Adult Hippocampal Progenitor Research Articles

The Bioactive Gamma-Oryzanol from Oryza sativa L. Promotes Neuronal Differentiation in Different In Vitro and In Vivo Models.

Gamma-oryzanol (ORY), found in rice (Oryza sativa L.), is a mixture of ferulic acid esters with triterpene alcohols, well-known for its antioxidant and anti-inflammatory properties. Our past research demonstrated its positive impact on cognitive function in adult mice, influencing synaptic plasticity and neuroprotection. In this study, we explored whether ORY can exert neuro-differentiating effects by using different experimental models. For this purpose, chemical characterization identified four components that are most abundant in ORY. In human neuroblastoma cells, we showed ORY's ability to stimulate neurite outgrowth, upregulating the expression of GAP43, BDNF, and TrkB genes. In addition, ORY was found to guide adult mouse hippocampal neural progenitor cells (NPCs) toward a neuronal commitment. Microinjection of ORY in zebrafish Tg (-3.1 neurog1:GFP) amplified neurog1-GFP signal, islet1, and bdnf mRNA levels. Zebrafish nrf2a and nrf2b morphants (MOs) were utilized to assess ORY effects in the presence or absence of Nrf2. Notably, ORY's ability to activate bdnf was nullified in nrf2a-MO and nrf2b-MO. Furthermore, computational analysis suggested ORY's single components have different affinities for the Keap1-Kelch domain. In conclusion, although more in-depth studies are needed, our findings position ORY as a potential source of bioactive molecules with neuro-differentiating potential involving the Nrf2 pathway.

Assessment of the Behaviors of an In Vitro Brain Model On-Chip under Shockwave Impacts.

Herein we report the assessment of the effects of shockwave (SW) impacts on adult rat hippocampal progenitor cell (AHPC) neurospheres (NSs), which are used as in vitro brain models, for enhancing our understanding of the mechanisms of traumatic brain injury (TBI). The assessment has been achieved by using culture dishes and a new microchip. The microchip allows the chemicals released from the brain models cultured inside the cell culture chamber under SW impacts to diffuse to the nanosensors in adjacent sensor chambers through built-in diffusion barriers, which are used to prevent the cells from entering the sensor chambers, thereby mitigating the biofouling issues of the sensor surface. Experiments showed the negative impact of the SW on the viability, proliferation, and differentiation of the cells within the NSs. A qPCR gene expression analysis was performed and appeared to confirm some of the immunocytochemistry (ICC) results. Finally, we demonstrated that the microchip can be used to monitor lactate dehydrogenase (LDH) released from the AHPC-NSs subjected to SW impacts. As expected, LDH levels changed when AHPC-NSs were injured by SW impacts, verifying this chip can be used for assessing the degrees of injuries to AHPC-NSs by monitoring LDH levels. Taken together, these results suggest the feasibility of using the chip to better understand the interactions between SW impacts and in vitro brain models, paving the way for potentially establishing in vitro TBI models on a chip.

Chronic chemogenetic activation of hippocampal progenitors enhances adult neurogenesis and modulates anxiety-like behavior and fear extinction learning

Adult hippocampal neurogenesis is a lifelong process that involves the integration of newborn neurons into the hippocampal network, and plays a role in cognitive function and the modulation of mood-related behavior. Here, we sought to address the impact of chemogenetic activation of adult hippocampal progenitors on distinct stages of progenitor development, including quiescent stem cell activation, progenitor turnover, differentiation and morphological maturation. We find that hM3Dq-DREADD-mediated activation of nestin-positive adult hippocampal progenitors recruits quiescent stem cells, enhances progenitor proliferation, increases doublecortin-positive newborn neuron number, accompanied by an acceleration of differentiation and morphological maturation, associated with increased dendritic complexity. Behavioral analysis indicated anxiolytic behavioral responses in transgenic mice subjected to chemogenetic activation of adult hippocampal progenitors at timepoints when newborn neurons are predicted to integrate into the mature hippocampal network. Furthermore, we noted an enhanced fear memory extinction on a contextual fear memory learning task in transgenic mice subjected to chemogenetic activation of adult hippocampal progenitors. Our findings indicate that hM3Dq-DREAD-mediated chemogenetic activation of adult hippocampal progenitors impacts distinct aspects of hippocampal neurogenesis, associated with the regulation of anxiety-like behavior and fear memory extinction.

