神经干细胞迁移的研究进展

神经干细胞的定向迁移是胚胎神经系统发育的先决条件,同时在成体组织的许多生理、病理过程中也起着重要作用;研究发现,许多神经退行性疾病都与神经干细胞迁移的缺陷相关。近年来,越来越多的证据表明,无论是内源性的还是移植的神经干细胞都有向大脑损伤部位迁移的特性,显示出神经干细胞用于神经再生及损伤修复治疗的潜能。该文着重在神经干细胞的基本特性以及神经干细胞定向迁移的细胞与分子机制研究等方面进行了综述。     

Copine1 regulates neural stem cell functions during brain development

Copine 1 (CPNE1) is a well-known phospholipid binding protein in plasma membrane of various cell types. In brain cells, CPNE1 is closely associated with AKT signaling pathway, which is important for neural stem cell (NSC) functions during brain development. Here, we investigated the role of CPNE1 in the regulation of brain NSC functions during brain development and determined its underlying mechanism. In this study, abundant expression of CPNE1 was observed in neural lineage cells including NSCs and immature neurons in human. With mouse brain tissues in various developmental stages, we found that CPNE1 expression was higher at early embryonic stages compared to postnatal and adult stages. To model developing brain in vitro, we used primary NSCs derived from mouse embryonic hippocampus. Our in vitro study shows decreased proliferation and multi-lineage differentiation potential in CPNE1 deficient NSCs. Finally, we found that the deficiency of CPNE1 downregulated mTOR signaling in embryonic NSCs. These data demonstrate that CPNE1 plays a key role in the regulation of NSC functions through the activation of AKT-mTOR signaling pathway during brain development.     

Molecular and clinical characterization of Galectin-9 in glioma through 1,027 samples

In recent years, research on glioma immunotherapy have grown rapidly. However, the autoimmune-like side effects that are caused by blocking immunological checkpoints hinder their clinical application in gliomas currently. Galectin-9, a ligand for T-cell immunoglobulin mucin 3, has shed a new light on the treatment of malignant glioma. However, the potential mechanism of Galectin-9 is still under discussion. In this study, first, we methodically gathered 1,027 glioma patients with RNA-seq and 986 patients with survival data to explore the role and mechanism of Galectin-9 in gliomas. Second, we analyzed glioma samples from 50 patients in the Department of Neurosurgery, Tianjin Medical University General Hospital. Finally, we found that Galectin-9 was strongly upregulated in glioblastoma multiforme compared with normal brain tissues and lower-grade glioma. Patients with Galectin-9 overexpression had a significantly shorter overall survival. Moreover, the tissue microarray data displayed that the expression of Galectin-9 in the core of tumor is higher than that in the border and was correlated with the shorter survival in glioma patients. Galectin-9 is more highly expressed in the mesenchymal subtype of glioblastoma multiforme than in the other subtypes. Simultaneously, Galectin-9 was closely associated with the immune response and lymphocyte activation, especially T-cell activation. To further determine the underlying role of Galectin-9 in the immune response, we selected seven immune metagenes. Through cluster analysis and correlation analysis, we discovered that Galectin-9 was highly correlated with immune checkpoint molecules and M2 tumor-associated macrophages. In summary, Galectin-9 serves as a potential therapeutic target to treat glioblastoma multiforme.     

Adult periventricular neural stem cells: outstanding progress and outstanding issues

Twenty years have past since the existence of neural stem cells (NSCs) within the walls of the adult lateral ventricles was discovered. During this period of time, great strides have been made in every facet of our understanding of this adult periventricular NSC population. In this review, some of the fields' major advancements regarding the nature and function of adult periventricular NSCs are examined. We bring attention to issues related to NSC identity, potential, and the role of Notch signaling in regulating quiescence and activation that warrant further investigation. Progress in the understanding of human adult NSCs will aid in the development of tools required to advance therapies not only for brain repair after injury or disease but may also lead to novel therapeutics for brain tumors.     

