Rat Hippocampal Neural Stem Cells Research Articles

Plant Cellulose as a Substrate for 3D Neural Stem Cell Culture.

Neural stem cell (NSC)-based therapies are at the forefront of regenerative medicine strategies for various neural defects and injuries such as stroke, traumatic brain injury, and spinal cord injury. For several clinical applications, NSC therapies require biocompatible scaffolds to support cell survival and to direct differentiation. Here, we investigate decellularized plant tissue as a novel scaffold for three-dimensional (3D), in vitro culture of NSCs. Plant cellulose scaffolds were shown to support the attachment and proliferation of adult rat hippocampal neural stem cells (NSCs). Further, NSCs differentiated on the cellulose scaffold had significant increases in their expression of neuron-specific beta-III tubulin and glial fibrillary acidic protein compared to 2D culture on a polystyrene plate, indicating that the scaffold may enhance the differentiation of NSCs towards astrocytic and neuronal lineages. Our findings suggest that plant-derived cellulose scaffolds have the potential to be used in neural tissue engineering and can be harnessed to direct the differentiation of NSCs.

Protective effect of metformin on methotrexate induced reduction of rat hippocampal neural stem cells and neurogenesis

Adult neurogenesis is a process in which the adult neural stem cells produce newborn neurons that are implicated in terms of learning and memory. Methotrexate (MTX) is a chemotherapeutic drug, which has a negative effect on memory and hippocampal neurogenesis in animal models. Metformin is an antidiabetic drug with strong antioxidant capacities. We found that metformin ameliorates MTX induced deteriorations of memory and hippocampal neurogenesis in adult rats. In this study, we focus to investigate neural stem cells, biomarkers of apoptosis, and the protein for synaptogenesis, which involves in the transcription factors of the hippocampus in rats that received metformin and MTX. Male Sprague-Dawley rats were composed of control, MTX, metformin, and MTX+metformin groups. MTX (75 mg/kg, i.v.) was given on days 7 and 14, whereas metformin (200 mg/kg, i.p.) was given for 14 days. Hippocampal neural stem cells in the subgranular zone (SGZ) were quantified using immunofluorescence staining of Sox2 and nestin. Protein expression including PSD95, Casepase-3, Bax, Bcl-2, CREB, and pCREB were determined using Western blotting. MTX-treated rats displayed decreases in Sox2 and nestin-positive cells in the SGZ. Increases in Caspase-3 and Bax levels and decreases in PSD95, Bcl-2, CREB, and pCREB protein expressions in the hippocampus were also detected. However, these negative impacts of MTX were ameliorated by co-treatment with metformin. These consequences postulate that metformin has a potential to increase neural stem cells, synaptic plasticity, decreased apoptotic activities, and transcription factors, resulting in upregulation of hippocampal neurogenesis in MTX-treated rats.

Effects of Subchronic Propofol Administration on the Proliferation and Differentiation of Neural Stem Cells in Rat Hippocampus

Although controversial, experimental data suggest the use of propofol may be associated with neurotoxicity. The mechanisms responsible for propofol neurotoxicity in animals are not yet clear. This study aimed to determine the effects of propofol on the proliferation of neural stem cells in rat hippocampus and the mechanisms underlying these effects. Forty-five adult male Sprague-Dawley rats were randomly divided into 5 groups: Control (N group), intralipid (V group), 30 mg/kg propofol (Prop30 group), 60 mg/kg propofol (Prop60 group), and 120 mg/kg propofol (Prop120 group). The rats in all groups received 5, once daily intraperitoneal injections. For each of the 5 days, the N group received 6 mL/kg normal saline, the V group received 6 mL/kg fat emulsion, the Prop30 group received 30 mg/kg propofol, the Prop60 group received 60 mg/kg propofol, and the Prop120 group received 120 mg/kg propofol. Memory function was scored daily using the Morris water maze test. Immunofluorescence staining was used to histologically monitor the proliferation and differentiation of the rats' hippocampal neural stem cells, and real time quantitative polymerase chain reaction and Western blotting were used to determine the expression of Notch3, Hes1, and Hes5. Compared with the N group, the Prop120 group exhibited reduced learning and memory, whereas there were no significant differences for the Prop60 group. The number of β-tubulin III+ cells increased in the Prop60 group, but decreased in the Prop120 group. Compared with the N group, the relative expression of Notch3 and Hes5 increased significantly in the Prop60 group, whereas this expression decreased in the Prop120 group. These data demonstrate that repeated, subchronic (5 days) intraperitoneal injections of 60 mg/kg propofol can effectively promote rat hippocampal neural stem cells proliferation and differentiation, and that this is likely mediated by its effects on the Notch3-Hes5 pathway.

