Large-scale generation of human iPSC-derived neural stem cells/early neural progenitor cells and their neuronal differentiation

Anti-herpetic tau preserves neurons via the cGAS-STING-TBK1 pathway in Alzheimer's disease

Alzheimer's disease (AD) diagnosis relies on the presence of extracellular β-amyloid (Aβ) and intracellular hyperphosphorylated tau (p-tau). Emerging evidence suggests a potential link between AD pathologies and infectious agents, with herpes simplex virus 1 (HSV-1) being a leading candidate. Our investigation, using metagenomics, mass spectrometry, western blotting, and decrowding expansion pathology, detects HSV-1-associated proteins in human brain samples. Expression of the herpesvirus protein ICP27 increases with AD severity and strongly colocalizes with p-tau but not with Aβ. Modeling in human brain organoids shows that HSV-1 infection elevates tau phosphorylation. Notably, p-tau reduces ICP27 expression and markedly decreases post-infection neuronal death from 64% to 7%. This modeling prompts investigation into the cGAS-STING-TBK1 pathway products, nuclear factor (NF)-κB and IRF-3, which colocalizes with ICP27 and p-tau in AD. Furthermore, experimental activation of STING enhances tau phosphorylation, while TBK1 inhibition prevents it. Together, these findings suggest that tau phosphorylation acts as an innate immune response in AD, driven by cGAS-STING.

Cell culture research in aging and Alzheimer's disease: The strategic use/reuse of untreated controls and savings people's tax dollars

Cell culture is an essential tool in both fundamental and translational research, particularly for understanding complex diseases like Alzheimer's disease (AD). The use of cell lines provides the advantage of genetic homogeneity, ensuring reproducible and consistent results. This article explores the application of mammalian cell cultures to model AD, focusing on the transfection of cells with key genes associated with the disease to replicate the cellular environment of AD. It explains various transfection methods and challenges related to the process. These models offer a robust platform for investigating cellular biology, molecular pathways, physiological processes, and drug discovery efforts. A range of assays, including RT-PCR, western blotting, ELISA, mitochondrial respiration, and reactive oxygen species analysis, are employed to assess the impact of genetic modifications on cellular functions and to screen potential AD therapies. Researchers often design experiments with multiple variables such as genetic modifications, chemical treatments, or time points, paired with positive and negative controls. By using a consistent control group across all conditions and under identical experimental conditions, researchers can minimize variability and enhance data reproducibility. This approach is particularly valuable in AD research, where small experimental differences can significantly influence outcomes. Using a shared control group ensures data comparability across experiments, saving time and resources by eliminating redundant control tests. This strategy not only streamlines the research process but also improves the reliability of results, making it a sensible, resource-efficient method that ultimately conserves public funding in the pursuit of AD treatments.

Evaluating chemical effects on human neural cells through calcium imaging and deep learning

New substances intended for human consumption must undergo extensive preclinical safety pharmacology testing prior to approval. These tests encompass the evaluation of effects on the central nervous system, which is highly sensitive to chemical substances. With the growing understanding of the species-specific characteristics of human neural cells and advancements in machine learning technology, the development of effective and efficient methods for the initial screening of chemical effects on human neural function using machine learning platforms is anticipated. In this study, we employed a deep learning model to analyze calcium dynamics in human-induced pluripotent stem cell-derived neural progenitor cells, which were exposed to various concentrations of four representative chemicals. We report that this approach offers a reliable and concise method for quantitatively classifying the effects of chemical exposures and predicting potential harm to human neural cells.

Potential of Stem-Cell-Induced Peripheral Nerve Regeneration: From Animal Models to Clinical Trials

Peripheral nerve injury has become an increasingly prevalent clinical concern, causing great morbidity in the community. Although there have been significant advancements in the treatment of peripheral nerve damage in recent years, the issue of long-term nerve regeneration remains. Furthermore, Wallerian degeneration has created an obstacle to long-term nerve regeneration. For this reason, there has been extensive research on the use of exogenous and endogenous stem cells as an adjunct or even primary treatment option for peripheral nerve injury. The plasticity and inducibility of stem cells make them an enticing option for initiating neuronal cell regrowth and optimal sensory and functional nerve regeneration. Peripheral nerve injury has a broad range of causative factors and etiologies. As such, unique stem cell-induced peripheral nerve treatments are being investigated to ameliorate the damage incited by all causes, including trauma, neuropathy, and systemic neurodegenerative diseases. This review is oriented to outline the potential role of stem cell therapies in peripheral nerve injury versus the current standards of care, compare the benefits and drawbacks of specific stem cell lines under investigation, and highlight the current models of stem cell therapy in the peripheral nervous system, with the ultimate goal of narrowing down and optimizing the role and scope of stem cell therapy in peripheral nerve injury.

Characterization of neural infection by Oropouche orthobunyavirus

Oropouche fever is a re-emerging global viral threat caused by infection with Oropouche orthobunyavirus (OROV). While disease is generally self-limiting, historical and recent reports of neurologic involvement highlight the importance of understanding the neuropathogenesis of OROV. In this study, we characterize viral replication kinetics in neurons and microglia derived from immortalized, primary, and induced pluripotent stem cell-derived cells, which are all permissive to infection. We demonstrate that ex vivo rat brain slice cultures can be infected by OROV and produce antiviral cytokines and chemokines, including IL-6, TNF-α and IFN-β, which introduces an additional model to study viral kinetics in the central nervous system. These findings provide additional insight into OROV neuropathogenesis and in vitro modeling strategies for a newly re-emerging arbovirus.

Zika virus vertical transmission induces neuroinflammation and synapse impairment in brain cells derived from children born with Congenital Zika Syndrome

Zika virus (ZIKV) infection was first reported in 2015 in Brazil as causing microcephaly and other developmental abnormalities in newborns, leading to the identification of Congenital Zika Syndrome (CZS). Viral infections have been considered an environmental risk factor for neurodevelopmental disorders outcome, such as Autism Spectrum Disorder (ASD). Moreover, not only the infection per se, but maternal immune system activation during pregnancy, has been linked to fetal neurodevelopmental disorders. To understand the impact of ZIKV vertical infection on brain development, we derived induced pluripotent stem cells (iPSC) from Brazilian children born with CZS, some of the patients also being diagnosed with ASD. Comparing iPSC-derived neurons from CZS with a control group, we found lower levels of pre- and postsynaptic proteins and reduced functional synapses by puncta co-localization. Furthermore, neurons and astrocytes derived from the CZS group showed decreased glutamate levels. Additionally, the CZS group exhibited elevated levels of cytokine production, one of which being IL-6, already associated with the ASD phenotype. These preliminary findings suggest that ZIKV vertical infection may cause long-lasting disruptions in brain development during fetal stages, even in the absence of the virus after birth. These disruptions could contribute to neurodevelopmental disorders manifestations such as ASD. Our study contributes with novel knowledge of the CZS outcomes and paves the way for clinical validation and the development of potential interventions to mitigate the impact of ZIKV vertical infection on neurodevelopment.

The roles of neural stem cells in myelin regeneration and repair therapy after spinal cord injury

Spinal cord injury (SCI) is a complex tissue injury that results in a wide range of physical deficits, including permanent or progressive disabilities of sensory, motor and autonomic functions. To date, limitations in current clinical treatment options can leave SCI patients with lifelong disabilities. There is an urgent need to develop new therapies for reconstructing the damaged spinal cord neuron-glia network and restoring connectivity with the supraspinal pathways. Neural stem cells (NSCs) possess the ability to self-renew and differentiate into neurons and neuroglia, including oligodendrocytes, which are cells responsible for the formation and maintenance of the myelin sheath and the regeneration of demyelinated axons. For these properties, NSCs are considered to be a promising cell source for rebuilding damaged neural circuits and promoting myelin regeneration. Over the past decade, transplantation of NSCs has been extensively tested in a variety of preclinical models of SCI. This review aims to highlight the pathophysiology of SCI and promote the understanding of the role of NSCs in SCI repair therapy and the current advances in pathological mechanism, pre-clinical studies, as well as clinical trials of SCI via NSC transplantation therapeutic strategy. Understanding and mastering these frontier updates will pave the way for establishing novel therapeutic strategies to improve the quality of recovery from SCI.

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.

