Behavior Of Neural Stem Cells Research Articles

Epigenetic Regulation of Neural Stem Cells in Developmental and Adult Stages.

The development of the nervous system is regulated by numerous intracellular molecules and cellular signals that interact temporally and spatially with the extracellular microenvironment. The three major cell types in the brain, i.e., neurons and two types of glial cells (astrocytes and oligodendrocytes), are generated from common multipotent neural stem cells (NSCs) throughout life. However, NSCs do not have this multipotentiality from the beginning. During cortical development, NSCs sequentially obtain abilities to differentiate into neurons and glial cells in response to combinations of spatiotemporally modulated cell-intrinsic epigenetic alterations and extrinsic factors. After the completion of brain development, a limited population of NSCs remains in the adult brain and continues to produce neurons (adult neurogenesis), thus contributing to learning and memory. Many biological aspects of brain development and adult neurogenesis are regulated by epigenetic changes via behavioral control of NSCs. Epigenetic dysregulation has also been implicated in the pathogenesis of various brain diseases. Here, we present recent advances in the epigenetic regulation of NSC behavior and its dysregulation in brain disorders.

The interplay between glucose and ketone bodies in neural stem cell metabolism.

Glucose is the primary energy source for neural stem cells (NSCs), supporting their proliferation, differentiation, and quiescence. However, the high demand for glucose during brain development often exceeds its supply, leading to the utilization of alternative energy sources including ketone bodies. Ketone bodies, including β-hydroxybutyrate, are short-chain fatty acids produced through hepatic ketogenesis and play a crucial role in providing energy and the biosynthetic components for NSCs when required. The interplay between glucose and ketone metabolism influences NSC behavior and fate decisions, and disruptions in these metabolic pathways have been linked to neurodevelopmental, neuropsychiatric, and neurodegenerative disorders. Additionally, ketone bodies exert neuroprotective effects on NSCs and modulate cellular responses to oxidative stress, energy maintenance, deacetylation, and inflammation. As such, understanding the interdependence of glucose and ketone metabolism in NSCs is crucial to understanding their roles in NSC function and their implications for neurological conditions. This article reviews the mechanisms of glucose and ketone utilization in NSCs, their impact on NSC function, and the therapeutic potential of targeting these metabolic pathways in neurological disorders.

Biomimetic Dual-Network Collagen Fibers with Porous and Mechanical Cues Reconstruct Neural Stem Cell Niche via AKT/YAP Mechanotransduction after Spinal Cord Injury.

Tissue engineering scaffolds can mediate the maneuverability of neural stem cell (NSC) niche to influence NSC behavior, such as cell self-renewal, proliferation, and differentiation direction, showing the promising application in spinal cord injury (SCI) repair. Here, dual-network porous collagen fibers (PCFS) are developed as neurogenesis scaffolds by employing biomimetic plasma ammonia oxidase catalysis and conventional amidation cross-linking. Following optimizing the mechanical parameters of PCFS, the well-matched Young's modulus and physiological dynamic adaptability of PCFS (4.0wt%) have been identified as a neurogenetic exciter after SCI. Remarkably, porous topographies and curving wall-like protrusions are generated on the surface of PCFS by simple and non-toxic CO2 bubble-water replacement. As expected, PCFS with porous and matched mechanical properties can considerably activate the cadherin receptor of NSCs and induce a series of serine-threonine kinase/yes-associated protein mechanotransduction signal pathways, encouraging cellular orientation, neuron differentiation, and adhesion. In SCI rats, implanted PCFS with matched mechanical properties further integrated into the injured spinal cords, inhibited the inflammatory progression and decreased glial and fibrous scar formation. Wall-like protrusions of PCFS drive multiple neuron subtypes formation and even functional neural circuits, suggesting a viable therapeutic strategy for nerve regeneration and functional recovery after SCI.

