Promoting remyelination in multiple sclerosis: current drugs and future prospects

Imaging Demyelinated Axons After Spinal Cord Injuries with PET Tracer [18F]3F4AP

Spinal cord injuries (SCIs) often lead to lifelong disability. Among the various types of injuries, incomplete and discomplete injuries, where some axons remain intact, offer potential for recovery. However, demyelination of these spared axons can worsen disability. Demyelination is a reversible phenomenon, and drugs such as 4-aminopyridine (4AP), which target K+ channels in demyelinated axons, show that conduction can be restored. Yet, accurately assessing and monitoring demyelination after SCI remains challenging because of the lack of suitable imaging methods. In this study, we introduce a novel approach using the PET tracer, 3-[18F]fluoro-4-aminopyridine ([18F]3F4AP), specifically targeting K+ channels in demyelinated axons for SCI imaging. Methods: Rats with incomplete contusion injuries were imaged with [18F]3F4AP PET up to 1 mo after injury, followed by further validation of PET imaging results with autoradiography and immunohistochemistry of postmortem spinal cord tissue. A proof-of-concept study in 2 human subjects with incomplete injuries of different severities and etiologies was also performed. Results: [18F]3F4AP PET of SCI rats revealed a more than 2-fold increase in tracer binding highly localized to the injured segment of the cord at 7 d after injury relative to baseline (SUV ratio = 2.49 ± 0.09 for 7 d after injury vs. 1.14 ± 0.10 for baseline), revealing [18F]3F4AP's exceptional sensitivity to injury and its ability to detect temporal changes. Autoradiography, histology, and immunohistochemistry confirmed [18F]3F4AP's targeting of demyelinated axons. In humans, [18F]3F4AP differentiated between a severe and a largely recovered incomplete injury, indicating axonal loss and demyelination, respectively. Moreover, alterations in tracer delivery were evident on dynamic PET images, suggestive of differences in spinal cord blood flow between the injuries. Conclusion: [18F]3F4AP demonstrates efficacy in detecting incomplete SCI in both animal models and humans. The potential for monitoring post-SCI demyelination changes and response to therapy underscores the utility of [18F]3F4AP in advancing our understanding and management of SCI.

ApTOLL: A new therapeutic aptamer for cytoprotection and (re)myelination after multiple sclerosis

BACKGROUND AND PURPOSE

ApTOLL is an aptamer selected to antagonize toll-like receptor 4 (TLR4), a relevant actor for innate immunity involved in inflammatory responses in multiple sclerosis (MS) and other diseases. The currently available therapeutic arsenal to treat MS is composed of immunomodulators but, to date, there are no (re)myelinating drugs available in clinics. In our present study, we studied the effect of ApTOLL on different animal models of MS.

EXPERIMENTAL APPROACH

The experimental autoimmune encephalomyelitis (EAE) model was used to evaluate the effect of ApTOLL on reducing the inflammatory component. A more direct effect on oligodendroglia was studied with the cuprizone model and purified primary cultures of murine and human oligodendrocyte precursor cells (OPCs) isolated through magnetic-activated cell sorting (MACS) from samples of brain cortex. Also, we tested these effects in an ex vivo model of organotypic cultures demyelinated with lysolecithin (LPC).

KEY RESULTS

ApTOLL treatment positively impacted the clinical symptomatology of mice in the EAE and cuprizone models, which was associated with better preservation plus restoration of myelin and oligodendrocytes in the demyelinated lesions of animals. Restoration was corroborated on purified cultures of rodent and human OPCs.

CONCLUSION AND IMPLICATIONS

Our findings reveal a new therapeutic approach for the treatment of inflammatory and demyelinating diseases such as MS. The molecular nature of the aptamer exerts not only an anti-inflammatory effect but also neuroprotective and remyelinating effects. The excellent safety profile demonstrated by ApTOLL in animals and humans opens the door to future clinical trials in MS patients.

Improvement of the thalamocortical white matter network in people with stable treated relapsing-remitting multiple sclerosis over time

Advanced imaging techniques (tractography) enable the mapping of white matter (WM) pathways and the understanding of brain connectivity patterns. We combined tractography with a network-based approach to examine WM microstructure on a network level in people with relapsing-remitting multiple sclerosis (pw-RRMS) and healthy controls (HCs) over 2 years. Seventy-six pw-RRMS matched with 43 HCs underwent clinical assessments and 3T MRI scans at baseline (BL) and 2-year follow-up (2-YFU). Probabilistic tractography was performed, accounting for the effect of lesions, producing connectomes of 25 million streamlines. Network differences in fibre density across pw-RRMS and HCs at BL and 2-YFU were quantified using network-based statistics (NBS). Longitudinal network differences in fibre density were quantified using NBS in pw-RRMS, and were tested for correlations with disability, cognition and fatigue scores. Widespread network reductions in fibre density were found in pw-RRMS compared with HCs at BL in cortical regions, with more reductions detected at 2-YFU. Pw-RRMS had reduced fibre density at BL in the thalamocortical network compared to 2-YFU. This effect appeared after correction for age, was robust across different thresholds, and did not correlate with lesion volume or disease duration. Pw-RRMS demonstrated a robust and long-distance improvement in the thalamocortical WM network, regardless of age, disease burden, duration or therapy, suggesting a potential locus of neuroplasticity in MS. This network's role over the disease's lifespan and its potential implications in prognosis and treatment warrants further investigation.

Imaging demyelinated axons after spinal cord injuries with PET tracer [ 18 F]3F4AP

Spinal cord injuries (SCI) often lead to lifelong disability. Among the various types of injuries, incomplete and discomplete injuries, where some axons remain intact, offer potential for recovery. However, demyelination of these spared axons can worsen disability. Demyelination is a reversible phenomenon, and drugs like 4-aminopyridine (4AP), which target K+ channels in demyelinated axons, show that conduction can be restored. Yet, accurately assessing and monitoring demyelination post-SCI remains challenging due to the lack of suitable imaging methods. In this study, we introduce a novel approach utilizing the positron emission tomography (PET) tracer, [ 18 F]3F4AP, specifically targeting K+ channels in demyelinated axons for SCI imaging. Rats with incomplete contusion injuries were imaged up to one month post-injury, revealing [ 18 F]3F4AP's exceptional sensitivity to injury and its ability to detect temporal changes. Further validation through autoradiography and immunohistochemistry confirmed [ 18 F]3F4AP's targeting of demyelinated axons. In a proof-of-concept study involving human subjects, [ 18 F]3F4AP differentiated between a severe and a largely recovered incomplete injury, indicating axonal loss and demyelination, respectively. Moreover, alterations in tracer delivery were evident on dynamic PET images, suggestive of differences in spinal cord blood flow between the injuries. In conclusion, [ 18 F]3F4AP demonstrates efficacy in detecting incomplete SCI in both animal models and humans. The potential for monitoring post-SCI demyelination changes and response to therapy underscores the utility of [ 18 F]3F4AP in advancing our understanding and management of spinal cord injuries.

Notch Signaling in Central Nervous System: From Cellular Development to Multiple Sclerosis Disease

INTRODUCTION/OBJECTIVE

Multiple sclerosis (MS), is characterized by autoimmune-driven neuroinflammation, axonal degeneration, and demyelination. This study aimed to explore the therapeutic potential of targeting Notch signaling within the central nervous system (CNS) in the context of MS. Understanding the intricate roles of Notch signaling could pave the way for targeted interventions to mitigate MS progression.