Identification,characterization, and functional investigation of circular RNAs in subventricular zone of adult rat brain

Adult neural stem cells (NSCs) are able to self-renew and generate new neural cells. Identifying regulators of NSCs is significant for the development of NSC-based therapies for neurodegenerative diseases and brain injuries. Recently, circular RNAs (circRNAs) have been characterized in various cell lines and brain tissues, and found to participate in multiple biological processes. However, the expression pattern of circRNAs in adult NSCs is still unknown. Here, the subventricular zone (SVZ) of the lateral ventricle was isolated as the niche of NSCs in adult rat brain for RNA sequencing and the characteristics of circRNAs profiling in both SVZ and cerebral cortex were also investigated. As a result, 29 049 and 31 975 circRNAs were identified in SVZ and cortex, respectively. Among them, 41 were SVZ-specific and 48 were cortex-specific. 467 circRNAs were also found to express predominately in SVZ, while the cortex had other 423 circRNAs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that the SVZ-specific circRNAs have close relationship with the regulation of NSC expansion and NSC-niche interaction, while the other differentially expressed circRNAs might be involved in neural cellular construction and nerve system function. Furthermore, the interactions between circRNAs and microRNAs were also explored, and the result showed that one SVZ-specific circRNA was capable to competitively bind miR-138-5p as a potential derepressive regulator in NSCs proliferation. Hence, our work has laid the foundations to decipher regulation mechanisms of circRNAs in adult NSCs and to develop circRNAs as novel biomarkers for adult NSCs.     

The Nuclear Receptor TLX Is Required for Gliomagenesis within the Adult Neurogenic Niche

Neural stem cells (NSCs) continually generate functional neurons in the adult brain. Due to their ability to proliferate, deregulated NSCs or their progenitors have been proposed as the cells of origin for a number of primary central nervous system neoplasms, including infiltrating gliomas. The orphan nuclear receptor TLX is required for proliferation of adult NSCs, and its upregulation promotes brain tumor formation. However, it is unknown whether TLX is required for gliomagenesis. We examined the genetic interactions between TLX and several tumor suppressors, as well as the role of TLX-dependent NSCs during gliomagenesis, using mouse models. Here, we show that TLX is essential for the proliferation of adult NSCs with a single deletion of p21, p53, or Pten or combined deletion of Pten and p53. While brain tumors still form in Tlx mutant mice, these tumors are less infiltrative and rarely associate with the adult neurogenic niches, suggesting a non-stem-cell origin. Taken together, these results indicate a critical role for TLX in NSC-dependent gliomagenesis and implicate TLX as a therapeutic target to inhibit the development of NSC-derived brain tumors.     

Prospective isolation of adult neural stem cells from the mouse subependymal zone

Neural stem cells (NSCs) have the remarkable capacity to self-renew and the lifelong ability to generate neurons in the adult mammalian brain. However, the molecular and cellular mechanisms contributing to these behaviors are still not understood. Now that prospective isolation of the NSCs has become feasible, these mechanisms can be studied. Here we describe a protocol for the efficient isolation of adult NSCs, by the application of a dual-labeling strategy on the basis of their glial identity and ciliated nature. The cells are isolated from the lateral ventricular subependymal zone (SEZ) of adult hGFAP-eGFP (human glial fibrillary acidic protein-enhanced green fluorescent protein) transgenic mice by fluorescence-activated cell sorting. Staining against prominin1 (CD133) allows the isolation of the NSCs (hGFAP-eGFP(+)/prominin1(+)), which can be further subdivided by labeling with the fluorescent epidermal growth factor. This protocol, which can be completed in 7 h, allows the assessment of quantitative changes in SEZ NSCs and the examination of their molecular and functional characteristics.     

Jagged1 signals in the postnatal subventricular zone are required for neural stem cell self-renewal

Neural stem cells (NSCs) in the postnatal mammalian brain self-renew and are a source of neurons and glia. To date, little is known about the molecular and cellular mechanisms regulating the maintenance and differentiation of these multipotent progenitors. We show that Jagged1 is required by mitotic cells in the subventricular zone (SVZ) and stimulates self-renewal of multipotent epidermal growth factor-dependent NSCs. Jagged1-expressing cells line the adult SVZ and are juxtaposed to Notch1-expressing cells, some of which are putative NSCs. In vitro, endogenous Jagged1 acts through Notch1 to promote NSC maintenance and multipotency. In vivo, reducing Jagged1/Notch1 signaling decreases the number of proliferating cells in the SVZ. In addition, soluble Jagged1 promotes self-renewal and neurogenic potential of multipotent neural progenitors in vitro. Our findings suggest a central role for Jagged1 in the NSC niche in the SVZ for maintaining a population of NSCs in the postnatal brain.     

