Wnt signaling promotes neuronal differentiation from mesenchymal stem cells through activation of Tlx3

A prognostic model built on amino acid metabolism patterns in HPV-associated head and neck squamous cell carcinoma

OBJECTIVES

To compare amino acid metabolism patterns between HPV-positive and HPV-negative head and neck squamous cell carcinoma (HNSCC) patients and identify key genes for a prognostic model.

DESIGN

Utilizing the Cancer Genome Atlas dataset, we analyzed amino acid metabolism genes, differentiated genes between HPV statuses, and selected key genes via LASSO regression for the prognostic model. The model's gene expression was verified through immunohistochemistry in clinical samples. Functional enrichment and CIBERSORTx analyses explored biological functions, molecular mechanisms, and immune cell correlations. The model's prognostic capability was assessed using nomograms, calibration, and decision curve analysis.

RESULTS

We identified 1157 key genes associated with amino acid metabolism in HNSCC and HPV status. The prognostic model, featuring genes like IQCN, SLC22A1, SYT12, and TLX3, highlighted functions in development, metabolism, and pathways related to receptors and enzymes. It significantly correlated with immune cell infiltration and outperformed traditional staging in prognosis prediction, despite immunohistochemistry results showing limited clinical identification of HPV-related HNSCC.

CONCLUSIONS

Distinct amino acid metabolism patterns differentiate HPV-positive from negative HNSCC patients, underscoring the prognostic model's utility in predicting outcomes and guiding therapeutic strategies.

Rhoptry proteins affect the placental barrier in the context of Toxoplasma gondii infection: Signaling pathways and functions

Toxoplasma gondii is an opportunistic and pathogenic obligate intracellular parasitic protozoan that is widespread worldwide and can infect most warm-blooded animals, seriously endangering human health and affecting livestock production. Toxoplasmosis caused by T. gondii infection has different clinical manifestations, which are mainly determined by the virulence of T. gondii and host differences. Among the manifestations of this condition, abortion, stillbirth, and fetal malformation can occur if a woman is infected with T. gondii in early pregnancy. Here, we discuss how the T. gondii rhoptry protein affects host pregnancy outcomes and speculate on the related signaling pathways involved. The effects of rhoptry proteins of T. gondii on the placental barrier are complex. Rhoptry proteins not only regulate interferon-regulated genes (IRGs) to ensure the survival of parasites in activated cells but also promote the spread of worms in tissues and the invasive ability of the parasites. The functions of these rhoptry proteins and the associated signaling pathways highlight relevant mechanisms by which Toxoplasma crosses the placental barrier and influences fetal development and will guide future studies to uncover the complexity of the host-pathogen interactions.

KLF2 Regulates Neural Differentiation of Dental Pulp-derived Stem Cells by Modulating Autophagy and Mitophagy

BACKGROUND

Transplantation of stem cells for treating neurodegenerative disorders is a promising future therapeutic approach. However, the molecular mechanism underlying the neuronal differentiation of dental pulp-derived stem cells (DPSC) remains inadequately explored. The current study aims to define the regulatory role of KLF2 (Kruppel-like factor 2) during the neural differentiation (ND) of DPSC.

METHODS

We first investigated the transcriptional and translational expression of KLF2, autophagy, and mitophagy-associated markers during the ND of DPSC by using quantitative RT-PCR and western blot methods. After that, we applied the chemical-mediated loss- and gain-of-function approaches using KLF2 inhibitor, GGPP (geranylgeranyl pyrophosphate), and KLF2 activator, GGTI-298 (geranylgeranyl transferase inhibitor-298) to delineate the role of KLF2 during ND of DPSC. The western blot, qRT-PCR, and immunocytochemistry were performed to determine the molecular changes during ND after KLF2 deficiency and KLF2 sufficiency. We also analyzed the oxygen consumption rate (OCR) and the extracellular acidification rate (ECAR) using the Seahorse XFe24 analyzer.

RESULTS

Our study demonstrated that the expression level of KLF2, autophagy, and mitophagy-associated markers were significantly elevated during the ND of DPSC. Next, we found that the KLF2 inhibitor, GGPP significantly reduced the ND of DPSC. Inversely, KLF2 overexpression accelerated the molecular phenomenon of DPSC's commitment towards ND, indicating the crucial role of KLF2 in neurogenesis. Moreover, we found that the KLF2 positively regulated autophagy, mitophagy, and the Wnt5a signaling pathway during neurogenesis. Seahorse XFe24 analysis revealed that the ECAR and OCR parameters were significantly increased during ND, and inhibition of KLF2 marginally reversed them towards DPSC's cellular bioenergetics. However, KLF2 overexpression shifted the cellular energy metabolism toward the quiescent stage.

CONCLUSION

Collectively, our findings provide the first evidence that the KLF2 critically regulates the neurogenesis of DPSC by inducing autophagy and mitophagy.

Cell-Based Therapies for Glaucoma

Glaucomatous optic neuropathy (GON) is the major cause of irreversible visual loss worldwide and can result from a range of disease etiologies. The defining features of GON are retinal ganglion cell (RGC) degeneration and characteristic cupping of the optic nerve head (ONH) due to tissue remodeling, while intraocular pressure remains the only modifiable GON risk factor currently targeted by approved clinical treatment strategies. Efforts to understand the mechanisms that allow species such as the zebrafish to regenerate their retinal cells have greatly increased our understanding of regenerative signaling pathways. However, proper integration within the retina and projection to the brain by the newly regenerated neuronal cells remain major hurdles. Meanwhile, a range of methods for in vitro differentiation have been developed to derive retinal cells from a variety of cell sources, including embryonic and induced pluripotent stem cells. More recently, there has been growing interest in the implantation of glial cells as well as cell-derived products, including neurotrophins, microRNA, and extracellular vesicles, to provide functional support to vulnerable structures such as RGC axons and the ONH. These approaches offer the advantage of not relying upon the replacement of degenerated cells and potentially targeting earlier stages of disease pathogenesis. In order to translate these techniques into clinical practice, appropriate cell sourcing, robust differentiation protocols, and accurate implantation methods are crucial to the success of cell-based therapy in glaucoma. Translational Relevance: Cell-based therapies for glaucoma currently under active development include the induction of endogenous regeneration, implantation of exogenously derived retinal cells, and utilization of cell-derived products to provide functional support.

LNX2 involves in the role of ghrelin to promote the neuronal differentiation of adipose tissue-derived mesenchymal stem cells

Adipose tissue-derived mesenchymal stem cells (ADSCs) have promising effects on nerve repair due to the differentiation ability to neural cells. Ghrelin has been shown to promote the neural differentiation of ADSCs. This work was designed to explore its underlying mechanism. Herein, we found high expression of LNX2 in ADSCs after neuronal differentiation. Knockdown of LNX2 might block neuronal differentiation of ADSCs, as evidenced by the decreased number of neural-like cells and dendrites per cell, and the reduced expressions of neural markers (including β-Tubulin III, Nestin, and MAP2). We also demonstrated that LNX2 silencing suppressed the nuclear translocation of β-catenin in differentiated ADSCs. Luciferase reporter assay indicated that LNX2 inhibited wnt/β-catenin pathway by reducing its transcriptional activity. In addition, results showed that LNX2 expression was increased by ghrelin, and its inhibition diminished the effects of ghrelin on neuronal differentiation. Altogether, the results suggest that LNX2 is involved in the role of ghrelin to facilitate neuronal differentiation of ADSCs.

The biotoxin BMAA promotes dysfunction via distinct mechanisms in neuroblastoma and glioblastoma cells

Chronic exposure to the Cyanobacteria biotoxin Beta-methylamino-L-alanine (BMAA) has been associated with development of a sporadic form of ALS called Amyotrophic Lateral Sclerosis/Parkinsonism-Dementia Complex (ALS/PDC), as observed within certain Indigenous populations of Guam and Japan. Studies in primate models and cell culture have supported the association of BMAA with ALS/PDC, yet the pathological mechanisms at play remain incompletely characterized, effectively stalling the development of rationally-designed therapeutics or application of preventative measures for this disease. In this study we demonstrate for the first time that sub-excitotoxic doses of BMAA modulate the canonical Wnt signaling pathway to drive cellular defects in human neuroblastoma cells, suggesting a potential mechanism by which BMAA may promote neurological disease. Further, we demonstrate here that the effects of BMAA can be reversed in cell culture by use of pharmacological modulators of the Wnt pathway, revealing the potential value of targeting this pathway therapeutically. Interestingly, our results suggest the existence of a distinct Wnt-independent mechanism activated by BMAA in glioblastoma cells, highlighting the likelihood that neurological disease may result from the cumulative effects of distinct cell-type specific mechanisms of BMAA toxicity.