METHODS

A comprehensive literature review was conducted using databases such as PubMed, Web of Science, and Scopus. Keywords such as "Notch signaling," "neuroglial interactions," and "MS" were used. The selection criteria included relevance to neuroglial interactions, peer-reviewed publications, and studies involving animal models of MS.

RESULTS

This review highlights the diverse functions of Notch signaling in CNS development, including its regulation of neural stem cell differentiation into neurons, astrocytes, and oligodendrocytes. In the context of MS, Notch signaling has emerged as a promising therapeutic target, exhibiting positive impacts on neuroprotection and remyelination. However, its intricate nature within the CNS necessitates precise modulation for therapeutic efficacy.

CONCLUSION

This study provides a comprehensive overview of the potential therapeutic role of Notch signaling in MS. The findings underscore the significance of Notch modulation for neuroprotection and remyelination, emphasizing the need for precision in therapeutic interventions. Further research is imperative to elucidate the specific underlying mechanisms involved, which will provide a foundation for targeted therapeutic strategies for the management of MS and related neurodegenerative disorders.

Remyelination in multiple sclerosis from the miRNA perspective

Remyelination relies on the repair of damaged myelin sheaths, involving microglia cells, oligodendrocyte precursor cells (OPCs), and mature oligodendrocytes. This process drives the pathophysiology of autoimmune chronic disease of the central nervous system (CNS), multiple sclerosis (MS), leading to nerve cell damage and progressive neurodegeneration. Stimulating the reconstruction of damaged myelin sheaths is one of the goals in terms of delaying the progression of MS symptoms and preventing neuronal damage. Short, noncoding RNA molecules, microRNAs (miRNAs), responsible for regulating gene expression, are believed to play a crucial role in the remyelination process. For example, studies showed that miR-223 promotes efficient activation and phagocytosis of myelin debris by microglia, which is necessary for the initiation of remyelination. Meanwhile, miR-124 promotes the return of activated microglia to the quiescent state, while miR-204 and miR-219 promote the differentiation of mature oligodendrocytes. Furthermore, miR-138, miR-145, and miR-338 have been shown to be involved in the synthesis and assembly of myelin proteins. Various delivery systems, including extracellular vesicles, hold promise as an efficient and non-invasive way for providing miRNAs to stimulate remyelination. This article summarizes the biology of remyelination as well as current challenges and strategies for miRNA molecules in potential diagnostic and therapeutic applications.

Quantification of individual remyelination during short-term disease course by synthetic magnetic resonance imaging

MRI is an important diagnostic tool for evaluation of myelin content in multiple sclerosis and other CNS diseases, being especially relevant for studies investigating remyelinating pharmacotherapies. In this study, we evaluated a new synthetic MRI–based myelin estimation in methylenetetrahydrofolate reductase deficiency as a treatable primary demyelinating disorder and compared this method with established diffusion tensor imaging in both methylenetetrahydrofolate reductase deficiency patients and healthy controls. This is the first synthetic MRI–based in vivo evaluation of treatment-associated remyelination. 1.5 T synthetic MRI and 3 T diffusion MRI were obtained from three methylenetetrahydrofolate reductase deficiency patients at baseline and 6 months after therapy initiation, as well as from age-matched healthy controls (diffusion tensor imaging: n = 14, synthetic MRI: n = 9). Global and regional synthetic MRI parameters (myelin volume fraction, proton density, and relaxation rates) were compared with diffusion metrics (fractional anisotropy, mean/radial/axial diffusivity) and related to healthy controls by calculating z-scores and z-deviation maps. Whole-brain myelin (% of intracranial volume) of the index patient was reduced to 6 versus 10% in healthy controls, which recovered to a nonetheless subnormal level of 6.6% following initiation of high-dosage betaine. Radial diffusivity was higher at baseline compared with healthy controls (1.34 versus 0.79 × 10⁻³ mm²/s), recovering at follow-up (1.19 × 10⁻³ mm²/s). The index patient’s lesion volume diminished by 58% under treatment. Regional analysis within lesion area and atlas-based regions revealed lower mean myelin volume fraction (12.7_Baseline/14.71_Follow-up%) and relaxation rates, higher proton density, as well as lower fractional anisotropy and higher radial diffusivity (1.08 × 10⁻³_Baseline/0.94 × 10⁻³_Follow-up) compared with healthy controls. The highest z-scores were observed for myelin volume fraction in the posterior thalamic radiation, with greater deviation from controls at baseline and reduced deviation at follow-up. Z-deviations of diffusion metrics were less pronounced for radial and mean diffusivity than for myelin volume fraction. Z-maps for myelin volume fraction of the index patient demonstrated high deviation within and beyond lesion areas, among others in the precentral and postcentral gyrus, as well as in the cerebellum, and partial remission of these alterations at follow-up, while radial diffusivity demonstrated more widespread deviations in supra- and infratentorial regions. Concordant changes of myelin volume fraction and radial diffusivity after treatment initiation, accompanied by dramatic clinical and paraclinical improvement, indicate the consistency of the methods, while myelin volume fraction seems to characterize remyelinated regions more specifically. Synthetic MRI–based myelin volume fraction provides myelin estimation consistent with changes of diffusion metrics to monitor short-term myelin changes on individual patient level.

Delayed Maturation of Oligodendrocyte Progenitors by Microgravity: Implications for Multiple Sclerosis and Space Flight

In previous studies, we examined the effects of space microgravity on human neural stem cells. To date, there are no studies on a different type of cell that is critical for myelination and electrical signals transmission, oligodendrocyte progenitors (OLPs). The purpose of the present study was to examine the behavior of space-flown OLPs (SPC-OLPs) as they were adapting to Earth's gravity. We found that SPC-OLPs survived, and most of them proliferated normally. Nonetheless, some of them displayed incomplete cytokinesis. Both morphological and ontogenetic analyses showed that they remained healthy and expressed the immature OLP markers Sox2, PDGFR-α, and transferrin (Tf) after space flight, which confirmed that SPC-OLPs displayed a more immature phenotype than their ground control (GC) counterparts. In contrast, GC OLPs expressed markers that usually appear later (GPDH, O4, and ferritin), indicating a delay in SPC-OLPs' development. These cells remained immature even after treatment with culture media designed to support oligodendrocyte (OL) maturation. The most remarkable and surprising finding was that the iron carrier glycoprotein Tf, previously described as an early marker for OLPs, was expressed ectopically in the nucleus of all SPC-OLPs. In contrast, their GC counterparts expressed it exclusively in the cytoplasm, as previously described. In addition, analysis of the secretome demonstrated that SPC-OLPs contained 3.5 times more Tf than that of GC cells, indicating that Tf is gravitationally regulated, opening two main fields of study to understand the upregulation of the Tf gene and secretion of the protein that keep OLPs at a progenitor stage rather than moving forward to more mature phenotypes. Alternatively, because Tf is an autocrine and paracrine factor in the central nervous system (CNS), in the absence of neurons, it accumulated in the secretome collected after space flight. We conclude that microgravity is becoming a novel platform to study why in some myelin disorders OLPs are present but do not mature.