Tauroursodeoxycholic Acid Enhances Mitochondrial Biogenesis,Neural Stem Cell Pool,and Early Neurogenesis in Adult Rats

Although neurogenesis occurs in restricted regions of the adult mammalian brain, neural stem cells (NSCs) produce very few neurons during ageing or after injury. We have recently discovered that the endogenous bile acid tauroursodeoxycholic acid (TUDCA), a strong inhibitor of mitochondrial apoptosis and a neuroprotective in animal models of neurodegenerative disorders, also enhances NSC proliferation, self-renewal, and neuronal conversion by improving mitochondrial integrity and function of NSCs. In the present study, we explore the effect of TUDCA on regulation of NSC fate in neurogenic niches, the subventricular zone (SVZ) of the lateral ventricles and the hippocampal dentate gyrus (DG), using rat postnatal neurospheres and adult rats exposed to the bile acid. TUDCA significantly induced NSC proliferation, self-renewal, and neural differentiation in the SVZ, without affecting DG-derived NSCs. More importantly, expression levels of mitochondrial biogenesis-related proteins and mitochondrial antioxidant responses were significantly increased by TUDCA in SVZ-derived NSCs. Finally, intracerebroventricular administration of TUDCA in adult rats markedly enhanced both NSC proliferation and early differentiation in SVZ regions, corroborating in vitro data. Collectively, our results highlight a potential novel role for TUDCA in neurologic disorders associated with SVZ niche deterioration and impaired neurogenesis.     

Neural stem cells: involvement in adult neurogenesis and CNS repair

Recent advances in stem cell research, including the selective expansion of neural stem cells (NSCs) in vitro, the induction of particular neural cells from embryonic stem cells in vitro, the identification of NSCs or NSC-like cells in the adult brain and the detection of neurogenesis in the adult brain (adult neurogenesis), have laid the groundwork for the development of novel therapies aimed at inducing regeneration in the damaged central nervous system (CNS). There are two major strategies for inducing regeneration in the damaged CNS: (i) activation of the endogenous regenerative capacity and (ii) cell transplantation therapy. In this review, we summarize the recent findings from our group and others on NSCs, with respect to their role in insult-induced neurogenesis (activation of adult NSCs, proliferation of transit-amplifying cells, migration of neuroblasts and survival and maturation of the newborn neurons), and implications for therapeutic interventions, together with tactics for using cell transplantation therapy to treat the damaged CNS.     

Effects of hypoxia on the proliferation and differentiation of NSCs

Oxygen is vital to nearly all forms of life on Earth via its role in energy homeostasis and other cell functions. Until recently, the effects of oxygen on the proliferation and differentiation of neural stem cells (NSCs) have been largely ignored. Some studies have been carried out on the basis of the fact that NSCs exists within a “physiological hypoxic” environment at 1 to 5% O₂ in both embryonic and adult brains. The results showed that hypoxia could promote the growth of NSCs and maintain its survival in vitro. In vivo studies also showed that ischemia/hypoxia increased the number of endogenous NSCs in the subventricular zone and dentate gyrus. In addition, hypoxia could influence the differentiation of NSCs. More neurons, especially more doparminergic neurons, were produced under hypoxic condition. The effects of hypoxia on the other kind of stem cell were briefly introduced as additional evidence. The mechanism of these responses might be primarily involved in the hypoxic inducible factor-1 (HIF-1) signal pathway. The present review summarizes recent works on the role of hypoxia in the proliferation and differentiation of NSCs both in vitro and in vivo, and the mechanism involved in HIF-1 signaling pathway behind this response was also discussed.     

In vivo fate analysis reveals the multipotent and self-renewal capacities of Sox2+ neural stem cells in the adult hippocampus

To characterize the properties of adult neural stem cells (NSCs), we generated and analyzed Sox2-GFP transgenic mice. Sox2-GFP cells in the subgranular zone (SGZ) express markers specific for progenitors, but they represent two morphologically distinct populations that differ in proliferation levels. Lentivirus- and retrovirus-mediated fate-tracing studies showed that Sox2+ cells in the SGZ have potential to give rise to neurons and astrocytes, revealing their multipotency at the population as well as at a single-cell level. A subpopulation of Sox2+ cells gives rise to cells that retain Sox2, highlighting Sox2+ cells as a primary source for adult NSCs. In response to mitotic signals, increased proliferation of Sox2+ cells is coupled with the generation of Sox2+ NSCs as well as neuronal precursors. An asymmetric contribution of Sox2+ NSCs may play an important role in maintaining the constant size of the NSC pool and producing newly born neurons during adult neurogenesis.     

Oct4-induced reprogramming is required for adult brain neural stem cell differentiation into midbrain dopaminergic neurons

Neural stem cells (NSCs) lose their competency to generate region-specific neuronal populations at an early stage during embryonic brain development. Here we investigated whether epigenetic modifications can reverse the regional restriction of mouse adult brain subventricular zone (SVZ) NSCs. Using a variety of chemicals that interfere with DNA methylation and histone acetylation, we showed that such epigenetic modifications increased neuronal differentiation but did not enable specific regional patterning, such as midbrain dopaminergic (DA) neuron generation. Only after Oct-4 overexpression did adult NSCs acquire a pluripotent state that allowed differentiation into midbrain DA neurons. DA neurons derived from Oct4-reprogrammed NSCs improved behavioural motor deficits in a rat model of Parkinson's disease (PD) upon intrastriatal transplantation. Here we report for the first time the successful differentiation of SVZ adult NSCs into functional region-specific midbrain DA neurons, by means of Oct-4 induced pluripotency.     

