Remyelination therapies: a new direction and challenge in multiple sclerosis

Targeted DeSUMOylation as a therapeutic strategy for multiple sclerosis

SUMO (small ubiquitin like modifier) conjugated proteins have emerged as an important post translational modifier of cellular function. SUMOylation modulates several cellular processes involved in transcriptional regulation of genes, protein-protein interactions and DNA damage and repair. Since abnormalities in SUMOylation has been observed in neoplastic and neurodegenerative disorders, the SUMO pathway has become an attractive site for targeting of new therapies to regulate SUMOylation and reduce disease burden. Conjugation of SUMO to their respective substrates is orchestrated by an enzymatic cascade involving three main enzymes, E1, activation enzyme, E2, conjugating enzyme and E3, a protein ligase. Each of these enzymes are therefore potential "druggable" sites for future therapeutics. SUMOylation is a well-known mechanism by which the innate immune response is regulated in response to viral infections and in the adaptive immune response to tumor immunity. We have shown that small molecules which inhibit the SUMO activation pathway are also capable of inhibiting autoimmune response. TAK981 which forms adducts with SUMO and anacardic acid which inhibits the E1 enzyme of the SUMO pathway were effective in preventing the development of experimental allergic encephalitis (EAE), a mouse model of multiple sclerosis. Anacardic acid and TAK981 inhibited activation of TH17 cells and reduced clinical and pathological injury in IL-17 mediated myelin oligodendrocyte glycoprotein (MOG) induced EAE. Ginkgolic acid, another known inhibitor of SUMO pathway, was also shown to be effective in reducing the severity of inflammatory arthropathies which is also IL-17 mediated. In addition, the increase in the transcription of myelin genes with TAK981 and anacardic acid improved remyelination in experimental models of demyelination. In the present review paper, we examine the mechanism of action of inhibitors of the SUMO pathway on regulating the immune response and the possibility of the use of these agents as therapeutics for MS.

Neurological efficacy and safety of mesenchymal stem cells (MSCs) therapy in people with multiple sclerosis (pwMS): An updated systematic review and meta-analysis

BACKGROUND

Current therapeutic strategies for multiple sclerosis (MS) aim to suppress the immune response and reduce relapse rates. As alternative treatments, mesenchymal stem cells (MSCs) are being explored. MSCs show promise in repairing nerve tissue and reducing autoimmune responses in people with MS (pwMS).

OBJECTIVE

This review delves into the literature on the efficacy and safety of MSC therapy for pwMS.

METHODS

A comprehensive search strategy was employed to identify relevant articles from five databases until January 2024. The inclusion criteria encompassed interventional studies. Efficacy and safety data concerning MSC therapy in relapsing-remitting MS (RRMS), secondary progressive MS (SPMS), and primary progressive MS (PPMS) groups were extracted and analyzed.

RESULTS

A comprehensive analysis encompassing 30 studies revealed that individuals who underwent intrathecal (IT) protocol-based transplantation of MSCs experienced a noteworthy improvement in their expanded disability status scale (EDSS) compared to the placebo group. Weighted mean difference (WMD) was -0.28; 95 % CI -0.53 to -0.03, I2 = 0 %, p-value = 0.028); however, the intravenous (IV) group did not show significant changes in EDSS scores. The annualized relapse rate (ARR) did not significantly decrease among pwMS (WMD = -0.34; 95 % CI -1.05 to 0.38, I2 = 98 %, p-value = 0.357). Favorable results were observed in magnetic resonance imaging (MRI), with only 19.11 % of pwMS showing contrast-enhanced lesions (CEL) in the short term and no long-term MRI activity. The most common complications in both short-term and long-term follow-ups were infection, back pain, and gastrointestinal symptoms.

CONCLUSIONS

The study highlights the safety potential of MSC therapy for pwMS. While MRI-based neural regeneration shows significant treatment potential, the effectiveness of MSC therapy remains uncertain due to study limitations and ineffective outcome measures. Further research is needed to establish efficacy and optimize evaluation methods for MSC therapy on pwMS.

