One mouse, two cultures: isolation and culture of adult neural stem cells from the two neurogenic zones of individual mice

Bexarotene drives the self-renewing proliferation of adult neural stem cells, promotes neuron-glial fate shift, and regulates late neuronal differentiation

Treatment with bexarotene, a selective retinoid X receptor (RXR) agonist, significantly improves behavioral dysfunctions in various neurodegenerative animal models. Additionally, it activates neurodevelopmental and plasticity pathways in the brains of adult mice. Our objective was to investigate the impact of RXR activation by bexarotene on adult neural stem cells (aNSC) and their cell lineages. To achieve this, we treated NSCs isolated from the subventricular zone (SVZ) of adult rat brains from the proliferative stage to the differentiated status. The results showed that bexarotene-treated aNSC exhibited increased BrdU incorporation, SOX2+ dividing cell pairs, and cell migration from neurospheres, revealing that the treatment promotes self-renewing proliferation and cell motility in SVZ-aNCS. Furthermore, bexarotene induced a cell fate shift characterized by a significant increase in GFAP+/S100B+ differentiated astrocytes, which uncovers the participation of activated-RXR in astrogenesis. In the neuronal lineage, the fate shift was counteracted by bexarotene-induced enhancement of NeuN+ nuclei together with neurite network outgrowth, indicating that the RXR agonist stimulates SVZ-aNCS neuronal differentiation at later stages. These findings establish new connections between RXR activation, astro- and neurogenesis in the adult brain, and contribute to the development of therapeutic strategies targeting nuclear receptors for neural repair.

Characteristics of quiescent adult neural stem cells induced by the bFGF/BMP4 combination or BMP4 alone in vitro

Bone morphogenetic protein-4 (BMP4) is involved in regulation of neural stem cells (NSCs) proliferation, differentiation, migration and survival. It was previously thought that the treatment of NSCs with BMP4 alone induces astrocytes, whereas the treatment of NSCs with the bFGF/BMP4 combination induces quiescent neural stem cells (qNSCs). In this study, we performed bulk RNA sequencing (RNA-Seq) to compare the transcriptome profiles of BMP4-treated NSCs and bFGF/BMP4-treated NSCs, and found that both NSCs treated by these two methods were Sox2 positive qNSCs which were able to generate neurospheres. However, NSCs treated by those two methods exhibited different characteristics in state and the potential for neuronal differentiation based on transcriptome analysis and experimental results. We found that BMP4-treated NSCs tended to be in a deeper quiescent state than bFGF/BMP4-treated NSCs as the percentage of ki67-positive cells were lower in BMP4-treated NSCs. And after exposure to differentiated environment, bFGF/BMP4-treated NSCs generated more DCX-positive immature neurons and MAP2-positive neurons than BMP4-treated NSCs. Our study characterized qNSCs treated with BMP4 alone and bFGF/BMP4 combination, providing a reference for the scientific use of BMP4 and bFGF/BMP4-induced qNSCs models.

Neurosphere culture derived from aged hippocampal dentate gyrus

The neurosphere assay is the gold standard for determining proliferative and differentiation potential of neural progenitor cells (NPCs) in neurogenesis studies 1-3 . While several in vitro assays have been developed to model the process of neurogenesis, they have predominantly used embryonic and early postnatal NPCs derived from the dentate gyrus (DG). A limitation of these approaches is that they do not provide insight into adult-born NPCs, which are modeled to affect hippocampal function and diseases later in life. Here, we show a novel free-floating neurosphere culture system using NPCs isolated from the DG of mature adult and aged mice. The protocol outlines detailed steps on the isolation, propagation, and maintenance of neurospheres from adult and aged (>12 months old) mouse brain and how to differentiate cultured neurospheres into neurons and astrocytes. Culturing adult and aged NPCs provides an important in vitro model to (1) investigate cellular and molecular properties of this unique cell population and (2) expand the understanding of plasticity in the adult and aging brain. This protocol requires ∼2 hours to complete dissection, dissociation and culture plating, while differentiation to neuronal and astrocytic lineages takes 9 days. By focusing on neurospheres obtained from animals at later ages this model facilitates investigation of important biological questions related to development and differentiation of hippocampal neurons generated throughout adult life.

Glucocorticoids rescue cell surface trafficking of R451C Neuroligin3 and enhance synapse formation

Neuroligins are synaptic cell adhesion proteins with a role in synaptic function, implicated in neurodevelopmental disorders. The autism spectrum disorder-associated substitution Arg451Cys (R451C) in NLGN3 promotes a partial misfolding of the extracellular domain of the protein leading to retention in the endoplasmic reticulum (ER) and the induction of the unfolded protein response (UPR). The reduced trafficking of R451C NLGN3 to the cell surface leads to altered synaptic function and social behavior. A screening in HEK-293 cells overexpressing NLGN3 of 2662 compounds (FDA-approved small molecule drug library), led to the identification of several glucocorticoids such as alclometasone dipropionate, desonide, prednisolone sodium phosphate, and dexamethasone (DEX), with the ability to favor the exit of full-length R451C NLGN3 from the ER. DEX improved the stability of R451C NLGN3 and trafficking to the cell surface, reduced the activation of the UPR, and increased the formation of artificial synapses between HEK-293 and hippocampal primary neurons. The effect of DEX was validated on a novel model system represented by neural stem progenitor cells and differentiated neurons derived from the R451C NLGN3 knock-in mouse, expressing the endogenous protein. This work shows a potential rescue strategy for an autism-linked mutation affecting cell surface trafficking of a synaptic protein.

c-Cbl Regulates Murine Subventricular Zone-Derived Neural Progenitor Cells in Dependence of the Epidermal Growth Factor Receptor

The localization, expression, and physiological role of regulatory proteins in the neurogenic niches of the brain is fundamental to our understanding of adult neurogenesis. This study explores the expression and role of the E3-ubiquitin ligase, c-Cbl, in neurogenesis within the subventricular zone (SVZ) of mice. In vitro neurosphere assays and in vivo analyses were performed in specific c-Cbl knock-out lines to unravel c-Cbl's role in receptor tyrosine kinase signaling, including the epidermal growth factor receptor (EGFR) pathway. Our findings suggest that c-Cbl is significantly expressed within EGFR-expressing cells, playing a pivotal role in neural stem cell proliferation and differentiation. However, c-Cbl's function extends beyond EGFR signaling, as its loss upon knock-out stimulated progenitor cell proliferation in neurosphere cultures. Yet, this effect was not detected in hippocampal progenitor cells, reflecting the lack of the EGFR in the hippocampus. In vivo, c-Cbl exerted only a minor proneurogenic influence with no measurable impact on the formation of adult-born neurons. In conclusion, c-Cbl regulates neural stem cells in the subventricular zone via the EGFR pathway but, likely, its loss is compensated by other signaling modules in vivo.

Single-nucleus transcriptomic mapping uncovers targets for traumatic brain injury

The subventricular zone (SVZ) is a neurogenic niche that contributes to homeostasis and repair after brain injury. However, the effects of mild traumatic brain injury (mTBI) on the divergence of the regulatory DNA landscape within the SVZ and its link to functional alterations remain unexplored. In this study, we mapped the transcriptome atlas of murine SVZ and its responses to mTBI at the single-cell level. We observed cell-specific gene expression changes following mTBI and unveiled diverse cell-to-cell interaction networks that influence a wide array of cellular processes. Moreover, we report novel neurogenesis lineage trajectories and related key transcription factors, which we validate through loss-of-function experiments. Specifically, we validate the role of Tcf7l1, a cell cycle gene regulator, in promoting neural stem cell differentiation toward the neuronal lineage after mTBI, providing a potential target for regenerative medicine. Overall, our study profiles an SVZ transcriptome reference map, which underlies the differential cellular behavior in response to mTBI. The identified key genes and pathways that may ameliorate brain damage or facilitate neural repair serve as a comprehensive resource for drug discovery in the context of mTBI.

