Growth Of Neural Progenitor Cells Research Articles

Engineering Biomimetic Nanofiber Microspheres with Tailored Size, Predesigned Structure, and Desired Composition via Gas Bubble-Mediated Coaxial Electrospray.

Minimally invasive therapies avoiding surgical complexities evoke great interest in developing injectable biomedical devices. Herein, a versatile approach is reported for engineering injectable and biomimetic nanofiber microspheres (NMs) with tunable sizes, predesigned structures, and desired compositions via gas bubble-mediated coaxial electrospraying. The sizes and structures of NMs are controlled by adjusting processing parameters including air flow rate, applied voltage, distance, and spinneret configuration in the coaxial setup. Importantly, unlike the self-assembly method, this technique can be used to fabricate NMs from any material feasible for electrospinning or other nanofiber fabrication techniques. To demonstrate the versatility, open porous NMs are successfully fabricated that consist of various short nanofibers made of poly(ε-caprolactone), poly(lactic-co-glycolic acid), gelatin, methacrylated gelatin, bioglass, and magneto-responsive polymer composites. Open porous NMs support human neural progenitor cell growth in 3D with a larger number and more neurites than nonporous NMs. Additionally, highly open porous NMs show faster cell infiltration and host tissue integration than nonporous NMs after subcutaneous injection to rats. Such a novel class of NMs holds great potential for many biomedical applications such as tissue filling, cell and drug delivery, and minimally invasive tissue regeneration.

Ethanol Exposure Increases miR-140 in Extracellular Vesicles: Implications for Fetal Neural Stem Cell Proliferation and Maturation.

Neural stem cells (NSCs) generate most of the neurons of the adult brain in humans, during the mid-first through second-trimester period. This critical neurogenic window is particularly vulnerable to prenatal alcohol exposure, which can result in diminished brain growth. Previous studies showed that ethanol (EtOH) exposure does not kill NSCs, but, rather, results in their depletion by influencing cell cycle kinetics and promoting aberrant maturation, in part, by altering NSC expression of key neurogenic miRNAs. NSCs reside in a complex microenvironment rich in extracellular vesicles, shown to traffic miRNA cargo between cells. We profiled the miRNA content of extracellular vesicles from control and EtOH-exposed ex vivo neurosphere cultures of fetal NSCs. We subsequently examined the effects of one EtOH-sensitive miRNA, miR-140-3p, on NSC growth, survival, and maturation. EtOH exposure significantly elevates levels of a subset of miRNAs in secreted extracellular vesicles. Overexpression of one of these elevated miRNAs, miR-140-3p, and its passenger strand relative, miR-140-5p, significantly increased the proportion of S-phase cells while decreasing the proportion of G0 /G1 cells compared to controls. In contrast, while miR-140-3p knockdown had minimal effects on the proportion of cells in each phase of the cell cycle, knockdown of miR-140-5p significantly decreased the proportion of cells in G2 /M phase. Furthermore, miR-140-3p overexpression, during mitogen-withdrawal-induced NSC differentiation, favors astroglial maturation at the expense of neural and oligodendrocyte differentiation. Collectively, the dysregulated miRNA content of extracellular vesicles following EtOH exposure may result in aberrant neural progenitor cell growth and maturation, explaining brain growth deficits associated with prenatal alcohol exposure.

Release of methylene blue from graphene oxide-coated electrospun nanofibrous scaffolds to modulate functions of neural progenitor cells

