The role of nuclear receptors in controlling the fine balance between proliferation and differentiation of neural stem cells

PPAR Gamma and Viral Infections of the Brain

Peroxisome Proliferator-Activated Receptor gamma (PPARγ) is a master regulator of metabolism, adipogenesis, inflammation and cell cycle, and it has been extensively studied in the brain in relation to inflammation or neurodegeneration. Little is known however about its role in viral infections of the brain parenchyma, although they represent the most frequent cause of encephalitis and are a major threat for the developing brain. Specific to viral infections is the ability to subvert signaling pathways of the host cell to ensure virus replication and spreading, as deleterious as the consequences may be for the host. In this respect, the pleiotropic role of PPARγ makes it a critical target of infection. This review aims to provide an update on the role of PPARγ in viral infections of the brain. Recent studies have highlighted the involvement of PPARγ in brain or neural cells infected by immunodeficiency virus 1, Zika virus, or human cytomegalovirus. They have provided a better understanding on PPARγ functions in the infected brain, and revealed that it can be a double-edged sword with respect to inflammation, viral replication, or neuronogenesis. They unraveled new roles of PPARγ in health and disease and could possibly help designing new therapeutic strategies.

Neural Stem Cells: What Happens When They Go Viral?

Viruses that infect the central nervous system (CNS) are associated with developmental abnormalities as well as neuropsychiatric and degenerative conditions. Many of these viruses such as Zika virus (ZIKV), cytomegalovirus (CMV), and herpes simplex virus (HSV) demonstrate tropism for neural stem cells (NSCs). NSCs are the multipotent progenitor cells of the brain that have the ability to form neurons, astrocytes, and oligodendrocytes. Viral infections often alter the function of NSCs, with profound impacts on the growth and repair of the brain. There are a wide spectrum of effects on NSCs, which differ by the type of virus, the model system, the cell types studied, and the age of the host. Thus, it is a challenge to predict and define the consequences of interactions between viruses and NSCs. The purpose of this review is to dissect the mechanisms by which viruses can affect survival, proliferation, and differentiation of NSCs. This review also sheds light on the contribution of key antiviral cytokines in the impairment of NSC activity during a viral infection, revealing a complex interplay between NSCs, viruses, and the immune system.

Accommodation-based interventions for individuals experiencing, or at risk of experiencing, homelessness

Background

Globally, almost 1.6 billion individuals lack adequate housing. Many accommodation-based approaches have evolved across the globe to incorporate additional support and services beyond delivery of housing.

Objectives

This review examines the effectiveness of accommodation-based approaches on outcomes including housing stability, health, employment, crime, wellbeing, and cost for individuals experiencing or at risk of experiencing homelessness.

Search Methods

The systematic review is based on evidence already identified in two existing EGMs commissioned by the Centre for Homelessness Impact (CHI) and built by White et al. The maps were constructed using a comprehensive three stage search and mapping process. Stage one mapped included studies in an existing systematic review on homelessness, stage two was an extensive search of 17 academic databases, three EGM databases, and eight systematic review databases. Finally stage three included web searches for grey literature, scanning reference lists of included studies and consultation with experts to identify additional literature. We identified 223 unique studies across 551 articles from the effectiveness map on 12th April 2019.

Selection Criteria

We include research on all individuals currently experiencing, or at risk of experiencing homelessness irrespective of age or gender, in high-income countries. The Network Meta-Analysis (NMA) contains all study designs where a comparison group was used. This includes randomised controlled trials (RCTs), quasi-experimental designs, matched comparisons and other study designs that attempt to isolate the impact of the intervention on homelessness. The NMA primarily addresses how interventions can reduce homelessness and increase housing stability for those individuals experiencing, or at risk of experiencing, homelessness. Additional outcomes are examined and narratively described. These include: access to mainstream healthcare; crime and justice; employment and income; capabilities and wellbeing; and cost of intervention. These outcomes reflect the domains used in the EGM, with the addition of cost.