Nerve growth factor receptor (Ngfr) induces neurogenic plasticity by suppressing reactive astroglial Lcn2/Slc22a17 signaling in Alzheimer's disease

Neurogenesis, crucial for brain resilience, is reduced in Alzheimer's disease (AD) that induces astroglial reactivity at the expense of the pro-neurogenic potential, and restoring neurogenesis could counteract neurodegenerative pathology. However, the molecular mechanisms promoting pro-neurogenic astroglial fate despite AD pathology are unknown. In this study, we used APP/PS1dE9 mouse model and induced Nerve growth factor receptor (Ngfr) expression in the hippocampus. Ngfr, which promotes neurogenic fate of astroglia during the amyloid pathology-induced neuroregeneration in zebrafish brain, stimulated proliferative and neurogenic outcomes. Histological analyses of the changes in proliferation and neurogenesis, single-cell transcriptomics, spatial proteomics, and functional knockdown studies showed that the induced expression of Ngfr reduced the reactive astrocyte marker Lipocalin-2 (Lcn2), which we found was sufficient to reduce neurogenesis in astroglia. Anti-neurogenic effects of Lcn2 was mediated by Slc22a17, blockage of which recapitulated the pro-neurogenicity by Ngfr. Long-term Ngfr expression reduced amyloid plaques and Tau phosphorylation. Postmortem human AD hippocampi and 3D human astroglial cultures showed elevated LCN2 levels correlate with reactive gliosis and reduced neurogenesis. Comparing transcriptional changes in mouse, zebrafish, and human AD brains for cell intrinsic differential gene expression and weighted gene co-expression networks revealed common altered downstream effectors of NGFR signaling, such as PFKP, which can enhance proliferation and neurogenesis in vitro when blocked. Our study suggests that the reactive non-neurogenic astroglia in AD can be coaxed to a pro-neurogenic fate and AD pathology can be alleviated with Ngfr. We suggest that enhancing pro-neurogenic astroglial fate may have therapeutic ramifications in AD.

Single-nucleus profiling of adult mice sub-ventricular zone after blast-related traumatic brain injury

Explosive blast-related traumatic brain injuries (bTBI) are common in war zones and urban terrorist attacks. These bTBIs often result in complex neuropathologic damage and neurologic complications. However, there is still a lack of specific strategies for diagnosing and/or treating bTBIs. The sub-ventricular zone (SVZ), which undergoes adult neurogenesis, is critical for the neurological maintenance and repair after brain injury. However, the cellular responses and mechanisms that trigger and modulate these activities in the pathophysiological processes following bTBI remain poorly understood. Here we employ single-nucleus RNA-sequencing (snRNA-seq) of the SVZ from mice subjected to a bTBI. This data-set, including 15272 cells (7778 bTBI and 7494 control) representing all SVZ cell types and is ideally suited for exploring the mechanisms underlying the pathogenesis of bTBIs. Additionally, it can serve as a reference for future studies regarding the diagnosis and treatment of bTBIs.

A region-dependent allele-biased expression of Dopa decarboxylase in mouse brain

Genomic imprinting is an epigenetic event in which genes are expressed only from either the paternal or maternal allele. Dopa decarboxylase (Ddc), is an imprinted gene that encodes an enzyme which catalyzes the conversion of L-dopa to dopamine. Although Ddc has been reported to be paternally expressed in embryonic and neonatal hearts, its expression pattern in the brain has been controversial. To visualize Ddc-expressing neurons, we established a knock-in mouse carrying a humanized Kusabira orange 1 (hKO1) reporter cassette at the Ddc locus (Ddc-hKO1). The expression of Ddc-hKO1 was detected in all known Ddc-positive cells in the brains of embryonic, neonatal, adult, and aged mice. We further developed an efficient purification method for Ddc-hKO1-positive neurons using a cell sorter. RNA sequencing analysis confirmed the enrichment of dopaminergic, serotonergic and cholinergic neurons in Ddc-hKO1-positive cell population recovered using this method. A detailed analysis of Ddc-hKO1 paternally and maternally derived heterozygous mice combined with immunostaining revealed that Ddc was preferentially expressed from the maternal allele in ventral tegmented area (VTA), substantia nigra pars compacta (SNc), and retrorubral field (RRF); while it was expressed from both alleles in dorsal raphe nucleus (DR). These results indicate that Ddc exhibit an allele-specific expression pattern in different brain regions, presumably reflecting the diverse regulatory mechanisms of imprinting.

A Bone Morphogenetic Protein Signaling Inhibitor, LDN193189, Converts Ischemia-Induced Multipotent Stem Cells into Neural Stem/Progenitor Cell-Like Cells

Stem cell therapy is used to restore neurological function in stroke patients. We have previously reported that ischemia-induced multipotent stem cells (iSCs), which are likely derived from brain pericytes, develop in poststroke human and mouse brains. Although we have demonstrated that iSCs can differentiate into neural lineage cells, the factors responsible for inducing this differentiation remain unclear. In this study, we found that LDN193189, a bone morphogenetic protein (BMP) inhibitor, caused irreversible changes in the shape of iSCs. In addition, compared with iSCs incubated without LDN193189, the iSCs incubated with LDN193189 (LDN-iSCs) showed upregulated expression of neural lineage-related genes and proteins, including those expressed in neural stem/progenitor cells (NSPCs), and downregulated expression of mesenchymal and pericytic-related genes and proteins. Moreover, microarray analysis revealed that LDN-iSCs and NSPCs had similar gene expression profiles. Furthermore, LDN-iSCs differentiated into electrophysiologically functional neurons. These results indicate that LDN193189 induces NSPC-like cells from iSCs, suggesting that bioactive molecules regulating BMP signaling are potential targets for promoting neurogenesis from iSCs in the pathological brain, such as during ischemic stroke. We believe that our findings will bring us one step closer to the clinical application of iSCs.

The autophagy inducer SMER28 attenuates microtubule dynamics mediating neuroprotection

SMER28 originated from a screen for small molecules that act as modulators of autophagy. SMER28 enhanced the clearance of autophagic substrates such as mutant huntingtin, which was additive to rapamycin-induced autophagy. Thus, SMER28 was established as a positive regulator of autophagy acting independently of the mTOR pathway, increasing autophagosome biosynthesis and attenuating mutant huntingtin-fragment toxicity in cellular- and fruit fly disease models, suggesting therapeutic potential. Despite many previous studies, molecular mechanisms mediating SMER28 activities and its direct targets have remained elusive. Here we analyzed the effects of SMER28 on cells and found that aside from autophagy induction, it significantly stabilizes microtubules and decelerates microtubule dynamics. Moreover, we report that SMER28 displays neurotrophic and neuroprotective effects at the cellular level by inducing neurite outgrowth and protecting from excitotoxin-induced axon degeneration. Finally, we compare the effects of SMER28 with other autophagy-inducing or microtubule-stabilizing drugs: whereas SMER28 and rapamycin both induce autophagy, the latter does not stabilize microtubules, and whereas both SMER28 and epothilone B stabilize microtubules, epothilone B does not stimulate autophagy. Thus, the effect of SMER28 on cells in general and neurons in particular is based on its unique spectrum of bioactivities distinct from other known microtubule-stabilizing or autophagy-inducing drugs.

Copper Modulates Adult Neurogenesis in Brain Subventricular Zone

The subventricular zone (SVZ) in lateral ventricles is the largest neurogenic region in adult brain containing high amounts of copper (Cu). This study aims to define the role of Cu in adult neurogenesis by chelating labile Cu ions using a well-established Cu chelator D-Penicillamine (D-Pen). A neurosphere model derived from adult mouse SVZ tissues was established and characterized for its functionality with regards to neural stem/progenitor cells (NSPCs). Applying D-Pen in cultured neurospheres significantly reduced intracellular Cu levels and reversed the Cu-induced suppression of NSPC’s differentiation and migration. An in vivo intracerebroventricular (ICV) infusion model was subsequently established to infuse D-Pen directly into the lateral ventricle. Metal analyses revealed a selective reduction of Cu in SVZ by 13.1% (p = 0.19) and 21.4% (p < 0.05) following D-Pen infusions at low (0.075 μg/h) and high (0.75 μg/h) doses for 28 days, respectively, compared to saline-infused controls. Immunohistochemical studies revealed that the 7-day, low-dose D-Pen infusion significantly increased Ki67(+)/Nestin(+) cell counts in SVZ by 28% (p < 0.05). Quantification of BrdU(+)/doublecortin (DCX)(+) newborn neuroblasts in the rostral migration stream (RMS) and olfactory bulb (OB) further revealed that the short-term, low-dose D-Pen infusion, as compared with saline-infused controls, resulted in more newborn neuroblasts in OB, while the high-dose D-Pen infusion showed fewer newborn neuroblasts in OB but with more arrested in the RMS. Long-term (28-day) infusion revealed similar outcomes. The qPCR data from neurosphere experiments revealed altered expressions of mRNAs encoding key proteins known to regulate SVZ adult neurogenesis, including, but not limited to, Shh, Dlx2, and Slit1, in response to the changed Cu level in neurospheres. Further immunohistochemical data indicated that Cu chelation also altered the expression of high-affinity copper uptake protein 1 (CTR1) and metallothionein-3 (MT3) in the SVZ as well as CTR1 in the choroid plexus, a tissue regulating brain Cu homeostasis. Taken together, this study provides first-hand evidence that a high Cu level in SVZ appears likely to maintain the stability of adult neurogenesis in this neurogenic zone.