Transplantation of neural progenitor cells (NPCs) can repair the damaged neurons and therefore holds significant promise as a new treatment strategy for Alzheimer’s disease (AD). Development of functional scaffolds for the growth, proliferation, and differentiation of NPCs offers a useful approach for AD therapy. In our study, the functional scaffolds were obtained by fabrication of a poly(lactic-co-glycolic acid) (PLGA) nanofibrous mat by the electrospinning technique, followed by coating of a layer of graphene oxide (GO) and then physisorption of methylene blue (MB) under mild conditions. The precoating of GO on the nanofibrous scaffolds allows efficient loading and release of MB from the substrate for regulating the functions of NPCs. The NPCs cultured on the scaffolds remained in the quiescence phase due to the activation of autophagy signaling pathway by MB. Moreover, the MB-loaded nanofibrous scaffolds diminish tau phosphorylation and protect NPCs from apoptosis. Definitely, more work, especially the in vivo experiment, is highly desired to demonstrate the feasibility of the current strategy for AD treatment. Statement of SignificanceTransplantation of neural progenitor cells (NPCs) can repair the damaged neurons and hold significant promise as a new treatment strategy for Alzheimer’s disease (AD). Development of functional scaffolds for the growth, proliferation, and differentiation of NPCs offers a novel and useful approach for AD therapy. In this work, we have developed a GO and MB sequentially coated PLGA nanofibrous mat as a new scaffold for NPC transplantation and tauopathy inhibition. The coating of GO that we have demonstrated significantly enhanced the loading and release of MB on the scaffolds. Furthermore, NPCs cultured on the nanofibrous scaffolds entered quiescence phase through the activation of autophagy signaling pathway, leading to improved performance of NPCs to cope with stressors of disease. More importantly, the release of MB from the scaffolds leads to attenuation of tauopathy and protection of NPCs, which may represent a novel, versatile, and effective therapeutic approach for AD and other neurodegenerative diseases.

Quercetin promotes learning and memory performance concomitantly with neural stem/progenitor cell proliferation and neurogenesis in the adult rat dentate gyrus

The decline in neurogenesis is a very critical problem in Alzheimer disease. Different biological activities have been reported for medicinal application of quercetin. Herein, we investigated the neurogenesis potential of quercetin in a rat model of Alzheimer's disease induced by amyloid-beta injection. Rats were randomly divided into Control, Alzheimer + Saline and Alzheimer + Quercetin groups. Following the administration of Amyloid-beta, rats in the Alzheimer + Quercetin group received 40 mg/kg/day quercetin orally for one month. Our data demonstrated amyloid-β injection could impair learning and memory processing in rats indicated by passive avoidance test evaluation. We noted that one-month quercetin treatment alleviated the detrimental effects of amyloid-β on spatial learning and memory parameters using Morris water maze analysis. Quercetin was found to increase the number of proliferating neural stem/progenitor cells. Notably, quercetin increased the number of DCX-expressing cells, indicating the active dynamic growth of neural progenitor cells in the dentate gyrus of the hippocampus. We further observed that the quercetin improved the number of BrdU/NeuN positive cells contributed to enhanced adult neurogenesis. Based on our results, quercetin had the potential to promote the expression of BDNF, NGF, CREB, and EGR-1 genes involved in regulating neurogenesis. These data suggest that quercetin can play a valuable role in alleviating Alzheimer's disease symptoms by enhancing adult neurogenesis mechanism.

Differentiation of circulating neural progenitor cells in vitro on fibrin-based composite -matrix involves Wnt- β-catenin-like signaling.

Isolation of progenitors with regenerative potential and their in vitro induction to specific lineage may be necessary for effective cell transplantation outcome. Earlier, we standardized specific niche for derivation of neural progenitor cells (NPCs) from circulating mononuclear cells to neural like cells (NLC) in vitro, for applications in neural regeneration. The current study analysed the prospective involvement of signaling mechanism for in vitro lineage commitment of circulating NPCs. Preferred mechanism selected was Wnt-like signaling because this is one of the pathways implicated in the central nervous system (CNS) development and homeostasis. We sought to determine the activation of Wnt3a-specific genes in the standardized NPC culture system. To start with, it was found that when standardized NPC culture niche was supplemented with Wnt 3a protein, no additional morphological changes happen. Chemical inhibitors of the pathway retarded NPC to NLC conversion both in the absence and presence of supplemented Wnt-3a. In earlier studies, involvement of the niche constituents- fibronectin (FN), laminin (La) and fibrin (Fib)- for NPC growth and differentiation was established. In an attempt to study the role of these adhesive proteins by adding antibodies against FN, La & Fib together, molecular level signaling changes seen were comparable to that occur in response to Wnt3a chemical inhibitor. Therefore, induction of Wnt 3a-like signal from the matrix-dependent niche constituents may be implicated in the differentiation of NPC to NLC. The results substantiate the potential applications of the fibrin-based composite niche in neural engineering for regeneration.

Stalled replication forks within heterochromatin require ATRX for protection.

