Efficient generation of myelinating oligodendrocytes from primary progressive multiple sclerosis patients by induced pluripotent stem cells

A human iPSC-Derived myelination model for investigating fetal brain injuries

Cerebral white matter injuries, such as periventricular leukomalacia, are major contributors to neurodevelopmental impairments in preterm infants. Despite the clinical significance of these conditions, human-relevant models for studying fetal brain development and injury mechanisms remain limited. This study introduces a human iPSC-derived myelination model developed using a microfluidic device. The platform combines spinal cord-patterned neuronal and oligodendrocyte spheroids to recapitulate axon-glia interactions and myelination processes in vitro. The model successfully achieved axonal fascicle formation and compact myelin deposition, as validated by immunostaining and transmission electron microscopy. Functional calcium imaging confirmed neuronal activity within the system, underscoring its physiological relevance. While myelination efficiency was partial, with some axons remaining unmyelinated under the current conditions, this model represents a significant advancement in human myelin biology, offering a foundation for investigating fetal and perinatal brain injuries and related pathologies. Future refinements, such as improved myelination coverage and incorporating additional CNS cell types, will enhance its utility for studying disease mechanisms and enabling high-throughput drug screening.

Repurposed Drugs to Enhance the Therapeutic Potential of Oligodendrocyte Precursor Cells Derived from Adult Rat Adipose Tissue

Failure in the proliferation, recruitment, mobilization, and/or differentiation of oligodendrocyte precursor cells (OPCs) impedes remyelination in central nervous system (CNS) demyelinating diseases. Our group has recently achieved the generation of functional oligodendroglia through direct lineage conversion by expressing Sox10, Olig2, and Zfp536 genes in adult rat adipose tissue-derived stromal cells. The present study aimed to determine whether various repurposed drugs or molecules could enhance the myelinating capacities of these induced OPCs (iOPCs). We report that kainate, benztropine, miconazole, clobetasol, and baclofen promote in vitro iOPCs migration, differentiation, and ensheathing abilities through mechanisms similar to those observed in rat neural stem cell-derived OPCs. This research supports the potential use of iOPCs as they provide an alternative and reliable cell source for testing the effects of in vitro promyelinating repurposed drugs and for assessing the molecular and cellular mechanisms involved in therapeutic strategies for demyelinating diseases.

Cholesterol-mediated Lysosomal Dysfunction in APOE4 Astrocytes Promotes α-Synuclein Pathology in Human Brain Tissue

The pathological hallmark of neurodegenerative disease is the aberrant post-translational modification and aggregation of proteins leading to the formation of insoluble protein inclusions. Genetic factors like APOE4 are known to increase the prevalence and severity of tau, amyloid, and α-Synuclein inclusions. However, the human brain is largely inaccessible during this process, limiting our mechanistic understanding. Here, we developed an iPSC-based 3D model that integrates neurons, glia, myelin, and cerebrovascular cells into a functional human brain tissue (miBrain). Like the human brain, we found pathogenic phosphorylation and aggregation of α-Synuclein is increased in the APOE4 miBrain. Combinatorial experiments revealed that lipid-droplet formation in APOE4 astrocytes impairs the degradation of α-synuclein and leads to a pathogenic transformation that seeds neuronal inclusions of α-Synuclein. Collectively, this study establishes a robust model for investigating protein inclusions in human brain tissue and highlights the role of astrocytes and cholesterol in APOE4-mediated pathologies, opening therapeutic opportunities.

Therapeutic Potential of Experimental Stereotactic Hippocampal Cell Transplant in the Management of Alzheimer's Disease

Due to a continuous increase in life expectancy and the progress made in specialized healthcare, the incidence of Alzheimer's disease (AD) has dramatically increased to the point that it has become one of the main challenges of contemporary medicine. Despite a huge scientific and clinical effort, current treatments manage just a temporary alleviation of symptomatology but offer no cure. Modern trials involving cell transplantation in experimental animals require the involvement of neurosurgeons in the treatment protocol. CSF shunting, intraventricular infusions, or DBS for symptoms relief have been an integral part of the therapeutic arsenal from the very beginning. The development of stereotactic surgery has facilitated the experimental potential of cell transplantation in the hippocampus for Alzheimer's disease. We conducted a narrative review of the literature in the top three medical databases (PubMed, Science Direct, and Google Scholar) using the keywords "Alzheimer's disease", "hippocampus", and "transplant". After eliminating duplicates, 241 papers were selected and screened by title and abstract. Two reviewers independently analyzed the 88 papers and chose 32 experiments that involved stereotactic hippocampal transplantation of cells in experimental animals with AD. The stereotactic transplantation of cells such as mesenchymal stem cells (MSCs), neuronal stem cells (NSCs), induced pluripotent cells (iPSCs), astrocytes, and derivates from stem cells was analyzed. The experiments used either a chemically induced or transgenic AD model and observed the impact of the stereotactic transplantation with behavioral testing, MRS spectroscopy, and biochemical analysis. The stereotaxic method delivers minimal invasive treatment option by cell transplantation at the hippocampus. The results showed that amyloid deposits were lower after transplantation, showing a positive impact. Other impactful results involve proliferation of neurogenesis, downregulation of anti-inflammatory response, and increased neuronal plasticity. The increased precision with which the stereotaxic method manages to target deep structures of the brain and the results of the reviewed papers could represent an argument for future human trials. More studies are needed to confirm the viability of the transplanted cells and the long-term effects.

In vitro models for human neuroglia

Neuroglia are a heterogenous population of cells in the nervous system. In the central nervous system, this group is classified into astrocytes, oligodendrocytes, and microglia. Neuroglia in the peripheral nervous system are divided into Schwann cells and enteric glia. These groups of cells display considerable differences in their developmental origin, morphology, function, and regional abundance. Compared to animal models, human neuroglia differ in their transcriptomic profile, morphology, and function. Investigating the physiology of healthy or diseased human neuroglia in vivo is challenging due to the inaccessibility of the tissue. Therefore, researchers have developed numerous in vitro models attempting to replicate the natural tissue environment. Earlier models made use of postmortem, postsurgical, or fetal tissue to establish human neuroglial cells in vitro, either as a pure population of the desired cell type or as organotypic slice cultures. Advancements in human stem cell differentiation techniques have greatly enhanced the possibilities for creating in vitro models of human neuroglia. This chapter provides an overview of the current models used to study the functioning and development of human neuroglia in vitro, both in health and disease.

Patient iPSC models reveal glia-intrinsic phenotypes in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory and neurodegenerative disease of the central nervous system (CNS), resulting in neurological disability that worsens over time. While progress has been made in defining the immune system's role in MS pathophysiology, the contribution of intrinsic CNS cell dysfunction remains unclear. Here, we generated a collection of induced pluripotent stem cell (iPSC) lines from people with MS spanning diverse clinical subtypes and differentiated them into glia-enriched cultures. Using single-cell transcriptomic profiling and orthogonal analyses, we observed several distinguishing characteristics of MS cultures pointing to glia-intrinsic disease mechanisms. We found that primary progressive MS-derived cultures contained fewer oligodendrocytes. Moreover, MS-derived oligodendrocyte lineage cells and astrocytes showed increased expression of immune and inflammatory genes, matching those of glia from MS postmortem brains. Thus, iPSC-derived MS models provide a unique platform for dissecting glial contributions to disease phenotypes independent of the peripheral immune system and identify potential glia-specific targets for therapeutic intervention.

