iPS-derived neural progenitor cells from PPMS patients reveal defect in myelin injury response

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.

Glial-restricted progenitor cells: a cure for diseased brain?

The central nervous system (CNS) is home to neuronal and glial cells. Traditionally, glia was disregarded as just the structural support across the brain and spinal cord, in striking contrast to neurons, always considered critical players in CNS functioning. In modern times this outdated dogma is continuously repelled by new evidence unravelling the importance of glia in neuronal maintenance and function. Therefore, glia replacement has been considered a potentially powerful therapeutic strategy. Glial progenitors are at the center of this hope, as they are the source of new glial cells. Indeed, sophisticated experimental therapies and exciting clinical trials shed light on the utility of exogenous glia in disease treatment. Therefore, this review article will elaborate on glial-restricted progenitor cells (GRPs), their origin and characteristics, available sources, and adaptation to current therapeutic approaches aimed at various CNS diseases, with particular attention paid to myelin-related disorders with a focus on recent progress and emerging concepts. The landscape of GRP clinical applications is also comprehensively presented, and future perspectives on promising, GRP-based therapeutic strategies for brain and spinal cord diseases are described in detail.

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.

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.

Miconazole-like Scaffold is a Promising Lead for Naegleria fowleri-Specific CYP51 Inhibitors

Developing drugs for brain infection by Naegleria fowleri is an unmet medical need. We used a combination of cheminformatics, target-, and phenotypic-based drug discovery methods to identify inhibitors that target an essential N. fowleri enzyme, sterol 14-demethylase (NfCYP51). A total of 124 compounds preselected in silico were tested against N. fowleri. Nine primary hits with EC50 ≤ 10 μM were phenotypically identified. Cocrystallization with NfCYP51 focused attention on one primary hit, miconazole-like compound 2a. The S-enantiomer of 2a produced a 1.74 Å cocrystal structure. A set of analogues was then synthesized and evaluated to confirm the superiority of the S-configuration over the R-configuration and the advantage of an ether linkage over an ester linkage. The two compounds, S-8b and S-9b, had an improved EC50 and KD compared to 2a. Importantly, both were readily taken up into the brain. The brain-to-plasma distribution coefficient of S-9b was 1.02 ± 0.12, suggesting further evaluation as a lead for primary amoebic meningoencephalitis.

Insights on therapeutic potential of clemastine in neurological disorders

Clemastine, a Food and Drug Administration (FDA)-approved compound, is recognized as a first-generation, widely available antihistamine that reduces histamine-induced symptoms. Evidence has confirmed that clemastine can transport across the blood-brain barrier and act on specific neurons and neuroglia to exert its protective effect. In this review, we summarize the beneficial effects of clemastine in various central nervous system (CNS) disorders, including neurodegenerative disease, neurodevelopmental deficits, brain injury, and psychiatric disorders. Additionally, we highlight key cellular links between clemastine and different CNS cells, in particular in oligodendrocyte progenitor cells (OPCs), oligodendrocytes (OLs), microglia, and neurons.

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.

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.

Epigenetic clock indicates accelerated aging in glial cells of progressive multiple sclerosis patients

Background

Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative disease of the central nervous system (CNS) characterized by irreversible disability at later progressive stages. A growing body of evidence suggests that disease progression depends on age and inflammation within the CNS. We aimed to investigate epigenetic aging in bulk brain tissue and sorted nuclei from MS patients using DNA methylation-based epigenetic clocks.

Methods

We applied Horvath’s multi-tissue and Shireby’s brain-specific Cortical clock on bulk brain tissue (n = 46), sorted neuronal (n = 54), and glial nuclei (n = 66) from post-mortem brain tissue of progressive MS patients and controls.

Results

We found a significant increase in age acceleration residuals, corresponding to 3.6 years, in glial cells of MS patients compared to controls (P = 0.0024) using the Cortical clock, which held after adjustment for covariates (P_adj = 0.0263). The 4.8-year age acceleration found in MS neurons (P = 0.0054) did not withstand adjustment for covariates and no significant difference in age acceleration residuals was observed in bulk brain tissue between MS patients and controls.

Conclusion

While the findings warrant replication in larger cohorts, our study suggests that glial cells of progressive MS patients exhibit accelerated biological aging.

The Cellular Senescence Factor Extracellular HMGB1 Directly Inhibits Oligodendrocyte Progenitor Cell Differentiation and Impairs CNS Remyelination

HMGB1 is a highly conserved, ubiquitous protein in eukaryotic cells. HMGB1 is normally localized to the nucleus, where it acts as a chromatin associated non-histone binding protein. In contrast, extracellular HMGB1 is an alarmin released by stressed cells to act as a danger associated molecular pattern (DAMP). We have recently determined that progenitor cells from multiple sclerosis patients exhibit a cellular senescent phenotype and release extracellular HMGB1 which directly impaired the maturation of oligodendrocyte progenitor cells (OPCs) to myelinating oligodendrocytes (OLs). Herein, we report that administration of recombinant HMGB1 into the spinal cord at the time of lysolecithin administration resulted in arrest of OPC differentiation in vivo, and a profound impairment of remyelination. To define the receptor by which extracellular HMGB1 mediates its inhibitory influence on OPCs to impair OL differentiation, we tested selective inhibitors against the four primary receptors known to mediate the effects of HMGB1, the toll-like receptors (TLRs)-2, -4, -9 or the receptor for advanced glycation end-products (RAGE). We found that inhibition of neither TLR9 nor RAGE increased OL differentiation in the presence of HMGB1, while inhibition of TLR4 resulted in partial restoration of OL differentiation and inhibiting TLR2 fully restored differentiation of OLs in the presence of HMGB1. Analysis of transcriptomic data (RNAseq) from OPCs identified an overrepresentation of NFκB regulated genes in OPCs when in the presence of HMGB1. We found that application of HMGB1 to OPCs in culture resulted in a rapid and concentration dependent shift in NFκB nuclear translocation which was also attenuated with coincident TLR2 inhibition. These data provide new information on how extracellular HMGB1 directly affects the differentiation potential of OPCs. Recent and past evidence for elevated HMGB1 released from senescent progenitor cells within demyelinated lesions in the MS brain suggests that a greater understanding of how this molecule acts on OPCs may unfetter the endogenous remyelination potential in MS.

