Remyelination In Multiple Sclerosis Patients Research Articles

Remyelination in Multiple Sclerosis: Findings in the Cuprizone Model.

Remyelination therapies, which are currently under development, have a great potential to delay, prevent or even reverse disability in multiple sclerosis patients. Several models are available to study the effectiveness of novel compounds in vivo, among which is the cuprizone model. This model is characterized by toxin-induced demyelination, followed by endogenous remyelination after cessation of the intoxication. Due to its high reproducibility and ease of use, this model enjoys high popularity among various research and industrial groups. In this review article, we will summarize recent findings using this model and discuss the potential of some of the identified compounds to promote remyelination in multiple sclerosis patients.

G Protein-Coupled Receptor 17 Inhibition as a Prospective Treatment for Multiple Sclerosis: A Research Protocol

Introduction: Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative disease. MS is the most prevalent neurological disability that often leads to severe cognitive or physical incapacitations in young adults. As MS is currently an incurable disease, more effective treatments need to be investigated. The disease is associated with axonal degenerations and the development of demyelinated plaques, due to episodic autoimmune destruction of oligodendrocytes. Usually, demyelination is followed by remyelination as the brain attempts to reconstruct the myelin sheaths. Oligodendrocyte precursor cells are essential for remyelination as these cells proliferate and differentiate into mature oligodendrocytes. An important regulator of oligodendrocyte development is G protein-coupled receptor 17 (GPR17), whose inhibition has been suggested in previous studies to the promote oligodendrocyte differentiation and remyelination. As such, a potential therapy for MS patients is through decreasing GPR17 expression via inhibition of one of its ligands, LTC4. Methods: We aim to promote remyelination in MS patients using the LTC4 synthase inhibitor AZD9898 to indirectly partially inhibit GPR17 in proteolipid protein-induced experimental autoimmune encephalomyelitis (PLP-induced EAE) MS mice models. There will be 6 experimental groups and 8 control groups. All experimental groups will receive a three mg dose of AZD9898. After approximately zero, one, five and ten days, the mice will be sacrificed, and magnetic resonance imaging will be conducted. The myelin water fraction will then be determined to visualize in vivo myelination of the central nervous system through myelin water imaging. Western blotting will be used to verify AZD9898’s indirect inhibition of GPR17. The resulting data will be analyzed with the Kolomogorov–Smirnov test, Pearson’s correlation coefficient (linear) and two-tailed paired t-tests and ImageJ software. Anticipated Results: It is expected that AZD9898 administration in PLP-induced EAE mice models will result in an increased myelin water fraction, indicating remyelination, alongside decreased GPR17 expression. Discussion: These results will provide a potential treatment for MS by illustrating how AZD9898 is effective at indirectly inhibiting GPR17 in mice models, and thus promoting remyelination. Conclusion: This study will provide insight on the treatment of demyelinating diseases by demonstrating how pharmacological inhibition of GPR17 ligand LTC4 can promote remyelination in MS patients.

Recent Advances on Immunosuppressive Drugs and Remyelination Enhancers for the Treatment of Multiple Sclerosis.

Mammalian nervous systems depend crucially on myelin sheaths covering the axons. In the central nervous system, myelin sheaths consist of lipid structures that are generated from the membrane of oligodendrocytes (OL). These sheaths allow fast nerve transmission, protect axons and provide them metabolic support. In response to specific traumas or pathologies, these lipid structures can be destabilized and generate demyelinating lesions. Multiple sclerosis (MS) is an example of a demyelinating disease in which the myelin sheaths surrounding the nerve fibers of the brain and spinal cord are damaged. MS is the leading cause of neurological disability in young adults in many countries, and its incidence has been increasing in recent decades. Related to its etiology, it is known that MS is an autoimmune and inflammatory CNS disease. However, there are no effective treatments for this disease and the immunomodulatory therapies that currently exist have proven limited success since they only delay the progress of the disease. Nowadays, one of the main goals in MS research is to find treatments which allow the recovery of neurological disabilities due to demyelination. To this end, different approaches, such as modulating intracellular signaling or regulating the lipid metabolism of OLs, are being considered. Here, in addition to immunosuppressive or immunomodulatory drugs that reduce the immune response against myelin sheaths, we review a diverse group of drugs that promotes endogenous remyelination in MS patients and their use may be interesting as potential therapeutic agents in MS disease. To this end, we compile specific treatments against MS that are currently in the market with remyelination strategies that have entered into human clinical trials for future reparative MS therapies. The method used in this study is a systematic literature review on PubMed, Web of Science and Science Direct databases up to May 31, 2020. To narrow down the search results in databases, more specific keywords, such as "myelin sheath", "remyelination", "demyelination", "oligodendrocyte" and "lipid synthesis" were used to focus the search. We preferred papers published after January 2015, but did not exclude earlier seminal papers.