Increased cholesterol synthesis drives neurotoxicity in patient stem cell-derived model of multiple sclerosis

Senescent neural progenitor cells have been identified in brain lesions of people with progressive multiple sclerosis (PMS). However, their role in disease pathobiology and contribution to the lesion environment remains unclear. By establishing directly induced neural stem/progenitor cell (iNSC) lines from PMS patient fibroblasts, we studied their senescent phenotype in vitro. Senescence was strongly associated with inflammatory signaling, hypermetabolism, and the senescence-associated secretory phenotype (SASP). PMS-derived iNSCs displayed increased glucose-dependent fatty acid and cholesterol synthesis, which resulted in the accumulation of lipid droplets. A 3-hydroxy-3-methylglutaryl (HMG)-coenzyme A (CoA) reductase (HMGCR)-mediated lipogenic state was found to induce a SASP in PMS iNSCs via cholesterol-dependent transcription factors. SASP from PMS iNSC lines induced neurotoxicity in mature neurons, and treatment with the HMGCR inhibitor simvastatin altered the PMS iNSC SASP, promoting cytoprotective qualities and reducing neurotoxicity. Our findings suggest a disease-associated, cholesterol-related, hypermetabolic phenotype of PMS iNSCs that leads to neurotoxic signaling and is rescuable pharmacologically.

Remyelinating Drugs at a Crossroad: How to Improve Clinical Efficacy and Drug Screenings

Axons wrapped around the myelin sheath enable fast transmission of neuronal signals in the Central Nervous System (CNS). Unfortunately, myelin can be damaged by injury, viral infection, and inflammatory and neurodegenerative diseases. Remyelination is a spontaneous process that can restore nerve conductivity and thus movement and cognition after a demyelination event. Cumulative evidence indicates that remyelination can be pharmacologically stimulated, either by targeting natural inhibitors of Oligodendrocyte Precursor Cells (OPCs) differentiation or by reactivating quiescent Neural Stem Cells (qNSCs) proliferation and differentiation in myelinating Oligodendrocytes (OLs). Although promising results were obtained in animal models for demyelination diseases, none of the compounds identified have passed all the clinical stages. The significant number of patients who could benefit from remyelination therapies reinforces the urgent need to reassess drug selection approaches and develop strategies that effectively promote remyelination. Integrating Artificial Intelligence (AI)-driven technologies with patient-derived cell-based assays and organoid models is expected to lead to novel strategies and drug screening pipelines to achieve this goal. In this review, we explore the current literature on these technologies and their potential to enhance the identification of more effective drugs for clinical use in CNS remyelination therapies.

Injectable shear-thinning hydrogels promote oligodendrocyte progenitor cell survival and remyelination in the central nervous system

Cell therapy for the treatment of demyelinating diseases such as multiple sclerosis is hampered by poor survival of donor oligodendrocyte cell preparations, resulting in limited therapeutic outcomes. Excessive cell death leads to the release of intracellular alloantigens, which likely exacerbate local inflammation and may predispose the graft to eventual rejection. Here, we engineered innovative cell-instructive shear-thinning hydrogels (STHs) with tunable viscoelasticity and bioactivity for minimally invasive delivery of primary human oligodendrocyte progenitor cells (hOPCs) to the brain of a shiverer/rag2 mouse, a model of congenital hypomyelinating disease. The STHs enabled immobilization of prosurvival signals, including a recombinantly designed bidomain peptide and platelet-derived growth factor. Notably, STHs reduced the death rate of hOPCs significantly, promoted the production of myelinating oligodendrocytes, and enhanced myelination of the mouse brain 12 weeks post-implantation. Our results demonstrate the potential of STHs loaded with biological cues to improve cell therapies for the treatment of devastating myelopathies.

A review: oligodendrocytes in neuronal axonal conduction and methods for enhancing their performance

OBJECTIVES

This review explores the vital role of oligodendrocytes in axon myelination and efficient neuronal transmission and the impact of dysfunction resulting from neurotransmitter deficiencies related disorders. Furthermore, the review also provides insight into the potential of bionanotechnology for addressing neurodegenerative diseases by targeting oligodendrocytes.

METHODS

A review of literature in the field was conducted using Google scholar. Systematic searches were performed to identify relevant studies and reviews addressing the role of oligodendrocytes in neural function, the influence of neurotransmitters on oligodendrocyte differentiation, and the potential of nanotechnology-based strategies for targeted therapy of oligodendrocytes.

RESULTS

This review indicates the mechanisms underlying oligodendrocyte differentiation and the influence of neurotransmitters on this process. The importance of action potentials and neurotransmission in neural function and the susceptibility of damaged nerve axons to ischemic or toxic damage is provided in detail. The potential of bionanotechnology for targeting neurodegenerative diseases using nanotechnology-based strategies, including polymeric, lipid-based, inorganic, organic, and biomimetic nanoparticles, suggests better management of neurodegenerative disorders.

CONCLUSION

While nanotechnology-based biomaterials show promise for targeted oligodendrocyte therapy in addressing neurodegenerative disorders linked to oligodendrocyte dysfunction, encapsulating neuroprotective agents within nanoparticles offers additional advantages. Nano-based delivery systems effectively protect drugs from degradation and prolong their therapeutic effects, holding promise in overcoming the blood-brain barrier by facilitating drug transport. However, a multifaceted approach is essential to enhance oligodendrocyte differentiation, promote myelin repair, and facilitate myelin dynamics with reduced toxicity. Further research is needed to elucidate the optimal therapeutic approaches and enhance patient outcomes.

Neuronal Cell Differentiation of iPSCs for the Clinical Treatment of Neurological Diseases

Current chemical treatments for cerebrovascular disease and neurological disorders have limited efficacy in tissue repair and functional restoration. Induced pluripotent stem cells (iPSCs) present a promising avenue in regenerative medicine for addressing neurological conditions. iPSCs, which are capable of reprogramming adult cells to regain pluripotency, offer the potential for patient-specific, personalized therapies. The modulation of molecular mechanisms through specific growth factor inhibition and signaling pathways can direct iPSCs' differentiation into neural stem cells (NSCs). These include employing bone morphogenetic protein-4 (BMP-4), transforming growth factor-beta (TGFβ), and Sma-and Mad-related protein (SMAD) signaling. iPSC-derived NSCs can subsequently differentiate into various neuron types, each performing distinct functions. Cell transplantation underscores the potential of iPSC-derived NSCs to treat neurodegenerative diseases such as Parkinson's disease and points to future research directions for optimizing differentiation protocols and enhancing clinical applications.