An integrated microfluidic chip for studying the effects of neurotransmitters on neurospheroids.

To improve our understanding of how the central nervous system functions in health and disease, we report the development of an integrated chip for studying the effects of the neurotransmitters dopamine and serotonin on adult rat hippocampal progenitor cell (AHPC) neurospheroids. This chip allows dopamine or serotonin located in one chamber to diffuse to AHPC neurospheroids cultured in an adjacent chamber through a built-in diffusion barrier created by an array of intentionally misaligned micropillars. The gaps among the micropillars are filled with porous poly(ethylene glycol) (PEG) gel to tune the permeability of the diffusion barrier. An electrochemical sensor is also integrated within the chamber where the neurospheroids can be cultured, thereby allowing monitoring of the concentrations of dopamine or serotonin. Experiments show that concentrations of the neurotransmitters inside the neurospheroid chamber can be increased over a period of several hours to over 10 days by controlling the compositions of the PEG gel inside the diffusion barrier. The AHPC neurospheroids cultured in the chip remain highly viable following dopamine or serotonin treatment. Cell proliferation and neuronal differentiation have also been observed following treatment, revealing that the AHPC neurospheroids are a valuable in vitro brain model for neurogenesis research. Finally, we show that by tuning the permeability of diffusion barrier, we can block transfer of Escherichia coli cells across the diffusion barrier, while allowing dopamine or serotonin to pass through. These results suggest the feasibility of using the chip to better understand the interactions between microbiota and brain via the gut-brain axis.

The metabolic regulator USF-1 is involved in the control of affective behaviour in mice

Epidemiological studies indicate a bidirectional association between metabolic disturbances, including obesity and related pathological states, and mood disorders, most prominently major depression. However, the biological mechanisms mediating the comorbid relationship between the deranged metabolic and mood states remain incompletely understood. Here, we tested the hypothesis that the enhanced activation of brown fat tissue (BAT), known to beneficially regulate obesity and accompanying dysfunctional metabolic states, is also paralleled by an alteration of affective behaviour. We used upstream stimulatory factor 1 (USF-1) knock-out (KO) mice as a genetic model of constitutively activated BAT and positive cardiometabolic traits and found a reduction of depression-like and anxiety-like behaviours associated with USF-1 deficiency. Surgical removal of interscapular BAT did not impact the behavioural phenotype of USF-1 KO mice. Further, the absence of USF-1 did not lead to alterations of adult hippocampal neural progenitor cell proliferation, differentiation, or survival. RNA-seq analysis characterised the molecular signature of USF-1 deficiency in the hippocampus and revealed a significant increase in the expression of several members of the X-linked lymphocyte-regulated (xlr) genes, including xlr3b and xlr4b. Xlr genes are the mouse orthologues of the human FAM9 gene family and are implicated in the regulation of dendritic branching, dendritic spine number and morphology. The transcriptional changes were associated with morphological alterations in hippocampal neurons, manifested in reduced dendritic length and complexity in USF-1 KO mice. Collectively these data suggest that the metabolic regulator USF-1 is involved in the control of affective behaviour in mice and that this modulation of mood states is unrelated to USF-1-dependent BAT activation, but reflected in structural changes in the brain.

Genetic loss of norepinephrine does not alter adult hippocampal neurogenesis in dopamine beta-hydroxylase deficient mice.

Norepinephrine (NE), and specific adrenoceptors, have been reported to influence distinct aspects of adult hippocampal neurogenesis, including latent stem cell activation, progenitor proliferation, and differentiation. These findings are predominantly based on the use of pharmacological approaches in both in vitro and in vivo systems. Here, we sought to assess the consequences of genetic ablation of NE on adult hippocampal neurogenesis, by examining dopamine β hydroxylase knockout (Dbh -/-) mice, which lack NE from birth. We find that Dbh -/- mice exhibit no difference in adult hippocampal progenitor proliferation and survival. Further, the number of immature newborn neurons, labeled using stage-specific developmental markers within the hippocampal neurogenic niche, was also unaltered in Dbh -/- mice. In contrast, the noradrenergic neurotoxin DSP-4, which had previously been shown to reduce adult hippocampal neurogenesis in rats, also resulted in a decline in hippocampal progenitor proliferation in C57/Bl6N mice. These findings indicate that pharmacological lesioning of noradrenergic afferents in adulthood, but not the complete genetic loss of NE from birth, impairs adult hippocampal neurogenesis in mice.