Black Seed Oil-Based Curcumin Nanoformulations Ameliorated Cuprizone-Induced Demyelination in the Mouse Hippocampus

Multiple sclerosis (MS) is a neurodegenerative disease characterized by the demyelination of nerves, axonal damage, and neuroinflammation. Cognition impairment, pain, and loss of mobility are some of the usual complications of MS. It has been postulated that the overproduction of proinflammatory cytokines and reactive oxygen species (ROS) are the main factors that contribute to MS pathology. Among various animal models, the cuprizone model is the most widely used model for investigating MS-related pathology. We assessed the effects of cuprizone along with the protective effects of some black seed oil-based nanoformulations of curcumin with and without piperine, in mice hippocampus in terms of the changes in antioxidant enzymes, transcription factors, and cytokines during demyelination and remyelination processes. The results of behavioral studies point toward impairment in working memory following the feeding of cuprizone for 5 weeks. However, in treatment groups, mice seemed to prevent the toxic effects of cuprizone. Nanoformulations used in this study were found to be highly effective in lowering the amount of ROS as indicated by the levels of antioxidant enzymes like catalase, superoxide dismutase, glutathione, and glutathione peroxidase. Moreover, nanoformulations CCF and CCPF were observed resisting the toxic effects of cuprizone. We observed greater expression of NFκB-p65 in the CPZ group than in the control group. CCF nanoformulation had a better inhibitory effect on NFκB-p65 than other formulations. Histological examination of the hippocampus was also conducted. Nanoformulations used here were found effective in reversing MS-related pathophysiology and hence have the potential to be applied as adjuvant therapy for MS treatment.

The Study of Remyelinating Therapies in Multiple Sclerosis: Visual Outcomes as a Window Into Repair

INTRODUCTION

Amelioration of disability in multiple sclerosis requires the development of complementary therapies that target neurodegeneration and promote repair. Remyelination is a promising neuroprotective strategy that may protect axons from damage and subsequent neurodegeneration.

METHODS

A review of key literature plus additional targeted search of PubMed and Google Scholar was conducted.

RESULTS

There has been a rapid expansion of clinical trials studying putative remyelinating candidates, but further growth of the field is limited by the lack of consensus on key aspects of trial design. We have not yet defined the ideal study population, duration of therapy, or the appropriate outcome measures to detect remyelination in humans. The varied natural history of multiple sclerosis, coupled with the short time frame of phase II clinical trials, requires that we develop and validate biomarkers of remyelination that can serve as surrogate endpoints in clinical trials.

CONCLUSIONS

We propose that the visual system may be the most well-suited and validated model for the study potential remyelinating agents. In this review, we discuss the pathophysiology of demyelination and summarize the current clinical trial landscape of remyelinating agents. We present some of the challenges in the study of remyelinating agents and discuss current potential biomarkers of remyelination and repair, emphasizing both established and emerging visual outcome measures.

ACKR3 Antagonism Enhances the Repair of Demyelinated Lesions Through Both Immunomodulatory and Remyelinating Effects

Addressing inflammation, demyelination, and associated neurodegeneration in inflammatory demyelinating diseases like multiple sclerosis (MS) remains challenging. ACT-1004-1239, a first-in-class and potent ACKR3 antagonist, currently undergoing clinical development, showed promise in preclinical MS models, reducing neuroinflammation and demyelination. However, its effectiveness in treating established disease and impact on remyelination after the occurrence of demyelinated lesions remain unexplored. This study assessed the therapeutic effect of ACT-1004-1239 in two demyelinating disease models. In the proteolipid protein (PLP)-induced experimental autoimmune encephalomyelitis (EAE) model, ACT-1004-1239 administered upon the detection of the first signs of paralysis, resulted in a dose-dependent reduction in EAE disease severity, concomitant with diminished immune cell infiltrates in the CNS and reduced demyelination. Notably, efficacy correlated with elevated plasma concentrations of CXCL11 and CXCL12, two pharmacodynamic biomarkers of ACKR3 antagonism. Combining ACT-1004-1239 with siponimod, an approved immunomodulatory treatment for MS, synergistically reduced EAE severity. In the cuprizone-induced demyelination model, ACT-1004-1239 administered after 5 weeks of cuprizone exposure, significantly accelerated remyelination, already quantifiable one week after cuprizone withdrawal. Additionally, ACT-1004-1239 penetrated the CNS, elevating brain CXCL12 concentrations. These results demonstrate that ACKR3 antagonism significantly reduces the severity of experimental demyelinating diseases, even when treatment is initiated therapeutically, after the occurrence of lesions. It confirms the dual mode of action of ACT-1004-1239, exhibiting both immunomodulatory effects by reducing neuroinflammation and promyelinating effects by accelerating myelin repair. The results further strengthen the rationale for evaluating ACT-1004-1239 in clinical trials for patients with demyelinating diseases.