Expansive growth of neural progenitor cells (NPCs) is a prerequisite to the temporal waves of neuronal differentiation that generate the six-layered neocortex, while also placing a heavy burden on proteins that regulate chromatin packaging and genome integrity. This problem is further reflected by the growing number of developmental disorders caused by mutations in chromatin regulators. ATRX gene mutations cause a severe intellectual disability disorder (α-thalassemia mental retardation X-linked (ATRX) syndrome; OMIM no. 301040), characterized by microcephaly, urogenital abnormalities and α-thalassemia. Although the ATRX protein is required for the maintenance of repetitive DNA within heterochromatin, how this translates to disease pathogenesis remain poorly understood and was a focus of this study. We demonstrate that AtrxFoxG1Cre forebrain-specific conditional knockout mice display poly(ADP-ribose) polymerase-1 (Parp-1) hyperactivation during neurogenesis and generate fewer late-born Cux1- and Brn2-positive neurons that accounts for the reduced cortical size. Moreover, DNA damage, induced Parp-1 and Atm activation is elevated in progenitor cells and contributes to their increased level of cell death. ATRX-null HeLa cells are similarly sensitive to hydroxyurea-induced replication stress, accumulate DNA damage and proliferate poorly. Impaired BRCA1-RAD51 colocalization and PARP-1 hyperactivation indicated that stalled replication forks are not efficiently protected. DNA fiber assays confirmed that MRE11 degradation of stalled replication forks was rampant in the absence of ATRX or DAXX. Indeed, fork degradation in ATRX-null cells could be attenuated by treatment with the MRE11 inhibitor mirin, or exacerbated by inhibiting PARP-1 activity. Taken together, these results suggest that ATRX is required to limit replication stress during cellular proliferation, whereas upregulation of PARP-1 activity functions as a compensatory mechanism to protect stalled forks, limiting genomic damage, and facilitating late-born neuron production.

Studies using IPS cells support a possible link between ZIKA and microcephaly.

There is a suspected link between Brazilian babies born with microcephaly and Zika virus (ZIKV) infection. However, little is know about the brain cell targets and the mechanisms that Zika virus may cause microcephaly. A recent report demonstrated that Zika virus infection increases cell death and dysregulates cell-cycle, resulting in attenuated human neural progenitor cells growth. This study fills a major gap and serves as an entry point to establish a mechanistic link between Zika infection and microcephaly.

Bidirectional crosstalk between periventricular endothelial cells and neural progenitor cells promotes the formation of a neurovascular unit

Interactions between neural progenitor cells (NPC) and endothelial cells (EC) from adult vascular beds have been well explored previously. However, the factors and signaling mechanisms that regulate neurogenesis and angiogenesis are most prevalent during embryonic development. This study aimed to determine whether embryonic brain endothelial cells from the periventricular region (PVEC) present an advantage over adult brain EC in supporting NPC growth and differentiation. PVEC were isolated from E15 mouse brains, processed, and sorted with immunomagnetic beads using antibodies against CD31/PECAM. On immunofluorescence (IF) staining, nearly all cells were positive for EC markers CD31 and CD144/VE-Cadherin. In proliferation studies, NPC proliferation was highest in transwell co-culture with PVEC, approximately 2.3 fold increase compared to baseline versus 1.4 fold increase when co-cultured with adult brain endothelial cells (ABEC). These results correlated with the PVEC mediated delay in NPC differentiation, evidenced by high expression of progenitor marker Nestin evaluated by IF staining. Upon further characterization of PVEC in an angiogenesis assay measuring cord length, PVEC exhibited a high capacity to form cords in basal conditions compared to ABEC. This was enhanced in the presence of NPC, with both cell types displaying a preferential structural alignment resembling neurovascular networks. PVEC also expressed high Vegfa levels at baseline in comparison to NPC and ABEC. Vegfa levels increased when co-cultured with NPC. We demonstrate that PVEC and NPC co-cultures act synergistically to promote the formation of a neurovascular unit through dynamic and reciprocal communication. Our results suggest that PVEC/NPC could provide promising neuro-regenerative therapies for patients suffering brain injuries.

Ephrin-A2 and -A3 are negative regulators of the regenerative potential of Möller cells.