Molecular Mechanisms of Immunosenescene and Inflammaging: Relevance to the Immunopathogenesis and Treatment of Multiple Sclerosis

Aging is characterized, amongst other features, by a complex process of cellular senescence involving both innate and adaptive immunity, called immunosenescence and associated to inflammaging, a low-grade chronic inflammation. Both processes fuel each other and partially explain increasing incidence of cancers, infections, age-related autoimmunity, and vascular disease as well as a reduced response to vaccination. Multiple sclerosis (MS) is a lifelong disease, for which considerable progress in disease-modifying therapies (DMTs) and management has improved long-term survival. However, disability progression, increasing with age and disease duration, remains. Neurologists are now involved in caring for elderly MS patients, with increasing comorbidities. Aging of the immune system therefore has relevant implications for MS pathogenesis, response to DMTs and the risks mediated by these treatments. We propose to review current evidence regarding markers and molecular mechanisms of immunosenescence and their relevance to understanding MS pathogenesis. We will focus on age-related changes in the innate and adaptive immune system in MS and other auto-immune diseases, such as systemic lupus erythematosus and rheumatoid arthritis. The consequences of these immune changes on MS pathology, in interaction with the intrinsic aging process of central nervous system resident cells will be discussed. Finally, the impact of immunosenescence on disease evolution and on the safety and efficacy of current DMTs will be presented.

Establishment of Human Induced Pluripotent Stem Cells from Multiple Sclerosis Patients

The patient-derived iPSC lines provide valuable resources as these cells can be utilized to generate human cell types relevant to the disease of interest. In this context, human iPSC-based model systems are particularly useful for neurological diseases as the neuron and glial cell types affected by such diseases are difficult to obtain. Multiple sclerosis is a demyelinating central nervous system disease characterized by inflammation and eventually axonal damage. iPS cells generated from MS patients may allow for unique approaches for studying the disease in a species-specific manner, with a potentially limitless supply of patients' own glial and neuronal cells differentiated from the iPSCs. Here we describe the detailed protocol for establishing iPSCs from peripheral blood mononuclear cells that we have utilized to model multiple sclerosis. We particularly focused on optimized and cost-effective procedures using the integration-free Sendai virus-based reprogramming method for the generation and characterization of MS iPSCs.

Human-Induced Pluripotent Stem Cell-Based Models for Studying Sex-Specific Differences in Neurodegenerative Diseases

The prevalence of neurodegenerative diseases is steadily increasing worldwide, and epidemiological studies strongly suggest that many of the diseases are sex-biased. It has long been suggested that biological sex differences are crucial for neurodegenerative diseases; however, how biological sex affects disease initiation, progression, and severity is not well-understood. Sex is a critical biological variable that should be taken into account in basic research, and this review aims to highlight the utility of human-induced pluripotent stem cells (iPSC)-derived models for studying sex-specific differences in neurodegenerative diseases, with advantages and limitations. In vitro systems utilizing species-specific, renewable, and physiologically relevant cell sources can provide powerful platforms for mechanistic studies, toxicity testings, and drug discovery. Matched healthy, patient-derived, and gene-corrected human iPSCs, from both sexes, can be utilized to generate neuronal and glial cell types affected by specific neurodegenerative diseases to study sex-specific differences in two-dimensional (2D) and three-dimensional (3D) human culture systems. Such relatively simple and well-controlled systems can significantly contribute to the elucidation of molecular mechanisms underlying sex-specific differences, which can yield effective, and potentially sex-based strategies, against neurodegenerative diseases.

Novel in vitro Experimental Approaches to Study Myelination and Remyelination in the Central Nervous System

Myelin is the lipidic insulating structure enwrapping axons and allowing fast saltatory nerve conduction. In the central nervous system, myelin sheath is the result of the complex packaging of multilamellar extensions of oligodendrocyte (OL) membranes. Before reaching myelinating capabilities, OLs undergo a very precise program of differentiation and maturation that starts from OL precursor cells (OPCs). In the last 20 years, the biology of OPCs and their behavior under pathological conditions have been studied through several experimental models. When co-cultured with neurons, OPCs undergo terminal maturation and produce myelin tracts around axons, allowing to investigate myelination in response to exogenous stimuli in a very simple in vitro system. On the other hand, in vivo models more closely reproducing some of the features of human pathophysiology enabled to assess the consequences of demyelination and the molecular mechanisms of remyelination, and they are often used to validate the effect of pharmacological agents. However, they are very complex, and not suitable for large scale drug discovery screening. Recent advances in cell reprogramming, biophysics and bioengineering have allowed impressive improvements in the methodological approaches to study brain physiology and myelination. Rat and mouse OPCs can be replaced by human OPCs obtained by induced pluripotent stem cells (iPSCs) derived from healthy or diseased individuals, thus offering unprecedented possibilities for personalized disease modeling and treatment. OPCs and neural cells can be also artificially assembled, using 3D-printed culture chambers and biomaterial scaffolds, which allow modeling cell-to-cell interactions in a highly controlled manner. Interestingly, scaffold stiffness can be adopted to reproduce the mechanosensory properties assumed by tissues in physiological or pathological conditions. Moreover, the recent development of iPSC-derived 3D brain cultures, called organoids, has made it possible to study key aspects of embryonic brain development, such as neuronal differentiation, maturation and network formation in temporal dynamics that are inaccessible to traditional in vitro cultures. Despite the huge potential of organoids, their application to myelination studies is still in its infancy. In this review, we shall summarize the novel most relevant experimental approaches and their implications for the identification of remyelinating agents for human diseases such as multiple sclerosis.