20-Hydroxyecdysone Improves Neuronal Differentiation of Adult Hippocampal Neural Stem Cells in High Power Microwave Radiation-Exposed Rats

ObjectiveThe hippocampus is thought to be a vulnerable target of microwave exposure. The aim of the present study was to investigate whether 20-hydroxyecdysone (20E) acted as a fate regulator of adult rat hippocampal neural stem cells (NSCs). Furthermore, we investigated if 20E attenuated high power microwave (HMP) radiation-induced learning and memory deficits. MethodsSixty male Sprague-Dawley rats were randomly divided into three groups: normal controls, radiation treated, and radiation+20E treated. Rats in the radiation and radiation+20E treatment groups were exposed to HPM radiation from a microwave emission system. The learning and memory abilities of the rats were assessed using the Morris water maze test. Primary adult rat hippocampal NSCs were isolated in vitro and cultured to evaluate their proliferation and differentiation. In addition, hematoxylin & eosin staining, western blotting, and immunofluorescence were used to detect changes in the rat brain and the proliferation and differentiation of the adult rat hippocampal NSCs after HPM radiation exposure. ResultsThe results showed that 20E induced neuronal differentiation of adult hippocampal NSCs from HPM radiation-exposed rats via the Wnt3a/β-catenin signaling pathway in vitro. Furthermore, 20E facilitated neurogenesis in the subgranular zone of the rat brain following HPM radiation exposure. Administration of 20E attenuated learning and memory deficits in HPM radiation-exposed rats and frizzled-related protein (FRZB) reduced the 20E-induced nuclear translocation of β-catenin, while FRZB treatment also reversed 20E-induced neuronal differentiation of NSCs in vitro. ConclusionThese results suggested that 20E was a fate regulator of adult rat hippocampal NSCs, where it played a role in attenuating HPM radiation-induced learning and memory deficits.

Treating hippocampal neural stem cells with nano‐pulsed laser therapy generates neurons with decreased sensitivity to toxic Aβ oligomers

Synaptic dysfunction driven by toxic amyloid oligomers (Abo and Tauo) is an early event leading to cognitive decline in Alzheimer's disease (AD). We have shown that transcranial treatment of adult wt mice with near-infrared light decreases synaptic vulnerability to Aβo. We have also shown that preserved neurogenesis correlates with synaptic resilience and preserved cognitive function in non-demented individuals with AD neuropathology. Here we sought to determine whether treating hippocampal neural stem cells (NSCs), the primary source of neurogenesis in the adult brain, with Nano-Pulsed Laser Therapy (NPLT), combining near-infrared light irradiation (808nm) with ultrasonic optoacoustic waves, could lead to the generation of neurons with decreased synaptic vulnerability to Aβo toxicity.Adult rat hippocampal NSCs were treated for five minutes with NPLT (10ms pulse duration, 20Hz pulse frequency, 4.3mJ total energy) or sham treatment and allowed to differentiate into mature neurons (MN) for five days. For analysis of Abo binding, MNs were exposed to 2.5µM Fluor-647-labeled Aβo for 30 minutes at 37⁰C and immunostained for βIII-tubulin. The number of Aβo puncta on neurites was quantified using ImageJ. For analysis of mitochondrial function, Aβo-treated MNs were incubated with the mitochondrial membrane potential-dependent dye, MitoTracker Deep Red (MTDR) and potential-independent MitoTracker Green (MTG). Flow cytometric analyses of MTDR (healthy mitochondria) and MTG (total mitochondria) was conducted at 30 minutes post-Aβo treatment.MNs generated from NPLT-treated NSCs showed significantly fewer Aβo puncta per neurite compared to MNs from sham-treated NSCs (p=0.0049), and lower percentage of total neurites with bound Aβo (p<0.0001) (Figure 1). We also found that Aβo treatment induced a significant reduction in both total mitochondria and mitochondrial membrane potential in MNs from sham-treated NSCs but not in MNs from NPLT-treated NSCs (Figure 2).Here we show that NSCs treated with NPLT generate MNs resistant to Aβo binding and to Ab-induced mitochondrial dysfunction. These data suggest that NPLT, which is currently approved for use in humans for unrelated clinical applications, could be a valuable therapeutic tool for inducing cognitive resilience to AD neuropathology.