In a previous study, we demonstrated that ephrin-A2 and -A3 negatively regulate the growth of neural progenitor cells in the central nervous system. Adult mice deficient in ephrin-A2 and -A3 (A2(-/-)A3(-/-)) displayed active ongoing neurogenesis throughout the brain, and mice deficient in ephrin-A3 alone showed increased proliferation of ciliary epithelium derived retinal stem cells. This study aimed to detect that the increase in proliferation and neurogenic potential of Müller cells is influenced by the absence of ephrin-A2 and -A3. We assessed the retinal and Müller cell expression of ephrin-As and their receptor and neural progenitor cell markers by immunostaining and real-time PCR. We cultured purified primary Müller cells derived from wild-type and A2(-/-)A3(-/-) mice in a defined culture medium that enables trans-differentiation of Müller cells into retinal neurons. To evaluate proliferating Müller cells in vivo, we injected 5'-ethylnyl-2'-deoxiuridine (EdU) intraperitoneally to adult mice. Expression of ephrin-A2/A3 and their receptor EphA4 were detected in the retinas of adult mice, with EphA4 expression particularly enriched in Müller cells. Müller cells of A2(-/-)A3(-/-) mice exhibited significantly elevated expression of retinal progenitor cell markers, Pax6 and Chx10, when compared with those from wild-type mice. Moreover, a higher percentage of Müller cells of A2(-/-)A3(-/-) mice trans-differentiated and became recoverin+ and β-III-tublin+ in the culture than those from wild type mice. Strikingly, an increased number of EdU+ retinal cells was detected in the retinas of adult A2(-/-)A3(-/-) mice as compared with wild-type mice. Ephrin-A2 and -A3 are negative regulators of the proliferative and neurogenic potentials of Müller cells. Manipulating ephrin-A signaling may thus represent a novel strategy for stimulating neuroregeneration from endogenous progenitors to participate in retinal repair in case of disease or damage.

Micro-Patterned Nanowire Surfaces Encourage Directional Neural Progenitor Cell Adhesion and Proliferation

Peripheral nerve damage is common in the United States, with an estimated 200,000 patients treated surgically each year. Autografts, the current gold standard treatment, require that the patient trade functionality by transplanting a nerve from elsewhere in the body. For this reason, tissue-engineering scaffolds that can regenerate nervous tissue and that can direct proliferation need to be investigated. In this work we investigated the influence of micro-patterned nanowire surfaces on neuronal progenitor cell adhesion and proliferation. We created a simple micro-patterning process to create a micro-patterned scaffold with regions lacking a nano-topography approximately 60 microns in width bordered by regions with a nanowire topography approximately 400 microns in width. We hypothesized that neural progenitor cells would preferentially adhere to the regions containing the nano-topography and in turn would avoid regions lacking the nano-topography. Our results indicate that we can direct neural progenitor cell proliferation using this technique. Furthermore, the results show that after 2 days of culture, cells contacting the boundary have elongated morphology. After 5 days of culture, quantifying dimensions on the cell aggregates reveals that they grow twice as long as they do wide on micro-patterned nanowires when compared to controls. These studies suggest that neural progenitor cell growth can be directed by simply creating a scaffold with distinct linear regions of nano-topography bordered by a smooth, hard, hydrophobic surface.

MELK-Dependent FOXM1 Phosphorylation is Essential for Proliferation of Glioma Stem Cells

Glioblastoma multiforme (GBM) is a life-threatening brain tumor. Accumulating evidence suggests that eradication of glioma stem-like cells (GSCs) in GBM is essential to achieve cure. The transcription factor FOXM1 has recently gained attention as a master regulator of mitotic progression of cancer cells in various organs. Here, we demonstrate that FOXM1 forms a protein complex with the mitotic kinase MELK in GSCs, leading to phosphorylation and activation of FOXM1 in a MELK kinase-dependent manner. This MELK-dependent activation of FOXM1 results in a subsequent increase in mitotic regulatory genes in GSCs. MELK-driven FOXM1 activation is regulated by the binding and subsequent trans-phosphorylation of FOXM1 by another kinase PLK1. Using mouse neural progenitor cells (NPCs), we found that transgenic expression of FOXM1 enhances, while siRNA-mediated gene silencing diminishes neurosphere formation, suggesting that FOXM1 is required for NPC growth. During tumorigenesis, FOXM1 expression sequentially increases as cells progress from NPCs, to pretumorigenic progenitors and GSCs. The antibiotic Siomycin A disrupts MELK-mediated FOXM1 signaling with a greater sensitivity in GSC compared to neural stem cell. Treatment with the first-line chemotherapy agent for GBM, Temozolomide, paradoxically enriches for both FOXM1 (+) and MELK (+) cells in GBM cells, and addition of Siomycin A to Temozolomide treatment in mice harboring GSC-derived intracranial tumors enhances the effects of the latter. Collectively, our data indicate that FOXM1 signaling through its direct interaction with MELK regulates key mitotic genes in GSCs in a PLK1-dependent manner and thus, this protein complex is a potential therapeutic target for GBM. Stem Cells 2013;31:1051–1063

Abstract 4912: MELK-dependent phosphorylation of FOXM1 is essential for mitotic progression of glioma stem cells.