Metabolic control of adult neural stem cell self-renewal by the mitochondrial protease YME1L

The transition between quiescence and activation in neural stem and progenitor cells (NSPCs) is coupled with reversible changes in energy metabolism with key implications for lifelong NSPC self-renewal and neurogenesis. How this metabolic plasticity is ensured between NSPC activity states is unclear. We find that a state-specific rewiring of the mitochondrial proteome by the i-AAA peptidase YME1L is required to preserve NSPC self-renewal. YME1L controls the abundance of numerous mitochondrial substrates in quiescent NSPCs, and its deletion activates a differentiation program characterized by broad metabolic changes causing the irreversible shift away from a fatty-acid-oxidation-dependent state. Conditional Yme1l deletion in adult NSPCs in vivo results in defective self-renewal and premature differentiation, ultimately leading to NSPC pool depletion. Our results disclose an important role for YME1L in coordinating the switch between metabolic states of NSPCs and suggest that NSPC fate is regulated by compartmentalized changes in protein network dynamics.

Anti-excitotoxicity and neuroprotective action of asiaticoside encapsulated polymeric nanoparticles in pilocarpine rodent seizure model

Asiaticoside (ASI), an ursane-type triterpenoid saponin, isolated from the memory enhancing herb Centella asiatica, is known for its neuroprotective activities. Here the anti-excitotoxicity and neuro protective effects of ASI encapsulated alginate chitosan nanoparticles (ACNPs) were evaluated in pilocarpine (PC) induced seizure in mice model. ACNPs were prepared by ionic gelation-polyelectrolyte complex method and their physicochemical characterization was carried out by TEM, SEM, DLS, XRD and FT-IR. Subsequently their encapsulation efficiency (EE), in vitro drug release, cell viability, seizure score, DNA fragmentation and mRNA expression of regulatory stress markers were evaluated. Membrane permeability of ACNPs in brain, histopathology and biological TEM and SEM analyses were also carried out. TEM of ACNPs showed spherical morphology with a particle size of 200-400 nm. DLS of ACNPs displayed an average size of 486.2 nm with polydispersity index (PDI) of 0.567 and zeta potential of -14.1 mV. ACNPs achieved high EE (> 90%) and controlled release (10%). Biological evaluation studies revealed ACNPs as non-toxic to mouse neural stem cells (mNSCs). They displayed enhanced brain permeability and attenuated seizure. Our results confirmed ACNPs as effective in crossing the brain membrane barrier and mitigating seizure severity induced by PC.

Direct FACS Isolation of Neural Stem/Progenitor Lineages from the Adult Brain

Adult neural stem and progenitor cells reside in the neurogenic niche of the adult brain and have tremendous potential in regenerative medicine. Compelling evidence suggests that adult neurogenesis plays an important role in hippocampal memory formation, plasticity, and mood regulation. Understanding the mechanisms that regulate the function of neural stem/progenitor cells within the brain is a critical step for the development of regenerative strategies to maintain or enhance neurological function. A major challenge in studying these cells is the limited cell number of adult neural stem cells, and the significant changes in their properties induced by in vitro culture and expansion. To best understand the regulation of these cells, they must be studied within their niche context. In this chapter, we provide a simplified protocol for the harvest and isolation of neural stem cell lineages directly from the murine brain, to provide input material for single-cell RNA-seq. This approach will elucidate the true transcriptional signatures and activated pathways in neural stem cell lineages, within the context of their niche environment.

Using a Digital Twin of an Electrical Stimulation Device to Monitor and Control the Electrical Stimulation of Cells in vitro

Electrical stimulation for application in tissue engineering and regenerative medicine has received increasing attention in recent years. A variety of stimulation methods, waveforms and amplitudes have been studied. However, a clear choice of optimal stimulation parameters is still not available and is complicated by ambiguous reporting standards. In order to understand underlying cellular mechanisms affected by the electrical stimulation, the knowledge of the actual prevailing field strength or current density is required. Here, we present a comprehensive digital representation, a digital twin, of a basic electrical stimulation device for the electrical stimulation of cells in vitro. The effect of electrochemical processes at the electrode surface was experimentally characterised and integrated into a numerical model of the electrical stimulation. Uncertainty quantification techniques were used to identify the influence of model uncertainties on relevant observables. Different stimulation protocols were compared and it was assessed if the information contained in the monitored stimulation pulses could be related to the stimulation model. We found that our approach permits to model and simulate the recorded rectangular waveforms such that local electric field strengths become accessible. Moreover, we could predict stimulation voltages and currents reliably. This enabled us to define a controlled stimulation setting and to identify significant temperature changes of the cell culture in the monitored voltage data. Eventually, we give an outlook on how the presented methods can be applied in more complex situations such as the stimulation of hydrogels or tissue in vivo.

High throughput screening of novel AAV capsids identifies variants for transduction of adult NSCs within the subventricular zone

The adult mammalian brain entails a reservoir of neural stem cells (NSCs) generating glial cells and neurons. However, NSCs become increasingly quiescent with age, which hampers their regenerative capacity. New means are therefore required to genetically modify adult NSCs for re-enabling endogenous brain repair. Recombinant adeno-associated viruses (AAVs) are ideal gene-therapy vectors due to an excellent safety profile and high transduction efficiency. We thus conducted a high-throughput screening of 177 intraventricularly injected barcoded AAV variants profiled by RNA sequencing. Quantification of barcoded AAV mRNAs identified two synthetic capsids, peptide-modified derivative of wild-type AAV9 (AAV9_A2) and peptide-modified derivative of wild-type AAV1 (AAV1_P5), both of which transduce active and quiescent NSCs. Further optimization of AAV1_P5 by judicious selection of the promoter and dose of injected viral genomes enabled labeling of 30%–60% of the NSC compartment, which was validated by fluorescence-activated cell sorting (FACS) analyses and single-cell RNA sequencing. Importantly, transduced NSCs readily produced neurons. The present study identifies AAV variants with a high regional tropism toward the ventricular-subventricular zone (v-SVZ) with high efficiency in targeting adult NSCs, thereby paving the way for preclinical testing of regenerative gene therapy.

Stimulation of the Migration and Expansion of Adult Mouse Neural Stem Cells by the FPR2-Specific Peptide WKYMVm

Neural stem cells (NSCs) are multipotent cells capable of self-renewal and differentiation into different nervous system cells. Mouse NSCs (mNSCs) are useful tools for studying neurogenesis and the therapeutic applications of neurodegenerative diseases in mammals. Formyl peptide receptor 2 (FPR2), expressed in the central nervous system and brain, is involved in the migration and differentiation of murine embryonic-derived NSCs. In this study, we explored the effect of FPR2 activation in adult mNSCs using the synthetic peptide Trp-Lys-Tyr-Met-Val-D-Met-NH2 (WKYMVm), an agonist of FPR2. After isolation of NSCs from the subventricular zone of the adult mouse brain, they were cultured in two culture systems—neurospheres or adherent monolayers—to demonstrate the expression of NSC markers and phenotypes. Under different conditions, mNSCs differentiated into neurons and glial cells such as astrocytes, microglia, and oligodendrocytes. Treatment with WKYMVm stimulated the chemotactic migration of mNSCs. Moreover, WKYMVm-treated mNSCs were found to promote proliferation; this result was confirmed by the expansion of mNSCs in Matrigel and the increase in the number of Ki67-positive cells. Incubation of mNSCs with WKYMVm in a supplement-free medium enhanced the survival rate of the mNSCs. Together, these results suggest that WKYMVm-induced activation of FPR2 stimulates cellular responses in adult NSCs.