MiR-219a-5p Enriched Extracellular Vesicles Induce OPC Differentiation and EAE Improvement More Efficiently Than Liposomes and Polymeric Nanoparticles.

Remyelination is a key aspect in multiple sclerosis pathology and a special effort is being made to promote it. However, there is still no available treatment to regenerate myelin and several strategies are being scrutinized. Myelination is naturally performed by oligodendrocytes and microRNAs have been postulated as a promising tool to induce oligodendrocyte precursor cell differentiation and therefore remyelination. Herein, DSPC liposomes and PLGA nanoparticles were studied for miR-219a-5p encapsulation, release and remyelination promotion. In parallel, they were compared with biologically engineered extracellular vesicles overexpressing miR-219a-5p. Interestingly, extracellular vesicles showed the highest oligodendrocyte precursor cell differentiation levels and were more effective than liposomes and polymeric nanoparticles crossing the blood–brain barrier. Finally, extracellular vesicles were able to improve EAE animal model clinical evolution. Our results indicate that the use of extracellular vesicles as miR-219a-5p delivery system can be a feasible and promising strategy to induce remyelination in multiple sclerosis patients.

Preclinical evaluation of the PI3K/Akt/mTOR pathway in animal models of multiple sclerosis.

The PI3K/AKT/mTOR pathway is an intracellular signalling pathway that regulates cell activation. proliferation, metabolism and apoptosis. Increasing body of data suggests that alterations in the PI3K/AKT/mTOR pathway may result in an enhanced susceptibility to autoimmunity. Multiple Sclerosis (MS) is one of the most common chronic inflammatory diseases of the central nervous system leading to demyelination and neurodegeneration.In the current study, we have firstly evaluated in silico the involvement of the mTOR network on the generation and progression of MS and on oligodendrocyte function, making use of currently available whole-genome transcriptomic data. Then, the data generated in silico were subjected to an ex-vivo evaluation. To this aim, the involvement of mTOR was validated on a well-known animal model of MS and in vitro on Th17 cells.Our data indicate that there is a significant involvement of the mTOR network in the etiopathogenesis of MS and that Rapamycin treatment may represent a useful therapeutic approach in this clinical setting. On the other hand, our data showed that a significant involvement of the mTOR network could be observed only in the early phases of oligodendrocyte maturation, but not in the maturation process of adult oligodendrocytes and in the process of remyelination following demyelinating injury.Overall, our study suggests that targeting the PI3K/mTOR pathway, although it may not be a useful therapeutic approach to promote remyelination in MS patients, it can be exploited to exert immunomodulation, preventing/delaying relapses, and to treat MS patients in order to slow down the progression of disability.

Q-Space Myelin Map imaging for longitudinal analysis of demyelination and remyelination in multiple sclerosis patients treated with fingolimod: A preliminary study

BackgroundFingolimod (FTY) is an oral sphingosine-1-phosphate receptor modulator that reduces relapse and slows brain atrophy in multiple sclerosis (MS) patients. In addition, FTY has been shown to enhance remyelination in certain animal models. ObjectiveTo analyze feasibility of a novel q-space Myelin Map imaging to monitor demyelination and remyelination under FTY treatment in MS patients. MethodsTreatment outcomes of 24 consecutive MS patients treated with FTY were analyzed. A longitudinal analysis of q-space Myelin Map imaging was performed in a subset of these patients. ResultsDuring the treatment course (average of 16.1months), 10 patients (42%) exhibited improvement on the Expanded Disability Status Scale (EDSS) or maintained disability-free state (“optimal responders”). The average baseline age and EDSS score were significantly younger and milder in optimal responders compared to the rest of patients. A pilot longitudinal q-space Myelin Map study in 8 patients (including 4 optimal responders) showed that optimal responders tended to show signs of remyelination while exhibiting no newly evolved demyelinated lesions. ConclusionFTY may improve disability in younger patients with milder MS, and absence of demyelination activity and presence of remyelination activity may in part be associated with such improvement. q-Space Myelin Map imaging is a clinically feasible modality to monitor demyelination and remyelination in MS patients.