Engineered 3D Immuno-Glial-Neurovascular Human miBrain Model

Patient-specific, human-based cellular models integrating a biomimetic blood-brain barrier (BBB), immune, and myelinated neuron components are critically needed to enable accelerated, translationally relevant discovery of neurological disease mechanisms and interventions. By engineering a novel brain-mimicking 3D hydrogel and co-culturing all six major brain cell types derived from patient iPSCs, we have constructed, characterized, and utilized a multicellular integrated brain (miBrain) immuno-glial-neurovascular model with in vivo- like hallmarks inclusive of neuronal activity, functional connectivity, barrier function, myelin-producing oligodendrocyte engagement with neurons, multicellular interactions, and transcriptomic profiles. We implemented the model to study Alzheimer's Disease pathologies associated with APOE4 genetic risk. APOE4 miBrains differentially exhibit amyloid aggregation, tau phosphorylation, and astrocytic GFAP. Unlike the co-emergent fate specification of glia and neurons in organoids, miBrains integrate independently differentiated cell types, a feature we harnessed to identify that APOE4 in astrocytes promotes neuronal tau pathogenesis and dysregulation through crosstalk with microglia.

The use of a SOX10 reporter toward ameliorating oligodendrocyte lineage differentiation from human induced pluripotent stem cells

Oligodendrocytes (OLs) are key players in the central nervous system, critical for the formation and maintenance of the myelin sheaths insulating axons, ensuring efficient neuronal communication. In the last decade, the use of human induced pluripotent stem cells (iPSCs) has become essential for recapitulating and understanding the differentiation and role of OLs in vitro. Current methods include overexpression of transcription factors for rapid OL generation, neglecting the complexity of OL lineage development. Alternatively, growth factor-based protocols offer physiological relevance but struggle with efficiency and cell heterogeneity. To address these issues, we created a novel SOX10-P2A-mOrange iPSC reporter line to track and purify oligodendrocyte precursor cells. Using this reporter cell line, we analyzed an existing differentiation protocol and shed light on the origin of glial cell heterogeneity. Additionally, we have modified the differentiation protocol, toward enhancing reproducibility, efficiency, and terminal maturity. Our approach not only advances OL biology but also holds promise to accelerate research and translational work with iPSC-derived OLs.

Recent advances and current challenges of new approach methodologies in developmental and adult neurotoxicity testing

Adult neurotoxicity (ANT) and developmental neurotoxicity (DNT) assessments aim to understand the adverse effects and underlying mechanisms of toxicants on the human nervous system. In recent years, there has been an increasing focus on the so-called new approach methodologies (NAMs). The Organization for Economic Co-operation and Development (OECD), together with European and American regulatory agencies, promote the use of validated alternative test systems, but to date, guidelines for regulatory DNT and ANT assessment rely primarily on classical animal testing. Alternative methods include both non-animal approaches and test systems on non-vertebrates (e.g., nematodes) or non-mammals (e.g., fish). Therefore, this review summarizes the recent advances of NAMs focusing on ANT and DNT and highlights the potential and current critical issues for the full implementation of these methods in the future. The status of the DNT in vitro battery (DNT IVB) is also reviewed as a first step of NAMs for the assessment of neurotoxicity in the regulatory context. Critical issues such as (i) the need for test batteries and method integration (from in silico and in vitro to in vivo alternatives, e.g., zebrafish, C. elegans) requiring interdisciplinarity to manage complexity, (ii) interlaboratory transferability, and (iii) the urgent need for method validation are discussed.

Research progress of autoimmune diseases based on induced pluripotent stem cells

Autoimmune diseases can damage specific or multiple organs and tissues, influence the quality of life, and even cause disability and death. A 'disease in a dish' can be developed based on patients-derived induced pluripotent stem cells (iPSCs) and iPSCs-derived disease-relevant cell types to provide a platform for pathogenesis research, phenotypical assays, cell therapy, and drug discovery. With rapid progress in molecular biology research methods including genome-sequencing technology, epigenetic analysis, '-omics' analysis and organoid technology, large amount of data represents an opportunity to help in gaining an in-depth understanding of pathological mechanisms and developing novel therapeutic strategies for these diseases. This paper aimed to review the iPSCs-based research on phenotype confirmation, mechanism exploration, drug discovery, and cell therapy for autoimmune diseases, especially multiple sclerosis, inflammatory bowel disease, and type 1 diabetes using iPSCs and iPSCs-derived cells.

Identity and Maturity of iPSC-Derived Oligodendrocytes in 2D and Organoid Systems

Oligodendrocytes originating in the brain and spinal cord as well as in the ventral and dorsal domains of the neural tube are transcriptomically and functionally distinct. These distinctions are also reflected in the ultrastructure of the produced myelin, and the susceptibility to myelin-related disorders, which highlights the significance of the choice of patterning protocols in the differentiation of induced pluripotent stem cells (iPSCs) into oligodendrocytes. Thus, our first goal was to survey the different approaches applied to the generation of iPSC-derived oligodendrocytes in 2D culture and in organoids, as well as reflect on how these approaches pertain to the regional and spatial fate of the generated oligodendrocyte progenitors and myelinating oligodendrocytes. This knowledge is increasingly important to disease modeling and future therapeutic strategies. Our second goal was to recap the recent advances in the development of oligodendrocyte-enriched organoids, as we explore their relevance to a regional specification alongside their duration, complexity, and maturation stages of oligodendrocytes and myelin biology. Finally, we discuss the shortcomings of the existing protocols and potential future explorations.

Nestorone (segesterone acetate) effects on neuroregeneration

Nestorone® (segesterone acetate) is a progestin with a chemical structure closely related to progesterone with high affinity and selectivity for the progesterone receptor without significant interaction with other steroid receptors. It has been developed for female and male contraception and is FDA-approved in a first long-acting contraceptive vaginal system for female contraception. Its safety has been extensively demonstrated in both preclinical and clinical studies for contraceptive indications. Nestorone was found to display neuroprotective and neuroregenerative activity in animal models of various central nervous system diseases, including multiple sclerosis, stroke, and amyotrophic lateral sclerosis. Reviewed herein are neuroprotective and myelin- regenerating properties of Nestorone in various animal models and its translational potential as a therapeutic agent for debilitating neurological diseases for which limited therapeutic options are available (Table 1).

Remyelination in the Central Nervous System

The inability of the mammalian central nervous system (CNS) to undergo spontaneous regeneration has long been regarded as a central tenet of neurobiology. However, while this is largely true of the neuronal elements of the adult mammalian CNS, save for discrete populations of granule neurons, the same is not true of its glial elements. In particular, the loss of oligodendrocytes, which results in demyelination, triggers a spontaneous and often highly efficient regenerative response, remyelination, in which new oligodendrocytes are generated and myelin sheaths are restored to denuded axons. Yet remyelination in humans is not without limitation, and a variety of demyelinating conditions are associated with sustained and disabling myelin loss. In this work, we will (1) review the biology of remyelination, including the cells and signals involved; (2) describe when remyelination occurs and when and why it fails, including the consequences of its failure; and (3) discuss approaches for therapeutically enhancing remyelination in demyelinating diseases of both children and adults, both by stimulating endogenous oligodendrocyte progenitor cells and by transplanting these cells into demyelinated brain.