Mouse Neural Stem Cell Differentiation and Human Adipose Mesenchymal Stem Cell Transdifferentiation Into Neuron- and Oligodendrocyte-like Cells With Myelination Potential

Stem cell therapy is an interesting approach for neural repair, once it can improve and increase processes, like angiogenesis, neurogenesis, and synaptic plasticity. In this regard, adult neural stem cells (NSC) are studied for their mechanisms of proliferation, differentiation and functionality in neural repair. Here, we describe novel neural differentiation methods. NSC from adult mouse brains and human adipose-derived stem cells (hADSC) were isolated and characterized regarding their neural differentiation potential based on neural marker expression profiles. For both cell types, their capabilities of differentiating into neuron-, astrocyte- and oligodendrocytes-like cells (NLC, ALC and OLC, respectively) were analyzed. Our methodologies were capable of producing NLC, ALC and OLC from adult murine and human transdifferentiated NSC. NSC showed augmented gene expression of NES, TUJ1, GFAP and PDGFRA/Cnp. Following differentiation induction into NLC, OLC or ALC, specific neural phenotypes were obtained expressing MAP2, GalC/O4 or GFAP with compatible morphologies, respectively. Accordingly, immunostaining for nestin⁺ in NSC, GFAP⁺ in astrocytes and GalC/O4⁺ in oligodendrocytes was detected. Co-cultured NLC and OLC showed excitability in 81.3% of cells and 23.5% of neuron/oligodendrocyte marker expression overlap indicating occurrence of in vitro myelination. We show here that hADSC can be transdifferentiated into NSC and distinct neural phenotypes with the occurrence of neuron myelination in vitro, providing novel strategies for CNS regeneration therapy. Superior Part: Schematic organization of obtaining and generating hNSC from hADSC and differentiation processes and phenotypic expression of neuron, astrocyte and oligodendrocyte markers (MAP2, GFAP and O4, respectively) and stem cell marker (NES) of differentiating hNSC 14 days after induction. The nuclear staining in blue corresponds to DAPI. bar = 100 μm. Inferior part: Neural phenotype fates in diverse differentiation media. NES: nestin; GFAP: Glial fibrillary acidic protein. MAP2: Microtubule-associated protein 2. TUJ1: β-III tubulin. PDGFRA: PDGF receptor alpha. Two-way ANOVA with Bonferroni post-test with n = 3. * p < 0.05 and ** p < 0.01: (NSCiM1 NSC induction medium 1) vs differentiation media.

Isolation and characterization of neural stem/progenitor cells in the subventricular zone of the naked mole-rat brain

Background

The naked mole-rat (NMR) is the longest-lived rodent with a maximum lifespan of more than 37 years and shows a negligible senescence phenotype, suggesting that tissue stem cells of NMRs are highly capable of maintaining homeostasis. However, the properties of NMR tissue stem cells, including neural stem cells (NSCs), are largely unclear.

Methods

Neural stem/progenitor cells (NS/PCs) were isolated from the subventricular zone of the neonate NMR brain (NMR-NS/PCs) and cultured in neurosphere and adherent culture conditions. Expression of NSC markers and markers of neurons, astrocytes, and oligodendrocytes was analyzed by immunocytochemistry. In adherent culture conditions, the proliferation rate and cell cycle of NMR-NS/PCs were assessed and compared with those of NS/PCs from mice (mouse-NS/PCs). The DNA damage response to γ-irradiation was analyzed by immunocytochemistry and reverse transcription-quantitative PCR.

Results

NMR-NS/PCs expressed several NSC markers and differentiated into neurons, astrocytes, and oligodendrocytes. NMR-NS/PCs proliferated markedly slower than mouse-NS/PCs, and a higher percentage of NMR-NS/PCs than mouse-NS/PCs was in G0/G1 phase. Notably, upon γ-irradiation, NMR-NS/PCs exhibited a faster initiation of the DNA damage response and were less prone to dying than mouse-NS/PCs.

Conclusions

NMR-NS/PCs were successfully isolated and cultured. The slow proliferation of NMR-NS/PCs and their resistance to DNA damage may help to prevent stem cell exhaustion in the brain during the long lifespan of NMRs. Our findings provide novel insights into the mechanism underlying delayed aging of NMRs. Further analysis of NMR tissue stem cells may lead to the development of new strategies that can prevent aging in humans.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41232-021-00182-7.

Wnt/β-catenin signalling is dispensable for adult neural stem cell homeostasis and activation

Adult mouse hippocampal neural stem cells (NSCs) generate new neurons that integrate into existing hippocampal networks and modulate mood and memory. These NSCs are largely quiescent and are stimulated by niche signals to activate and produce neurons. Wnt/β-catenin signalling acts at different steps along the hippocampal neurogenic lineage, but whether it has a direct role in the regulation of NSCs remains unclear. Here, we used Wnt/β-catenin reporters and transcriptomic data from in vivo and in vitro models to show that adult NSCs respond to Wnt/β-catenin signalling. Wnt/β-catenin stimulation instructed the neuronal differentiation of proliferating NSCs and promoted the activation or differentiation of quiescent NSCs in a dose-dependent manner. However, deletion of β-catenin in NSCs did not affect either their activation or maintenance of their stem cell characteristics. Together, these results indicate that, although NSCs do respond to Wnt/β-catenin stimulation in a dose-dependent and state-specific manner, Wnt/β-catenin signalling is not cell-autonomously required to maintain NSC homeostasis, which reconciles some of the contradictions in the literature as to the role of Wnt/β-catenin signalling in adult hippocampal NSCs.

Summary: Wnt/β-catenin signalling stimulation promotes the exit from quiescence and differentiation of adult hippocampal neural stem cells but is dispensable for homeostatic neurogenesis in the dentate gyrus of young mice.

Optimal culture conditions for neurosphere formation and neuronal differentiation from human dental pulp stem cells

Objectives

Human dental pulp stem cells (DPSCs) have been used to regenerate damaged nervous tissues. However, the methods of committing DPSCs into neural stem/progenitor cells (NSPCs) or neurospheres are highly diverse, resulting in many neuronal differentiation outcomes. This study aims to validate an optimal protocol for inducing DPSCs into neurospheres and neurons.

Methodology

After isolation and characterization of mesenchymal stem cell identity, DPSCs were cultured in a NSPC induction medium and culture vessels. The durations of the culture, dissociation methods, and passage numbers of DPSCs were varied.

Results

Neurosphere formation requires a special surface that inhibits cell attachment. Five-days was the most appropriate duration for generating proliferative neurospheres and they strongly expressed Nestin, an NSPC marker. Neurosphere reformation after being dissociated by the Accutase enzyme was significantly higher than other methods. Passage number of DPSCs did not affect neurosphere formation, but did influence neuronal differentiation. We found that the cells expressing a neuronal marker, β-tubulin III, and exhibiting neuronal morphology were significantly higher in the early passage of the DPSCs.

Conclusion

These results suggest a guideline to obtain a high efficiency of neurospheres and neuronal differentiation from DPSCs for further study and neurodegeneration therapeutics.

Isolation of adult mouse hippocampal neural stem cells for fluorescence loss in photobleaching assays

This protocol describes the isolation and culturing of primary neural stem cells (NSCs) from the adult mouse hippocampus, followed by the experimental approach for fluorescence loss in photobleaching assays, previously used to characterize the presence of an endoplasmic reticulum (ER) membrane diffusion barrier. The assay described here can be used to study live asymmetry in the ER membrane or other organelles that is established in dividing NSCs.

For complete details on the use and execution of this protocol, please refer to Clay et al. (2014); bin Imtiaz et al. (2021); Lee et al. (2016); Luedeke et al. (2005); Moore et al. (2015); Shcheprova et al. (2008).