In vitro investigation of growth factors including MGF and IGF-1 in neural stem cell activation, proliferation, and migration

Neurogenesis is mainly activated after damage in adult tissues. This destruction activates the neural stem cells (NSCs) by exiting from a quiescent state and initiating proliferation, differentiation, and migration towards the damaged area. Although studies have investigated to clarify the process of NSC biology and neurogenesis, there are still significant artifacts in understanding the primary mechanism. It is known that only a small percentage of NSC become neurons and integrate into the brain tissue after this process. The significant proportion differentiates to become either astrocytes or oligodendrocytes. Furthermore, the quiescent stem cells in the niche are mainly activated by the stimuli affect. In recent years, many studies have been conducted with varying hormones, some of which might provide neuro-stimulation effect and/or involved in the regeneration of the brain tissue and/or neuroprotection from traumatic or ischemic pathologies, including Insulin-like growth factor 1 (IGF-1), Mechano Growth Factor (MGF), Basic Fibroblast Growth Factor (FGF-2), Erythropoietin (EPO), Epidermal Growth Factor (EGF), Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF).In this study, we examined the effects of FGF-2, MGF, IGF-1, EPO, EGF, NGF, and BDNF alone or with various combinations on rat hippocampal NSC by tracking the changes in the expression of Nestin, GFAP, TUBB3, and DCX genes during 24 h (h), 72 h and 168 h time frame. The apoptosis analysis revealed that FGF-2 and FGF-2 coupled growth factors effectively protect NSCs against apoptosis, whereas MGF coupled growth factors failed in this protection. The cell cycle analysis demonstrated that these growth factors had accumulated the NSCs exit from the quiescent phase to the Mitosis phase, mostly without being long in the Synthesis Phase. Neurosphere sizes were increased with MGF, signifying MGF being effective in neural progenitor cells. The combined use of MGF with FGF-2 was more effective in postmitotic neurons than MGF alone.We have comparatively demonstrated the effect of cytokines alone and combined administration on activation, proliferation, and migration of NSCs. Although many issues are still waiting to be investigated in adult neurogenesis, neural regeneration, and adult neural stem cell biology, the results provide vital resources to the researchers that are interested in the varying effect of growth factor on NSC.

Gene expression changes induced by valproate in the process of rat hippocampal neural stem cells differentiation.

Valproate (VPA), an effective clinical approved anti-epileptic drug and mood stabilizer, has been believed to induce neuronal differentiation at the expense of inhibiting astrocytic and oligodendrocytic differentiation. Nevertheless, the involving mechanisms of it remain unclear yet. In the present study, we explored the global gene expression changes of fetus rat hippocampal neural stem cells following VPA treatment by high-throughput microarray. We obtained 874 significantly upregulated genes and 258 obviously downregulated genes (fold change > 2 and P < 0.05). Then, we performed gene ontology and pathway analyses of these differentially expressed genes and chose several genes associated with nervous system according to gene ontology analysis to conduct expression analysis to validate the reliability of the array results as well as reveal possible mechanisms of VPA. To get a better comprehension of the differentially regulated genes by VPA, we conducted protein-protein association analysis of these genes, which offered a source for further studies. In addition, we made the overlap between the VPA-downregulated genes and the predicted target genes of VPA-upregulated microRNAs (miRNAs), which were previously demonstrated. These overlapped genes may provide a source to find functional VPA/miRNA/mRNA axes during neuronal differentiation. This study first constructed a comprehensive potential downstream gene map of VPA in the process of neuronal differentiation.

