Neural Stem Cells and Methods for Their Generation From Induced Pluripotent Stem Cells in vitro

Multiscale 3D genome rewiring during PTF1A-mediated somatic cell reprogramming into neural stem cells

The genome is intricately folded into chromatin compartments, topologically associating domains (TADs) and loops unique to each cell type. How this higher-order genome organization regulates cell fate transition remains elusive. Here we show how a single non-neural progenitor transcription factor, PTF1A, reorchestrates the 3D genome during fibroblast transdifferentiation into neural stem cells (NSCs). Multiomics analyses integrating Hi-C data, PTF1A and CTCF DNA-binding profiles, H3K27ac modification, and gene expression, demonstrate that PTF1A binds to subTAD boundaries subsequently associated with elevated CTCF binding and enhanced boundary insulation, and reorganizes chromatin loops, leading to gene expression changes that drive transdifferentiation into NSCs. Moreover, PTF1A activates enhancers and super-enhancers near low-insulation boundaries and modulates H3K27ac deposition, promoting cell fate transitions. Together, our data implicate an involvement of 3D genome in transcriptional and cell fate alterations, and highlight an essential role for PTF1A in gene expression control and multiscale 3D genome remodeling during cell reprogramming.

Human stem cell-based models to study synaptic dysfunction and cognition in schizophrenia: A narrative review

Cognitive impairment is the strongest predictor of functional outcomes in schizophrenia and is hypothesized to result from synaptic dysfunction. However, targeting synaptic plasticity and cognitive deficits in patients remains a significant clinical challenge. A comprehensive understanding of synaptic plasticity and the molecular basis of learning and memory in a disease context can provide specific targets for the development of novel therapeutics targeting cognitive impairments in schizophrenia. Here, we describe the role of synaptic plasticity in cognition, summarize evidence for synaptic dysfunction in schizophrenia and demonstrate the use of patient derived induced-pluripotent stem cells for studying synaptic plasticity in vitro. Lastly, we discuss current advances and future technologies for bridging basic science research of synaptic dysfunction with clinical and translational research that can be used to predict treatment response and develop novel therapeutics.

Sequencing-based study of neural induction of human dental pulp stem cells

Techniques for triggering neural differentiation of embryonic and induced pluripotent stem cells into neural stem cells and neurons have been established. However, neural induction of mesenchymal stem cells, including dental pulp stem cells (DPSCs), has been assessed primarily based on neural-related gene regulation, and detailed studies into the characteristics and differentiation status of cells are lacking. Therefore, this study was aimed at evaluating the cellular components and differentiation pathways of neural lineage cells obtained via neural induction of human DPSCs. Human DPSCs were induced to neural cells in monolayer culture and examined for gene expression and mechanisms underlying differentiation using microarray-based ingenuity pathway analysis. In addition, the neural lineage cells were subjected to single-cell RNA sequencing (scRNA-seq) to classify cell populations based on gene expression profiles and to elucidate their differentiation pathways. Ingenuity pathway analysis revealed that genes exhibiting marked overexpression, post-neuronal induction, such as FABP7 and ZIC1, were associated with neurogenesis. Furthermore, in canonical pathway analysis, axon guidance signals demonstrated maximum activation. The scRNA-seq and cell type annotations revealed the presence of neural progenitor cells, astrocytes, neurons, and a small number of non-neural lineage cells. Moreover, trajectory and pseudotime analyses demonstrated that the neural progenitor cells initially engendered neurons, which subsequently differentiated into astrocytes. This result indicates that the aforementioned neural induction strategy generated neural stem/progenitor cells from DPSCs, which might differentiate and proliferate to constitute neural lineage cells. Therefore, neural induction of DPSCs may present an alternative approach to pluripotent stem cell-based therapeutic interventions for nervous system disorders.

The chromodomain protein CDYL confers forebrain identity to human cortical organoids by inhibiting neuronatin

Fate determination of neural stem cells (NSCs) is crucial for cortex development and is closely linked to neurodevelopmental disorders when gene expression networks are disrupted. The transcriptional corepressor chromodomain Y-like (CDYL) is widely expressed across diverse cell populations within the human embryonic cortex. However, its precise role in cortical development remains unclear. Here, we show that CDYL is critical for human cortical neurogenesis and that its deficiency leads to a substantial increase in gamma-aminobutyric acid (GABA)-ergic neurons in cortical organoids. Subsequently, neuronatin (NNAT) is identified as a significant target of CDYL, and its abnormal expression obviously influences the fate commitment of cortical NSCs. Cross-species comparisons of CDYL targets unravel a distinct developmental trajectory between human cortical organoids and the mouse cortex at an analogous stage. Collectively, our data provide insight into the evolutionary roles of CDYL in human cortex development, emphasizing its critical function in maintaining the fate of human cortical NSCs.

A Hybrid 2D-to-3D in vitro Differentiation Platform Improves Outcomes of Cerebral Cortical Organoid Generation in hiPSCs

Three-dimensional (3D) cerebral cortical organoids are popular in vitro cellular model systems widely used to study human brain development and disease, compared to traditional stem cell-derived methods that use two-dimensional (2D) monolayer cultures. Despite the advancements made in protocol development for cerebral cortical organoid derivation over the past decade, limitations due to biological, mechanistic, and technical variables remain in generating these complex 3D cellular systems. Building from our previously established differentiation system, we have made modifications to our existing 3D cerebral cortical organoid protocol that resolve several of these technical and biological challenges when working with diverse groups of human induced pluripotent stem cell (hiPSC) lines. This improved protocol blends a 2D monolayer culture format for the specification of neural stem cells and expansion of neuroepithelial progenitor cells with a 3D system for improved self-aggregation and subsequent organoid development. Furthermore, this "hybrid" approach is amenable to both an accelerated cerebral cortical organoid protocol as well as an alternative long-term differentiation protocol. In addition to establishing a hybrid technical format, this protocol also offers phenotypic and morphological characterization of stage-specific cellular profiles using antibodies and fluorescent-based dyes for live cell imaging. © 2024 Wiley Periodicals LLC. Basic Protocol 1: hiPSC-based 2D monolayer specification into neural stem cells (NSCs) Basic Protocol 2: Serial passaging and 2D monolayer expansion of neuroepithelial progenitor cells (NPCs) Support Protocol 1: Direct cryopreservation and rapid thawing of NSCs and NPCs Basic Protocol 3: Bulk aggregation of 3D neurospheres and accelerated cerebral cortical organoid differentiation Alternate Protocol 1: Bulk aggregation of 3D neurospheres and long-term cerebral cortical organoid differentiation Support Protocol 2: High-throughput 3D neurosphere formation and 2D neurosphere migration assay Support Protocol 3: LIVE/DEAD stain cell imaging assay of 3D neurospheres Support Protocol 4: NeuroFluor NeuO live cell dye for 3D cerebral cortical organoids.

Application of cell transplantation in the treatment of neuropathic pain

Nerve injury can not only lead to sensory and motor dysfunction, but also be complicated with neuropathic pain (NPP), which brings great psychosomatic injury to patients. At present, there is no effective treatment for NPP. Based on the functional characteristics of cell transplantation in nerve regeneration and injury repair, cell therapy has been used in the exploratory treatment of NPP and has become a promising treatment of NPP. In this article, we discuss the current mainstream cell types for the treatment of NPP, including Schwann cells, olfactory ensheathing cells, neural stem cells and mesenchymal stem cells in the treatment of NPP. These bioactive cells transplanted into the host have pharmacological properties of decreasing pain threshold and relieving NPP by exerting nutritional support, neuroprotection, immune regulation, promoting axonal regeneration, and remyelination. Cell transplantation can also change the microenvironment around the nerve injury, which is conducive to the survival of neurons. It can effectively relieve pain by repairing the injured nerve and rebuilding the nerve function. At present, some preclinical and clinical studies have shown that some encouraging results have been achieved in NPP treatment based on cell transplantation. Therefore, we discussed the feasible strategy of cell transplantation as a treatment of NPP and the problems and challenges that need to be solved in the current application of cell transplantation in NPP therapy.