3D inversion recovery ultrashort echo time MRI can detect demyelination in cuprizone-treated mice

Purpose

To test the ability of inversion-recovery ultrashort echo time (IR-UTE) MRI to directly detect demyelination in mice using a standard cuprizone mouse model.

Methods

Non-aqueous myelin protons have ultrashort T2s and are "invisible" with conventional MRI sequences but can be detected with UTE sequences. The IR-UTE sequence uses an adiabatic inversion-recovery preparation to suppress the long T2 water signal so that the remaining signal is from the ultrashort T2 myelin component. In this study, eight 8-week-old C57BL/6 mice were fed cuprizone (n = 4) or control chow (n = 4) for 5 weeks and then imaged by 3D IR-UTE MRI. The differences in IR-UTE signal were compared in the major white matter tracts in the brain and correlated with the Luxol Fast Blue histochemical marker of myelin.

Results

IR-UTE signal decreased in cuprizone-treated mice in white matter known to be sensitive to demyelination in this model, such as the corpus callosum, but not in white matter known to be resistant to demyelination, such as the internal capsule. These findings correlated with histochemical staining of myelin content.

Conclusions

3D IR-UTE MRI was sensitive to cuprizone-induced demyelination in the mouse brain, and is a promising noninvasive method for measuring brain myelin content.

Prolonged myelin deficits contribute to neuron loss and functional impairments after ischaemic stroke

Ischaemic stroke causes neuron loss and long-term functional deficits. Unfortunately, effective approaches to preserving neurons and promoting functional recovery remain unavailable. Oligodendrocytes, the myelinating cells in the CNS, are susceptible to oxygen and nutrition deprivation and undergo degeneration after ischaemic stroke. Technically, new oligodendrocytes and myelin can be generated by the differentiation of oligodendrocyte precursor cells (OPCs). However, myelin dynamics and their functional significance after ischaemic stroke remain poorly understood. Here, we report numerous denuded axons accompanied by decreased neuron density in sections from ischaemic stroke lesions in human brain, suggesting that neuron loss correlates with myelin deficits in these lesions. To investigate the longitudinal changes in myelin dynamics after stroke, we labelled and traced pre-existing and newly-formed myelin, respectively, using cell-specific genetic approaches. Our results indicated massive oligodendrocyte death and myelin loss 2 weeks after stroke in the transient middle cerebral artery occlusion (tMCAO) mouse model. In contrast, myelin regeneration remained insufficient 4 and 8 weeks post-stroke. Notably, neuronal loss and functional impairments worsened in aged brains, and new myelin generation was diminished. To analyse the causal relationship between remyelination and neuron survival, we manipulated myelinogenesis by conditional deletion of Olig2 (a positive regulator) or muscarinic receptor 1 (M1R, a negative regulator) in OPCs. Deleting Olig2 inhibited remyelination, reducing neuron survival and functional recovery after tMCAO. Conversely, enhancing remyelination by M1R conditional knockout or treatment with the pro-myelination drug clemastine after tMCAO preserved white matter integrity and neuronal survival, accelerating functional recovery. Together, our findings demonstrate that enhancing myelinogenesis is a promising strategy to preserve neurons and promote functional recovery after ischaemic stroke.