Generation of a fluorescent oligodendrocyte reporter line in human induced pluripotent stem cells

Human brain organoids can serve as models to study myelination, a process orchestrated by oligodendrocytes. Real-time imaging provides new insights on the communication of oligodendrocytes with neurons as well as demyelination processes in patient derived organoids. PLP1, a prominent myelin protein within the central nervous system, is associated with demyelinating diseases, such as Pelizaeus-Merzbacher. In this study, we generated a stable PLP1-Citrine reporter line (fPLP1) in human induced pluripotent stem cells (iPSCs) by CRISPR/Cas9 editing. fPLP1 facilitates visualization of PLP1 expression in living brain organoids, allowing time-lapse imaging of pre-myelinating and myelinating oligodendrocytes.

Human stem cell transplantation models of Alzheimer's disease

Alzheimer's disease (AD) is the most frequent form of dementia. It is characterized by pronounced neuronal degeneration with formation of neurofibrillary tangles and deposition of amyloid β throughout the central nervous system. Animal models have provided important insights into the pathogenesis of AD and they have shown that different brain cell types including neurons, astrocytes and microglia have important functions in the pathogenesis of AD. However, there are difficulties in translating promising therapeutic observations in mice into clinical application in patients. Alternative models using human cells such as human induced pluripotent stem cells (iPSCs) may provide significant advantages, since they have successfully been used to model disease mechanisms in neurons and in glial cells in neurodegenerative diseases in vitro and in vivo. In this review, we summarize recent studies that describe the transplantation of human iPSC-derived neurons, astrocytes and microglial cells into the forebrain of mice to generate chimeric transplantation models of AD. We also discuss opportunities, challenges and limitations in using differentiated human iPSCs for in vivo disease modeling and their application for biomedical research.

Induced Pluripotent Stem Cells in Drug Discovery and Neurodegenerative Disease Modelling

Induced pluripotent stem cells (iPSCs) are derived from reprogrammed adult somatic cells. These adult cells are manipulated in vitro to express genes and factors essential for acquiring and maintaining embryonic stem cell (ESC) properties. This technology is widely applied in many fields, and much attention has been given to developing iPSC-based disease models to validate drug discovery platforms and study the pathophysiological molecular processes underlying disease onset. Especially in neurological diseases, there is a great need for iPSC-based technological research, as these cells can be obtained from each patient and carry the individual's bulk of genetic mutations and unique properties. Moreover, iPSCs can differentiate into multiple cell types. These are essential characteristics, since the study of neurological diseases is affected by the limited access to injury sites, the need for in vitro models composed of various cell types, the complexity of reproducing the brain's anatomy, the challenges of postmortem cell culture, and ethical issues. Neurodegenerative diseases strongly impact global health due to their high incidence, symptom severity, and lack of effective therapies. Recently, analyses using disease specific, iPSC-based models confirmed the efficacy of these models for testing multiple drugs. This review summarizes the advances in iPSC technology used in disease modelling and drug testing, with a primary focus on neurodegenerative diseases, including Parkinson's and Alzheimer's diseases.

Utilizing hiPSC-derived oligodendrocytes to study myelin pathophysiology in neuropsychiatric and neurodegenerative disorders

Oligodendrocytes play a crucial role in our central nervous system (CNS) by myelinating axons for faster action potential conduction, protecting axons from degeneration, structuring the position of ion channels, and providing nutrients to neurons. Oligodendrocyte dysfunction and/or dysmyelination can contribute to a range of neurodegenerative diseases and neuropsychiatric disorders such as Multiple Sclerosis (MS), Leukodystrophy (LD), Schizophrenia (SCZ), and Autism Spectrum Disorder (ASD). Common characteristics identified across these disorders were either an inability of oligodendrocytes to remyelinate after degeneration or defects in oligodendrocyte development and maturation. Unfortunately, the causal mechanisms of oligodendrocyte dysfunction are still uncertain, and therapeutic targets remain elusive. Many studies rely on the use of animal models to identify the molecular and cellular mechanisms behind these disorders, however, such studies face species-specific challenges and therefore lack translatability. The use of human induced pluripotent stem cells (hiPSCs) to model neurological diseases is becoming a powerful new tool, improving our understanding of pathophysiology and capacity to explore therapeutic targets. Here, we focus on the application of hiPSC-derived oligodendrocyte model systems to model disorders caused by oligodendrocyte dysregulation.

Stem and progenitor cell-based therapy of myelin disorders

Much of clinical neurology is concerned with diseases of-or involving-the brain's subcortical white matter. Common to these disorders is the loss of myelin, reflecting the elimination or dysfunction of oligodendrocytes and fibrous astrocytes. As such, the introduction of glial progenitor cells, which can give rise to new oligodendrocytes and astrocytes alike, may be a feasible strategy for treating a broad variety of conditions in which white matter loss is causally involved. This review first covers the sourcing and production of human glial progenitor cells, and the preclinical evidence for their efficacy in achieving myelin restoration in vivo. It then discusses both pediatric and adult disease targets for which transplanted glial progenitors may prove of therapeutic value, those challenges that remain in the clinical application of a glial cell replacement strategy, and the clinical endpoints by which the efficacy of this approach may be assessed.

Cell replacement therapy with stem cells in multiple sclerosis, a systematic review

Multiple sclerosis (MS) is a chronic inflammatory, autoimmune, and neurodegenerative disease of the central nervous system (CNS), characterized by demyelination and axonal loss. It is induced by attack of autoreactive lymphocytes on the myelin sheath and endogenous remyelination failure, eventually leading to accumulation of neurological disability. Disease-modifying agents can successfully address inflammatory relapses, but have low efficacy in progressive forms of MS, and cannot stop the progressive neurodegenerative process. Thus, the stem cell replacement therapy approach, which aims to overcome CNS cell loss and remyelination failure, is considered a promising alternative treatment. Although the mechanisms behind the beneficial effects of stem cell transplantation are not yet fully understood, neurotrophic support, immunomodulation, and cell replacement appear to play an important role, leading to a multifaceted fight against the pathology of the disease. The present systematic review is focusing on the efficacy of stem cells to migrate at the lesion sites of the CNS and develop functional oligodendrocytes remyelinating axons. While most studies confirm the improvement of neurological deficits after the administration of different stem cell types, many critical issues need to be clarified before they can be efficiently introduced into clinical practice.