Protective Effects of a Polyphenol-Rich Blueberry Extract on Adult Human Neural Progenitor Cells.

The aging process impacts neural stem cells and causes a significant decline in neurogenesis that contributes to neuronal dysfunction leading to cognitive decline. Blueberries are rich in polyphenols and have been shown to improve cognition and memory in older humans. While our previous studies have shown that blueberry supplementations can increase neurogenesis in aged rodents, it is not clear whether this finding can be extrapolated to humans. We thus investigated the effects of blueberry treatments on adult hippocampal human neural progenitor cells (AHNPs) that are involved in neurogenesis and potentially in memory and other brain functions. Cultured AHNPs were treated with blueberry extract at different concentrations. Their viability, proliferation, and differentiation were evaluated with and without the presence of a cellular oxidative stressor, dopamine, and potential cellular mechanisms were also investigated. Our data showed that blueberry extract can significantly increase the viability and proliferation rates of control hippocampal AHNPs and can also reverse decreases in viability and proliferation induced by the cellular stressor dopamine. These effects may be associated with blueberry’s anti-inflammatory, antioxidant, and calcium-buffering properties. Polyphenol-rich berry extracts thus confer a neuroprotective effect on human hippocampal progenitor cells in vitro.

Distinct Actions of the Thyroid Hormone Transporters Mct8 and Oatp1c1 in Murine Adult Hippocampal Neurogenesis.

Inactivating mutations in the thyroid hormone (TH) transporter monocarboxylate transporter 8 (MCT8) result in Allan-Herndon-Dudley Syndrome, a severe form of psychomotor retardation, while inactivating mutations in another TH transporter, organic anion transporting polypeptide 1c1 (OATP1C1), are linked to juvenile neurodegeneration. These diseases point to essential roles for TH transporters in CNS function. We recently defined the presence of Mct8 in adult hippocampal progenitors and mature granule cell neurons and unraveled cell-autonomous and indirect requirements for Mct8 in adult hippocampal neurogenesis. Here, we investigated whether Oatp1c1 is involved in the hippocampal neurogenic process in concert with Mct8. We detected Oatp1c1 gene expression activity and transcripts in subsets of progenitors, neurons and niche cells in the dentate gyrus. Absence of Oatp1c1 resulted in increased neuroblast and reduced immature neuron numbers in 6-month-old Oatp1c1ko and Mct8/Oatp1c1 double knockout (M/Odko) mice. Reduced EdU-label retention in Mct8ko and M/Odko mice confirmed the impact of Mct8 on neuron formation. In contrast, no significant effect of Oatp1c1 loss on granule cell neuron production and anxiety-like behavior in the open field arena were seen. Together, our results reinforce that distinct actions of each TH transporter are required at multiple stages to ensure proper adult hippocampal neurogenesis.

A Microfluidic Chip for Growth and Characterization of Adult Rat Hippocampal Progenitor Cell Neurospheroids

Adult hippocampal neural stem/progenitor cells (AHPCs), which are self-renewing multipotent progenitors that can differentiate into neurons, astrocytes, and oligodendrocytes, are suitable as a central nervous system (CNS) molecular model, and the formation of 3D AHPC neurospheroids are potentially suitable as an in vitro brain model. In this paper we report a new microfluidic chip to culture AHPC neurospheroids (NSs-AHPC) inside culture-chambers on chip. After cell fixation and immunostaining were conducted, the fluorescence images of NSs-AHPC were analyzed. It has been found that the AHPCs comprising neurospheroids remained highly viable. Cell proliferation and neuronal differentiation have also been observed, indicating the feasibility of NSs-AHPC as the in vitro brain model on chip. Given its simple-to-use, low-cost, and orderly arranged culture-chambers, this type of chip is particularly suitable for culturing and analyzing multiple in vitro brain models in an efficient manner. [2021-0199]

Robust Transcriptional Profiling and Identification of Differentially Expressed Genes With Low Input RNA Sequencing of Adult Hippocampal Neural Stem and Progenitor Populations