Menstrual blood-derived mesenchymal stromal cells efficiently ameliorate experimental autoimmune encephalomyelitis by inhibiting T cell activation in mice

Background

Immunosuppressive properties grant mesenchymal stromal cells (MSCs) promising potential for treating autoimmune diseases. As autologous MSCs suffer from limited availability, the readily available allogeneic MSCs isolated from menstrual blood (MB-MSCs) donated by young, healthy individuals offer great potential. Here, we evaluate the therapeutic potential of MB-MSCs as ready-to-use allo-MSCs in multiple sclerosis, an autoimmune disease developed by the activation of myelin sheath-reactive Th1 and Th17 cells, by application in its animal model experimental autoimmune encephalomyelitis (EAE).

Methods

We assessed the therapeutic effect of MB-MSCs transplanted via either intravenous (i.v.) or intraperitoneal (i.p.) route in EAE in comparison with umbilical cord-derived MSCs (UC-MSCs). We used histology to assess myelin sheath integrity and infiltrated immune cells in CNS and flow cytometry to evaluate EAE-associated inflammatory T cells and antigen-presenting cells in lymphoid organs.

Results

We observed disease-ameliorating effects of MB-MSCs when transplanted at various stages of EAE (day − 1, 6, 10, and 19), via either i.v. or i.p. route, with a potency comparable to UC-MSCs. We observed reduced Th1 and Th17 cell responses in mice that had received MB-MSCs via either i.v. or i.p. injection. The repressed Th1 and Th17 cell responses were associated with a reduced frequency of plasmacytoid dendritic cells (pDCs) and a suppressed co-stimulatory capacity of pDCs, cDCs, and B cells.

Conclusions

Our data demonstrate that the readily available MB-MSCs significantly reduced the disease severity of EAE upon transplantation. Thus, they have the potential to be developed as ready-to-use allo-MSCs in MS-related inflammation.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02838-8.

Cost of Illness of Multiple Sclerosis in Isfahan, Iran, From a Social Perspective: A Comparison of the Human-Capital and Friction-Cost Methods

OBJECTIVES

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system that is characterized by demyelination and neurodegenerative changes and associated with high levels of disability. This study aimed to investigate direct and indirect costs of illness of patients with MS in Isfahan using and comparing human-capital and friction-cost methods from a societal perspective.

METHODS

A total of 300 patients with MS of 2 main centers of the disease in Isfahan, the MS center of Ayatollah Kashani hospital and Isfahan MS center, were included. Patient's demographic characteristics, disease information, and annual social costs (2018-2019) were collected using data collection form. Both the human-capital and friction-cost methods were applied and compared with value indirect costs because of loss of productivity.

RESULTS

From the social perspective, the average annual total cost of MS disease was estimated to be 1 441 163 710 rials (34 313 US dollar [USD]) per patient using the human-capital approach and 1 434 832 004 rials (34 162 USD) with the use of friction-cost method, from which 1 428 668 396 rials (34 016 USD) was related to direct costs. The main direct costs were related to disease-modifying therapies and referring to other physicians and hospitals. The cost of loss of production was greater with human-capital approach in comparison with friction-cost method.

CONCLUSIONS

The most prominent cost in MS disease is related to drug costs. The indirect costs were sensitive to the methods, applied in the study.

Kinetics of myelin breakdown products: A labeling study in patients with progressive multiple sclerosis

The majority of disease modifying therapies for multiple sclerosis (MS) reduce inflammation, but do no’t target remyelination. Development of remyelinating therapies will benefit from a method to quantify myelin kinetics in patients with MS. We labeled myelin in vivo with deuterium, and modeled kinetics of myelin breakdown products β‐galactosylceramide (β‐GalC) and N‐Octadecanoyl‐sulfatide (NO‐Sulf). Five patients with MS received 120 ml 70% D₂O daily for 70 days and were compared with six healthy subjects who previously received the same procedure. Mass spectrometry and compartmental modeling were used to quantify the turnover rate of β‐GalC and NO‐Sulf in cerebrospinal fluid (CSF). Turnover rate constants of the fractions of β‐GalC and NO‐Sulf with non‐negligible turnover were 0.00186 and 0.00714, respectively, in both healthy subjects and patients with MS. The turnover half‐life of β‐GalC and NO‐Sulf was calculated as 373 days and 96.5 days, respectively. The effect of MS on the NO‐Sulf (49.4% lower fraction with non‐negligible turnover) was more pronounced compared to the effect on β‐GalC turnover (18.3% lower fraction with non‐negligible turnover). Kinetics of myelin breakdown products in the CSF are different in patients with MS compared with healthy subjects. This may be caused by slower myelin production in these patients, by a higher level of degradation of a more stable component of myelin, or, most likely, by a combination of these two processes. Labeling myelin breakdown products is a useful method that can be used to quantify myelin turnover in patients with progressive MS and can therefore be used in proof‐of‐concept studies with remyelination therapies.

Connecting Neuroinflammation and Neurodegeneration in Multiple Sclerosis: Are Oligodendrocyte Precursor Cells a Nexus of Disease?

The pathology in neurodegenerative diseases is often accompanied by inflammation. It is well-known that many cells within the central nervous system (CNS) also contribute to ongoing neuroinflammation, which can promote neurodegeneration. Multiple sclerosis (MS) is both an inflammatory and neurodegenerative disease in which there is a complex interplay between resident CNS cells to mediate myelin and axonal damage, and this communication network can vary depending on the subtype and chronicity of disease. Oligodendrocytes, the myelinating cell of the CNS, and their precursors, oligodendrocyte precursor cells (OPCs), are often thought of as the targets of autoimmune pathology during MS and in several animal models of MS; however, there is emerging evidence that OPCs actively contribute to inflammation that directly and indirectly contributes to neurodegeneration. Here we discuss several contributors to MS disease progression starting with lesion pathology and murine models amenable to studying particular aspects of disease. We then review how OPCs themselves can play an active role in promoting neuroinflammation and neurodegeneration, and how other resident CNS cells including microglia, astrocytes, and neurons can impact OPC function. Further, we outline the very complex and pleiotropic role(s) of several inflammatory cytokines and other secreted factors classically described as solely deleterious during MS and its animal models, but in fact, have many neuroprotective functions and promote a return to homeostasis, in part via modulation of OPC function. Finally, since MS affects patients from the onset of disease throughout their lifespan, we discuss the impact of aging on OPC function and CNS recovery. It is becoming clear that OPCs are not simply a bystander during MS progression and uncovering the active roles they play during different stages of disease will help uncover potential new avenues for therapeutic intervention.

Identification of novel myelin repair drugs by modulation of oligodendroglial differentiation competence

BACKGROUND

In multiple sclerosis loss of myelin and oligodendrocytes impairs saltatory signal transduction and leads to neuronal loss and functional deficits. Limited capacity of oligodendroglial precursor cells to differentiate into mature cells is the main reason for inefficient myelin repair in the central nervous system. Drug repurposing constitutes a powerful approach for identification of pharmacological compounds promoting this process.

METHODS

A phenotypic compound screening using the subcellular distribution of a potent inhibitor of oligodendroglial cell differentiation, namely p57kip2, as differentiation competence marker was conducted. Hit compounds were validated in terms of their impact on developmental cell differentiation and myelination using both rat and human primary cell cultures and organotypic cerebellar slice cultures, respectively. Their effect on spontaneous remyelination was then investigated following cuprizone-mediated demyelination of the corpus callosum.

FINDINGS

A number of novel small molecules able to promote oligodendroglial cell differentiation were identified and a subset was found to foster human oligodendrogenesis as well as myelination ex vivo. Among them the steroid danazol and the anthelminthic parbendazole were found to increase myelin repair.