Interleukin-6 Inhibits Expression of miR-204-5p, a Regulator of Oligodendrocyte Differentiation: Involvement of miR-204-5p in the Prevention of Chemical-Induced Oligodendrocyte Impairment

Oligodendrocytes (OLs) form myelin sheaths around axons in the central nervous system (CNS) facilitate the propagation of action potentials. The studies have shown that the differentiation and maturation of OLs involve microRNA (miR) regulation. The recent findings have addressed that miR-204 regulates OL differentiation in culture. In this study, through in situ hybridization in combination with immunohistochemistry, we showed that microRNA-204-5p in the corpus callosum was mainly expressed in OLs immunoreactive with adenomatous polyposis coli (APC), an OL marker. We also found miR-204-5p expression in mature OLs was suppressed by the addition of interleukin-6 (IL-6). Moreover, IL-6-induced inhibition of miR-204-5p expression was blocked by the addition of the inhibitors specific for p38 mitogen-activated protein kinase (p38MAPK) or phosphatidylinositol 3-kinase (PI3K) pathway. We further utilized a rat model by feeding cuprizone (CPZ)-containing diet for 3 weeks to induce demyelination and gliosis in the corpus callosum, as well as the upregulation of IL-6 gene expression significantly. Despite that miR-204-5p expression in the corpus callosum was not altered after feeding by CPZ for 3 weeks, its expression was increased and IL-6 transcription was decreased in the corpus callosum of the recovery group that was fed by CPZ for the first 2 weeks and by the regular diet for one more week. Our data demonstrate that miR-204-5p expression in OLs declined under the influence of the inflamed microenvironment. The findings that an increase in miR-204-5p and declined IL-6 expression observed in the recovery group might be involved with OL repair in the corpus callosum, and also shed light on a potential role for miR-204-5p in OL homeostasis following the white matter injury.

Anti- and pro-inflammatory milieu differentially regulate differentiation and immune functions of oligodendrocyte progenitor cells

Oligodendrocyte progenitor cells (OPCs) were regarded for years solely for their regenerative role; however, their immune-modulatory roles have gained much attention recently, particularly in the context of multiple sclerosis (MS). Despite extensive studies on OPCs, there are limited data elucidating the interactions between their intrinsic regenerative and immune functions, as well as their relationship with the inflamed central nervous system (CNS) environment, a key factor in MS pathology. We examined the effects of pro-inflammatory cytokines, represented by interferon (IFN)-γ and tumour necrosis factor (TNF)-α, as well as anti-inflammatory cytokines, represented by interleukin (IL)-4 and IL-10, on OPC differentiation and immune characteristics. Using primary cultures, enzyme-linked immunosorbent assay and immunofluorescence stainings, we assessed differentiation capacity, phagocytic activity, major histocompatibility complex (MHC)-II expression, and cytokine secretion. We observed that the anti-inflammatory milieu (IL4 and IL10) reduced both OPC differentiation and immune functions. Conversely, exposure to TNF-α led to intact differentiation, increased phagocytic activity, high levels of MHC-II expression, and cytokines secretion. Those effects were attributed to signalling via TNF-receptor-2 and counteracted the detrimental effects of IFN-γ on OPC differentiation. Our findings suggest that a pro-regenerative, permissive inflammatory environment is needed for OPCs to execute both regenerative and immune-modulatory functions.

High Levels of Perivascular Inflammation and Active Demyelinating Lesions at Time of Death Associated with Rapidly Progressive Multiple Sclerosis Disease Course: A Retrospective Postmortem Cohort Study

OBJECTIVE

Analysis of postmortem multiple sclerosis (MS) tissues combined with in vivo disease milestones suggests that whereas perivascular white matter infiltrates are associated with demyelinating activity in the initial stages, leptomeningeal immune cell infiltration, enriched in B cells, and associated cortical lesions contribute to disease progression. We systematically examine the association of inflammatory features and white matter demyelination at postmortem with clinical milestones.

METHODS

In 269 MS brains, 20 sites were examined using immunohistochemistry for active lesions (ALs) and perivenular inflammation (PVI). In a subset of 22, a detailed count of CD20+ B cells and CD3+ T cells in PVIs was performed.

RESULTS

ALs were detected in 22%, whereas high levels of PVI were detected in 52% of cases. ALs were present in 35% of cases with high levels of PVI. Shorter time from onset of progression to death was associated with increased prevalence and higher levels of PVI (both p < 0.0001). Shorter time from onset of progression to wheelchair use was associated with higher prevalence of ALs (odds ratio [OR] = 0.921, 95% confidence interval [CI] = 0.858-0.989, p = 0.0230) and higher level of PVI (OR = 0.932, 95% CI = 0.886-0.981, p = 0.0071). High levels of PVI were associated with meningeal inflammation and increased cortical demyelination and significantly higher levels of B lymphocytes within the PVI.