Multipotent neural stem cells (NSCs) are found in several isolated niches of the adult mammalian brain where they have unique potential to assist in tissue repair. Modern transcriptomics offer high-throughput methods for identifying disease or injury associated gene expression signatures in endogenous adult NSCs, but they require adaptation to accommodate the rarity of NSCs. Bulk RNA sequencing (RNAseq) of NSCs requires pooling several mice, which impedes application to labor-intensive injury models. Alternatively, single cell RNAseq can profile hundreds to thousands of cells from a single mouse and is increasingly used to study NSCs. The consequences of the low RNA input from a single NSC on downstream identification of differentially expressed genes (DEGs) remains insufficiently explored. Here, to clarify the role that low RNA input plays in NSC DEG identification, we directly compared DEGs in an oxidative stress model of cultured NSCs by bulk and single cell sequencing. While both methods yielded DEGs that were replicable, single cell sequencing using the 10X Chromium platform yielded DEGs derived from genes with higher relative transcript counts compared to non-DEGs and exhibited smaller fold changes than DEGs identified by bulk RNAseq. The loss of high fold-change DEGs in the single cell platform presents an important limitation for identifying disease-relevant genes. To facilitate identification of such genes, we determined an RNA-input threshold that enables transcriptional profiling of NSCs comparable to standard bulk sequencing and used it to establish a workflow for in vivo profiling of endogenous NSCs. We then applied this workflow to identify DEGs after lateral fluid percussion injury, a labor-intensive animal model of traumatic brain injury. Our work joins an emerging body of evidence suggesting that single cell RNA sequencing may underestimate the diversity of pathologic DEGs. However, our data also suggest that population level transcriptomic analysis can be adapted to capture more of these DEGs with similar efficacy and diversity as standard bulk sequencing. Together, our data and workflow will be useful for investigators interested in understanding and manipulating adult hippocampal NSC responses to various stimuli.

H3K9 Methyltransferases Suv39h1 and Suv39h2 Control the Differentiation of Neural Progenitor Cells in the Adult Hippocampus.

In the dentate gyrus of the adult hippocampus new neurons are generated from neural precursor cells through different stages including proliferation and differentiation of neural progenitor cells and maturation of newborn neurons. These stages are controlled by the expression of specific transcription factors and epigenetic mechanisms, which together orchestrate the progression of the neurogenic process. However, little is known about the involvement of histone posttranslational modifications, a crucial epigenetic mechanism in embryonic neurogenesis that regulates fate commitment and neuronal differentiation. During embryonic development, the repressive modification trimethylation of histone H3 on lysine 9 (H3K9me3) contributes to the cellular identity of different cell-types. However, the role of this modification and its H3K9 methyltransferases has not been elucidated in adult hippocampal neurogenesis. We determined that during the stages of neurogenesis in the adult mouse dentate gyrus and in cultured adult hippocampal progenitors (AHPs), there was a dynamic change in the expression and distribution of H3K9me3, being enriched at early stages of the neurogenic process. A similar pattern was observed in the hippocampus for the dimethylation of histone H3 on lysine 9 (H3K9me2), another repressive modification. Among H3K9 methyltransferases, the enzymes Suv39h1 and Suv39h2 exhibited high levels of expression at early stages of neurogenesis and their expression decreased upon differentiation. Pharmacological inhibition of these enzymes by chaetocin in AHPs reduced H3K9me3 and concomitantly decreased neuronal differentiation while increasing proliferation. Moreover, Suv39h1 and Suv39h2 knockdown in newborn cells of the adult mouse dentate gyrus by retrovirus-mediated RNA interference impaired neuronal differentiation of progenitor cells. Our results indicate that H3K9me3 and H3K9 methyltransferases Suv39h1 and Suv39h2 are critically involved in the regulation of adult hippocampal neurogenesis by controlling the differentiation of neural progenitor cells.

Thyroid hormone regulation of adult hippocampal neurogenesis: Putative molecular and cellular mechanisms.

Adult hippocampal neurogenesis is sensitive to perturbations in thyroid hormone signaling, with evidence supporting a key role for thyroid hormone and thyroid hormone receptors (TRs) in the regulation of postmitotic progenitor survival and neuronal differentiation. In this book chapter we summarize the current understanding of the effects of thyroid hormone signaling on adult hippocampal progenitor development, and also critically address the role of TRs in regulation of distinct aspects of stage-specific hippocampal progenitor progression. We highlight actions of thyroid hormone on thyroid hormone responsive target genes, and the implications for hippocampal progenitor regulation. Given the influence of thyroid hormone on both mitochondrial and lipid metabolism, we discuss a putative role for regulation of metabolism in the effects of thyroid hormone on adult hippocampal neurogenesis. Finally, we highlight specific ideas that require detailed experimental investigation, and the need for future studies to obtain a deeper mechanistic insight into the influence of thyroid hormone and TRs in the developmental progression of adult hippocampal progenitors.