In vitro human cell culture models in a bench-to-bedside approach to epilepsy

Epilepsy is the most common chronic neurological disease, affecting nearly 1%-2% of the world's population. Current pharmacological treatment and regimen adjustments are aimed at controlling seizures; however, they are ineffective in one-third of the patients. Although neuronal hyperexcitability was previously thought to be mainly due to ion channel alterations, current research has revealed other contributing molecular pathways, including processes involved in cellular signaling, energy metabolism, protein synthesis, axon guidance, inflammation, and others. Some forms of drug-resistant epilepsy are caused by genetic defects that constitute potential targets for precision therapy. Although such approaches are increasingly important, they are still in the early stages of development. This review aims to provide a summary of practical aspects of the employment of in vitro human cell culture models in epilepsy diagnosis, treatment, and research. First, we briefly summarize the genetic testing that may result in the detection of candidate pathogenic variants in genes involved in epilepsy pathogenesis. Consequently, we review existing in vitro cell models, including induced pluripotent stem cells and differentiated neuronal cells, providing their specific properties, validity, and employment in research pipelines. We cover two methodological approaches. The first approach involves the utilization of somatic cells directly obtained from individual patients, while the second approach entails the utilization of characterized cell lines. The models are evaluated in terms of their research and clinical benefits, relevance to the in vivo conditions, legal and ethical aspects, time and cost demands, and available published data. Despite the methodological, temporal, and financial demands of the reviewed models they possess high potential to be used as robust systems in routine testing of pathogenicity of detected variants in the near future and provide a solid experimental background for personalized therapy of genetic epilepsies. PLAIN LANGUAGE SUMMARY: Epilepsy affects millions worldwide, but current treatments fail for many patients. Beyond traditional ion channel alterations, various genetic factors contribute to the disorder's complexity. This review explores how in vitro human cell models, either from patients or from cell lines, can aid in understanding epilepsy's genetic roots and developing personalized therapies. While these models require further investigation, they offer hope for improved diagnosis and treatment of genetic forms of epilepsy.

Emerging Pro-neurogenic Therapeutic Strategies for Neurodegenerative Diseases: A Review of Pre-clinical and Clinical Research

The neuroscience community has largely accepted the notion that functional neurons can be generated from neural stem cells in the adult brain, especially in two brain regions: the subventricular zone of the lateral ventricles and the subgranular zone in the dentate gyrus of the hippocampus. However, impaired neurogenesis has been observed in some neurodegenerative diseases, particularly in Alzheimer's, Parkinson's, and Huntington's diseases, and also in Lewy Body dementia. Therefore, restoration of neurogenic function in neurodegenerative diseases emerges as a potential therapeutic strategy to counteract, or at least delay, disease progression. Considering this, the present study summarizes the different neuronal niches, provides a collection of the therapeutic potential of different pro-neurogenic strategies in pre-clinical and clinical research, providing details about their possible modes of action, to guide future research and clinical practice.

Multiple factors to assist human-derived induced pluripotent stem cells to efficiently differentiate into midbrain dopaminergic neurons

Midbrain dopaminergic neurons play an important role in the etiology of neurodevelopmental and neurodegenerative diseases. They also represent a potential source of transplanted cells for therapeutic applications. In vitro differentiation of functional midbrain dopaminergic neurons provides an accessible platform to study midbrain neuronal dysfunction and can be used to examine obstacles to dopaminergic neuronal development. Emerging evidence and impressive advances in human induced pluripotent stem cells, with tuned neural induction and differentiation protocols, makes the production of induced pluripotent stem cell-derived dopaminergic neurons feasible. Using SB431542 and dorsomorphin dual inhibitor in an induced pluripotent stem cell-derived neural induction protocol, we obtained multiple subtypes of neurons, including 20% tyrosine hydroxylase-positive dopaminergic neurons. To obtain more dopaminergic neurons, we next added sonic hedgehog (SHH) and fibroblast growth factor 8 (FGF8) on day 8 of induction. This increased the proportion of dopaminergic neurons, up to 75% tyrosine hydroxylase-positive neurons, with 15% tyrosine hydroxylase and forkhead box protein A2 (FOXA2) co-expressing neurons. We further optimized the induction protocol by applying the small molecule inhibitor, CHIR99021 (CHIR).This helped facilitate the generation of midbrain dopaminergic neurons, and we obtained 31-74% midbrain dopaminergic neurons based on tyrosine hydroxylase and FOXA2 staining. Thus, we have established three induction protocols for dopaminergic neurons. Based on tyrosine hydroxylase and FOXA2 immunostaining analysis, the CHIR, SHH, and FGF8 combined protocol produces a much higher proportion of midbrain dopaminergic neurons, which could be an ideal resource for tackling midbrain-related diseases.

Neural repair and regeneration interfaces: a comprehensive review

Neural interfaces play a pivotal role in neuromodulation, as they enable precise intervention into aberrant neural activity and facilitate recovery from neural injuries and resultant functional impairments by modulating local immune responses and neural circuits. This review outlines the development and applications of these interfaces and highlights the advantages of employing neural interfaces for neural stimulation and repair, including accurate targeting of specific neural populations, real-time monitoring and control of neural activity, reduced invasiveness, and personalized treatment strategies. Ongoing research aims to enhance the biocompatibility, stability, and functionality of these interfaces, ultimately augmenting their therapeutic potential for various neurological disorders. The review focuses on electrophysiological and optophysiology neural interfaces, discussing functionalization and power supply approaches. By summarizing the techniques, materials, and methods employed in this field, this review aims to provide a comprehensive understanding of the potential applications and future directions for neural repair and regeneration devices.

Deciphering the impact of cerebrospinal fluid on stem cell fate as a new mechanism to enhance clinical therapy development

Neural stem cells (NSCs) hold a very significant promise as candidates for cell therapy due to their robust neuroprotective and regenerative properties. Preclinical studies using NSCs have shown enough encouraging results to perform deeper investigations into more potential clinical applications. Nevertheless, our knowledge regarding neurogenesis and its underlying mechanisms remains incomplete. To understand them better, it seems necessary to characterize all components of neural stem cell niche and discover their role in physiology and pathology. Using NSCs in vivo brings challenges including limited cell survival and still inadequate integration within host tissue. Identifying overlooked factors that might influence these outcomes becomes pivotal. In this review, we take a deeper examination of the influence of a fundamental element that is present in the brain, the cerebrospinal fluid (CSF), which still remains relatively unexplored. Its role in neurogenesis could be instrumental to help find novel therapeutic solutions for neurological disorders, eventually advancing our knowledge on central nervous system (CNS) regeneration and repair.

A new advanced cellular model of functional cholinergic-like neurons developed by reprogramming the human SH-SY5Y neuroblastoma cell line

Modeling human neuronal properties in physiological and pathological conditions is essential to identify novel potential drugs and to explore pathological mechanisms of neurological diseases. For this purpose, we generated a three-dimensional (3D) neuronal culture, by employing the readily available human neuroblastoma SH-SY5Y cell line, and a new differentiation protocol. The entire differentiation process occurred in a matrix and lasted 47 days, with 7 days of pre-differentiation phase and 40 days of differentiation, and allowed the development of a 3D culture in conditions consistent with the physiological environment. Neurons in the culture were electrically active, were able to establish functional networks, and showed features of cholinergic neurons. Hence here we provide an easily accessible, reproducible, and suitable culture method that might empower studies on synaptic function, vesicle trafficking, and metabolism, which sustain neuronal activity and cerebral circuits. Moreover, this novel differentiation protocol could represent a promising cellular tool to study physiological cellular processes, such as migration, differentiation, maturation, and to develop novel therapeutic approaches.