INTERPRETATION

ALs, a feature of early disease stage, persist up to death in a subgroup with high levels of PVI. These features link to a rapid progressive phase and higher levels of meningeal inflammation and B-cell infiltrates, supporting the hypothesis that chronic inflammation drives progression in MS. ANN NEUROL 2024;95:706-719.

Unravelling the Road to Recovery: Mechanisms of Wnt Signalling in Spinal Cord Injury

Spinal cord injury (SCI) is a complex neurodegenerative pathology that consistently harbours a poor prognostic outcome. At present, there are few therapeutic strategies that can halt neuronal cell death and facilitate functional motor recovery. However, recent studies have highlighted the Wnt pathway as a key promoter of axon regeneration following central nervous system (CNS) injuries. Emerging evidence also suggests that the temporal dysregulation of Wnt may drive cell death post-SCI. A major challenge in SCI treatment resides in developing therapeutics that can effectively target inflammation and facilitate glial scar repair. Before Wnt signalling is exploited for SCI therapy, further research is needed to clarify the implications of Wnt on neuroinflammation during chronic stages of injury. In this review, an attempt is made to dissect the impact of canonical and non-canonical Wnt pathways in relation to individual aspects of glial and fibrotic scar formation. Furthermore, it is also highlighted how modulating Wnt activity at chronic time points may aid in limiting lesion expansion and promoting axonal repair.

Validating a minipig model of reversible cerebral demyelination using human diagnostic modalities and electron microscopy

BACKGROUND

Inflammatory demyelinating diseases of the central nervous system, such as multiple sclerosis, are significant sources of morbidity in young adults despite therapeutic advances. Current murine models of remyelination have limited applicability due to the low white matter content of their brains, which restricts the spatial resolution of diagnostic imaging. Large animal models might be more suitable but pose significant technological, ethical and logistical challenges.

METHODS

We induced targeted cerebral demyelinating lesions by serially repeated injections of lysophosphatidylcholine in the minipig brain. Lesions were amenable to follow-up using the same clinical imaging modalities (3T magnetic resonance imaging, 11C-PIB positron emission tomography) and standard histopathology protocols as for human diagnostics (myelin, glia and neuronal cell markers), as well as electron microscopy (EM), to compare against biopsy data from two patients.

FINDINGS

We demonstrate controlled, clinically unapparent, reversible and multimodally trackable brain white matter demyelination in a large animal model. De-/remyelination dynamics were slower than reported for rodent models and paralleled by a degree of secondary axonal pathology. Regression modelling of ultrastructural parameters (g-ratio, axon thickness) predicted EM features of cerebral de- and remyelination in human data.

INTERPRETATION

We validated our minipig model of demyelinating brain diseases by employing human diagnostic tools and comparing it with biopsy data from patients with cerebral demyelination.

FUNDING

This work was supported by the DFG under Germany's Excellence Strategy within the framework of the Munich Cluster for Systems Neurology (EXC 2145 SyNergy, ID 390857198) and TRR 274/1 2020, 408885537 (projects B03 and Z01).

Interplay between androgen and CXCR4 chemokine signaling in myelin repair

In men, reduced levels of testosterone are associated with the prevalence and progression of multiple sclerosis (MS), a chronic and disabling demyelinating disorder. Testosterone has been shown to promote myelin repair. Here, we demonstrate that the cooperation between testosterone and CXCR4 signaling involving astrocytes is required for myelin regeneration after focal demyelination produced in the ventral mouse spinal cord by the infusion of lysolecithin. The testosterone-dependent remyelination of axons by oligodendrocytes was accompanied by an increase in astrocytes expressing CXCR4, its ligand CXCL12 and the androgen receptor (AR) within the demyelinated area. Depriving males of their testosterone or pharmacological inhibition of CXCR4, with the selective antagonist AMD3100, prevented the appearance of astrocytes expressing CXCR4, CXCL12 and AR within the demyelinated area and the concomitant recruitment of myelin forming oligodendrocytes. Conditional genetic ablation of either CXCR4 or AR in astrocytes also completely blocked the formation of new myelin by oligodendrocytes. Interestingly, the gain of function mutation in CXCR4 causing WHIM syndrome allows remyelination to take place, even in the absence of testosterone, but its potentiating effects remained observable. After testosterone deprivation or CXCR4 inhibition, the absence of astrocytes within the demyelinated area led to the incursion of Schwann cells, most likely derived from spinal nerves, and the formation of peripheral nerve type myelin. In patients with progressive MS, astrocytes expressing CXCR4 and AR surrounded myelin lesions, and their presence opposed the incursion of Schwann cells. These results highlight a mechanism of promyelinating testosterone signaling and the importance of normalizing its levels in combined myelin repair therapies.