Stimulatory effect of icariin on the proliferation of neural stem cells from rat hippocampus

BackgroundIcariin (ICA), a major ingredient of Epimediumbrevicornum, has various pharmacological activities including central nervous system protective functions such as the improvement of learning and memory function in mice models of Alzheimer’s disease. It has been reported that ICA can promote regeneration of peripheral nerve and functional recovery. The purpose of this study was to investigate the potentiating effect of ICA on the proliferation of rat hippocampal neural stem cells, and explore the possible mechanism involved.MethodsPrimary neural stem cells were prepared from the hippocampus of newly born SD rats, and cells were cultured in special stem cell culture medium. Neural stem cells were confirmed by immunofluorescence detection of nestin, NSE and GFAP expression. The effect of ICA on the growth and proliferation of the neural stem cells was evaluated by 5-ethynyl-2-deoxyuridine (EdU) labeling of proliferating cells, and photomicrographic images of the cultured neural stem cells. Further, the mechanism of ICA-induced cell proliferation of neural stem cells was investigated by analyzing the gene and protein expression of cell cycle related genes cyclin D1 and p21.ResultsThe present study showed that icariin promotes the growth and proliferation of neural stem cells from rat hippocampus in a dose-dependent manner. Incubation of cells with icariin resulted in significant increase in the number of stem cell spheres as well as the increased incorporation of EdU when compared with cells exposed to control vehicle. In addition, it was found that icariin-induced effect on neural stem cells is associated with increased mRNA and protein expression of cell cycle genes cyclin D1 and p21.ConclusionsThis study evidently demonstrates the potentiating effect of ICA on neural stem cell growth and proliferation, which might be mediated through regulation of cell cycle gene and protein expression promoting cell cycle progression.

Ghrelin protects adult rat hippocampal neural stem cells from excessive autophagy during oxygen-glucose deprivation.

Ghrelin functions as a neuroprotective agent and saves neurons from various insults include ischemic injury. However, it remains to be elucidated whether ghrelin protects neuronal cells against ischemic injury-induced excessive autophagy. Autophagy is required for the maintenance of neural stem cell homeostasis. However, regarding autophagic cell death, it is commonly assumed that excessive autophagy leads to self-elimination of mammalian cells. The purpose of this study was to investigate the potential neuroprotection effects of ghrelin from excessive autophagy in adult rat hippocampal neural stem cells (NSCs). Oxygen-Glucose Deprivation (OGD) strongly induces autophagy in adult rat hippocampal NSCs. Ghrelin treatment inhibited OGD-induced cell death of adult rat hippocampal NSCs assessed by cell-counting-kit-8 assay. Ghrelin also suppressed OGD-induced excessive autophagy activity. The protective effect of ghrelin was accompanied by an increased expression levels of Bcl-2, p-62 and decreased expression level of LC3-II, Beclin-1 by Western blot. Furthermore, ghrelin reduced autophagosome formation and number of GFP-LC3 transfected puncta. In conclusion, our data suggest that ghrelin protects adult rat hippocampal NSCs from excessive autophagy in experimental stroke (oxygen-glucose deprivation) model. Regulating autophagic activity may be a potential optimizing target for promoting adult rat hippocampal NSCs based therapy for stroke.

Mdivi-1 Protects Adult Rat Hippocampal Neural Stem Cells against Palmitate-Induced Oxidative Stress and Apoptosis.

