Notch signaling in astrocytes and neuroblasts of the adult subventricular zone in health and after cortical injury

Dtx2 Deficiency Induces Ependymo-Radial Glial Cell Proliferation and Improves Spinal Cord Motor Function Recovery

Traumatic injury to the spinal cord can lead to significant, permanent disability. Mammalian spinal cords are not capable of regeneration; in contrast, adult zebrafish are capable of such regeneration, fully recovering motor function. Understanding the mechanisms underlying zebrafish neuroregeneration may provide useful information regarding endogenous regenerative potential and aid in the development of therapeutic strategies in humans. DELTEX proteins (DTXs) regulate a variety of cellular processes. However, their role in neural regeneration has not been described. We found that zebrafish dtx2, encoding Deltex E3 ubiquitin ligase 2, is expressed in ependymo-radial glial cells in the adult spinal cord. After spinal cord injury, the heterozygous dtx2 mutant fish motor function recovered quicker than that of the wild-type controls. The mutant fish displayed increased ependymo-radial glial cell proliferation and augmented motor neuron formation. Moreover, her gene expression, downstream of Notch signaling, increased in Dtx2 mutants. Notch signaling inactivation by dominant-negative Rbpj abolished the increased ependymo-radial glia proliferation caused by Dtx2 deficiency. These results indicate that ependymo-radial glial proliferation is induced by Dtx2 deficiency by activating Notch-Rbpj signaling to improve spinal cord regeneration and motor function recovery.

Two Sides of The Same Coin: Normal and Tumoral Stem Cells, The Relevance of In Vitro Models and Therapeutic Approaches: The Experience with Zika Virus in Nervous System Development and Glioblastoma Treatment

Neural stem cells (NSCs) were described for the first time more than two decades ago for their ability to differentiate into all neural cell lineages. The isolation of NSCs from adults and embryos was carried out by various laboratories and in different species, from mice to humans. Similarly, no more than two decades ago, cancer stem cells were described. Cancer stem cells, previously identified in hematological malignancies, have now been isolated from several solid tumors (breast, brain, and gastrointestinal compartment). Though the origin of these cells is still unknown, there is a wide consensus about their role in tumor onset, propagation and, in particular, resistance to treatments. Normal and neoplastic neural stem cells share common characteristics, and can thus be considered as two sides of the same coin. This is particularly true in the case of the Zika virus (ZIKV), which has been described as an inhibitor of neural development by specifically targeting NSCs. This understanding prompted us and other groups to evaluate ZIKV action in glioblastoma stem cells (GSCs). The results indicate an oncolytic activity of this virus vs. GSCs, opening potentially new possibilities in glioblastoma treatment.

JAG-1/Notch signaling axis in the spinal cord contributes to bone cancer pain in rats

Notch signal plays an important role in regulating cell-cell interactions with the adjacent cells. However, it remains unknown whether Jagged1 (JAG-1) mediated Notch signaling regulates bone cancer pain (BCP) via the spinal cell interactions mechanism. Here, we showed that intramedullary injection of Walker 256 breast cancer cells increased the expression of JAG-1 in spinal astrocytes and knockdown of JAG-1 reduced BCP. The supplementation of exogenous JAG-1 to the spinal cord induced BCP-like behavior and promoted expression of c-Fos and hairy and enhancer of split homolog-1 (Hes-1) in the spinal cord of the naïve rats. These effects were reversed when the rats were administered intrathecal injections of N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT). The intrathecal injection of DAPT reduced BCP and inhibited Hes-1 and c-Fos expression in the spinal cord. Furthermore, our results showed that JAG-1 up-regulated Hes-1 expression by inducing the recruitment of Notch intracellular domain (NICD) to the RBP-J/CSL-binding site located within the Hes-1 promoter sequence. Finally, the intrathecal injection of c-Fos-antisense oligonucleotides (c-Fos-ASO) and administration of sh-Hes-1 to the spinal dorsal horn also alleviated BCP. The study indicates that inhibition of the JAG-1/Notch signaling axis may be a potential strategy for the treatment of BCP.

Excitotoxic glutamate levels drive spinal cord ependymal stem cell proliferation and fate specification through CP-AMPAR signaling

The adult spinal cord contains a population of ependymal-derived neural stem/progenitor cells (epNSPCs) that are normally quiescent, but are activated to proliferate, differentiate, and migrate after spinal cord injury. The mechanisms that regulate their response to injury cues, however, remain unknown. Here, we demonstrate that excitotoxic levels of glutamate promote the proliferation and astrocytic fate specification of adult spinal cord epNSPCs. We show that glutamate-mediated calcium influx through calcium-permeable alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors (CP-AMPARs) in concert with Notch signaling increases the proliferation of epNSPCs via pCREB, and induces astrocytic differentiation through Hes1 upregulation. Furthermore, the in vivo targeting of this pathway via positive modulation of AMPARs after spinal cord injury enhances epNSPC proliferation, astrogliogenesis, neurotrophic factor production and increases neuronal survival. Our study uncovers an important mechanism by which CP-AMPARs regulate the growth and phenotype of epNSPCs, which can be targeted therapeutically to harness the regenerative potential of these cells after injury.

Characterization by Gene Expression Analysis of Two Groups of Dopaminergic Cells Isolated from the Mouse Olfactory Bulb

The olfactory bulb (OB) is one of two regions of the mammalian brain which undergo continuous neuronal replacement during adulthood. A significant fraction of the cells added in adulthood to the bulbar circuitry is constituted by dopaminergic (DA) neurons. We took advantage of a peculiar property of dopaminergic neurons in transgenic mice expressing eGFP under the tyrosine hydroxylase (TH) promoter: while DA neurons located in the glomerular layer (GL) display full electrophysiological maturation, eGFP+ cells in the mitral layer (ML) show characteristics of immature cells. In addition, they also display a lower fluorescence intensity, possibly reflecting different degrees of maturation. To investigate whether this difference in maturation might be confirmed at the gene expression level, we used a fluorescence-activated cell sorting technique on enzymatically dissociated cells of the OB. The cells were divided into two groups based on their level of fluorescence, possibly corresponding to immature ML cells and fully mature DA neurons from the GL. Semiquantitative real-time PCR was performed to detect the level of expression of genes linked to the degree of maturation of DA neurons. We showed that indeed the cells expressing low eGFP fluorescence are immature neurons. Our method can be further used to explore the differences between these two groups of DA neurons.

Limb Remote Ischemic Conditioning Promotes Neurogenesis after Cerebral Ischemia by Modulating miR-449b/Notch1 Pathway in Mice

Neurogenesis plays an important role in the prognosis of stroke patients and is known to be promoted by the activation of the Notch1 signaling pathway. Studies on the airway epithelium have shown that miR-449b represses the Notch pathway. The study aimed to investigate whether limb remote ischemic conditioning (LRIC) was able to promote neurogenesis in cerebral ischemic mice, and to investigate the role of the miR-449b/Notch1 pathway in LRIC-induced neuroprotection. Male C57BL/6 mice (22–25 g) were subjected to transient middle cerebral artery occlusion (MCAO), and LRIC was performed in the bilateral lower limbs immediately after MCA occlusion. Immunofluorescence staining was performed to assess neurogenesis. The cell line NE-4C was used to elucidate the proliferation of neuronal stem cells in 8% O₂. After LRIC treatment on day 28, mice recovered neurological function. Neuronal precursor proliferation was enhanced in the SVZ, and neuronal precursor migration was enhanced in the basal ganglia on day 7. LRIC promoted the improvement of neurological function in mice on day 28, promoted neuronal precursor proliferation in the SVZ, and enhanced neuronal precursor migration in the basal ganglia on day 7. The neurological function score was negatively correlated with the number of BrdU-positive/DCX-positive cells in the SVZ and striatum. LRIC promoted activated Notch1 protein expression in the SVZ and substantially downregulated miR-449b levels in the SVZ and plasma. In vitro, miR-449b was found to target Notch1. Lentivirus-mediated miR-449b knockdown increased Notch1 levels in NE-4C cells and increased proliferation in the cells. The effects of miR-449b inhibition on neurogenesis were ablated by the application of Notch1 shRNA. Our study showed that LRIC promoted the proliferation and migration of neural stem cells after MCAO, and these effects were modulated by the miR-449b/Notch1 pathway.