Potential of Nano-Engineered Stem Cells in the Treatment of Multiple Sclerosis: A Comprehensive Review

Multiple sclerosis (MS) is a chronic and degrading autoimmune disorder mainly targeting the central nervous system, leading to progressive neurodegeneration, demyelination, and axonal damage. Current treatment options for MS are limited in efficacy, generally linked to adverse side effects, and do not offer a cure. Stem cell therapies have emerged as a promising therapeutic strategy for MS, potentially promoting remyelination, exerting immunomodulatory effects and protecting against neurodegeneration. Therefore, this review article focussed on the potential of nano-engineering in stem cells as a therapeutic approach for MS, focusing on the synergistic effects of combining stem cell biology with nanotechnology to stimulate the proliferation of oligodendrocytes (OLs) from neural stem cells and OL precursor cells, by manipulating neural signalling pathways-PDGF, BMP, Wnt, Notch and their essential genes such as Sox, bHLH, Nkx. Here we discuss the pathophysiology of MS, the use of various types of stem cells in MS treatment and their mechanisms of action. In the context of nanotechnology, we present an overview of its applications in the medical and research field and discuss different methods and materials used to nano-engineer stem cells, including surface modification, biomaterials and scaffolds, and nanoparticle-based delivery systems. We further elaborate on nano-engineered stem cell techniques, such as nano script, nano-exosome hybrid, nano-topography and their potentials in MS. The article also highlights enhanced homing, engraftment, and survival of nano-engineered stem cells, targeted and controlled release of therapeutic agents, and immunomodulatory and tissue repair effects with their challenges and limitations. This visual illustration depicts the process of utilizing nano-engineering in stem cells and exosomes for the purpose of delivering more accurate and improved treatments for Multiple Sclerosis (MS). This approach targets specifically the creation of oligodendrocytes, the breakdown of which is the primary pathological factor in MS.

Opportunities and challenges: mesenchymal stem cells in the treatment of multiple sclerosis

Multiple sclerosis (MS) was once considered an untreatable disease. Through years of research, many drugs have been discovered and are widely used for the treatment of MS. However, the current treatment can only alleviate the clinical symptoms of MS and has serious side effects. Mesenchymal stem cells (MSCs) provide neuroprotection by migrating to injured tissues, suppressing inflammation, and fostering neuronal repair. Therefore, MSCs therapy holds great promise for MS treatment. This review aimed to assess the feasibility and safety of use of MSCs in MS treatment as well as its development prospect in clinical treatment by analysing the existing clinical studies.

Developing a human iPSC-derived three-dimensional myelin spheroid platform for modeling myelin diseases

Myelin defects cause a collection of myelin disorders in the brain. The lack of human models has limited us from better understanding pathological mechanisms of myelin diseases. While human induced pluripotent stem cell (hiPSC)-derived spheroids or organoids have been used to study brain development and disorders, it has been difficult to recapitulate mature myelination in these structures. Here, we have developed a method to generate three-dimensional (3D) myelin spheroids from hiPSCs in a robust and reproducible manner. Using this method, we generated myelin spheroids from patient iPSCs to model Canavan disease (CD), a demyelinating disorder. By using CD patient iPSC-derived myelin spheroids treated with N-acetyl-aspartate (NAA), we were able to recapitulate key pathological features of the disease and show that high-level NAA is sufficient to induce toxicity on myelin sheaths. Our study has established a 3D human cellular platform to model human myelin diseases for mechanistic studies and drug discovery.

Oligodendrocyte Progenitor Cell Transplantation Ameliorates Preterm Infant Cerebral White Matter Injury in Rats Model

Background

Cerebral white matter injury (WMI) is the most common brain injury in preterm infants, leading to motor and developmental deficits often accompanied by cognitive impairment. However, there is no effective treatment. One promising approach for treating preterm WMI is cell replacement therapy, in which lost cells can be replaced by exogenous oligodendrocyte progenitor cells (OPCs).

Methods

This study developed a method to differentiate human neural stem cells (hNSCs) into human OPCs (hOPCs). The preterm WMI animal model was established in rats on postnatal day 3, and OLIG2+/NG2+/PDGFRα+/O4+ hOPCs were enriched and transplanted into the corpus callosum on postnatal day 10. Then, histological analysis and electron microscopy were used to detect lesion structure; behavioral assays were performed to detect cognitive function.

Results

Transplanted hOPCs survived and migrated throughout the major white matter tracts. Morphological differentiation of transplanted hOPCs was observed. Histological analysis revealed structural repair of lesioned areas. Re-myelination of the axons in the corpus callosum was confirmed by electron microscopy. The Morris water maze test revealed cognitive function recovery.

Conclusion

Our study showed that exogenous hOPCs could differentiate into CC1+ OLS in the brain of WMI rats, improving their cognitive functions.

Astrocytic response mediated by the CLU risk allele inhibits OPC proliferation and myelination in a human iPSC model

The C allele of rs11136000 variant in the clusterin (CLU) gene represents the third strongest known genetic risk factor for late-onset Alzheimer's disease. However, whether this single-nucleotide polymorphism (SNP) is functional and what the underlying mechanisms are remain unclear. In this study, the CLU rs11136000 SNP is identified as a functional variant by a small-scale CRISPR-Cas9 screen. Astrocytes derived from isogenic induced pluripotent stem cells (iPSCs) carrying the "C" or "T" allele of the CLU rs11136000 SNP exhibit different CLU expression levels. TAR DNA-binding protein-43 (TDP-43) preferentially binds to the "C" allele to promote CLU expression and exacerbate inflammation. The interferon response and CXCL10 expression are elevated in cytokine-treated C/C astrocytes, leading to inhibition of oligodendrocyte progenitor cell (OPC) proliferation and myelination. Accordingly, elevated CLU and CXCL10 but reduced myelin basic protein (MBP) expression are detected in human brains of C/C carriers. Our study uncovers a mechanism underlying reduced white matter integrity observed in the CLU rs11136000 risk "C" allele carriers.

Current advances in stem cell therapy in the treatment of multiple sclerosis

Multiple sclerosis (MS) is an inflammatory disease related to the central nervous system (CNS) with a significant global burden. In this illness, the immune system plays an essential role in its pathophysiology and progression. The currently available treatments are not recognized as curable options and, at best, might slow the progression of MS injuries to the CNS. However, stem cell treatment has provided a new avenue for treating MS. Stem cells may enhance CNS healing and regulate immunological responses. Likewise, stem cells can come from various sources, including adipose, neuronal, bone marrow, and embryonic tissues. Choosing the optimal cell source for stem cell therapy is still a difficult verdict. A type of stem cell known as mesenchymal stem cells (MSCs) is obtainable from different sources and has a strong immunomodulatory impact on the immune system. According to mounting data, the umbilical cord and adipose tissue may serve as appropriate sources for the isolation of MSCs. Human amniotic epithelial cells (hAECs), as novel stem cell sources with immune-regulatory effects, regenerative properties, and decreased antigenicity, can also be thought of as a new upcoming contender for MS treatment. Overall, the administration of stem cells in different sets of animal and clinical trials has shown immunomodulatory and neuroprotective results. Therefore, this review aims to discuss the different types of stem cells by focusing on MSCs and their mechanisms, which can be used to treat and improve the outcomes of MS disease.

Patient iPSC models reveal glia-intrinsic phenotypes in multiple sclerosis

Multiple sclerosis (MS) is considered an inflammatory and neurodegenerative disease of the central nervous system, typically resulting in significant neurological disability that worsens over time. While considerable progress has been made in defining the immune system's role in MS pathophysiology, the contribution of intrinsic CNS-cell dysfunction remains unclear. Here, we generated the largest reported collection of iPSC lines from people with MS spanning diverse clinical subtypes and differentiated them into glia-enriched cultures. Using single-cell transcriptomic profiling, we observed several distinguishing characteristics of MS cultures pointing to glia-intrinsic disease mechanisms. We found that iPSC-derived cultures from people with primary progressive MS contained fewer oligodendrocytes. Moreover, iPSC-oligodendrocyte lineage cells and astrocytes from people with MS showed increased expression of immune and inflammatory genes that match those of glial cells from MS postmortem brains. Thus, iPSC-derived MS models provide a unique platform for dissecting glial contributions to disease phenotypes independent of the peripheral immune system and identify potential glia-specific targets for therapeutic intervention.