The m6A methylation and expression profiles of mouse neural stem cells after hypoxia/reoxygenation

BackgroundIschemia–reperfusion injury to the central nervous system often causes severe complications. The activation of endogenous neural stem cells (NSCs) is considered a promising therapeutic strategy for nerve repair. However, the specific biological processes and molecular mechanisms of NSC activation remain unclear, and the role of N6-methyladenosine (m6A) methylation modification in this process has not been explored.MethodsNSCs were subjected to hypoxia/reoxygenation (H/R) to simulate ischemia–reperfusion in vivo. m6A RNA methylation quantitative kit was used to measure the total RNA m6A methylation level. Quantitative real-time PCR was used to detect methyltransferase and demethylase mRNA expression levels. Methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA sequencing (RNA-seq) were conducted for NSCs in control and H/R groups, and the sequencing results were analyzed using bioinformatics. Finally, the migration ability of NSCs was identified by wound healing assays, and the proliferative capacity of NSCs was assessed using the cell counting kit-8, EdU assays and cell spheroidization assays.ResultsOverall of m6A modification level and Mettl14 mRNA expression increased in NSCs after H/R treatment. The m6A methylation and expression profiles of mRNAs in NSCs after H/R are described for the first time. Through the joint analysis of MeRIP-seq and RNA-seq results, we verified the proliferation of NSCs after H/R, which was regulated by m6A methylation modification. Seven hub genes were identified to play key roles in the regulatory process. Knockdown of Mettl14 significantly inhibited the proliferation of NSCs. In addition, separate analysis of the MeRIP-seq results suggested that m6A methylation regulates cell migration and differentiation in ways other than affecting mRNA expression. Subsequent experiments confirmed the migration ability of NSCs was suppressed by knockdown of Mettl14.ConclusionThe biological behaviors of NSCs after H/R are closely related to m6A methylation of mRNAs, and Mettl14 was confirmed to be involved in cell proliferation and migration.

Comparative analysis of aligned and random amniotic membrane-derived cryogels for neural tissue repair.

The ordered arrangement of cells and extracellular matrix facilitates the seamless transmission of electrical signals along axons in the spinal cord and peripheral nerves. Therefore, restoring tissue geometry is crucial for neural regeneration. This study presents a novel method using proteins derived from the human amniotic membrane, which is modified with photoresponsive groups, to produce cryogels with aligned porosity. Freeze-casting was used to produce cryogels with longitudinally aligned pores, while cryogels with randomly distributed porosity were used as the control. The cryogels exhibited remarkable injectability and shape-recovery properties, essential for minimally invasive applications. Different tendencies in proliferation and differentiation were evident between aligned and random cryogels, underscoring the significance of the scaffold's microstructure in directing the behaviour of neural stem cells (NSC). Remarkably, aligned cryogels facilitated extensive cellular infiltration and migration, contrasting with NSC cultured on isotropic cryogels, which predominantly remained on the scaffold's surface throughout the proliferation experiment. Significantly, the proliferation assay demonstrated that on day 7, the aligned cryogels contained eight times more cells compared to the random cryogels. Consistent with the proliferation experiments, NSC exhibited the ability to differentiate into neurons within the aligned scaffolds and extend neurites longitudinally. In addition, differentiation assays showed a four-fold increase in the expression of neural markers in the cross-sections of the aligned cryogels. Conversely, the random cryogels exhibited minimal presence of cell bodies and extensions. The presence of synaptic vesicles on the anisotropic cryogels indicates the formation of functional synaptic connections, emphasizing the importance of the scaffold's microstructure in guiding neuronal reconnection.

Differential contribution of TrkB and p75NTR to BDNF-dependent self-renewal, proliferation, and differentiation of adult neural stem cells.

Alterations in adult neurogenesis are a common hallmark of neurodegenerative diseases. Therefore, understanding the molecular mechanisms that control this process is an indispensable requirement for designing therapeutic interventions addressing neurodegeneration. Neurotrophins have been implicated in multiple functions including proliferation, survival, and differentiation of the neural stem cells (NSCs), thereby being good candidates for therapeutic intervention. Brain-derived neurotrophic factor (BDNF) belongs to the neurotrophin family and has been proven to promote neurogenesis in the subgranular zone. However, the effects of BDNF in the adult subventricular zone (SVZ) still remain unclear due to contradictory results. Using in vitro cultures of adult NSCs isolated from the mouse SVZ, we show that low concentrations of BDNF are able to promote self-renewal and proliferation in these cells by activating the tropomyosin-related kinase B (TrkB) receptor. However, higher concentrations of BDNF that can bind the p75 neurotrophin receptor (p75NTR) potentiate TrkB-dependent self-renewal and proliferation and promote differentiation of the adult NSCs, suggesting different molecular mechanisms in BDNF-promoting proliferation and differentiation. The use of an antagonist for p75NTR reduces the increment in NSC proliferation and commitment to the oligodendrocyte lineage. Our data support a fundamental role for both receptors, TrkB and p75NTR, in the regulation of NSC behavior.