Endogenous Neural Stem Cell Mediated Oligodendrogenesis in the Adult Mammalian Brain

Oligodendrogenesis is essential for replacing worn-out oligodendrocytes, promoting myelin plasticity, and for myelin repair following a demyelinating injury in the adult mammalian brain. Neural stem cells are an important source of oligodendrocytes in the adult brain; however, there are considerable differences in oligodendrogenesis from neural stem cells residing in different areas of the adult brain. Amongst the distinct niches containing neural stem cells, the subventricular zone lining the lateral ventricles and the subgranular zone in the dentate gyrus of the hippocampus are considered the principle areas of adult neurogenesis. In addition to these areas, radial glia-like cells, which are the precursors of neural stem cells, are found in the lining of the third ventricle, where they are called tanycytes, and in the cerebellum, where they are called Bergmann glia. In this review, we will describe the contribution and regulation of each of these niches in adult oligodendrogenesis.

Epidermal Growth Factor in the CNS: A Beguiling Journey from Integrated Cell Biology to Multiple Sclerosis. An Extensive Translational Overview

This article reviews the wealth of papers dealing with the different effects of epidermal growth factor (EGF) on oligodendrocytes, astrocytes, neurons, and neural stem cells (NSCs). EGF induces the in vitro and in vivo proliferation of NSCs, their migration, and their differentiation towards the neuroglial cell line. It interacts with extracellular matrix components. NSCs are distributed in different CNS areas, serve as a reservoir of multipotent cells, and may be increased during CNS demyelinating diseases. EGF has pleiotropic differentiative and proliferative effects on the main CNS cell types, particularly oligodendrocytes and their precursors, and astrocytes. EGF mediates the in vivo myelinotrophic effect of cobalamin on the CNS, and modulates the synthesis and levels of CNS normal prions (PrPCs), both of which are indispensable for myelinogenesis and myelin maintenance. EGF levels are significantly lower in the cerebrospinal fluid and spinal cord of patients with multiple sclerosis (MS), which probably explains remyelination failure, also because of the EGF marginal role in immunology. When repeatedly administered, EGF protects mouse spinal cord from demyelination in various experimental models of autoimmune encephalomyelitis. It would be worth further investigating the role of EGF in the pathogenesis of MS because of its multifarious effects.

Astrocyte and Oligodendrocyte Responses From the Subventricular Zone After Injury

Under normal conditions, neural stem cells (NSCs or B cells) in the adult subventricular zone (SVZ) give rise to amplifying neural progenitor cells (NPCs or C cells), which can produce neuroblasts (or A cells) that migrate to the olfactory bulb and differentiate into new neurons. However, following brain injury, these cells migrate toward the injury site where they differentiate into astrocytes and oligodendrocytes. In this review, we will focus on recent findings that chronicle how astrocytes and oligodendrocytes derived from SVZ-NSCs respond to different types of injury. We will also discuss molecular regulators of SVZ-NSC proliferation and their differentiation into astrocytes and oligodendrocytes. Overall, the goal of this review is to highlight how SVZ-NSCs respond to injury and to summarize the regulatory mechanisms that oversee their glial response. These molecular and cellular processes will provide critical insights needed to develop strategies to promote brain repair following injury using SVZ-NSCs.

Danzhi Xiaoyao Powder Promotes Neuronal Regeneration by Downregulating Notch Signaling Pathway in the Treatment of Generalized Anxiety Disorder

Background: Generalized anxiety disorder (GAD) is one of the most common types of anxiety disorders with unclear pathogenesis. Our team's previous research found that extensive neuronal apoptosis and neuronal regeneration disorders occur in the hippocampus of GAD rats. Danzhi Xiaoyao (DZXYS) Powder can improve the anxiety behavior of rats, but its molecular mechanism is not well understood. Objective: This paper discusses whether the pathogenesis of GAD is related to the abnormal expression of Notch signal pathway, and whether the anti-anxiety effect of DZXYS promotes nerve regeneration in the hippocampus by regulating the Notch signaling pathway. Methods: The animal model of GAD was developed by the chronic restraint stress and uncertain empty bottle stimulation method. After the model was successfully established, the rats in the model preparation group were divided into the buspirone, DZXYS, DZXYS + DAPT, and model groups, and were administered the corresponding drug intervention. The changes in body weight and food intake of rats were continuously monitored throughout the process. The changes in anxiety behavior of rats were measured by open field experiment and elevated plus-maze test, and morphological changes and regeneration of neurons in the rat hippocampus were observed by HE staining and double immunofluorescence staining. Changes in the expression of key targets of the Notch signaling pathway in the hippocampus were monitored by real-time fluorescence quantitative PCR and western blotting. Results: In this study, we verified that the GAD model was stable and reliable, and found that the key targets of the Notch signaling pathway (Notch1, Hes1, Hes5, etc.) in the hippocampus of GAD rats were significantly upregulated, leading to the increased proliferation of neural stem cells in the hippocampus and increased differentiation into astrocytes, resulting in neuronal regeneration. DZXYS intervention in GAD rats can improve appetite, promote weight growth, and significantly reverse the anxiety behavior of GAD rats, which can inhibit the upregulation of key targets of the Notch signaling pathway, promote the differentiation of neural stem cells in the hippocampus into neurons, and inhibit their differentiation into astrocytes, thus alleviating anxiety behavior. Conclusion: The occurrence of GAD is closely related to the upregulation of the Notch signaling pathway, which hinders the regeneration of normal neurons in the hippocampus, while DZXYS can downregulate the Notch signaling pathway and promote neuronal regeneration in the hippocampus, thereby relieving anxiety behavior.

Effect and mechanism of propranolol on promoting osteogenic differentiation and early implant osseointegration

The present study aimed to investigate the effect of β‑receptor blocker propranolol on early osseointegration of pure titanium implants and the underlying molecular regulatory mechanisms. An implant osseointegration model using the tibial metaphysis of New Zealand rabbits was established. The rabbits were divided into control and low‑, medium‑ and high‑dose propranolol groups. The formation of implant osseointegration was detected by X‑ray scanning. Mesenchymal stem cells (MSCs) and osteoblasts (OBs) were isolated and cultured in vitro, isoproterenol was supplemented to simulate sympathetic action and propranolol was subsequently administrated. The effect of propranolol on cell proliferation and osteogenic differentiation were assessed by EdU, flow cytometry, alizarin red staining and alkaline phosphatase (ALP) detection. The expression levels of bone morphogenetic protein (BMP)2, RUNX family transcription factor (RunX)2, collagen (COL)‑1, osteocalcin (OCN) and β2‑adrenergic receptor (AR) were detected by immunofluorescence, reverse transcription‑quantitative PCR and western blot assay. Propranolol effectively promoted implant osseointegration in vivo, facilitated proliferation of OBs, inhibited proliferation of MSCs and enhanced osteogenic differentiation of OBs and MSCs. The calcium content and ALP activity of cells treated with propranolol were markedly higher than in the control group. Propranolol also elevated mRNA and protein expression levels of BMP2, RunX2, COL‑1 and OCN in tissue and cells, and decreased the expression of β2‑AR. The present study demonstrated that the β‑receptor blocker propranolol promoted osteogenic differentiation of OBs and MSCs and enhanced implant osseointegration. The present study provided a novel insight into the application and regulatory mechanisms of propranolol.