DNA methylation in oligodendroglial cells during developmental myelination and in disease.

Oligodendrocyte progenitor cells (OPC) are the myelinating cells of the central nervous system (CNS). During development, they differentiate into mature oligodendrocytes (OL) and ensheath axons, providing trophic and functional support to the neurons. This process is regulated by the dynamic expression of specific transcription factors, which, in turn, is controlled by epigenetic marks such as DNA methylation. Here we discuss recent findings showing that DNA methylation levels are differentially regulated in the oligodendrocyte lineage during developmental myelination, affecting both genes expression and alternative splicing events. Based on the phenotypic characterization of mice with genetic ablation of DNA methyltransferase 1 (Dnmt1) we conclude that DNA methylation is critical for efficient OPC expansion and for developmental myelination. Previous work suggests that in the context of diseases such as multiple sclerosis (MS) or gliomas, DNA methylation is differentially regulated in the CNS of affected individuals compared with healthy controls. In this commentary, based on the results of previous work, we propose the potential role of DNA methylation in adult oligodendroglial lineage cells in physiologic and pathological conditions, and delineate potential research approaches to be undertaken to test this hypothesis. A better understanding of this epigenetic modification in adult oligodendrocyte progenitor cells is essential, as it can potentially result in the design of new therapeutic strategies to enhance remyelination in MS patients or reduce proliferation in glioma patients.

Survival and Functionality of Human Induced Pluripotent Stem Cell-Derived Oligodendrocytes in a Nonhuman Primate Model for Multiple Sclerosis

This study demonstrates for the first time that human induced pluripotent stem cell (iPSC)-derived oligodendrocyte precursor cells (OPCs), after intracortical implantation in a nonhuman primate model for progressive multiple sclerosis (MS), migrate to the lesions and remyelinate denuded axons. These findings imply that human iPSC-OPCs can be a therapeutic tool for MS. The results of this feasibility study on the potential use of hiPSC-derived OPCs are of great importance for all MS researchers focusing on the stimulation of remyelination in MS patients. Further optimization and research on practical issues related to the safe production and administration of iPSC-derived cell grafts will likely lead to a first clinical trial in a small group of secondary progressive MS patients. This would be the first specific therapeutic approach aimed at restoring myelination and rescuing axons in MS patients, since there is no treatment available for this most debilitating aspect of MS.

Application of q-Space Diffusion MRI for the Visualization of White Matter.

Myelin abnormalities in the CNS have been gaining increasing attention in various neurological and psychiatric diseases. However, appropriate methods with which to monitor CNS myelin in daily clinical practice have been lacking. In the current study, we introduced a novel MRI modality that produces the "myelin map." The myelin map accurately depicted myelin status in mice and nonhuman primates and in a pilot clinical study of multiple sclerosis patients, suggesting that it is useful in detecting possibly remyelinated lesions. A myelin map of the human brain could be obtained in <10 min using a 3 T scanner and it therefore promises to be a powerful tool for researchers and clinicians examining myelin-related diseases.

Remyelination Therapy in Multiple Sclerosis.

Multiple sclerosis (MS) is an immune-mediated disorder of the central nervous system that results in destruction of the myelin sheath that surrounds axons and eventual neurodegeneration. Current treatments approved for the treatment of relapsing forms of MS target the aberrant immune response and successfully reduce the severity of attacks and frequency of relapses. Therapies are still needed that can repair damage particularly for the treatment of progressive forms of MS for which current therapies are relatively ineffective. Remyelination can restore neuronal function and prevent further neuronal loss and clinical disability. Recent advancements in our understanding of the molecular and cellular mechanisms regulating myelination, as well as the development of high-throughput screens to identify agents that enhance myelination, have lead to the identification of many potential remyelination therapies currently in preclinical and early clinical development. One problem that has plagued the development of treatments to promote remyelination is the difficulty in assessing remyelination in patients with current imaging techniques. Powerful new imaging technologies are making it easier to discern remyelination in patients, which is critical for the assessment of these new therapeutic strategies during clinical trials. This review will summarize what is currently known about remyelination failure in MS, strategies to overcome this failure, new therapeutic treatments in the pipeline for promoting remyelination in MS patients, and new imaging technologies for measuring remyelination in patients.