Generation of induced pluripotent stem cells from rat fibroblasts and optimization of its differentiation into mature functional neurons

BACKGROUND

Induced pluripotent stem cells (iPSCs) derived neural stem cells (NSCs) provide a potential for autologous neural transplantation therapy following neurological insults. Thus far, in preclinical studies the donor iPSCs-NSCs are mostly of human or mouse origin with concerns centering around graft rejection when applied to rat brain injury models. For better survival and integration of transplanted cells in the injured brain in rat models, use of rat-iPSC-NSCs and in combination with biomaterials is of advantageous. Herein, we report a detailed method in generating rat iPSCs with improved reprogramming efficiency and differentiation into neurons.

NEW METHOD

Rat fibroblasts were reprogrammed into iPSCs with polybrene and EF1α-STEMCCA-LoxP lentivirus vector. Pluripotency characterization, differentiation into neuronal linage cells were assessed with RT-qPCR, Western blotting, immunostaining and patch-clamp methods. Cells were cultured in a custom-designed integrin array system as well as in a hydrogel-based 3D condition.

RESULTS

We describe a thorough method for the generation of rat-iPSC-NSCs, and identify integrin αvβ8 as a substrate for the optimal growth of rat-iPSC-NSCs. Furthermore, with hydrogel as the supporting biomaterial in the 3-D culture, when combined with integrin αvβ8 binding peptide, it forms a conducive environment for optimal growth and differentiation of iPSC-NSCs into mature neurons.

COMPARISON WITH EXISTING METHODS

Published studies about rat-iPSC-NSCs are rare. This study provides a detailed protocol for the generation of rat iPSC-NSCs and optimal growth conditions for neuronal differentiation. Our method is useable for studies to assess the utility of rat iPSC-NSCs for neural transplantation in rat brain injury models.

Extracellular vesicles as nanotheranostic platforms for targeted neurological disorder interventions

Central Nervous System (CNS) disorders represent a profound public health challenge that affects millions of people around the world. Diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and traumatic brain injury (TBI) exemplify the complexities and diversities that complicate their early detection and the development of effective treatments. Amid these challenges, the emergence of nanotechnology and extracellular vesicles (EVs) signals a new dawn for treating and diagnosing CNS ailments. EVs are cellularly derived lipid bilayer nanosized particles that are pivotal in intercellular communication within the CNS and have the potential to revolutionize targeted therapeutic delivery and the identification of novel biomarkers. Integrating EVs with nanotechnology amplifies their diagnostic and therapeutic capabilities, opening new avenues for managing CNS diseases. This review focuses on examining the fascinating interplay between EVs and nanotechnology in CNS theranostics. Through highlighting the remarkable advancements and unique methodologies, we aim to offer valuable perspectives on how these approaches can bring about a revolutionary change in disease management. The objective is to harness the distinctive attributes of EVs and nanotechnology to forge personalized, efficient interventions for CNS disorders, thereby providing a beacon of hope for affected individuals. In short, the confluence of EVs and nanotechnology heralds a promising frontier for targeted and impactful treatments against CNS diseases, which continue to pose significant public health challenges. By focusing on personalized and powerful diagnostic and therapeutic methods, we might improve the quality of patients.

The hope, hype and obstacles surrounding cell therapy

Cell therapy offers hope, but it also presents challenges, most particularly the limited ability of human organs and tissues to regenerate. Since many diseases are associated with irreversible pathophysiological or traumatic changes, stem cells and their derivatives are unable to secure healing. Although regenerative medicine offers chances for improvements in many diseases, such as type one diabetes and Parkinson's disease, it cannot eliminate the primary cause of many of them. While successes can be expected for diseases such as sickle cell disease, this is not the case for hereditary diseases with varied mutation types or for ciliopathies, which start in embryogenesis. In this complicated medical environment, synthetic biology offers some solutions, but their implementation will take many years. Still, positive examples such as CAR-T therapy offer hope.

Therapeutic role of neural stem cells in neurological diseases

The failure of endogenous repair is the main feature of neurological diseases that cannot recover the damaged tissue and the resulting dysfunction. Currently, the range of treatment options for neurological diseases is limited, and the approved drugs are used to treat neurological diseases, but the therapeutic effect is still not ideal. In recent years, different studies have revealed that neural stem cells (NSCs) have made exciting achievements in the treatment of neurological diseases. NSCs have the potential of self-renewal and differentiation, which shows great foreground as the replacement therapy of endogenous cells in neurological diseases, which broadens a new way of cell therapy. The biological functions of NSCs in the repair of nerve injury include neuroprotection, promoting axonal regeneration and remyelination, secretion of neurotrophic factors, immune regulation, and improve the inflammatory microenvironment of nerve injury. All these reveal that NSCs play an important role in improving the progression of neurological diseases. Therefore, it is of great significance to better understand the functional role of NSCs in the treatment of neurological diseases. In view of this, we comprehensively discussed the application and value of NSCs in neurological diseases as well as the existing problems and challenges.

Potential therapeutic effect of olfactory ensheathing cells in neurological diseases: neurodegenerative diseases and peripheral nerve injuries

Neurological diseases are destructive, mainly characterized by the failure of endogenous repair, the inability to recover tissue damage, resulting in the increasing loss of cognitive and physical function. Although some clinical drugs can alleviate the progression of these diseases, but they lack therapeutic effect in repairing tissue injury and rebuilding neurological function. More and more studies have shown that cell therapy has made good achievements in the application of nerve injury. Olfactory ensheathing cells (OECs) are a special type of glial cells, which have been proved to play an important role as an alternative therapy for neurological diseases, opening up a new way for the treatment of neurological problems. The functional mechanisms of OECs in the treatment of neurological diseases include neuroprotection, immune regulation, axon regeneration, improvement of nerve injury microenvironment and myelin regeneration, which also include secreted bioactive factors. Therefore, it is of great significance to better understand the mechanism of OECs promoting functional improvement, and to recognize the implementation of these treatments and the effective simulation of nerve injury disorders. In this review, we discuss the function of OECs and their application value in the treatment of neurological diseases, and position OECs as a potential candidate strategy for the treatment of nervous system diseases.

Targeting and eradicating latent CNS reservoirs of HIV-1: original strategies and new models

Nowadays, combination antiretroviral therapy (cART) is the standard treatment for all people with human immunodeficiency virus (HIV-1). Although cART is effective in treating productive infection, it does not eliminate latent reservoirs of the virus. This leads to lifelong treatment associated with the occurrence of side effects and the development of drug-resistant HIV-1. Suppression of viral latency is therefore the major hurdle to HIV-1 eradication. Multiple mechanisms exist to regulate viral gene expression and drive the transcriptional and post-transcriptional establishment of latency. Epigenetic processes are amongst the most studied mechanisms influencing both productive and latent infection states. The central nervous system (CNS) represents a key anatomical sanctuary for HIV and is the focal point of considerable research efforts. However, limited and difficult access to CNS compartments makes understanding the HIV-1 infection state in latent brain cells such as microglial cells, astrocytes, and perivascular macrophages challenging. This review examines the latest advances on epigenetic transformations involved in CNS viral latency and targeting of brain reservoirs. Evidence from clinical studies as well as in vivo and in vitro models of HIV-1 persistence in the CNS will be discussed, with a special focus on recent 3D in vitro models such as human brain organoids. Finally, the review will address therapeutic considerations for targeting latent CNS reservoirs.

Potency assays and biomarkers for cell-based advanced therapy medicinal products

Advanced Therapy Medicinal Products (ATMPs) based on somatic cells expanded in vitro, with or without genetic modification, is a rapidly growing area of drug development, even more so following the marketing approval of several such products. ATMPs are produced according to Good Manufacturing Practice (GMP) in authorized laboratories. Potency assays are a fundamental aspect of the quality control of the end cell products and ideally could become useful biomarkers of efficacy in vivo. Here we summarize the state of the art with regard to potency assays used for the assessment of the quality of the major ATMPs used clinic settings. We also review the data available on biomarkers that may substitute more complex functional potency tests and predict the efficacy in vivo of these cell-based drugs.