Developing Hypoimmunogenic Human iPSC-Derived Oligodendrocyte Progenitor Cells as an Off-The-Shelf Cell Therapy for Myelin Disorders

Demyelinating disorders are among the most common and debilitating diseases in neurology. Canavan disease (CD) is a lethal demyelinating disease caused by mutation of the aspartoacylase (ASPA) gene, which leads to the accumulation of its substrate N-acetyl-l-aspartate (NAA), and consequently demyelination and vacuolation in the brain. In this study, hypoimmunogenic human induced pluripotent stem cell (iPSC)-derived oligodendrocyte progenitor cells (OPC) are developed from a healthy donor as an "off-the-shelf" cell therapy. Hypoimmunogenic iPSCs are generated through CRISPR/Cas9 editing of the human leukocyte antigen (HLA) molecules in healthy donor-derived iPSCs and differentiated into OPCs. The OPCs are engrafted into the brains of CD (nur7) mice and exhibit widespread distribution in the brain. The engrafted OPCs mature into oligodendrocytes that express the endogenous wildtype ASPA gene. Consequently, the transplanted mice exhibit elevated human ASPA expression and enzymatic activity and reduced NAA level in the brain. The transplanted OPCs are able to rescue major pathological features of CD, including defective myelination, extensive vacuolation, and motor function deficits. Moreover, the hypoimmunogenic OPCs exhibit low immunogenicity both in vitro and in vivo. The hypoimmunogenic OPCs can be used as "off-the-shelf" universal donor cells to treat various CD patients and many other demyelinating disorders, especially autoimmune demyelinating diseases, such as multiple sclerosis.

Directional induction of neural stem cells, a new therapy for neurodegenerative diseases and ischemic stroke

Due to the limited capacity of the adult mammalian brain to self-repair and regenerate, neurological diseases, especially neurodegenerative disorders and stroke, characterized by irreversible cellular damage are often considered as refractory diseases. Neural stem cells (NSCs) play a unique role in the treatment of neurological diseases for their abilities to self-renew and form different neural lineage cells, such as neurons and glial cells. With the increasing understanding of neurodevelopment and advances in stem cell technology, NSCs can be obtained from different sources and directed to differentiate into a specific neural lineage cell phenotype purposefully, making it possible to replace specific cells lost in some neurological diseases, which provides new approaches to treat neurodegenerative diseases as well as stroke. In this review, we outline the advances in generating several neuronal lineage subtypes from different sources of NSCs. We further summarize the therapeutic effects and possible therapeutic mechanisms of these fated specific NSCs in neurological disease models, with special emphasis on Parkinson's disease and ischemic stroke. Finally, from the perspective of clinical translation, we compare the strengths and weaknesses of different sources of NSCs and different methods of directed differentiation, and propose future research directions for directed differentiation of NSCs in regenerative medicine.

Neural lineage differentiation of human pluripotent stem cells: Advances in disease modeling

Brain diseases affect 1 in 6 people worldwide. These diseases range from acute neurological conditions such as stroke to chronic neurodegenerative disorders such as Alzheimer’s disease. Recent advancements in tissue-engineered brain disease models have overcome many of the different shortcomings associated with the various animal models, tissue culture models, and epidemiologic patient data that are commonly used to study brain disease. One innovative method by which to model human neurological disease is via the directed differentiation of human pluripotent stem cells (hPSCs) to neural lineages including neurons, astrocytes, and oligodendrocytes. Three-dimensional models such as brain organoids have also been derived from hPSCs, offering more physiological relevance due to their incorporation of various cell types. As such, brain organoids can better model the pathophysiology of neural diseases observed in patients. In this review, we will emphasize recent developments in hPSC-based tissue culture models of neurological disorders and how they are being used to create neural disease models.

TNF-α Preconditioning Promotes a Proangiogenic Phenotype in hiPSC-Derived Vascular Smooth Muscle Cells

Introduction

hiPSC-VSMCs have been suggested as therapeutic agents for wound healing and revascularization through the secretion of proangiogenic factors. However, methods of increasing cell paracrine secretion and survivability have thus far yielded inconsistent results. This study investigates the effect of pre-conditioning of hiPSC-VSMCs with TNF-α and their integration into 3D collagen scaffolds on cellular viability and secretome.

Methods

hiPSC-VSMCs were dual-plated in a 2D environment. TNF-α was introduced to one plate. Following incubation, cells from each plate were divided and added to type-I collagen scaffolds. TNF-α was introduced to two sets of scaffolds, one from each 2D plate. Following incubation, scaffolds were harvested for their media, tested for cell survivability, cytotoxicity, and imaged. Intra-media VEGF and bFGF levels were evaluated using ELISA testing.

Results

hiPSC-VSMCs exposed to TNF-α during collagen scaffold proliferation and preconditioning showed an increase in cell viability and less cytotoxicity compared to non-exposed cells and solely-preconditioned cells. Significant increases in bFGF expression were found in pre-conditioned cell groups with further increases found in cells subsequently exposed during intra-scaffold conditioning. A significant increase in VEGF expression was found in cell groups exposed during both pre-conditioning and intra-scaffold conditioning. Fibroblasts treated with any conditioned media demonstrated increased migration potential.

Conclusions

Conditioning hiPSC-VSMCs embedded in scaffolds with TNF-α improves cellular viability and increases the secretion of paracrine factors necessary for wound healing mechanisms such as migration.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-023-00764-0.

Inflammation in multiple sclerosis: consequences for remyelination and disease progression

Despite the large number of immunomodulatory or immunosuppressive treatments available to treat relapsing-remitting multiple sclerosis (MS), treatment of the progressive phase of the disease has not yet been achieved. This lack of successful treatment approaches is caused by our poor understanding of the mechanisms driving disease progression. Emerging concepts suggest that a combination of persisting focal and diffuse inflammation within the CNS and a gradual failure of compensatory mechanisms, including remyelination, result in disease progression. Therefore, promotion of remyelination presents a promising intervention approach. However, despite our increasing knowledge regarding the cellular and molecular mechanisms regulating remyelination in animal models, therapeutic increases in remyelination remain an unmet need in MS, which suggests that mechanisms of remyelination and remyelination failure differ fundamentally between humans and demyelinating animal models. New and emerging technologies now allow us to investigate the cellular and molecular mechanisms underlying remyelination failure in human tissue samples in an unprecedented way. The aim of this Review is to summarize our current knowledge regarding mechanisms of remyelination and remyelination failure in MS and in animal models of the disease, identify open questions, challenge existing concepts, and discuss strategies to overcome the translational roadblock in the field of remyelination-promoting therapies.