Mitochondrial and metabolic dysfunction of peripheral immune cells in multiple sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disorder characterized by the infiltration of inflammatory cells and demyelination of nerves. Mitochondrial dysfunction has been implicated in the pathogenesis of MS, as studies have shown abnormalities in mitochondrial activities, metabolism, mitochondrial DNA (mtDNA) levels, and mitochondrial morphology in immune cells of individuals with MS. The presence of mitochondrial dysfunctions in immune cells contributes to immunological dysregulation and neurodegeneration in MS. This review provided a comprehensive overview of mitochondrial dysfunction in immune cells associated with MS, focusing on the potential consequences of mitochondrial metabolic reprogramming on immune function. Current challenges and future directions in the field of immune-metabolic MS and its potential as a therapeutic target were also discussed.

Microglia promote remyelination independent of their role in clearing myelin debris

Multiple sclerosis (MS) is an inflammatory disease characterized by myelin loss. While therapies exist to slow MS progression, no treatment currently exists for remyelination. Remyelination, linked to reduced disability in MS, relies on microglia and monocyte-derived macrophages (MDMs). This study aims to understand the role of microglia during remyelination by lineage tracing and depleting them. Microglial lineage tracing reveals that both microglia and MDMs initially accumulate, but microglia later dominate the lesion. Microglia and MDMs engulf equal amounts of inhibitory myelin debris, but after microglial depletion, MDMs compensate by engulfing more myelin debris. Microglial depletion does, however, reduce the recruitment and proliferation of oligodendrocyte progenitor cells (OPCs) and impairs their subsequent differentiation and remyelination. These findings underscore the essential role of microglia during remyelination and offer insights for enhancing this process by understanding microglial regulation of remyelination.

Neuroglial components of brain lesions may provide new therapeutic strategies for multiple sclerosis

Multiple sclerosis (MS) is a chronic autoimmune and demyelinating disease of the central nervous system (CNS) which leads to focal demyelinated lesions in the brain and spinal cord. Failure of remyelination contributes to chronic disability in young adults. Characterization of events occurring during the demyelination and remyelination processes and those of which subsequently limit remyelination or contribute to demyelination can provide the possibility of new therapies development for MS. Most of the currently available therapies and investigations modulate immune responses and mediators. Since most therapeutic strategies have unsatisfied outcomes, developing new therapies that enhance brain lesion repair is a priority. A close look at cellular and chemical components of MS lesions will pave the way to a better understanding of lesions pathology and will provide possible opportunities for repair strategies and targeted pharmacotherapy. This review summarizes the lesion components and features, particularly the detrimental elements, and discusses the possibility of suggesting new potential targets as therapies for demyelinating diseases like MS.

Therapeutic Plasma Exchange and Multiple Sclerosis Dysregulations: Focus on the Removal of Pathogenic Circulatory Factors and Altering Nerve Growth Factor and Sphingosine-1-Phosphate Plasma Levels