INTERPRETATION

We provide evidence that early cellular processes involved in differentiation decisions are applicable for the identification of regeneration promoting drugs and we suggest danazol and parbendazole as potent therapeutic candidates for demyelinating diseases.

FUNDING

This work was supported by the Jürgen Manchot Foundation, Düsseldorf; Research Commission of the Medical Faculty of Heinrich-Heine-University Düsseldorf; Christiane and Claudia Hempel Foundation; Stifterverband/Novartisstiftung; James and Elisabeth Cloppenburg, Peek and Cloppenburg Düsseldorf Stiftung and International Progressive MS Alliance (BRAVEinMS).

CZ-7, a new derivative of Claulansine F, promotes remyelination induced by cuprizone by enhancing myelin debris clearance

The mechanism of demyelinating diseases is controversial, while demyelination and remyeliantion disorder is the acknowledged etiology and therapeutic target. Untill now, there is no efficient therapy for these diseases. CZ-7, a new derivative of Claulansine F, which has been reported before, were investigated its pro-remyelination effect and its associated mechanism in cuprizone (CPZ)-induced demyelination model. In this study, male C57BL/6 mice were subjected to CPZ (300 mg/kg) through intragastric gavage and were orally administered CZ-7 (20 mg/kg) meanwhile. The results of weight monitoring and behavioral testing showed that CZ-7 can significantly improve behavior dysfunction in the demyelinating mice. Luxol-fast blue (LFB) staining, myelin basic protein (MBP) immunostaining, transmission electron microscopy (TEM) and QPCR results indicated the therapeutic effect of CZ-7 on CPZ mice model. Furthermore, degraded myelin basic protein (dMBP) immunofluorescent staining and oil red O staining showed that CZ-7 contributed to the clearance of degraded myelin debris. More microglia displayed phagocytic shape assembled in corpus callosum (CC) and there was an active process of phagocytosis in microglia after CZ-7 treatment. Immunofluorescent staining and QPCR analysis revealed the M2-polarized phenotype switch of microglia in the process of myelin debris removel, which demostrated the microenvironment improvement of CZ-7. Moreover, immunofluorescent staining of NG2 and O4 demonstated that more oligodendrocyte precursor cells (OPCs) existed in CC after CZ-7 treatment. In conclusion, our results demonstrated CZ-7 has a potential therapeutic effect for MS and other demyelinating diseases through enhancing myelin debris clearance to improve the microenvironment.

Gene Therapy Approaches in an Autoimmune Demyelinating Disease: Multiple Sclerosis

Multiple Sclerosis (MS) is the most common autoimmune demyelinating disease of the Central Nervous System (CNS). It is a multifactorial disease which develops in an immune-mediated way under the influences of both genetic and environmental factors. Demyelination is observed in the brain and spinal cord leading to neuro-axonal damage in patients with MS. Due to the infiltration of different immune cells such as T-cells, B-cells, monocytes and macrophages, focal lesions are observed in MS. Currently available medications treating MS are mainly based on two strategies; i) to ease specific symptoms or ii) to reduce disease progression. However, these medications tend to induce different adverse effects with limited therapeutic efficacy due to the protective function of the blood-brain barrier. Therefore, researchers have been working for the last four decades to discover better solutions by introducing gene therapy approaches in treating MS generally by following three strategies, i) prevention of specific symptoms, ii) halt or reverse disease progression and iii) heal CNS damage by promoting remyelination and axonal repair. In last two decades, there have been some remarkable successes of gene therapy approaches on the experimental mice model of MS - experimental autoimmune encephalomyelitis (EAE) which suggests that it is not far that the gene therapy approaches would start in human subjects ensuring the highest levels of safety and efficacy. In this review, we summarised the gene therapy approaches attempted in different animal models towards treating MS.

Monocarboxylate Transporter 8 Deficiency: Delayed or Permanent Hypomyelination?

Monocarboxylate transporter 8 (MCT8) deficiency or the Allan-Herndon-Dudley Syndrome (AHDS) is an X-linked psychomotor disability syndrome with around 320 clinical cases described worldwide. SLC16A2 gene mutations, encoding the thyroid hormone (TH) transporter MCT8, result in intellectual disability due to impaired TH uptake in the developing brain. MCT8 deficiency is a multi-organ affecting disease with a predominant neuronal cell-based pathology, with the glial component inadequately investigated. However, deficiency in myelin, a key component of white matter (WM) enabling fast nerve conduction, is a TH-dependent hallmark of the disease. Nevertheless, analysis of the myelin status in AHDS patients has led to conflicting interpretations. The majority of individual case studies reported delayed myelination, that was restored later in life. In contrast, post-mortem studies and high-resolution MRIs detected WM (micro-) abnormalities throughout adolescence, suggesting permanent hypomyelination. Thus, interpretations vary depending on methodology to investigate WM microstructure. Further, it is unknown whether the mutation within the MCT8 is linked to the severity of the myelin deficiency. Consequently, terminology is inconsistent among reports, and AHDS is occasionally misdiagnosed as another WM disorder. The evolutionary conserved TH signaling pathway that promotes the generation of myelinating oligodendrocytes enabled deciphering how the lack of MCT8 might affect myelinogenesis. Linking patient findings on myelination to those obtained from models of MCT8 deficiency revealed underlying pathophysiological mechanisms, but knowledge gaps remain, notably how myelination progresses both spatially and temporally in MCT8 deficiency. This limits predicting how myelin integrity might benefit therapeutically, and when to initiate. A recurrent observation in clinical trials is the absence of neurological improvement. Testing MCT8-independent thyromimetics in models, and evaluating treatments used in other demyelinating diseases, despite different etiologies, is crucial to propose new therapeutic strategies combatting this devastating disease.

Chromatin modification and epigenetic control in functional nerve regeneration

The repair and functional recovery of the nervous system is a highly regulated process that requires the coordination of many different components including the proper myelination of regenerated axons. Dysmyelination and remyelination failures after injury result in defective nerve conduction, impairing normal nervous system functions. There are many convergent regulatory networks and signaling mechanisms between development and regeneration. For instance, the regulatory mechanisms required for oligodendrocyte lineage progression could potentially play fundamental roles in myelin repair. In recent years, epigenetic chromatin modifications have been implicated in CNS myelination and functional nerve restoration. The pro-regenerative transcriptional program is likely silenced or repressed in adult neural cells including neurons and myelinating cells in the central and peripheral nervous systems limiting the capacity for repair after injury. In this review, we will discuss the roles of epigenetic mechanisms, including histone modifications, chromatin remodeling, and DNA methylation, in the maintenance and establishment of the myelination program during normal oligodendrocyte development and regeneration. We also discuss how these epigenetic processes impact myelination and axonal regeneration, and facilitate the improvement of current preclinical therapeutics for functional nerve regeneration in neurodegenerative disorders or after injury.

Histamine H3 receptor antagonists/inverse agonists: Where do they go?

Since the discovery of the histamine H₃ receptor in 1983, tremendous advances in the pharmacological aspects of H₃ receptor antagonists/inverse agonists have been accomplished in preclinical studies. At present, there are several drug candidates that reached clinical trial studies for various indications. However, entrance of these candidates to the pharmaceutical market is not free from challenges, and a variety of difficulties is engaged with their developmental process. In this review, the potential role of H₃ receptors in the pathophysiology of various central nervous system, metabolic and allergic diseases is discussed. Thereafter, the current status for H₃ receptor antagonists/inverse agonists in ongoing clinical trial studies is reviewed and obstacles in developing these agents are emphasized.