Stress Triggers Expression of Bovine Herpesvirus 1 Infected Cell Protein 4 (bICP4) RNA during Early Stages of Reactivation from Latency in Pharyngeal Tonsil

Bovine herpesvirus 1 (BoHV-1), an important pathogen of cattle, establishes lifelong latency in sensory neurons within trigeminal ganglia (TG) after acute infection. The BoHV-1 latency-reactivation cycle, like other alphaherpesvirinae subfamily members, is essential for viral persistence and transmission. Notably, cells within pharyngeal tonsil (PT) also support a quiescent or latent BoHV-1 infection. The synthetic corticosteroid dexamethasone, which mimics the effects of stress, consistently induces BoHV-1 reactivation from latency allowing early stages of viral reactivation to be examined in the natural host. Based on previous studies, we hypothesized that stress-induced cellular factors trigger expression of key viral transcriptional regulatory genes. To explore this hypothesis, RNA-sequencing studies compared viral gene expression in PT during early stages of dexamethasone-induced reactivation from latency. Strikingly, RNA encoding infected cell protein 4 (bICP4), which is translated into an essential viral transcriptional regulatory protein, was detected 30 min after dexamethasone treatment. Ninety minutes after dexamethasone treatment bICP4 and, to a lesser extent, bICP0 RNA were detected in PT. All lytic cycle viral transcripts were detected within 3 h after dexamethasone treatment. Surprisingly, the latency related (LR) gene, the only viral gene abundantly expressed in latently infected TG neurons, was not detected in PT during latency. In TG neurons, bICP0 and the viral tegument protein VP16 are expressed before bICP4 during reactivation, suggesting distinct viral regulatory genes mediate reactivation from latency in PT versus TG neurons. Finally, these studies confirm PT is a biologically relevant site for BoHV-1 latency, reactivation from latency, and virus transmission. IMPORTANCE BoHV-1, a neurotropic herpesvirus, establishes, maintains, and reactivates from latency in neurons. BoHV-1 DNA is also detected in pharyngeal tonsil (PT) from latently infected calves. RNA-sequencing studies revealed the viral infected cell protein 4 (bICP4) RNA was expressed in PT of latently infected calves within 30 min after dexamethasone was used to initiate reactivation. As expected, bICP4 RNA was not detected during latency. All lytic cycle viral genes were expressed within 3 h after dexamethasone treatment. Conversely, bICP0 and the viral tegument protein VP16 are expressed prior to bICP4 in trigeminal ganglionic neurons during reactivation. The viral latency related gene, which is abundantly expressed in latently infected neurons, was not abundantly expressed in PT during latency. These studies provide new evidence PT is a biologically relevant site for BoHV-1 latency and reactivation. Finally, we predict other alphaherpesvirinae subfamily members utilize PT as a site for latency and reactivation.

Genetic Mechanism Study of Auditory Phoenix Spheres and Transcription Factors Prediction for Direct Reprogramming by Bioinformatics

Background: Hearing loss is the most common irreversible sensory disorder. By delivering regenerative cells into the cochlea, cell-based therapy provides a novel strategy for hearing restoration. Recently, newly-identified phoenix cells have drawn attention due to their nearly unlimited self-renewal and neural differentiation capabilities. They are a promising cell source for cell therapy and a potential substitute for induced pluripotent stem cells (iPSCs) in many in vitro applications. However, the underlying genomic mechanism of their self-renewal capabilities is largely unknown. The aim of this study was to identify hub genes and potential molecular mechanisms between differentiated and undifferentiated phoenix cells and predict transcription factors (TFs) for direct reprogramming. Material and Methods: The datasets were downloaded from the ArrayExpress database. Samples of differentiated and undifferentiated phoenix cells with three biological replicates were utilised for bioinformatic analysis. Differentially expressed genes (DEGs) were screened and the Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment were investigated. The gene set enrichment analysis (GSEA) was conducted to verify the enrichment of four self-defined gene set collections, followed by protein-protein interaction (PPI) network construction and subcluster analysis. The prediction of TFs for direct reprogramming was performed based on the TRANSFAC database. Results: Ten hub genes were identified to be the key candidates for self-renewal. Ten TFs were predicted as the direct reprogramming factors. This study provides a theoretical foundation for understanding phoenix cells and clues for direct reprogramming, which would stimulate further experiments and clinical applications in hearing research and treatment.

Glyphosate-based herbicide induces long-lasting impairment in neuronal and glial differentiation

Glyphosate-based herbicides (GBH) are among the most sold pesticides in the world. There are several formulations based on the active ingredient glyphosate (GLY) used along with other chemicals to improve the absorption and penetration in plants. The final composition of commercial GBH may modify GLY toxicological profile, potentially enhancing its neurotoxic properties. The developing nervous system is particularly susceptible to insults occurring during the early phases of development, and exposure to chemicals in this period may lead to persistent impairments on neurogenesis and differentiation. The aim of this study was to evaluate the long-lasting effects of a sub-cytotoxic concentration, 2.5 parts per million of GBH and GLY, on the differentiation of human neuroepithelial stem cells (NES) derived from induced pluripotent stem cells (iPSC). We treated NES cells with each compound and evaluated the effects on key cellular processes, such as proliferation and differentiation in daughter cells never directly exposed to the toxicants. We found that GBH induced a more immature neuronal profile associated to increased PAX6, NESTIN and DCX expression, and a shift in the differentiation process toward glial cell fate at the expense of mature neurons, as shown by an increase in the glial markers GFAP, GLT1, GLAST and a decrease in MAP2. Such alterations were associated to dysregulation of key genes critically involved in neurogenesis, including PAX6, HES1, HES5, and DDK1. Altogether, the data indicate that subtoxic concentrations of GBH, but not of GLY, induce long-lasting impairments on the differentiation potential of NES cells.

Xenogenic Neural Stem Cell-Derived Extracellular Nanovesicles Modulate Human Mesenchymal Stem Cell Fate and Reconstruct Metabolomic Structure

Extracellular nanovesicles, particularly exosomes, can deliver their diverse bioactive biomolecular content, including miRNAs, proteins, and lipids, thus providing a context for investigating the capability of exosomes to induce stem cells toward lineage-specific cells and tissue regeneration. In this study, it is demonstrated that rat subventricular zone neural stem cell-derived exosomes (rSVZ-NSCExo) can control neural-lineage specification of human mesenchymal stem cells (hMSCs). Microarray analysis shows that the miRNA content of rSVZ-NSCExo is a faithful representation of rSVZ tissue. Through immunocytochemistry, gene expression, and multi-omics analyses, the capability to use rSVZ-NSCExo to induce hMSCs into a neuroglial or neural stem cell phenotype and genotype in a temporal and dose-dependent manner via multiple signaling pathways is demonstrated. The current study presents a new and innovative strategy to modulate hMSCs fate by harnessing the molecular content of exosomes, thus suggesting future opportunities for rSVZ-NSCExo in nerve tissue regeneration.

Transmembrane protein TMEM184B is necessary for interleukin-31-induced itch

ABSTRACT

Nociceptive and pruriceptive neurons in the dorsal root ganglia (DRG) convey sensations of pain and itch to the spinal cord, respectively. One subtype of mature DRG neurons, comprising 6% to 8% of neurons in the ganglia, is responsible for sensing mediators of acute itch and atopic dermatitis, including the cytokine IL-31. How itch-sensitive (pruriceptive) neurons are specified is unclear. Here, we show that transmembrane protein 184B (TMEM184B), a protein with roles in axon degeneration and nerve terminal maintenance, is required for the expression of a large cohort of itch receptors, including those for interleukin 31 (IL-31), leukotriene C4, and histamine. Male and female mice lacking TMEM184B show reduced responses to IL-31 but maintain normal responses to pain and mechanical force, indicating a specific behavioral defect in IL-31-induced pruriception. Calcium imaging experiments indicate that a reduction in IL-31-induced calcium entry is a likely contributor to this phenotype. We identified an early failure of proper Wnt-dependent transcriptional signatures and signaling components in Tmem184b mutant mice that may explain the improper DRG neuronal subtype specification. Accordingly, lentiviral re-expression of TMEM184B in mutant embryonic neurons restores Wnt signatures. Together, these data demonstrate that TMEM184B promotes adult somatosensation through developmental Wnt signaling and promotion of proper pruriceptive gene expression. Our data illuminate a new key regulatory step in the processes controlling the establishment of diversity in the somatosensory system.