A novel NMDA receptor test model based on hiPSC-derived neural cells

N-Methyl-D-aspartate receptors (NMDARs) are central for learning and information processing in the brain. Dysfunction of NMDARs can play a key role in the pathogenesis of neurodegeneration and drug addiction. The development of selective NMDAR modulators represents a promising strategy to target these diseases. Among such modulating compounds are ifenprodil and its 3-benzazepine derivatives. Classically, the effects of these NMDAR modulators have been tested by techniques like two-electrode voltage clamp (TEVC), patch clamp, or fluorescence-based assays. However, testing their functional effects in complex human systems requires more advanced approaches. Here, we established a human induced pluripotent stem cell-derived (hiPSC-derived) neural cell system and proved its eligibility as a test system for investigating NMDAR modulators and pharmaceutical effects on human neurons.

iPSC-Derived Neurons from Patients with POLG Mutations Exhibit Decreased Mitochondrial Content and Dendrite Simplification

Mutations in POLG, the gene encoding the catalytic subunit of DNA polymerase gamma, result in clinical syndromes characterized by mitochondrial DNA (mtDNA) depletion in affected tissues with variable organ involvement. The brain is one of the most affected organs, and symptoms include intractable seizures, developmental delay, dementia, and ataxia. Patient-derived induced pluripotent stem cells (iPSCs) provide opportunities to explore mechanisms in affected cell types and potential therapeutic strategies. Fibroblasts from two patients were reprogrammed to create new iPSC models of POLG-related mitochondrial diseases. Compared with iPSC-derived control neurons, mtDNA depletion was observed upon differentiation of the POLG-mutated lines to cortical neurons. POLG-mutated neurons exhibited neurite simplification with decreased mitochondrial content, abnormal mitochondrial structure and function, and increased cell death. Expression of the mitochondrial kinase PTEN-induced kinase 1 (PINK1) mRNA was decreased in patient neurons. Overexpression of PINK1 increased mitochondrial content and ATP:ADP ratios in neurites, decreasing cell death and rescuing neuritic complexity. These data indicate an intersection of polymerase gamma and PINK1 pathways that may offer a novel therapeutic option for patients affected by this spectrum of disorders.

Differentiation of human induced pluripotent stem cells into cortical neural stem cells

Efficient and effective methods for converting human induced pluripotent stem cells into differentiated derivatives are critical for performing robust, large-scale studies of development and disease modelling, and for providing a source of cells for regenerative medicine. Here, we describe a 14-day neural differentiation protocol which allows for the scalable, simultaneous differentiation of multiple iPSC lines into cortical neural stem cells We currently employ this protocol to differentiate and compare sets of engineered iPSC lines carrying loss of function alleles in developmental disorder associated genes, alongside isogenic wildtype controls. Using RNA sequencing (RNA-Seq), we can examine the changes in gene expression brought about by each disease gene knockout, to determine its impact on neural development and explore mechanisms of disease. The 10-day Neural Induction period uses the well established dual-SMAD inhibition approach combined with Wnt/β-Catenin inhibition to selectively induce formation of cortical NSCs. This is followed by a 4-day Neural Maintenance period facilitating NSC expansion and rosette formation, and NSC cryopreservation. We also describe methods for thawing and passaging the cryopreserved NSCs, which are useful in confirming their viability for further culture. Routine implementation of immunocytochemistry Quality Control confirms the presence of PAX6-positive and/or FOXG1-positive NSCs and the absence of OCT4-positive iPSCs after differentiation. RNA-Seq, flow cytometry, immunocytochemistry (ICC) and RT-qPCR provide additional confirmation of robust presence of NSC markers in the differentiated cells. The broader utility and application of our protocol is demonstrated by the successful differentiation of wildtype iPSC lines from five additional independent donors. This paper thereby describes an efficient method for the production of large numbers of high purity cortical NSCs, which are widely applicable for downstream research into developmental mechanisms, further differentiation into postmitotic cortical neurons, or other applications such as large-scale drug screening experiments.

Pathophysiology of Spinal Cord Injury and Tissue Engineering Approach for Its Neuronal Regeneration: Current Status and Future Prospects

A spinal cord injury (SCI) is a very debilitating condition causing loss of sensory and motor function as well as multiple organ failures. Current therapeutic options like surgery and pharmacotherapy show positive results but are incapable of providing a complete cure for chronic SCI symptoms. Tissue engineering, including neuroprotective or growth factors, stem cells, and biomaterial scaffolds, grabs attention because of their potential for regeneration and ability to bridge the gap in the injured spinal cord (SC). Preclinical studies with tissue engineering showed functional recovery and neurorestorative effects. Few clinical trials show the safety and efficacy of the tissue engineering approach. However, more studies should be carried out for potential treatment modalities. In this review, we summarize the pathophysiology of SCI and its current treatment modalities, including surgical, pharmacological, and tissue engineering approaches following SCI in preclinical and clinical phases.

Variations in Aspects of Neural Precursor Cell Neurogenesis in a Human Model of HSV-1 Infection

Encephalitis, the most significant of the central nervous system (CNS) diseases caused by Herpes simplex virus 1 (HSV-1), may have long-term sequelae in survivors treated with acyclovir, the cause of which is unclear. HSV-1 exhibits a tropism toward neurogenic niches in CNS enriched with neural precursor cells (NPCs), which play a pivotal role in neurogenesis. NPCs are susceptible to HSV-1. There is a paucity of information regarding the influence of HSV-1 on neurogenesis in humans. We investigated HSV-1 infection of NPCs from two individuals. Our results show (i) HSV-1 impairs, to different extents, the proliferation, self-renewing, and, to an even greater extent, migration of NPCs from these two subjects; (ii) The protective effect of the gold-standard antiherpetic drug acyclovir (ACV) varies with viral dose and is incomplete. It is also subject to differences in terms of efficacy of the NPCs derived from these two individuals. These results suggest that the effects of HSV-1 may have on aspects of NPC neurogenesis may vary among individuals, even in the presence of acyclovir, and this may contribute to the heterogeneity of cognitive sequelae across encephalitis survivors. Further analysis of NPC cell lines from a larger number of individuals is warranted.

Vesicular Glutamate Release from Feeder-FreehiPSC-Derived Neurons

Human-induced pluripotent stem cells (hiPSCs) represent one of the main and powerful tools for the in vitro modeling of neurological diseases. Standard hiPSC-based protocols make use of animal-derived feeder systems to better support the neuronal differentiation process. Despite their efficiency, such protocols may not be appropriate to dissect neuronal specific properties or to avoid interspecies contaminations, hindering their future translation into clinical and drug discovery approaches. In this work, we focused on the optimization of a reproducible protocol in feeder-free conditions able to generate functional glutamatergic neurons. This protocol is based on a generation of neuroprecursor cells differentiated into human neurons with the administration in the culture medium of specific neurotrophins in a Geltrex-coated substrate. We confirmed the efficiency of this protocol through molecular analysis (upregulation of neuronal markers and neurotransmitter receptors assessed by gene expression profiling and expression of the neuronal markers at the protein level), morphological analysis, and immunfluorescence detection of pre-synaptic and post-synaptic markers at synaptic boutons. The hiPSC-derived neurons acquired Ca²⁺-dependent glutamate release properties as a hallmark of neuronal maturation. In conclusion, our study describes a new methodological approach to achieve feeder-free neuronal differentiation from hiPSC and adds a new tool for functional characterization of hiPSC-derived neurons.

Herpesvirus Infections in the Human Brain: A Neural Cell Model of the Complement System Derived from Induced Pluripotent Stem Cells

BACKGROUND

Herpesviruses alter cognitive functions in humans following acute infections; progressive cognitive decline and dementia have also been suggested. It is important to understand the pathogenic mechanisms of such infections. The complement system - comprising functionally related proteins integral for systemic innate and adaptive immunity - is an important component of host responses. The complement system has specialized functions in the brain. Still, the dynamics of the brain complement system are still poorly understood. Many complement proteins have limited access to the brain from plasma, necessitating synthesis and specific regulation of expression in the brain; thus, complement protein synthesis, activation, regulation, and signaling should be investigated in human brain-relevant cellular models. Cells derived from human-induced pluripotent stem cells (hiPSCs) could enable tractable models.

METHODS

Human-induced pluripotent stem cells were differentiated into neuronal (hi-N) and microglial (hi-M) cells that were cultured with primary culture human astrocyte-like cells (ha-D). Gene expression analyses and complement protein levels were analyzed in mono- and co-cultures.