Nkx6.1 enhances neural stem cell activation and attenuates glial scar formation and neuroinflammation in the adult injured spinal cord

Nkx6.1 plays an essential role during the embryonic development of the spinal cord. However, its role in the adult and injured spinal cord is not well understood. Here we show that lentivirus-mediated Nkx6.1 expression in the adult injured mouse spinal cord promotes cell proliferation and activation of endogenous neural stem/progenitor cells (NSPCs) at the acute phase of injury. In the chronic phase, Nkx6.1 increases the number of interneurons, reduces the number of reactive astrocytes, minimizes glial scar formation, and represses neuroinflammation. Transcriptomic analysis reveals that Nkx6.1 upregulates the sequential expression of genes involved in cell proliferation, neural differentiation, and Notch signaling pathway, downregulates genes and pathways involved in neuroinflammation, reactive astrocyte activation, and glial scar formation. Together, our findings support the potential role of Nkx6.1 in neural regeneration in the adult injured spinal cord.

Interleukin-17A promotes the differentiation of bone marrow mesenchymal stem cells into neuronal cells

Ischemia or hemorrhagic stroke is one of the leading causes of death and permanent disability in the worldwide population. As a consequence of the potential increasing in stroke, stem cell therapy is currently an area of intense focus. However, there are less data available regarding the promotion of healing efficacy after stroke. The present study aimed to investigate whether the cytokine interleukin-17A (IL-17A) could have a role in promoting the neuronal differentiation of mesenchymal stem cells (MSCs) and to investigate the associated molecular mechanism. Firstly, different concentration of IL-17A at range from 5-40 ng/mL was applied to stimulate bone marrow MSCs (BMSCs) during the course of neurogenic differentiation. Then reverse transcription-PCR, histological analyses and immunofluorescence assays were used to determine the optimum concentration of IL-17A in promoting the neuronal differentiation of BMSCs, which was 20 ng/mL. Mechanistically, Wnt signaling pathway was activated and Notch signaling pathway was suppressed. In addition, there were antergic effect of these two signaling pathways modulating the neurogenic differentiation of BMSCs induced by IL-17A. The present study demonstrated the potential role of IL-17A-based BMSCs strategy for promoting neuronal differentiation in vitro. However, the treatment efficacy could be considerably confirmed in animals with ischemia stroke. Therefore, a more sophisticated strategy that addresses the complicated treatment associated with stroke is needed.

A novel mouse model for the study of endogenous neural stem and progenitor cells after traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of death and disability in the US. Neural stem/progenitor cells (NSPCs) persist in the adult brain and represent a potential cell source for tissue regeneration and wound healing after injury. The Notch signaling pathway is critical for embryonic development and adult brain injury response. However, the specific role of Notch signaling in the injured brain is not well characterized. Our previous study has established a Notch1CR2-GFP reporter mouse line in which the Notch1CR2 enhancer directs GFP expression in NSPCs and their progeny. In this study, we performed closed head injury (CHI) in the Notch1CR2-GFP mice to study the response of injury-activated NSPCs. We show that CHI induces neuroinflammation, cell death, and the expression of typical TBI markers (e.g., ApoE, Il1b, and Tau), validating the animal model. In addition, CHI induces cell proliferation in GFP+ cells expressing NSPC markers, e.g., Notch1 and Nestin. A significant higher percentage of GFP+ astrocytes and GABAergic neurons was observed in the injured brain, with no significant change in oligodendrocyte lineage between the CHI and sham animal groups. Since injury is known to activate astrogliosis, our results suggest that injury-induced GFP+ NSPCs preferentially differentiate into GABAergic neurons. Our study establishes that Notch1CR2-GFP transgenic mouse is a useful tool for the study of NSPC behavior in vivo after TBI. Unveiling the potential of NSPCs response to TBI (e.g., proliferation and differentiation) will identify new therapeutic strategy for the treatment of brain trauma.

NKAP promotes renal cell carcinoma growth via AKT/mTOR signalling pathway

Renal cell carcinoma (RCC) is the seventh most common site for malignant tumours worldwide leading to a high risk of death. NKAP is a conserved nuclear protein that has critical roles in the development, maturation, and functional acquisition of T cells, iNKT cells, and cancers. But the function and underlying mechanism of NKAP in RCC is still unknown. Knockdown of NKAP by siRNA interference (siNKAP) was used to explore the roles of NAKP in human RCC cells. Here, we found that siNKAP strongly inhibited the proliferation and motility of Ketr-3 and 786-0 cells and induced cell apoptosis. Furthermore, the expression of anti-apoptotic protein Bcl2 in the siNKAP group was strongly decreased, while the expression of pro-apoptotic proteins Bax, cleaved Caspase-3, and cleaved Caspase-9 was significantly increased. Finally, to identify the potential mechanisms, we detected related proteins of the AKT/mTOR signalling pathway by western blot assay. We found that siNKAP significantly inhibited the expression of cyclin D1 and the phosphorylation of AKT and mTOR. The findings for the first time reveal that the AKT/mTOR signalling pathway is involved in the oncogenic role of NKAP in RCC, which provides an important basis for exploring the molecular regulation mechanism of RCC. SIGNIFICANCE OF THE STUDY: There is an urgent need to study the molecular mechanisms involved in RCC to promote the development of early diagnosis and more effective treatment options. This research provides an important basis for exploring the accurate regulatory mechanism of NKAP in RCC and a novel perspective to find the potential utility of NKAP inhibitors for RCC therapy.

Regulation of Cell Cycle Entry and Exit: A Single Cell Perspective

The transition between proliferating and quiescent states must be carefully regulated to ensure that cells divide to create the cells an organism needs only at the appropriate time and place. Cyclin-dependent kinases (CDKs) are critical for both transitioning cells from one cell cycle state to the next, and for regulating whether cells are proliferating or quiescent. CDKs are regulated by association with cognate cyclins, activating and inhibitory phosphorylation events, and proteins that bind to them and inhibit their activity. The substrates of these kinases, including the retinoblastoma protein, enforce the changes in cell cycle status. Single cell analysis has clarified that competition among factors that activate and inhibit CDK activity leads to the cell's decision to enter the cell cycle, a decision the cell makes before S phase. Signaling pathways that control the activity of CDKs regulate the transition between quiescence and proliferation in stem cells, including stem cells that generate muscle and neurons. © 2020 American Physiological Society. Compr Physiol 10:317-344, 2020.