Abstract Glioblastoma multiforme (GBM) is a life-threatening brain tumor. Accumulating evidence suggests that eradication of glioma stem-like cells (GSCs) in GBM is essential to achieve cure. The transcription factor FOXM1 has recently gained attention as a master regulator for mitotic progression of cancer cells in various organs. Here, we demonstrate that FOXM1 forms a protein complex with the serine/threonine kinase MELK in GSCs, leading to phosphorylation and activation of FOXM1 in a MELK kinase-dependent manner. The MELK-dependent activation of FOXM1 results in an increase of mitotic regulatory genes in GSCs. MELK-driven FOXM1 activation is regulated by the binding and subsequent trans-phosphorylation of FOXM1 by another kinase PLK1 (Polo-like kinase 1). Using neural progenitor cells (NPCs) derived from mouse brains, we found that transgene expression of FOXM1 enhances, while its siRNA-mediated gene silencing diminishes clonal neurosphere formation, suggesting that FOXM1 is required for NPC growth. During tumorigenesis, FOXM1 expression sequentially increases from NPCs, pre-tumorigenic progenitors, and GSCs. As expected, sensitivity of GSCs to pharmacological inhibition of MELK-mediated FOXM1 signaling via the thiazole antibiotic Siomycin A is substantially higher than NPCs. In addition, treatment with the first-line chemotherapy agent for GBM, Temozolomide, paradoxically enriches for both FOXM1 (+) and MELK (+) cells in GBM cell culture, and addition of Siomycin A to Temozolomide treatment to mice harboring GSC-derived intracranial tumors enhances the effects of the latter. Collectively, our data indicate that FOXM1 signaling through its direct interaction with the kinase domain of MELK regulates mitotic key genes in GSCs in a PLK1-dependent manner and thus, this protein complex is a potential therapeutic target for GBM. Citation Format: Kaushal Joshi, Ichiro Nakano. MELK-dependent phosphorylation of FOXM1 is essential for mitotic progression of glioma stem cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4912. doi:10.1158/1538-7445.AM2013-4912

Assessing the efficacy of endoscopic office olfactory biopsy sites to produce neural progenitor cell cultures for the study of neuropsychiatric disorders

The olfactory region is capable of continuous neurogenesis. Situated on the cribriform plate and segments of the superior septum and both superior and middle turbinates, it is accessible through office-based biopsy and can be used to generate neural progenitor cells to study molecular abnormalities associated with neuropsychiatric disorders. The purpose of the study was to evaluate the efficacy of the endoscopic office olfactory biopsy from middle turbinate and superior-posterior septum to produce the neural progenitor cells. Endoscopic office-based biopsy samples were collected and cultured neuronal cells derived from olfactory neuroepithelium (CNON) were established from 40 healthy individuals and 40 schizophrenia patients. All patients underwent biopsies of both the middle turbinate and the superior-posterior septum. Specific culture conditions promoted the growth of neural progenitor cells from these biopsy sites. CNON cultures were established from such outgrowing neuronal cells. The study was institutional review board (IRB)-approved and informed consent was obtained. Cultures were successfully developed from 98.8% of participants. No complications were observed. The single, unsuccessful specimen failed to grow any cell types due to tissue mishandling. Overall, we have observed no significant difference in the effectiveness of biopsy from middle turbinate and superior-posterior septum to produce neural progenitor cells. The middle turbinate biopsies contain viable neural progenitor cells capable of generating neuronal cell cultures. Thus technically more simple biopsy of the middle turbinate can be used to propagate neural progenitor cells.