Role of Neural Stem Cells and Vitamin D Receptor (VDR)-Mediated Cellular Signaling in the Mitigation of Neurological Diseases

Specific stem cell-based therapies for treating Alzheimer's disease, Parkinson's disease, and schizophrenia are gaining importance in recent years. Accumulating data is providing further support by demonstrating the efficacy of neural stem cells in enhancing the neurogenesis in the aging brain. In addition to stem cells, recent studies have shown the efficacy of supplementing vitamin D in promoting neurogenesis and neuronal survival. Studies have also demonstrated the presence of mutational variants and single-nucleotide polymorphisms of the vitamin D receptor (VDR) in neurological disorders; however, implications of these mutations in the pathophysiology and response to drug treatment are yet to be explored. Hence, in this article, we have reviewed recent reports pertaining to the role of neural stem cells and VDR-mediated cellular signaling cascades that are involved in enhancing the neurogenesis through Wnt/β-catenin and Sonic Hedgehog pathways. This review benefits neurobiologists and pharmaceutical industry experts to develop stem cell-based and vitamin D-based therapies to better treat the patients suffering from neurological diseases.

Exploration of the DARTable Genome- a Resource Enabling Data-Driven NAMs for Developmental and Reproductive Toxicity Prediction

The identification of developmental and reproductive toxicity (DART) is a critical component of toxicological evaluations of chemical safety. Adverse Outcome Pathways (AOPs) provide a framework to describe biological processes leading to a toxic effect and can provide insights in understanding the mechanisms underlying toxicological endpoints and aid the development of new approach methods (NAMs). Integrated approaches to testing and assessment (IATA) can be developed based on AOP knowledge and can serve as pragmatic approaches to chemical hazard characterization using NAMs. However, DART effects remain difficult to predict given the diversity of biological mechanisms operating during ontogenesis and consequently, the considerable number of potential molecular initiating events (MIEs) that might trigger a DART Adverse Outcome (DART AO). Consequently, two challenges that need to be overcome to create an AOP-based DART IATA are having sufficient knowledge of relevant biology and using this knowledge to determine the appropriate selection of cell systems that provide sufficient coverage of that biology. The wealth of modern biological and bioinformatics data can be used to provide this knowledge. Here we demonstrate the utility of bioinformatics analyses to address these questions. We integrated known DART MIEs with gene-developmental phenotype information to curate the hypothetical human DARTable genome (HDG, ∼5 k genes) which represents the comprehensive set of biomarkers for DART. Using network analysis of the human interactome, we show that HDG genes have distinct connectivity compared to other genes. HDG genes have higher node degree with lower neighborhood connectivity, betweenness centralities and average shortest path length. Therefore, HDG is highly connected to itself and to the wider network and not only to their local community. Also, by comparison with the Druggable Genome we show how the HDG can be prioritized to identify potential MIEs based on potential to interact with small molecules. We demonstrate how the HDG in combination with gene expression data can be used to select a panel of relevant cell lines (RD-1, OVCAR-3) for inclusion in an IATA and conclude that bioinformatic analyses can provide the necessary insights and serve as a resource for the development of a screening panel for a DART IATA.

Temporal and Spatial Transcriptomic Dynamics across Brain Development in Xenopus laevis tadpoles

Amphibian metamorphosis is a transitional period that involves significant changes in the cell type populations and biological processes occurring in the brain. Analysis of gene expression dynamics during this process may provide insight into the molecular events underlying these changes. We conducted differential gene expression analyses of the developing X. laevis tadpole brain during this period in two ways: first, over stages of development in the midbrain, and second, across regions of the brain at a single developmental stage. We found that genes pertaining to positive regulation of neural progenitor cell proliferation as well as known progenitor cell markers were upregulated in the midbrain prior to metamorphic climax; concurrently, expression of cell cycle timing regulators decreased across this period, supporting the notion that cell cycle lengthening contributes to a decrease in proliferation by the end of metamorphosis. We also found that at the start of metamorphosis, neural progenitor populations appeared to be similar across the fore-, mid-, and hindbrain regions. Genes pertaining to negative regulation of differentiation were upregulated in the spinal cord compared to the rest of the brain, however, suggesting that a different program may regulate neurogenesis there. Finally, we found that regulation of biological processes like cell fate commitment and synaptic signaling follow similar trajectories in the brain across early tadpole metamorphosis and mid- to late-embryonic mouse development. By comparing expression across both temporal and spatial conditions, we have been able to illuminate cell type and biological pathway dynamics in the brain during metamorphosis.

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.

Human induced pluripotent stem cells and CRISPR/Cas-mediated targeted genome editing: Platforms to tackle sensorineural hearing loss

Hearing loss (HL) is a major global health problem of pandemic proportions. The most common type of HL is sensorineural hearing loss (SNHL) which typically occurs when cells within the inner ear are damaged. Human induced pluripotent stem cells (hiPSCs) can be generated from any individual including those who suffer from different types of HL. The development of new differentiation protocols to obtain cells of the inner ear including hair cells (HCs) and spiral ganglion neurons (SGNs) promises to expedite cell-based therapy and screening of potential pharmacologic and genetic therapies using human models. Considering age-related, acoustic, ototoxic, and genetic insults which are the most frequent causes of irreversible damage of HCs and SGNs, new methods of genome editing (GE), especially the CRISPR/Cas9 technology, could bring additional opportunities to understand the pathogenesis of human SNHL and identify novel therapies. However, important challenges associated with both hiPSCs and GE need to be overcome before scientific discoveries are correctly translated to effective and patient-safe applications. The purpose of the present review is (a) to summarize the findings from published reports utilizing hiPSCs for studies of SNHL, hence complementing recent reviews focused on animal studies, and (b) to outline promising future directions for deciphering SNHL using disruptive molecular and genomic technologies.

Utility of Reactive Species Generation in Plasma Medicine for Neuronal Development

Reactive oxygen species (ROS) are critical signaling molecules for neuronal physiology that stimulate growth and development and play vital roles in several pathways when in a balanced state, but they cause neurodegeneration when unbalanced. As ROS levels above a certain threshold cause the activation of the autophagy system, moderate levels of ROS can be used as treatment strategies. Currently, such treatments are used together with low-level laser or photodynamic therapies, photo-bio modulation, or infrared treatments, in different chronic diseases but not in the treatment of neurodegeneration. Recently, non-thermal plasma has been successfully used in biomedical applications and treatments, and beneficial effects such as differentiation, cell growth, and proliferation, stimulation of ROS based pathways have been observed. Besides the activation of a wide range of biological signaling pathways by generating ROS, plasma application can be an effective treatment in neuronal regeneration, as well as in neuronal diseases. In this review, we summarize the generation and role of ROS in neurons and provide critical insights into their potential benefits on neurons. We also discuss the underlying mechanisms of ROS on neuronal development. Regarding clinical applications, we focus on ROS-based neuronal growth and regeneration strategies and in the usage of non-thermal plasma in neuronal and CNS injury treatments.

Stem cell-based approaches: Possible route to hearing restoration?

Disabling hearing loss is the most common sensorineural disability worldwide. It affects around 466 million people and its incidence is expected to rise to around 900 million people by 2050, according to World Health Organization estimates. Most cases of hearing impairment are due to the degeneration of hair cells (HCs) in the cochlea, mechano-receptors that transduce incoming sound information into electrical signals that are sent to the brain. Damage to these cells is mainly caused by exposure to aminoglycoside antibiotics and to some anti-cancer drugs such as cisplatin, loud sounds, age, infections and genetic mutations. Hearing deficits may also result from damage to the spiral ganglion neurons that innervate cochlear HCs. Differently from what is observed in avian and non-mammalian species, there is no regeneration of missing sensory cell types in the adult mammalian cochlea, what makes hearing loss an irreversible process. This review summarizes the research that has been conducted with the aim of developing cell-based strategies that lead to sensory cell replacement in the adult cochlea and, ultimately, to hearing restoration. Two main lines of research are discussed, one directed toward the transplantation of exogenous replacement cells into the damaged tissue, and another that aims at reactivating the regenerative potential of putative progenitor cells in the adult inner ear. Results from some of the studies that have been conducted are presented and the advantages and drawbacks of the various approaches discussed.