Palmitate concentrations in type 2 diabetic patients are higher than in healthy subjects. The prolonged elevation of plasma palmitate levels induces oxidative stress and mitochondrial dysfunction in neuronal cells. In this study, we examined the role of mdivi-1, a selective inhibitor of mitochondrial fission protein dynamin-regulated protein 1 (Drp1), on the survival of cultured hippocampal neural stem cells (NSCs) exposed to high palmitate. Treatment of hippocampal NSCs with mdivi-1 attenuated palmitate-induced increase in cell death and apoptosis. Palmitate exposure significantly increased Drp1 protein levels, which were prevented by pretreatment of cells with mdivi-1. We found that cytosolic Drp1 was translocated to the mitochondria when cells were exposed to palmitate. In contrast, palmitate-induced translocation of Drp1 was inhibited by mdivi-1 treatment. We also investigated mdivi-1 regulation of apoptosis at the mitochondrial level. Mdivi-1 rescued cells from palmitate-induced lipotoxicity by suppressing intracellular and mitochondrial reactive oxygen species production and stabilizing mitochondrial transmembrane potential. Mdivi-1-treated cells showed an increased Bcl-2/Bax ratio, prevention of cytochrome c release, and inhibition of caspase-3 activation. Our data suggest that mdivi-1 protects hippocampal NSCs against lipotoxicity-associated oxidative stress by preserving mitochondrial integrity and inhibiting mitochondrial apoptotic cascades.

Effects of estradiol benzoate on proliferation and differentiation of in vitro cultured hippocampal neural stem cells

Objective To explore the potential mechanism of action of estradiol benzoate on proliferation and differentiation of rat hippocampal neural stem cells. Methods Hippocampus tissues from SD rats were dissociated and plated into culture flasks.Neural stem cells were identified by immunofluorescence against Nestin.After treatment with different concentration of estradiol benzoate(10-10, 10-9, 10-8, 10-7, 10-6 mol/L), the proliferation and differentiation of neural stem cells were assessed by MTT assay and the proportion of neurons and astrocytes in differentiated cells was assessed by flow cytometry.Western blot assay was performed to detect the expression levels of protein in neural stem cells. Results (1)The neural stem cells formed neurospheres and grew in floating, and were Nestin-positive.Estrogen receptors, including ERα and ERβ, were expressed in neural stem cells; (2)After treatment with 10-8 mol/L estradiol benzoate versus in the control group, the cell viability was significantly increased(t=5.36, P=0.003), and the ratio of neuron-specific nuclear protein(NeuN)-positive neuron cells in total cells was significantly increased(t=4.32, P=0.02), but the ratio of glial fibers acidic protein(GFAP)-positive cell in total cells was decreased(t=4.65, P=0.008). The expression levels of GDNF, GFRal and Ret proteins were enhanced in the estradiol benzoate group compared with the control group. Conclusions Appropriate concentration of estradiol benzoate promotes proliferation and differentiation ofin vitrocultured hippocampal neural stem cells and elevates the ratio between neurons and glial cells differentiated from neural stem cells. Key words: Estradiol; Stem cells; Hippocampus

Ghrelin gene products rescue cultured adult rat hippocampal neural stem cells from high glucose insult.

Adult hippocampal neurogenesis is decreased in type 2 diabetes, and this impairment appears to be important in cognitive dysfunction. Previous studies suggest that ghrelin gene products (acylated ghrelin (AG), unacylated ghrelin (UAG) and obestatin (OB)) promote neurogenesis. Therefore, we hypothesize that ghrelin gene products may reduce the harmful effects of high glucose (HG) on hippocampal neural stem cells (NSCs). The aim of this study was to investigate the role of these peptides on the survival of cultured hippocampal NSCs exposed to HG insult. Treatment of hippocampal NSCs with AG, UAG or OB inhibited HG-induced cell death and apoptosis. Exposure of cells to the growth hormone secretagogue receptor 1a antagonist abolished the protective effects of AG against HG toxicity, whereas those of UAG or OB were preserved. All three peptides attenuated HG-induced decrease in BrdU-labeled and phosphohistone-H3-labeled cells. We also investigated the effects of ghrelin gene products on the regulation of apoptosis at the mitochondrial level. AG, UAG or OB rescued hippocampal NSCs from HG insult by inhibiting intracellular and mitochondrial reactive oxygen species generation and stabilizing mitochondrial transmembrane potential. In addition, cells treated with ghrelin gene products showed an increased Bcl-2 and decreased Bax levels, thereby increasing the Bcl-2/Bax ratio, inhibiting cytochrome c release and preventing caspase-3 activation. Finally, AG-, UAG- or OB-mediated protection was dependent on the activities of adenosine monophosphate-activated protein kinase/uncoupling protein 2 pathway. Our data indicate that ghrelin gene products may act as survival factors that preserve mitochondrial function and inhibit oxidative stress-induced apoptosis.