BCAT1 controls embryonic neural stem cells proliferation and differentiation in the upper layer neurons

The regulation of neural stem cell (NSC) proliferation and differentiation during brain development is a precisely controlled process, with the production of different neuronal subtypes governed by strict timelines. Glutamate is predominantly used as a neurotransmitter by the subtypes of neurons in the various layers of the cerebral cortex. The expression pattern of BCAT1, a gene involved in glutamate metabolism, in the different layers of neurons has yet to be fully understood. Using single-cell data, we have identified seven different states of NSCs and found that state 4 is closely associated with the development of projection neurons. By inferring the developmental trajectory of different neuronal subtypes from NSC subsets of this state, we discovered that BCAT1 is involved in the regulation of NSC proliferation and differentiation and is specifically highly expressed in layer II/III and IV neurons. Suppression of BCAT1 through shRNA resulted in a reduction in NSC proliferation and an abnormal development of layer II/III and IV neurons. These findings provide new insights into the role of BCAT1 in the regulation of NSC behavior and neuronal development.

Design of IKVAV peptide/gold nanoparticle decorated, micro/nano-channeled PCL/PLGA film scaffolds for neuronal differentiation and neurite outgrowth

In the field of neural tissue engineering, intensive efforts are being made to develop tissue scaffolds that can support an effective functional recovery and neural development by guiding damaged axons and neurites. Micro/nano-channeled conductive biomaterials are considered a promising approach for repairing the injured neural tissues. Many studies have demonstrated that the micro/nano-channels and aligned nanofibers could guide the neurites to extend along the direction of alignment. However, an ideal biocompatible scaffold containing conductive arrays that could promote effective neural stem cell differentiation and development, and also stimulate high neurite guidance has not been fully developed. In the current study, we aimed to fabricate micro/nano-channeled polycaprolactone (PCL)/Poly-d,l-lactic-co-glycolic acid (PLGA) hybrid film scaffolds, decorate their surfaces with IKVAV pentapeptide/gold nanoparticles (AuNPs), and investigate the behavior of PC12 cells and neural stem cells (NSCs) on the developed biomaterial under static/bioreactor conditions. Here we show that channeled groups decorated with AuNPs highly promote neurite outgrowth and neuronal differentiation along linear lines in the presence of electrical stimulation, compared with the polypyrrole (PPy) coating, which has been used traditionally for many years. Hopefully, this newly developed channeled scaffold structure (PCL/PLGA-AuNPs-IKVAV) could help to support long-distance axonal regeneration and neuronal development after different neural damages.

Crocetin Regulates Functions of Neural Stem Cells to Generate New Neurons for Cerebral Ischemia Recovery.

Many neurons undergo apoptosis after ischemic stroke. In the brain, neurogenesis has the potential for neuronal replacement and can be activated by external conditions to repair the injury. Crocetin (CRO), naturally extracted from the plant saffron, acts as a neuroprotective agent for ischemic stroke. However, the underlying mechanism remains unknown. In this work, the effect of CRO on neural stem cell (NSC) behaviors and subventricular zone neurogenesis is investigated. Initially, NSCs are incubated with different concentrations of CRO to detect the cell proliferation and differentiation in vitro. Second, ischemic stroke induced rats are treated with CRO using nimodipine (NMDP) as a comparison. The behavioral functions, infarcted volume, and apoptotic Nissl bodies of rats are noticeably improved after CRO-treatment, comparable to those of NMDP. In addition, the increased regional cerebral blood flow and promoted neuronal differentiation are achieved by CRO-treatment. Brain tissue examination shows significantly increased neuronal regeneration in the focal ischemic injury area. Meanwhile, the length of neurites is prolonged, indicating that CRO could potentially promote neurite extension to enhance cell-cell communication. These findings demonstrate that CRO facilitated the neuronal differentiation of NSCs by activating subventricular zone neurogenesis in damaged cortex and striatum sites to repair ischemic stroke.