An engineered three-dimensional stem cell niche in the inner ear by applying a nanofibrillar cellulose hydrogel with a sustained-release neurotrophic factor delivery system

Although the application of human embryonic stem cells (hESCs) in stem cell-replacement therapy remains promising, its potential is hindered by a low cell survival rate in post-transplantation within the inner ear. Here, we aim to enhance the in vitro and in vivo survival rate and neuronal differentiation of otic neuronal progenitors (ONPs) by generating an artificial stem cell niche consisting of three-dimensional (3D) hESC-derived ONP spheroids with a nanofibrillar cellulose hydrogel and a sustained-release brain-derivative neurotrophic factor delivery system. Our results demonstrated that the transplanted hESC-derived ONP spheroids survived and neuronally differentiated into otic neuronal lineages in vitro and in vivo and also extended neurites toward the bony wall of the cochlea 90 days after the transplantation without the use of immunosuppressant medication. Our data in vitro and in vivo presented here provide sufficient evidence that we have established a robust, reproducible protocol for in vivo transplantation of hESC-derived ONPs to the inner ear. Using our protocol to create an artificial stem cell niche in the inner ear, it is now possible to work on integrating transplanted hESC-derived ONPs further and also to work toward achieving functional auditory neurons generated from hESCs. Our findings suggest that the provision of an artificial stem cell niche can be a future approach to stem cell-replacement therapy for inner-ear regeneration. STATEMENT OF SIGNIFICANCE: Inner ear regeneration utilizing human embryonic stem cell-derived otic neuronal progenitors (hESC-derived ONPs) has remarkable potential for treating sensorineural hearing loss. However, the local environment of the inner ear requires a suitable stem cell niche to allow hESC-derived ONP engraftment as well as neuronal differentiation. To overcome this obstacle, we utilized three-dimensional spheroid formation (direct contact), nanofibrillar cellulose hydrogel (extracellular matrix), and a neurotrophic factor delivery system to artificially create a stem cell niche in vitro and in vivo. Our in vitro and in vivo data presented here provide sufficient evidence that we have established a robust, reproducible protocol for in vivo transplantation of hESC-derived ONPs to the inner ear.

Herpes simplex virus 1 regulates β-catenin expression in TG neurons during the latency-reactivation cycle

When herpes simplex virus 1 (HSV-1) infection is initiated in the ocular, nasal, or oral cavity, sensory neurons within trigeminal ganglia (TG) become infected. Following a burst of viral transcription in TG neurons, lytic cycle viral genes are suppressed and latency is established. The latency-associated transcript (LAT) is the only viral gene abundantly expressed during latency, and LAT expression is important for the latency-reactivation cycle. Reactivation from latency is required for virus transmission and recurrent disease, including encephalitis. The Wnt/β-catenin signaling pathway is differentially expressed in TG during the bovine herpesvirus 1 latency-reactivation cycle. Hence, we hypothesized HSV-1 regulates the Wnt/β-catenin pathway and promotes maintenance of latency because this pathway enhances neuronal survival and axonal repair. New studies revealed β-catenin was expressed in significantly more TG neurons during latency compared to TG from uninfected mice or mice latently infected with a LAT-/- mutant virus. When TG explants were incubated with media containing dexamethasone to stimulate reactivation, significantly fewer β-catenin+ TG neurons were detected. Conversely, TG explants from uninfected mice or mice latently infected with a LAT-/- mutant increased the number of β-catenin+ TG neurons in the presence of DEX relative to samples not treated with DEX. Impairing Wnt signaling with small molecule antagonists reduced virus shedding during explant-induced reactivation. These studies suggested β-catenin was differentially expressed during the latency-reactivation cycle, in part due to LAT expression.

Differentiation of Mesenchymal Stem Cells to Neuroglia: in the Context of Cell Signalling

The promise of engineering specific cell types from stem cells and rebuilding damaged or diseased tissues has fascinated stem cell researchers and clinicians over last few decades. Mesenchymal Stem Cells (MSCs) have the potential to differentiate into non-mesodermal cells, particularly neural-lineage, consisting of neurons and glia. These multipotent adult stem cells can be used for implementing clinical trials in neural repair. Ongoing research identifies several molecular mechanisms involved in the speciation of neuroglia, which are tightly regulated and interconnected by various components of cell signalling machinery. Growing MSCs with multiple inducers in culture media will initiate changes on intricately interlinked cell signalling pathways and processes. Net result of these signal flow on cellular architecture is also dependent on the type of ligands and stem cells investigated in vitro. However, our understanding about this dynamic signalling machinery is limited and confounding, especially with spheroid structures, neurospheres and organoids. Therefore, the results for differentiating neurons and glia in vitro have been inconclusive, so far. Added to this complication, we have no convincing evidence about the electrical conductivity and functionality status generated in differentiating neurons and glia. This review has taken a step forward to tailor the information on differentiating neuroglia with the common methodologies, in practice.

Injury-preconditioning secretome of umbilical cord mesenchymal stem cells amplified the neurogenesis and cognitive recovery after severe traumatic brain injury in rats

Traumatic brain injury (TBI) is a dominant cause of death and permanent disability worldwide. Although TBI could significantly increase the proliferation of adult neural stem cells in the hippocampus, the survival and maturation of newborn cells is markedly low. Increasing evidence suggests that the secretome derived from mesenchymal stem cells (MSCs) would be an ideal alternative to MSC transplantation. The successive and microenvironmentally responsive secretion in MSCs may be critical for the functional benefits provided by transplanted MSCs after TBI. Therefore, it is reasonable to hypothesize that the signaling molecules secreted in response to local tissue damage can further facilitate the therapeutic effect of the MSC secretome. To simulate the complex microenvironment in the injured brain well, we used traumatically injured brain tissue extracts to pretreat umbilical cord mesenchymal stem cells (UCMSCs) in vitro and stereotaxically injected the secretome from traumatic injury-preconditioned UCMSCs into the dentate gyrus of the hippocampus in a rat severe TBI model. The results revealed that compared with the normal secretome, the traumatic injury-preconditioned secretome could significantly further promote the differentiation, migration, and maturation of newborn cells in the dentate gyrus and ultimately improve cognitive function after TBI. Cytokine antibody array suggested that the increased benefits of secretome administration were attributable to the newly produced proteins and up-regulated molecules from the MSC secretome preconditioned by a traumatically injured microenvironment. Our study utilized the traumatic injury-preconditioned secretome to amplify neurogenesis and improve cognitive recovery, suggesting this method may be a novel and safer candidate for nerve repair. Cover Image for this issue: doi: 10.1111/jnc.14741.

Lercanidipine boosts the efficacy of mesenchymal stem cell therapy in 3-NP-induced Huntington's disease model rats via modulation of the calcium/calcineurin/NFATc4 and Wnt/β-catenin signalling pathways

3-Nitropropionic acid (3-NP) induces a spectrum of Huntington's disease (HD)-like neuropathologies in the rat striatum. The present study aimed to demonstrate the neuroprotective effect of lercanidipine (LER) in rats with 3-NP-induced neurotoxicity, address the possible additional protective effect of combined treatment with bone marrow-derived mesenchymal stem cells (BM-MSCs) and LER, and investigate the possible involvement of the Ca²⁺/calcineurin (CaN)/nuclear factor of activated T cells c4 (NFATc4) and Wnt/β-catenin signalling pathways. Rats were injected with 3-NP (10 mg/kg/day, i.p.) for two weeks and were divided into four subgroups; the first served as the control HD group, the second received a daily dose of LER (0.5 mg/kg, i.p.), the third received a single injection of BM-MSCs (1 x 106/rat, i.v.) and the last received a combination of both BM-MSCs and LER. The combined therapy improved motor and behaviour performance. Meanwhile, this treatment led to a marked reduction in striatal cytosolic Ca^2+, CaN, tumour necrosis factor-alpha, and NFATc4 expression and the Bax/Bcl2 ratio. Combined therapy also increased striatal brain-derived neurotrophic factor, FOXP3, Wnt, and β-catenin protein expression. Furthermore, haematoxylin-eosin and Nissl staining revealed an amelioration of striatum tissue injury with the combined treatment. In conclusion, the current study provides evidence for a neuroprotective effect of LER and/or BM-MSCs in 3-NP-induced neurotoxicity in rats. Interestingly, combined LER/BM-MSC therapy was superior to cell therapy alone in inhibiting 3-NP-induced neurological insults via modulation of the Ca²⁺/CaN/NFATc4 and Wnt/β-catenin signalling pathways. LER/BM-MSC combined therapy may represent a feasible approach for improving the beneficial effects of stem cell therapy in HD.