Remyelination in multiple sclerosis: cellular mechanisms and novel therapeutic approaches.

The myelin sheath that coats axons allows rapid propagation of electrical impulses across the nervous system. Oligodendrocytes (ODs) are myelin-producing cells of the central nervous system (CNS) responsible for wrapping the axons of neurons. Multiple sclerosis (MS) is a demyelinating disease of the CNS identifiable by white and gray matter lesions. These lesions consist of axons that have lost their myelin through an autoimmune response to myelin and ODs. Current treatments for MS target the autoimmune aspect of the disease. However, these immunomodulators do not directly enhance the process of remyelination. The ability to remyelinate lesions can be enhanced by neural progenitor cells that can differentiate into ODs and replace lost myelin, although successful remyelination is complex and dependent on multiple factors. The restoration of lost myelin might protect the axon from degeneration and restore optimal conduction of impulses in MS patients, requiring further research on proremyelinating therapies. The combination of immunomodulators and remyelinating enhancers might be the best course of treatment for many MS patients. This Review discusses demyelination in MS, the mechanisms of remyelination, and current therapies designed to promote remyelination in MS patients.

PET imaging of demyelination and remyelination in the cuprizone mouse model for multiple sclerosis: A comparison between [11C]CIC and [11C]MeDAS

Multiple Sclerosis (MS) is a neurodegenerative disease characterized by demyelinated lesions. PET imaging using specific myelin radioligands might solve the lack of a specific imaging tool for diagnosing and monitoring demyelination and remyelination in MS patients. In recent years, a few tracers have been developed for in vivo PET imaging of myelin, but they have not been fully evaluated yet. In this study, we compared [11C]CIC and [11C]MeDAS as PET tracers for monitoring demyelination and remyelination in cuprizone-fed mice. The ex vivo biodistribution of [11C]CIC showed decreased tracer uptake in mice fed with 0.2% cuprizone diet for 5weeks, as compared to control mice. However, tracer uptake did not increase again after normal diet was restored for 5weeks (remyelination). Surprisingly, in vivo PET imaging with [11C]CIC in cuprizone-fed mice revealed a significant reduction in whole brain tracer uptake after 5weeks of remyelination. No correlation between ex vivo biodistribution and in vivo imaging data was found for [11C]CIC (r2=0.15, p=0.11). However, a strong correlation was found for [11C]MeDAS (r2=0.88, p<0.0001). [11C]MeDAS ex vivo biodistribution revealed significant decreased brain uptake in the demyelination group, as compared to controls and increased the tracer uptake after 5weeks of remyelination. [11C]MeDAS images showed a low background signal and clear uptake in the brain white matter and spinal cord. Taken together, the results of this comparative study between [11C]CIC and [11C]MeDAS clearly show that [11C]MeDAS is the preferred PET tracer to monitor myelin changes in the brain and spinal cord in vivo.

Endogeneous Remyelination: Findings in Human Studies

In multiple sclerosis, conduction block in demyelinated axons underlies early neurological symptoms, whereas axonal transection is believed to be responsible for more permanent later deficits. Approved treatments for the disease are immunoregulatory and reduce the rate of lesion formation and clinical exacerbation, but are only partially effective in preventing the onset of disability. Remyelination is a term for the re-generation of the nerve's myelin sheath and is a subject of active medical research. Remyelination capacity varies from patient to patient or even from lesion to lesion in one and the same patient. Efforts to understand the causes for remyelination failure have prompted research into the biology of remyelination and the complex molecular factors that regulate remyelination. In the current review article we address challenges of remyelination research with a special focus on histo-pathological studies using brain biopsy and autopsy material. We summarize our current knowledge about extent of remyelination in multiple sclerosis patients and its relation to disease duration, lesion type, inflammation, affected brain region and gender. Furthermore we will address which step(s) of the oligodendrocyte maturation program is impaired and, thus, could be a feasible target for therapeutic interventions. Specifically mentioned will be the distribution of oligodendrocyte progenitor cells in demyelinated multiple sclerosis plaques and therapeutic approaches which aim to boost intrinsic properties of progenitor cells or to supply progenitors by cell transplantation approaches. This comprehensive overview is complemented by recent findings suggesting that U.S. Food and Drug Administration-approved treatment options, such as FTY720 (Gilenya®) or glatiramer acetate (Copaxone®) might boost myelin repair.