RESULTS

Transcript levels of complement proteins differ by cell type and co-culture conditions, with evidence for cellular crosstalk in co-cultures. Hi-N and hi-M cells have distinct patterns of expression of complement receptors, soluble factors, and regulatory proteins. hi-N cells produce complement factor 4 (C4) and factor B (FB), whereas hi-M cells produce complement factor 2 (C2) and complement factor 3 (C3). Thus, neither hi-N nor hi-M cells can form either of the C3-convertases - C4bC2a and C3bBb. However, when hi-N and hi-M cells are combined in co-cultures, both types of functional C3 convertase are produced, indicated by elevated levels of the cleaved C3 protein, C3a.

CONCLUSIONS

hiPSC-derived co-culture models can be used to study viral infection in the brain, particularly complement receptor and function in relation to cellular "crosstalk." The models could be refined to further investigate pathogenic mechanisms.

The roles and applications of neural stem cells in spinal cord injury repair

Spinal cord injury (SCI), which has no current cure, places a severe burden on patients. Stem cell-based therapies are considered promising in attempts to repair injured spinal cords; such options include neural stem cells (NSCs). NSCs are multipotent stem cells that differentiate into neuronal and neuroglial lineages. This feature makes NSCs suitable candidates for regenerating injured spinal cords. Many studies have revealed the therapeutic potential of NSCs. In this review, we discuss from an integrated view how NSCs can help SCI repair. We will discuss the sources and therapeutic potential of NSCs, as well as representative pre-clinical studies and clinical trials of NSC-based therapies for SCI repair.

Application of bioreactor technology for cell culture-based viral vaccine production: Present status and future prospects

Bioreactors are widely used in cell culture-based viral vaccine production, especially during the coronavirus disease 2019 (COVID-19) pandemic. In this context, the development and application of bioreactors can provide more efficient and cost-effective vaccine production to meet the global vaccine demand. The production of viral vaccines is inseparable from the development of upstream biological processes. In particular, exploration at the laboratory-scale is urgently required for further development. Therefore, it is necessary to evaluate the existing upstream biological processes, to enable the selection of pilot-scale conditions for academic and industrial scientists to maximize the yield and quality of vaccine development and production. Reviewing methods for optimizing the upstream process of virus vaccine production, this review discusses the bioreactor concepts, significant parameters and operational strategies related to large-scale amplification of virus. On this basis, a comprehensive analysis and evaluation of the various process optimization methods for the production of various viruses (SARS-CoV-2, Influenza virus, Tropical virus, Enterovirus, Rabies virus) in bioreactors is presented. Meanwhile, the types of viral vaccines are briefly introduced, and the established animal cell lines for vaccine production are described. In addition, it is emphasized that the co-development of bioreactor and computational biology is urgently needed to meet the challenges posed by the differences in upstream production scales between the laboratory and industry.

Basic Fibroblast Growth Factor Induces Cholinergic Differentiation of Tonsil-Derived Mesenchymal Stem Cells

BACKGROUND

Mesenchymal stem cells (MSCs) are considered a potential tool for regenerating damaged tissues due to their great multipotency into various cell types. Here, we attempted to find the appropriate conditions for neuronal differentiation of tonsil-derived MSCs (TMSCs) and expand the potential application of TMSCs for treating neurological diseases.

METHODS

The TMSCs were differentiated in DMEM/F-12 (Dulbecco's Modified Eagle Medium/Nutrient Mixture F-12) supplemented with various neurotrophic factors for 7-28 days to determine the optimal neuronal differentiation condition for the TMSCs. The morphologies as well as the levels of the neural markers and neurotransmitters were assessed to determine neuronal differentiation potentials and the neuronal lineages of the differentiated TMSCs.

RESULTS

Our initial study demonstrated that DMEM/F12 supplemented with 50 ng/mL basic fibroblast growth factor with 10 μM forskolin was the optimal condition for neuronal differentiation for the TMSCs. TMSCs had higher protein expression of neuronal markers, including neuron-specific enolase (NSE), GAP43, postsynaptic density protein 95 (PSD95), and synaptosomal-associated protein of 25 kDa (SNAP25) compared to the undifferentiated TMSCs. Immunofluorescence staining also validated the increased mature neuron markers, NeuN and synaptophysin, in the differentiated TMSCs. The expression of glial fibrillar acidic protein and ionized calcium-binding adaptor molecule 1 the markers of astrocytes and microglia, were also slightly increased. Additionally, the differentiated TMSCs released a significantly higher level of acetylcholine, the cholinergic neurotransmitter, as analyzed by the liquid chromatography-tandem mass spectrometry and showed an enhanced choline acetyltransferase immunoreactivity compared to the undifferentiated cells.

CONCLUSION

Our study suggests that the optimized condition favors the TMSCs to differentiate into cholinergic neuron-like phenotype, which could be used as a possible therapeutic tool in treating certain neurological disorders such as Alzheimer's disease.

Cerebral malaria - modelling interactions at the blood-brain barrier in vitro

The blood–brain barrier (BBB) is a continuous endothelial barrier that is supported by pericytes and astrocytes and regulates the passage of solutes between the bloodstream and the brain. This structure is called the neurovascular unit and serves to protect the brain from blood-borne disease-causing agents and other risk factors. In the past decade, great strides have been made to investigate the neurovascular unit for delivery of chemotherapeutics and for understanding how pathogens can circumvent the barrier, leading to severe and, at times, fatal complications. One such complication is cerebral malaria, in which Plasmodium falciparum-infected red blood cells disrupt the barrier function of the BBB, causing severe brain swelling. Multiple in vitro models of the BBB are available to investigate the mechanisms underlying the pathogenesis of cerebral malaria and other diseases. These range from single-cell monolayer cultures to multicellular BBB organoids and highly complex cerebral organoids. Here, we review the technologies available in malaria research to investigate the interaction between P. falciparum-infected red blood cells and the BBB, and discuss the advantages and disadvantages of each model.

Summary: This Review discusses the available in vitro models to investigate the impact of adhesion of Plasmodium falciparum-infected red blood cells on the blood–brain barrier, a process associated with cerebral malaria.

Roles of the Neuron-Restrictive Silencer Factor in the Pathophysiological Process of the Central Nervous System

The neuron-restrictive silencer factor (NRSF), also known as repressor element 1 (RE-1) silencing transcription factor (REST) or X2 box repressor (XBR), is a zinc finger transcription factor that is widely expressed in neuronal and non-neuronal cells. It is a master regulator of the nervous system, and the function of NRSF is the basis of neuronal differentiation, diversity, plasticity, and survival. NRSF can bind to the neuron-restrictive silencer element (NRSE), recruit some co-repressors, and then inhibit transcription of NRSE downstream genes through epigenetic mechanisms. In neurogenesis, NRSF functions not only as a transcriptional silencer that can mediate the transcriptional inhibition of neuron-specific genes in non-neuronal cells and thus give neuron cells specificity, but also as a transcriptional activator to induce neuronal differentiation. Many studies have confirmed the association between NRSF and brain disorders, such as brain injury and neurodegenerative diseases. Overexpression, underexpression, or mutation may lead to neurological disorders. In tumorigenesis, NRSF functions as an oncogene in neuronal tumors, such as neuroblastomas, medulloblastomas, and pheochromocytomas, stimulating their proliferation, which results in poor prognosis. Additionally, NRSF-mediated selective targets gene repression plays an important role in the development and maintenance of neuropathic pain caused by nerve injury, cancer, and diabetes. At present, several compounds that target NRSF or its co-repressors, such as REST-VP16 and X5050, have been shown to be clinically effective against many brain diseases, such as seizures, implying that NRSF and its co-repressors may be potential and promising therapeutic targets for neural disorders. In the present review, we introduced the biological characteristics of NRSF; reviewed the progress to date in understanding the roles of NRSF in the pathophysiological processes of the nervous system, such as neurogenesis, brain disorders, neural tumorigenesis, and neuropathic pain; and suggested new therapeutic approaches to such brain diseases.