Neuronal-glial interactions in central nervous system neurogenesis: the neural stem cell perspective

Essentially, three neuroectodermal-derived cell types make up the complex architecture of the adult CNS: neurons, astrocytes and oligodendrocytes. These elements are endowed with remarkable morphological, molecular and functional heterogeneity that reaches its maximal expression during development when stem/progenitor cells undergo progressive changes that drive them to a fully differentiated state. During this period the transient expression of molecular markers hampers precise identification of cell categories, even in neuronal and glial domains. These issues of developmental biology are recapitulated partially during the neurogenic processes that persist in discrete regions of the adult brain. The recent hypothesis that adult neural stem cells (NSCs) show a glial identity and derive directly from radial glia raises questions concerning the neuronal-glial relationships during pre- and post-natal brain development. The fact that NSCs isolated in vitro differentiate mainly into astrocytes, whereas in vivo they produce mainly neurons highlights the importance of epigenetic signals in the neurogenic niches, where glial cells and neurons exert mutual influences. Unravelling the mechanisms that underlie NSC plasticity in vivo and in vitro is crucial to understanding adult neurogenesis and exploiting this physiological process for brain repair. In this review we address the issues of neuronal/glial cell identity and neuronal-glial interactions in the context of NSC biology and NSC-driven neurogenesis during development and adulthood in vivo, focusing mainly on the CNS. We also discuss the peculiarities of neuronal-glial relationships for NSCs and their progeny in the context of in vitro systems.     

Neural stem cell transplantation therapy for brain ischemic stroke: Review and perspectives

Brain ischemic stroke is one of the most common causes of death and disability, currently has no efficient therapeutic strategy in clinic. Due to irreversible functional neurons loss and neural tissue injury, stem cell transplantation may be the most promising treatment approach. Neural stem cells (NSCs) as the special type of stem cells only exist in the nervous system, can differentiate into neurons, astrocytes, and oligodendrocytes, and have the abilities to compensate insufficient endogenous nerve cells and improve the inflammatory microenvironment of cell survival. In this review, we focused on the important role of NSCs therapy for brain ischemic stroke, mainly introduced the methods of optimizing the therapeutic efficacy of NSC transplantation, such as transfection and overexpression of specific genes, pretreatment of NSCs with inflammatory factors, and co-transplantation with cytokines. Next, we discussed the potential problems of NSC transplantation which seriously limited their rapid clinical transformation and application. Finally, we expected a new research topic in the field of stem cell research. Based on the bystander effect, exosomes derived from NSCs can overcome many of the risks and difficulties associated with cell therapy. Thus, as natural seed resource of nervous system, NSCs-based cell-free treatment is a newly therapy strategy, will play more important role in treating ischemic stroke in the future.     

Melatonin Regulates the Viability and Differentiation of Rat Midbrain Neural Stem Cells

(1) Neurogenesis driven by neural stem cells (NSCs) is regulated by physiological and pathological factors. Melatonin (MT) has profound neurotrophic and neuroprotective effects. Hence, we studied the role of MT in regulating the viability and differentiation of NSCs derived from rat ventral midbrain. (2) NSCs were isolated from the rat ventral midbrain. The viability of NSCs was determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-ulfophenyl)-2H-tetrazolium assay. The differentiation of NSCs was examined by analyzing the expression of the neural markers, MT receptors, brain derived neurotropic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) with semi-quantitative RT-PCR, immunofluorescence cytochemistry, and Western blot. (3) Our results showed that MT could promote the viability of NSCs. In addition, MT could significantly elevate the mRNA and protein levels of tyroxine hydroxylase (TH), a marker of dopaminergic neurons, and decrease the expression of the astrocytes maker glial fibrillary acidic protein (GFAP). MT also increased the production of BDNF and GDNF in the cultured NSCs. Meanwhile, we first found that two subtypes of MT receptors, MT1 and MT2, were expressed in the ventral midbrain NSCs. (4) These results demonstrated that MT could induce NSCs to differentiate into dopaminergic neurons and decrease astrocyte production. These findings also suggest that MT could offer a beneficial tool in guiding directional differentiation of NSCs.