Potential of nafimidone derivatives against co-morbidities of epilepsy: In vitro, in vivo, and in silico investigations

Nafimidone is known for its clinical antiepileptic effects and alcohol derivatives of nafimidone were reported be potent anticonvulsants. These compounds are structurally similar to miconazole, which is known to inhibit cholinesterases, protect neurons, and ameliorate cognitive decline. Herein, we aimed to reveal the potential of three nafimidone alcohol esters (5 g, 5i, and 5 k), which were previously reported for their anticonvulsant effects, against co-morbidities of epilepsy such as inflammatory and neuropathic pain, cognitive and behavioral deficits, and neuron death, and understand their roles in related pathways such as γ-butyric acid type A (GABA_A ) receptor and cholinesterases using in vitro, in vivo and in silico methods. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test was used for cytotoxicity evaluation, hippocampal slice culture assay for neuroprotection, formalin test for acute and inflammatory pain, sciatic ligation for neuropathic pain, Morris water maze and open field locomotor tasks for cognitive and behavioral deficits, radioligand binding for GABA_A receptor affinity, spectrophotometric methods for cholinesterase inhibition in vitro, and molecular docking in silico. The compounds were non-toxic to fibroblast cells. 5 k was neuroprotective against kainic acid-induced neuron death. 5i reduced pain response of mice in both the acute and the inflammatory phases. 5i improved survival upon status epilepticus. The compounds showed no affinity to GABA_A receptor but inhibited acetylcholinesterase, 5 k also inhibited butyrylcholinesterase. The compounds were predicted to interact mainly with the peripheric anionic site of cholinesterase enzymes. The title compounds showed neuroprotective, analgesic, and cholinesterase inhibitory effects, thus they bear promise against certain co-morbidities of epilepsy with neurological insults.

Stem Cell Therapies for Progressive Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system characterized by demyelination and axonal degeneration. MS patients typically present with a relapsing-remitting (RR) disease course, manifesting as sporadic attacks of neurological symptoms including ataxia, fatigue, and sensory impairment. While there are several effective disease-modifying therapies able to address the inflammatory relapses associated with RRMS, most patients will inevitably advance to a progressive disease course marked by a gradual and irreversible accrual of disabilities. Therapeutic intervention in progressive MS (PMS) suffers from a lack of well-characterized biological targets and, hence, a dearth of successful drugs. The few medications approved for the treatment of PMS are typically limited in their efficacy to active forms of the disease, have little impact on slowing degeneration, and fail to promote repair. In looking to address these unmet needs, the multifactorial therapeutic benefits of stem cell therapies are particularly compelling. Ostensibly providing neurotrophic support, immunomodulation and cell replacement, stem cell transplantation holds substantial promise in combatting the complex pathology of chronic neuroinflammation. Herein, we explore the current state of preclinical and clinical evidence supporting the use of stem cells in treating PMS and we discuss prospective hurdles impeding their translation into revolutionary regenerative medicines.

Human Glial Progenitor Cells Effectively Remyelinate the Demyelinated Adult Brain

Neonatally transplanted human glial progenitor cells (hGPCs) can myelinate the brains of myelin-deficient shiverer mice, rescuing their phenotype and survival. Yet, it has been unclear whether implanted hGPCs are similarly able to remyelinate the diffusely demyelinated adult CNS. We, therefore, ask if hGPCs could remyelinate both congenitally hypomyelinated adult shiverers and normal adult mice after cuprizone demyelination. In adult shiverers, hGPCs broadly disperse and differentiate as myelinating oligodendrocytes after subcortical injection, improving both host callosal conduction and ambulation. Implanted hGPCs similarly remyelinate denuded axons after cuprizone demyelination, whether delivered before or after demyelination. RNA sequencing (RNA-seq) of hGPCs back from cuprizone-demyelinated brains reveals their transcriptional activation of oligodendrocyte differentiation programs, while distinguishing them from hGPCs not previously exposed to demyelination. These data indicate the ability of transplanted hGPCs to disperse throughout the adult CNS, to broadly myelinate regions of dysmyelination, and also to be recruited as myelinogenic oligodendrocytes later in life, upon demyelination-associated demand.

Generation of RRMS and PPMS specific iPSCs as a platform for modeling Multiple Sclerosis

The advent of cellular reprogramming technology converting somatic cells into induced pluripotent stem cells (iPSCs) has revolutionized our understandings of neurodegenerative diseases that are otherwise hard to access and model. Multiple Sclerosis (MS) is a chronic demyelinating, inflammatory disease of central nervous system eventually causing neuronal death and accompanied disabilities. Here, we report the generation of several relapsing-remitting MS (RRMS) and primary progressive MS (PPMS) iPSC lines from MS patients along with their age matched healthy controls from peripheral blood mononuclear cells (PBMC). These patient specific iPSC lines displayed characteristic embryonic stem cell (ESC) morphology and exhibited pluripotency marker expression. Moreover, these MS iPSC lines were successfully differentiated into neural progenitor cells (NPC) after subjecting to neural induction. Furthermore, we identified the elevated expression of cellular senescence hallmarks in RRMS and PPMS neural progenitors unveiling a novel drug target avenue of MS pathophysiology. Thus, our study altogether offers both RRMS and PPMS iPSC cellular models as a good tool for better understanding of MS pathologies and drug testing.

Diversity and Function of Glial Cell Types in Multiple Sclerosis

Glial subtype diversity is an emerging topic in neurobiology and immune-mediated neurological diseases such as multiple sclerosis (MS). We discuss recent conceptual and technological advances that allow a better understanding of the transcriptomic and functional heterogeneity of oligodendrocytes (OLs), astrocytes, and microglial cells under inflammatory-demyelinating conditions. Recent single cell transcriptomic studies suggest the occurrence of novel homeostatic and reactive glial subtypes and provide insight into the molecular events during disease progression. Multiplexed RNA in situ hybridization has enabled 'mapping back' dysregulated gene expression to glial subtypes within the MS lesion microenvironment. These findings suggest novel homeostatic and reactive glial-cell-type functions both in immune-related processes and neuroprotection relevant to understanding the pathology of MS.