Bibliometric Analysis of Stem Cells in Ischemic Stroke (2001-2022): Trends, Hotspots and Prospects

Background: Ischemic stroke is a common cerebrovascular accident with a high risk of neurological deficits. Stem cell therapy has progressively attracted the interest of scientists and clinicians due to the benefits of promoting neural regeneration and regulating the microenvironment surrounding the lesion after ischemic stroke. Our study aimed to evaluate the development trends and research hotspots in the field of stem cells and ischemic stroke. Materials and methods: Publications related to stem cells and ischemic stroke were retrieved from the Web of Science from 2001 to 2022. Data analysis and mapping were performed using VOSviewer, Citespace and ImageGP. Results: In total, 1932 papers were included in the analysis. Publications have steadily increased over the past 22 years. China has contributed the maximum number of publications, whereas the USA ranked first in the total number of citations and was considered the center of the international collaboration network. University of South Florida, Henry Ford Hospital, and Oakland University were the most influential institutions. Stroke, Brain Research, and Neural Regeneration Research were the most productive journals. The research in this field was primarily focused on the effects of stem cells on neurogenesis, inflammation, and angiogenesis following ischemic stroke, as well as their therapeutic potential for the disease. In addition, neural stem cells and mesenchymal stem cells are the most commonly utilized stem cells. The topics related to miRNA, extracellular vesicles, exosomes, mesenchymal stem cells, neuroinflammation, and autophagy are current research hotspots. Conclusion: Our bibliometric study provides a novel perspective on the research trends in the field of stem cells and ischemic stroke. The outcome of this study may benefit scientists to identify research hotspots and development directions, thereby advancing the application of stem cell-based therapy for ischemic stroke.

Neural Stem Cell-based Regenerative Therapy: A New Approach to Diabetes Treatment

Diabetes mellitus (DM) is the most common metabolic disorder that occurs due to the loss, or impaired function of insulin-secreting pancreatic beta cells, which are of two types - type 1 (T1D) and type 2 (T2D). To cure DM, the replacement of the destroyed pancreatic beta cells of islet of Langerhans is the most widely practiced treatment. For this, isolating neuronal stem cells and cultivating them as a source of renewable beta cells is a significant breakthrough in medicine. The functions, growth, and gene expression of insulin-producing pancreatic beta cells and neurons are very similar in many ways. A diabetic patient's neural stem cells (obtained from the hippocampus and olfactory bulb) can be used as a replacement source of beta cells for regenerative therapy to treat diabetes. The same protocol used to create functional neurons from progenitor cells can be used to create beta cells. Recent research suggests that replacing lost pancreatic beta cells with autologous transplantation of insulin-producing neural progenitor cells may be a perfect therapeutic strategy for diabetes, allowing for a safe and normal restoration of function and a reduction in potential risks and a long-term cure.

Potential Therapeutic Use of Stem Cells for Prion Diseases

Prion diseases are neurodegenerative disorders that are progressive, incurable, and deadly. The prion consists of PrPSc, the misfolded pathogenic isoform of the cellular prion protein (PrPC). PrPC is involved in a variety of physiological functions, including cellular proliferation, adhesion, differentiation, and neural development. Prion protein is expressed on the membrane surface of a variety of stem cells (SCs), where it plays an important role in the pluripotency and self-renewal matrix, as well as in SC differentiation. SCs have been found to multiply the pathogenic form of the prion protein, implying their potential as an in vitro model for prion diseases. Furthermore, due to their capability to self-renew, differentiate, immunomodulate, and regenerate tissue, SCs are prospective cell treatments in many neurodegenerative conditions, including prion diseases. Regenerative medicine has become a new revolution in disease treatment in recent years, particularly with the introduction of SC therapy. Here, we review the data demonstrating prion diseases' biology and molecular mechanism. SC biology, therapeutic potential, and its role in understanding prion disease mechanisms are highlighted. Moreover, we summarize preclinical studies that use SCs in prion diseases.

A robust and reliable methodology to perform GECI-based multi-time point neuronal calcium imaging within mixed cultures of human iPSC-derived cortical neurons

Introduction

Human induced pluripotent stem cells (iPSCs), with their ability to generate human neural cells (astrocytes and neurons) from patients, hold great promise for understanding the pathophysiology of major neuropsychiatric diseases such as schizophrenia and bipolar disorders, which includes alterations in cerebral development. Indeed, the in vitro neurodifferentiation of iPSCs, while recapitulating certain major stages of neurodevelopment in vivo, makes it possible to obtain networks of living human neurons. The culture model presented is particularly attractive within this framework since it involves iPSC-derived neural cells, which more specifically differentiate into cortical neurons of diverse types (in particular glutamatergic and GABAergic) and astrocytes. However, these in vitro neuronal networks, which may be heterogeneous in their degree of differentiation, remain challenging to bring to an appropriate level of maturation. It is therefore necessary to develop tools capable of analyzing a large number of cells to assess this maturation process. Calcium (Ca2+) imaging, which has been extensively developed, undoubtedly offers an incredibly good approach, particularly in its versions using genetically encoded calcium indicators. However, in the context of these iPSC-derived neural cell cultures, there is a lack of studies that propose Ca2+ imaging methods that can finely characterize the evolution of neuronal maturation during the neurodifferentiation process.

Methods

In this study, we propose a robust and reliable method for specifically measuring neuronal activity at two different time points of the neurodifferentiation process in such human neural cultures. To this end, we have developed a specific Ca2+ signal analysis procedure and tested a series of different AAV serotypes to obtain expression levels of GCaMP6f under the control of the neuron-specific human synapsin1 (hSyn) promoter.

Results

The retro serotype has been found to be the most efficient in driving the expression of the GCaMP6f and is compatible with multi-time point neuronal Ca2+ imaging in our human iPSC-derived neural cultures. An AAV2/retro carrying GCaMP6f under the hSyn promoter (AAV2/retro-hSyn-GCaMP6f) is an efficient vector that we have identified. To establish the method, calcium measurements were carried out at two time points in the neurodifferentiation process with both hSyn and CAG promoters, the latter being known to provide high transient gene expression across various cell types.

Discussion

Our results stress that this methodology involving AAV2/retro-hSyn-GCaMP6f is suitable for specifically measuring neuronal calcium activities over multiple time points and is compatible with the neurodifferentiation process in our mixed human neural cultures.

Genetically engineered neural stem cells (NSCs) therapy for neurological diseases; state-of-the-art

Neural stem cells (NSCs) are multipotent stem cells with remarkable self-renewal potential and also unique competencies to differentiate into neurons, astrocytes, and oligodendrocytes (ODCs) and improve the cellular microenvironment. In addition, NSCs secret diversity of mediators, including neurotrophic factors (e.g., BDNF, NGF, GDNF, CNTF, and NT-3), pro-angiogenic mediators (e.g., FGF-2 and VEGF), and anti-inflammatory biomolecules. Thereby, NSCs transplantation has become a reasonable and effective treatment for various neurodegenerative disorders by their capacity to induce neurogenesis and vasculogenesis and dampen neuroinflammation and oxidative stress. Nonetheless, various drawbacks such as lower migration and survival and less differential capacity to a particular cell lineage concerning the disease pathogenesis hinder their application. Thus, genetic engineering of NSCs before transplantation is recently regarded as an innovative strategy to bypass these hurdles. Indeed, genetically modified NSCs could bring about more favored therapeutic influences post-transplantation in vivo, making them an excellent option for neurological disease therapy. This review for the first time offers a comprehensive review of the therapeutic capability of genetically modified NSCs rather than naïve NSCs in neurological disease beyond brain tumors and sheds light on the recent progress and prospect in this context.