Impaired Memory in OT-II Transgenic Mice Is Associated with Decreased Adult Hippocampal Neurogenesis Possibly Induced by Alteration in Th2 Cytokine Levels.

Recently, an increasing number of studies have focused on the effects of CD4+ T cell on cognitive function. However, the changes of Th2 cytokines in restricted CD4+ T cell receptor (TCR) repertoire model and their effects on the adult hippocampal neurogenesis and memory are not fully understood. Here, we investigated whether and how the mice with restricted CD4+ repertoire TCR exhibit learning and memory impairment by using OT-II mice. OT-II mice showed decreased adult neurogenesis in hippocampus and short- and long- term memory impairment. Moreover, Th2 cytokines in OT-II mice are significantly increased in peripheral organs and IL-4 is significantly increased in brain. Finally, IL-4 treatment significantly inhibited the proliferation of cultured adult rat hippocampal neural stem cells. Taken together, abnormal level of Th2 cytokines can lead memory dysfunction via impaired adult neurogenesis in OT-II transgenic.

Ghrelin regulates cell cycle-related gene expression in cultured hippocampal neural stem cells.

We have previously demonstrated that ghrelin stimulates the cellular proliferation of cultured adult rat hippocampal neural stem cells (NSCs). However, little is known about the molecular mechanisms by which ghrelin regulates cell cycle progression. The purpose of this study was to investigate the potential effects of ghrelin on cell cycle regulatory molecules in cultured hippocampal NSCs. Ghrelin treatment increased proliferation assessed by CCK-8 proliferation assay. The expression levels of proliferating cell nuclear antigen and cell division control 2, well-known cell-proliferating markers, were also increased by ghrelin. Fluorescence-activated cell sorting analysis revealed that ghrelin promoted progression of cell cycle from G0/G1 to S phase, whereas this progression was attenuated by the pretreatment with specific inhibitors of MEK/extracellular signal-regulated kinase 1/2, phosphoinositide 3-kinase/Akt, mammalian target of rapamycin, and janus kinase 2/signal transducer and activator of transcription 3. Ghrelin-induced proliferative effect was associated with increased expression of E2F1 transcription factor in the nucleus, as determined by Western blotting and immunofluorescence. We also found that ghrelin caused an increase in protein levels of positive regulators of cell cycle, such as cyclin A and cyclin-dependent kinase (CDK) 2. Moreover, p27(KIP1) and p57(KIP2) protein levels were reduced when cell were exposed to ghrelin, suggesting downregulation of CDK inhibitors may contribute to proliferative effect of ghrelin. Our data suggest that ghrelin targets both cell cycle positive and negative regulators to stimulate proliferation of cultured hippocampal NSCs.

Propofol Promotes Proliferation of Cultured Adult Rat Hippocampal Neural Stem Cells

The effect of propofol on proliferation of adult neural stem cells (ANSCs) is unclear. We investigated the effect of propofol on cultured rat ANSCs and the underlying molecular mechanisms, especially the role of activated cAMP response element binding protein (CREB). Rat ANSCs were treated with propofol at concentrations of 0 (control), 10, 50, or 100 μM, or with a DMSO vehicle. The cell viability was checked by cell counting and MTT assay. The proportions of BrdU-positive cells and pyknotic nuclei were also checked. Caspase activity was measured by a colorimetric assay. Cytoplasmic [Ca] were determined with Fura2-AM. The expression of CREB and phospho-CREB in cells was examined by immunostaining and Western blot. The role of p-CREB in cell proliferation was confirmed by using KN93, an inhibitor of p-CREB formation. Propofol promoted the proliferation of ANSCs (P<0.01) and increased the proportion of BrdU-positive cells (P<0.01). Cell death was maintained at a low level (P=0.0691) and inhibition of caspase-3 activity with propofol was not significant (P=0.0839). Propofol elevated the cytoplasmic-free calcium concentrations in ANSCs (P=0.0057). CREB and phospho-CREB were generally expressed in ANSCs with or without application of propofol. Propofol upregulated the phosphorylation level of CREB in ANSCs (P=0.0074). Application of KN93 diminished the proliferative effects of propofol and p-CREB levels (P<0.01) without disturbance of intracellular [Ca] (P=0.0722). Propofol acts partly through a Ca-mediated pathway to enhance CREB phosphorylation. We believe this mechanism promotes the in vitro proliferation of ANSCs.

