Insights into the Biology and Therapeutic Applications of Neural Stem Cells

Adult Neurogenesis of Teleost Fish Determines High Neuronal Plasticity and Regeneration

Studying the properties of neural stem progenitor cells (NSPCs) in a fish model will provide new information about the organization of neurogenic niches containing embryonic and adult neural stem cells, reflecting their development, origin cell lines and proliferative dynamics. Currently, the molecular signatures of these populations in homeostasis and repair in the vertebrate forebrain are being intensively studied. Outside the telencephalon, the regenerative plasticity of NSPCs and their biological significance have not yet been practically studied. The impressive capacity of juvenile salmon to regenerate brain suggests that most NSPCs are likely multipotent, as they are capable of replacing virtually all cell lineages lost during injury, including neuroepithelial cells, radial glia, oligodendrocytes, and neurons. However, the unique regenerative profile of individual cell phenotypes in the diverse niches of brain stem cells remains unclear. Various types of neuronal precursors, as previously shown, are contained in sufficient numbers in different parts of the brain in juvenile Pacific salmon. This review article aims to provide an update on NSPCs in the brain of common models of zebrafish and other fish species, including Pacific salmon, and the involvement of these cells in homeostatic brain growth as well as reparative processes during the postraumatic period. Additionally, new data are presented on the participation of astrocytic glia in the functioning of neural circuits and animal behavior. Thus, from a molecular aspect, zebrafish radial glia cells are seen to be similar to mammalian astrocytes, and can therefore also be referred to as astroglia. However, a question exists as to if zebrafish astroglia cells interact functionally with neurons, in a similar way to their mammalian counterparts. Future studies of this fish will complement those on rodents and provide important information about the cellular and physiological processes underlying astroglial function that modulate neural activity and behavior in animals.

Regenerative Stem Cell Therapy for Neurodegenerative Diseases: An Overview

Neurodegenerative diseases resulting from the progressive loss of structure and/or function of neurons contribute to different paralysis degrees and loss of cognition and sensation. The lack of successful curative therapies for neurodegenerative disorders leads to a considerable burden on society and a high economic impact. Over the past 20 years, regenerative cell therapy, also known as stem cell therapy, has provided an excellent opportunity to investigate potentially powerful innovative strategies for treating neurodegenerative diseases. This is due to stem cells' capability to repair injured neuronal tissue by replacing the damaged or lost cells with differentiated cells, providing a conducive environment that is in favor of regeneration, or protecting the existing healthy neurons and glial cells from further damage. Thus, in this review, the various types of stem cells, the current knowledge of stem-cell-based therapies in neurodegenerative diseases, and the recent advances in this field are summarized. Indeed, a better understanding and further studies of stem cell technologies cause progress into realistic and efficacious treatments of neurodegenerative disorders.

Common Regulatory Targets of NFIA, NFIX and NFIB during Postnatal Cerebellar Development

Transcriptional regulation plays a central role in controlling neural stem and progenitor cell proliferation and differentiation during neurogenesis. For instance, transcription factors from the nuclear factor I (NFI) family have been shown to co-ordinate neural stem and progenitor cell differentiation within multiple regions of the embryonic nervous system, including the neocortex, hippocampus, spinal cord and cerebellum. Knockout of individual Nfi genes culminates in similar phenotypes, suggestive of common target genes for these transcription factors. However, whether or not the NFI family regulates common suites of genes remains poorly defined. Here, we use granule neuron precursors (GNPs) of the postnatal murine cerebellum as a model system to analyse regulatory targets of three members of the NFI family: NFIA, NFIB and NFIX. By integrating transcriptomic profiling (RNA-seq) of Nfia- and Nfix-deficient GNPs with epigenomic profiling (ChIP-seq against NFIA, NFIB and NFIX, and DNase I hypersensitivity assays), we reveal that these transcription factors share a large set of potential transcriptional targets, suggestive of complementary roles for these NFI family members in promoting neural development.