Functional Analysis of a Novel Immortalized Murine Microglia Cell Line in 3D Spheroid Model

Microglia are the residential immune cells of central nervous system and they are crucial for brain development and homeostasis, as well as the progression of inflammatory brain diseases. To study microglia's physiological and pathological functions, one of the most widely used models is primary microglia culture from neonatal rodents. However, primary microglia culture is time consuming and needs a great number of animals. In our microglia culture, we found a strain of spontaneously immortalized microglia that continued to divide without any known genetic intervention. We confirmed the immortalization of these cells for uninterrupted thirty passages and we named them as immortalized microglia like-1 cells (iMG-1). The iMG-1 cells kept their microglia morphology, and they expressed macrophage/microglia-specific proteins of CD11b, CD68, P2RY12, and IBA1 in vitro. iMG-1 cells were responsive to inflammatory stimulations with lipopolysaccharide (LPS) and Polyinosinic:polycytidylic acid (pIpC), triggering increased mRNA/protein levels of IL1-β, IL-6, TNF-α, and interferons. LPS and pIpC treated iMG-1 cells also significantly increased their accumulation of lipid droplets (LDs). We also generated a 3D spheroid model using immortalized neural progenitor cells and iMG-1 cells with defined percentages to study neuroinflammation. The iMG-1 cells distributed evenly in spheroids, and they regulated the basal mRNA levels of cytokines of neural progenitors in 3D spheroid. iMG-1 cells were responsive to LPS by increased expression of IL-6 and IL1-β in spheroids. Together, this study indicated the reliability of iMG-1 which could be readily available to study the physiological and pathological functions of microglia.

Proteomics and disease network associations evaluation of environmentally relevant Bisphenol A concentrations in a human 3D neural stem cell model

Bisphenol A (BPA) exposure is associated with a plethora of neurodevelopmental abnormalities and brain disorders. Previous studies have demonstrated BPA-induced perturbations to critical neural stem cell (NSC) characteristics, such as proliferation and differentiation, although the underlying molecular mechanisms remain under debate. The present study evaluated the effects of a repeated-dose exposure of environmentally relevant BPA concentrations during the in vitro 3D neural induction of human induced pluripotent stem cells (hiPSCs), emulating a chronic exposure scenario. Firstly, we demonstrated that our model is suitable for NSC differentiation during the early stages of embryonic brain development. Our morphological image analysis showed that BPA exposure at 0.01, 0.1 and 1 µM decreased the average spheroid size by day 21 (D21) of the neural induction, while no effect on cell viability was detected. No alteration to the rate of the neural induction was observed based on the expression of key neural lineage and neuroectodermal transcripts. Quantitative proteomics at D21 revealed several differentially abundant proteins across all BPA-treated groups with important functions in NSC proliferation and maintenance (e.g., FABP7, GPC4, GAP43, Wnt-8B, TPPP3). Additionally, a network analysis demonstrated alterations to the glycolytic pathway, potentially implicating BPA-induced changes to glycolytic signalling in NSC proliferation impairments, as well as the pathophysiology of brain disorders including intellectual disability, autism spectrum disorders, and amyotrophic lateral sclerosis (ALS). This study enhances the current understanding of BPA-related NSC aberrations based mostly on acute, often high dose exposures of rodent in vivo and in vitro models and human GWAS data in a novel human 3D cell-based model with real-life scenario relevant prolonged and low-level exposures, offering further mechanistic insights into the ramifications of BPA exposure on the developing human brain and consequently, later life neurological disorders.

Regulatory mechanisms of stem cell differentiation: Biotechnological applications for neurogenesis

The world population's life expectancy is growing, and neurodegenerative disorders common in old age require more efficient therapies. In this context, neural stem cells (NSCs) are imperative for the development and maintenance of the functioning of the nervous system and have broad therapeutic applicability for neurodegenerative diseases. Therefore, knowing all the mechanisms that govern the self-renewal, differentiation, and cell signaling of NSC is necessary. This review will address some of these aspects, including the role of growth and transcription factors, epigenetic modulators, microRNAs, and extracellular matrix components. Furthermore, differentiation and transdifferentiation processes will be addressed as therapeutic strategies showing their significance for stem cell-based therapy.

Decellularized Extracellular Matrix: The Role of This Complex Biomaterial in Regeneration

Organ transplantation is understood as a technique where an organ from a donor patient is transferred to a recipient patient. This practice gained strength in the 20th century and ensured advances in areas of knowledge such as immunology and tissue engineering. The main problems that comprise the practice of transplants involve the demand for viable organs and immunological aspects related to organ rejection. In this review, we address advances in tissue engineering for reversing the current challenges of transplants, focusing on the possible use of decellularized tissues in tissue engineering. We address the interaction of acellular tissues with immune cells, especially macrophages and stem cells, due to their potential use in regenerative medicine. Our goal is to exhibit data that demonstrate the use of decellularized tissues as alternative biomaterials that can be applied clinically as partial or complete organ substitutes.

Protocol for a Wnt reporter assay to measure its activity in human neural stem cells derived from induced pluripotent stem cells

The canonical Wnt signaling is an essential pathway that regulates cellular proliferation, maturation, and differentiation during neurodevelopment and maintenance of adult tissue homeostasis. This pathway has been implicated with the pathophysiology of neuropsychiatric disorders and was associated with cognitive processes, such as learning and memory. However, the molecular investigation of the Wnt signaling in functional human neural cell lines might be challenging since brain biopsies are not possible and animal models may not represent the polygenic profile of some neurological and neurodevelopmental disorders. In this context, using induced pluripotent stem cells (iPSCs) has become a powerful tool to model disorders that affect the Central Nervous System (CNS) in vitro, by maintaining patients' genetic backgrounds. In this method paper, we report the development of a virus-free Wnt reporter assay in neural stem cells (NSCs) derived from human iPSCs from two healthy individuals, by using a vector containing a reporter gene (luc2P) under the control of a TCF/LEF (T-cell factor/lymphoid enhancer factor) responsive element. Dose-response curve analysis from this luciferase-based method might be useful when testing the activity of the Wnt signaling pathway after agonists (e.g. Wnt3a) or antagonists (e.g. DKK1) administration, comparing activity between cases and controls in distinct disorders. Using such a reporter assay method may help to elucidate whether neurological or neurodevelopmental mental disorders show alterations in this pathway, and testing whether targeted treatment may reverse these. Therefore, our established assay aims to help researchers on the functional and molecular investigation of the Wnt pathway in patient-specific cell types comprising several neuropsychiatric disorders.

Alzheimer's Disease Treatment: The Search for a Breakthrough

As the search for modalities to cure Alzheimer's disease (AD) has made slow progress, research has now turned to innovative pathways involving neural and peripheral inflammation and neuro-regeneration. Widely used AD treatments provide only symptomatic relief without changing the disease course. The recently FDA-approved anti-amyloid drugs, aducanumab and lecanemab, have demonstrated unclear real-world efficacy with a substantial side effect profile. Interest is growing in targeting the early stages of AD before irreversible pathologic changes so that cognitive function and neuronal viability can be preserved. Neuroinflammation is a fundamental feature of AD that involves complex relationships among cerebral immune cells and pro-inflammatory cytokines, which could be altered pharmacologically by AD therapy. Here, we provide an overview of the manipulations attempted in pre-clinical experiments. These include inhibition of microglial receptors, attenuation of inflammation and enhancement of toxin-clearing autophagy. In addition, modulation of the microbiome-brain-gut axis, dietary changes, and increased mental and physical exercise are under evaluation as ways to optimize brain health. As the scientific and medical communities work together, new solutions may be on the horizon to slow or halt AD progression.