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Protocol describes the isolation of hippocampal neural stem cells (NSCs)

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Approach to culture NSCs for fluorescence loss in photobleaching (FLIP) assays

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FLIP assays of NSCs explained step by step

Comparison of the Characteristics of Breast Milk-derived Stem Cells with the Stem Cells Derived from the Other Sources: A Comparative Review

Breast milk (BrM) not only supplies nutrition, but it also contains a diverse population of cells. It has been estimated that up to 6% of the cells in human milk possess the characteristics of mesenchymal stem cells (MSC). Available data also indicate that these cells are multipotent and capable of self-renewal and differentiation with other cells. In this review, we have compared different characteristics, such as CD markers, differentiation capacity, and morphology of stem cells, derived from human breast milk (hBr-MSC) with human bone marrow (hBMSC), Wharton's jelly (WJMSC), and human adipose tissue (hADMSC). Through the literature review, it was revealed that human breast milk-derived stem cells specifically express a group of cell surface markers, including CD14, CD31, CD45, and CD86. Importantly, a group of markers, CD13, CD29, CD44, CD105, CD106, CD146, and CD166, were identified, which were common in the four sources of stem cells. WJMSC, hBMSC, hADMSC, and hBr-MSC are potently able to differentiate into the mesoderm, ectoderm, and endoderm cell lineages. The ability of hBr-MSCs todifferentiate into the neural stem cells, neurons, adipocyte, hepatocyte, chondrocyte, osteocyte, and cardiomyocytes has made these cells a promising source of stem cells in regenerative medicine, while isolation of stem cells from the commonly used sources, such as bone marrow, requires invasive procedures. Although autologous breast milk-derived stem cells are an accessible source for women who are in the lactation period, breast milk can be considered as a source of stem cells with high differentiation potential without any ethical concern.

Generation of mouse hippocampal neural precursor cell lines with CRISPR/Cas9-mediated gene knockouts

Genetic manipulation of neural precursor cells is an important tool to study mechanisms underlying proliferation, fate specification, and neuron formation. The CRISPR/Cas9 system enables efficient genome editing but requires the clonal expansion of cells containing the desired mutation. Here, we describe a protocol for the effective generation of clonal mouse hippocampal neural precursor lines with CRISPR/Cas9-based gene knockouts. Edited cell lines can be used to investigate gene regulatory networks driving neuronal differentiation and for modeling of diseases that involve hippocampal neurogenesis. For complete details on the use and execution of this protocol, please refer to Pötzsch et al. (2021).

Methamphetamine Enhances HIV-Induced Aberrant Proliferation of Neural Progenitor Cells via the FOXO3-Mediated Mechanism

Maintaining an intact pool of neural progenitor cells (NPCs) is crucial for generating new and functionally active neurons. Methamphetamine (METH) can exacerbate the HIV-induced deficit of adult neurogenesis; however, potential mechanisms of this influence are still poorly understood. In the present study, we present evidence that chronic exposure to METH combined with brain infection by EcoHIV results in enhanced proliferation of NPCs in the subventricular zone (SVZ) in mice. This effect was long-lasting as it was preserved ex vivo in NPCs isolated from the exposed mice over several passages in the absence of additional treatments. Increased proliferation in response to METH plus HIV was associated with dysregulation of cyclin B1 and cyclin D. Transcriptomic studies indicated that 27 out of the top 30 differentially expressed genes in response to METH plus EcoHIV were targets of the forkhead box O transcriptional factor (FOXO) and primarily FOXO3. Additional ex vivo studies and in vitro experiments using human NPCs exposed to METH and infected with HIV revealed upregulation of the CXCL12-CXCR4 axis, leading to activation of downstream pAkt and pErk, the pathways that can phosphorylate FOXO3 and force its exports from the nuclei into the cytoplasm. Indeed, nuclear expulsion of FOXO3 was demonstrated both in mice exposed to METH and infected with EcoHIV and in cell cultures of human NPCs. These results provide novel information that exposure to METH combined with HIV infection can induce aberrant proliferation of SVZ-derived NPCs and identifies CXCL12-CXCR4-Akt-1-mediated phosphorylation of FOXO3 as the mechanism responsible for this effect.

Human Breast Milk: Bioactive Components, from Stem Cells to Health Outcomes

PURPOSE OF REVIEW

Breast milk (BM) is a peculiar fluid owing unique properties and resulting the ideal food during early neonatal period. As widely known, it can improve the outcome of both neonate and lactating mother, influencing their whole life. BM is characterized by several beneficial components; among these, a great role is played by BM own and specific microbiome, deeply investigated in many studies. Moreover, the use of metabolomics in BM analysis allowed a better characterization of its metabolic pathways that vary according to lactation stage and neonatal gestational age. The aim of this review is to describe growth factors, cytokines, immunity mediators, and stem cells (SCs) contained in BM and investigate their functions and effects on neonatal outcome, especially focusing on immuno- and neurodevelopment.

RECENT FINDINGS

We evaluated recent and updated literature on this field. The article that we analyzed to write this review have been found in MEDLINE using breast milk-derived stem cells, biofactors, growth factors, breastfeeding-related outcomes, neurodevelopment, and neonatal immunological system as keywords. Discovering and characterizing BM components could result very useful to clarify the pathophysiology of their influence on neonatal growth and even to improve artificial formulations' composition. Moreover, since SCs abilities and their involvement in the development of several diseases, they could help to discover specific targets for new therapies. It could be useful to characterize BM-derived SC markers, properties, and variations during lactation stages, to understand their potential role in therapeutic applications, since they could be noninvasively isolated from BM. More studies will help to describe more in detail the characteristics of mother-to-child communication through breastfeeding and its potential role in the next future.

Cell population analysis of the adult murine subependymal neurogenic lineage by flow cytometry

This protocol provides a flow-cytometry-based procedure to classify and isolate all cells of the adult rodent subependymal zone (SEZ) neurogenic lineage, without the need for reporter mice, into different cell populations, including three neural stem cell (NSC) fractions with molecular signatures that are coherent with single-cell transcriptomics. Additionally, their cycling behavior can be assessed by means of 5-ethynyl-2′-deoxyuridine (EdU) incorporation. Our method allows the isolation of different NSC fractions and the functional assay of their cycling heterogeneity and quiescence-activation transitions.

For complete details on the use, execution, and outcomes of this protocol, please refer to Belenguer et al. (2021).

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The subependymal neurogenic lineage can be stratified with a set of surface markers

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Cytometry-based classification and isolation of three distinct neural stem cell states

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Nucleoside incorporation can be combined to score cycling dynamics and cell transitions

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Tips for accurate dissection of the subependymal neurogenic niche

Neurospheres: a potential in vitro model for the study of central nervous system disorders

Neurogenesis was believed to end after the period of embryonic development. However, the possibility of obtaining an expressive number of cells with functional neuronal characteristics implied a great advance in experimental research. New techniques have emerged to demonstrate that the birth of new neurons continues to occur in the adult brain. Two main rich sources of these cells are the subventricular zone (SVZ) and the subgranular zone of the hippocampal dentate gyrus (SGZ) where adult neural stem cells (aNSCs) have the ability to proliferate and differentiate into mature cell lines. The cultivation of neurospheres is a method to isolate, maintain and expand neural stem cells (NSCs) and has been used extensively by several research groups to analyze the biological properties of NSCs and their potential use in injured brains from animal models. Throughout this review, we highlight the areas where this type of cell culture has been applied and the advantages and limitations of using this model in experimental studies for the neurological clinical scenario.

Dlk1 dosage regulates hippocampal neurogenesis and cognition

Neurogenesis in the adult brain gives rise to functional neurons, which integrate into neuronal circuits and modulate neural plasticity. Sustained neurogenesis throughout life occurs in the subgranular zone (SGZ) of the dentate gyrus in the hippocampus and is hypothesized to be involved in behavioral/cognitive processes such as memory and in diseases. Genomic imprinting is of critical importance to brain development and normal behavior, and exemplifies how epigenetic states regulate genome function and gene dosage. While most genes are expressed from both alleles, imprinted genes are usually expressed from either the maternally or the paternally inherited chromosome. Here, we show that in contrast to its canonical imprinting in nonneurogenic regions, Delta-like homolog 1 (Dlk1) is expressed biallelically in the SGZ, and both parental alleles are required for stem cell behavior and normal adult neurogenesis in the hippocampus. To evaluate the effects of maternally, paternally, and biallelically inherited mutations within the Dlk1 gene in specific behavioral domains, we subjected Dlk1-mutant mice to a battery of tests that dissociate and evaluate the effects of Dlk1 dosage on spatial learning ability and on anxiety traits. Importantly, reduction in Dlk1 levels triggers specific cognitive abnormalities that affect aspects of discriminating differences in environmental stimuli, emphasizing the importance of selective absence of imprinting in this neurogenic niche.