Berberine Protects C17.2 Neural Stem Cells From Oxidative Damage Followed by Inducing Neuronal Differentiation

Neurodegeneration is the loss of structure and/or function of neurons. Oxidative stress has been suggested as one of the common etiology in most of the neurodegenerative diseases. Previous studies have demonstrated the beneficial effects of berberine in various neurodegenerative and neuropsychiatric disorders. In this study, we hypothesized that berberine could protect C17.2 neural stem cells (NSCs) from 2,2′-Azobis(2-amidinopropane) dihydrochloride (AAPH)-induced oxidative damage then promote neuronal differentiation. AAPH was used to induce oxidative damage. After the damage, berberine protected C17.2 cells were kept cultured for another week in differentiation medium with/without berberine. Changes in cell morphology were detected by microscopy and cell viability was determined by MTT assay. Real-time PCR and western blot analysis were performed to confirm the associated pathways. Berberine was able to protect C17.2 NSCs from the oxidative damage. It lowered the cellular reactive oxygen species (ROS) level in C17.2 cells via Nuclear Factor Erythroid 2-Related Factor 1/2 (NRF1/2) – NAD(P)H Quinone Dehydrogenase 1 (NQO-1) – Heme Oxygenase 1 (HO-1) pathway. It also down-regulated the apoptotic factors-Caspase 3 and Bcl2 Associated X (Bax) and upregulated the anti-apoptotic factor-Bcl2 to reduce cell apoptosis. Besides, berberine increased C17.2 cell viability via up-regulating Extracellular-signal-Related Kinase (ERK) and phosphor-Extracellular-signal-Related Kinase (pERK) expression. Then, berberine promoted C17.2 cell to differentiate into neurons and the differentiation mechanism involved the activation of WNT/β-catenin pathway as well as the upregulation of expression levels of pro-neural factors Achaete-Scute Complex-Like 1 (ASCL1), Neurogenin 1 (NeuroG1), Neuronal Differentiation 2 (NeuroD2) and Doublecortin (DCX). In conclusion, berberine protected C17.2 NSCs from oxidative damage then induced them to differentiate into neurons.

MicroRNA Profiling During Neural Differentiation of Induced Pluripotent Stem Cells

MicroRNAs (miRNA) play an essential role in the regulation of gene expression and influence signaling networks responsible for several cellular processes like differentiation of pluripotent stem cells. Despite several studies on the neurogenesis process, no global analysis of microRNA expression during differentiation of induced pluripotent stem cells (iPSC) to neuronal stem cells (NSC) has been done. Therefore, we compared the profile of microRNA expression in iPSC lines and in NSC lines derived from them, using microarray-based analysis. Two different protocols for NSC formation were used: Direct and two-step via neural rosette formation. We confirmed the new associations of previously described miRNAs in regulation of NSC differentiation from iPSC. We discovered upregulation of miR-10 family, miR-30 family and miR-9 family and downregulation of miR-302 and miR-515 family expression. Moreover, we showed that miR-10 family play a crucial role in the negative regulation of genes expression belonging to signaling pathways involved in neural differentiation: WNT signaling pathway, focal adhesion, and signaling pathways regulating pluripotency of stem cells.

TLX3 repressed SNAI1-induced epithelial-mesenchymal transition by directly constraining STAT3 phosphorylation and functionally sensitized 5-FU chemotherapy in hepatocellular carcinoma

TLX3 has an established role as a sequence-specific transcription factor with vital functions in the nervous system. Although several studies have shown that TLX3 is aberrantly up-regulated in leukemia, its expression and function in hepatocellular carcinoma (HCC) remain unknown. We found that TLX3 expression was decreased in 68/100 (68%) HCC cases and negatively correlated with the expression of p-STAT3, SNAI1, and Vimentin, while it was positively associated with E-cadherin expression. ITRAQ proteomic profiling revealed significantly less TLX3 expression in primary HCC tumors than in portal vein tumor thrombi. Comparison of Kaplan-Meier curves showed that down-regulation of TLX3 in HCC was associated with poor post-surgical survival. TLX3 over-expression inhibited HCC cell viability, proliferation, migration, invasion and enhanced 5-FU treatment, whereas silencing TLX3 produced the opposite results. Further experiments showed that TLX3 attenuated the EMT phenotype. In vivo experiments showed that knockdown of TLX3 promoted the growth of HCC xenografts and attenuated the anti-tumor effects of 5-FU treatment. Gene expression microarray analysis revealed that TLX3 inhibited IL-6/STAT3 signaling. In additional mechanistic studies TLX3 reversed the EMT phenotype of HCC cells by binding to STAT3, inhibiting STAT3 phosphorylation, and down-regulating SNAI1 expression. Taken together, loss of expression of TLX3 induces EMT by enhancing IL-6/STAT3/SNAI1 signaling, and accelerates HCC progression while also attenuated the effect of 5-FU on HCCs.

Protective effects of mesenchymal stem cells overexpressing extracellular regulating kinase 1/2 against stroke in rats

OBJECTIVE

Although transplantation of bone marrow-derived mesenchymal stem cells (MSCs) has shown beneficial effects on stroke, lower survival of MSCs limits effects. Extracellular regulating kinase 1/2 signaling (ERK1/2) is crucial for cell survival, differentiation, and proliferation. This study was designed to explore whether MSCs modified by over-expressing ERK1/2 may reinforce beneficial effects on stroke in rats.

METHODS

rat MSCs transfected with ERK1/2 and empty lentivirus to generate MSCs overexpressing ERK1/2 (ERK/MSCs) and MSCs (as a control), respectively. In vitro, ERK/MSCs were plated and exposed to glutamate-induced condition, and viability of ERK/MSCs was measured. Furthermore, neural induction of ERK/MSCs was investigated in vitro. Cerebral ischemic rats were induced by occluding middle cerebral artery, and then were stereotaxically injected into ipsilateral right lateral ventricle with ERK/MSCs or MSCs 3 days after stroke and survived for 7 or 14 days after injection.

RESULTS

ERK/MSCs showed better viability in physiological and glutamate-induced neurotoxic conditions compared to MSCs. After neural induction, more neurons were be differentiated from ERK/MSCs than from MSCs. After transplantation, more numbers of grafted cells and improved functional recovery were observed in ERK/MSCs-treated rats compared with MSCs-treated rats. Compared with MSCs treatment, ERK/MSCs treatment significantly increased proliferation of neural stem cells in the subventricle zone (SVZ) and the MAP2/nestin double-labeled cells adjacent to the SVZ, enhanced the numbers of reactive astrocytes while suppressed microglial activation. Besides, TNF-α level was elevated in ERK/MSCs-treated rats.

CONCLUSION

ERK/MSCs transplantation showed better functional recovery after stroke in rats, likely in part through enhancing survival of MSCs and possibly by modulating the proliferation, neuronal de-differentiation and neuroinflammation.

Two faces of the coin: Minireview for dissecting the role of reactive oxygen species in stem cell potency and lineage commitment

Reactive oxygen species (ROS) are produced as by-products of several intracellular metabolic pathways and are reduced to more stable molecules by several protective pathways. The presence of high levels of ROS can be associated with disturbance of cell function and could lead to apoptosis. The presence of ROS within the physiological range has many effects on several signalling pathways. In stem cells, this role can range between keeping the potency of the naive stem cells to differentiation towards a certain lineage. In addition, the level of certain ROS would change according to the differentiation stage. For example, the presence of ROS can be associated with increasing the proliferation of mesenchymal stem cells, decreasing the potency of embryonic stem cells and adding to the genomic stability of induced pluripotent stem cells. ROS can enhance the differentiation of stem cells into cardiomyocytes, adipocytes, endothelial cells, keratinocytes and neurons. In the meantime, ROS inhibits osteogenesis and enhances the differentiation of cartilage to the hypertrophic stage, which is associated with chondrocyte death. Thus, ROS may form a link between naïve stem cells in the body and the environment. In addition, monitoring of ROS levels in vitro may help in tissue regeneration studies.

Comparison of village dog and wolf genomes highlights the role of the neural crest in dog domestication

BACKGROUND

Domesticated from gray wolves between 10 and 40 kya in Eurasia, dogs display a vast array of phenotypes that differ from their ancestors, yet mirror other domesticated animal species, a phenomenon known as the domestication syndrome. Here, we use signatures persisting in dog genomes to identify genes and pathways possibly altered by the selective pressures of domestication.

RESULTS

Whole-genome SNP analyses of 43 globally distributed village dogs and 10 wolves differentiated signatures resulting from domestication rather than breed formation. We identified 246 candidate domestication regions containing 10.8 Mb of genome sequence and 429 genes. The regions share haplotypes with ancient dogs, suggesting that the detected signals are not the result of recent selection. Gene enrichments highlight numerous genes linked to neural crest and central nervous system development as well as neurological function. Read depth analysis suggests that copy number variation played a minor role in dog domestication.

CONCLUSIONS

Our results identify genes that act early in embryogenesis and can confer phenotypes distinguishing domesticated dogs from wolves, such as tameness, smaller jaws, floppy ears, and diminished craniofacial development as the targets of selection during domestication. These differences reflect the phenotypes of the domestication syndrome, which can be explained by alterations in the migration or activity of neural crest cells during development. We propose that initial selection during early dog domestication was for behavior, a trait influenced by genes which act in the neural crest, which secondarily gave rise to the phenotypes of modern dogs.

