/I by promoting tissue protection, revascularization, and neurogenesis in neonatal H/I-injured brain, leading to improved neurobehavioral outcomes.

G-CSF enhances stem cell proliferation in rat hippocampus after transient middle cerebral artery occlusion

Granulocyte colony-stimulating factor (G-CSF) enhances the survival and stimulates the proliferation of neutrophil progenitors. Recently, the neurogenerative effect of G-CSF has been intensely investigated. In this study, we explored the possibility that G-CSF enhanced the cell proliferation in the rat dentate gyrus (DG) after focal cerebral ischemia, using a rat transient middle cerebral artery occlusion (tMCAO) model. At 7 days after tMCAO, the number of 5-bromodeoxyuridine (BrdU)-positive cells in the G-CSF-treated group was significantly increased compared with that in the vehicle-treated group in the ipsilateral SGZ (16.6+/-5.5/mm(2) in the vehicle-treated group versus 33.0+/-7.2/mm(2) in the G-CSF-treated group, **p<0.01) and in the ipsilateral GCL (14.2+/-2.8/mm(2) in the vehicle-treated group versus 21.0+/-3.8/mm(2) in the G-CSF-treated group, *p<0.05). This result showed the possibility of a neurogenerative role of G-CSF after tMCAO in rats.