Cuprizone-Dependent De/Remyelination Responses and Functional Correlates in Mouse Strains Adopted to Model Relapsing, Chronic and Progressive Experimental Autoimmune Encephalomyelitis

NOD mice represent a unique strain that recapitulates some aspects of progressive MS when subjected to experimental autoimmune encephalomyelitis (EAE). It is unknown, however, whether a proneness to demyelination and/or defect in remyelination contribute to disease progression in NOD mice. Answering to this question might help deciphering the molecular and cellular events underpinning disease evolution in progressive MS. Here, we compared the cuprizone-dependent demyelination and remyelination responses, as well as their functional correlates, in NOD, C57BL/6, and SJL mice typically adopted to model progressive, chronic or relapsing EAE. We report that demyelination occurred to a similar extent in the three mice strains, and that in none of them there was evidence of axonal degeneration during prolonged demyelination. Moreover, immunostaining for GFAP⁺ astrocytes, Iba1⁺ microglia, and NG2⁺ oligodendrocyte precursor cells similarly increased in the 3 mouse strains after cuprizone exposure. The mice underwent concomitant and complete remyelination 2 weeks after cuprizone withdrawal. On a functional level, NOD mice showed the earliest reduction of spontaneous motility and full recovery, but no impairment of motor skill. Conversely, C57BL/6 animals showed phasic reduction of both spontaneous motility and motor skill. Lastly, SJL mice presented the most severe neurological impairment with long-lasting reduction of spontaneous motility and motor skill. Overall, data suggest that the unique feature of EAE progression in NOD mice is not due to proneness to demyelination or intrinsic defects in myelin formation. Findings also unravel important functional differences in the response of the three mouse stains to cuprizone that can be harnessed to design and interpret future experiments.

Multiple sclerosis iPS-derived oligodendroglia conserve their properties to functionally interact with axons and glia in vivo

Remyelination failure in multiple sclerosis (MS) is associated with a migration/differentiation block of oligodendroglia. The reason for this block is highly debated. It could result from disease-related extrinsic or intrinsic regulators in oligodendroglial biology. To avoid confounding immune-mediated extrinsic effect, we used an immune-deficient mouse model to compare induced pluripotent stem cell-derived oligodendroglia from MS and healthy donors following engraftment in the developing CNS. We show that the MS-progeny behaves and differentiates into oligodendrocytes to the same extent as controls. They generate equal amounts of myelin, with bona fide nodes of Ranvier, and promote equal restoration of their host slow conduction. MS-progeny expressed oligodendrocyte- and astrocyte-specific connexins and established functional connections with donor and host glia. Thus, MS oligodendroglia, regardless of major immune manipulators, are intrinsically capable of myelination and making functional axo-glia/glia-glia connections, reinforcing the view that the MS oligodendrocyte differentiation block is not from major intrinsic oligodendroglial deficits.

Modelling multiple sclerosis using induced pluripotent stem cells

Multiple Sclerosis (MS) is one of the leading causes of non-traumatic neurological disability among young adults. Due to its complex pathology and the lack of reliable disease models, there are no effective therapies for MS to prevent neurodegeneration or promote neuroprotection, and hence stop disease progression. The emergence of induced pluripotent stem cells (iPSC) has allowed the generation of patient-specific neural cell types for disease modelling, drug screening, and cell therapy. In this review, the challenges related with the use of iPSC-derived cells in MS are discussed, with a special focus on the functional studies performed, limitations and future perspectives.

Antifungal drug miconazole ameliorated memory deficits in a mouse model of LPS-induced memory loss through targeting iNOS

Alzheimer’s disease (AD) is closely related to neuroinflammation, and the increase in inflammatory cytokine generation and inducible nitric oxide synthase (iNOS) expression in the brain of a patient with AD is well known. Excessive cytokines can stimulate iNOS in microglia and astroglia and overproduce nitric oxide, which can be toxic to neurons. The disease–gene–drug network analysis based on the GWAS/OMIM/DEG records showed that miconazole (MCZ) affected AD through interactions with NOS. Inhibiting iNOS can reduce neuroinflammation, thus preventing AD progression. To investigate the prophylactic role of antifungal agent in the AD development, a lipopolysaccharide-induced memory disorder mouse model was used, and cognitive function was assessed by Morris water maze test and passive avoidance test. MCZ treatment significantly attenuated cognitive impairment, suppressed iNOS and cyclooxygenase-2 expression, and activation of astrocyte and microglial BV2 cells, as well as reduced cytokine levels in the brains and lipopolysaccharide-treated astrocytes and microglia BV2 cells. In further mechanism studies, Pull-down assay and iNOS luciferase activity data showed that MCZ binds to iNOS and inhibited transcriptional activity. Our results suggest that MCZ is useful for ameliorating the neuroinflammation-mediated AD progression by blocking iNOS expression.

Stem Cells of the Aging Brain

The adult central nervous system (CNS) contains resident stem cells within specific niches that maintain a self-renewal and proliferative capacity to generate new neurons, astrocytes, and oligodendrocytes throughout adulthood. Physiological aging is associated with a progressive loss of function and a decline in the self-renewal and regenerative capacities of CNS stem cells. Also, the biggest risk factor for neurodegenerative diseases is age, and current in vivo and in vitro models of neurodegenerative diseases rarely consider this. Therefore, combining both aging research and appropriate interrogation of animal disease models towards the understanding of the disease and age-related stem cell failure is imperative to the discovery of new therapies. This review article will highlight the main intrinsic and extrinsic regulators of neural stem cell (NSC) aging and discuss how these factors impact normal homeostatic functions within the adult brain. We will consider established in vivo animal and in vitro human disease model systems, and then discuss the current and future trajectories of novel senotherapeutics that target aging NSCs to ameliorate brain disease.

Spinal Muscular Atrophy Modeling and Treatment Advances by Induced Pluripotent Stem Cells Studies

Spinal Muscular Atrophy (SMA) is a neurodegenerative disease characterized by specific and predominantly lower motor neuron (MN) loss. SMA is the main reason for infant death, while about one in 40 children born is a healthy carrier. SMA is caused by decreased levels of production of a ubiquitously expressed gene: the survival motor neuron (SMN). All SMA patients present mutations of the telomeric SMN1 gene, but many copies of a centromeric, partially functional paralog gene, SMN2, can somewhat compensate for the SMN1 deficiency, scaling inversely with phenotypic harshness. Because the study of neural tissue in and from patients presents too many challenges and is very often not feasible; the use of animal models, such as the mouse, had a pivotal impact in our understanding of SMA pathology but could not portray totally satisfactorily the elaborate regulatory mechanisms that are present in higher animals, particularly in humans. And while recent therapeutic achievements have been substantial, especially for very young infants, some issues should be considered for the treatment of older patients. An alternative way to study SMA, and other neurological pathologies, is the use of induced pluripotent stem cells (iPSCs) derived from patients. In this work, we will present a wide analysis of the uses of iPSCs in SMA pathology, starting from basic science to their possible roles as therapeutic tools.