Human peptidergic nociceptive sensory neurons generated from human epidermal neural crest stem cells (hEPI-NCSC)

Here we provide new technology for generating human peptidergic nociceptive sensory neurons in a straightforward and efficient way. The cellular source, human epidermal neural crest stem cells (hEPI-NCSC), consists of multipotent somatic stem cells that reside in the bulge of hair follicles. hEPI-NCSC and primary sensory neurons have a common origin, the embryonic neural crest. For directed differentiation, hEPI-NCSC were exposed to pertinent growth factors and small molecules in order to modulate master signalling networks involved in differentiation of neural crest cells into postmitotic peptidergic sensory neurons during embryonic development. The neuronal populations were homogenous in regard to antibody marker expression. Cells were immunoreactive for essential master regulatory genes, including NGN1/2, SOX10, and BRN3a among others, and for the pain-mediating genes substance P (SP), calcitonin gene related protein (CGRP) and the TRPV1 channel. Approximately 30% of total cells responded to capsaicin, indicating that they expressed an active TRPV1 channel. In summary, hEPI-NCSC are a biologically relevant and easily available source of somatic stem cells for generating human peptidergic nociceptive neurons without the need for genetic manipulation and cell purification. As no analgesics exist that specifically target TRPV1, a ready supply of high-quality human peptidergic nociceptive sensory neurons could open the way for new approaches, in a biologically relevant cellular context, to drug discovery and patient-specific disease modelling that is aimed at pain control, and as such is highly desirable.

Differentiation of circulating neural progenitor cells in vitro on fibrin-based composite -matrix involves Wnt- β-catenin-like signaling

Isolation of progenitors with regenerative potential and their in vitro induction to specific lineage may be necessary for effective cell transplantation outcome. Earlier, we standardized specific niche for derivation of neural progenitor cells (NPCs) from circulating mononuclear cells to neural like cells (NLC) in vitro, for applications in neural regeneration. The current study analysed the prospective involvement of signaling mechanism for in vitro lineage commitment of circulating NPCs. Preferred mechanism selected was Wnt-like signaling because this is one of the pathways implicated in the central nervous system (CNS) development and homeostasis. We sought to determine the activation of Wnt3a-specific genes in the standardized NPC culture system. To start with, it was found that when standardized NPC culture niche was supplemented with Wnt 3a protein, no additional morphological changes happen. Chemical inhibitors of the pathway retarded NPC to NLC conversion both in the absence and presence of supplemented Wnt-3a. In earlier studies, involvement of the niche constituents- fibronectin (FN), laminin (La) and fibrin (Fib)- for NPC growth and differentiation was established. In an attempt to study the role of these adhesive proteins by adding antibodies against FN, La & Fib together, molecular level signaling changes seen were comparable to that occur in response to Wnt3a chemical inhibitor. Therefore, induction of Wnt 3a-like signal from the matrix-dependent niche constituents may be implicated in the differentiation of NPC to NLC. The results substantiate the potential applications of the fibrin-based composite niche in neural engineering for regeneration.

Creating a stem cell niche in the inner ear using self-assembling peptide amphiphiles

The use of human embryonic stem cells (hESCs) for regeneration of the spiral ganglion will require techniques for promoting otic neuronal progenitor (ONP) differentiation, anchoring of cells to anatomically appropriate and specific niches, and long-term cell survival after transplantation. In this study, we used self-assembling peptide amphiphile (PA) molecules that display an IKVAV epitope (IKVAV-PA) to create a niche for hESC-derived ONPs that supported neuronal differentiation and survival both in vitro and in vivo after transplantation into rodent inner ears. A feature of the IKVAV-PA gel is its ability to form organized nanofibers that promote directed neurite growth. Culture of hESC-derived ONPs in IKVAV-PA gels did not alter cell proliferation or viability. However, the presence of IKVAV-PA gels increased the number of cells expressing the neuronal marker beta-III tubulin and improved neurite extension. The self-assembly properties of the IKVAV-PA gel allowed it to be injected as a liquid into the inner ear to create a biophysical niche for transplanted cells after gelation in vivo. Injection of ONPs combined with IKVAV-PA into the modiolus of X-SCID rats increased survival and localization of the cells around the injection site compared to controls. Human cadaveric temporal bone studies demonstrated the technical feasibility of a transmastoid surgical approach for clinical intracochlear injection of the IKVAV-PA/ONP combination. Combining stem cell transplantation with injection of self-assembling PA gels to create a supportive niche may improve clinical approaches to spiral ganglion regeneration.

Generation of Otic Sensory Neurons from Mouse Embryonic Stem Cells in 3D Culture

The peripheral hearing process taking place in the cochlea mainly depends on two distinct sensory cell types: the mechanosensitive hair cells and the spiral ganglion neurons (SGNs). The first respond to the mechanical stimulation exerted by sound pressure waves on their hair bundles by releasing neurotransmitters and thereby activating the latter. Loss of these sensorineural cells is associated with permanent hearing loss. Stem cell-based approaches aiming at cell replacement or in vitro drug testing to identify potential ototoxic, otoprotective, or regenerative compounds have lately gained attention as putative therapeutic strategies for hearing loss. Nevertheless, they rely on efficient and reliable protocols for the in vitro generation of cochlear sensory cells for their implementation. To this end, we have developed a differentiation protocol based on organoid culture systems, which mimics the most important steps of in vivo otic development, robustly guiding mouse embryonic stem cells (mESCs) toward otic sensory neurons (OSNs). The stepwise differentiation of mESCs toward ectoderm was initiated using a quick aggregation method in presence of Matrigel in serum-free conditions. Non-neural ectoderm was induced via activation of bone morphogenetic protein (BMP) signaling and concomitant inhibition of transforming growth factor beta (TGFβ) signaling to prevent mesendoderm induction. Preplacodal and otic placode ectoderm was further induced by inhibition of BMP signaling and addition of fibroblast growth factor 2 (FGF2). Delamination and differentiation of SGNs was initiated by plating of the organoids on a 2D Matrigel-coated substrate. Supplementation with brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) was used for further maturation until 15 days of in vitro differentiation. A large population of neurons with a clear bipolar morphology and functional excitability was derived from these cultures. Immunostaining and gene expression analysis performed at different time points confirmed the transition trough the otic lineage and final expression of the key OSN markers. Moreover, the stem cell-derived OSNs exhibited functional electrophysiological properties of native SGNs. Our established in vitro model of OSNs development can be used for basic developmental studies, for drug screening or for the exploration of their regenerative potential.

Inter-individual variation in genes governing human hippocampal progenitor differentiation in vitro is associated with hippocampal volume in adulthood

Hippocampal volumes are smaller in psychiatric disorder patients and lower levels of hippocampal neurogenesis are the hypothesized cause. Understanding which molecular processes regulate hippocampal progenitor differentiation might aid in the identification of novel drug targets that can promote larger hippocampal volumes. Here we use a unique human cell line to assay genome-wide expression changes when hippocampal progenitor cells differentiate. RNA was extracted from proliferating cells versus differentiated neural cells and applied to Illumina Human HT-12 v4 Expression BeadChips. Linear regressions were used to determine the effect of differentiation on probe expression and we assessed enrichment for gene ontology (GO) terms. Genetic pathway analysis (MAGMA) was used to evaluate the relationship between hippocampal progenitor cell differentiation and adult hippocampal volume, using results from the imaging genomics consortium, ENIGMA. Downregulated transcripts were enriched for mitotic processes and upregulated transcripts were enriched for cell differentiation. Upregulated (differentiation) transcripts specifically, were also predictive of adult hippocampal volume; with Early growth response protein 2 identified as a hub transcription factor within the top GO term, and a potential drug target. Our results suggest that genes governing differentiation, rather than mitosis, have an impact on adult hippocampal volume and that these genes represent important drug targets.

M2 microglia promotes neurogenesis and oligodendrogenesis from neural stem/progenitor cells via the PPARγ signaling pathway

Neural stem/progenitor cells (NSPCs) are an important source of cells for cell replacement therapy after nerve injury. How to induce NSPCs differentiation towards neurons and oligodendrocytes is a challenging issue in neuroscience research. In the present study, we polarized microglia into M1 and M2 phenotype, used their supernatants to induce NSPCs differentiation, and investigated the effects of different microglia phenotypes on NSPCs differentiation and their mechanisms. We discovered that, after exposure to M1 phenotype supernatant, NSPCs differentiated into fewer Tuj-1+ and Olig2+ cells, but more GFAP+ cells. Meanwhile, a significantly increased number of Tuj-1+ and Olig2+ cells and smaller number of GFAP+ cells were generated by M2 microglia supernatant-induced NSPCs differentiation. We also observed that 15d-PGJ₂, an endogenous ligand of PPARγ, was elevated in M2 phenotype supernatant and could activate PPARγ expression in NSPCs, whereas use of the PPARγ inhibitor GW9662, could reduce the percentage of differentiated neurons and oligodendrocytes. Our study results confirm that M2 microglia supernatant can activate the PPARγ signaling pathway and promote neurogenesis and oligodendrogenesis from NSPCs differentiation. The present study provides a further theoretical basis for induction of NSPCs oriented differentiation.