Advances in stem cell therapy in Alzheimer's disease: a comprehensive clinical trial review

Alzheimer's disease (AD) is the most common type of dementia responsible for more than 121,499 deaths from AD in 2019 making AD the sixth-leading cause in the United States. AD is a progressive neurodegenerative disorder characterized by decline of memory, behavioral impairments that affects a person's ability to function independently ultimately leading to death. The current pressing need for a treatment for (AD) and advances in the field of cell therapy, has rendered stem cell therapeutics a promising field of research. Despite advancements in stem cell technology, confirmed by encouraging pre-clinical utilization of stem cells in AD animal models, the number of clinical trials evaluating the efficacy of stem cell therapy is limited, with the results of many ongoing clinical trials on cell therapy for AD still pending. Mesenchymal stem cells (MSCs) have been the main focus in these studies, reporting encouraging results concerning safety profile, however their efficacy remains unproven. In the current article we review the latest advances regarding different sources of stem cell therapy and present a comprehensive list of every available clinical trial in national and international registries. Finally, we discuss drawbacks arising from AD pathology and technical limitations that hinder the transition of stem cell technology from bench to bedside. Our findings emphasize the need to increase clinical trials towards uncovering the mode of action and the underlying therapeutic mechanisms of transplanted cells as well as the molecular mechanisms controlling regeneration and neuronal microenvironment.

Retroviral infection of human neurospheres and use of stem Cell EVs to repair cellular damage

HIV-1 remains an incurable infection that is associated with substantial economic and epidemiologic impacts. HIV-associated neurocognitive disorders (HAND) are commonly linked with HIV-1 infection; despite the development of combination antiretroviral therapy (cART), HAND is still reported to affect at least 50% of HIV-1 infected individuals. It is believed that the over-amplification of inflammatory pathways, along with release of toxic viral proteins from infected cells, are primarily responsible for the neurological damage that is observed in HAND; however, the underlying mechanisms are not well-defined. Therefore, there is an unmet need to develop more physiologically relevant and reliable platforms for studying these pathologies. In recent years, neurospheres derived from induced pluripotent stem cells (iPSCs) have been utilized to model the effects of different neurotropic viruses. Here, we report the generation of neurospheres from iPSC-derived neural progenitor cells (NPCs) and we show that these cultures are permissive to retroviral (e.g. HIV-1, HTLV-1) replication. In addition, we also examine the potential effects of stem cell derived extracellular vesicles (EVs) on HIV-1 damaged cells as there is abundant literature supporting the reparative and regenerative properties of stem cell EVs in the context of various CNS pathologies. Consistent with the literature, our data suggests that stem cell EVs may modulate neuroprotective and anti-inflammatory properties in damaged cells. Collectively, this study demonstrates the feasibility of NPC-derived neurospheres for modeling HIV-1 infection and, subsequently, highlights the potential of stem cell EVs for rescuing cellular damage induced by HIV-1 infection.

In vitro disease modeling of oculocutaneous albinism type 1 and 2 using human induced pluripotent stem cell-derived retinal pigment epithelium

Oculocutaneous albinism (OCA) encompasses a set of autosomal recessive genetic conditions that affect pigmentation in the eye, skin, and hair. OCA patients display reduced best-corrected visual acuity, reduced to absent ocular pigmentation, abnormalities in fovea development, and/or abnormal decussation of optic nerve fibers. It has been hypothesized that improving eye pigmentation could prevent or rescue some of the vision defects. The goal of the present study was to develop an in vitro model for studying pigmentation defects in human retinal pigment epithelium (RPE). We developed a “disease in a dish” model for OCA1A and OCA2 types using induced pluripotent stem cells to generate RPE. The RPE is a monolayer of cells that are pigmented, polarized, and polygonal in shape, located between the neural retina and choroid, with an important role in vision. Here we show that RPE tissue derived in vitro from OCA patients recapitulates the pigmentation defects seen in albinism, while retaining the apical-basal polarity and normal polygonal morphology of the constituent RPE cells.

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We established a human iPSC-based in vitro model for oculocutaneous albinism (OCA)

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iRPE derived from OCA-iPSC retains apical-basal polarity and polygonal morphology

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OCA-iRPE recapitulates the pigmentation defect seen in albinism

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Excess pre-melanosomes and scarce mature melanosomes are found in OCA-iRPE

Enhancement of intercellular interaction between iPSC-derived neural progenitor cells and activated endothelial cells using cell surface modification with functional oligopeptides

Cell-based therapy has been used to treat stroke related disorders, which have no treatment options available 4.5 hours after onset. Although the administration of tissue plasminogen activator and mechanical thrombectomy are potent treatments, their clinical implementation is limited within the available time. Here, we aimed to use induced pluripotent stem cell-derived neural progenitor cells (NPCs) for stroke treatment with higher delivery efficiency in stroke areas, which will improve the therapeutic effect. E-selectin binding oligopeptide (Esbp) was conjugated with poly(ethylene glycol)-conjugated-lipid (Esbp-PEG-lipid) with different molecular weights of PEG (5 and 40 kDa) for cell surface modification. Then, we optimized the cell surface modification of NPCs by studying cell-binding ability onto the model surfaces of stroke areas, such as recombinant E-selectin-immobilized surfaces and TNF-α activated endothelium. As a result, the cell surface modification of NPCs with Esbp-PEG-lipid was found to induce specific intercellular interactions with the activated endothelium through the binding of Esbp with E-selectin. Additionally, the shorter PEG spacer was suitable for intercellular interactions. Thus, our technique shows potential for use in cell therapy with enhanced cell accumulation in infarct areas.

Postsynaptic structure formation of human iPS cell-derived neurons takes longer than presynaptic formation during neural differentiation in vitro

The generation of mature synaptic structures using neurons differentiated from human-induced pluripotent stem cells (hiPSC-neurons) is expected to be applied to physiological studies of synapses in human cells and to pathological studies of diseases that cause abnormal synaptic function. Although it has been reported that synapses themselves change from an immature to a mature state as neurons mature, there are few reports that clearly show when and how human stem cell-derived neurons change to mature synaptic structures. This study was designed to elucidate the synapse formation process of hiPSC-neurons. We propagated hiPSC-derived neural progenitor cells (hiPSC-NPCs) that expressed localized markers of the ventral hindbrain as neurospheres by dual SMAD inhibition and then differentiated them into hiPSC-neurons in vitro. After 49 days of in vitro differentiation, hiPSC-neurons significantly expressed pre- and postsynaptic markers at both the transcript and protein levels. However, the expression of postsynaptic markers was lower than in normal human or normal rat brain tissues, and immunostaining analysis showed that it was relatively modest and was lower than that of presynaptic markers and that its localization in synaptic structures was insufficient. Neurophysiological analysis using a microelectrode array also revealed that no synaptic activity was generated on hiPSC-neurons at 49 days of differentiation. Analysis of subtype markers by immunostaining revealed that most hiPSC-neurons expressed vesicular glutamate transporter 2 (VGLUT2). The presence or absence of NGF, which is required for the survival of cholinergic neurons, had no effect on their cell fractionation. These results suggest that during the synaptogenesis of hiPSC-neurons, the formation of presynaptic structures is not the only requirement for the formation of postsynaptic structures and that the mRNA expression of postsynaptic markers does not correlate with the formation of their mature structures. Technically, we also confirmed a certain level of robustness and reproducibility of our neuronal differentiation method in a multicenter setting, which will be helpful for future research. Synapse formation with mature postsynaptic structures will remain an interesting issue for stem cell-derived neurons, and the present method can be used to obtain early and stable quality neuronal cultures from hiPSC-NPCs.

Induced Pluripotent Stem Cells in Psychiatry: An Overview and Critical Perspective

A key challenge in psychiatry research is the development of high-fidelity model systems that can be experimentally manipulated to explore and test pathophysiological mechanisms of illness. In this respect, the emerging capacity to derive neural cells and circuits from human induced pluripotent stem cells (iPSCs) has generated significant excitement. This review aims to provide a critical appraisal of the potential for iPSCs in illuminating pathophysiological mechanisms in the context of other available technical approaches. We discuss the selection of iPSC phenotypes relevant to psychiatry, the information that researchers can draw on to help guide these decisions, and how researchers choose between the use of 2-dimensional cultures and the use of more complex 3-dimensional model systems. We discuss the strengths and limitations of current models and the challenges and opportunities that they present. Finally, we discuss the potential of iPSC-based model systems for clarifying the mechanisms underlying genetic risk for psychiatry and the steps that will be needed to ensure that robust and reliable conclusions can be drawn. We argue that while iPSC-based models are ideally placed to study fundamental processes occurring within and between neural cells, they are often less well suited for case-control studies, given issues relating to statistical power and the challenges in identifying which cellular phenotypes are meaningful at the level of the whole individual. Our aim is to highlight the importance of considering the hypotheses of a given study to guide decisions about which, if any, iPSC-based system is most appropriate to address it.