Cooperative contributions of Interferon regulatory factor 1 (IRF1) and IRF8 to interferon-γ-mediated cytotoxic effects on oligodendroglial progenitor cells

BackgroundAdministration of exogenous interferon-γ (IFNγ) aggravates the symptoms of multiple sclerosis (MS), whereas interferon-β (IFNβ) is used for treatment of MS patients. We previously demonstrated that IFNγ induces apoptosis of oligodendroglial progenitor cells (OPCs), suggesting that IFNγ is more toxic to OPCs than IFNβ. Thus we hypothesized that a difference in expression profiles between IFNγ-inducible and IFNβ-inducible genes in OPCs would predict the genes responsible for IFNγ-mediated cytotoxic effects on OPCs. We have tested this hypothesis particularly focusing on the interferon regulatory factors (IRFs) well-known transcription factors up-regulated by IFNs.MethodsHighly pure primary rat OPC cultures were treated with IFNγ and IFNβ. Cell death and proliferation were assessed by MTT reduction, caspse-3-like proteinase activity, Annexin-V binding, mitochondrial membrane potential, and BrdU-incorporation. Induction of all nine IRFs was comprehensively compared by quantitative PCR between IFNγ-treated and IFNβ-treated OPCs. IRFs more strongly induced by IFNγ than by IFNβ were selected, and tested for their ability to induce OPC apoptosis by overexpression and by inhibition by dominant-negative proteins or small interference RNA either in the presence or absence of IFNγ.ResultsUnlike IFNγ, IFNβ did not induce apoptosis of OPCs. Among nine IRFs, IRF1 and IRF8 were preferentially up-regulated by IFNγ. In contrast, IRF7 was more robustly induced by IFNβ than by IFNγ. Overexpressed IRF1 elicited apoptosis of OPCs, and a dominant negative IRF1 protein partially protected OPCs from IFNγ-induced apoptosis, indicating a substantial contribution of IRF1 to IFNγ-induced OPC apoptosis. On the other hand, overexpression of IRF8 itself had only marginal proapoptotic effects. However, overexpressed IRF8 enhanced the IFNγ-induced cytotoxicity and the proapoptotic effect of overexpressed IRF1, and down-regulation of IRF8 by siRNA partially but significantly reduced preapoptotic cells after treatment with IFNγ, suggesting that IRF8 cooperatively enhances IFNγ-induced OPC apoptosis.ConclusionsThis study has identified that IRF1 and IRF8 mediate IFNγ-signaling leading to OPC apoptosis. Therapies targeting at these transcription factors and their target genes could reduce IFNγ-induced OPC loss and thereby enhance remyelination in MS patients.

Oligodendrocyte precursor cells in the demyelinated multiple sclerosis spinal cord.