Multiple signaling pathways mediate ghrelin-induced proliferation of hippocampal neural stem cells

Ghrelin, an endogenous ligand for the GH secretagogue receptor (GHS-R) receptor 1a (GHS-R1a), has been implicated in several physiologic processes involving the hippocampus. The aim of this study was to investigate the molecular mechanisms of ghrelin-stimulated neurogenesis using cultured adult rat hippocampal neural stem cells (NSCs). The expression of GHS-R1a was detected in hippocampal NSCs, as assessed by western blot analysis and immunocytochemistry. Ghrelin treatment increased the proliferation of cultured hippocampal NSCs assessed by BrdU incorporation. The exposure of cells to the receptor-specific antagonist d-Lys-3-GHRP-6 abolished the proliferative effect of ghrelin. By contrast, ghrelin showed no significant effect on cell differentiation. The expression of GHS-R1a was significantly increased by ghrelin treatment. The analysis of signaling pathways showed that ghrelin caused rapid activation of ERK1/2 and Akt, which were blocked by the GHS-R1a antagonist. In addition, ghrelin stimulated the phosphorylation of Akt downstream effectors, such as glycogen synthase kinase (GSK)-3β, mammalian target of rapamycin (mTOR), and p70(S6K). The activation of STAT3 was also caused by ghrelin treatment. Furthermore, pretreatment of cells with specific inhibitors of MEK/ERK1/2, phosphatidylinositol-3-kinase (PI3K)/Akt, mTOR, and Jak2/STAT3 attenuated ghrelin-induced cell proliferation. Taken together, our results support a role for ghrelin in adult hippocampal neurogenesis and suggest the involvement of the ERK1/2, PI3K/Akt, and STAT3 signaling pathways in the mediation of the actions of ghrelin on neurogenesis. Our data also suggest that PI3K/Akt-mediated inactivation of GSK-3β and activation of mTOR/p70(S6K) contribute to the proliferative effect of ghrelin.

Are newborn rat-derived neural stem cells more sensitive to lead neurotoxicity?

Lead ion (Pb2+) has been proven to be a neurotoxin due to its neurotoxicity on mammalian nervous system, especially for the developing brains of juveniles. However, many reported studies involved the negative effects of Pb2+ on adult neural cells of humans or other mammals, only few of which have examined the effects of Pb2+ on neural stem cells. The purpose of this study was to reveal the biological effects of Pb2+ from lead acetate [Pb (CH3COO)2] on viability, proliferation and differentiation of neural stem cells derived from the hippocampus of newborn rats aged 7 days and adult rats aged 90 days, respectively. This study was carried out in three parts. In the first part, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (MTT viability assay) was used to detect the effects of Pb2+ on the cell viability of passage 2 hippocampal neural stem cells after 48-hour exposure to 0–200 μM Pb2+. In the second part, 10 μM bromodeoxyuridine was added into the culture medium of passage 2 hippocampal neural stem cells after 48-hour exposure to 0–200 μM Pb2+, followed by immunocytochemical staining with anti-bromodeoxyuridine to demonstrate the effects of Pb2+ on cell proliferation. In the last part, passage 2 hippocampal neural stem cells were allowed to grow in the differentiation medium with 0–200 μM Pb2+. Immunocytochemical staining with anti-microtubule-associated protein 2 (a neuron marker), anti-glial fibrillary acidic protein (an astrocyte marker), and anti-RIP (an oligodendrocyte marker) was performed to detect the differentiation commitment of affected neural stem cells after 6 days. The data showed that Pb2+ inhibited not only the viability and proliferation of rat hippocampal neural stem cells, but also their neuronal and oligodendrocyte differentiation in vitro. Moreover, increased activity of astrocyte differentiation of hippocampal neural stem cells from both newborn and adult rats was observed after exposure to high concentration of lead ion in vitro. These findings suggest that hippocampal neural stem cells of newborn rats were more sensitive than those from adult rats to Pb2+ cytotoxicity.