Data Collection and Analysis

Due to the diverse nature of the literature on accommodation-based approaches, the way in which the approaches are implemented in practice, and the disordered descriptions of the categories, the review team created a novel typology to allow meaningful categorisations for functional and useful comparison between the various intervention types. Once these eligible categories were identified, we undertook dual data extraction, where two authors completed data extraction and risk of bias (ROB) assessments independently for each study. NMA was conducted across outcomes related to housing stability and health.Qualitative data from process evaluations is included using a "Best Fit" Framework synthesis. The purpose of this synthesis is to complement the quantitative evidence and provide a better understanding of what factors influenced programme effectiveness. All included Qualitative data followed the initial framework provided by the five main analytical categories of factors of influence (reflected in the EGM), namely: contextual factors, policy makers/funders, programme administrators/managers/implementing agencies, staff/case workers and recipients of the programme.

Main Results

There was a total of 13,128 people included in the review, across 51 reports of 28 studies. Most of the included studies were carried out in the United States of America (25/28), with other locations including Canada and the UK. Sixteen studies were RCTs (57%) and 12 were nonrandomised (quasi-experimental) designs (43%). Assessment of methodological quality and potential for bias was conducted using the second version of the Cochrane Risk of Bias tool for Randomised controlled trials. Nonrandomised studies were coded using the ROBINS- I tool. Out of the 28 studies, three had sufficiently low ROB (11%), 11 (39%) had moderate ROB, and five (18%) presented serious problems with ROB, and nine (32%) demonstrated high, critical problems with their methodology. A NMA on housing stability outcomes demonstrates that interventions offering the highest levels of support alongside unconditional accommodation (High/Unconditional) were more effective in improving housing stability compared to basic support alongside unconditional housing (Basic/Unconditional) (ES=1.10, 95% confidence interval [CI] [0.39, 1.82]), and in comparison to a no-intervention control group (ES=0.62, 95% CI [0.19, 1.06]). A second NMA on health outcomes demonstrates that interventions categorised as offering Moderate/Conditional (ES= 0.36, 95% CI [0.03, 0.69]) and High/Unconditional (ES = 0.22, 95% CI [0.01, 0.43]) support were effective in improving health outcomes compared to no intervention. These effects were smaller than those observed for housing stability. The quality of the evidence was relatively low but varied across the 28 included studies. Depending on the context, finding accommodation for those who need it can be hindered by supply and affordability in the market. The social welfare approach in each jurisdiction can impact heavily on support available and can influence some of the prejudice and stigma surrounding homelessness. The evaluations emphasised the need for collaboration and a shared commitment between policymakers, funders and practitioners which creates community and buy in across sectors and agencies. However, co-ordinating this is difficult and requires sustainability to work. For those implementing programmes, it was important to invest time in developing a culture together to build trust and solid relationships. Additionally, identifying sufficient resources and appropriate referral routes allows for better implementation planning. Involving staff and case workers in creating processes helps drive enthusiasm and energy for the service. Time should be allocated for staff to develop key skills and communicate engage effectively with service users. Finally, staff need time to develop trust and relationships with service users; this goes hand in hand with providing information that is up to date and useful as well making themselves accessible in terms of location and time.

Authors' Conclusions

The network meta-analysis suggests that all types of accommodation which provided support are more effective than no intervention or Basic/Unconditional accommodation in terms of housing stability and health. The qualitative evidence synthesis raised a primary issue in relation to context: which was the lack of stable, affordable accommodation and the variability in the rental market, such that actually sourcing accommodation to provide for individuals who are homeless is extremely challenging. Collaboration between stakeholders and practitioners can be fruitful but difficult to coordinate across different agencies and organisations.