Cul4B regulates neural progenitor cell growth

BackgroundCullin ubiquitin ligases are activated via the covalent modification of Cullins by the small ubiquitin-like protein nedd8 in a process called neddylation. Genetic mutations of cullin-4b (cul4b) cause a prevalent type of X-linked intellectual disability (XLID) in males, but the physiological function of Cul4B in neuronal cells remains unclear.ResultsThere are three major isoforms of Cul4B (1, 2, and 3) in human and rodent tissues. By examining the endogenous Cul4B isoforms in the brain, this study demonstrates that Cul4B-1 and Cul4B-2 isoforms are unneddylated and more abundant in the brain whereas the lesser species Cul4B-3 that misses the N-terminus present in the other two isoforms is neddylated. The data suggest that the N-terminus of Cul4B inhibits neddylation in the larger isoforms. Immunostaining of human NT-2 cells also shows that most Cul4B is unneddylated, especially when it is localized in the process in G0-synchronized cells. This study demonstrates that Cul4B accumulates during mitosis and downregulation of Cul4B arrests NPCs and NT-2 cells in the G2/M phase of the cell cycle. In both human and rodent brain tissues, Cul4B-positive cells accumulate β-catenin in the dentate subgranular zone and the subventricular zone. These Cul4B-positive cells also co-express the MPM-2 mitotic epitope, suggesting that Cul4B is also necessary for mitosis progression in vivo.ConclusionsThis study provides first evidence that unneddylated Cul4B isoforms exist in the brain and are necessary for mitosis progression in NPCs. The data suggest that unneddylated Cul4B isoforms specifically inhibits β-catenin degradation during mitosis. Furthermore, unneddylated Cul4B may play a role in addition to cell cycle since it is exclusively localized to the processes in starved NT-2 cells. Further analyses of the different isoforms of Cul4B will help understand the cognitive deficits in Cul4B-linked XLID and give insights into drug and biomarker discoveries.

Seeding neural progenitor cells on silicon-based neural probes

Chronically implanted neural electrode arrays have the potential to be used as neural prostheses in patients with various neurological disorders. While these electrodes perform well in acute recordings, they often fail to function reliably in clinically relevant chronic settings because of glial encapsulation and the loss of neurons. Surface modification of these implants may provide a means of improving their biocompatibility and integration within host brain tissue. The authors proposed a method of improving the brain-implant interface by seeding the implant's surface with a layer of neural progenitor cells (NPCs) derived from adult murine subependyma. Neural progenitor cells may reduce the foreign body reaction by presenting a tissue-friendly surface and repair implant-induced injury and inflammation by releasing neurotrophic factors. In this study, the authors evaluated the growth and differentiation of NPCs on laminin-immobilized probe surfaces and explored the potential impact on transplant survival of these cells. Laminin protein was successfully immobilized on the silicon surface via covalent binding using silane chemistry. The growth, adhesion, and differentiation of NPCs expressing green fluorescent protein (GFP) on laminin-modified silicon surfaces were characterized in vitro by using immunocytochemical techniques. Shear forces were applied to NPC cultures in growth medium to evaluate their shearing properties. In addition, neural probes seeded with GFP-labeled NPCs cultured in growth medium for 14 days were implanted in murine cortex. The authors assessed the adhesion properties of these cells during implantation conditions. Moreover, the tissue response around NPC-seeded implants was observed after 1 and 7 days postimplantation. Significantly improved NPC attachment and growth was found on the laminin-immobilized surface compared with an unmodified control before and after shear force application. The NPCs grown on the laminin-immobilized surface showed differentiation potential similar to those grown on polylysine-treated well plates, as previously reported. Viable (still expressing GFP) NPCs were found on and in proximity to the neural implant after 1 and 7 days postimplantation. Preliminary examinations indicated that the probe's NPC coating might reduce the glial response at these 2 different time points. The authors' findings suggest that NPCs can differentiate and strongly adhere to laminin-immobilized surfaces, providing a stable matrix for these cells to be implanted in brain tissue on the neural probe's surface. In addition, NPCs were found to improve the astrocytic reaction around the implant site. Further in vivo work revealing the mechanisms of this effect could lead to improvement of biocompatibility and chronic recording performance of neural probes.