Adult neural stem cells have latent inflammatory potential that is kept suppressed by Tcf4 to facilitate adult neurogenesis.

Inflammation is known to adversely affect adult neurogenesis, wherein the source of inflammation is largely thought to be extraneous to the neurogenic niche. Here, we demonstrate that the adult hippocampal neural progenitors harbor an inflammatory potential that is proactively suppressed by transcription factor 4 (Tcf4). Deletion of Tcf4 in hippocampal nestin-expressing progenitors causes loss of proliferative capacity and acquisition of myeloid inflammatory properties. This transformation abolishes their differentiation potential and causes production of detrimental factors that adversely affect niche cells, causing inflammation in the dentate gyrus. Thus, on one hand, Tcf4 deletion causes abrogation of proliferative progenitors leading to reduction of adult neurogenesis, while on the other, their accompanying inflammatory transformation inflicts inflammation in the niche. Taken together, we provide the first evidence for a latent inflammatory potential of adult hippocampal neural progenitors and identify Tcf4 as a critical regulator that facilitates adult neurogenesis via proactive suppression of this detrimental potential.

GSK-3β S9A overexpression leads murine hippocampal neural precursors to acquire an astroglial phenotype in vivo.

The addition of new neurons to the existing hippocampal circuitry persists in the adult dentate gyrus (DG). During this process, named adult hippocampal neurogenesis (AHN), adult hippocampal progenitor cells (AHPs) give rise to newborn dentate granule cells (DGCs). The acquisition of a neuronal lineage by AHPs is tightly regulated by numerous signaling molecules and transcription factors. In this regard, glycogen synthase kinase 3β (GSK-3β) is a master regulator of the maturation of AHPs in vitro. Here we analyzed the cell-autonomous effects of overexpressing a constitutively active form of GSK-3β (GSK-3β S9A) in AHPs in vivo. To this end, we stereotaxically injected a GSK-3β S9A-encoding retrovirus (GSK-3β-V5) into the DG of young adult C57BL6/J Ola Hsd female mice and studied the cell lineage acquisition, migratory and marker expression patterns, and the morphological maturation of the infected cells over time. Strikingly, GSK-3β S9A-transduced cells expressed glial fibrillary acidic protein (GFAP) and NG2, thereby acquiring an immature astroglial phenotype, which differed markedly from the neuronal phenotype observed in cells transduced with a control retrovirus that encoded GFP. Accordingly, the morphology and migration patterns of cells transduced by the two retroviruses are remarkably divergent. These observations support the role of GSK-3β as a cornerstone that regulates the balance between new astocytes/neurons generated in the adult murine DG.

Poor Concordance of Floxed Sequence Recombination in Single Neural Stem Cells: Implications for Cell Autonomous Studies.

To manipulate target gene function in specific adult cell populations, tamoxifen (TAM)-dependent CreERT2 is widely used to drive inducible, site-specific recombination of loxP flanked sequences. In studies of cell autonomous target gene function, it is common practice to combine these CreERT2-lox systems with a ubiquitously expressed stop-floxed fluorescent reporter gene to identify single cells supposedly undergoing target gene recombination. Here, we studied the reliability of using Cre-induced recombination of one gene to predict recombination in another gene at the single-cell level in adult hippocampal neural stem and progenitor cells (NSPCs). Using both probabilistic predictions in a generic experimental paradigm, as well as a mouse model with two separate stop-floxed reporters plus a Nestin promoter-driven CreERT2, we found that, in individual cells, recombination of one gene was a poor predictor of recombination in another. This poor concordance in floxed sequence recombination across genes suggests that use of stop-floxed reporters to investigate cell autonomous gene function may not be universally reliable and could lead to false conclusions.