The Notch pathway in CNS homeostasis and neurodegeneration

The role of the Notch signaling pathway in neural development has been well established over many years. More recent studies, however, have demonstrated that Notch continues to be expressed and active throughout adulthood in many areas of the central nervous system. Notch signals have been implicated in adult neurogenesis, memory formation, and synaptic plasticity in the adult organism, as well as linked to acute brain trauma and chronic neurodegenerative conditions. NOTCH3 mutations are responsible for the most common form of hereditary stroke, the progressive disorder cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy. Notch has also been associated with several progressive neurodegenerative diseases, including Alzheimer's disease, multiple sclerosis, and amyotrophic lateral sclerosis. Although numerous studies link Notch activity with CNS homeostasis and neurodegenerative diseases, the data thus far are primarily correlative, rather than functional. Nevertheless, the evidence for Notch pathway activity in specific neural cellular contexts is strong, and certainly intriguing, and points to the possibility that the pathway carries therapeutic promise. This article is categorized under: Nervous System Development > Flies Signaling Pathways > Cell Fate Signaling Nervous System Development > Vertebrates: General Principles.

Zebrafish as a translational regeneration model to study the activation of neural stem cells and role of their environment

The review is an overview of the current knowledge of neuronal regeneration properties in mammals and fish. The ability to regenerate the damaged parts of the nervous tissue has been demonstrated in all vertebrates. Notably, fish and amphibians have the highest capacity for neurogenesis, whereas reptiles and birds are able to only regenerate specific regions of the brain, while mammals have reduced capacity for neurogenesis. Zebrafish (Danio rerio) is a promising model of study because lesions in the brain or complete cross-section of the spinal cord are followed by an effective neuro-regeneration that successfully restores the motor function. In the brain and the spinal cord of zebrafish, stem cell activity is always able to re-activate the molecular programs required for central nervous system regeneration. In mammals, traumatic brain injuries are followed by reduced neurogenesis and poor axonal regeneration, often insufficient to functionally restore the nervous tissue, while spinal injuries are not repaired at all. The environment that surrounds the stem cell niche constituted by connective tissue and stimulating factors, including pro-inflammation molecules, seems to be a determinant in triggering stem cell proliferation and/or the trans-differentiation of connective elements (mainly fibroblasts). Investigating and comparing the neuronal regeneration in zebrafish and mammals may lead to a better understanding of the mechanisms behind neurogenesis, and the failure of the regenerative response in mammals, first of all, the role of inflammation, considered the main inhibitor of the neuronal regeneration.

Neural stem cell therapies and hypoxic-ischemic brain injury

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

Troy+ brain stem cells cycle through quiescence and regulate their number by sensing niche occupancy

The adult mouse subependymal zone provides a niche for mammalian neural stem cells (NSCs). However, the molecular signature, self-renewal potential, and fate behavior of NSCs remain poorly defined. Here we propose a model in which the fate of active NSCs is coupled to the total number of neighboring NSCs in a shared niche. Using knock-in reporter alleles and single-cell RNA sequencing, we show that the Wnt target Tnfrsf19/Troy identifies both active and quiescent NSCs. Quantitative analysis of genetic lineage tracing of individual NSCs under homeostasis or in response to injury reveals rapid expansion of stem-cell number before some return to quiescence. This behavior is best explained by stochastic fate decisions, where stem-cell number within a shared niche fluctuates over time. Fate mapping proliferating cells using a Ki67iresCreER allele confirms that active NSCs reversibly return to quiescence, achieving long-term self-renewal. Our findings suggest a niche-based mechanism for the regulation of NSC fate and number.

Genetic Pathways of Neuroregeneration in a Novel Mild Traumatic Brain Injury Model in Adult Zebrafish

Mild traumatic brain injuries (mTBIs) are one of the most prevalent neurological disorders, and humans are severely limited in their ability to repair and regenerate central nervous system (CNS) tissue postinjury. However, zebrafish (Danio rerio) maintain the remarkable ability to undergo complete and functional neuroregeneration as an adult. We wish to extend knowledge of the known mechanisms of neuroregeneration by analyzing the differentially expressed genes (DEGs) in a novel adult zebrafish model of mTBI. In this study, a rodent weight drop model of mTBI was adapted to the adult zebrafish. A memory test showed significant deficits in spatial memory in the mTBI group. We identified DEGs at 3 and 21 days postinjury (dpi) through RNA-sequencing analysis. The resulting DEGs were categorized according to gene ontology (GO) categories. At 3 dpi, GO categories consisted of peak injury response pathways. Significantly, at 21 dpi, GO categories consisted of neuroregeneration pathways. Ultimately, these results validate a novel zebrafish model of mTBI and elucidate significant DEGs of interest in CNS injury and neuroregeneration.

Influence of hippocampal niche signals on neural stem cell functions during aging

The genesis of new neurons from neural stem cells in the adult brain offers the hope that this mechanism of plasticity can be harnessed for the treatment of brain injuries and diseases. However, neurogenesis becomes impaired during the normal course of aging; this is also the primary risk factor for most neurodegenerative diseases. The local microenvironment that regulates the function of resident neural stem cells (the "neurogenic niche") is a particularly complex network of various signaling mechanisms, rendering it especially challenging for the dissection of the control of these cells but offering the potential for the advancement of our understanding of the regulation/misregulation of neurogenesis. In this review, we examine the factors that control neurogenesis in an age-dependent manner, and we define these signals by the extrinsic mechanism through which they are presented to the neural stem cells. Secreted signals, cell-contact-dependent signals, and extracellular matrix cues all contribute to the regulation of the aging neurogenic niche and offer points of therapeutic intervention.

Activation of the Notch-1 signaling pathway may be involved in intracerebral hemorrhage-induced reactive astrogliosis in rats

OBJECTIVE Reactive astrogliosis, a key feature that is characterized by glial proliferation, has been observed in rat brains after intracerebral hemorrhage (ICH). However, the mechanisms that control reactive astrogliosis formation remain unknown. Notch-1 signaling plays a critical role in modulating reactive astrogliosis. The purpose of this paper was to establish whether Notch-1 signaling is involved in reactive astrogliosis after ICH. METHODS ICH was induced in adult male Sprague-Dawley rats via stereotactic injection of autologous blood into the right globus pallidus. N-[ N-(3,5-difluorophenacetyl)-l-alanyl]- S-phenylglycine t-butyl ester (DAPT) was injected into the lateral ventricle to block Notch-1 signaling. The rats' brains were perfused to identify proliferating cell nuclear antigen (PCNA)-positive/GFAP-positive nuclei. The expression of GFAP, Notch-1, and the activated form of Notch-1 (Notch intracellular domain [NICD]) and its ligand Jagged-1 was assessed using immunohistochemical and Western blot analyses, respectively. RESULTS Notch-1 signaling was upregulated and activated after ICH as confirmed by an increase in the expression of Notch-1 and NICD and its ligand Jagged-1. Remarkably, blockade of Notch-1 signaling with the specific inhibitor DAPT suppressed astrocytic proliferation and GFAP levels caused by ICH. In addition, DAPT improved neurological outcome after ICH. CONCLUSIONS Notch-1 signaling is a critical regulator of ICH-induced reactive astrogliosis, and its blockage may be a potential therapeutic strategy for hemorrhagic injury.

Cellular and molecular attributes of neural stem cell niches in adult zebrafish brain

Adult neurogenesis is a complex, presumably conserved phenomenon in vertebrates with a broad range of variations regarding neural progenitor/stem cell niches, cellular composition of these niches, migratory patterns of progenitors and so forth among different species. Current understanding of the reasons underlying the inter-species differences in adult neurogenic potential, the identification and characterization of various neural progenitors, characterization of the permissive environment of neural stem cell niches and other important aspects of adult neurogenesis is insufficient. In the last decade, zebrafish has emerged as a very useful model for addressing these questions. In this review, we have discussed the present knowledge regarding the neural stem cell niches in adult zebrafish brain as well as their cellular and molecular attributes. We have also highlighted their similarities and differences with other vertebrate species. In the end, we shed light on some of the known intrinsic and extrinsic factors that are assumed to regulate the neurogenic process in adult zebrafish brain. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1188-1205, 2017.