The Neural Stem Cell Properties of PKD2L1+ Cerebrospinal Fluid-Contacting Neurons in vitro

Cerebrospinal fluid-touching neurons (CSF-cNs) exist in the region surrounding the central canal of the spinal cord, which locate in the adult neurogenic niche. Previous research showed that CSF-cNs expressed the molecular markers of immature neural cells in vivo. Here, we explored the potential of CSF-cNs as neural stem cell in intro. We first found that PKD2L1⁺ CSF-cNs, isolating by FACS using the molecular marker PKD2L1 of CSF-cNs, expressed neural stem cells markers like Nestin, Sox2, and GFAP by immunofluorescence staining. PKD2L1⁺ CSF-cNs were able to form neurospheres and passaged in vitro. Immunofluorescence staining showed that the neurospheres forming by PKD2L1⁺ CSF-cNs also expressed neural stem cell markers Nestin, Sox2 and GFAP. The neurospheres expressed proliferation markers Ki67 and PCNA by immunofluorescence staining, indicating that the neurospheres forming by PKD2L1⁺ CSF-cNs were proliferative. The neurospheres, forming by CSF-cNs, had the ability of differentiation into neurons, astrocytes, and oligodendrocytes. Collectively, our data suggested that PKD2L1⁺ CSF-cNs have the properties of neural stem cells in vitro and may provide a promising approach for the repair of spinal cord injury.

Coordinated changes in cellular behavior ensure the lifelong maintenance of the hippocampal stem cell population

Neural stem cell numbers fall rapidly in the hippocampus of juvenile mice but stabilize during adulthood, ensuring lifelong hippocampal neurogenesis. We show that this stabilization of stem cell numbers in young adults is the result of coordinated changes in stem cell behavior. Although proliferating neural stem cells in juveniles differentiate rapidly, they increasingly return to a resting state of shallow quiescence and progress through additional self-renewing divisions in adulthood. Single-cell transcriptomics, modeling, and label retention analyses indicate that resting cells have a higher activation rate and greater contribution to neurogenesis than dormant cells, which have not left quiescence. These changes in stem cell behavior result from a progressive reduction in expression of the pro-activation protein ASCL1 because of increased post-translational degradation. These cellular mechanisms help reconcile current contradictory models of hippocampal neural stem cell (NSC) dynamics and may contribute to the different rates of decline of hippocampal neurogenesis in mammalian species, including humans.

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More proliferating hippocampal stem cells return to shallow quiescence with age

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Dormant stem cells enter deeper quiescence with age

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These changes drive the transition from developmental to adult neurogenesis

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Increasing degradation of ASCL1 protein by HUWE1 coordinates these changes

Apple Peel and Flesh Contain Pro-neurogenic Compounds

As mammals evolved with exposure to particular diets, naturally abundant compounds may have become part of the set of environmental co-determinants that shaped brain structure and function. Here we investigated whether bioactive factors found in apples directly affect hippocampal neurogenesis in the adult mouse. We found that quercetin, the most abundant flavanol in apple peel, was anti-proliferative at high concentrations but pro-neurogenic at low concentrations. This was confirmed in vivo, with intraperitoneally delivered quercetin promoting survival and neuronal differentiation, without affecting proliferation. Using a bioassay-guided fractionation approach we also identified additional pro-neurogenic compounds in apple flesh that were not related to flavonoids. We found that 3,5-dihydroxybenzoic acid significantly increased neural precursor cell proliferation and neurogenesis. This work shows that both flavonoids and 3,5-dihydroxybenzoic acid are pro-neurogenic, not only by activating precursor cell proliferation but also by promoting cell-cycle exit, cellular survival, and neuronal differentiation.

ROS Dynamics Delineate Functional States of Hippocampal Neural Stem Cells and Link to Their Activity-Dependent Exit from Quiescence

Cellular redox states regulate the balance between stem cell maintenance and activation. Increased levels of intracellular reactive oxygen species (ROS) are linked to proliferation and lineage specification. In contrast to this general principle, we here show that in the hippocampus of adult mice, quiescent neural precursor cells (NPCs) maintain the highest ROS levels (hiROS). Classifying NPCs on the basis of cellular ROS content identified distinct functional states. Shifts in ROS content primed cells for a subsequent state transition, with lower ROS content marking proliferative activity and differentiation. Physical activity, a physiological activator of adult hippocampal neurogenesis, recruited hiROS NPCs into proliferation via a transient Nox2-dependent ROS surge. In the absence of Nox2, baseline neurogenesis was unaffected, but the activity-induced increase in proliferation disappeared. These results provide a metabolic classification of NPC functional states and describe a mechanism linking the modulation of cellular ROS by behavioral cues to the activation of adult NPCs.

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A ROS gradient delineates cell types in the course of adult hippocampal neurogenesis

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Quiescent hippocampal stem cells have unusually high intracellular ROS

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Physical activity recruits quiescent stem cells in a ROS-dependent manner

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NOX2 dependency distinguishes this recruitment from baseline proliferation

A Guide to Extract Spinal Cord for Translational Stem Cell Biology Research: Comparative Analysis of Adult Human, Porcine, and Rodent Spinal Cord Stem Cells

Improving the clinical translation of animal-based neural stem/progenitor cell (NSPC) therapies to humans requires an understanding of intrinsic human and animal cell characteristics. We report a novel in vitro method to assess spinal cord NSPCs from a small (rodent) and large (porcine) animal model in comparison to human NSPCs. To extract live adult human, porcine, and rodent spinal cord tissue, we illustrate a strategy using an anterior or posterior approach that was simulated in a porcine model. The initial expansion of primary NSPCs is carried out using the neurosphere assay followed by a pharmacological treatment phase during which NSPCs derived from humans, porcines, and rodents are assessed in parallel using the same defined parameters. Using this model, NSPCs from all species demonstrated multi-lineage differentiation and self-renewal. Importantly, these methods provide conditions to enable the direct comparison of species-dependent cell behavior in response to specific exogenous signals.

Activation of GPR40 induces hypothalamic neurogenesis through p38- and BDNF-dependent mechanisms

Hypothalamic adult neurogenesis provides the basis for renewal of neurons involved in the regulation of whole-body energy status. In addition to hormones, cytokines and growth factors, components of the diet, particularly fatty acids, have been shown to stimulate hypothalamic neurogenesis; however, the mechanisms behind this action are unknown. Here, we hypothesized that GPR40 (FFAR1), the receptor for medium and long chain unsaturated fatty acids, could mediate at least part of the neurogenic activity in the hypothalamus. We show that a GPR40 ligand increased hypothalamic cell proliferation and survival in adult mice. In postnatal generated neurospheres, acting in synergy with brain-derived neurotrophic factor (BDNF) and interleukin 6, GPR40 activation increased the expression of doublecortin during the early differentiation phase and of the mature neuronal marker, microtubule-associated protein 2 (MAP2), during the late differentiation phase. In Neuro-2a proliferative cell-line GPR40 activation increased BDNF expression and p38 activation. The chemical inhibition of p38 abolished GPR40 effect in inducing neurogenesis markers in neurospheres, whereas BDNF immunoneutralization inhibited GPR40-induced cell proliferation in the hypothalamus of adult mice. Thus, GPR40 acts through p38 and BDNF to induce hypothalamic neurogenesis. This study provides mechanistic advance in the understating of how a fatty acid receptor regulates adult hypothalamic neurogenesis.

Circadian glucocorticoid oscillations preserve a population of adult hippocampal neural stem cells in the aging brain

A decrease in adult hippocampal neurogenesis has been linked to age-related cognitive impairment. However, the mechanisms involved in this age-related reduction remain elusive. Glucocorticoid hormones (GC) are important regulators of neural stem/precursor cells (NSPC) proliferation. GC are released from the adrenal glands in ultradian secretory pulses that generate characteristic circadian oscillations. Here, we investigated the hypothesis that GC oscillations prevent NSPC activation and preserve a quiescent NSPC pool in the aging hippocampus. We found that hippocampal NSPC populations lacking expression of the glucocorticoid receptor (GR) decayed exponentially with age, while GR-positive populations decayed linearly and predominated in the hippocampus from middle age onwards. Importantly, GC oscillations controlled NSPC activation and GR knockdown reactivated NSPC proliferation in aged mice. When modeled in primary hippocampal NSPC cultures, GC oscillations control cell cycle progression and induce specific genome-wide DNA methylation profiles. GC oscillations induced lasting changes in the methylation state of a group of gene promoters associated with cell cycle regulation and the canonical Wnt signaling pathway. Finally, in a mouse model of accelerated aging, we show that disruption of GC oscillations induces lasting changes in dendritic complexity, spine numbers and morphology of newborn granule neurons. Together, these results indicate that GC oscillations preserve a population of GR-expressing NSPC during aging, preventing their activation possibly by epigenetic programming through methylation of specific gene promoters. Our observations suggest a novel mechanism mediated by GC that controls NSPC proliferation and preserves a dormant NSPC pool, possibly contributing to a neuroplasticity reserve in the aging brain.