Defining the adult hippocampal neural stem cell secretome: In vivo versus in vitro transcriptomic differences and their correlation to secreted protein levels

Adult hippocampal neural stem and progenitor cells (NSPCs) secrete a variety of proteins that affect tissue function. Though several individual NSPC-derived proteins have been shown to impact key cellular processes, a broad characterization is lacking. Secretome profiling of low abundance stem cell populations is typically achieved via proteomic characterization of in vitro, isolated cells. Here, we identified hundreds of secreted proteins in conditioned media from in vitro adult mouse hippocampal NSPCs using an antibody array and mass spectrometry. Comparison of protein abundance between antibody array and mass spectrometry plus quantification of several key secreted proteins by ELISA revealed notable disconnect between methods in what proteins were identified as being high versus low abundance, suggesting that data from antibody arrays in particular should be approached with caution. We next assessed the NSPC secretome on a transcriptional level with single cell and bulk RNA sequencing (RNAseq) of cultured NSPCs. Comparison of RNAseq transcript levels of highly secreted proteins revealed that quantification of gene expression did not necessarily predict relative protein abundance. Interestingly, comparing our in vitro NSPC gene expression data with similar data from freshly isolated, in vivo hippocampal NSPCs revealed strong correlations in global gene expression between in vitro and in vivo NSPCs. Understanding the components and functions of the NSPC secretome is essential to understanding how these cells may modulate the hippocampal neurogenic niche. Cumulatively, our data emphasize the importance of using proteomics in conjunction with transcriptomics and highlights the need for better methods of unbiased secretome profiling.

The potential oncogenic role of the RAS-like GTP-binding gene RIT1 in glioblastoma.

Glioblastoma is the most common type of malignant brain tumors and the most feared cancer among adults. The poor prognosis among patients affected with this type of cancer is associated with its high-invasiveness and the lack of successful therapies. A comprehensive understanding for the early molecular mechanisms in glioblastoma would definitely enhance the diagnosis and the treatment strategies. Deregulated expression of key genes that are known to be involved in early neurogenesis could be the instigator of brain tumorigenesis. Ras Like Without CAAX 1 (RIT1) gene that encodes an unusual "orphan" GTPase protein belongs to this category of critical genes that are known to be involved in controlling sequential proliferation and differentiation of adult hippocampal neural progenitor cells. In this study, we surveyed RIT1 gene expression by in-silico approaches to determine its spatio-temporal pattern in glioblastoma. Our results revealed a significant and progressive upregulation of RIT1 mRNA levels in various publicly available datasets. RIT1 expression ranked among the top upregulated genes in glioblastoma cohorts and it correlated with poor overall survival. Genetic and epigenetic analysis of RIT1 didn't reveal any significant aberration that could underlie its deregulated expression. Yet, our results highlighted the possibility of its activity to be transcriptionally controlled by STAT3, one of the main players in the onset of glioblastoma. In conclusion, our study presented for the first time a potential oncogenic role for RIT1 in glioblastoma. Knowing that the RAS superfamily of proteins has created an evolution in the cancer field, RIT1 should be added to this list through further investigations on its possible usage as a biomarker and therapeutic target in glioblastoma.

Wnt5a promotes differentiation and development of adult-born neurons in the hippocampus by noncanonical Wnt signaling.

In the adult hippocampus, new neurons are generated in the dentate gyrus. The Wnt signaling pathway regulates this process, but little is known about the endogenous Wnt ligands involved. We investigated the role of Wnt5a on adult hippocampal neurogenesis. Wnt5a regulates neuronal morphogenesis during embryonic development, and maintains dendritic architecture of pyramidal neurons in the adult hippocampus. Here, we determined that Wnt5a knockdown in the mouse dentate gyrus by lentivirus-mediated shRNA impaired neuronal differentiation of progenitor cells, and reduced dendritic development of adult-born neurons. In cultured adult hippocampal progenitors (AHPs), Wnt5a knockdown reduced neuronal differentiation and morphological development of AHP-derived neurons, whereas treatment with Wnt5a had the opposite effect. Interestingly, no changes in astrocytic differentiation were observed in vivo or in vitro, suggesting that Wnt5a does not affect fate-commitment. By using specific inhibitors, we determined that Wnt5a signals through CaMKII to induce neurogenesis, and promotes dendritic development of newborn neurons through activating Wnt/JNK and Wnt/CaMKII signaling. Our results indicate Wnt5a as a niche factor in the adult hippocampus that promotes neuronal differentiation and development through activation of noncanonical Wnt signaling pathways.