Notch1 deficiency in postnatal neural progenitor cells in the dentate gyrus leads to emotional and cognitive impairment

It is well known that Notch1 signaling plays a crucial role in embryonic neural development and adult neurogenesis. The latest evidence shows that Notch1 also plays a critical role in synaptic plasticity in mature hippocampal neurons. So far, deeper insights into the function of Notch1 signaling during the different steps of adult neurogenesis are still lacking, and the mechanisms by which Notch1 dysfunction is associated with brain disorders are also poorly understood. In the current study, we found that Notch1 was highly expressed in the adult-born immature neurons in the hippocampal dentate gyrus. Using a genetic approach to selectively ablate Notch1 signaling in late immature precursors in the postnatal hippocampus by cross-breeding doublecortin (DCX)⁺ neuron-specific proopiomelanocortin (POMC)-α Cre mice with floxed Notch1 mice, we demonstrated a previously unreported pivotal role of Notch1 signaling in survival and function of adult newborn neurons in the dentate gyrus. Moreover, behavioral and functional studies demonstrated that POMC-Notch1^-/- mutant mice showed anxiety and depressive-like behavior with impaired synaptic transmission properties in the dentate gyrus. Finally, our mechanistic study showed significantly compromised phosphorylation of cAMP response element-binding protein (CREB) in Notch1 mutants, suggesting that the dysfunction of Notch1 mutants is associated with the disrupted pCREB signaling in postnatally generated immature neurons in the dentate gyrus.-Feng, S., Shi, T., Qiu, J., Yang, H., Wu, Y., Zhou, W., Wang, W., Wu, H. Notch1 deficiency in postnatal neural progenitor cells in the dentate gyrus leads to emotional and cognitive impairment.

Attenuation of opioid tolerance by ETB receptor agonist, IRL-1620, is independent of an accompanied decrease in nerve growth factor in mice

AIM

ET_A receptor antagonists reverse opioid tolerance but the involvement of ET_B receptors is unknown. In morphine or oxycodone tolerant mice we investigated (1) the effect of ET_B receptor agonist, IRL-1620, on analgesic tolerance; (2) changes in expression of the brain ET_A and ET_B receptors; and (3) alterations in the brain VEGF, NGF, PI3K and notch-1 expression.

MAIN METHODS

Body weight, body temperature, and tail-flick latency were assessed before and after a challenge dose of morphine or oxycodone in vehicle or IRL-1620 treated mice. Expression studies were carried out using Western blots.

KEY FINDINGS

Tail flick latency to a challenge dose of opioid was significantly increased by IRL-1620 from 39% to 100% in morphine tolerant and from 8% to 83% in oxycodone tolerant mice. Morphine or oxycodone did not alter ET_A or ET_B receptor expression. IRL-1620 had no effect on ET_A however it increased (61%) expression of ET_B receptors. IRL-1620-induced increase in ET_B receptor expression was attenuated by morphine (39.8%) and oxycodone (51.8%). VEGF expression was not affected by morphine or oxycodone and was unaltered by IRL-1620. However, NGF and PI3K expression was decreased (P < 0.001) by morphine and oxycodone and was unaffected by IRL-1620. Notch-1 expression was not altered by morphine, oxycodone or IRL-1620.

SIGNIFICANCE

ET_B receptor agonist, IRL-1620, restored analgesic tolerance to morphine and oxycodone, but it did not affect morphine and oxycodone induced decrease in NGF/PI3K expression. It is concluded that IRL-1620 attenuates opioid tolerance without the involvement of NGF/PI3K pathway.

Olfactory Ensheathing Cells Inhibit Gliosis in Retinal Degeneration by Downregulation of the Müller Cell Notch Signaling Pathway

Retinal regeneration and self-repair, whether in response to injury or degenerative disease, are severely impeded by glial scar formation by Müller cells (specialized retinal macroglia). We have previously demonstrated that the activation of Müller cells and gliosis in the degenerative retina are significantly suppressed by the subretinal transplantation of a mixture of olfactory ensheathing cells (OECs) and olfactory nerve fibroblasts. However, the underlying molecular mechanism has remained elusive. Here we transplanted purified rat OECs into the subretinal space of pigmented Royal College of Surgeons (RCS) rats, a classic rodent model of retinal degeneration. Using behavioral testing and electroretinography, we confirmed that the grafted OECs preserved the visual function of rats for 8 weeks, relative to vehicle controls (phosphate-buffered saline). Histological evaluation of outer nuclear layer thickness and composition demonstrated that more photoreceptors and ON-bipolar cells were preserved in the retinas of OEC-treated RCS rats than in controls. The grafted OECs migrated into the outer plexiform layer, inner nuclear layer, and inner plexiform layer. They interacted directly with Müller cells in the retina of RCS rats, in three distinct patterns, and secreted matrix metalloproteinases 2 and 3. Previous studies have demonstrated that rat OECs express delta-like ligand (DLL), while Müller cells express Notch3, the receptor for DLL. Here we found that the grafted OECs significantly decreased the expression, by retinal cells, of Notch signaling pathway components (including Notch3, Notch4, DLL1, DLL4, Jagged1, Hes1, and Hes5) 2 weeks after the cell transplantation and that this effect persisted for a further 2 weeks. Based on these findings, we suggest that transplanted OECs inhibit the activation of Müller cells and the associated gliosis, at least partly through suppression of the Notch pathway.

Pharmacological approaches to intervention in hypomyelinating and demyelinating white matter pathology

White matter disease afflicts both developing and mature central nervous systems. Both cell intrinsic and extrinsic dysregulation result in profound changes in cell survival, axonal metabolism and functional performance. Experimental models of developmental white matter (WM) injury and demyelination have not only delineated mechanisms of signaling and inflammation, but have also paved the way for the discovery of pharmacological approaches to intervention. These reagents have been shown to enhance protection of the mature oligodendrocyte cell, accelerate progenitor cell recruitment and/or differentiation, or attenuate pathological stimuli arising from the inflammatory response to injury. Here we highlight reports of studies in the CNS in which compounds, namely peptides, hormones, and small molecule agonists/antagonists, have been used in experimental animal models of demyelination and neonatal brain injury that affect aspects of excitotoxicity, oligodendrocyte development and survival, and progenitor cell function, and which have been demonstrated to attenuate damage and improve WM protection in experimental models of injury. The molecular targets of these agents include growth factor and neurotransmitter receptors, morphogens and their signaling components, nuclear receptors, as well as the processes of iron transport and actin binding. By surveying the current evidence in non-immune targets of both the immature and mature WM, we aim to better understand pharmacological approaches modulating endogenous oligodendroglia that show potential for success in the contexts of developmental and adult WM pathology. This article is part of the Special Issue entitled 'Oligodendrocytes in Health and Disease'.

Notch signaling in cerebrovascular diseases (Review)

The Notch signaling pathway is a crucial regulator of numerous fundamental cellular processes. Increasing evidence suggests that Notch signaling is involved in inflammation and oxidative stress, and thus in the progress of cerebrovascular diseases. In addition, Notch signaling in cerebrovascular diseases is associated with apoptosis, angiogenesis and the function of blood-brain barrier. Despite the contradictory results obtained to date as to whether Notch signaling is harmful or beneficial, the regulation of Notch signaling may provide a novel strategy for the treatment of cerebrovascular diseases.