Type II nuclear receptors with potential role in Alzheimer disease

Nuclear receptors are ligand-activated transcription factors that can modulated cellular processes involved in the development, homeostasis, cell proliferation, metabolism, and reproduction through the control of the specific genetic and molecular program. In the central nervous system, they are key regulators of neural stem cell fate decisions and can modulate the physiology of different brain cells. Over the past decades, a large body of evidence has supported that nuclear receptors are potential therapeutic targets for the treatment of neurodegenerative disorders such as Alzheimer's disease, the most common dementia worldwide, and the main cause of disability in later life. This disease is characterized by the progressive accumulation of amyloid-beta peptides and hyperphosphorylated tau protein that can explain alterations in synaptic transmission and plasticity; loss of dendritic spines; increased in reactive microglia and inflammation; reduction of neuronal stem cells number; myelin and vascular alterations that finally leads to increased neuronal death. Here, we present a review of type II no steroidal nuclear receptors that form obligatory heterodimers with the Retinoid X Receptor (RXR) and its potential in the therapeutic of AD. Activation of type II nuclear receptor by synthetic agonist leads to transcriptional regulation of specific genes that acts counteracting against the detrimental effects of amyloid-beta peptides and hyperphosphorylated tau in neuronal cells recovering the functionality of the synapses. But also, activation of type II nuclear receptor leads to modifications in APP metabolism, repression of inflammatory cascade and inductors of the generation of neuronal stem cells and progenitor cells supporting its potential therapeutics role for Alzheimer's disease.

[Research progress of structured repair of tendon-bone interface]

In sports system, the tendon-bone interface has the effect of tensile and bearing load, so the effect of healing plays a crucial role in restoring joint function. The process of repair is the formation of scar tissue, so it is difficult to achieve the ideal effect for morphology and biomechanical strength. The tissue engineering method can promote the tendon-bone interface healing from the seed cells, growth factors, and scaffolds, and is a new direction in the field of development of the tendon-bone interface healing.

Antiproliferative Effect of Elastin-Derived Peptide VGVAPG on SH-SY5Y Neuroblastoma Cells

Throughout the lifetime of humans, the amount of stem cells and the rate of cell proliferation continue to decrease. Reactive oxygen species (ROS) are one among the many factors that promote stem cell aging. Both a decrease in the level of stem cells and increase in ROS production can lead to the development of different neurodegenerative diseases. This study was conducted to determine how the VGVAPG peptide, liberated from elastin during the aging process and under pathological conditions, affects ROS production and activities of antioxidant enzymes in undifferentiated, proliferating SH-SY5Y cells. SH-SY5Y cells were maintained in Dulbecco's modified Eagle's medium/nutrient mixture F-12 supplemented with 10% heat-inactivated fetal bovine serum (FBS). After treating the SH-SY5Y cells with VGVAPG peptide, we measured ROS production; cell metabolism, proliferation, and expression; and activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT). We demonstrated that the VGVAPG peptide increases GPx expression and activity, whereas it decreases CAT expression in SH-SY5Y cells. Silencing of the GLB1 gene prevents changes in GPx activity. Despite the fact that the VGVAPG peptide increases GPx expression, it increases the ROS level. Moreover, the VGVAPG peptide decreases SH-SY5Y proliferation, which is prevented by the ROS scavenger N-acetyl-L-cysteine. Our data suggest that ROS production and decreased proliferation of SH-SY5Y cells are the results of excitotoxicity meditated through close unrecognized molecular pathways. More research is needed to elucidate the unknown mechanism of action of VGVAPG peptide in the nervous system.

Oral administration of the cannabigerol derivative VCE-003.2 promotes subventricular zone neurogenesis and protects against mutant huntingtin-induced neurodegeneration

BACKGROUND

The administration of certain cannabinoids provides neuroprotection in models of neurodegenerative diseases by acting through various cellular and molecular mechanisms. Many cannabinoid actions in the nervous system are mediated by CB1 receptors, which can elicit psychotropic effects, but other targets devoid of psychotropic activity, including CB2 and nuclear PPARγ receptors, can also be the target of specific cannabinoids.

METHODS

We investigated the pro-neurogenic potential of the synthetic cannabigerol derivative, VCE-003.2, in striatal neurodegeneration by using adeno-associated viral expression of mutant huntingtin in vivo and mouse embryonic stem cell differentiation in vitro.