Effects of Panax Notoginseng Saponins on Proliferation and Differentiation of Rat Hippocampal Neural Stem Cells

We aimed to investigate the effects of Panax notoginseng saponins (PNS) on proliferation, differentiation and self-renewal of rat hippocampal neural stem cells (NSCs) in vitro. Rat hippocampal NSCs were isolated from post-natal day 1 (P1) rats and cultured in a serum-free medium. The neurospheres were identified by the expressions of nestin, class III β-tublin (Tuj-1) and glial fibrillary acid protein (GFAP). The cells were given PNS and subjected to oxygen glucose deprivation (OGD) as an in vitro model of brain ischemia reperfusion. The proliferation of NSCs was determined by MTT colorimetry, nestin/BrdU immunofluorescent double-labeling and RT-PCR. Differentiation of NSCs was assessed by immunofluorescent double-labeling of nestin/BrdU, nestin/vimentin, and nestin/Tuj-1. The primary cells and the first two passages of cells formed certain amount of neurospheres, the cells derived from a single cell clone also formed neurospheres. Nestin, BrdU, GFAP and Tuj-1-positive cells appeared in those neurospheres. Compared to the control group, PNS significantly promoted NSC proliferation and the expression of nestin/BrdU, and also enhanced Tuj-1, vimentin, and nestin mRNA expressions in hippocampal NSCs. PNS significantly increased area density, optical density and numbers of nestin/BrdU, nestin/vimentin, and nestin/Tuj-1 positive cells following OGD. These results indicate that PNS can promote proliferation and differentiation of hippocampus NCSs in vitro after OGD, suggesting its potential benefits on neurogenesis and neuroregeneration in brain ischemic injury.

The Aromatic Amino Acid Residues of Tumor Necrosis Factor Receptor‐1‐Derived Peptide are Important for Promoting Differentiation of Neural Stem Cells

Neural stem cells have the self-renewal capacity and the ability to differentiate into all types of nerve cells. We previously reported that the tumor necrosis factor receptor-1-derived peptide promotes neural differentiation of fetal rat hippocampal neural stem cells. The tumor necrosis factor receptor-1-derived peptide contains six aromatic amino acid residues among its 14 amino acid residues. To clarify the role of these aromatic amino acid residues in the action of tumor necrosis factor receptor-1-derived peptide on neural stem cells, we synthesized mutant peptides, in which aromatic residues were substituted with alanine, and we assessed their effects. Substitution of the tyrosine residue at position 103 (Y(103)) or 106 (Y(106)), the tryptophan residue at position 107 (W(107)), or the phenylalanine residue at position 112 (F(112)) or 115 (F(115)), decreased the ability of the peptide to promote neurite outgrowth of neural stem cells depending on their concentration. These data suggest that although all five aromatic amino acid residues mediate the action of the tumor necrosis factor receptor-1-derived peptide, their order of importance in this activity is F(115) > Y(103) > W(107) > Y(106) and F(112).

A Synthetic Small Molecule That Induces Neuronal Differentiation of Adult Hippocampal Neural Progenitor Cells

Brain power: An image-based screen of a chemical library was carried out to identify molecules that regulate the differentiation of adult rat hippocampal neural stem cells. Neuropathiazol (1) induces selective neuronal differentiation and competitively suppresses astrocyte differentiation. This compound should be a useful tool to study the processes that control stem-cell fate both in vitro and in vivo.