Traumatic Brain Injury Activation of the Adult Subventricular Zone Neurogenic Niche

Traumatic brain injury (TBI) is common in both civilian and military life, placing a large burden on survivors and society. However, with the recognition of neural stem cells in adult mammals, including humans, came the possibility to harness these cells for repair of damaged brain, whereas previously this was thought to be impossible. In this review, we focus on the rodent adult subventricular zone (SVZ), an important neurogenic niche within the mature brain in which neural stem cells continue to reside. We review how the SVZ is perturbed following various animal TBI models with regards to cell proliferation, emigration, survival, and differentiation, and we review specific molecules involved in these processes. Together, this information suggests next steps in attempting to translate knowledge from TBI animal models into human therapies for TBI.

Persistent Gliosis Interferes with Neurogenesis in Organotypic Hippocampal Slice Cultures

Neurogenesis in the adult hippocampus has become an intensively investigated research topic, as it is essential for proper hippocampal function and considered to bear therapeutic potential for the replacement of pathologically lost neurons. On the other hand, neurogenesis itself is frequently affected by CNS insults. To identify processes leading to the disturbance of neurogenesis, we made use of organotypic hippocampal slice cultures (OHSC), which, for unknown reasons, lose their neurogenic potential during cultivation. In the present study, we show by BrdU/Prox1 double-immunostaining that the generation of new granule cells drops by 90% during the first week of cultivation. Monitoring neurogenesis dynamically in OHSC from POMC-eGFP mice, in which immature granule cells are endogenously labeled, revealed a gradual decay of the eGFP signal, reaching 10% of initial values within 7 days of cultivation. Accordingly, reverse transcription quantitative polymerase chain reaction analysis showed the downregulation of the neurogenesis-related genes doublecortin and Hes5, a crucial target of the stem cell-maintaining Notch signaling pathway. In parallel, we demonstrate a strong and long-lasting activation of astrocytes and microglial cells, both, morphologically and on the level of gene expression. Enhancement of astroglial activation by treating OHSC with ciliary neurotrophic factor accelerated the loss of neurogenesis, whereas treatment with indomethacin or an antagonist of the purinergic P2Y12 receptor exhibited potent protective effects on the neurogenic outcome. Therefore, we conclude that OHSC rapidly lose their neurogenic capacity due to persistent inflammatory processes taking place after the slice preparation. As inflammation is also considered to affect neurogenesis in many CNS pathologies, OHSC appear as a useful tool to study this interplay and its molecular basis. Furthermore, we propose that modification of glial activation might bear the therapeutic potential of enabling neurogenesis under neuropathological conditions.

The Adult Ventricular-Subventricular Zone (V-SVZ) and Olfactory Bulb (OB) Neurogenesis

A large population of neural stem/precursor cells (NSCs) persists in the ventricular-subventricular zone (V-SVZ) located in the walls of the lateral brain ventricles. V-SVZ NSCs produce large numbers of neuroblasts that migrate a long distance into the olfactory bulb (OB) where they differentiate into local circuit interneurons. Here, we review a broad range of discoveries that have emerged from studies of postnatal V-SVZ neurogenesis: the identification of NSCs as a subpopulation of astroglial cells, the neurogenic lineage, new mechanisms of neuronal migration, and molecular regulators of precursor cell proliferation and migration. It has also become evident that V-SVZ NSCs are regionally heterogeneous, with NSCs located in different regions of the ventricle wall generating distinct OB interneuron subtypes. Insights into the developmental origins and molecular mechanisms that underlie the regional specification of V-SVZ NSCs have also begun to emerge. Other recent studies have revealed new cell-intrinsic molecular mechanisms that enable lifelong neurogenesis in the V-SVZ. Finally, we discuss intriguing differences between the rodent V-SVZ and the corresponding human brain region. The rapidly expanding cellular and molecular knowledge of V-SVZ NSC biology provides key insights into postnatal neural development, the origin of brain tumors, and may inform the development regenerative therapies from cultured and endogenous human neural precursors.

The Role of Astrocytes in the Generation, Migration, and Integration of New Neurons in the Adult Olfactory Bulb

In mammals, new neurons in the adult olfactory bulb originate from a pool of neural stem cells in the subventricular zone of the lateral ventricles. Adult-born cells play an important role in odor information processing by adjusting the neuronal network to changing environmental conditions. Olfactory bulb neurogenesis is supported by several non-neuronal cells. In this review, we focus on the role of astroglial cells in the generation, migration, integration, and survival of new neurons in the adult forebrain. In the subventricular zone, neural stem cells with astrocytic properties display regional and temporal specificity when generating different neuronal subtypes. Non-neurogenic astrocytes contribute to the establishment and maintenance of the neurogenic niche. Neuroblast chains migrate through the rostral migratory stream ensheathed by astrocytic processes. Astrocytes play an important regulatory role in neuroblast migration and also assist in the development of a vasculature scaffold in the migratory stream that is essential for neuroblast migration in the postnatal brain. In the olfactory bulb, astrocytes help to modulate the network through a complex release of cytokines, regulate blood flow, and provide metabolic support, which may promote the integration and survival of new neurons. Astrocytes thus play a pivotal role in various processes of adult olfactory bulb neurogenesis, and it is likely that many other functions of these glial cells will emerge in the near future.

Membrane receptor-dependent Notch1/Hes1 activation by melatonin protects against myocardial ischemia-reperfusion injury: in vivo and in vitro studies

Melatonin confers profound protective effect against myocardial ischemia-reperfusion injury (MI/RI). Activation of Notch1/Hairy and enhancer of split 1 (Hes1) signaling also ameliorates MI/RI. We hypothesize that melatonin attenuates MI/RI-induced oxidative damage by activating Notch1/Hes1 signaling pathway with phosphatase and tensin homolog deleted on chromosome 10 (Pten)/Akt acting as the downstream signaling pathway in a melatonin membrane receptor-dependent manner. Male Sprague Dawley rats were treated with melatonin (10 mg/kg/day) for 4 wk and then subjected to MI/R surgery. Melatonin significantly improved cardiac function and decreased myocardial apoptosis and oxidative damage. Furthermore, in cultured H9C2 cardiomyocytes, melatonin (100 μmol/L) attenuated simulated ischemia-reperfusion (SIR)-induced myocardial apoptosis and oxidative damage. Both in vivo and in vitro study demonstrated that melatonin treatment increased Notch1, Notch1 intracellular domain (NICD), Hes1, Bcl-2 expressions, and p-Akt/Akt ratio and decreased Pten, Bax, and caspase-3 expressions. However, these protective effects conferred by melatonin were blocked by DAPT (the specific inhibitor of Notch1 signaling), luzindole (the antagonist of melatonin membrane receptors), Notch1 siRNA, or Hes1 siRNA administration. In summary, our study demonstrates that melatonin treatment protects against MI/RI by modulating Notch1/Hes1 signaling in a receptor-dependent manner and Pten/Akt signaling pathways are key downstream mediators.

Isolating dividing neural and brain tumour cells for gene expression profiling

BACKGROUND

The characterisation of dividing brain cells is fundamental for studies ranging from developmental and stem cell biology, to brain cancers. Whilst there is extensive anatomical data on these dividing cells, limited gene transcription data is available due to technical constraints.

NEW METHOD

We focally isolated dividing cells whilst conserving RNA, from culture, primary neural tissue and xenografted glioma tumours, using a thymidine analogue that enables gene transcription analysis.