Bioengineered perfused human brain microvascular networks enhance neural progenitor cell survival, neurogenesis, and maturation

Neural progenitor cells (NPCs) have the capability to self-renew and differentiate into neurons and glial cells. In the adult brain, NPCs are found near brain microvascular networks (BMVNs) in specialized microenvironments called the neurovascular niche (NVN). Although several in vitro NVN models have been previously reported, most do not properly recapitulate the intimate cellular interactions between NPCs and perfused brain microvessels. Here, we developed perfused BMVNs composed of primary human brain endothelial cells, pericytes, and astrocytes within microfluidic devices. When induced pluripotent stem cell-derived NPCs were introduced into BMVNs, we found that NPC survival, neurogenesis, and maturation were enhanced. The application of flow during BMVN coculture was also beneficial for neuron differentiation. Collectively, our work highlighted the important role of BMVNs and flow in NPC self-renewal and neurogenesis, as well as demonstrated our model's potential to study the biological and physical interactions of human NVN in vitro.

Molecular and Functional Characterization of Different BrainSphere Models for Use in Neurotoxicity Testing on Microelectrode Arrays

The currently accepted methods for neurotoxicity (NT) testing rely on animal studies. However, high costs and low testing throughput hinder their application for large numbers of chemicals. To overcome these limitations, in vitro methods are currently being developed based on human-induced pluripotent stem cells (hiPSC) that allow higher testing throughput at lower costs. We applied six different protocols to generate 3D BrainSphere models for acute NT evaluation. These include three different media for 2D neural induction and two media for subsequent 3D differentiation resulting in self-organized, organotypic neuron/astrocyte microtissues. All induction protocols yielded nearly 100% NESTIN-positive hiPSC-derived neural progenitor cells (hiNPCs), though with different gene expression profiles concerning regional patterning. Moreover, gene expression and immunocytochemistry analyses revealed that the choice of media determines neural differentiation patterns. On the functional level, BrainSpheres exhibited different levels of electrical activity on microelectrode arrays (MEA). Spike sorting allowed BrainSphere functional characterization with the mixed cultures consisting of GABAergic, glutamatergic, dopaminergic, serotonergic, and cholinergic neurons. A test method for acute NT testing, the human multi-neurotransmitter receptor (hMNR) assay, was proposed to apply such MEA-based spike sorting. These models are promising tools not only in toxicology but also for drug development and disease modeling.

Complement in the Brain: Contributions to Neuroprotection, Neuronal Plasticity, and Neuroinflammation

The complement system is an ancient collection of proteolytic cascades with well-described roles in regulation of innate and adaptive immunity. With the convergence of a revolution in complement-directed clinical therapeutics, the discovery of specific complement-associated targetable pathways in the central nervous system, and the development of integrated multi-omic technologies that have all emerged over the last 15 years, precision therapeutic targeting in Alzheimer disease and other neurodegenerative diseases and processes appears to be within reach. As a sensor of tissue distress, the complement system protects the brain from microbial challenge as well as the accumulation of dead and/or damaged molecules and cells. Additional more recently discovered diverse functions of complement make it of paramount importance to design complement-directed neurotherapeutics such that the beneficial roles in neurodevelopment, adult neural plasticity, and neuroprotective functions of the complement system are retained.

Generation of hypothalamic neural stem cell-like cells in vitro from human pluripotent stem cells

When damaged, restoring the function of the hypothalamus is currently impossible. It is unclear whether neural stem cells exist in the hypothalamus. Studies have reported that adult rodent tanycytes around the third ventricle function as hypothalamic neural stem cell-like cells. However, it is currently impossible to collect periventricular cells from humans. We attempted to generate hypothalamic neural stem cell-like cells from human embryonic stem cells (ESCs). We focused on retina and anterior neural fold homeobox (RAX) because its expression is gradually restricted to tanycytes during the late embryonic stage. We differentiated RAX::VENUS knockin human ESCs (hESCs) into hypothalamic organoids and sorted RAX⁺ cells from mature organoids. The isolated RAX⁺ cells formed neurospheres and exhibited self-renewal and multipotency. Neurogenesis was observed when neurospheres were transplanted into the mouse hypothalamus. We isolated RAX⁺ hypothalamic neural stem cell-like cells from wild-type human ES organoids. This is the first study to differentiate human hypothalamic neural stem cell-like cells from pluripotent stem cells.

Critical points for optimizing long-term culture and neural differentiation capacity of rodent and human neural stem cells to facilitate translation into clinical settings

Despite several decades of research on the nature and functional properties of neural stem cells, which brought great advances in regenerative medicine, there is still a plethora of ambiguous protocols and interpretations linked to their applications. Here, we present a whole spectrum of protocol elements that should be standardized in order to obtain viable cell cultures and facilitate their translation into clinical settings. Additionally, this review also presents outstanding limitations and possible problems to be encountered when dealing with protocol optimization. Most importantly, we also outline the critical points that should be considered before starting any experiments utilizing neural stem cells or interpreting their results.

Transcription factor SOX15 regulates stem cell pluripotency and promotes neural fate during differentiation by activating the neurogenic gene Hes5

SOX2 and SOX15 are Sox family transcription factors enriched in embryonic stem cells (ESCs). The role of SOX2 in activating gene expression programs essential for stem cell self-renewal and acquisition of pluripotency during somatic cell reprogramming is well-documented. However, the contribution of SOX15 to these processes is unclear and often presumed redundant with SOX2 largely because overexpression of SOX15 can partially restore self-renewal in SOX2-deficient ESCs. Here, we show that SOX15 contributes to stem cell maintenance by cooperating with ESC-enriched transcriptional coactivators to ensure optimal expression of pluripotency-associated genes. We demonstrate that SOX15 depletion compromises reprogramming of fibroblasts to pluripotency which cannot be compensated by SOX2. Ectopic expression of SOX15 promotes the reversion of a postimplantation, epiblast stem cell state back to a preimplantation, ESC-like identity even though SOX2 is expressed in both cell states. We also uncover a role of SOX15 in lineage specification, by showing that loss of SOX15 leads to defects in commitment of ESCs to neural fates. SOX15 promotes neural differentiation by binding to and activating a previously uncharacterized distal enhancer of a key neurogenic regulator, Hes5. Together, these findings identify a multifaceted role of SOX15 in induction and maintenance of pluripotency and neural differentiation.

Extracellular vesicles throughout development: A potential roadmap for emerging glioblastoma therapies

Extracellular vesicles (EVs) are membrane-delimited vesicular bodies carrying different molecules, classified according to their size, density, cargo, and origin. Research on this topic has been actively growing through the years, as EVs are associated with critical pathological processes such as neurodegenerative diseases and cancer. Despite that, studies exploring the physiological functions of EVs are sparse, with particular emphasis on their role in organismal development, initial cell differentiation, and morphogenesis. In this review, we explore the topic of EVs from a developmental perspective, discussing their role in the earliest cell-fate decisions and neural tissue morphogenesis. We focus on the function of EVs through development to highlight possible conserved or novel processes that can impact disease progression. Specifically, we take advantage of what was learned about their role in development so far to discuss EVs impact on glioblastoma, a particular brain tumor of stem-cell origin and poor prognosis, and how their function can be hijacked to improve current therapies.

Different iPSC-derived neural stem cells shows various spectrums of spontaneous differentiation during long term cultivation

Introduction

Culturing of human neural stem cells (NSCs) derived from induced pluripotent stem cells (iPSC) is a promising area of research, as these cells have the potential to treat a wide range of neurological, neurodegenerative and psychiatric diseases. However, the development of optimal protocols for the production and long-term culturing of NSCs remains a challenge. One of the most important aspects of this problem is to determine the stability of NSCs during long-term in vitro passaging. To address this problem, our study was aimed at investigating the spontaneous differentiation profile in different iPSC-derived human NSCs cultures during long-term cultivation using.