Understanding neural development and diseases using CRISPR screens in human pluripotent stem cell-derived cultures

The brain is arguably the most complex part of the human body in form and function. Much remains unclear about the molecular mechanisms that regulate its normal and pathological physiology. This lack of knowledge largely stems from the inaccessible nature of the human brain, and the limitation of animal models. As a result, brain disorders are difficult to understand and even more difficult to treat. Recent advances in generating human pluripotent stem cells (hPSCs)-derived 2-dimensional (2D) and 3-dimensional (3D) neural cultures have provided an accessible system to model the human brain. Breakthroughs in gene editing technologies such as CRISPR/Cas9 further elevate the hPSCs into a genetically tractable experimental system. Powerful genetic screens, previously reserved for model organisms and transformed cell lines, can now be performed in human neural cells. Combined with the rapidly expanding single-cell genomics toolkit, these technological advances culminate to create an unprecedented opportunity to study the human brain using functional genomics. This review will summarize the current progress of applying CRISPR-based genetic screens in hPSCs-derived 2D neural cultures and 3D brain organoids. We will also evaluate the key technologies involved and discuss their related experimental considerations and future applications.

High-throughput screening for myelination promoting compounds using human stem cell-derived oligodendrocyte progenitor cells

Promoting myelination capacity of endogenous oligodendrocyte precursor cells (OPCs) is a promising therapeutic approach for CNS demyelinating disorders such as Multiple Sclerosis (MS). To aid in the discovery of myelination-promoting compounds, we generated a genome-engineered human pluripotent stem cell (hPSC) line that consists of three reporters: identification-and-purification tag, GFP, and secreted-NanoLuc, driven by the endogenous PDGFRA, PLP1, and MBP genes, respectively. Using this cell line, we established a high-throughput drug screening platform and performed a small-molecule screen, which identified at least two myelination-promoting small-molecule (Ro1138452 and SR2211) that target prostacyclin (IP) receptor and retinoic acid receptor-related orphan receptor γ (RORγ), respectively. Single-cell-transcriptomic analysis of differentiating OPCs treated with these molecules further confirmed that they promote oligodendrocyte differentiation and revealed several pathways that are potentially modulated by them. The molecules and their target pathways provide promising targets for the possible development of remyelination-based therapy for MS and other demyelinating disorders.

Cerebral organoids in primary progressive multiple sclerosis reveal stem cell and oligodendrocyte differentiation defect

Multiple sclerosis (MS) is an auto-immune inflammatory disorder affecting the central nervous system. The cause of the disease is unknown but both genetic and environmental factors are implicated in the pathogenesis. We derived cerebral organoids from induced pluripotent stem cells (iPSC) of healthy control subjects as well as from primary progressive MS (PPMS), secondary progressive MS (SPMS) and relapsing remitting MS (RRMS) patients to better understand the pathologic basis of the varied clinical phenotypic expressions of MS. In MS organoids, most notably in PPMS, we observed a decrease of proliferation marker Ki67 and a reduction of the SOX2+ stem cell pool associated with an increased expression of neuronal markers CTIP2 and TBR1 as well as a strong decrease of oligodendrocyte differentiation. This dysregulation of the stem cell pool is associated with a decreased expression of the cell cycle inhibitor p21. Our findings show that the genetic background of a patient can directly alter stem cell function, provides new insights on the innate cellular dysregulation in MS and identifies p21 pathway as a new potential target for therapeutic strategies in MS.

Role of curcumin and its nanoformulations in the treatment of neurological diseases through the effects on stem cells

Curcumin from turmeric is a natural phenolic compound with a promising potential to regulate fundamental processes involved in neurological diseases, including inflammation, oxidative stress, protein aggregation, and apoptosis at the molecular level. In this regard, employing nanoformulation can improve curcumin efficiency by reducing its limitations, such as low bioavailability. Besides curcumin, growing data suggest that stem cells are a noteworthy candidate for neurodegenerative disorders therapy due to their anti-inflammatory, anti-oxidative, and neuronal-differentiation properties, which result in neuroprotection. Curcumin and stem cells have similar neurogenic features and can be co-administered in a cell-drug delivery system to achieve better combination therapeutic outcomes for neurological diseases. Based on the evidence, curcumin can induce the neuroprotective activity of stem cells by modulating their related signalling pathways. The present review is about the role of curcumin and its nanoformulations in the improvement of neurological diseases alone and through the effect on different categories of stem cells by discussing the underlying mechanisms to provide a roadmap for future investigations.

Therapeutical growth in oligodendroglial fate induction via transdifferentiation of stem cells for neuroregenerative therapy

The merits of stem cell therapy and research are undisputed due to their widespread usage in the treatment of neurodegenerative diseases and demyelinating disorders. Cell replacement therapy especially revolves around stem cells and their induction into different cell lineages both adult and progenitor - belonging to each germ layer, prior to transplantation or disease modeling studies. The nervous system is abundant in glial cells and among these are oligodendrocytes capable of myelinating new-born neurons and remyelination of axons with lost or damaged myelin sheath. But demyelinating diseases generate tremendous deficit between myelin loss and recovery. To compensate for this loss, analyze the defects in remyelination mechanisms as well as to trigger full recovery in such patients mesenchymal stem cells (MSCs) have been induced to transdifferentiate into oligodendrocytes. But such experiments are riddled with problems like prolonged, tenuous and complicated protocols that stretch longer than the time taken for the spread of demyelination-associated after-effects. This review delves into such protocols and the combinations of different molecules and factors that have been recruited to derive bona fide oligodendrocytes from in vitro differentiation of embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs) and MSCs with special focus on MSC-derived oligodendrocytes.

Modeling Human Brain Tumors and the Microenvironment Using Induced Pluripotent Stem Cells

Brain cancer is a group of diverse and rapidly growing malignancies that originate in the central nervous system (CNS) and have a poor prognosis. The complexity of brain structure and function makes brain cancer modeling extremely difficult, limiting pathological studies and therapeutic developments. Advancements in human pluripotent stem cell technology have opened a window of opportunity for brain cancer modeling, providing a wealth of customizable methods to simulate the disease in vitro. This is achieved with the advent of genome editing and genetic engineering technologies that can simulate germline and somatic mutations found in human brain tumors. This review investigates induced pluripotent stem cell (iPSC)-based approaches to model human brain cancer. The applications of iPSCs as renewable sources of individual brain cell types, brain organoids, blood-brain barrier (BBB), and brain tumor models are discussed. The brain tumor models reviewed are glioblastoma and medulloblastoma. The iPSC-derived isogenic cells and three-dimensional (3D) brain cancer organoids combined with patient-derived xenografts will enhance future compound screening and drug development for these deadly human brain cancers.