RESULTS

Oral administration of VCE-003.2 protected striatal medium spiny neurons from mutant huntingtin-induced damage, attenuated neuroinflammation and improved motor performance. VCE-003.2 bioavailability was characterized and the potential undesired side effects were evaluated by analyzing hepatotoxicity after chronic treatment. VCE-003.2 promoted subventricular zone progenitor mobilization, increased doublecortin-positive migrating neuroblasts towards the injured area, and enhanced effective neurogenesis. Moreover, we demonstrated the proneurogenic activity of VCE-003.2 in embryonic stem cells. VCE-003.2 was able to increase neuroblast formation and striatal-like CTIP2-mediated neurogenesis.

CONCLUSIONS

The cannabigerol derivative VCE-003.2 improves subventricular zone-derived neurogenesis in response to mutant huntingtin-induced neurodegeneration, and is neuroprotective by oral administration.

Characteristics of tendon derived stem cells according to different factors to induce the tendinopathy

Tendon derived stem cells (TDSCs) have been used as a therapeutic agent and as a healing marker. However, there has been no study about the characteristics of TDSCs extracted from tendinopathic tendon tissues. The aim of this study was to find the different characteristics of TDSCs according to the factors to induce the tendinopathy. Five- and fifteen-week old Sprague Dawley rats were used for this study and chemically-induced and injury-induced tendinopathy models were made depending on the age of the animal for different types of tendinopathy. TDSCs from chemically-induced tendinopathy showed markedly low proliferation compared to those from age-matched normal control and injury-induced tendinopathy. In addition, TDSCs from chemically-induced tendinopathy progressed to osteogenesis under an osteogenic differentiation environment more than those from other groups. In contrast, TDSCs from injury-induced tendinopathy showed markedly high proliferation and high expression of type III collagen and α-SMA compared to other groups. Adipogenic potentials in TDSCs from injury-induced tendinopathy were also higher. These different characteristics might be helpful in the development new therapeutic agents for tendon regeneration according to different factors to induce the tendinopathy.

Nuclear receptors in neural stem/progenitor cell homeostasis

In the central nervous system, embryonic and adult neural stem/progenitor cells (NSCs) generate the enormous variety and huge numbers of neuronal and glial cells that provide structural and functional support in the brain and spinal cord. Over the last decades, nuclear receptors and their natural ligands have emerged as critical regulators of NSC homeostasis during embryonic development and adult life. Furthermore, substantial progress has been achieved towards elucidating the molecular mechanisms of nuclear receptors action in proliferative and differentiation capacities of NSCs. Aberrant expression or function of nuclear receptors in NSCs also contributes to the pathogenesis of various nervous system diseases. Here, we review recent advances in our understanding of the regulatory roles of steroid, non-steroid, and orphan nuclear receptors in NSC fate decisions. These studies establish nuclear receptors as key therapeutic targets in brain diseases.

Microarray expression profiling in the denervated hippocampus identifies long noncoding RNAs functionally involved in neurogenesis

BACKGROUND

The denervated hippocampus provides a proper microenvironment for the survival and neuronal differentiation of neural progenitors. While thousands of lncRNAs were identified, only a few lncRNAs that regulate neurogenesis in the hippocampus are reported. The present study aimed to perform microarray expression profiling to identify long noncoding RNAs (lncRNAs) that might participate in the hippocampal neurogenesis, and investigate the potential roles of identified lncRNAs in the hippocampal neurogenesis.

RESULTS

In this study, the profiling suggested that 74 activated and 29 repressed (|log fold-change|>1.5) lncRNAs were differentially expressed between the denervated and the normal hippocampi. Furthermore, differentially expressed lncRNAs associated with neurogenesis were found. According to the tissue-specific expression profiles, and a novel lncRNA (lncRNA2393) was identified as a neural regulator in the hippocampus in this study. The expression of lncRNA2393 was activated in the denervated hippocampus. FISH showed lncRNA2393 specially existed in the subgranular zone of the dentate gyrus in the hippocampus and in the cytoplasm of neural stem cells (NSCs). The knockdown of lncRNA2393 depletes the EdU-positive NSCs. Besides, the increased expression of lncRNA2393 was found to be triggered by the change in the microenvironment.