A high-fat diet impairs neurogenesis: Involvement of lipid peroxidation and brain-derived neurotrophic factor

Obesity is a growing global health problem that contributes to diabetes, hypertension, cardiovascular diseases, dementia, and cancer. The increased consumption of saturated fats in a high-fat diet (HFD) contributes to obesity, neurodegenerative diseases, long-term memory loss, and cognitive impairment. We tested whether HFD influences adult hippocampal neurogenesis. Male C57BL/6 mice were divided into two groups and maintained on either a normal diet (ND) or HFD. Seven weeks of HFD significantly decreased the numbers of newly generated cells in the dentate gyrus of the hippocampus without neuronal loss. HFD also increased the level of malondialdehyde (MDA) and decreased the level of brain-derived neurotrophic factor (BDNF) in the hippocampus. The toxic effects of MDA were evaluated on neural progenitor cells (NPCs). MDA reduced the growth of NPCs, but BDNF treatment restored NPCs proliferation. The present data indicate that a HFD impairs hippocampal neurogenesis and NPCs proliferation through increased lipid peroxidation and decreased BDNF.

Cleavage of the Wnt Receptor Ryk Regulates Neuronal Differentiation during Cortical Neurogenesis

Ryk is a transmembrane receptor tyrosine kinase (RTK). It functions as a receptor of Wnt proteins required for cell-fate determination, axon guidance, and neurite outgrowth in different organisms; however, the molecular mechanism of Ryk signaling is unknown. Here, we show that Ryk is cleaved, permitting the intracellular C-terminal fragment of Ryk to translocate to the nucleus in response to Wnt3 stimulation. We also show that the cleaved intracellular domain of Ryk is required for Wnt3-induced neuronal differentiation in vitro and in vivo. These results demonstrate an unexpected mechanism of signal transduction for Ryk as a Wnt receptor, in which the intracellular domain itself functions as the transducing molecule to bring extracellular signals from the cell surface into the nucleus, to regulate neural progenitor cell differentiation.

Japanese encephalitis virus infects neural progenitor cells and decreases their proliferation

Japanese encephalitis virus (JEV), a common cause of encephalitis in humans, especially in children, leads to substantial neuronal injury. The survivors of JEV infection have severe cognitive impairment, motor and behavioral disorders. We hypothesize that depletion of neural progenitor cells (NPCs) by the virus culminates in neurological sequelae in survivors of Japanese encephalitis (JE). We utilized both in vivo model of JEV infection and in vitro neurosphere cultures to study progressive JEV infection. Cellular infection and cell death was determined by flow cytometry. BrdU administration in animals and in neurospheres was used to determine the proliferative ability of NPCs. JEV leads to massive loss of actively proliferating NPC population from the subventricular zone (SVZ). The ability of JEV infected subventricular zone cells to form neurospheres is severely compromised. This can be attributed to JEV infection in NPCs, which however do not result in robust death of the resilient NPC cells. Instead, JEV suppresses the cycling ability of these cells, preventing their proliferation. JEV primarily targets at a critical postnatal age and severely diminishes the NPC pool in SVZ, thus impairing the process of recovery after the insult. This arrested growth and proliferation of NPCs might have an effect on the neurological consequences in JE survivors.

Ephrins as negative regulators of adult neurogenesis in diverse regions of the central nervous system

In the central nervous system (CNS) of adult mammals, neurogenesis occurs in only two restricted areas, the subgranular zone (SGZ) of the hippocampus and the subventricular zone (SVZ). Isolation of multipotent progenitor cells from other CNS regions suggests that their neurogenic potential is dictated by local environmental cues. Here, we report that astrocytes in areas outside of the SGZ and SVZ of adult mice express high levels of ephrin-A2 and -A3, which present an inhibitory niche, negatively regulating neural progenitor cell growth. Adult mice lacking both ephrin-A2 and -A3 display active ongoing neurogenesis throughout the CNS. These findings suggest that neural cell replacement therapies for neurodegeneration or injury in the adult CNS may be achieved by manipulating ephrin signaling pathways.

Oxygen glucose deprivation inhibits the growth and ERK phosphorylation of neural progenitor cells in vitro

The neurogenic regions such as subventricular zone of the lateral ventricles could become ischemic in some clinical situations due to the blockage of blood vessels by blood clots. Hence the aim of this study is to investigate the effects of OGD on the growth of neural progenitor cells and the phosphorylation of ERK, which plays an important role in the growth of these cells. Oxygen glucose deprivation (OGD) for 4h decreased the growth of neural progenitor cells in vitro and also decreased the phosphorylation of extracellular signal regulated kinase (ERK). Inhibition of the ERK pathway for 4h using U0126 (10 microM) also decreased the growth of progenitor cells. These data suggest that a decline in the phospho-ERK content might decrease the growth of progenitor cells following OGD.