Characterization and Optimization of Chitosan-Coated Polybutylcyanoacrylate Nanoparticles for the Transfection-Guided Neural Differentiation of Mouse Induced Pluripotent Stem Cells

Gene transfection is a valuable tool for analyzing gene regulation and function, and providing an avenue for the genetic engineering of cells for therapeutic purposes. Though efficient, the potential concerns over viral vectors for gene transfection has led to research in non-viral alternatives. Cationic polyplexes such as those synthesized from chitosan offer distinct advantages such as enhanced polyplex stability, cellular uptake, endo-lysosomal escape, and release, but are limited by the poor solubility and viscosity of chitosan. In this study, the easily synthesized biocompatible and biodegradable polymeric polysorbate 80 polybutylcyanoacrylate nanoparticles (PS80 PBCA NP) are utilized as the backbone for surface modification with chitosan, in order to address the synthetic issues faced when using chitosan alone as a carrier. Plasmid DNA (pDNA) containing the brain-derived neurotrophic factor (BDNF) gene coupled to a hypoxia-responsive element and the cytomegalovirus promotor gene was selected as the genetic cargo for the in vitro transfection-guided neural-lineage specification of mouse induced pluripotent stem cells (iPSCs), which were assessed by immunofluorescence staining. The chitosan-coated PS80 PBCA NP/BDNF pDNA polyplex measured 163.8 ± 1.8 nm and zeta potential measured -34.8 ± 1.8 mV with 0.01% (w/v) high molecular weight chitosan (HMWC); the pDNA loading efficiency reached 90% at a nanoparticle to pDNA weight ratio of 15, which also corresponded to enhanced polyplex stability on the DNA stability assay. The HMWC-PS80 PBCA NP/BDNF pDNA polyplex was non-toxic to mouse iPSCs for up to 80 μg/mL (weight ratio = 40) and enhanced the expression of BDNF when compared with PS80 PBCA NP/BDNF pDNA polyplex. Evidence for neural-lineage specification of mouse iPSCs was observed by an increased expression of nestin, neurofilament heavy polypeptide, and beta III tubulin, and the effects appeared superior when transfection was performed with the chitosan-coated formulation. This study illustrates the versatility of the PS80 PBCA NP and that surface decoration with chitosan enabled this delivery platform to be used for the transfection-guided differentiation of mouse iPSCs.

Novel test strategies for in vitro seizure liability assessment

INTRODUCTION

The increasing incidence of mental illnesses and neurodegenerative diseases results in a high demand for drugs targeting the central nervous system (CNS). These drugs easily reach the CNS, have a high affinity for CNS targets, and are prone to cause seizures as an adverse drug reaction. Current seizure liability assessment heavily depends on in vivo or ex vivo animal models and is therefore ethically debated, labor intensive, expensive, and not always predictive for human risk.

AREAS COVERED

The demand for CNS drugs urges the development of alternative safety assessment strategies. Yet, the complexity of the CNS hampers reliable detection of compound-induced seizures. This review provides an overview of the requirements of in vitro seizure liability assays and highlights recent advances, including micro-electrode array (MEA) recordings using rodent and human cell models.

EXPERT OPINION

Successful and cost-effective replacement of in vivo and ex vivo models for seizure liability screening can reduce animal use for drug development, while increasing the predictive value of the assays, particularly if human cell models are used. However, these novel test strategies require further validation and standardization as well as additional refinements to better mimic the human in vivo situation and increase their predictive value.

Live Viral Vaccine Neurovirulence Screening: Current and Future Models

Live viral vaccines are one of the most successful methods for controlling viral infections but require strong evidence to indicate that they are properly attenuated. Screening for residual neurovirulence is an important aspect for live viral vaccines against potentially neurovirulent diseases. Approximately half of all emerging viral diseases have neurological effects, so testing of future vaccines will need to be rapid and accurate. The current method, the monkey neurovirulence test (MNVT), shows limited translatability for human diseases and does not account for different viral pathogenic mechanisms. This review discusses the MNVT and potential alternative models, including in vivo and in vitro methods. The advantages and disadvantages of these methods are discussed, and there are promising data indicating high levels of translatability. There is a need to investigate these models more thoroughly and to devise more accurate and rapid alternatives to the MNVT.

Microphysiological models of the central nervous system with fluid flow

There are over 1,000 described neurological and neurodegenerative disorders affecting nearly 100 million Americans - roughly one third of the U.S. population. Collectively, treatment of neurological conditions is estimated to cost $800 billion every year. Lowering this societal burden will require developing better model systems in which to study these diverse disorders. Microphysiological systems are promising tools for modeling healthy and diseased neural tissues to study mechanisms and treatment of neuropathology. One major benefit of microphysiological systems is the ability to incorporate biophysical forces, namely the forces derived from biological fluid flow. Fluid flow in the central nervous system (CNS) is a complex but important element of physiology, and pathologies as diverse as traumatic or ischemic injury, cancer, neurodegenerative disease, and natural aging have all been found to alter flow pathways. In this review, we summarize recent advances in three-dimensional microphysiological systems for studying the biology and therapy of CNS disorders and highlight the ability and growing need to incorporate biological fluid flow in these miniaturized model systems.

Polycomb group protein Bmi1 is required for the neuronal differentiation of mouse induced pluripotent stem cells

Induced pluripotent stem cells (iPSCs) reprogrammed by somatic cells may be used as a potentially novel treatment regimen in stem cell regenerative medicine, particularly in the central nervous system (CNS). In the present study, iPSCs were generated using mouse embryonic fibroblasts by ectopic overexpression of Sox-2, Oct-3/4, Klf-4 and c-Myc, and cultured under the same conditions as that used for embryonic stem cells. The neuronal differentiation capacity of mouse iPSCs was examined, and the involvement of the formation of embryoid bodies was assessed. The results suggested that after 15 days of neuronal inducement, Nestin, Vimentin and Glast protein expression levels were significantly increased in the mouse iPSC-derived cells. Additionally, Bmi1, which is selectively expressed in differentiated postnatal adult stem cells. such as hematopoietic stem cells and neural stem cells, was required for establishment of the neuronal differentiation of mouse iPSCs. In order to assess the effects of Bmi1 in neuronal differentiation, Bmi1 expression levels were inhibited with the small molecule PTC-209. The results showed that inhibition of Bmi1 expression reduced the expression of neuronal markers, such as Nestin, compared with the controls. These results suggested that mouse iPSCs can be induced to achieve neuronal differentiation. More interestingly, Bmi1 was required during the neuronal differentiation of mouse iPSCs.

Bioengineering the neurovascular niche to study the interaction of neural stem cells and endothelial cells

The ability of mammalian neural stem cells (NSCs) to self-renew and differentiate throughout adulthood has made them ideal to study neurogenesis and attractive candidates for neurodegenerative disease therapies. In the adult mammalian brain, NSCs are maintained in the neurovascular niche (NVN) where they are found near the specialized blood vessels, suggesting that brain endothelial cells (BECs) are prominent orchestrators of NSC fate. However, most of the current knowledge of the mammalian NVN has been deduced from nonhuman studies. To circumvent the challenges of in vivo studies, in vitro models have been developed to better understand the reciprocal cellular mechanisms of human NSCs and BECs. This review will cover the current understanding of mammalian NVN biology, the effects of endothelial cell-derived signals on NSC fate, and the in vitro models developed to study the interactions between NSCs and BECs.

Modeling Aβ42 Accumulation in Response to Herpes Simplex Virus 1 Infection: 2D or 3D?