The vasculature of neurogenic niches: Properties and function

In the adult rodent brain, neural stem cells (NSCs) reside in the subventricular zone (SVZ) of the lateral ventricles and the subgranular zone (SGZ) of the hippocampus. In these areas, NSCs and their progeny integrate intrinsic signals and extrinsic cues provided by their microenvironment that control their behavior. The vasculature in the SVZ and SGZ, and the choroid plexus (ChP) in the SVZ, have emerged as critical compartments of the neurogenic niches as they provide a rich repertoire of cues to regulate NSC quiescence, proliferation, self-renewal and differentiation. Physical contact between NSCs and blood vessels is also a feature within the niches and supports different processes such as quiescence, migration and vesicle transport. In this review, we provide a description of the brain and choroid plexus vasculature in both stem cell niches, highlighting the main properties and role of the vasculature in each niche. We also summarize the current understanding of how blood vessel- and ChP-derived signals influence the behavior of NSCs in physiological adulthood, as well as upon aging.

Connexin 43-mediated neurovascular interactions regulate neurogenesis in the adult brain subventricular zone

The subventricular zone (SVZ) is the largest neural stem cell (NSC) niche in the adult brain; herein, the blood-brain barrier is leaky, allowing direct interactions between NSCs and endothelial cells (ECs). Mechanisms by which direct NSC-EC interactions in the adult SVZ control NSC behavior are unclear. We found that Cx43 is highly expressed by SVZ NSCs and ECs, and its deletion in either leads to increased NSC proliferation and neuroblast generation, suggesting that Cx43-mediated NSC-EC interactions maintain NSC quiescence. This is further supported by single-cell RNA sequencing and invitro studies showing that ECs control NSC proliferation by regulating expression of genes associated with NSC quiescence and/or activation in a Cx43-dependent manner. Cx43 mediates these effects in a channel-independent manner involving its cytoplasmic tail and ERK activation. Such insights inform adult NSC regulation and maintenance aimed at stem cell therapies for neurodegenerative disorders.

The Biological Behaviors of Neural Stem Cell Affected by Microenvironment from Host Organotypic Brain Slices under Different Conditions

Therapeutic strategies based on neural stem cells (NSCs) transplantation bring new hope for neural degenerative disorders, while the biological behaviors of NSCs after being grafted that were affected by the host tissue are still largely unknown. In this study, we engrafted NSCs that were isolated from a rat embryonic cerebral cortex onto organotypic brain slices to examine the interaction between grafts and the host tissue both in normal and pathological conditions, including oxygen-glucose deprivation (OGD) and traumatic injury. Our data showed that the survival and differentiation of NSCs were strongly influenced by the microenvironment of the host tissue. Enhanced neuronal differentiation was observed in normal conditions, while significantly more glial differentiation was observed in injured brain slices. The process growth of grafted NSCs was guided by the cytoarchitecture of host brain slices and showed the distinct difference between the cerebral cortex, corpus callosum and striatum. These findings provided a powerful resource for unraveling how the host environment determines the fate of grafted NSCs, and raise the prospect of NSCs transplantation therapy for neurological diseases.

L-arginine homeostasis governs adult neural stem cell activation by modulating energy metabolism invivo.