The high mobility group AT-hook 1 protein stimulates bovine herpesvirus 1 productive infection

Bovine herpesvirus 1 (BoHV-1) is an important pathogen of cattle that causes clinical symptoms in the upper respiratory tract and conjunctivitis. Like most alpha-herpesvirinae subfamily members, BoHV-1 establishes latency in sensory neurons. Stress consistently induces reactivation from latency, which is essential for virus transmission. Recent studies demonstrated that a viral protein (ORF2) expressed in a subset of latently infected neurons is associated with β-catenin and the high mobility group AT-hook 1 protein (HMGA1), which correlates with increased expression of these proteins in latently infected neurons. Since HMGA1 is primarily expressed in actively growing cells, binds to the minor groove of A+T rich regions in double-stranded DNA, and mediates gene transcription, we hypothesized that HMGA1 regulates BoHV-1 productive infection. Studies in this report indicated that productive infection increased HMGA1 protein levels and re-localized the protein in the nucleus. Netropsin, a small molecule that binds to the minor groove of DNA and prevents HMGA1 from interacting with DNA inhibited viral replication and interfered with the ability of BoHV-1 to induce HMGA1 re-localization. Furthermore, netropsin reduced RNA and protein expression of two viral regulatory proteins (bICP0 and bICP22) during productive infection, but increased bICP4 levels. Small interfering RNAs (siRNAs) that specifically target HMGA1 reduced HMGA1 RNA levels and virus production confirming HMGA1 stimulates productive infection.

The effect of histone deacetylase inhibitor trichostatin A on porcine mesenchymal stem cell transcriptome

The use of histone deacetylase inhibitors such as trichostatin A (TSA) for epigenetic transformation of mesenchymal stem cells (MSCs), whose nuclei will be transferred into enucleated oocytes, is a novel approach in research involving somatic cell cloning of pigs and other mammalian species. Although the effectiveness of TSA in cloning applications was confirmed, processes and mechanisms underlying achieved effects are not yet fully understood, especially for pig MSCs. To contribute to this knowledge, in this study we performed a comprehensive transcriptome analysis using high-throughput sequencing of pig bone-marrow derived MSCs, both treated and untreated with TSA, and evaluated the effect of TSA administration on their transcription profile after 24 h of in vitro culture. The expression of selected positive and negative mesenchymal surface antigens was also evaluated in these cells by flow cytometry. Subsequently, the stability of induced expression changes was evaluated after another 55-72 h of culture without TSA. The results of this study showed that TSA does not affect the expression of the selected surface antigens related to MSC mesenchymal stemness origin, namely: CD90 (positive marker), CD31 and CD34 (negative markers) and has a wide stimulating effect on MSCs transcription, affecting genes across the whole genome with some minor signs of site-specific acting in regions on SSC2 and SSC6. TSA turned out to have a higher impact on already expressed genes with only minor abilities to induce expression of silenced genes. Genes with expression affected by TSA were related to a wide range of biological processes, however, we found some evidence for specific stimulation of genes associated with development, differentiation, neurogenesis or myogenesis. TSA also seemed to interfere with Wnt signaling pathways by upregulation of several engaged genes. The analysis of cell transcriptome after prolonged culture following the TSA removal, showed that the expression level of majority of genes affected by TSA is restored to the initial level. Nonetheless, the set of about six hundred genes responsible for e.g. adhesion, signal transduction and cell communication was altered even after 55-72 h of culture without TSA. TSA also enhanced expression of some of pluripotency marker genes (FGF2, LIF, TERT) but their expression was stabilized during further culture without TSA. The detailed analysis of factors connected with neuron-like differentiation allowed us to assume that TSA mostly stimulates neurogenic differentiation pathway in the pig MSCs possibly through interaction with Wnt-mediated signaling and thus triggers mechanisms conducive to epigenetic reprograming.

Advances in translational inner ear stem cell research

Stem cell research is expanding our understanding of developmental biology as well as promising the development of new therapies for a range of different diseases. Within hearing research, the use of stem cells has focused mainly on cell replacement. Stem cells however have a broad range of other potential applications that are just beginning to be explored in the ear. Mesenchymal stem cells are an adult derived stem cell population that have been shown to produce growth factors, modulate the immune system and can differentiate into a wide variety of tissue types. Potential advantages of mesenchymal/adult stem cells are that they have no ethical constraints on their use. However, appropriate regulatory oversight seems necessary in order to protect patients from side effects. Disadvantages may be the lack of efficacy in many preclinical studies. But if proven safe and efficacious, they are easily translatable to clinical trials. The current review will focus on the potential application on mesenchymal stem cells for the treatment of inner ear disorders.

Isolation and Characterization of Human Chorionic Membranes Mesenchymal Stem Cells and Their Neural Differentiation

Mesenchymal stem cells (MSCs) can be obtained from a variety of human tissues. Placenta has become an attractive stem cell source for potential applications in regenerative medicine and tissue engineering. The aim of this study was to localize and characterize MSCs within human chorionic membranes (hCMSCs). For this purpose, immunofluorescence labeling with CD105 and CD90 were used to determine the distribution of MSCs in chorionic membranes tissue. A medium supplemented with a synthetic serum and various concentrations of neurotrophic factors and cytokines was used to induce hCMSCs to neural cells. The results showed that the CD90 positive cells were scattered in the chorionic membranes tissue, and the CD105 positive cells were mostly located around the small blood vessels. hCMSCs expressed typical mesenchymal markers (CD73, CD90, CD105, CD44 and CD166) but not hematopoietic markers (CD45, CD34) and HLA-DR. hCMSCs differentiated into adipocytes, osteocytes, chondrocytes, and neuronal cells, as revealed by morphological changes, cell staining, immunofluorescence analyses, and RT-PCR showing the tissue-specific gene presence for differentiated cell lineages after the treatment with induce medium. Human chorionic membranes may be the source of MSCs for treatment of nervous system injury.

Directed Differentiation of Human Embryonic Stem Cells Toward Placode-Derived Spiral Ganglion-Like Sensory Neurons

The ability to generate spiral ganglion neurons (SGNs) from stem cells is a necessary prerequisite for development of cell-replacement therapies for sensorineural hearing loss. We present a protocol that directs human embryonic stem cells (hESCs) toward a purified population of otic neuronal progenitors (ONPs) and SGN-like cells. Between 82% and 95% of these cells express SGN molecular markers, they preferentially extend neurites to the cochlear nucleus rather than nonauditory nuclei, and they generate action potentials. The protocol follows an in vitro stepwise recapitulation of developmental events inherent to normal differentiation of hESCs into SGNs, resulting in efficient sequential generation of nonneuronal ectoderm, preplacodal ectoderm, early prosensory ONPs, late ONPs, and cells with cellular and molecular characteristics of human SGNs. We thus describe the sequential signaling pathways that generate the early and later lineage species in the human SGN lineage, thereby better describing key developmental processes. The results indicate that our protocol generates cells that closely replicate the phenotypic characteristics of human SGNs, advancing the process of guiding hESCs to states serving inner-ear cell-replacement therapies and possible next-generation hybrid auditory prostheses. © Stem Cells Translational Medicine 2017;6:923-936.

External factors influencing mesenchymal stem cell fate in vitro

Mesenchymal stem cells (MSCs) have extensive potentials, which make them attractive candidates for the developmental biology, drug discovery and regenerative medicine. However, the use of MSCs is limited by their scarceness in tissues and in culture conditions. They also exhibit various degrees of potency which subsequently influencing their applications. Nowadays, questions remain about how self-renewal and differentiation of MSCs can be controlled in vitro and in vivo, how they will behave and migrate to the right place and how they modulate the immune system. Therefore, identification of factors and culture conditions to affect the fate and function of MSCs may be effective to enhance their applications in clinical situations. Studies have indicated that the fate of MSCs in culture is influenced by various external factors, including the specific cell source, donor age, plating density, passage number and plastic surface quality. Some other factors such as cell culture media and their supplementary factors, O₂ concentration, mechano-/electro-stimuli and three-dimensional scaffolds are also shown to be influential. This review addresses the current state of MSC research for describing and discussing the findings about external factors that influence the fate and function of MSCs. Additionally, the new discoveries and suggestions regarding their molecular mechanisms will be explained.