Decreased nuclear Pten in neural stem cells contributes to deficits in neuronal maturation

BACKGROUND

PTEN, a syndromic autism spectrum disorder (ASD) risk gene, is mutated in approximately 10% of macrocephalic ASD cases. Despite the described genetic association between PTEN and ASD and ensuing studies, we continue to have a limited understanding of how PTEN disruption drives ASD pathogenesis and maintenance.

METHODS

We derived neural stem cells (NSCs) from the dentate gyrus (DG) of Pten^m3m4 mice, a model that recapitulates PTEN-ASD phenotypes. We subsequently characterized the expression of stemness factors, proliferation, and differentiation of neurons and glia in Pten^m3m4 NSCs using immunofluorescent and immunoblotting approaches. We also measured Creb phosphorylation by Western blot analysis and expression of Creb-regulated genes with qRT-PCR.

RESULTS

The m3m4 mutation decreases Pten localization to the nucleus and its global expression over time. Pten^m3m4 NSCs exhibit persistent stemness characteristics associated with increased proliferation and a resistance to neuronal maturation during differentiation. Given the increased proliferation of Pten^m3m4 NSCs, a significant increase in the population of immature neurons relative to mature neurons occurs, an approximately tenfold decrease in the ratio between the homozygous mutant and wildtype. There is an opposite pattern of differentiation in some Pten^m3m4 glia, specifically an increase in astrocytes. These aberrant differentiation patterns associate with changes in Creb activation in Pten^m3m4/m3m4 NSCs. We specifically observed loss of Creb phosphorylation at S133 in Pten^m3m4/m3m4 NSCs and a subsequent decrease in expression of Creb-regulated genes important to neuronal function (i.e., Bdnf). Interestingly, Bdnf treatment is able to partially rescue the stunted neuronal maturation phenotype in Pten^m3m4/m3m4 NSCs.

CONCLUSIONS

Constitutional disruption of Pten nuclear localization with subsequent global decrease in Pten expression generates abnormal patterns of differentiation, a stunting of neuronal maturation. The propensity of Pten disruption to restrain neurons to a more progenitor-like state may be an important feature contributing to PTEN-ASD pathogenesis.

Manipulating Adult Neural Stem and Progenitor Cells with G-Quadruplex Ligands

G-quadruplexes are pervasive nucleic acid secondary structures in mammalian genomes and transcriptomes that regulate gene expression and genome duplication. Small molecule ligands that modify the stability of G-quadruplexes are widely studied in cancer, but whether G-quadruplex ligands can also be used to manipulate cell function under normal development and homeostatic conditions is largely unexplored. Here we show that two related G-quadruplex ligands (pyridostatin and carboxypyridostatin) can reduce proliferation of adult neural stem cell and progenitor cells derived from the adult mouse subventricular zone both in vitro and in vivo. Studies with neurosphere cultures show that pyridostatin reduces proliferation by a mechanism associated with DNA damage and cell death. By contrast, selectively targeting RNA G-quadruplex stability with carboxypyridostatin diminishes proliferation through a mechanism that promotes cell cycle exit and the production of oligodendrocyte progenitors. The ability to generate oligodendrocyte progenitors by targeting RNA G-quadruplex stability, however, is dependent on the cellular environment. Together, these findings show that ligands that can selectively stabilize RNA G-quadruplexes are an important, new class of molecular tool for neural stem and progenitor cell engineering, whereas ligands that target DNA G-quadruplexes have limited utility due to their toxicity.

Differentiation Drives Widespread Rewiring of the Neural Stem Cell Chaperone Network

Neural stem and progenitor cells (NSPCs) are critical for continued cellular replacement in the adult brain. Lifelong maintenance of a functional NSPC pool necessitates stringent mechanisms to preserve a pristine proteome. We find that the NSPC chaperone network robustly maintains misfolded protein solubility and stress resilience through high levels of the ATP-dependent chaperonin TRiC/CCT. Strikingly, NSPC differentiation rewires the cellular chaperone network, reducing TRiC/CCT levels and inducing those of the ATP-independent small heat shock proteins (sHSPs). This switches the proteostasis strategy in neural progeny cells to promote sequestration of misfolded proteins into protective inclusions. The chaperone network of NSPCs is more effective than that of differentiated cells, leading to improved management of proteotoxic stress and amyloidogenic proteins. However, NSPC proteostasis is impaired by brain aging. The less efficient chaperone network of differentiated neural progeny may contribute to their enhanced susceptibility to neurodegenerative diseases characterized by aberrant protein misfolding and aggregation.

Tailored Lipoprotein-Like miRNA Delivery Nanostructure Suppresses Glioma Stemness and Drug Resistance through Receptor-Stimulated Macropinocytosis

Glioma initiating cells (GICs) function as the seed for the propagation and relapse of glioma. Designing a smart and efficient strategy to target the GICs and to suppress the multiple signaling pathways associated with stemness and chemoresistance is essential to achieving a cancer cure. Inspired by the metabolic difference in endocytosis between GICs, differentiated glioma cells, and normal cells, a tailored lipoprotein-like nanostructure is developed to amplify their internalization into GICs through receptor-stimulated macropinocytosis. As CXCR4 is highly expressed on GICs and glioma tumor sites, meanwhile, the activation of CXCR4 induces the receptor-stimulated macropinocytosis pathway in GICs, this CXCR4 receptor-stimulated lipoprotein-like nanoparticle (SLNP) achieves efficient accumulation in GICs in vitro and in vivo. By carrying microRNA-34a in the core, this tailored SLNP reduces sex-determining region Y-box 2 and Notch1 expression, powerfully inhibits GICs stemness and chemoresistance, and significantly prolongs the survival of GICs-bearing mice. Taken together, a tailored lipoprotein-based nanostructure realizes efficient GICs accumulation and therapeutic effect through receptor-stimulated macropinocytosis, providing a powerful nanoplatform for RNA interference drugs to combat glioma.

Type 1 Interleukin-4 Signaling Obliterates Mouse Astroglia in vivo but Not in vitro

Recent findings suggest that reduced neurogenesis could be one of the underlying reasons for the exacerbated neuropathology in humans, thus restoring the neural stem cell proliferation and neurogenesis could help to circumvent some pathological aspects of Alzheimer’s disease. We recently identified Interleukin-4/STAT6 signaling as a neuron–glia crosstalk mechanism that enables glial proliferation and neurogenesis in adult zebrafish brain and 3D cultures of human astroglia, which manifest neurogenic properties. In this study, by using single cell sequencing in the APP/PS1dE9 mouse model of AD, we found that IL4 receptor (Il4r) is not expressed in mouse astroglia and IL4 signaling is not active in these cells. We tested whether activating IL4/STAT6 signaling would enhance cell proliferation and neurogenesis in healthy and disease conditions. Lentivirus-mediated expression of IL4R or constitutively active STAT6VT impaired the survival capacity of mouse astroglia in vivo but not in vitro. These results suggest that the adult mouse brain generates a non-permissive environment that dictates a negative effect of IL4 signaling on astroglial survival and neurogenic properties in contrast to zebrafish brains and in vitro mammalian cell cultures. Our findings that IL4R signaling in dentate gyrus (DG) of adult mouse brain impinges on the survival of DG cells implicate an evolutionary mechanism that might underlie the loss of neuroregenerative ability of the brain, which might be utilized for basic and clinical aspects for neurodegenerative diseases.

Static and dynamic 3D culture of neural precursor cells on macroporous cryogel microcarriers

Neural precursor cells have been much studied to further our understanding of the far-reaching and controversial question of adult neurogenesis. Currently, differentiation of primary neural precursor cells from the mouse dentate gyrus via 2-dimentional in vitro culture yields low numbers of neurons, a major hindrance to the field of study. 3-dimentional “neurosphere” culture allows better 3D cell-cell contact, but control over cell differentiation is poor because nutrition and oxygen restrictions at the core of the sphere causes spontaneous differentiation, predominantly to glial cells, not neurons. Our group has developed macroporous scaffolds, which overcome the above-mentioned problems, allowing long-term culture of neural stem cells, which can be differentiated into a much higher yield of neurons. Herein we describe a method for culturing neural precursor cells on RGD peptide functionalized-heparin containing cryogel scaffolds, either in standard non-adherent well-plates (static culture) or in spinner flasks (dynamic culture). This method includes:

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The synthesis and characterization of heparin based microcarriers.