RESULTS

5-ethynyl-2-deoxyuridine labels the replicating DNA of dividing cells. Once labelled, cultured cells and tissues were dissociated, fluorescently tagged with a revised click chemistry technique and the dividing cells isolated using fluorescence-assisted cell sorting. RNA was extracted and analysed using real time PCR. Proliferation and maturation related gene expression in neurogenic tissues was demonstrated in acutely and 3 day old labelled cells, respectively. An elevated expression of marker and pathway genes was demonstrated in the dividing cells of xenografted brain tumours, with the non-dividing cells showing relatively low levels of expression.

COMPARISON WITH EXISTING METHOD

BrdU "immune-labelling", the most frequently used protocol for detecting cell proliferation, causes complete denaturation of RNA, precluding gene transcription analysis. This EdU labelling technique, maintained cell integrity during dissociation, minimized copper exposure during labelling and used a cell isolation protocol that avoided cell lysis, thus conserving RNA.

CONCLUSIONS

The technique conserves RNA, enabling the definition of cell proliferation-related changes in gene transcription of neural and pathological brain cells in cells harvested immediately after division, or following a period of maturation.

Effect of Acupuncture on the Notch Signaling Pathway in Rats with Brain Injury

OBJECTIVE

To observe the effect of acupuncture on the Notch signaling pathway in rats with traumatic brain injury and to explore the pathogenesis of acupuncture intervention on traumatic brain injury.

METHODS

Feeney's freefall epidural impact method was used to establish a traumatic brain injury model in rats; the rats were randomly divided into a normal group, sham operation group, model group and acupuncture group. Acupuncture was performed in the Baihui (DU 20), Shuigou (DU 26), Fengfu (DU 16), Yamen (DU 15) and Hegu (LI 4) acupoints in the rat, and Yamen was punctured via Fengfu. Then, the rats in each group were randomly divided into three subgroups, namely the day 3 subgroup, day 7 subgroup and day 14 subgroup according to treatment duration. The modified neurological severity scores (mNss) method was used to perform neurobehavioral scoring for evaluating the degree of injury in the rats. The hematoxylin-eosin (HE) staining method was used to observe the pathological change in the brain tissue of rats in each group. Real-time fluorescent quantitative polymerase chain reaction (Q-PCR) technology was used to detect changes in the Notch1, Hes1 and Hes5 gene expression levels in the cortex on the injured side. Western blot was used to detect the protein expression changes.

RESULTS

One day after modeling, the mNss scores in the model group and in the acupuncture group were significantly higher than those in the normal and sham operation groups (P<0.01) ; there was no statistically significant difference between the normal group and the sham operation group. The scores decreased with increased treatment time, and the scores in the acupuncture group decreased more significantly than those in the model group (P<0.01). The pathological examination by the HE staining method demonstrated that the brain tissue of the rats in the acupuncture and model groups relatively significantly changed. The Notch1 gene expression level in the acupuncture group was significantly higher than the level in all of the other groups (P<0.01) ; the Hes1 and Hes5 gene expression levels were also higher in the acupuncture group. The expression changes of the Notch1 and Hes1 protein were consistent with that of mRNA. In each experimental group, the mNss score and the pathological results by the HE staining method were consistent with the mRNA results.

CONCLUSION

Acupuncture could significantly promote high expression levels of Notch1, Hes1 and Hes5 in the brain tissue of traumatic brain injury rats. Therefore, acupuncture might be an important intervention for inducing endogenous stem cell proliferation and for promoting nerve repair.

Notch signaling activation is critical to the development of neuropathic pain

Background

Nerve injury-induced neuropathic pain is a major health problem worldwide. Notch signaling is a highly conserved pathway in evolution, which has an important role in synaptic plasticity and inflammation in central nervous system. The present study was designed to investigate the potential role of notch signaling in the development of neuropathic pain.

Methods

The neuropathic pain was induced by spared nerve injury (SNI) in rats. The activation of notch signaling in the lumbar spinal dorsal horn was measured. DAPT, an inhibitor of notch signaling, was intrathecally (i.t.) administered before SNI or after appearance of pain sensitivity. Moreover, Jagged-1 (JAG-1) peptide, a ligand of notch signaling, was i.t. administered to normal rats. The mechanical allodynia was assessed by von Frey test.

Results

Here, we found that DAPT administered 0.5 h before SNI operation could significantly prevent the decrease of mechanical paw withdrawal threshold (PWT) for more than 4 weeks (P < 0.05 vs. SNI group). DAPT administered after appearance of pain sensitivity could also significantly reverse the decrease of mechanical PWT in a dose-dependent manner (P < 0.05). In addition, administration of Jagged-1 (JAG-1) peptide significantly decreased the mechanical PWT of normal rats in a dose-dependent manner (P < 0.05).

Conclusions

Therefore, notch signaling activation might contribute to the development of neuropathic pain. This study might provide a new therapeutic target for neuropathic pain.

The Roles of the Stem Cell-Controlling Sox2 Transcription Factor: from Neuroectoderm Development to Alzheimer's Disease?

Sox2 is a component of the core transcriptional regulatory network which maintains the totipotency of the cells during embryonic preimplantation period, the pluripotency of embryonic stem cells, and the multipotency of neural stem cells. This maintenance is controlled by internal loops between Sox2 and other transcription factors of the core such as Oct4, Nanog, Dax1, and Klf4, downstream proteins of extracellular ligands, epigenetic modifiers, and miRNAs. As Sox2 plays an important role in the balance between stem cells maintenance and commitment to differentiated lineages throughout the lifetime, it is supposed that Sox2 could regulate stem cells aging processes. In this review, we provide an update concerning the involvement of Sox2 in neurogenesis during normal aging and discuss its possible role in Alzheimer's disease.

Dysfunction of platelet-derived growth factor receptor α (PDGFRα) represses the production of oligodendrocytes from arylsulfatase A-deficient multipotential neural precursor cells

The membrane-bound receptor for platelet-derived growth factor A (PDGFRα) is crucial for controlling the production of oligodendrocytes (OLs) for myelination, but regulation of its activity during OL differentiation is largely unknown. We have examined the effect of increased sulfated content of galactosylceramides (sulfatides) on the regulation of PDGFRα in multipotential neural precursors (NPs) that are deficient in arylsulfatase A (ASA) activity. This enzyme is responsible for the lysosomal hydrolysis of sulfatides. We show that sulfatide accumulation significantly impacts the formation of OLs via deregulation of PDGFRα function. PDGFRα is less associated with detergent-resistant membranes in ASA-deficient cells and showed a significant decrease in AKT phosphorylation. Rescue experiments with ASA showed a normalization of the ratio of long versus short sulfatides, restored PDGFRα levels, corrected its localization to detergent-resistant membranes, increased AKT phosphorylation, and normalized the production of OLs in ASA-deficient NPs. Moreover, our studies identified a novel mechanism that regulates the secretion of PDGFRα in NPs, in glial cells, and in the brain cortex via exosomal shedding. Our study provides a first step in understanding the role of sulfatides in regulating PDGFRα levels in OLs and its impact in myelination.