CONCLUSION

We concluded that expression changes of lncRNAs exists in the microenvironment of denervated hippocampus, of which promotes hippocampal neurogenesis. The identified lncRNA lncRNA2393 expressed in neural stem cells, located in the subgranular zone of the dentate gyrus, which can promote NSCs proliferation in vitro. Therefore, the question is exactly which part of the denervated hippocampus induced the expression of lncRNA2393. Further studies should aim to explore the exact molecular mechanism behind the expression of lncRNA2393 in the hippocampus, to lay the foundation for the clinical application of NSCs in treating diseases of the central nervous system.

Peroxisome proliferator-activated receptor γ (PPARγ) activation: A key determinant of neuropathogeny during congenital infection by cytomegalovirus

Congenital infection by human cytomegalovirus (HCMV) might result in permanent neurological sequelae, including sensorineural deafness, cerebral palsies or devastating neurodevelopmental abnormalities. We recently disclosed that Peroxisome Proliferator-Activated Receptor gamma (PPARγ), a transcription factor of the nuclear receptor superfamily, is a key determinant of HCMV pathogenesis in developing brain. Using neural stem cells from human embryonic stem cells, we showed that HCMV infection strongly increases levels and activity of PPARγ in NSCs. Further in vitro experiments showed that PPARγ activity inhibits the neuronogenic differentiation of NSCs into neurons. Consistently, increased PPARγ expression was found in brain section of fetuses infected by HCMV, but not in uninfected controls. In this commentary, we summarize and discuss our findings and the new insights they provide on the neuropathogenesis of HCMV congenital infection.

VCE-003.2, a novel cannabigerol derivative, enhances neuronal progenitor cell survival and alleviates symptomatology in murine models of Huntington's disease

Cannabinoids have shown to exert neuroprotective actions in animal models by acting at different targets including canonical cannabinoid receptors and PPARγ. We previously showed that VCE-003, a cannabigerol (CBG) quinone derivative, is a novel neuroprotective and anti-inflammatory cannabinoid acting through PPARγ. We have now generated a non-thiophilic VCE-003 derivative named VCE-003.2 that preserves the ability to activate PPARγ and analyzed its neuroprotective activity. This compound exerted a prosurvival action in progenitor cells during neuronal differentiation, which was prevented by a PPARγ antagonist, without affecting neural progenitor cell proliferation. In addition, VCE-003.2 attenuated quinolinic acid (QA)-induced cell death and caspase-3 activation and also reduced mutant huntingtin aggregates in striatal cells. The neuroprotective profile of VCE-003.2 was analyzed using in vivo models of striatal neurodegeneration induced by QA and 3-nitropropionic acid (3NP) administration. VCE-003.2 prevented medium spiny DARPP32⁺ neuronal loss in these Huntington’s-like disease mice models improving motor deficits, reactive astrogliosis and microglial activation. In the 3NP model VCE-003.2 inhibited the upregulation of proinflammatory markers and improved antioxidant defenses in the brain. These data lead us to consider VCE-003.2 to have high potential for the treatment of Huntington’s disease (HD) and other neurodegenerative diseases with neuroinflammatory traits.

Regulation of Nuclear Hormone Receptors by MYCN-Driven miRNAs Impacts Neural Differentiation and Survival in Neuroblastoma Patients

MYCN amplification and MYC signaling are associated with high-risk neuroblastoma with poor prognosis. Treating these tumors remains challenging, although therapeutic approaches stimulating differentiation have generated considerable interest. We have previously shown that the MYCN-regulated miR-17∼92 cluster inhibits neuroblastoma differentiation by repressing estrogen receptor alpha. Here, we demonstrate that this microRNA (miRNA) cluster selectively targets several members of the nuclear hormone receptor (NHR) superfamily, and we present a unique NHR signature associated with the survival of neuroblastoma patients. We found that suppressing glucocorticoid receptor (GR) expression in MYCN-driven patient and mouse tumors was associated with an undifferentiated phenotype and decreased survival. Importantly, MYCN inhibition and subsequent reactivation of GR signaling promotes neural differentiation and reduces tumor burden. Our findings reveal a key role for the miR-17∼92-regulated NHRs in neuroblastoma biology, thereby providing a potential differentiation approach for treating neuroblastoma patients.