Effects of Ginsenoside Rg1 Regulating Wnt/β-Catenin Signaling on Neural Stem Cells to Delay Brain Senescence

This is a study on the relationship between the protective effect of ginsenoside Rg1 on senescent neural stem cells and Wnt-β/catenin signaling pathway. Background. Recent studies have shown that overactivation of the Wnt/β-catenin signaling pathway is closely related to stem cell senescence. Whether Rg1 delays the senescence of NSCs is related to the regulation of this signaling pathway. Methods. The whole brain of Nestin-GFP transgenic newborn rat was extracted, and NSCs were extracted and cultured to P3 generation. The following indicators were detected: (1) NSC culture identification, (2) the effect of LiCl on the proliferation and survival rate of NSCs, (3) the effect of ginsenoside Rg1 on the proliferation and survival of NSCs, (4) the growth of NSCs in each group observed by an optical microscope, (5) the cell cycle of each group detected by flow cytometry, (6) the proliferative ability of each group detected by BrdU, (7) the fluorescence intensity of Nestin and Sox2 of NSCs in each group observed by a fluorescence microscope, (8) the positive rate of senescence staining analyzed by SA-β-Gal staining, (9) the localization of β-catenin in NSCs observed by laser confocal microscopy, and (10) the changes of the Wnt/β-catenin pathway-related proteins in each group detected by Western blotting. Results. LiCl activates the Wnt/β-catenin pathway and promotes mouse neural stem cell senescence. Ginsenoside Rg1 promotes proliferation of neural stem cells and inhibits Wnt/β-catenin pathway activation. Conclusions. LiCl can activate the Wnt/β-catenin signaling pathway of NSCs, and ginsenoside Rg1 can antagonize the senescence of NSCs caused by activation of the Wnt/β-catenin signaling pathway and delay brain aging.

The Emerging Role of lncRNAs in Spinal Cord Injury

Spinal cord injury (SCI) is a highly debilitating disease and is increasingly being recognized as an important global health priority. However, the mechanisms underlying SCI have not yet been fully elucidated, and effective therapies for SCI are lacking. Long noncoding RNAs (lncRNAs), which form a major class of noncoding RNAs, have emerged as novel targets for regulating several physiological functions and mediating numerous neurological diseases. Notably, gene expression profile analyses have demonstrated aberrant changes in lncRNA expression in rats or mice after traumatic or nontraumatic SCI. LncRNAs have been shown to be associated with multiple pathophysiological processes following SCI including inflammation, neural apoptosis, and oxidative stress. They also play a crucial role in the complications associated with SCI, such as neuropathic pain. At the same time, some lncRNAs have been found to be therapeutic targets for neural stem cell transplantation and hydrogen sulfide treatment aimed at alleviating SCI. Therefore, lncRNAs could be promising biomarkers for the diagnosis, treatment, and prognosis of SCI. However, further researches are required to clarify the therapeutic effects of lncRNAs on SCI and the mechanisms underlying these effects. In this study, we reviewed the current progress of the studies on the involvement of lncRNAs in SCI, with the aim of drawing attention towards their roles in this debilitating condition.

Local delivery of FTY720 and NSCs on electrospun PLGA scaffolds improves functional recovery after spinal cord injury

Spinal cord injury (SCI) is a common issue in the clinic that causes severe motor and sensory dysfunction below the lesion level. FTY720, also known as fingolimod, has recently been reported to exert a positive effect on the recovery from a spinal cord injury. Through local delivery to the lesion site, FTY720 effectively integrates with biomaterials, and the systemic adverse effects are alleviated. However, the effects of the proper mass ratio of FTY720 in biomaterials on neural stem cell (NSC) proliferation and differentiation, as well as functional recovery after SCI, have not been thoroughly investigated. In our study, we fabricated electrospun poly (lactide-co-glycolide) (PLGA)/FTY720 scaffolds at different mass ratios (0.1%, 1%, and 10%) and characterized these scaffolds. The effects of electrospun PLGA/FTY720 scaffolds on NSC proliferation and differentiation were measured. Then, a rat model of spinal transection was established to investigate the effects of PLGA/FTY720 scaffolds loaded with NSCs. Notably, 1% PLGA/FTY720 scaffolds exerted the best effects on the proliferation and differentiation of NSCs and 10% PLGA/FTY720 was cytotoxic to NSCs. Based on the Basso, Beattie, and Bresnahan (BBB) score, HE staining and immunofluorescence staining, the PLGA/FTY720 scaffold loaded with NSCs effectively promoted the recovery of spinal cord function. Thus, FTY720 properly integrated with electrospun PLGA scaffolds, and electrospun PLGA/FTY720 scaffolds loaded with NSCs may have potential applications for SCI as a nerve implant.

Spinal cord injury (SCI) is a common issue in the clinic that causes severe motor and sensory dysfunction below the lesion level.