Methods

Four different IPSC lines were used to generate NSC and spontaneously differentiated neural cultures using DUAL SMAD inhibition. These cells were analyzed at different passages using immunocytochemistry, qPCR, bulk transcriptomes and scRNA-seq.

Results

We found that various NSC lines generate significantly different spectrums of differentiated neural cells, which can also change significantly during long-term cultivation in vitro.

Discussion

Our results indicate that both internal (genetic and epigenetic) and external (conditions and duration of cultivation) factors influence the stability of NSCs. These results have important implications for the development of optimal NSCs culturing protocols and highlight the need to further investigate the factors influencing the stability of these cells in vitro.

Characterization of Human-Induced Neural Stem Cells and Derivatives following Transplantation into the Central Nervous System of a Nonhuman Primate and Rats

Neural stem cells (NSCs) and derivatives are potential cellular sources to treat neurological diseases. In the current study, we reprogrammed human peripheral blood mononuclear cells into induced NSCs (iNSCs) and inserted GFP gene into the AAVS1 site for graft tracing. Targeted integration of GFP does not affect the proliferation and differentiation capacity of iNSCs. iNSC-GFP can be further differentiated into dopaminergic precursors (DAPs) and motor neuron precursors (MNPs), respectively. iNSCs were engrafted into the motor cortex and iNSC-DAPs into the striatum and substantia nigra (SN) of a nonhuman primate, respectively. The surviving iNSCs could respond to the microenvironment of the cortex and spontaneously differentiate into mature neurons that extended neurites. iNSC-DAPs survived well and matured into DA neurons following transplantation into the striatum and SN. iNSC-MNPs could also survive and turn into motor neurons after being engrafted into the spinal cord of rats. The results suggest that iNSCs and derivatives have a potential to be used for the treatment of neurological diseases.

Variation of DNA methylation on the IRX1/2 genes is responsible for the neural differentiation propensity in human induced pluripotent stem cells

Introduction

Human induced pluripotent stem cells (hiPSCs) are useful tools for reproducing neural development in vitro. However, each hiPSC line has a different ability to differentiate into specific lineages, known as differentiation propensity, resulting in reduced reproducibility and increased time and funding requirements for research. To overcome this issue, we searched for predictive signatures of neural differentiation propensity of hiPSCs focusing on DNA methylation, which is the main modulator of cellular properties.

Methods

We obtained 32 hiPSC lines and their comprehensive DNA methylation data using the Infinium MethylationEPIC BeadChip. To assess the neural differentiation efficiency of these hiPSCs, we measured the percentage of neural stem cells on day 7 of induction. Using the DNA methylation data of undifferentiated hiPSCs and their measured differentiation efficiency into neural stem cells as the set of data, and HSIC Lasso, a machine learning-based nonlinear feature selection method, we attempted to identify neural differentiation-associated differentially methylated sites.

Results

Epigenome-wide unsupervised clustering cannot distinguish hiPSCs with varying differentiation efficiencies. In contrast, HSIC Lasso identified 62 CpG sites that could explain the neural differentiation efficiency of hiPSCs. Features selected by HSIC Lasso were particularly enriched within 3 Mbp of chromosome 5, harboring IRX1, IRX2, and C5orf38 genes. Within this region, DNA methylation rates were correlated with neural differentiation efficiency and were negatively correlated with gene expression of the IRX1/2 genes, particularly in female hiPSCs. In addition, forced expression of the IRX1/2 impaired the neural differentiation ability of hiPSCs in both sexes.

Conclusion

We for the first time showed that the DNA methylation state of the IRX1/2 genes of hiPSCs is a predictive biomarker of their potential for neural differentiation. The predictive markers for neural differentiation efficiency identified in this study may be useful for the selection of suitable undifferentiated hiPSCs prior to differentiation induction.

Dialysis based-culture medium conditioning improved the generation of human induced pluripotent stem cell derived-liver organoid in a high cell density

Human pluripotent stem cell-derived liver organoids (HLOs) have recently become a promising alternative for liver regenerative therapy. To realize this application, a large amount of human-induced pluripotent stem cells (hiPSCs) derived-liver cells are required for partial liver replacement during transplantation. This method requires stepwise induction using costly growth factors to direct the hiPSCs into the hepatic lineage. Therefore, we developed a simple dialysis-based medium conditioning that fully utilized growth factors accumulation to improve hepatic differentiation of hiPSCs at a high cell density. The results demonstrated that the dialysis culture system could accumulate the four essential growth factors required in each differentiation stage: activin A, bone morphogenetic protein 4 (BMP4), hepatocyte growth factor (HGF), and oncostatin M (OSM). As a result, this low lactate culture environment allowed high-density bipotential hepatic differentiation of up to 4.5 × 10⁷ cells/mL of human liver organoids (HLOs), consisting of hiPSC derived-hepatocyte like cells (HLCs) and cholangiocyte like-cells (CLCs). The differentiated HLOs presented a better or comparable hepatic marker and hepatobiliary physiology to the one that differentiated in suspension culture with routine daily medium replacement at a lower cell density. This simple miniaturized dialysis culture system demonstrated the feasibility of cost-effective high-density hepatic differentiation with minimum growth factor usage.

Advances in Neural Stem Cell Therapy for Spinal Cord Injury: Safety, Efficacy, and Future Perspectives

Spinal cord injury (SCI) is a devastating central nervous system injury that leads to severe disabilities in motor and sensory functions, causing significant deterioration in patients' quality of life. Owing to the complexity of SCI pathophysiology, there has been no effective treatment for reversing neural tissue damage and recovering neurological functions. Several novel therapies targeting different stages of pathophysiological mechanisms of SCI have been developed. Among these, treatments using stem cells have great potential for the regeneration of damaged neural tissues. In this review, we have summarized recent preclinical and clinical studies focusing on neural stem cells (NSCs). NSCs are multipotent cells with specific differentiation capabilities for neural lineage. Several preclinical studies have demonstrated the regenerative effects of transplanted NSCs in SCI animal models through both paracrine effects and direct neuronal differentiation, restoring synaptic connectivity and neural networks. Based on the positive results of several preclinical studies, phase I and II clinical trials using NSCs have been performed. Despite several hurdles and issues that need to be addressed in the clinical use of NSCs in patients with SCI, gradual progress in the technical development and therapeutic efficacy of NSCs treatments has enhanced the prospects for cell-based treatments in SCI.

In Vitro Modeling of the Blood–Brain Barrier for the Study of Physiological Conditions and Alzheimer’s Disease

The blood–brain barrier (BBB) is an essential structure for the maintenance of brain homeostasis. Alterations to the BBB are linked with a myriad of pathological conditions and play a significant role in the onset and evolution of neurodegenerative diseases, including Alzheimer’s disease. Thus, a deeper understanding of the BBB’s structure and function is mandatory for a better knowledge of neurodegenerative disorders and the development of effective therapies. Because studying the BBB in vivo imposes overwhelming difficulties, the in vitro approach remains the main possible way of research. With many in vitro BBB models having been developed over the last years, the main aim of this review is to systematically present the most relevant designs used in neurological research. In the first part of the article, the physiological and structural–functional parameters of the human BBB are detailed. Subsequently, available BBB models are presented in a comparative approach, highlighting their advantages and limitations. Finally, the new perspectives related to the study of Alzheimer’s disease with the help of novel devices that mimic the in vivo human BBB milieu gives the paper significant originality.