iPS-Derived Early Oligodendrocyte Progenitor Cells from SPMS Patients Reveal Deficient In Vitro Cell Migration Stimulation

The most challenging aspect of secondary progressive multiple sclerosis (SPMS) is the lack of efficient regenerative response for remyelination, which is carried out by the endogenous population of adult oligoprogenitor cells (OPCs) after proper activation. OPCs must proliferate and migrate to the lesion and then differentiate into mature oligodendrocytes. To investigate the OPC cellular component in SPMS, we developed induced pluripotent stem cells (iPSCs) from SPMS-affected donors and age-matched controls (CT). We confirmed their efficient and similar OPC differentiation capacity, although we reported SPMS-OPCs were transcriptionally distinguishable from their CT counterparts. Analysis of OPC-generated conditioned media (CM) also evinced differences in protein secretion. We further confirmed SPMS-OPC CM presented a deficient capacity to stimulate OPC in vitro migration that can be compensated by exogenous addition of specific components. Our results provide an SPMS-OPC cellular model and encouraging venues to study potential cell communication deficiencies in the progressive form of multiple sclerosis (MS) for future treatment strategies.

Aging, Cellular Senescence, and Progressive Multiple Sclerosis

Aging is one of the most important risk factors for the development of several neurodegenerative diseases including progressive multiple sclerosis (MS). Cellular senescence (CS) is a key biological process underlying aging. Several stressors associated with aging and MS pathology, such as oxidative stress, mitochondrial dysfunction, cytokines and replicative exhaustion are known triggers of cellular senescence. Senescent cells exhibit stereotypical metabolic and functional changes, which include cell-cycle arrest and acquiring a pro-inflammatory phenotype secreting cytokines, growth factors, metalloproteinases and reactive oxygen species. They accumulate with aging and can convert neighboring cells to senescence in a paracrine manner. In MS, accelerated cellular senescence may drive disease progression by promoting chronic non-remitting inflammation, loss or altered immune, glial and neuronal function, failure of remyelination, impaired blood-brain barrier integrity and ultimately neurodegeneration. Here we discuss the evidence linking cellular senescence to the pathogenesis of MS and the putative role of senolytic and senomorphic agents as neuroprotective therapies in tackling disease progression.

iPSCs from people with MS can differentiate into oligodendrocytes in a homeostatic but not an inflammatory milieu

Multiple sclerosis (MS) is an inflammatory and demyelinating disease of the central nervous system (CNS) that results in variable severities of neurodegeneration. The understanding of MS has been limited by the inaccessibility of the affected cells and the lengthy timeframe of disease development. However, recent advances in stem cell technology have facilitated the bypassing of some of these challenges. Towards gaining a greater understanding of the innate potential of stem cells from people with varying degrees of disability, we generated induced pluripotent stem cells (iPSCs) from peripheral blood mononuclear cells derived from stable and progressive MS patients, and then further differentiated them into oligodendrocyte (OL) lineage cells. We analyzed differentiation under both homeostatic and inflammatory conditions via sustained exposure to low-dose interferon gamma (IFNγ), a prominent cytokine in MS. We found that all iPSC lines differentiated into mature myelinating OLs, but chronic exposure to IFNγ dramatically inhibited differentiation in both MS groups, particularly if exposure was initiated during the pre-progenitor stage. Low-dose IFNγ was not toxic but led to an early upregulation of interferon response genes in OPCs followed by an apparent redirection in lineage commitment from OL to a neuron-like phenotype in a significant portion of the treated cells. Our results reveal that a chronic low-grade inflammatory environment may have profound effects on the efficacy of regenerative therapies.

Astrocyte Support for Oligodendrocyte Differentiation can be Conveyed via Extracellular Vesicles but Diminishes with Age

The aging brain is associated with significant changes in physiology that alter the tissue microenvironment of the central nervous system (CNS). In the aged CNS, increased demyelination has been associated with astrocyte hypertrophy and aging has been implicated as a basis for these pathological changes. Aging tissues accumulate chronic cellular stress, which can lead to the development of a pro-inflammatory phenotype that can be associated with cellular senescence. Herein, we provide evidence that astrocytes aged in culture develop a spontaneous pro-inflammatory and senescence-like phenotype. We found that extracellular vesicles (EVs) from young astrocyte were sufficient to convey support for oligodendrocyte differentiation while this support was lost by EVs from aged astrocytes. Importantly, the negative influence of culture age on astrocytes, and their cognate EVs, could be countered by treatment with rapamycin. Comparative proteomic analysis of EVs from young and aged astrocytes revealed peptide repertoires unique to each age. Taken together, these findings provide new information on the contribution of EVs as potent mediators by which astrocytes can extert changing influence in either the disease or aged brain.

Remyelination Pharmacotherapy Investigations Highlight Diverse Mechanisms Underlying Multiple Sclerosis Progression

Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system characterized by a complex lesion microenvironment. Although much progress has been made in developing immunomodulatory treatments to reduce myelin damage and delay the progression of MS, there is a paucity in treatment options that address the multiple pathophysiological aspects of the disease. Currently available immune-centered therapies are able to reduce the immune-mediated damage exhibited in MS patients, however, they cannot rescue the eventual failure of remyelination or permanent neuronal damage that occurs as MS progresses. Recent advances have provided a better understanding of remyelination processes, specifically oligodendrocyte lineage cell progression following demyelination. Further there have been new findings highlighting various components of the lesion microenvironment that contribute to myelin repair and restored axonal health. In this review we discuss the complexities of myelin repair following immune-mediated damage in the CNS, the contribution of animal models of MS in providing insight on OL progression and myelin repair, and current and potential remyelination-centered therapeutic targets. As remyelination therapies continue to progress into clinical trials, we consider a dual approach targeting the inflammatory microenvironment and intrinsic remyelination mechanisms to be optimal in aiding MS patients.