NFIX-Mediated Inhibition of Neuroblast Branching Regulates Migration Within the Adult Mouse Ventricular–Subventricular Zone

Understanding the migration of newborn neurons within the brain presents a major challenge in contemporary biology. Neuronal migration is widespread within the developing brain but is also important within the adult brain. For instance, stem cells within the ventricular–subventricular zone (V-SVZ) and the subgranular zone of dentate gyrus of the adult rodent brain produce neuroblasts that migrate to the olfactory bulb and granule cell layer of the dentate gyrus, respectively, where they regulate key brain functions including innate olfactory responses, learning, and memory. Critically, our understanding of the factors mediating neuroblast migration remains limited. The transcription factor nuclear factor I X (NFIX) has previously been implicated in embryonic cortical development. Here, we employed conditional ablation of Nfix from the adult mouse brain and demonstrated that the removal of this gene from either neural stem and progenitor cells, or neuroblasts, within the V-SVZ culminated in neuroblast migration defects. Mechanistically, we identified aberrant neuroblast branching, due in part to increased expression of the guanylyl cyclase natriuretic peptide receptor 2 (Npr2), as a factor contributing to abnormal migration in Nfix-deficient adult mice. Collectively, these data provide new insights into how neuroblast migration is regulated at a transcriptional level within the adult brain.

Foxm1 controls a pro-stemness microRNA network in neural stem cells

Cerebellar neural stem cells (NSCs) require Hedgehog-Gli (Hh-Gli) signalling for their maintenance and Nanog expression for their self-renewal. To identify novel molecular features of this regulatory pathway, we used next-generation sequencing technology to profile mRNA and microRNA expression in cerebellar NSCs, before and after induced differentiation (Diff-NSCs). Genes with higher transcript levels in NSCs (vs. Diff-NSCs) included Foxm1, which proved to be directly regulated by Gli and Nanog. Foxm1 in turn regulated several microRNAs that were overexpressed in NSCs: miR-130b, miR-301a, and members of the miR-15~16 and miR-17~92 clusters and whose knockdown significantly impaired the neurosphere formation ability. Our results reveal a novel Hh-Gli-Nanog-driven Foxm1-microRNA network that controls the self-renewal capacity of NSCs.

Transcriptional regulation of ependymal cell maturation within the postnatal brain

Background

Radial glial stem cells within the developing nervous system generate a variety of post-mitotic cells, including neurons and glial cells, as well as the specialised multi-ciliated cells that line the walls of the ventricular system, the ependymal cells. Ependymal cells separate the brain parenchyma from the cerebrospinal fluid and mediate osmotic regulation, the flow of cerebrospinal fluid, and the subsequent dispersion of signalling molecules via the co-ordinated beating of their cilia. Deficits to ependymal cell development and function have been implicated in the formation of hydrocephalus, but the transcriptional mechanisms underpinning ependymal development remain poorly characterised.

Findings

Here, we demonstrate that the transcription factor nuclear factor IX (NFIX) plays a central role in the development of the ependymal cell layer of the lateral ventricles. Expression of ependymal cell-specific markers is delayed in the absence of Nfix. Moreover, Nfix-deficient mice exhibit aberrant ependymal cell morphology at postnatal day 15, culminating in abnormal thickening and intermittent loss of this cell layer. Finally, we reveal Foxj1, a key factor promoting ependymal cell maturation, as a target for NFIX-mediated transcriptional activation.

Conclusions

Collectively, our data indicate that ependymal cell development is reliant, at least in part, on NFIX expression, further implicating this transcription factor as a mediator of multiple aspects of radial glial biology during corticogenesis.

Electronic supplementary material

The online version of this article (10.1186/s13064-018-0099-4) contains supplementary material, which is available to authorized users.

Combined acupuncture and HuangDiSan treatment affects behavior and synaptophysin levels in the hippocampus of senescence-accelerated mouse prone 8 after neural stem cell transplantation

Sanjiao acupuncture and HuangDiSan can promote the proliferation, migration and differentiation of exogenous neural stem cells in senescence-accelerated mouse prone 8 (SAMP8) mice and can improve learning and memory impairment and behavioral function in dementia-model mice. Thus, we sought to determine whether Sanjiao acupuncture and HuangDiSan can elevate the effect of neural stem cell transplantation in Alzheimer’s disease model mice. Sanjiao acupuncture was used to stimulate Danzhong (CV17), Zhongwan (CV12), Qihai (CV6), bilateral Xuehai (SP10) and bilateral Zusanli (ST36) 15 days before and after implantation of neural stem cells (5 × 10⁵) into the hippocampal dentate gyrus of SAMP8 mice. Simultaneously, 0.2 mL HuangDiSan, containing Rehmannia Root and Chinese Angelica, was intragastrically administered. Our results demonstrated that compared with mice undergoing neural stem cell transplantation alone, learning ability was significantly improved and synaptophysin mRNA and protein levels were greatly increased in the hippocampus of mice undergoing both Sanjiao acupuncture and intragastric administration of HuangDiSan. We conclude that the combination of Sanjiao acupuncture and HuangDiSan can effectively improve dementia symptoms in mice, and the mechanism of this action might be related to the regulation of synaptophysin expression.