Claulansine F promoted the neuronal differentiation of neural stem and progenitor cells through Akt/GSK-3β/β-catenin pathway

The persistence of neurogenesis raises the idea that neurons produced by the resident or transplanted neural stem cells could replace the neurons lost from brain injury or neurodegenerative disease. Therefore, compounds or methods for promoting neuronal differentiation become the focus of neurodegenerative disease therapy research. Claulansine F (Clau F), a newly discovered carbazole alkaloid, has been showed to induce neuritogenesis in PC12 cells. Herein, we studied the effect of Clau F on neuronal differentiation of neural stem/progenitor cells (NS/PCs). The current study demonstrated that Clau F initiated neuronal differentiation with a significant increase of TuJ1-positive cells and TuJ1 protein levels. We also found that Clau F promoted the maturity and sustainability of neurons by increasing MAP2-positive cells and MAP2 protein levels. At the same time, Clau F significantly inhibited the proliferation of NS/PCs. The underlying mechanism of Clau F was preliminary explored. Clau F treatment resulted in a profound increase of phosphorylation of Akt and GSK-3β, which led to GSK-3β inhibition and subsequently the nuclear accumulation of β-catenin. Further, the interaction between β-catenin and p300 in the nucleus was enhanced and the transcription of p300/β-catenin responsive genes were increased significantly (c-jun, fra-1) by Clau F. Importantly, the positive effect of Clau F on neuronal differentiation was abolished by Akti-1/2, a specific inhibitor of Akt-1/2 kinase, which indicated the involvement of Akt/GSK-3β in Clau F-mediated neuronal differentiation. In conclusion, these data suggested that Clau F promoted neuronal differentiation through Akt/GSK-3β/β-catenin signaling pathway in NS/PCs.

PPARγ Is Activated during Congenital Cytomegalovirus Infection and Inhibits Neuronogenesis from Human Neural Stem Cells

Congenital infection by human cytomegalovirus (HCMV) is a leading cause of permanent sequelae of the central nervous system, including sensorineural deafness, cerebral palsies or devastating neurodevelopmental abnormalities (0.1% of all births). To gain insight on the impact of HCMV on neuronal development, we used both neural stem cells from human embryonic stem cells (NSC) and brain sections from infected fetuses and investigated the outcomes of infection on Peroxisome Proliferator-Activated Receptor gamma (PPARγ), a transcription factor critical in the developing brain. We observed that HCMV infection dramatically impaired the rate of neuronogenesis and strongly increased PPARγ levels and activity. Consistent with these findings, levels of 9-hydroxyoctadecadienoic acid (9-HODE), a known PPARγ agonist, were significantly increased in infected NSCs. Likewise, exposure of uninfected NSCs to 9-HODE recapitulated the effect of infection on PPARγ activity. It also increased the rate of cells expressing the IE antigen in HCMV-infected NSCs. Further, we demonstrated that (1) pharmacological activation of ectopically expressed PPARγ was sufficient to induce impaired neuronogenesis of uninfected NSCs, (2) treatment of uninfected NSCs with 9-HODE impaired NSC differentiation and (3) treatment of HCMV-infected NSCs with the PPARγ inhibitor T0070907 restored a normal rate of differentiation. The role of PPARγ in the disease phenotype was strongly supported by the immunodetection of nuclear PPARγ in brain germinative zones of congenitally infected fetuses (N = 20), but not in control samples. Altogether, our findings reveal a key role for PPARγ in neurogenesis and in the pathophysiology of HCMV congenital infection. They also pave the way to the identification of PPARγ gene targets in the infected brain.