Current Availability of Stem Cell-Based In Vitro Methods for Developmental Neurotoxicity (DNT) Testing

There is evidence that chemical exposure during development can cause irreversible impairments of the human developing nervous system. Therefore, testing compounds for their developmentally neurotoxic potential has high priority for different stakeholders: academia, industry, and regulatory bodies. Due to the resource-intensity of current developmental neurotoxicity (DNT) in vivo guidelines, alternative methods that are scientifically valid and have a high predictivity for humans are especially desired by regulators. Here, we review availability of stem-/progenitor cell-based in vitro methods for DNT evaluation that is based on the concept of neurodevelopmental process assessment. These test methods are assembled into a DNT in vitro testing battery. Gaps in this testing battery addressing research needs are also pointed out.

[Role of over-expression of TBX3 and TBX18 in the enrichment and differentiation of human induced pluripotent stem cells into sinoatrial node-like cells]

Objective

To explore the role of over-expression of TBX3 and TBX18 in inducing human induced pluripotent stem cells (HiPS) to enrich and differentiate into sinoatrial node-like cells.

Methods

The expression of stemness markers OCT3/4, SOX2, and NANOG in HiPS was detected by real-time fluorescence quantitative PCR (qRT- PCR), and compared with human embryonic stem cells (hESCs). Immunofluorescence staining was used to observe the expression of HiPS stemness markers OCT3/4, NANOG, SSEA4, and TRA-1-60. The HiPS were directional differentiated into cardiomyocytes, the expressions of ISL1, NK2 homeobox 5 (NKX2-5), ACTN1, and TNNT2 were detected by qRT-PCR, and human adult cardiomyocytes (hACM) were used as positive control. Immunofluorescence staining was used to observe the expressions of NKX2-5, cardiac troponin (cTnT), α-actinin, atria myosin light chain 2A (MLC-2A), and ventricular myosin light chain 2V (MLC-2V). The positive rate of α-actinin was detected by flow cytometry. On the 3rd day after HiPS were differentiated into cardiomyocytes (mesodermal stage), lentiviral over-expressions of sinoatrial node-related genes TBX3 and TBX18 were carried out for 21 days. The relative expressions of specific markers TBX3, TBX18, SHOX2, NKX2-5, HCN4, and HCN1 in sinoatrial node cells were detected by qRT-PCR, and compared with enhanced green fluorescent protein blank virus.

Results

OCT3/4, SOX2, and NANOG were highly expressed in HiPS and ESCs, and there was no significant difference in the relative expression of each gene ( P>0.05); OCT3/4 and NANOG were specifically distributed in the nucleus of HiPS, while SSEA4 and TRA-1-60 were distributed in the cell membrane. The relative expressions of ISL1 gene at 5, 7, 21, and 28 days and NKX2-5 gene at 7, 21, and 28 days of HiPS differentiation into cardiomyocytes were significantly higher than those of hACM ( P<0.05), and the relative expressions of ACTN1 and TNNT2 genes at 3, 5, 7, and 21 days of HiPS differentiation into cardiomyocytes were significantly lower than those of hACM ( P<0.05). NKX2-5 was expressed in most of the nuclei, cTnT and α-actinin, MLC-2A and MLC-2V signals were localized in the cytoplasm, presenting a texture-like structure of muscle nodules. Flow cytometry results showed that HiPS was successfully induced to differentiate into cardiomyocytes. The expressions of TBX18, SHOX2, HCN4, and HCN1 in the over-expression TBX3 group were up-regulated when compared with the control group, and difference in the relative expression of SHOX2 gene was significant ( P<0.05); the relative expression of NKX2-5 gene was lower than that in the control group, but there was no significant difference ( P>0.05). There was no significant difference in the relative expression of each gene between the over-expressed TBX18 group and the control group ( P>0.05).

Conclusion

HiPS and hESCs have similar pluripotency, and we have established a stable method for maintaining and culturing the stemness of HiPS. A technological platform for the efficient differentiation of HiPS into cardiomyocytes has been successfully established. Although TBX3 and TBX18 do not play a significant role in promoting the enrichment and differentiation of HiPS into sinoatrial node-like cells, TBX3 shows a certain promoting trend, which can be further explored in the future.

Cellular senescence in progenitor cells contributes to diminished remyelination potential in progressive multiple sclerosis

We identify cellular senescence occurring in neural progenitor cells (NPCs) from primary progressive multiple sclerosis (PPMS). In this study, senescent progenitor cells were identified within demyelinated white matter lesions in progressive MS (PMS) autopsy tissue, and induced pluripotent stem-derived NPCs from patients with PPMS were found to express cellular senescence markers compared with age-matched control NPCs. Reversal of this cellular senescence phenotype, by treatment with rapamycin, restored PPMS NPC-mediated support for oligodendrocyte (OL) maturation. Proteomic and histological analyses identify senescent progenitor cells in PMS as a source of high-mobility group box-1, which limits maturation and promotes transcriptomic changes in OLs. These findings provide evidence that cellular senescence is an active process in PMS that may contribute to limited remyelination in disease.

Cellular senescence is a form of adaptive cellular physiology associated with aging. Cellular senescence causes a proinflammatory cellular phenotype that impairs tissue regeneration, has been linked to stress, and is implicated in several human neurodegenerative diseases. We had previously determined that neural progenitor cells (NPCs) derived from induced pluripotent stem cell (iPSC) lines from patients with primary progressive multiple sclerosis (PPMS) failed to promote oligodendrocyte progenitor cell (OPC) maturation, whereas NPCs from age-matched control cell lines did so efficiently. Herein, we report that expression of hallmarks of cellular senescence were identified in SOX2⁺ progenitor cells within white matter lesions of human progressive MS (PMS) autopsy brain tissues and iPS-derived NPCs from patients with PPMS. Expression of cellular senescence genes in PPMS NPCs was found to be reversible by treatment with rapamycin, which then enhanced PPMS NPC support for oligodendrocyte (OL) differentiation. A proteomic analysis of the PPMS NPC secretome identified high-mobility group box-1 (HMGB1), which was found to be a senescence-associated inhibitor of OL differentiation. Transcriptome analysis of OPCs revealed that senescent NPCs induced expression of epigenetic regulators mediated by extracellular HMGB1. Lastly, we determined that progenitor cells are a source of elevated HMGB1 in human white matter lesions. Based on these data, we conclude that cellular senescence contributes to altered progenitor cell functions in demyelinated lesions in MS. Moreover, these data implicate cellular aging and senescence as a process that contributes to remyelination failure in PMS, which may impact how this disease is modeled and inform development of future myelin regeneration strategies.