Long nonding RNA UCA1 regulates neural stem cell differentiation by controlling miR-1/Hes1 expression

Neural stem cells are able to self-renew and generate glial and neuronal lineages. Neural stem cell may serve as therapeutic method for neurological disorders including spinal cord injuries, Parkinson's disease, Huntington's disease and Alzheimer's disease. Long noncoding RNAs (lncRNAs) are longer than 200 nucleotides with limited protein-coding capacity. Recent studies have demonstreated that lncRNAs play an important role in several cellular processes including cell differentiation, cell development, proliferation, apoptosis, invasion and migration. However, the role of lncRNA human urothelial carcinoma associated 1 (UCA1) in the development of neural stem cells remains unknown. In this study, we showed that the expression of UCA1 was upregulated in the neural stem cell in a time-dependent manner. Knockdown of UCA1 suppressed the neural stem cell proliferation. Inhibition of UCA1 decreased the expression of nestin and the formation of neurosphere. Moreover, knockdown of UCA1 suppressed the neural stem cell differentiation to astrocyte and promoted the neural stem cell differentiation to neuron. Furthermore, we demonstrated that knockdown of UCA1 increased the expression of miR-1 in the neural stem cell and suppressed the expresion of Hes1, which is one target gene of miR-1. In addition, ectopic expression of Hes1 could impair siUCA1-induced neural stem cells proliferation. Overexpression of Hes1 suppressed siUCA1-induced β-tubulin expression and promoted siUCA1-inhibited GFAP expression in the neural stem cell. These results suggested that UCA1 regulated the neural stem cell proliferation and differentiation through regulating Hes1 expression.

Effects of FTY720 on brain neurogenic niches in vitro and after kainic acid-induced injury

Background

FTY720 (fingolimod, Gilenya™) is an oral, blood-brain barrier (BBB)-passing drug approved as immunomodulatory treatment for relapsing-remitting form of the multiple sclerosis (MS). In addition, FTY720 exerts several effects in the central nervous system (CNS), ranging from neuroprotection to reduction of neuroinflammation. However, the neurogenic and oligodendrogenic potential of FTY720 has been poorly investigated. In this study, we assessed the effect of FTY720 on the production of new neurons and oligodendrocytes from neural stem/precursor cells both in vitro and in vivo.

Methods

Neural stem cells (NSCs) derived from the young rat subventricular zone (SVZ) were exposed to FTY720 (10, 100 nM), and their differentiation into neurons and oligodendrocytes was measured using immunofluorescence for anti-β-III tubulin or CNPase (2′,3′-cyclic nucleotide 3′-phosphodiesterase) as markers of mature neurons or oligodendrocytes, respectively. In addition, intracerebroventricular (icv) administration of kainic acid (KA; 0.5 μg/2 μl) in Sprague-Dawley rats was used as an in vivo model of neuronal death and inflammation. FTY720 was applied icv (1 μg/2 μl), together with KA, plus intraperitoneally (ip; 1 mg/kg) 24 h before, and daily, until sacrifice 8 days after KA injection. To visualize cell proliferation in the hippocampus and in white matter regions, rats were administered 5-bromo-2-deoxyuridine (BrdU) 100 mg/kg, ip injected every 2 days. Immunohistochemical analyses were performed on rat brain slices to measure the production of new neuronal precursors (doublecortin/DCX⁺ cells) and new oligodendrocytes precursors (proteoglycan/NG2⁺ cells).

Results

In this study, we observed that FTY720 increased postnatal NSCs differentiation into both neurons and oligodendrocytes in vitro. In turn, in adult animals, FTY720 enhanced the percentage of BrdU⁺ cells coexpressing DCX marker, both in basal (FTY720 alone) and in neurodegenerative (FTY720 + KA) conditions. However, FTY720 had only a partial effect on proliferation and differentiation of oligodendrocyte progenitor cell (OPC) population in vivo.

Conclusions

FTY720 promotes neurogenesis and oligodendrogenesis in vitro under basal conditions. In addition, it increases the generation of neuroblasts and oligodendrocytes after excitotoxic brain injury. This suggests that FTY720 has the potential to activate the neurogenic niche and thus favour tissue repair after lesion.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0922-6) contains supplementary material, which is available to authorized users.