Glatiramer acetate: A complex drug beyond biologics

Complex drugs may be either biological, if the active ingredients are derived from a biological source, or non-biological, if obtained by chemical synthesis. In both cases, their quality depends considerably on the manufacturing process. In the case of Non Biological Complex Drugs (NBCDs), complexity may arise either from the active substance, as in the case of glatiramer acetate, or from other sources, such as the formulation, as in the case of liposomes. In this paper, the case of glatiramer acetate (GA) - a NBCD relevant for clinical and economic reasons - is considered and the differences between US and EU regulatory approaches to GA marketing authorization are highlighted. Indeed, though US and EU regulatory agencies have chosen a generic approach integrated with additional data the implementation is different in the two jurisdictions. In the US, the additional data required are listed in a product specific guideline and copies of Copaxone® have been approved as generics. In the EU, instead regulatory agencies followed a hybrid approach requiring an additional comparative study, and interchangeability policies and substitution schemes have been left to national agencies.

Current advancements in promoting remyelination in multiple sclerosis

Current multiple sclerosis (MS) therapies are effective in reducing relapse rate, short-term measures of disability, and magnetic resonance imaging (MRI) measures of inflammation in relapsing remitting MS (RRMS), whereas in progressive/degenerative disease phases these medications are of little or no benefit. Therefore, the development of new therapies aimed at reversing neurodegeneration is of great interest. Remyelination, which is usually a spontaneous endogenous process, is achieved when myelin-producing oligodendrocytes are generated from oligodendrocyte precursor cells (OPCs). Even though these precursor cells are abundant in MS brains, their regeneration capacity is limited. Enhancing the generation of myelin-producing cells is therefore a major focus of MS research. Here we present an overview of the different advancements in the field of remyelination, including suitable animal models for testing remyelination therapies, approved medications with a proposed role in regeneration, myelin repair treatments under investigation in clinical trials, as well as future therapeutics aimed at facilitating myelin repair.

Thymosins in multiple sclerosis and its experimental models: moving from basic to clinical application

BACKGROUND

Multiple sclerosis (MS) afflicts more than 2.5 million individuals worldwide and this number is increasing over time. Within the past years, a great number of disease-modifying treatments have emerged; however, efficacious treatments and a cure for MS await discovery. Thymosins, soluble hormone-like peptides produced by the thymus gland, can mediate immune and non-immune physiological processes and have gained interest in recent years as therapeutics in inflammatory and autoimmune diseases.

METHODS

Pubmed was searched with no time constraints for articles using a combination of the keywords "thymosin/s" or "thymus factor/s" AND "multiple sclerosis", mesh terms with no language restriction.

RESULTS

Here, we review the state-of-the-art on the effects of thymosins on MS and its experimental models. In particular, we describe what is known in this field on the roles of thymosin-α1 (Tα1) and -β4 (Tβ4) as potential anti-inflammatory as well as neuroprotective and remyelinating molecules and their mechanisms of action.

CONCLUSION

Based on the data that Tα1 and Tβ4 act as anti-inflammatory molecules and as inducers of myelin repair and neuronal protection, respectively, a possible therapeutic application in MS for Tα1 and Tβ4 alone or combined with other approved drugs may be envisaged. This approach is reasonable in light of the current clinical usage of Tα1 and data demonstrating the safety, tolerability and efficacy of Tβ4 in clinical practice.

Detecting Demyelination by PET: The Lesion as Imaging Target

Noninvasive imaging of demyelination and remyelination is critical for diagnosis and clinical management of demyelinating diseases. Positron emission tomography (PET) has the potential to complement magnetic resonance imaging (MRI) by providing a quantitative measure specific to demyelination. In Brugarolas et al’s study¹, we describe the development of the first PET tracer for voltage-gated K⁺ channels based on a clinically approved drug for multiple sclerosis that can be used for imaging demyelination in animal models.

Leukemia inhibitory factor inhibits erythropoietin-induced myelin gene expression in oligodendrocytes

Background

The pro-myelinating effects of leukemia inhibitory factor (LIF) and other cytokines of the gp130 family, including oncostatin M (OSM) and ciliary neurotrophic factor (CNTF), have long been known, but controversial results have also been reported. We recently overexpressed erythropoietin receptor (EPOR) in rat central glia-4 (CG4) oligodendrocyte progenitor cells (OPCs) to study the mechanisms mediating the pro-myelinating effects of erythropoietin (EPO). In this study, we investigated the effect of co-treatment with EPO and LIF.

Methods

Gene expression in undifferentiated and differentiating CG4 cells in response to EPO and LIF was analysed by DNA microarrays and by RT-qPCR. Experiments were performed in biological replicates of N ≥ 4. Functional annotation and biological term enrichment was performed using DAVID (Database for Annotation, Visualization and Integrated Discovery). The gene-gene interaction network was visualised using STRING (Search Tool for the Retrieval of Interacting Genes).

Results

In CG4 cells treated with 10 ng/ml of EPO and 10 ng/ml of LIF, EPO-induced myelin oligodendrocyte glycoprotein (MOG) expression, measured at day 3 of differentiation, was inhibited ≥4-fold (N = 5, P < 0.001). Inhibition of EPO-induced MOG was also observed with OSM and CNTF. Analysis of the gene expression profile of CG4 differentiating cells treated for 20 h with EPO and LIF revealed LIF inhibition of EPO-induced genes involved in lipid transport and metabolism, previously identified as positive regulators of myelination in this system. In addition, among the genes induced by LIF, and not by differentiation or by EPO, the role of suppressor of cytokine signaling 3 (SOCS3) and toll like receptor 2 (TLR2) as negative regulators of myelination was further explored. LIF-induced SOCS3 was associated with MOG inhibition; Pam3, an agonist of TLR2, inhibited EPO-induced MOG expression, suggesting that TLR2 is functional and its activation decreases myelination.

Conclusions

Cytokines of the gp130 family may have negative effects on myelination, depending on the cytokine environment.

Electronic supplementary material

The online version of this article (10.1186/s10020-018-0052-3) contains supplementary material, which is available to authorized users.

N-Phenylquinazolin-2-amine Yhhu4952 as a novel promotor for oligodendrocyte differentiation and myelination

Oligodendrocytes are a type of glial cells that ensheath multiple neuronal axons and form myelin. Under pathological conditions, such as multiple sclerosis (MS), inflammatory damage to myelin and oligodendrocytes leads to demyelination. Although the demyelinated regions can partially resolve functional deficits through remyelination, however, as the disease progresses, remyelination typically becomes incomplete and ultimately fails. One possible explanation for this failure is the activation of the Notch pathway in MS lesions, which impedes oligodendrocyte precursor cells (OPCs) at maturation. This leads to a potential target for remyelination. Here, we have identified a compound Yhhu4952 that promoted the maturation of cultured OPCs in a dose-dependent and time-dependent manner. Neonatal rats showed a significant increase in the expression of myelin basic protein (MBP) and the prevalence of mature oligodendrocytes in the corpus callosum after Yhhu4952 treatment. The compound was also effective in promoting remyelination in cuprizone-induced demyelination model and improving severity scores in experimental autoimmune encephalomyelitis (EAE) model. Mechanism studies revealed that Yhhu4952 promotes OPC differentiation through the inhibition of the Jagged1-Notch1 pathway. These findings suggest Yhhu4952 is potentially useful for proceeding oligodendrocyte differentiation and remyelination.