Alzheimer's disease is a progressive neurodegenerative disease characterized neuropathologically by presence of extracellular amyloid plaques composed of fibrillar amyloid beta (Aβ) peptides and intracellular neurofibrillary tangles. Post-mortem and in vivo studies implicate HSV-1 infection in the brain as a precipitating factor in disease/pathology initiation. HSV-1 infection of two-dimensional (2D) neuronal cultures causes intracellular accumulation of Aβ42 peptide, but these 2D models do not recapitulate the three-dimensional (3D) architecture of brain tissue.We employed human induced pluripotent stem cells (hiPSCs) to compare patterns of Aβ42 accumulation in HSV-1 infected 2D (neuronal monolayers) and 3D neuronal cultures (brain organoids). Akin to prior studies, HSV-1-infected 2D cultures showed Aβ42 immunoreactivity in cells expressing the HSV-1 antigen ICP4 (ICP4+). Conversely, accumulation of Aβ42 in ICP4+ cells in infected organoids was rarely observed. These results highlight the importance of considering 3D cultures to model host-pathogen interaction.IMPORTANCE The "pathogen" hypothesis of Alzheimer's disease (AD) proposes that brain HSV-1 infection could be an initial source of amyloid beta (Aβ) peptide-containing amyloid plaque development. Aβ accumulation was reported in HSV-1-infected 2D neuronal cultures and neural stem cell cultures, as well as in HSV-1-infected 3D neuronal culture models.The current study extends these findings by showing different patterns of Aβ42 accumulation following HSV-1 infection of 2D compared to 3D neuronal cultures (brain organoids). Specifically, 2D neuronal cultures showed Aβ42-immunoreactivity mainly in HSV-1-infected cells and only rarely in uninfected cells or infected cells exposed to antivirals. Conversely, 3D brain organoids showed accumulation of Aβ42 mainly in non-infected cells surrounding HSV-1-infected cells. We suggest that because brain organoids better recapitulate architectural features of a developing brain than 2D cultures, they may be a more suitable model to investigate the involvement of HSV-1 in the onset of AD pathology.

Ascorbic acid can promote the generation and expansion of neuroepithelial-like stem cells derived from hiPS/ES cells under chemically defined conditions through promoting collagen synthesis

INTRODUCTION

Spinal cord injury (SCI) is a neurological, medically incurable disorder. Human pluripotent stem cells (hPSCs) have the potential to generate neural stem/progenitor cells (NS/PCs), which hold promise in the treatment of SCI by transplantation. In our study, we aimed to establish a chemically defined culture system using serum-free medium and ascorbic acid (AA) to generate and expand long-term self-renewing neuroepithelial-like stem cells (lt-NES cells) differentiated from hPSCs effectively and stably.

METHODS

We induced human embryonic stem cells (hESCs)/induced PSCs (iPSCs) to neurospheres using a newly established in vitro induction system. Moreover, lt-NES cells were derived from hESC/iPSC-neurospheres using two induction systems, i.e., conventional N2 medium with gelatin-coated plates (coated) and N2+AA medium without pre-coated plates (AA), and were characterized by reverse transcription polymerase chain reaction (RT-PCR) analysis and immunocytochemistry staining. Subsequently, lt-NES cells were induced to neurons. A microelectrode array (MEA) recording system was used to evaluate the functionality of the neurons differentiated from lt-NES cells. Finally, the mechanism underlying the induction of lt-NES cells by AA was explored through RNA-seq and the use of inhibitors.

RESULTS

HESCs/iPSCs were efficiently induced to neurospheres using a newly established induction system in vitro. lt-NES cells derived from hESC/iPSC-neurospheres using the two induction systems (coated vs. AA) both expressed the neural pluripotency-associated genes PAX6, NESTIN, SOX1, and SOX2. After long-term cultivation, we found that they both exhibited long-term expansion for more than a dozen generations while maintaining neuropluripotency. Moreover, the lt-NES cells retained the ability to differentiate into general functional neurons that express β-tubulin at high levels. We also demonstrated that AA promotes the generation and long-term expansion of lt-NES cells by promoting collagen synthesis via the MEK-ERK1/2 pathway.

CONCLUSIONS

This new chemically defined culture system was stable and effective regarding the generation and culture of lt-NES cells induced from hESCs/iPSCs using serum-free medium combined with AA. The lt-NES cells induced under this culture system maintained their long-term expansion and neural pluripotency, with the potential to differentiate into functional neurons.

Insights into bioinformatic approaches for repurposing compounds as anti-viral drugs

BACKGROUND

Drug repurposing is a cost-effective strategy to identify drugs with novel effects. We searched for drugs exhibiting inhibitory activity to Herpes Simplex virus 1 (HSV-1). Our strategy utilized gene expression data generated from HSV-1-infected cell cultures which was paired with drug effects on gene expression. Gene expression data from HSV-1 infected and uninfected neurons were analyzed using BaseSpace Correlation Engine (Illumina®). Based on the general Signature Reversing Principle (SRP), we hypothesized that the effects of candidate antiviral drugs on gene expression would be diametrically opposite (negatively correlated) to those effects induced by HSV-1 infection.

RESULTS

We initially identified compounds capable of inducing changes in gene expression opposite to those which were consequent to HSV-1 infection. The most promising negatively correlated drugs (Valproic acid, Vorinostat) did not significantly inhibit HSV-1 infection further in African green monkey kidney epithelial cells (Vero cells). Next, we tested Sulforaphane and Menadione which showed effects similar to those caused by viral infections (positively correlated). Intriguingly, Sulforaphane caused a modest but significant inhibition of HSV-1 infection in Vero cells (IC50 = 180.4 µM, p = 0.008), but exhibited toxicity when further explored in human neuronal progenitor cells (NPCs) derived from induced pluripotent stem cells.

CONCLUSIONS

These results reveal the limits of the commonly used SRP strategy when applied to the identification of novel antiviral drugs and highlight the necessity to refine the SRP strategy to increase its utility.

Neuroregeneration and functional recovery after stroke: advancing neural stem cell therapy toward clinical application

Stroke is a main cause of death and disability worldwide. The ability of the brain to self-repair in the acute and chronic phases after stroke is minimal; however, promising stem cell-based interventions are emerging that may give substantial and possibly complete recovery of brain function after stroke. Many animal models and clinical trials have demonstrated that neural stem cells (NSCs) in the central nervous system can orchestrate neurological repair through nerve regeneration, neuron polarization, axon pruning, neurite outgrowth, repair of myelin, and remodeling of the microenvironment and brain networks. Compared with other types of stem cells, NSCs have unique advantages in cell replacement, paracrine action, inflammatory regulation and neuroprotection. Our review summarizes NSC origins, characteristics, therapeutic mechanisms and repair processes, then highlights current research findings and clinical evidence for NSC therapy. These results may be helpful to inform the direction of future stroke research and to guide clinical decision-making.

Standards of induced pluripotent stem cells derived clinical-grade neural stem cells preparation and quality control (2021 China version)

Induced pluripotent stem cells (iPSCs) have become the leading research object in the clinical application of restorative medicine. They are easily generated from diverse cell sources and functionally indistinguishable from embryonic stem cells without the accompanying ethical issues. To date, the use of iPSC-derived neural stem cells and their progeny in the treatment of neurodegenerative and injurious diseases has achieved good results, with great potential in cell drug development. However, because of some unique biological properties and differences from traditional drug production processes, cell drug research and development has many problems that can hinder clinical applications. Given this situation, the Chinese Association of Neurorestoratology (Preparatory) and China Committee of the International Association of Neurorestoratology have organized relevant professional experts to formulate the standard presented here. Overall, the aim was to promote the clinical application of neural stem cells (NSCs) and their further derived neural cells from iPSC sources and promote cell drugs’ production and development. This standard refers to the latest research results, quality evaluation criteria for traditional medicines, and the regulatory framework for cellular treatments. The standard considers general biological properties of cells, including cell morphology, cell cycle, karyotype, and cell viability. The specific biological properties of NSCs, such as cell surface markers and differentiation ability, general drug standards, such as aseptic testing, endotoxins, human virus detection, and cell-related drug standards, such as telomerase activity and tumorigenicity, are also considered. This standard will serve as a reference for physicians and scientists who focus on clinical nervous cell applications and studies related to iPSCs.

Review: In vitro Cell Platform for Understanding Developmental Toxicity

Developmental toxicity and its affiliation to long-term health, particularly neurodegenerative disease (ND) has attracted significant attentions in recent years. There is, however, a significant gap in current models to track longitudinal changes arising from developmental toxicity. The advent of induced pluripotent stem cell (iPSC) derived neuronal culture has allowed for more complex and functionally active in vitro neuronal models. Coupled with recent progress in the detection of ND biomarkers, we are equipped with promising new tools to understand neurotoxicity arising from developmental exposure. This review provides a brief overview of current progress in neuronal culture derived from iPSC and in ND markers.