Neurogenesis in the developing and adult brain is intimately linked to remodeling of cellular metabolism. However, it is still unclear how distinct metabolic programs and energy sources govern neural stem cell (NSC) behavior and subsequent neuronal differentiation. Here, we found that adult mice lacking the mitochondrial urea metabolism enzyme, Arginase-II (Arg-II), exhibited NSC overactivation, thereby leading to accelerated NSC pool depletion and decreased hippocampal neurogenesis over time. Mechanistically, Arg-II deficiency resulted in elevated L-arginine levels and induction of a metabolic shift from glycolysis to oxidative phosphorylation (OXPHOS) caused by impaired attachment of hexokinase-I to mitochondria. Notably, selective inhibition of OXPHOS ameliorated NSC overactivation and restored abnormal neurogenesis in Arg-II deficient mice. Therefore, Arg-II-mediated intracellular L-arginine homeostasis directly influences the metabolic fitness of neural stem cells that is essential to maintain neurogenesis with age.

Redox-dependent Igfbp2 signaling controls Brca1 DNA damage response to govern neural stem cell fate

Neural stem cell (NSC) maintenance and functions are regulated by reactive oxygen species (ROS). However, the mechanisms by which ROS control NSC behavior remain unclear. Here we report that ROS-dependent Igfbp2 signaling controls DNA repair pathways which balance NSC self-renewal and lineage commitment. Ncf1 or Igfbp2 deficiency constrains NSCs to a self-renewing state and prevents neurosphere formation. Ncf1-dependent oxidation of Igfbp2 promotes neurogenesis by NSCs in vitro and in vivo while repressing Brca1 DNA damage response genes and inducing DNA double-strand breaks (DDSBs). By contrast, Ncf1–/– and Igfbp2–/– NSCs favor the formation of oligodendrocytes in vitro and in vivo. Notably, transient repression of Brca1 DNA repair pathway genes induces DDSBs and is sufficient to rescue the ability of Ncf1–/– and Igfbp2–/– NSCs to lineage-commit to form neurospheres and neurons. NSC lineage commitment is dependent on the oxidizable cysteine-43 residue of Igfbp2. Our study highlights the role of DNA damage/repair in orchestrating NSC fate decisions downstream of redox-regulated Igfbp2.

Enhancement of Cell Behavior by the Polysaccharide Extract of Arthrospira and Potential Biomedical Applications.

Arthrospira is one of the most studied cyanobacteria and has been reported with practical applications. Among the substances derived from Arthrospira, polysaccharides have received relatively less attention than phycocyanins, though they have more abundant structural variations and specific properties. Herein, a new Arthrospira-derived sulfated polysaccharide was explored for its potential bioactive functions. The ability of this sulfated polysaccharide to promote the behavior of neural stem cells (NSCs) in three-dimensional hydrogel was examined for the first time. NSCs encapsulated in the sulfated polysaccharide-containing hydrogel showed better proliferation than the control hydrogel as well as a unique cell clustering behavior, i.e., formation of multicellular spherical clusters (40-60 μm). The sulfated polysaccharide, in an appropriate range of concentration (5 mg/mL), also maintained the stemness of NSCs in hydrogel and facilitated their differentiation. In addition, the potentials of the new sulfated polysaccharide as a coating material and as a component for drug carrier were verified. The sulfated polysaccharide-modified substrate exhibited superhydrophilicity (contact angle ~9°) and promoted cell adhesion to the substrate. Composite nanoparticles composed of the sulfated polysaccharide and other differently charged polysaccharides were produced with an average diameter of ~240 nm and estimated drug loading of ~18%. The new Arthrospira-derived sulfated polysaccharide is a promising candidate for cell culture, surface-modification, and drug-delivery applications in the biomedical field.

Developmental exposure to thyroid disruptors: misprogramming of the brain's stem cells in later life?

Developmental exposure to thyroid disruptors: misprogramming of the brain's stem cells in later life?

MiR-17∼92 exerts stage-specific effects in adult V-SVZ neural stem cell lineages.

Neural stem cells (NSCs) in the adult ventricular-subventricular zone (V-SVZ) generate neurons and glia throughout life. MicroRNAs are important post-transcriptional regulators frequently acting in a context-dependent manner. Here, microRNA profiling defines cohorts of miRNAs in quiescent and activated NSCs, with miR-17∼92 highly upregulated in activated NSCs and transit amplifying cells (TACs) versus quiescent NSCs. Conditional miR-17∼92 deletion in the adult V-SVZ results in stage-specific effects. In NSCs, it reduces proliferation invitro and invivo, whereas in TACs, it selectively shifts neurogenic OLIG2- DLX2+ toward oligodendrogenic OLIG2+ DLX2- TACs, due to de-repression of an oligodendrogenic program, leading to increased oligodendrogenesis invivo. This differential regulation of TAC subpopulations highlights the importance of TAC heterogeneity. Finally, in the NSC lineage for intraventricular oligodendrocyte progenitors, miR-17∼92 deletion decreases proliferation and maturation. Together, these findings reveal multiple stage-specific functions of the miR-17∼92 cluster within different adult V-SVZ lineages.