Effects of inflammatory cytokines IFN-γ, TNF-α and IL-6 on the viability and functionality of human pluripotent stem cell-derived neural cells

Multiple Sclerosis (MS) is an inflammatory neurodegenerative disease, where neural progenitor cell (NPC) transplantation has been suggested as a potential neuroprotective therapeutic strategy. Since the effect of inflammation on NPCs is poorly known, their effect on the survival and functionality of human NPCs were studied. Treatment with interleukin (IL)-6, tumor necrosis factor (TNF)-α and interferon (IFN)-γ did not induced cytotoxicity, but IFN-γ treatment showed decreased proliferation and neuronal migration. By contrast, increased proliferation and inhibition of electrical activity were detected after TNF-α treatment. Treatments induced secretion of inflammatory factors. Inflammatory cytokines appear to modulate proliferation as well as the cellular and functional properties of human NPCs.

Costs and quality of life by disability among people with multiple sclerosis: a register-based study in Sweden

Background

Population-based estimates of costs of illness and health-related quality of life, by disability levels among people with multiple sclerosis, are lacking.

Objectives

To estimate the annual costs of illness and health-related quality of life, by disability levels, among multiple sclerosis patients, 21–64 years of age.

Methods

Microdata from Swedish nationwide registers were linked to estimate the prevalence-based costs of illness in 2013, including direct costs (prescription drug use and specialised healthcare) and indirect costs (calculated using sick leave and disability pension), and health-related quality of life (estimated from the EQ-5D). Disability level was measured by the Expanded Disability Status Scale (EDSS).

Results

Among 8906 multiple sclerosis patients, EDSS 0.0–3.5 and 7.0–9.5 were associated with mean indirect costs of SEK 117,609 and 461,357, respectively, whereas direct costs were similar between the categories (SEK 117,423 and 102,714, respectively). Prescription drug costs represented 40% of the costs of illness among multiple sclerosis patients with low EDSS, while among patients with high EDSS more than 80% were indirect costs. Among the 1684 individuals who had reported both EQ-5D and EDSS, the lowest health-related quality of life scores were found among those with a high EDSS.

Conclusion

Among people with multiple sclerosis, we confirmed higher costs and lower health-related quality of life in higher disability levels, in particular high indirect costs.

A systems medicine approach reveals disordered immune system and lipid metabolism in multiple sclerosis patients

Identification of autoimmune processes and introduction of new autoantigens involved in the pathogenesis of multiple sclerosis (MS) can be helpful in the design of new drugs to prevent unresponsiveness and side effects in patients. To find significant changes, we evaluated the autoantibody repertoires in newly diagnosed relapsing-remitting MS patients (NDP) and those receiving disease-modifying therapy (RP). Through a random peptide phage library, a panel of NDP- and RP-specific peptides was identified, producing two protein data sets visualized using Gephi, based on protein--protein interactions in the STRING database. The top modules of NDP and RP networks were assessed using Enrichr. Based on the findings, a set of proteins, including ATP binding cassette subfamily C member 1 (ABCC1), neurogenic locus notch homologue protein 1 (NOTCH1), hepatocyte growth factor receptor (MET), RAF proto-oncogene serine/threonine-protein kinase (RAF1) and proto-oncogene vav (VAV1) was found in NDP and was involved in over-represented terms correlated with cell-mediated immunity and cancer. In contrast, transcription factor RelB (RELB), histone acetyltransferase p300 (EP300), acetyl-CoA carboxylase 2 (ACACB), adiponectin (ADIPOQ) and phosphoenolpyruvate carboxykinase 2 mitochondrial (PCK2) had major contributions to viral infections and lipid metabolism as significant events in RP. According to these findings, further research is required to demonstrate the pathogenic roles of such proteins and autoantibodies targeting them in MS and to develop therapeutic agents which can ameliorate disease severity.

C-Phycocyanin and Phycocyanobilin as Remyelination Therapies for Enhancing Recovery in Multiple Sclerosis and Ischemic Stroke: A Preclinical Perspective

Myelin loss has a crucial impact on behavior disabilities associated to Multiple Sclerosis (MS) and Ischemic Stroke (IS). Although several MS therapies are approved, none of them promote remyelination in patients, limiting their ability for chronic recovery. With no available therapeutic options, enhanced demyelination in stroke survivors is correlated with a poorer behavioral recovery. Here, we show the experimental findings of our group and others supporting the remyelinating effects of C-Phycocyanin (C-PC), the main biliprotein of Spirulina platensis and its linked tetrapyrrole Phycocyanobilin (PCB), in models of these illnesses. C-PC promoted white matter regeneration in rats and mice affected by experimental autoimmune encephalomyelitis. Electron microscopy analysis in cerebral cortex from ischemic rats revealed a potent remyelinating action of PCB treatment after stroke. Among others biological processes, we discussed the role of regulatory T cell induction, the control of oxidative stress and pro-inflammatory mediators, gene expression modulation and COX-2 inhibition as potential mechanisms involved in the C-PC and PCB effects on the recruitment, differentiation and maturation of oligodendrocyte precursor cells in demyelinated lesions. The assembled evidence supports the implementation of clinical trials to demonstrate the recovery effects of C-PC and PCB in these diseases.

Computational comparison of two new fusion proteins for multiple sclerosis

Multiple sclerosis (MS), as one of the human autoimmune diseases, demyelinates the neurons of the central nervous system (CNS). Activation of the T cells which target the CNS antigens is the first autoimmune event in MS. Myelin oligodendrocyte glycoprotein (MOG) and myelin basic protein (MBP) are two proteins of the myelin sheath and have been shown to be among the high antigens contributing to the pathogenesis of MS. Production of the drugs with high specificity for the immune system diseases is a concern for various researchers. Therefore, tolerogenic vaccines are considered as a new strategy for the treatment of MS by presenting specific antigens. This study aimed to design and compare two fusion proteins by a combination of two neuroantigens linked to interleukin-16 (IL-16) (MOG-Linker-MBP-IL16 and MBP-Linker-MOG-IL16) as vaccines for MS. In this study, at first two models MOG (aa 11-30) linked to MBP (aa 13-32) was made by Modeler 9.10 and simulated for 20 ns via Gromacs 5.1.1 package. Then simulated antigen domains connected to the N-terminal domain of IL-16 and obtained structures simulated for 50 ns. The results revealed that both constructs had stable structures and the linker could keep two antigenic fragments separate enough, preventing undesired interactions. While MOG-Linker-MBP-IL16 showed better solubility, more accessible surface areas, more flexibility of its IL-16 domain, and better functionality of its IL-16 domain as well as more specific cleavage of its related epitopes after endocytosis lead to a better presentation of its antigenic property.

Erythropoietin Increases Myelination in Oligodendrocytes: Gene Expression Profiling Reveals Early Induction of Genes Involved in Lipid Transport and Metabolism

Several studies have shown that erythropoietin (EPO) has neuroprotective or neuroreparative actions on diseases of the nervous system and that improves oligodendrocyte (OL) differentiation and myelination in vivo and in vitro. This study aims at investigating the early molecular mechanisms for the pro-myelinating action of EPO at the gene expression level. For this purpose, we used a differentiating OL precursor cell line, rat central glia-4 cells. Cells were differentiated or not, and then treated with EPO for 1 or 20 h. RNA was extracted and changes in the gene expression profile were assessed using microarray analysis. Experiments were performed in biological replicates of n = 4. Differentiation alone changed the expression of 11% of transcripts (2,663 out of 24,272), representing 2,436 genes, half of which were upregulated and half downregulated. At 20 h of treatment, EPO significantly affected the expression of 99 genes that were already regulated by differentiation and of 150 genes that were not influenced by differentiation alone. Analysis of the transcripts most upregulated by EPO identified several genes involved in lipid transport (e.g., Cd36) and lipid metabolism (Ppargc1a/Pgc1alpha, Lpin1, Pnlip, Lpin2, Ppard, Plin2) along with Igf1 and Igf2, growth factors known for their pro-myelinating action. All these genes were only induced by EPO and not by differentiation alone, except for Pnlip which was highly induced by differentiation and augmented by EPO. Results were validated by quantitative PCR. These findings suggest that EPO might increase remyelination by inducing insulin-like growth factors and increasing lipid metabolism.