Congenital infection by human cytomegalovirus (HCMV) might result in permanent neurological sequelae, including sensorineural deafness, cerebral palsies or devastating neurodevelopmental abnormalities. Infants with such sequelae represent about 0.1% of all live births (>5500 per year in the USA). Given the considerable health and societal burden, a better insight on disease pathogenesis is urgently needed to design new therapeutic or prognostic tools. Here, we studied the impact of HCMV on neuronal development, using human neural progenitors (NSC) as a disease model. In particular, we investigated the outcome of infection on Peroxisome Proliferator-Activated Receptor gamma (PPARγ, a key protein in the regulation of metabolism, inflammation and cell differentiation. We disclosed that HCMV infection strongly increases levels and activity of PPARγ in NSCs. In vitro experiments showed that PPARγ activity inhibits the differentiation of NSCs into neurons. We also found increased PPARγ expression in brains of in utero infected fetuses, but not in controls, suggesting that PPARγ is a key effector of HCMV infection also in vivo. Our study provides new insights on the pathogenesis of HCMV infection and paves the way to the discovery of PPARγ-related molecules secreted in the infected brain.

Crosslinking of extracellular matrix scaffolds derived from pluripotent stem cell aggregates modulates neural differentiation

At various developmental stages, pluripotent stem cells (PSCs) and their progeny secrete a large amount of extracellular matrices (ECMs) which could interact with regulatory growth factors to modulate stem cell lineage commitment. ECMs derived from PSC can be used as unique scaffolds that provide broad signaling capacities to mediate cellular differentiation. However, the rapid degradation of ECMs can impact their applications as the scaffolds for in vitro cell expansion and in vivo transplantation. To address this issue, this study investigated the effects of crosslinking on the ECMs derived from embryonic stem cells (ESCs) and the regulatory capacity of the crosslinked ECMs on the proliferation and differentiation of reseeded ESC-derived neural progenitor cells (NPCs). To create different biological cues, undifferentiated aggregates, spontaneous embryoid bodies, and ESC-derived NPC aggregates were decellularized. The derived ECMs were crosslinked using genipin or glutaraldehyde to enhance the scaffold stability. ESC-derived NPC aggregates were reseeded on different ECM scaffolds and differential cellular compositions of neural progenitors, neurons, and glial cells were observed. The results indicate that ESC-derived ECM scaffolds affect neural differentiation through intrinsic biological cues and biophysical properties. These scaffolds have potential for in vitro cell culture and in vivo tissue regeneration study.

STATEMENT OF SIGNIFICANCE

Dynamic interactions of acellular extracellular matrices and stem cells are critical for lineage-specific commitment and tissue regeneration. Understanding the synergistic effects of biochemical, biological, and biophysical properties of acellular matrices would facilitate scaffold design and the functional regulation of stem cells. The present study assessed the influence of crosslinked embryonic stem cell-derived extracellular matrix on neural differentiation and revealed the synergistic interactions of various matrix properties. While embryonic stem cell-derived matrices have been assessed as tissue engineering scaffolds, the impact of crosslinking on the embryonic stem cell-derived matrices to modulate neural differentiation has not been studied. The results from this study provide novel knowledge on the interface of embryonic stem cell-derived extracellular matrix and neural aggregates. The findings reported in this manuscript are significant for stem cell differentiation toward the applications in stem cell-based drug screening, disease modeling, and cell therapies.

Thyroid Hormone-Otx2 Signaling Is Required for Embryonic Ventral Midbrain Neural Stem Cells Differentiated into Dopamine Neurons

Midbrain dopamine (DA) neurons are essential for maintaining multiple brain functions. These neurons have also been implicated in relation with diverse neurological disorders. However, how these neurons are developed from neuronal stem cells (NSCs) remains largely unknown. In this study, we provide both in vivo and in vitro evidence that the thyroid hormone, an important physiological factor for brain development, promotes DA neuron differentiation from embryonic ventral midbrain (VM) NSCs. We find that thyroid hormone deficiency during development reduces the midbrain DA neuron number, downregulates the expression of tyrosine hydroxylase (TH) and the dopamine transporter (DAT), and impairs the DA neuron-dependent motor behavior. In addition, thyroid hormone treatment during VM NSC differentiation in vitro increases the production of DA neurons and upregulates the expression of TH and DAT. We also found that the thyroid hormone enhances the expression of Otx2, an important determinant of DA neurogenesis, during DA neuron differentiation. Our in vitro gene silencing experiments indicate that Otx2 is required for thyroid hormone-dependent DA neuron differentiation from embryonic VM NSCs. Finally, we revealed both in vivo and in vitro that the thyroid hormone receptor alpha 1 is expressed in embryonic VM NSCs. Furthermore, it participates in the effects of thyroid hormone-induced Otx2 upregulation and DA neuron differentiation. These data demonstrate the role and molecular mechanisms of how the thyroid hormone regulates DA neuron differentiation from embryonic VM NSCs, particularly providing new mechanisms and a potential strategy for generating dopamine neurons from NSCs.