Hes1 is upregulated by ischemic postconditioning and contributes to cardioprotection

The expression of Hes1 is increased following myocardial infarct and other ischemic cardiomyopathies, but the role of Hes1 in cardioprotection provided by ischemic postconditioning (IPost) remains unclear. In this study, we used gain and loss of function approaches to investigate the role of Hes1 in cardioprotection during IPost. Primary cardiac myocytes exposed to ischemia reperfusion injury (IRI) and IPost were used as the experimental model. The results showed that Hes1 expression was increased during myocardial IPost, and Hes1 promoted the viability while inhibited the apoptosis of cardiomyocytes. Moreover, Hes1 inhibited the opening of mitochondrial permeability transition pore (mPTP) and the generation of reactive oxygen species in primary cardiac myocytes exposed to IRI. Mechanistically, we found that Hes1-mediated cardioprotection was related to the downregulation of phosphatase and tensin homolog and the activation of phosphatidylinositol 3-kinase/Akt and signal transducer and activator of transcription 3 signalling. These data demonstrate that Hes1 is upregulated and mediates cardioprotection provided by IPost and suggest that Hes1 is a potential new target for the treatment of ischemic cardiomyopathy.

βA3/A1-crystallin: more than a lens protein

Crystallins, the highly abundant proteins of the ocular lens, are essential determinants of the transparency and refractivity required for lens function. Initially thought to be lens-specific and to have evolved as lens proteins, it is now clear that crystallins were recruited to the lens from proteins that existed before lenses evolved. Crystallins are expressed outside of the lens and most have been shown to have cellular functions distinct from their roles as structural elements in the lens. For one major crystallin group, the β/γ-crystallin superfamily, no such functions have yet been established. We have explored possible functions for the polypeptides (βA3-and βA1-crystallins) encoded by Cryba1, one of the 6 β-crystallin genes, using a spontaneous rat mutant and genetically engineered mouse models. βA3-and βA1-crystallins are expressed in retinal astrocytes and retinal pigment epithelial (RPE) cells. In both cell types, these proteins appear to be required for the proper acidification of the lysosomes. In RPE cells, elevated pH in the lysosomes is shown to impair the critical processes of phagocytosis and autophagy, leading to accumulation of undigested cargo in (auto) phagolysosomes. We postulate that this accumulation may cause pathological changes in the cells resembling some of those characteristic of age-related macular degeneration (AMD). Our studies suggest an important regulatory function of βA3/A1-crystallin in astrocytes. We provide evidence that the cellular function of βA3/A1-crystallin involves its interaction with V-ATPase, the proton pump responsible for acidification of the endolysosomal system.

Increased expression of Notch1 in temporal lobe epilepsy: animal models and clinical evidence

Temporal lobe epilepsy is associated with astrogliosis. Notch1 signaling can induce astrogliosis in glioma. However, it remains unknown whether Notch1 signaling is involved in the pathogenesis of epilepsy. This study investigated the presence of Notch1, hairy and enhancer of split-1, and glial fibrillary acidic protein in the temporal neocortex and hippocampus of lithium-pilocarpine-treated rats. The presence of Notch1 and hairy and enhancer of split-1 was also explored in brain tissues of patients with intractable temporal lobe epilepsy. Quantitative electroencephalogram analysis and behavioral observations were used as auxiliary measures. Results revealed that the presence of Notch1, hairy and enhancer of split-1, and glial fibrillary acidic protein were enhanced in status epilepticus and vehicle-treated spontaneous recurrent seizures rats, but remain unchanged in the following groups: control, absence of either status epilepticus or spontaneous recurrent seizures, and zileuton-treated spontaneous recurrent seizures. Compared with patient control cases, the presences of Notch1 and hairy and enhancer of split-1 were upregulated in the temporal neocortex of patients with intractable temporal lobe epilepsy. Therefore, these results suggest that Notch1 signaling may play an important role in the onset of temporal lobe epilepsy via astrogliosis. Furthermore, zileuton may be a potential therapeutic strategy for temporal lobe epilepsy by blocking Notch1 signaling.

Influence of the extracellular matrix on endogenous and transplanted stem cells after brain damage

The limited regeneration capacity of the adult central nervous system (CNS) requires strategies to improve recovery of patients. In this context, the interaction of endogenous as well as transplanted stem cells with their environment is crucial. An understanding of the molecular mechanisms could help to improve regeneration by targeted manipulation. In the course of reactive gliosis, astrocytes upregulate Glial fibrillary acidic protein (GFAP) and start, in many cases, to proliferate. Beside GFAP, subpopulations of these astroglial cells coexpress neural progenitor markers like Nestin. Although cells express these markers, the proportion of cells that eventually give rise to neurons is limited in many cases in vivo compared to the situation in vitro. In the first section, we present the characteristics of endogenous progenitor-like cells and discuss the differences in their neurogenic potential in vitro and in vivo. As the environment plays an important role for survival, proliferation, migration, and other processes, the second section of the review describes changes in the extracellular matrix (ECM), a complex network that contains numerous signaling molecules. It appears that signals in the damaged CNS lead to an activation and de-differentiation of astrocytes, but do not effectively promote neuronal differentiation of these cells. Factors that influence stem cells during development are upregulated in the damaged brain as part of an environment resembling a stem cell niche. We give a general description of the ECM composition, with focus on stem cell-associated factors like the glycoprotein Tenascin-C (TN-C). Stem cell transplantation is considered as potential treatment strategy. Interaction of transplanted stem cells with the host environment is critical for the outcome of stem cell-based therapies. Possible mechanisms involving the ECM by which transplanted stem cells might improve recovery are discussed in the last section.

A self-organizing miR-132/Ctbp2 circuit regulates bimodal notch signals and glial progenitor fate choice during spinal cord maturation

Radial glial progenitors play pivotal roles in the development and patterning of the spinal cord, and their fate is controlled by Notch signaling. How Notch is shaped to regulate their crucial transition from expansion toward differentiation remains, however, unknown. miR-132 in the developing zebrafish dampens Notch signaling via a cascade involving the transcriptional corepressor Ctbp2 and the Notch suppressor Sirt1. At early embryonic stages, high Ctbp2 levels sustain Notch signaling and radial glial expansion and concomitantly induce miR-132 expression via a double-negative feedback loop involving Rest inhibition. The changing balance in miR-132 and Ctbp2 interaction gradually drives the switch in Notch output and radial glial progenitor fate as part of the larger developmental program involved in the transition from embryonic to larval spinal cord.

Excitotoxic brain injury in adult zebrafish stimulates neurogenesis and long-distance neuronal integration

Zebrafish maintain a greater capacity than mammals for central nervous system repair after injury. Understanding differences in regenerative responses between different vertebrate species may shed light on mechanisms to improve repair in humans. Quinolinic acid is an excitotoxin that has been used to induce brain injury in rodents for modeling Huntington's disease and stroke. When injected into the adult rodent striatum, this toxin stimulates subventricular zone neurogenesis and neuroblast migration to injury. However, most new neurons fail to survive and lesion repair is minimal. We used quinolinic acid to lesion the adult zebrafish telencephalon to study reparative processes. We also used conditional transgenic lineage mapping of adult radial glial stem cells to explore survival and integration of neurons generated after injury. Telencephalic lesioning with quinolinic acid, and to a lesser extent vehicle injection, produced cell death, microglial infiltration, increased cell proliferation, and enhanced neurogenesis in the injured hemisphere. Lesion repair was more complete with quinolinic acid injection than after vehicle injection. Fate mapping of her4-expressing radial glia showed injury-induced expansion of radial glial stem cells that gave rise to neurons which migrated to injury, survived at least 8 weeks and formed long-distance projections that crossed the anterior commissure and synapsed in the contralateral hemisphere. These findings suggest that quinolinic acid lesioning of the zebrafish brain stimulates adult neural stem cells to produce robust regeneration with long-distance integration of new neurons. This model should prove useful for elucidating reparative mechanisms that can be applied to restorative therapies for mammalian brain injury.