Electrical stimulation enhances the neuronal differentiation of neural stem cells in three-dimensional conductive scaffolds through the voltage-gated calcium ion channel

Electrical stimulation (ES) or electroconductive scaffold has been proved to have the positive effects on the behavior of neural stem cells (NSCs). We previously developed a novel three-dimensional conductive composite scaffold of poly (3, 4-ethylenedioxythiophen)/chitosan/gelatin (PEDOT/Cs/Gel) for neural tissue engineering. In the present study, we further studied the effect of three-dimensional conductive scaffolds combined with ES on the neuronal differentiation of NSCs. The sandwiched ES device was designed to apply single-phase pulse voltage on NSCs cultured in conductive scaffold for 7 days (4 h/day). Proliferation and differentiation related proteins and genes were analyzed by immunofluorescence staining and RT-qPCR. The role of voltage-gated ion channels (VGICs) in regulating NSCs’ neuronal differentiation by ES was investigated in presence of ion channels blockers. The results of protein and gene expression indicated that ES not only promoted the proliferation of NSCs cultured in the conductive scaffold, but also enhanced the differentiation of NSCs into neurons. Especially, the voltage-gated calcium channel (Cav2+) played an important role in the neuronal differentiation of NSCs under ES. Our findings demonstrated that ES combined with three-dimensional conductive scaffolds would be a promising strategy to regulate the neuronal differentiation of NSCs for neural regeneration.

Tissue-wide genetic and cellular landscape shapes the execution of sequential PRC2 functions in neural stem cell lineage progression.

The generation of a correctly sized cerebral cortex with all-embracing neuronal and glial cell-type diversity critically depends on faithful radial glial progenitor (RGP) cell proliferation/differentiation programs. Temporal RGP lineage progression is regulated by Polycomb repressive complex 2 (PRC2), and loss of PRC2 activity results in severe neurogenesis defects and microcephaly. How PRC2-dependent gene expression instructs RGP lineage progression is unknown. Here, we use mosaic analysis with double markers (MADM)-based single-cell technology and demonstrate that PRC2 is not cell-autonomously required in neurogenic RGPs but rather acts at the global tissue-wide level. Conversely, cortical astrocyte production and maturation is cell-autonomously controlled by PRC2-dependent transcriptional regulation. We thus reveal highly distinct and sequential PRC2 functions in RGP lineage progression that are dependent on complex interplays between intrinsic and tissue-wide properties. In a broader context, our results imply a critical role for the genetic and cellular niche environment in neural stem cell behavior.

Myostatin is a negative regulator of adult neurogenesis after spinal cord injury in zebrafish.

Intrinsic and extrinsic inhibition of neuronal regeneration obstruct spinal cord (SC) repair in mammals. In contrast, adult zebrafish achieve functional recovery after complete SC transection. While studies of innate SC regeneration have focused on axon regrowth as a primary repair mechanism, how local adult neurogenesis affects functional recovery is unknown. Here, we uncover dynamic expression of zebrafish myostatin b (mstnb) in a niche of dorsal SC progenitors after injury. mstnb mutants show impaired functional recovery, normal glial and axonal bridging across the lesion, and an increase in the profiles of newborn neurons. Molecularly, neuron differentiation genes are upregulated, while the neural stem cell maintenance gene fgf1b is downregulated in mstnb mutants. Finally, we show that human fibroblast growth factor 1 (FGF1) treatment rescues the molecular and cellular phenotypes of mstnb mutants. These studies uncover unanticipated neurogenic functions for mstnb and establish the importance of local adult neurogenesis for innate SC repair.