Prospero-related homeobox 1 (Prox1) at the crossroads of diverse pathways during adult neural fate specification

Over the last decades, adult neurogenesis in the central nervous system (CNS) has emerged as a fundamental process underlying physiology and disease. Recent evidence indicates that the homeobox transcription factor Prox1 is a critical intrinsic regulator of neurogenesis in the embryonic CNS and adult dentate gyrus (DG) of the hippocampus, acting in multiple ways and instructed by extrinsic cues and intrinsic factors. In the embryonic CNS, Prox1 is mechanistically involved in the regulation of proliferation vs. differentiation decisions of neural stem cells (NSCs), promoting cell cycle exit and neuronal differentiation, while inhibiting astrogliogenesis. During the complex differentiation events in adult hippocampal neurogenesis, Prox1 is required for maintenance of intermediate progenitors (IPs), differentiation and maturation of glutamatergic interneurons, as well as specification of DG cell identity over CA3 pyramidal fate. The mechanism by which Prox1 exerts multiple functions involves distinct signaling pathways currently not fully highlighted. In this mini-review, we thoroughly discuss the Prox1-dependent phenotypes and molecular pathways in adult neurogenesis in relation to different upstream signaling cues and cell fate determinants. In addition, we discuss the possibility that Prox1 may act as a cross-talk point between diverse signaling cascades to achieve specific outcomes during adult neurogenesis.

Gene expression profiling identifies the zinc-finger protein Charlatan as a regulator of intestinal stem cells in Drosophila

Intestinal stem cells (ISCs) in the adult Drosophila midgut can respond to tissue damage and support repair. We used genetic manipulation to increase the number of ISC-like cells in the adult midgut and performed gene expression profiling to identify potential ISC regulators. A detailed analysis of one of these potential regulators, the zinc-finger protein Charlatan, was carried out. MARCM clonal analysis and RNAi in precursor cells showed that loss of Chn function caused severe ISC division defects, including loss of EdU incorporation, phosphorylated histone 3 staining and expression of the mitotic protein Cdc2. Loss of Charlatan also led to a much reduced histone acetylation staining in precursor cells. Both the histone acetylation and ISC division defects could be rescued by the simultaneous decrease of the Histone Deacetylase 2. The overexpression of Charlatan blocked differentiation reversibly, but loss of Charlatan did not lead to automatic differentiation. The results together suggest that Charlatan does not simply act as an anti-differentiation factor but instead functions to maintain a chromatin structure that is compatible with stem cell properties, including proliferation.

Recent advances in the involvement of long non-coding RNAs in neural stem cell biology and brain pathophysiology

Exploration of non-coding genome has recently uncovered a growing list of formerly unknown regulatory long non-coding RNAs (lncRNAs) with important functions in stem cell pluripotency, development and homeostasis of several tissues. Although thousands of lncRNAs are expressed in mammalian brain in a highly patterned manner, their roles in brain development have just begun to emerge. Recent data suggest key roles for these molecules in gene regulatory networks controlling neuronal and glial cell differentiation. Analysis of the genomic distribution of genes encoding for lncRNAs indicates a physical association of these regulatory RNAs with transcription factors (TFs) with well-established roles in neural differentiation, suggesting that lncRNAs and TFs may form coherent regulatory networks with important functions in neural stem cells (NSCs). Additionally, many studies show that lncRNAs are involved in the pathophysiology of brain-related diseases/disorders. Here we discuss these observations and investigate the links between lncRNAs, brain development and brain-related diseases. Understanding the functions of lncRNAs in NSCs and brain organogenesis could revolutionize the basic principles of developmental biology and neuroscience.