Lesions appearing in the CNS of patients in the chronic phase of the inflammatory, demyelinating disease multiple sclerosis often fail to repair, resulting in neurological dysfunction. This failure of remyelination appears, in many cases, to be due not to the destruction of the local oligodendrocyte precursor population, a source for new myelin-forming cells, but to the failure of the precursor cells to proliferate and differentiate, at least in brain lesions. The spinal cord is also a prominent site for lesions in multiple sclerosis, but nothing is known about the fate of the oligodendrocyte precursor population in this area. The present study has therefore analysed spinal cord samples with demyelination from 16 subjects with longstanding multiple sclerosis for the presence of oligodendrocyte precursor cells. Immunolabellings of 10 microm thick sections with the O4/anti-galactocerebroside (GalC) antibody combination, to visualize O4-positive, GalC-negative oligodendrocyte precursor cells, revealed that such cells were prevalent in many spinal cord lesions, with densities of up to 35 cells/mm(2). Six of the spinal cord lesions contained < or =3 O4-positive, GalC-negative cells/mm(2), but such cells were widespread in brain lesions from these multiple sclerosis cases that were available for study (8-26 cells/mm(2)). The density of the O4-positive, GalC-negative oligodendrocyte precursor cells in all spinal cord and brain lesions studied thus far (n = 41) decreased significantly with declining numbers of debris-laden macrophages. In addition, lesions lacking macrophages tended to be derived from the older patients and there was a negative correlation between the density of the oligodendrocyte precursor cells and clinical age of the multiple sclerosis subject at death, and disease duration. The analysis further revealed that lesions from subjects with primary progressive and secondary progressive multiple sclerosis contained, on average, similar numbers of oligodendrocyte precursor cells/mm(2) and that immature oligodendrocytes were only present in significant numbers in lesions with high precursor densities. Taken together, the present data suggest that there is a gradual reduction in the size of the O4-positive, GalC- negative oligodendrocyte precursor population with increasing age of the lesion, that the generation of new oligodendrocytes becomes increasingly more impaired and that lesions are not repopulated to a significant extent by migratory oligodendrocyte precursor cells present in the adjacent unaffected tissue. Hence, strategies intended to promote endogenous remyelination in multiple sclerosis patients should focus on both enhancing the long-term survival of oligodendrocyte precursor cells and on stimulating these cells to proliferate and differentiate into remyelinating oligodendrocytes.

NG2-Positive Oligodendrocyte Progenitor Cells in Adult Human Brain and Multiple Sclerosis Lesions

Multiple sclerosis (MS) is characterized by multifocal loss of myelin, oligodendrocytes, and axons. Potential MS therapies include enhancement of remyelination by transplantation or manipulation of endogenous oligodendrocyte progenitor cells. Characteristics of endogenous oligodendrocyte progenitors in normal human brain and in MS lesions have not been studied extensively. This report describes the distribution of cells in sections from normal adult human brain and MS lesions by using antibodies directed against NG2, an integral membrane chondroitin sulfate proteoglycan expressed by oligodendrocyte progenitor cells. Stellate-shaped NG2-positive cells were detected in the white and gray matter of normal adult human brain and appeared as abundant as, but distinct from, astrocytes, oligodendrocytes, and microglia. Stellate-shaped or elongated NG2-positive cells also were detected in chronic MS lesions. A subpopulation of the elongated NG2-positive cells expressed the putative apoptotic signaling molecule p75(NTR). TUNEL-positive cells in three active, nine chronic active, and four chronic inactive lesions, however, were p75(NTR)-negative. These studies identify cells with phenotypic markers of endogenous oligodendrocyte progenitors in the mature human CNS and suggest that functional subpopulations of NG2-positive cells exist in MS lesions. Endogenous oligodendrocyte progenitor cells may represent a viable target for future therapies intended to enhance remyelination in MS patients.

Targeting of IgMκ Antibodies to Oligodendrocytes Promotes CNS Remyelination

We previously identified the remyelinating activity of a natural IgMkappa oligodendrocyte-reactive autoantibody (SCH94.03), using a virus-induced murine model of multiple sclerosis. We now describe a second mouse IgMkappa monoclonal antibody (mAb) (SCH79.08) raised against normal mouse spinal cord homogenate, which reacts with myelin basic protein and also promotes remyelination. Because these two mAbs recognize different oligodendrocyte antigens, several previously identified oligodendrocyte-reactive IgMkappa mAbs (O1, O4, A2B5, and HNK-1), each with distinct antigen specificities, were evaluated and found to promote remyelination. In contrast, IgMkappa mAbs that did not bind to oligodendrocytes showed no remyelination. One of these, CH12 IgMkappa mAb, which shares variable region cDNA sequences with SCH94.03 except for amino acid differences in the complementarity-determining region 3 in both heavy and light chains, did not bind to oligodendrocytes and did not promote remyelination. The fact that multiple oligodendrocyte-reactive antibodies with distinct antigen reactivities induce remyelination argues against direct activation by a unique cell surface receptor. These findings are most consistent with the hypothesis that the binding of mAbs to oligodendrocytes in the lesions induces myelin repair via indirect immune effector mechanisms initiated by the mu-chain. Importantly, these studies indicate that oligodendrocyte-reactive natural autoantibodies may provide a powerful and novel therapeutic means to induce remyelination in multiple sclerosis patients.