Silent Free Fall at Disease Onset: A Perspective on Therapeutics for Progressive Multiple Sclerosis

Central nervous system (CNS) degeneration occurs during multiple sclerosis (MS) following several years of reversible autoimmune demyelination. Progressive CNS degeneration appears later during the course of relapsing-remitting MS (RRMS), although it starts insidiously at disease onset. We propose that there is an early subclinical phase also for primary-progressive (PP) MS. Consensus exists that many different cell types are involved during disease onset. Furthermore, the response to the initial damage, which is specific for each individual, would result in distinct pathological pathways that add complexity to the disease and the mechanisms underlying progressive CNS degeneration. Progressive MS is classified as either active or not active, as well as with or without progression. Different forms of progressive MS might reflect distinct or overlapping pathogenetic pathways. Disease mechanisms should be determined for each patient at diagnosis and the time of treatment. Until individualized and time-sensitive treatments that specifically target the molecular mechanisms of the progressive aspect of the disease are identified, combined therapies directed at anti-inflammation, regeneration, and neuroprotection are the most effective for preventing MS progression. This review presents selected therapeutics in support of the overall idea of a multidimensional therapy applied early in the disease. This approach could limit damage and increase CNS repair. By targeting several cellular populations (i.e., microglia, astrocytes, neurons, oligodendrocytes, and lymphocytes) and multiple pathological processes (e.g., inflammation, demyelination, synaptopathy, and excitatory/inhibitory imbalance) progressive MS could be attenuated. Early timing for such multidimensional therapy is proposed as the prerequisite for effectively halting progressive MS.

Polycaprolactone electrospun fiber scaffold loaded with iPSCs-NSCs and ASCs as a novel tissue engineering scaffold for the treatment of spinal cord injury

Background

Spinal cord injury (SCI) is a traumatic disease of the central nervous system, accompanied with high incidence and high disability rate. Tissue engineering scaffold can be used as therapeutic systems to provide effective repair for SCI.

Purpose

In this study, a novel tissue engineering scaffold has been synthesized in order to explore the effect of nerve repair on SCI.

Patients and methods

Polycaprolactone (PCL) scaffolds loaded with actived Schwann cells (ASCs) and induced pluripotent stem cells -derived neural stem cells (iPSC-NSCs), a combined cell transplantation strategy, were prepared and characterized. The cell-loaded PCL scaffolds were further utilized for the treatment of SCI in vivo. Histological observation, behavioral evaluation, Western-blot and qRT-PCR were used to investigate the nerve repair of Wistar rats after scaffold transplantation.

Results

The iPSCs displayed similar characteristics to embryonic stem cells and were efficiently differentiated into neural stem cells in vitro. The obtained PCL scaffolds werê0.5 mm in thickness with biocompatibility and biodegradability. SEM results indicated that the ASCs and (or) iPS-NSCs grew well on PCL scaffolds. Moreover, transplantation reduced the volume of lesion cavity and improved locomotor recovery of rats. In addition, the degree of spinal cord recovery and remodeling maybe closely related to nerve growth factor and glial cell-derived neurotrophic factor. In summary, our results demonstrated that tissue engineering scaffold treatment could increase tissue remodeling and could promote motor function recovery in a transection SCI model.

Conclusion

This study provides preliminary evidence for using tissue engineering scaffold as a clinically viable treatment for SCI in the future.

Differentiation of Glial Cells From hiPSCs: Potential Applications in Neurological Diseases and Cell Replacement Therapy

Glial cells are the most abundant cell type in the central nervous system (CNS) and play essential roles in maintaining brain homeostasis, forming myelin, and providing support and protection for neurons, etc. Over the past decade, significant progress has been made in the reprogramming field. Given the limited accessibility of human glial cells, in vitro differentiation of human induced pluripotent stem cells (hiPSCs) into glia may provide not only a valuable research tool for a better understanding of the functions of glia in the CNS but also a potential cellular source for clinical therapeutic purposes. In this review, we will summarize up-to-date novel strategies for the committed differentiation into the three major glial cell types, i.e., astrocyte, oligodendrocyte, and microglia, from hiPSCs, focusing on the non-neuronal cell effects on the pathology of some representative neurological diseases. Furthermore, the application of hiPSC-derived glial cells in neurological disease modeling will be discussed, so as to gain further insights into the development of new therapeutic targets for treatment of neurological disorders.

An integrated biomanufacturing platform for the large-scale expansion and neuronal differentiation of human pluripotent stem cell-derived neural progenitor cells

Human pluripotent stem cell derived neural progenitor cells (hNPCs) have the unique properties of long-term in vitro expansion as well as differentiation into the various neurons and supporting cell types of the central nervous system (CNS). Because of these characteristics, hNPCs have tremendous potential in the modeling and treatment of various CNS diseases and disorders. However, expansion and neuronal differentiation of hNPCs in quantities necessary for these applications is not possible with current two dimensional (2-D) approaches. Here, we used a fully defined peptide substrate as the basis for a microcarrier (MC)-based suspension culture system. Several independently derived hNPC lines were cultured on MCs for multiple passages as well as efficiently differentiated to neurons. Finally, this MC-based system was used in conjunction with a low shear rotating wall vessel (RWV) bioreactor for the integrated, large-scale expansion and neuronal differentiation of hNPCs. Overall, this fully defined and scalable biomanufacturing system will facilitate the generation of hNPCs and their neuronal derivatives in quantities necessary for basic and translational applications.

STATEMENT OF SIGNIFICANCE

In this work, we developed a microcarrier (MC)-based culture system that allows for the expansion and neuronal differentiation of human pluripotent stem cell-derived neural progenitor cells (hNPCs) under defined conditions. In turn, this MC approach was implemented in a rotating wall vessel (RWV) bioreactor for the large-scale expansion and neuronal differentiation of hNPCs. This work is of significance as it overcomes current limitations of conventional two dimensional (2-D) culture systems to enable the generation of hNPCs and their neuronal derivatives in quantities required for downstream applications in disease modeling, drug screening, and regenerative medicine.