Oligodendroglial TNFR2 Mediates Membrane TNF-Dependent Repair in Experimental Autoimmune Encephalomyelitis by Promoting Oligodendrocyte Differentiation and Remyelination

Tumor necrosis factor (TNF) is associated with the pathophysiology of various neurological disorders, including multiple sclerosis. It exists as a transmembrane form tmTNF, signaling via TNF receptor 2 (TNFR2) and TNFR1, and a soluble form, solTNF, signaling via TNFR1. Multiple sclerosis is associated with the detrimental effects of solTNF acting through TNFR1, while tmTNF promotes repair and remyelination. Here we demonstrate that oligodendroglial TNFR2 is a key mediator of tmTNF-dependent protection in experimental autoimmune encephalomyelitis (EAE). CNP-cre:TNFR2(fl/fl) mice with TNFR2 ablation in oligodendrocytes show exacerbation of the disease with increased axon and myelin pathology, reduced remyelination, and increased loss of oligodendrocyte precursor cells and mature oligodendrocytes. The clinical course of EAE is not improved by the solTNF inhibitor XPro1595 in CNP-cre:TNFR2(fl/fl) mice, indicating that for tmTNF to promote recovery TNFR2 in oligodendrocytes is required. We show that TNFR2 drives differentiation of oligodendrocyte precursor cells, but not proliferation or survival. TNFR2 ablation leads to dysregulated expression of microRNAs, among which are regulators of oligodendrocyte differentiation and inflammation, including miR-7a. Our data provide the first direct in vivo evidence that TNFR2 in oligodendrocytes is important for oligodendrocyte differentiation, thereby sustaining tmTNF-dependent repair in neuroimmune disease. Our studies identify TNFR2 in the CNS as a molecular target for the development of remyelinating agents, addressing the most pressing need in multiple sclerosis therapy nowadays.

SIGNIFICANCE STATEMENT

Our study, using novel TNF receptor 2 (TNFR2) conditional KO mice with selective TNFR2 ablation in oligodendrocytes, provides the first direct evidence that TNFR2 is an important signal for oligodendrocyte differentiation. Following activation by transmembrane TNF, TNFR2 initiates pathways that drive oligodendrocytes into a reparative mode contributing to remyelination following disease. This identifies TNFR2 as a new molecular target for the development of therapeutic agents in multiple sclerosis.

Drug discovery for remyelination and treatment of MS

Glia constitute the majority of the cells in our nervous system, yet there are currently no drugs that target glia for the treatment of disease. Given ongoing discoveries of the many roles of glia in numerous diseases of the nervous system, this is likely to change in years to come. Here we focus on the possibility that targeting the oligodendrocyte lineage to promote regeneration of myelin (remyelination) represents a therapeutic strategy for the treatment of the demyelinating disease multiple sclerosis, MS. We discuss how hypothesis driven studies have identified multiple targets and pathways that can be manipulated to promote remyelination in vivo, and how this work has led to the first ever remyelination clinical trials. We also highlight how recent chemical discovery screens have identified a host of small molecule compounds that promote oligodendrocyte differentiation in vitro. Some of these compounds have also been shown to promote myelin regeneration in vivo, with one already being trialled in humans. Promoting oligodendrocyte differentiation and remyelination represents just one potential strategy for the treatment of MS. The pathology of MS is complex, and its complete amelioration may require targeting multiple biological processes in parallel. Therefore, we present an overview of new technologies and models for phenotypic analyses and screening that can be exploited to study complex cell-cell interactions in in vitro and in vivo systems. Such technological platforms will provide insight into fundamental mechanisms and increase capacities for drug-discovery of relevance to glia and currently intractable disorders of the CNS.

Leukemia/lymphoma-related factor (LRF) exhibits stage- and context-dependent transcriptional controls in the oligodendrocyte lineage and modulates remyelination

Leukemia/lymphoma‐related factor (LRF), a zinc‐finger transcription factor encoded by Zbtb7a, is a protooncogene that regulates differentiation in diverse cell lineages, and in the CNS, its function is relatively unexplored. This study is the first to examine the role of LRF in CNS pathology. We first examined LRF expression in a murine viral model of spinal cord demyelination with clinically relevant lesion characteristics. LRF was rarely expressed in oligodendrocyte progenitors (OP) yet, was detected in nuclei of the majority of oligodendrocytes in healthy adult CNS and during remyelination. Plp/CreER^T:Zbtb7a^fl/fl mice were then used with cuprizone demyelination to determine the effect of LRF knockdown on oligodendrocyte repopulation and remyelination. Cuprizone was given for 6 weeks to demyelinate the corpus callosum. Tamoxifen was administered at 4, 5, or 6 weeks after the start of cuprizone. Tamoxifen‐induced knockdown of LRF impaired remyelination during 3 or 6‐week recovery periods after cuprizone. LRF knockdown earlier within the oligodendrocyte lineage using NG2CreER^T:Zbtb7a^fl/fl mice reduced myelination after 6 weeks of cuprizone. LRF knockdown from either the Plp/CreER^T line or the NG2CreER^T line did not significantly change OP or oligodendrocyte populations. In vitro promoter assays demonstrated the potential for LRF to regulate transcription of myelin‐related genes and the notch target Hes5, which has been implicated in control of myelin formation and repair. In summary, in the oligodendrocyte lineage, LRF is expressed mainly in oligodendrocytes but is not required for oligodendrocyte repopulation of demyelinated lesions. Furthermore, LRF can modulate the extent of remyelination, potentially by contributing to interactions regulating transcription.

Comparing costs of illness of multiple sclerosis in three different years: A population-based study

BACKGROUND

Little is known about changes in the costs of illness (COI) among multiple sclerosis (MS) patients during recent years.

OBJECTIVES

To compare the COI among MS patients and matched controls in 2006, 2009, and 2012, respectively, indicating the costs attributable to the MS disease.

METHODS

Three cross-sectional datasets were analyzed, including all MS patients in Sweden aged 20-60 years and five matched controls for each of them. The analyses were based on 10,531 MS patients and 52,655 matched controls for 2006, 11,722 and 58,610 individuals for 2009, and 12,789 and 63,945 for 2012. Nationwide registers, including prescription drug use, specialized healthcare, sick leave, and disability pension, were linked to estimate the prevalence-based COI.

RESULTS

Adjusted for inflation, the average difference in COI between MS patients and matched controls were Swedish Krona (SEK) 243,751 (95% confidence interval: SEK 239,171-248,331) in 2006, SEK 238,971 (SEK 234,516-243,426) in 2009, and SEK 225,923 (SEK 221,630-230,218) in 2012. The difference in indirect costs were SEK 170,502 (SEK 166,478-174,525) in 2006, SEK 158,839 (SEK 154,953-162,726) in 2009, and SEK 141,280 (SEK 137,601-144,960) in 2012.