Stem cell therapies in age-related neurodegenerative diseases and stroke

Aging, a complex process associated with various structural, functional and metabolic changes in the brain, is an important risk factor for neurodegenerative diseases and stroke. These diseases share similar neuropathological changes, such as the formation of misfolded proteins, oxidative stress, loss of neurons and synapses, dysfunction of the neurovascular unit (NVU), reduction of self-repair capacity, and motor and/or cognitive deficiencies. In addition to gray matter dysfunction, the plasticity and repair capacity of white matter also decrease with aging and contribute to neurodegenerative diseases. Aging not only renders patients more susceptible to these disorders, but also attenuates their self-repair capabilities. In addition, low drug responsiveness and intolerable side effects are major challenges in the prevention and treatment of senile diseases. Thus, stem cell therapies-characterized by cellular plasticity and the ability to self-renew-may be a promising strategy for aging-related brain disorders. Here, we review the common pathophysiological changes, treatments, and the promises and limitations of stem cell therapies in age-related neurodegenerative diseases and stroke.

β-Arrestin1/miR-326 Transcription Unit Is Epigenetically Regulated in Neural Stem Cells Where It Controls Stemness and Growth Arrest

Cell development is regulated by a complex network of mRNA-encoded proteins and microRNAs, all funnelling onto the modulation of self-renewal or differentiation genes. How intragenic microRNAs and their host genes are transcriptionally coregulated and their functional relationships for the control of neural stem cells (NSCs) are poorly understood. We propose here the intragenic miR-326 and its host gene β-arrestin1 as novel players whose epigenetic silencing maintains stemness in normal cerebellar stem cells. Such a regulation is mediated by CpG islands methylation of the common promoter. Epigenetic derepression of β-arrestin1/miR-326 by differentiation signals or demethylating agents leads to suppression of stemness features and cell growth and promotes cell differentiation. β-Arrestin1 inhibits cell proliferation by enhancing the nuclear expression of the cyclin-dependent kinase inhibitor p27. Therefore, we propose a new mechanism for the control of cerebellar NSCs where a coordinated epigenetic mechanism finely regulates β-arrestin1/miR-326 expression and consequently NSCs stemness and cell growth.

Cell-type-specific expression of NFIX in the developing and adult cerebellum

Transcription factors from the nuclear factor one (NFI) family have been shown to play a central role in regulating neural progenitor cell differentiation within the embryonic and post-natal brain. NFIA and NFIB, for instance, promote the differentiation and functional maturation of granule neurons within the cerebellum. Mice lacking Nfix exhibit delays in the development of neuronal and glial lineages within the cerebellum, but the cell-type-specific expression of this transcription factor remains undefined. Here, we examined the expression of NFIX, together with various cell-type-specific markers, within the developing and adult cerebellum using both chromogenic immunohistochemistry and co-immunofluorescence labelling and confocal microscopy. In embryos, NFIX was expressed by progenitor cells within the rhombic lip and ventricular zone. After birth, progenitor cells within the external granule layer, as well as migrating and mature granule neurons, expressed NFIX. Within the adult cerebellum, NFIX displayed a broad expression profile, and was evident within granule cells, Bergmann glia, and interneurons, but not within Purkinje neurons. Furthermore, transcriptomic profiling of cerebellar granule neuron progenitor cells showed that multiple splice variants of Nfix are expressed within this germinal zone of the post-natal brain. Collectively, these data suggest that NFIX plays a role in regulating progenitor cell biology within the embryonic and post-natal cerebellum, as well as an ongoing role within multiple neuronal and glial populations within the adult cerebellum.

Effects of FTY720 (Fingolimod) on Proliferation, Differentiation, and Migration of Brain-Derived Neural Stem Cells

Insufficient proliferation, differentiation, and migration are the main pitfalls of neural stem cells (NSCs) in reparative therapeutics for the central nervous system (CNS) diseases. The potent lipid mediator sphingosine-1-phosphate (S1P) regulates cells' biological behavior broadly in the CNS. However, the effects of activating S1P on NSCs are not quite clear. In the current study, FTY720 (Fingolimod), an analog of S1P, was employed to induce the proliferation, differentiation, and migration of cultured brain-derived NSCs. The results indicated that proliferation and migration ability of NSCs were promoted by FTY720. Though we observed no obvious neuron prefers differentiation of NSCs, there were more protoplasmic astrocytes developed in the presence of certain concentration of FTY720. This work gives more comprehensive understanding of how FTY720 affects NSCs.