An efficient neuron-astrocyte differentiation protocol from human embryonic stem cell-derived neural progenitors to assess chemical-induced developmental neurotoxicity

Human embryonic stem cell neuronal differentiation models provide promising in vitro tools for the prediction of developmental neurotoxicity of chemicals. Such models mimic essential elements of human relevant neuronal development, including the differentiation of a variety of brain cell types and their neuronal network formation as evidenced by specific gene and protein biomarkers. However, the reproducibility and lengthy culture duration of cell models present drawbacks and delay regulatory implementation. Here we present a relatively short and robust protocol to differentiate H9-derived neural progenitor cells (NPCs) into a neuron-astrocyte co-culture. When frozen-stored NPCs were re-cultured and induced into neuron-astrocyte differentiation, they showed gene- and protein expression typical for these cells, and most notably they exhibited spontaneous electrical activity within three days of culture as measured by a multi-well micro-electrode array. Modulating the ratio of astrocytes and neurons through different growth factors including glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), and ciliary neurotrophic factor (CNTF) did not compromise the ability to develop spontaneous electrical activity. This robust neuronal differentiation model may serve as a functional component of a testing strategy for unravelling mechanisms of developmental neurotoxicity.

Population-scale proteome variation in human induced pluripotent stem cells

Human disease phenotypes are driven primarily by alterations in protein expression and/or function. To date, relatively little is known about the variability of the human proteome in populations and how this relates to variability in mRNA expression and to disease loci. Here, we present the first comprehensive proteomic analysis of human induced pluripotent stem cells (iPSC), a key cell type for disease modelling, analysing 202 iPSC lines derived from 151 donors, with integrated transcriptome and genomic sequence data from the same lines. We characterised the major genetic and non-genetic determinants of proteome variation across iPSC lines and assessed key regulatory mechanisms affecting variation in protein abundance. We identified 654 protein quantitative trait loci (pQTLs) in iPSCs, including disease-linked variants in protein-coding sequences and variants with trans regulatory effects. These include pQTL linked to GWAS variants that cannot be detected at the mRNA level, highlighting the utility of dissecting pQTL at peptide level resolution.

Patterns of Herpes Simplex Virus 1 Infection in Neural Progenitor Cells

This study employed human induced pluripotent stem cells (hiPSCs) to model the interaction of HSV-1 with NPCs, which reside in the neurogenic niches of the CNS and play a fundamental role in adult neurogenesis. Herein, we provide evidence that in NPCs infected at an MOI as low as 0.001, HSV-1 can establish a latent state, suggesting that (i) a variant of classical HSV-1 latency can be established during earlier stages of neuronal differentiation and (ii) neurogenic niches in the brain may constitute additional sites of viral reactivation. Lytic HSV-1 infections impaired NPC migration, which represents a critical step in neurogenesis. A difference in susceptibility to HSV-1 infection between two-dimensional (2D) and three-dimensional (3D) NPC cultures was observed, highlighting the potential value of 3D cultures for modeling host-pathogen interactions. Together, our results are relevant in light of observations relating HSV-1 infection to postencephalitic cognitive dysfunction.

Herpes simplex virus 1 (HSV-1) can induce damage in brain regions that include the hippocampus and associated limbic structures. These neurogenic niches are important because they are associated with memory formation and are highly enriched with neural progenitor cells (NPCs). The susceptibility and fate of HSV-1-infected NPCs are largely unexplored. We differentiated human induced pluripotent stem cells (hiPSCs) into NPCs to generate two-dimensional (2D) and three-dimensional (3D) culture models to examine the interaction of HSV-1 with NPCs. Here, we show that (i) NPCs can be efficiently infected by HSV-1, but infection does not result in cell death of most NPCs, even at high multiplicities of infection (MOIs); (ii) limited HSV-1 replication and gene expression can be detected in the infected NPCs; (iii) a viral silencing mechanism is established in NPCs exposed to the antivirals (E)-5-(2-bromovinyl)-2′-deoxyuridine (5BVdU) and alpha interferon (IFN-α) and when the antivirals are removed, spontaneous reactivation can occur at low frequency; (iv) HSV-1 impairs the ability of NPCs to migrate in a dose-dependent fashion in the presence of 5BVdU plus IFN-α; and (v) 3D cultures of NPCs are less susceptible to HSV-1 infection than 2D cultures. These results suggest that NPC pools could be sites of HSV-1 reactivation in the central nervous system (CNS). Finally, our results highlight the potential value of hiPSC-derived 3D cultures to model HSV-1–NPC interaction.

IMPORTANCE This study employed human induced pluripotent stem cells (hiPSCs) to model the interaction of HSV-1 with NPCs, which reside in the neurogenic niches of the CNS and play a fundamental role in adult neurogenesis. Herein, we provide evidence that in NPCs infected at an MOI as low as 0.001, HSV-1 can establish a latent state, suggesting that (i) a variant of classical HSV-1 latency can be established during earlier stages of neuronal differentiation and (ii) neurogenic niches in the brain may constitute additional sites of viral reactivation. Lytic HSV-1 infections impaired NPC migration, which represents a critical step in neurogenesis. A difference in susceptibility to HSV-1 infection between two-dimensional (2D) and three-dimensional (3D) NPC cultures was observed, highlighting the potential value of 3D cultures for modeling host-pathogen interactions. Together, our results are relevant in light of observations relating HSV-1 infection to postencephalitic cognitive dysfunction.

Extracellular vesicles isolated from human olfactory ensheathing cells enhance the viability of neural progenitor cells

OBJECTIVE

Acquired neurological diseases such as severe traumatic brain or spinal cord injury (SCI) cause irreversible disability. Olfactory ensheathing cell (OEC) transplantation has been trialed as a promising SCI treatment. Extracellular vesicles (EVs), which regulate cell-cell interactions, have recently garnered extensive research interests and emerged as a non-cell-based therapy in neurological disorders, including in SCI animal models. However, there have been no reports of human OEC-EVs and their beneficial effects on neuron regeneration. Here, we investigated the effects of EVs isolated from human OEC on the viability of neuronal cells.

METHODS

EVs were isolated from primary human OECs (hOECs) by serial ultracentrifugation. The hOEC-EVs were characterized by transmission electron microscopy, western blotting, and nanoparticle tracking analyses. We conducted CCK8 and lactate dehydrogenase assays to assess the cell proliferation and cytotoxicity of neural progenitor cells (NPCs) exposed to hOEC-EVs. Tert-butyl hydroperoxide (t-BHP) was utilized to mimic oxidative stress-induced cytotoxicity in NPCs.

RESULTS

The modal diameter of hOEC-derived EVs was 113.2 nm. Expressions of EV markers such as CD9, CD63, and CD81 were detected by western blotting. hOEC-derived EVs enhanced the proliferation of NPCs and ameliorated cell cytotoxicity mediated by t-BHP.

DISCUSSION

Our findings reveal a role for hOEC-derived EVs in NPC proliferation and oxidative stress-induced neuronal toxicity model. These results may be useful for developing non-cell therapy OEC-EV-based treatment in acquired nervous system disease.

Human pluripotent stem cell-derived models and drug screening in CNS precision medicine

Development of effective therapeutics for neurological disorders has historically been challenging partly because of lack of accurate model systems in which to investigate disease etiology and test new therapeutics at the preclinical stage. Human stem cells, particularly patient-derived induced pluripotent stem cells (iPSCs) upon differentiation, have the ability to recapitulate aspects of disease pathophysiology and are increasingly recognized as robust scalable systems for drug discovery. We review advances in deriving cellular models of human central nervous system (CNS) disorders using iPSCs along with strategies for investigating disease-relevant phenotypes, translatable biomarkers, and therapeutic targets. Given their potential to identify novel therapeutic targets and leads, we focus on phenotype-based, small-molecule screens employing human stem cell-derived models. Integrated efforts to assemble patient iPSC-derived cell models with deeply annotated clinicopathological data, along with molecular and drug-response signatures, may aid in the stratification of patients, diagnostics, and clinical trial success, shifting translational science and precision medicine approaches. A number of remaining challenges, including the optimization of cost-effective, large-scale culture of iPSC-derived cell types, incorporation of aging into neuronal models, as well as robustness and automation of phenotypic assays to support quantitative drug efficacy, toxicity, and metabolism testing workflows, are covered. Continued advancement of the field is expected to help fully humanize the process of CNS drug discovery.