Cell reprogramming for oligodendrocytes: A review of protocols and their applications to disease modeling and cell-based remyelination therapies

Oligodendrocytes are a type of glial cells that produce a lipid-rich membrane called myelin. Myelin assembles into a sheath and lines neuronal axons in the brain and spinal cord to insulate them. This not only increases the speed and efficiency of nerve signal transduction but also protects the axons from damage and degradation, which could trigger neuronal cell death. Demyelination, which is caused by a loss of myelin and oligodendrocytes, is a prominent feature of many neurological conditions, including Multiple sclerosis (MS), spinal cord injuries (SCI), and leukodystrophies. Demyelination is followed by a time of remyelination mediated by the recruitment of endogenous oligodendrocyte precursor cells, their migration to the injury site, and differentiation into myelin-producing oligodendrocytes. Unfortunately, endogenous remyelination is not sufficient to overcome demyelination, which explains why there are to date no regenerative-based treatments for MS, SCI, or leukodystrophies. To better understand the role of oligodendrocytes and develop cell-based remyelination therapies, human oligodendrocytes have been derived from somatic cells using cell reprogramming. This review will detail the different cell reprogramming methods that have been developed to generate human oligodendrocytes and their applications to disease modeling and cell-based remyelination therapies. Recent developments in the field have seen the derivation of brain organoids from pluripotent stem cells, and protocols have been devised to incorporate oligodendrocytes within the organoids, which will also be reviewed.

Cell-based experimental strategies for myelin repair in multiple sclerosis

Multiple sclerosis (MS) is an autoimmune demyelinating disorder of the central nervous system (CNS), diagnosed at a mean age of 32 years. CNS glia are crucial players in the onset of MS, primarily involving astrocytes and microglia that can cause/allow massive oligodendroglial cells death, without immune cell infiltration. Current therapeutic approaches are aimed at modulating inflammatory reactions during relapsing episodes, but lack the ability to induce very significant repair mechanisms. In this review article, different experimental approaches based mainly on the application of different cell types as therapeutic strategies applied for the induction of myelin repair and/or the amelioration of the disease are discussed. Regarding this issue, different cell sources were applied in various experimental models of MS, with different results, both in significant improvements in remyelination and the reduction of neuroinflammation and glial activation, or in neuroprotection. All cell types tested have advantages and disadvantages, which makes it difficult to choose a better option for therapeutic application in MS. New strategies combining cell-based treatment with other applications would result in further improvements and would be good candidates for MS cell therapy and myelin repair.

Applications of Induced Pluripotent Stem Cell-Derived Glia in Brain Disease Research and Treatment

Glia are integral components of neural networks and are crucial in both physiological functions and pathological processes of the brain. Many brain diseases involve glial abnormalities, including inflammatory changes, mitochondrial damage, calcium signaling disturbance, hemichannel opening, and loss of glutamate transporters. Induced pluripotent stem cell (iPSC)-derived glia provide opportunities to study the contributions of glia in human brain diseases. These cells have been used for human disease modeling as well as generating new therapies. This chapter introduces glial involvement in brain diseases, then summarizes different methods of generating iPSC-derived glia disease models of these cells. Finally, strategies for treating disease using iPSC-derived glia are discussed. The goal of this chapter is to provide an overview and shed light on the applications of iPSC-derived glia in brain disease research and treatment.

The Journey of iPSC-derived OPCs in Demyelinating Disorders: From In vitro Generation to In vivo Transplantation

Loss of myelination is common among neurological diseases. It causes significant disability, even death, if it is not treated instantly. Different mechanisms involve the pathophysiology of demyelinating diseases, such as genetic background, infectious, and autoimmune inflammation. Recently, regenerative medicine and stem cell therapy have shown to be promising for the treatment of demyelinating disorders. Stem cells, including embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and adult stem cells (ASCs), can differentiate into oligodendrocyte progenitor cells (OPCs), which may convert to oligodendrocytes (OLs) and recover myelination. IPSCs provide an endless source for OPCs generation. However, the restricted capacity of proliferation, differentiation, migration, and myelination of iPSC-derived OPCs is a notable gap for future studies. In this article, we have first reviewed stem cell therapy in demyelinating diseases. Secondly, methods of different protocols have been discussed among in vitro and in vivo studies on iPSC-derived OPCs to contrast OPCs' transplantation efficacy. Lastly, we have reviewed the results of iPSCs-derived OLs production in each demyelination model.

Intrinsic blood-brain barrier dysfunction contributes to multiple sclerosis pathogenesis

Blood-brain barrier (BBB) breakdown and immune cell infiltration into the CNS are early hallmarks of multiple sclerosis (MS). The mechanisms leading to BBB dysfunction are incompletely understood and generally thought to be a consequence of neuroinflammation. Here, we have challenged this view and asked if intrinsic alterations in the BBB of MS patients contribute to MS pathogenesis. To this end, we made use of human induced pluripotent stem cells derived from healthy controls and MS patients and differentiated them into brain microvascular endothelial cell (BMEC)-like cells as in vitro model of the BBB. MS-derived BMEC-like cells showed impaired junctional integrity, barrier properties and efflux pump activity when compared to healthy controls. Also, MS-derived BMEC-like cells displayed an inflammatory phenotype with increased adhesion molecule expression and immune cell interactions. Activation of Wnt/β-catenin signalling in MS-derived endothelial progenitor cells enhanced barrier characteristics and reduced the inflammatory phenotype. Our study provides evidence for an intrinsic impairment of BBB function in MS patients that can be modelled in vitro. Human iPSC-derived BMEC-like cells are thus suitable to explore the molecular underpinnings of BBB dysfunction in MS and will assist in the identification of potential novel therapeutic targets for BBB stabilization.

Pluripotent stem cell strategies for rebuilding the human brain

Neurodegenerative disorders have been extremely challenging to treat with traditional drug-based approaches and curative therapies are lacking. Given continued progress in stem cell technologies, cell replacement strategies have emerged as concrete and potentially viable therapeutic options. In this review, we cover advances in methods used to differentiate human pluripotent stem cells into several highly specialized types of neurons, including cholinergic, dopaminergic, and motor neurons, and the potential clinical applications of stem cell-derived neurons for common neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, ataxia, and amyotrophic lateral sclerosis. Additionally, we summarize cellular differentiation techniques for generating glial cell populations, including oligodendrocytes and microglia, and their conceivable translational roles in supporting neural function. Clinical trials of specific cell replacement therapies in the nervous system are already underway, and several attractive avenues in regenerative medicine warrant further investigation.

Building in vitro models of the brain to understand the role of APOE in Alzheimer's disease

Alzheimer's disease (AD) is a devastating, complex, and incurable disease that represents an increasingly problematic global health issue. The etiology of sporadic AD that accounts for a vast majority of cases remains poorly understood, with no effective therapeutic interventions. Genetic studies have identified AD risk genes including the most prominent, APOE, of which the ɛ4 allele increases risk in a dose-dependent manner. A breakthrough discovery enabled the creation of human induced pluripotent stem cells (hiPSCs) that can be differentiated into various brain cell types, facilitating AD research in genetically human models. Herein, we provide a brief background on AD in the context of APOE susceptibility and feature work employing hiPSC-derived brain cell and tissue models to interrogate the contribution of APOE in driving AD pathology. Such models have delivered crucial insights into cellular mechanisms and cell type-specific roles underlying the perturbed biological functions that trigger pathogenic cascades and propagate neurodegeneration. Collectively, hiPSC-based models are envisioned to be an impactful platform for uncovering fundamental AD understanding, with high translational value toward AD drug discovery and testing.