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A “static” 3D culture method for that does not require spinner flask equipment.

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“Dynamic” culture in which cell loaded microcarriers are transferred to a spinner flask.

K-3-Rh Protects Against Cerebral Ischemia/Reperfusion Injury by Anti-Apoptotic Effect Through PI3K-Akt Signaling Pathway in Rat

BACKGROUND/AIMS

Ischemic stroke is the main cause of nerve damage and brain dysfunction, accompanied by strong brain cell apoptosis. This study aimed to investigate the effect of kaempferol-3-O-rhamnoside (K-3-rh) on cerebral ischemia-reperfusion (I/R) injury.

METHODS AND MATERIALS

A rat model of cerebral I/R injury was established. The effects of K-3-rh on cerebral infarction size, brain water content and neurological deficits in rats were evaluated. Apoptosis of ischemic brain cells after mouse I/R was observed by TUNEL staining and flow cytometry. Western blot and qRT-PCR were used to detect the effect of K-3-rh on the expression of apoptosis-related proteins.

RESULTS

K-3-rh can improve the neurological deficit score, reduce the infarct volume and brain water content, and inhibit cell apoptosis. In addition, K-3-rh significantly downregulated the expression of Bax and p53 and upregulated the expression of Bcl-2, and the phosphorylation level of Akt. Blockade of PI3K activity by the PI3K inhibitor wortmannin not only reversed the effects of K-3-rh on infarct volume and brain water content but also reversed the expression level of p-Akt.

CONCLUSION

K-3-rh had obvious neuroprotective effects on brain I/R injury and neuronal apoptosis, and its mechanism may be related to activation of PI3K/Akt signaling pathway.

Enhanced lysosomal degradation maintains the quiescent state of neural stem cells

Quiescence is important for sustaining neural stem cells (NSCs) in the adult brain over the lifespan. Lysosomes are digestive organelles that degrade membrane receptors after they undergo endolysosomal membrane trafficking. Enlarged lysosomes are present in quiescent NSCs (qNSCs) in the subventricular zone of the mouse brain, but it remains largely unknown how lysosomal function is involved in the quiescence. Here we show that qNSCs exhibit higher lysosomal activity and degrade activated EGF receptor by endolysosomal degradation more rapidly than proliferating NSCs. Chemical inhibition of lysosomal degradation in qNSCs prevents degradation of signaling receptors resulting in exit from quiescence. Furthermore, conditional knockout of TFEB, a lysosomal master regulator, delays NSCs quiescence in vitro and increases NSC proliferation in the dentate gyrus of mice. Taken together, our results demonstrate that enhanced lysosomal degradation is an important regulator of qNSC maintenance.

It remains unclear why quiescent neural stem cells (qNSCs) in the subventricular zone of the mouse brain have enlarged lysosomes. Here, authors demonstrate that qNSCs exhibit higher lysosomal activity and degrade activated EGF receptor by endolysosomal degradation more rapidly than proliferating NSCs, which prevents the NSC exit from quiescence.

Deficiency of Mitochondrial Aspartate-Glutamate Carrier 1 Leads to Oligodendrocyte Precursor Cell Proliferation Defects Both In Vitro and In Vivo

Aspartate-Glutamate Carrier 1 (AGC1) deficiency is a rare neurological disease caused by mutations in the solute carrier family 25, member 12 (SLC25A12) gene, encoding for the mitochondrial aspartate-glutamate carrier isoform 1 (AGC1), a component of the malate-aspartate NADH shuttle (MAS), expressed in excitable tissues only. AGC1 deficiency patients are children showing severe hypotonia, arrested psychomotor development, seizures and global hypomyelination. While the effect of AGC1 deficiency in neurons and neuronal function has been deeply studied, little is known about oligodendrocytes and their precursors, the brain cells involved in myelination. Here we studied the effect of AGC1 down-regulation on oligodendrocyte precursor cells (OPCs), using both in vitro and in vivo mouse disease models. In the cell model, we showed that a reduced expression of AGC1 induces a deficit of OPC proliferation leading to their spontaneous and precocious differentiation into oligodendrocytes. Interestingly, this effect seems to be related to a dysregulation in the expression of trophic factors and receptors involved in OPC proliferation/differentiation, such as Platelet-Derived Growth Factor α (PDGFα) and Transforming Growth Factor βs (TGFβs). We also confirmed the OPC reduction in vivo in AGC1-deficent mice, as well as a proliferation deficit in neurospheres from the Subventricular Zone (SVZ) of these animals, thus indicating that AGC1 reduction could affect the proliferation of different brain precursor cells. These data clearly show that AGC1 impairment alters myelination not only by acting on N-acetyl-aspartate production in neurons but also on OPC proliferation and suggest new potential therapeutic targets for the treatment of AGC1 deficiency.

RBM3 promotes neurogenesis in a niche-dependent manner via IMP2-IGF2 signaling pathway after hypoxic-ischemic brain injury

Hypoxic ischemia (HI) is an acute brain threat across all age groups. Therapeutic hypothermia ameliorates resulting injury in neonates but its side effects prevent routine use in adults. Hypothermia up-regulates a small protein subset that includes RNA-binding motif protein 3 (RBM3), which is neuroprotective under stressful conditions. Here we show how RBM3 stimulates neuronal differentiation and inhibits HI-induced apoptosis in the two areas of persistent adult neurogenesis, the subventricular zone (SVZ) and the subgranular zone (SGZ), while promoting neural stem/progenitor cell (NSPC) proliferation after HI injury only in the SGZ. RBM3 interacts with IGF2 mRNA binding protein 2 (IMP2), elevates its expression and thereby stimulates IGF2 release in SGZ but not SVZ-NSPCs. In summary, we describe niche-dependent regulation of neurogenesis after adult HI injury via the novel RBM3-IMP2-IGF2 signaling pathway.

Therapeutic hypothermia is a potent tool in the treatment of neonatal hypoxic-ischemic (HI) injury, yet the underlying mechanisms remain unclear. Here, authors demonstrate how the RNA-binding motif protein RBM3, which is induced by mild cooling while global translation rate is slowed down, contributes substantially to neuroregeneration after adult HI injury, specifically in the subventricular zone and subgranular zone.

DSCR1-mediated TET1 splicing regulates miR-124 expression to control adult hippocampal neurogenesis

Whether epigenetic factors such as DNA methylation and microRNAs interact to control adult hippocampal neurogenesis is not fully understood. Here, we show that Down syndrome critical region 1 (DSCR1) protein plays a key role in adult hippocampal neurogenesis by modulating two epigenetic factors: TET1 and miR-124. We find that DSCR1 mutant mice have impaired adult hippocampal neurogenesis. DSCR1 binds to TET1 introns to regulate splicing of TET1, thereby modulating TET1 level. Furthermore, TET1 controls the demethylation of the miRNA-124 promoter to modulate miR-124 expression. Correcting the level of TET1 in DSCR1 knockout mice is sufficient to prevent defective adult neurogenesis. Importantly, restoring DSCR1 level in a Down syndrome mouse model effectively rescued adult neurogenesis and learning and memory deficits. Our study reveals that DSCR1 plays a critical upstream role in epigenetic regulation of adult neurogenesis and provides insights into potential therapeutic strategy for treating cognitive defects in Down syndrome.

Differentiation Induction as a Response to Irradiation in Neural Stem Cells In Vitro

Radiotherapy plays a significant role in brain cancer treatment; however, the use of this therapy is often accompanied by neurocognitive decline that is, at least partially, a consequence of radiation-induced damage to neural stem cell populations. Our findings describe features that define the response of neural stem cells (NSCs) to ionizing radiation. We investigated the effects of irradiation on neural stem cells isolated from the ventricular-subventricular zone of mouse brain and cultivated in vitro. Our findings describe the increased transcriptional activity of p53 targets and proliferative arrest after irradiation. Moreover, we show that most cells do not undergo apoptosis after irradiation but rather cease proliferation and start a differentiation program. Induction of differentiation and the demonstrated potential of irradiated cells to differentiate into neurons may represent a mechanism whereby damaged NSCs eliminate potentially hazardous cells and circumvent the debilitating consequences of cumulative DNA damage.