CONCLUSION

The inflation-adjusted COI of MS patients was lower in 2012 than in 2006, in particular regarding indirect costs.

Promoting in vivo remyelination with small molecules: a neuroreparative pharmacological treatment for Multiple Sclerosis

Multiple Sclerosis (MS) is a neurodegenerative disease where immune-driven demyelination occurs with inefficient remyelination, but therapies are limited, especially those to enhance repair. Here, we show that the dual phosphodiesterase (PDE)7- glycogen synthase kinase (GSK)3 inhibitor, VP3.15, a heterocyclic small molecule with good pharmacokinetic properties and safety profile, improves in vivo remyelination in mouse and increases both adult mouse and adult human oligodendrocyte progenitor cell (OPC) differentiation, in addition to its immune regulatory action. The dual inhibition is synergistic, as increasing intracellular levels of cAMP by cyclic nucleotide PDE inhibition both suppresses the immune response and increases remyelination, and in addition, inhibition of GSK3 limits experimental autoimmune encephalomyelitis in mice. This combination of an advantageous effect on the immune response and an enhancement of repair, plus demonstration of its activity on adult human OPCs, leads us to propose dual PDE7-GSK3 inhibition, and specifically VP3.15, as a neuroprotective and neuroreparative disease-modifying treatment for MS.

Direct magnitude and phase imaging of myelin using ultrashort echo time (UTE) pulse sequences: A feasibility study

In this paper, we aimed to investigate the feasibility of direct visualization of myelin, including myelin lipid and myelin basic protein (MBP), using two-dimensional ultrashort echo time (2D UTE) sequences and utilize phase information as a contrast mechanism in phantoms and in volunteers. The standard UTE sequence was used to detect both myelin and long T2 signal. An adiabatic inversion recovery UTE (IR-UTE) sequence was used to selectively detect myelin by suppressing signal from long T2 water protons. Magnitude and phase imaging and T2* were investigated on myelin lipid and MBP in the forms of lyophilized powders as well as paste-like phantoms with the powder mixed with D₂O, and rubber phantoms as well as healthy volunteers. Contrast to noise ratio (CNR) between white and gray matter was measured. Both magnitude and phase images were generated for myelin and rubber phantoms as well white matter in vivo using the IR-UTE sequence. T2* values of ~300μs were comparable for myelin paste phantoms and the short T2* component in white matter of the brain in vivo. Mean CNR between white and gray matter in IR-UTE imaging was increased from -7.3 for the magnitude images to 57.4 for the phase images. The preliminary results suggest that the IR-UTE sequence allows simultaneous magnitude and phase imaging of myelin in vitro and in vivo.

LINGO-1 Regulates Oligodendrocyte Differentiation through the Cytoplasmic Gelsolin Signaling Pathway

Differentiation and maturation of oligodendrocyte progenitor cells (OPCs) involve the assembly and disassembly of actin microfilaments. However, how actin dynamics are regulated during this process remains poorly understood. Leucine-rich repeat and Ig-like domain-containing Nogo receptor interacting protein 1 (LINGO-1) is a negative regulator of OPC differentiation. We discovered that anti-LINGO-1 antibody-promoted OPC differentiation was accompanied by upregulation of cytoplasmic gelsolin (cGSN), an abundant actin-severing protein involved in the depolymerization of actin filaments. Treating rat OPCs with cGSN siRNA reduced OPC differentiation, whereas overexpression of cGSN promoted OPC differentiation in vitro and remyelination in vivo Furthermore, coexpression of cGSN and LINGO-1 blocked the inhibitory effect of LINGO-1. Our study demonstrates that cGSN works downstream of LINGO-1 signaling pathway, which enhances actin dynamics and is essential for OPC morphogenesis and differentiation. This finding may lead to novel therapeutic approaches for the treatment of demyelinating diseases such as multiple sclerosis (MS).SIGNIFICANCE STATEMENT Myelin loss and subsequent axon degeneration contributes to a variety of neurological diseases, such as multiple sclerosis (MS). Understanding the regulation of myelination by oligodendrocytes is therefore critical for developing therapies for the treatment of MS. We previously demonstrated that leucine-rich repeat and Ig-like domain-containing Nogo receptor interacting protein 1 (LINGO-1) is a negative regulator of oligodendrocyte differentiation and that anti-LINGO-1 promotes remyelination in preclinical animal models for MS and in a phase II acute optic neuritis clinical trial (RENEW). The mechanism by which LINGO-1 regulates oligodendrocyte differentiation is unknown. Here, we demonstrate that LINGO-1 regulates oligodendrocyte differentiation and maturation through the cytoplasmic gelsolin signaling pathway, providing new drug targets for the treatment of demyelination diseases.

Taking Advantage of Nature's Gift: Can Endogenous Neural Stem Cells Improve Myelin Regeneration?

Irreversible functional deficits in multiple sclerosis (MS) are directly correlated to axonal damage and loss. Neurodegeneration results from immune-mediated destruction of myelin sheaths and subsequent axonal demyelination. Importantly, oligodendrocytes, the myelinating glial cells of the central nervous system, can be replaced to some extent to generate new myelin sheaths. This endogenous regeneration capacity has so far mainly been attributed to the activation and recruitment of resident oligodendroglial precursor cells. As this self-repair process is limited and increasingly fails while MS progresses, much interest has evolved regarding the development of remyelination-promoting strategies and the presence of alternative cell types, which can also contribute to the restoration of myelin sheaths. The adult brain comprises at least two neurogenic niches harboring life-long adult neural stem cells (NSCs). An increasing number of investigations are beginning to shed light on these cells under pathological conditions and revealed a significant potential of NSCs to contribute to myelin repair activities. In this review, these emerging investigations are discussed with respect to the importance of stimulating endogenous repair mechanisms from germinal sources. Moreover, we present key findings of NSC-derived oligodendroglial progeny, including a comprehensive overview of factors and mechanisms involved in this process.

Pharmacological approaches to intervention in hypomyelinating and demyelinating white matter pathology

White matter disease afflicts both developing and mature central nervous systems. Both cell intrinsic and extrinsic dysregulation result in profound changes in cell survival, axonal metabolism and functional performance. Experimental models of developmental white matter (WM) injury and demyelination have not only delineated mechanisms of signaling and inflammation, but have also paved the way for the discovery of pharmacological approaches to intervention. These reagents have been shown to enhance protection of the mature oligodendrocyte cell, accelerate progenitor cell recruitment and/or differentiation, or attenuate pathological stimuli arising from the inflammatory response to injury. Here we highlight reports of studies in the CNS in which compounds, namely peptides, hormones, and small molecule agonists/antagonists, have been used in experimental animal models of demyelination and neonatal brain injury that affect aspects of excitotoxicity, oligodendrocyte development and survival, and progenitor cell function, and which have been demonstrated to attenuate damage and improve WM protection in experimental models of injury. The molecular targets of these agents include growth factor and neurotransmitter receptors, morphogens and their signaling components, nuclear receptors, as well as the processes of iron transport and actin binding. By surveying the current evidence in non-immune targets of both the immature and mature WM, we aim to better understand pharmacological approaches modulating endogenous oligodendroglia that show potential for success in the contexts of developmental and adult WM pathology. This article is part of the Special Issue entitled 'Oligodendrocytes in Health and Disease'.