Human mesenchymal amniotic fluid stem cells reveal an unexpected neuronal potential differentiating into functional spinal motor neurons

Human amniotic fluids stem cells (hAFSCs) can be easily isolated from the amniotic fluid during routinely scheduled amniocentesis. Unlike hiPSCs or hESC, they are neither tumorigenic nor immunogenic and their use does not rise ethical or safety issues: for these reasons they may represent a good candidate for the regenerative medicine. hAFSCs are generally considered multipotent and committed towards the mesodermal lineages; however, they express many pluripotent markers and share some epigenetic features with hiPSCs. Hence, we hypothesized that hAFSCs may overcome their mesodermal commitment differentiating into to ectodermal lineages. Here we demonstrated that by the sequential exposure to specific factors, hAFSCs can give rise to spinal motor neurons (MNs), as evidenced by the gradual gene and protein upregulation of early and late MN markers (PAX6, ISL1, HB9, NF-L, vAChT). When co-cultured with myotubes, hAFSCs-derived MNs were able to create functional neuromuscular junctions that induced robust skeletal muscle contractions. These data demonstrated the hAFSCs are not restricted to mesodermal commitment and can generate functional MNs thus outlining an ethically acceptable strategy for the study and treatment of the neurodegenerative diseases.

Divergence between Neuronal and Oligodendroglial Cell Fate, in Postnatal Brain Neural Stem Cells, Leads to Divergent Properties in Polymorphic In Vitro Assays

Two main stem cell pools exist in the postnatal mammalian brain that, although they share some “stemness” properties, also exhibit significant differences. Multipotent neural stem cells survive within specialized microenvironments, called niches, and they are vulnerable to ageing. Oligodendroglial lineage-restricted progenitor cells are widely distributed in the brain parenchyma and are more resistant to the effects of ageing. Here, we create polymorphic neural stem cell cultures and allow cells to progress towards the neuronal and the oligodendroglial lineage. We show that the divergence of cell fate is accompanied by a divergence in the properties of progenitors, which reflects their adaptation to life in the niche or the parenchyma. Neurogenesis shows significant spatial restrictions and a dependence on laminin, a major niche component, while oligodendrogenesis shows none of these constraints. Furthermore, the blocking of integrin-β1 leads to opposing effects, reducing neurogenesis and enhancing oligodendrogenesis. Therefore, polymorphic neural stem cell assays can be used to investigate the divergence of postnatal brain stem cells and also to predict the in vivo effects of potential therapeutic molecules targeting stem and progenitor cells, as we do for the microneurotrophin BNN-20.

Generation of Human iPSC-Derived Astrocytes with a mature star-shaped phenotype for CNS modeling

The generation of astrocytes from human induced pluripotent stem cells has been hampered by either prolonged differentiation—spanning over two months—or by shorter protocols that generate immature astrocytes, devoid of salient mature astrocytic traits pivotal for central nervous system (CNS) modeling. We directed stable hiPSC-derived neuroepithelial stem cells to human iPSC-derived Astrocytes (hiAstrocytes) with a high percentage of star-shaped cells by orchestrating an astrocytic-tuned culturing environment in 28 days. We employed RT-qPCR and ICC to validate the astrocytic commitment of the neuroepithelial stem cells. To evaluate the inflammatory phenotype, we challenged the hiAstrocytes with the pro-inflammatory cytokine IL-1β (interleukin 1 beta) and quantitatively assessed the secretion profile of astrocyte-associated cytokines and the expression of intercellular adhesion molecule 1 (ICAM-1). Finally, we quantitatively assessed the capacity of hiAstrocytes to synthesize and export the antioxidant glutathione. In under 28 days, the generated cells express canonical and mature astrocytic markers, denoted by the expression of GFAP, AQP4 and ALDH1L1. In addition, the notion of a mature phenotype is reinforced by the expression of both astrocytic glutamate transporters EAAT1 and EAAT2. Thus, hiAstrocytes have a mature phenotype that encompasses traits critical in CNS modeling, including glutathione synthesis and secretion, upregulation of ICAM-1 and a cytokine secretion profile on a par with human fetal astrocytes. This protocol generates a multifaceted astrocytic model suitable for in vitro CNS disease modeling and personalized medicine.

Advances in Recapitulating Alzheimer's Disease Phenotypes Using Human Induced Pluripotent Stem Cell-Based In Vitro Models

Alzheimer's disease (AD) is an incurable neurodegenerative disorder and the leading cause of death among older individuals. Available treatment strategies only temporarily mitigate symptoms without modifying disease progression. Recent studies revealed the multifaceted neurobiology of AD and shifted the target of drug development. Established animal models of AD are mostly tailored to yield a subset of disease phenotypes, which do not recapitulate the complexity of sporadic late-onset AD, the most common form of the disease. The use of human induced pluripotent stem cells (HiPSCs) offers unique opportunities to fill these gaps. Emerging technology allows the development of disease models that recapitulate a brain-like microenvironment using patient-derived cells. These models retain the individual's unraveled genetic background, yielding clinically relevant disease phenotypes and enabling cost-effective, high-throughput studies for drug discovery. Here, we review the development of various HiPSC-based models to study AD mechanisms and their application in drug discovery.

'Channeling' therapeutic discovery for epileptic encephalopathy through iPSC technologies

Induced pluripotent stem cell (iPSC) and gene editing technologies have revolutionized the field of in vitro disease modeling, granting us access to disease-pertinent human cells of the central nervous system. These technologies are particularly well suited for the study of diseases with strong monogenic etiologies. Epilepsy is one of the most common neurological disorders in children, with approximately half of all genetic cases caused by mutations in ion channel genes. These channelopathy-associated epilepsies are clinically diverse, mechanistically complex, and hard to treat. Here, we review the genetic links to epilepsy, the opportunities and challenges of iPSC-based approaches for developing in vitro models of channelopathy-associated disorders, the available tools for effective phenotyping of iPSC-derived neurons, and discuss the potential therapeutic approaches for these devastating diseases.

Controlling neural territory patterning from pluripotency using a systems developmental biology approach

Successful manufacture of specialized human cells requires process understanding of directed differentiation. Here, we apply high-dimensional Design of Experiments (HD-DoE) methodology to identify critical process parameters (CPPs) that govern neural territory patterning from pluripotency—the first stage toward specification of central nervous system (CNS) cell fates. Using computerized experimental design, 7 developmental signaling pathways were simultaneously perturbed in human pluripotent stem cell culture. Regionally specific genes spanning the anterior-posterior and dorsal-ventral axes of the developing embryo were measured after 3 days and mathematical models describing pathway control were developed using regression analysis. High-dimensional models revealed particular combinations of signaling inputs that induce expression profiles consistent with emerging CNS territories and defined CPPs for anterior and posterior neuroectoderm patterning. The results demonstrate the importance of combinatorial control during neural induction and challenge the use of generic neural induction strategies such as dual-SMAD inhibition, when seeking to specify particular lineages from pluripotency.