Determination of Electrical Stimuli Parameters To Transdifferentiate Genetically Engineered Mesenchymal Stem Cells into Neuronal or Glial Lineages

This study investigated the effect of electrical stimuli parameters using graphene-based devices for the transdifferentiation of genetically engineered brain-derived neurotrophic factor (BDNF) hypersecreting mesenchymal stem cells (BDNF-MSCs) into neuronal or glial lineages. The results suggest that BDNF-MSCs have the tendency to transdifferentiate into both neuronal and Schwann cell (SC)-like phenotypes at lower voltages (25–50 mV). However, as the applied voltage changed from 25 to 100 mV at 50 Hz, the transdifferentiation of BDNF-MSCs yielded more into SC-like phenotypes and resulted in complete transdifferentiation into SC-like phenotypes at 100 mV and 50 Hz. With an increase in voltage to 100 mV, the complete transdifferentiation to SC-like phenotypes also resulted in enhanced paracrine activity leading to total secretion of nerve growth factor (NGF) up to 50 ng/mL with pronounced biological activity, causing neurite extension of 4 μm/cell on PC12-TrkB cells. Moreover, 90% of the transdifferentiated cells demonstrated significant myelination potential. The contact co-culture of BDNF-MSCs with adult hippocampal progenitor cells (AHPCs) in the presence of electrical stimuli resulted in differentiation of BDNF-MSCs into SC-like phenotypes accompanied by synergistic neurite extension of AHPCs. Overall, this study demonstrates the possibility of controlling simultaneous and spatial differentiation of MSCs into selected neuronal and glial lineages at desired ratios via changes in electrical stimuli through graphene-based devices and can contribute to the development of novel cell-based strategies for nervous system rescue and repair. This work evaluates the effect of different electrical stimuli conditions applied through inkjet-printed and laser-annealed graphene-based interdigitated circuits on the differentiation behavior of mesenchymal stem cells. Our results suggested that it is possible to spatially and locally control the differentiation of mesenchymal stem cells into final lineage type (glial or neuronal) by manipulating the electrical stimuli. The future work will include the control of stem cell differentiation and fate commitment in an in vivo model using electrical stimuli.

Deficits in Enrichment-Dependent Neurogenesis and Enhanced Anxiety Behaviors Mediated by Expression of Alzheimer's Disease-Linked Ps1 Variants Are Rescued by Microglial Depletion.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that presently affects an estimated 5.7 million Americans. Understanding the basis for this disease is key for the development of a future successful treatment. In this effort, we previously reported that mouse prion protein-promoter-driven, ubiquitous expression of familial AD (FAD)-linked human PSEN1 variants in transgenic mice impairs environmental enrichment (EE)-induced proliferation and neurogenesis of adult hippocampal neural progenitor cells (AHNPCs) and in a non-cell autonomous manner. These findings were confirmed in PS1M146V/+ mice that harbor an FAD-linked mutation in the endogenous PSEN1 gene. We now demonstrate that CSF1R antagonist-mediated microglial depletion in transgenic male mice expressing mutant presenilin 1 (PS1) or PS1M146V/+ "knock-in" mice leads to a complete rescue of deficits in proliferation, differentiation and survival of AHNPCs. Moreover, microglia depletion suppressed the heightened baseline anxiety behavior observed in transgenic mice expressing mutant PS1 and PS1M146V/+ mice to levels observed in mice expressing wild-type human PS1 or nontransgenic mice, respectively. These findings demonstrate that in mice expressing FAD-linked PS1, microglia play a critical role in the regulation of EE-dependent AHNPC proliferation and neurogenesis and the modulation of affective behaviors.SIGNIFICANCE STATEMENT Inheritance of mutations in genes encoding presenilin 1 (PS1) causes familial Alzheimer's disease (FAD). Mutant PS1 expression enhances the levels and assembly of toxic Aβ42 peptides and impairs the self-renewal and neuronal differentiation of adult hippocampal neural progenitor cells (AHNPCs) following environmental enrichment (EE) that is associated with heightened baseline anxiety. We now show that microglial depletion fully restores the EE-mediated impairments in AHNPC phenotypes and suppresses the heightened baseline anxiety observed in mice expressing FAD-linked PS1. Thus, we conclude that the memory deficits and anxiety-related behaviors in patients with PS1 mutations is a reflection not just of an increase in the levels of Aβ42 peptides, but to impairments in the self-renewal and neuronal differentiation of AHNPCs that modulate affective behaviors.