A review on stem cell therapy for multiple sclerosis: special focus on human embryonic stem cells

Multiple sclerosis (MS), a complex disorder of the central nervous system (CNS), is characterized with axonal loss underlying long-term progressive disability. Currently available therapies for its management are able to slow down the progression but fail to treat it completely. Moreover, these therapies are associated with major CNS and cardiovascular adverse events, and prolonged use of these treatments may cause life-threatening diseases. Recent research has shown that cellular therapies hold a potential for CNS repair and may be able to provide protection from inflammatory damage caused after injury. Human embryonic stem cell (hESC) transplantation is one of the promising cell therapies; hESCs play an important role in remyelination and help in preventing demylenation of the axons. In this study, an overview of the current knowledge about the unique properties of hESC and their comparison with other cell therapies has been presented for the treatment of patients with MS.

Representing Diversity in the Dish: Using Patient-Derived in Vitro Models to Recreate the Heterogeneity of Neurological Disease

Neurological diseases, including dementias such as Alzheimer's disease (AD) and fronto-temporal dementia (FTD) and degenerative motor neuron diseases such as amyotrophic lateral sclerosis (ALS), are responsible for an increasing fraction of worldwide fatalities. Researching these heterogeneous diseases requires models that endogenously express the full array of genetic and epigenetic factors which may influence disease development in both familial and sporadic patients. Here, we discuss the two primary methods of developing patient-derived neurons and glia to model neurodegenerative disease: reprogramming somatic cells into induced pluripotent stem cells (iPSCs), which are differentiated into neurons or glial cells, or directly converting (DC) somatic cells into neurons (iNeurons) or glial cells. Distinct differentiation techniques for both models result in a variety of neuronal and glial cell types, which have been successful in displaying unique hallmarks of a variety of neurological diseases. Yield, length of differentiation, ease of genetic manipulation, expression of cell-specific markers, and recapitulation of disease pathogenesis are presented as determining factors in how these methods may be used separately or together to ascertain mechanisms of disease and identify therapeutics for distinct patient populations or for specific individuals in personalized medicine projects.

Challenge of progressive multiple sclerosis therapy

PURPOSE OF REVIEW

Understanding the mechanisms underlying progression in multiple sclerosis (MS) and identifying appropriate therapeutic targets is a key challenge facing the MS community. This challenge has been championed internationally by organizations such as the Progressive MS Alliance, which has raised the profile of progressive MS and identified the key obstacles to treatment. This review will outline the considerable progress against these challenges.

RECENT FINDINGS

New insights into mechanisms underlying progression have opened up potential therapeutic opportunities. This has been complemented by ongoing validation of clinical and imaging outcomes for Phase II trials of progression, coupled with the development of innovative trial designs. The field has been greatly encouraged by recent positive Phase III trials in both primary and secondary progressive MS, albeit with modest benefit. Early trials of neuroprotection and repair have provided important new data with which to drive the field. Improving symptom management and advancing rehabilitation approaches, critical for this patient population which, taken together with identifying and managing comorbidities and risk factors, has an appreciable impact on health-related quality of life.

SUMMARY

Raising the profile of progressive MS has resulted in the first effective treatments with the promise of more to come.

Stem Cell Therapy for Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory, autoimmune, and neurodegenerative disease of the central nervous system (CNS). It is characterized by demyelination and neuronal loss that is induced by attack of autoreactive T cells to the myelin sheath and endogenous remyelination failure, eventually leading to functional neurological disability. Although recent evidence suggests that MS relapses are induced by environmental and exogenous triggers such as viral infections in a genetic background, its very complex pathogenesis is not completely understood. Therefore, the efficiency of current immunosuppression-based therapies of MS is too low, and emerging disease-modifying immunomodulatory agents such as fingolimod and dimethyl fumarate cannot stop progressive neurodegenerative process. Thus, the cell replacement therapy approach that aims to overcome neuronal cell loss and remyelination failure and to increase endogenous myelin repair capacity is considered as an alternative treatment option. A wide variety of preclinical studies, using experimental autoimmune encephalomyelitis model of MS, have recently shown that grafted cells with different origins including mesenchymal stem cells (MSCs), neural precursor and stem cells, and induced-pluripotent stem cells have the ability to repair CNS lesions and to recover functional neurological deficits. The results of ongoing autologous hematopoietic stem cell therapy studies, with the advantage of peripheral administration to the patients, have suggested that cell replacement therapy is also a feasible option for immunomodulatory treatment of MS. In this chapter, we overview cell sources and applications of the stem cell therapy for treatment of MS. We also discuss challenges including those associated with administration route, immune responses to grafted cells, integration of these cells to existing neural circuits, and risk of tumor growth. Finally, future prospects of stem cell therapy for MS are addressed.

Neural Stem Cell-Based Regenerative Approaches for the Treatment of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic, autoimmune, inflammatory, and demyelinating disorder of the central nervous system (CNS), which ultimately leads to axonal loss and permanent neurological disability. Current treatments for MS are largely comprised of medications that are either immunomodulatory or immunosuppressive and are aimed at reducing the frequency and intensity of relapses. Neural stem cells (NSCs) in the adult brain can differentiate into oligodendrocytes in a context-specific manner and are shown to be involved in the remyelination in these patients. NSCs may exert their beneficial effects not only through oligodendrocyte replacement but also by providing trophic support and immunomodulation, a phenomenon now known as "therapeutic plasticity." In this review, we first provided an update on the current knowledge regarding MS pathogenesis and the role of immune cells, microglia, and oligodendrocytes in MS disease progression. Next, we reviewed the current progress on research aimed toward stimulating endogenous NSC proliferation and differentiation to oligodendrocytes in vivo and in animal models of demyelination. In addition, we explored the neuroprotective and immunomodulatory effects of transplanted exogenous NSCs on T cell activation, microglial activation, and endogenous remyelination and their effects on the pathological process and prognosis in animal models of MS. Finally, we examined various protocols to generate genetically engineered NSCs as a potential therapy for MS. Overall, this review highlights the studies involving the immunomodulatory, neurotrophic, and regenerative effects of NSCs and novel methods aiming at stimulating the potential of NSCs for the treatment of MS.