Regulation of Tlx3 by Pax6 is required for the restricted expression of Chrnα3 in Cerebellar Granule Neuron progenitors during development

Homeobox gene Tlx3 is known to promote glutamatergic differentiation and is expressed in post-mitotic neurons of CNS. Contrary to this here, we discovered that Tlx3 is expressed in the proliferating progenitors of the external granule layer in the cerebellum, and examined factors that regulate this expression. Using Pax6^−/−Sey mouse model and molecular interaction studies we demonstrate Pax6 is a key activator of Tlx3 specifically in cerebellum, and induces its expression starting at embryonic day (E)15. By Postnatal day (PN)7, Tlx3 is expressed in a highly restricted manner in the cerebellar granule neurons of the posterior cerebellar lobes, where it is required for the restricted expression of nicotinic cholinergic receptor-α3 subunit (Chrnα3) and other genes involved in formation of synaptic connections and neuronal migration. These results demonstrate a novel role for Tlx3 and indicate that Pax6-Tlx3 expression and interaction is part of a region specific regulatory network in cerebellum and its deregulation during development could possibly lead to Autistic spectral disorders (ASD).

Induction of neuronal-like phenotype in human mesenchymal stem cells by overexpression of Neurogenin1 and treatment with neurotrophins

AIM OF THE STUDY

The induced expression of the transcription factors neurogenin1 (Neurog1) or neuronal differentiation 1 (NeuroD1) has previously been shown to initiate neuronal differentiation in embryonic stem cells (ESC). Human bone marrow-derived mesenchymal stem cells (hBMSCs) are ethically non-controversial stem cells. However, they are not pluripotent. In cochlear implantation, regeneration or replacement of lost spiral ganglion neurons may be a measure for the improvement of implant function. Thus, the aim of the study was to investigate whether the expression of Neurog1 or NeuroD1 is sufficient for induction of neuronal differentiation in hBMSCs.

MATERIALS AND METHODS

Human BMSCs were transduced with lentivirus expressing NeuroD1 or Neuorg1. Transduced cells were then treated with small molecules that enhanced neuronal differentiation. Markers of neuronal differentiation were evaluated.

RESULTS

Using quantitative reverse transcription PCR, the up-regulation of transcription factors expressed by developing primary auditory neurons, such as BRN3a (POU4F1) and GATA3, was quantified after induction of Neurog-1 expression. In addition, the expression of the receptor NTRK2 was induced by treatment with its specific ligand BDNF. The induction of expression of the vesicular glutamate transporter 1 was identified on gene and protein level. NeuroD1 seemed not sufficient to induce and maintain neuronal differentiation.

CONCLUSIONS

Induction of neuronal differentiation by overexpression of Neurog1 initiated important steps for the development of glutamatergic neurons such as the spiral ganglion neurons. However, it seems not sufficient to maintain the glutamatergic spiral ganglion neuron-like phenotype.

Toxoplasma gondii inhibits differentiation of C17.2 neural stem cells through Wnt/β-catenin signaling pathway

Toxoplasma gondii is a major cause of congenital brain disease. T. gondii infection in the developing fetus frequently results in major neural developmental damage; however, the effects of the parasite infection on the neural stem cells, the key players in fetal brain development, still remain elusive. This study is aiming to explore the role of T. gondii infection on differentiation of neural stem cells (NSCs) and elucidate the underlying molecular mechanisms that regulate the inhibited differentiation of NSCs induced by the infection. Using a differentiation medium, i.e. , DMEM: F12 (1:1 mixture) supplemented with 2% N2, C17.2 neural stem cells (NSCs) were able to differentiate to neurons and astrocytes, respectively evidenced by immunofluorescence staining of differentiation markers including βIII-tubulin and glial fibrillary acidic protein (GFAP). After 5-day culture in the differentiation medium, the excreted-secreted antigens of T. gondii (Tg-ESAs) significantly down-regulated the protein levels of βIII-tubulin and GFAP in C17.2 NSCs in a dose-dependent manner. The protein level of β-catenin in the nucleus of C17.2 cells treated with both wnt3a (a key activator for Wnt/β-catenin signaling pathway) and Tg-ESAs was significantly lower than that in the cells treated with only wnt3a, but significantly higher than that in the cells treated with only Tg-ESAs. In conclusion, the ESAs of T. gondii RH blocked the differentiation of C17.2 NCSs and downregulated the expression of β-catenin, an essential component of Wnt/β-catenin signaling pathway. The findings suggest a new mechanism underlying the neuropathogenesis induced by T. gondii infection, i.e. inhibition of the differentiation of NSCs via blockade of Wnt/β-catenin signaling pathway, such as downregulation of β-catenin expression by the parasite ESAs.

β-Catenin, a Transcription Factor Activated by Canonical Wnt Signaling, Is Expressed in Sensory Neurons of Calves Latently Infected with Bovine Herpesvirus 1

Like many Alphaherpesvirinae subfamily members, bovine herpesvirus 1 (BoHV-1) expresses an abundant transcript in latently infected sensory neurons, the latency-related (LR)-RNA. LR-RNA encodes a protein (ORF2) that inhibits apoptosis, interacts with Notch family members, interferes with Notch-mediated transcription, and stimulates neurite formation in cells expressing Notch. An LR mutant virus containing stop codons at the amino terminus of ORF2 does not reactivate from latency or replicate efficiently in certain tissues, indicating that LR gene products are important. In this study, β-catenin, a transcription factor activated by the canonical Wnt signaling pathway, was frequently detected in ORF2-positive trigeminal ganglionic neurons of latently infected, but not mock-infected, calves. Conversely, the lytic cycle regulatory protein (BoHV-1 infected cell protein 0, or bICP0) was not frequently detected in β-catenin-positive neurons in latently infected calves. During dexamethasone-induced reactivation from latency, mRNA expression levels of two Wnt antagonists, Dickkopf-1 (DKK-1) and secreted Frizzled-related protein 2 (SFRP2), were induced in bovine trigeminal ganglia (TG), which correlated with reduced β-catenin protein expression in TG neurons 6 h after dexamethasone treatment. ORF2 and a coactivator of β-catenin, mastermind-like protein 1 (MAML1), stabilized β-catenin protein levels and stimulated β-catenin-dependent transcription in mouse neuroblastoma cells more effectively than MAML1 or ORF2 alone. Neuroblastoma cells expressing ORF2, MAML1, and β-catenin were highly resistant to cell death following serum withdrawal, whereas most cells transfected with only one of these genes died. The Wnt signaling pathway interferes with neurodegeneration but promotes neuronal differentiation, suggesting that stabilization of β-catenin expression by ORF2 promotes neuronal survival and differentiation.

IMPORTANCE

Bovine herpesvirus 1 (BoHV-1) is an important pathogen of cattle, and like many Alphaherpesvirinae subfamily members establishes latency in sensory neurons. Lifelong latency and the ability to reactivate from latency are crucial for virus transmission. Maintaining the survival and normal functions of terminally differentiated neurons is also crucial for lifelong latency. Our studies revealed that BoHV-1 gene products expressed during latency stabilize expression of the transcription factor β-catenin and perhaps its cofactor, mastermind-like protein 1 (MAML1). In contrast to expression during latency, β-catenin expression in sensory neurons is not detectable following treatment of latently infected calves with the synthetic corticosteroid dexamethasone to initiate reactivation from latency. A viral protein (ORF2) expressed in a subset of latently infected neurons stabilized β-catenin and MAML1 in transfected cells. ORF2, β-catenin, and MAML1 also enhanced cell survival when growth factors were withdrawn, suggesting that these genes enhance survival of latently infected neurons.

A lower volume culture method for obtaining a larger yield of neuron-like cells from mesenchymal stem cells

Mesenchymal stem cells (MSCs) represent a promising cell source for stem cell therapy to replace neurons damaged by neurodegenerative diseases. A system designed for in vitro neuronal differentiation of MSCs is an indispensable technique, which provides MSC-derived functional neurons for cell-replacement therapies and valuable information in pre-clinical research. This study investigated the effects of reducing the volume of neural induction medium on cell viability and neural differentiation of MSCs. When MSCs were differentiated in low volumes of neural induction medium, rather than using the conventional method, the cell density on culture dishes significantly increased. The % cell death, including apoptosis and necrosis, was significantly lower in the lower volume method than in the conventional method. There were no significant differences between the lower volume and conventional methods in the expression levels of the neuronal marker genes. In an analysis of immunostaining for a mature neuronal marker, no significant difference was detected between the media volumes. These findings demonstrate that neuronal induction of MSCs in low volumes of differentiation medium promoted survival during differentiation and resulted in larger numbers of MSC-derived neurons, compared to the conventional method. This novel lower volume method offers both financial and cell-yield advantages over the conventional method.