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Mathematical models describe pathway control of neuroectoderm marker expression

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Stage 1 media conditions optimized for regionally specific neuroectoderm in 3 days

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Optimized conditions are more consistent than dual-SMADi across hiPSC lines

Nanoarchitectonics of a Microsphere-Based Scaffold for Modeling Neurodevelopment and Neurological Disease

Three-dimensional cellular constructs derived from pluripotent stem cells allow the ex vivo study of neurodevelopment and neurological disease within a spatially organized model. However, the robustness and utility of three-dimensional models is impacted by tissue self-organization, size limitations, nutrient supply, and heterogeneity. In this work, we have utilized the principles of nanoarchitectonics to create a multifunctional polymer/bioceramic composite microsphere system for stem cell culture and differentiation in a chemically defined microenvironment. Microspheres could be customized to produce three-dimensional structures of defined size (ranging from >100 to <350 μm) with lower mechanical properties compared with a thin film. Furthermore, the microspheres softened in solution, approaching more tissue-like mechanical properties over time. With neural stem cells (NSCs) derived from human induced pluripotent stem cells, microsphere-cultured NSCs were able to utilize multiple substrates to promote cell adhesion and proliferation. Prolonged culture of NSC-bound microspheres under differentiating conditions allowed the formation of both neural and glial cell types from control and patient-derived stem cell models. Human NSCs and differentiated neurons could also be cocultured with astrocytes and human umbilical vein endothelial cells, demonstrating application for tissue-engineered modeling of development and human disease. We further demonstrated that microspheres allow the loading and sustained release of multiple recombinant proteins to support cellular maintenance and differentiation. While previous work has principally utilized self-organizing models or protein-rich hydrogels for neural culture, the three-dimensional matrix developed here through nanoarchitectonics represents a chemically defined and robust alternative for the in vitro study of neurodevelopment and nervous system disorders.

Transplanted neural lineage cells derived from dental pulp stem cells promote peripheral nerve regeneration

Cell therapy for peripheral nerve injury is a promising strategy as regenerative medicine that restores neurological function. However, challenges remain in producing suitable and sufficient amounts of autologous cells for promoting nerve regeneration. This study aimed to identify the characteristics of neural lineage cells (NLCs) differentiated from dental pulp stem cells (DPSCs) and reveal their effect on functional recovery and nerve regeneration after cell transplantation into an immunodeficient rat using a nerve guide conduit. Here we report a protocol of neural induction in monolayer culture and characterize NLCs in vitro. Furthermore, NLCs were transplanted into an immunodeficient rat model with a 10-mm sciatic nerve defect, and cell survival and differentiation were investigated in vivo. Outcomes of nerve regeneration were also assessed using the remyelinated axon numbers, myelin sheath thickness, electrophysiological activities, and gastrocnemius muscle mass. NLCs comprised neuronal, astrocyte, oligodendrocyte, and neural crest lineage cells. NLCs enhanced the activities of endothelial cells, Schwann cells, and neurons in a paracrine-dependent manner in vitro. At 2 weeks post-transplantation, numerous transplanted NLCs differentiated into platelet-derived growth factor receptor alpha (PDGFRα) + oligodendrocyte progenitor cells (OPCs) and a few PDGFRα + /p75 neurotrophin receptor + Schwann cell-like cells derived from OPCs were observed. At 12 weeks post-transplantation, human Schwann cell-like cells survived, and axon growth, remyelination, electrophysiological activities, and muscle atrophy were improved. This study demonstrates the broad application of our protocol of neural induction of DPSCs and portrays the efficacy of transplantation of NLCs derived from human DPSCs as a promising strategy for peripheral nerve regeneration.

IPSC-Derived Human Neurons with GCaMP6s Expression Allow In Vitro Study of Neurophysiological Responses to Neurochemicals

The study of human neurons and their interaction with neurochemicals is difficult due to the inability to collect primary biomaterial. However, recent advances in the cultivation of human stem cells, methods for their neuronal differentiation and chimeric fluorescent calcium indicators have allowed the creation of model systems in vitro. In this paper we report on the development of a method to obtain human neurons with the GCaMP6s calcium indicator, based on a human iPSC line with the TetON–NGN2 transgene complex. The protocol we developed allows us quickly, conveniently and efficiently obtain significant amounts of human neurons suitable for the study of various neurochemicals and their effects on specific neurophysiological activity, which can be easily registered using fluorescence microscopy. In the neurons we obtained, glutamate (Glu) induces rises in [Ca²⁺]_i which are caused by ionotropic receptors for Glu, predominantly of the NMDA-type. Taken together, these facts allow us to consider the model we have created to be a useful and successful development of this technology.

Neuronal cell-based medicines from pluripotent stem cells: Development, production, and preclinical assessment

Brain degeneration and damage is difficult to cure due to the limited endogenous repair capability of the central nervous system. Furthermore, drug development for treatment of diseases of the central nervous system remains a major challenge. However, it now appears that using human pluripotent stem cell-derived neural cells to replace degenerating cells provides a promising cell-based medicine for rejuvenation of brain function. Accordingly, a large number of studies have carried out preclinical assessments, which have involved different neural cell types in several neurological diseases. Recent advances in animal models identify the transplantation of neural derivatives from pluripotent stem cells as a promising path toward the clinical application of cell therapies [Stem Cells Transl Med 2019;8:681-693; Drug Discov Today 2019;24:992-999; Nat Med 2019;25:1045-1053]. Some groups are moving toward clinical testing in humans. However, the difficulty in selection of valuable critical quality criteria for cell products and the lack of functional assays that could indicate suitability for clinical effect continue to hinder neural cell-based medicine development [Biologicals 2019;59:68-71]. In this review, we summarize the current status of preclinical studies progress in this area and outline the biological characteristics of neural cells that have been used in new developing clinical studies. We also discuss the requirements for translation of stem cell-derived neural cells in examples of stem cell-based clinical therapy.

Brain Organoids: Filling the Need for a Human Model of Neurological Disorder

Neurological disorders are among the leading causes of death worldwide, accounting for almost all onsets of dementia in the elderly, and are known to negatively affect motor ability, mental and cognitive performance, as well as overall wellbeing and happiness. Currently, most neurological disorders go untreated due to a lack of viable treatment options. The reason for this lack of options is s poor understanding of the disorders, primarily due to research models that do not translate well into the human in vivo system. Current models for researching neurological disorders, neurodevelopment, and drug interactions in the central nervous system include in vitro monolayer cell cultures, and in vivo animal models. These models have shortcomings when it comes to translating research about disorder pathology, development, and treatment to humans. Brain organoids are three-dimensional (3D) cultures of stem cell-derived neural cells that mimic the development of the in vivo human brain with high degrees of accuracy. Researchers have started developing these miniature brains to model neurodevelopment, and neuropathology. Brain organoids have been used to model a wide range of neurological disorders, including the complex and poorly understood neurodevelopmental and neurodegenerative disorders. In this review, we discuss the brain organoid technology, placing special focus on the different brain organoid models that have been developed, discussing their strengths, weaknesses, and uses in neurological disease modeling.

Effect of Electrical Stimulation Conditions on Neural Stem Cells Differentiation on Cross-Linked PEDOT:PSS Films

The ability to culture and differentiate neural stem cells (NSCs) to generate functional neural populations is attracting increasing attention due to its potential to enable cell-therapies to treat neurodegenerative diseases. Recent studies have shown that electrical stimulation improves neuronal differentiation of stem cells populations, highlighting the importance of the development of electroconductive biocompatible materials for NSC culture and differentiation for tissue engineering and regenerative medicine. Here, we report the use of the conjugated polymer poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS CLEVIOS P AI 4083) for the manufacture of conductive substrates. Two different protocols, using different cross-linkers (3-glycidyloxypropyl)trimethoxysilane (GOPS) and divinyl sulfone (DVS) were tested to enhance their stability in aqueous environments. Both cross-linking treatments influence PEDOT:PSS properties, namely conductivity and contact angle. However, only GOPS-cross-linked films demonstrated to maintain conductivity and thickness during their incubation in water for 15 days. GOPS-cross-linked films were used to culture ReNcell-VM under different electrical stimulation conditions (AC, DC, and pulsed DC electrical fields). The polymeric substrate exhibits adequate physicochemical properties to promote cell adhesion and growth, as assessed by Alamar Blue® assay, both with and without the application of electric fields. NSCs differentiation was studied by immunofluorescence and quantitative real-time polymerase chain reaction. This study demonstrates that the pulsed DC stimulation (1 V/cm for 12 days), is the most efficient at enhancing the differentiation of NSCs into neurons.