Multiple sclerosis (MS) is predominantly an immune-mediated disease of the central nervous system (CNS) of unknown etiology with a possible genetic predisposition and effect of certain environmental factors. It is generally accepted that the disease begins with an autoimmune inflammatory reaction targeting oligodendrocytes followed by a rapid depletion of their regenerative capacity with subsequent permanent neurodegenerative changes and disability. Recent research highlights the central role of B lymphocytes and the corresponding IgG and IgM autoantibodies in newly forming MS lesions. Thus, their removal along with the modulation of certain bioactive molecules to improve neuroprotection using therapeutic plasma exchange (TPE) becomes of utmost importance. Recently, it has been proposed to determine the levels and precise effects of both beneficial and harmful components in the serum of MS patients undergoing TPE to serve as markers for appropriate TPE protocols. In this review we discuss some relevant examples, focusing on the removal of pathogenic circulating factors and altering the plasma levels of nerve growth factor and sphingosine-1-phosphate by TPE. Altered plasma levels of the reviewed molecular compounds in response to TPE reflect a successful reduction of the pro-inflammatory burden at the expense of an increase in anti-inflammatory potential in the circulatory and CNS compartments.

Repurposing Clemastine to Target Glioblastoma Cell Stemness

Brain tumor-initiating cells (BTICs) and tumor cell plasticity promote glioblastoma (GBM) progression. Here, we demonstrate that clemastine, an over-the-counter drug for treating hay fever and allergy symptoms, effectively attenuated the stemness and suppressed the propagation of primary BTIC cultures bearing PDGFRA amplification. These effects on BTICs were accompanied by altered gene expression profiling indicative of their more differentiated states, resonating with the activity of clemastine in promoting the differentiation of normal oligodendrocyte progenitor cells (OPCs) into mature oligodendrocytes. Functional assays for pharmacological targets of clemastine revealed that the Emopamil Binding Protein (EBP), an enzyme in the cholesterol biosynthesis pathway, is essential for BTIC propagation and a target that mediates the suppressive effects of clemastine. Finally, we showed that a neural stem cell-derived mouse glioma model displaying predominantly proneural features was similarly susceptible to clemastine treatment. Collectively, these results identify pathways essential for maintaining the stemness and progenitor features of GBMs, uncover BTIC dependency on EBP, and suggest that non-oncology, low-toxicity drugs with OPC differentiation-promoting activity can be repurposed to target GBM stemness and aid in their treatment.

Alterations of Oligodendrocyte and Myelin Energy Metabolism in Multiple Sclerosis

Multiple sclerosis (MS) is a complex autoimmune disease of the central nervous system (CNS), characterized by demyelination and neurodegeneration. Oligodendrocytes play a vital role in maintaining the integrity of myelin, the protective sheath around nerve fibres essential for efficient signal transmission. However, in MS, oligodendrocytes become dysfunctional, leading to myelin damage and axonal degeneration. Emerging evidence suggests that metabolic changes, including mitochondrial dysfunction and alterations in glucose and lipid metabolism, contribute significantly to the pathogenesis of MS. Mitochondrial dysfunction is observed in both immune cells and oligodendrocytes within the CNS of MS patients. Impaired mitochondrial function leads to energy deficits, affecting crucial processes such as impulse transmission and axonal transport, ultimately contributing to neurodegeneration. Moreover, mitochondrial dysfunction is linked to the generation of reactive oxygen species (ROS), exacerbating myelin damage and inflammation. Altered glucose metabolism affects the energy supply required for oligodendrocyte function and myelin synthesis. Dysregulated lipid metabolism results in changes to the composition of myelin, affecting its stability and integrity. Importantly, low levels of polyunsaturated fatty acids in MS are associated with upregulated lipid metabolism and enhanced glucose catabolism. Understanding the intricate relationship between these mechanisms is crucial for developing targeted therapies to preserve myelin and promote neurological recovery in individuals with MS. Addressing these metabolic aspects may offer new insights into potential therapeutic strategies to halt disease progression and improve the quality of life for MS patients.

Promyelinating drugs promote functional recovery in an autism spectrum disorder mouse model of Pitt-Hopkins syndrome

Pitt-Hopkins syndrome is an autism spectrum disorder caused by autosomal dominant mutations in the human transcription factor 4 gene (TCF4). One pathobiological process caused by murine Tcf4 mutation is a cell autonomous reduction in oligodendrocytes and myelination. In this study, we show that the promyelinating compounds, clemastine, sobetirome and Sob-AM2 are effective at restoring myelination defects in a Pitt-Hopkins syndrome mouse model. In vitro, clemastine treatment reduced excess oligodendrocyte precursor cells and normalized oligodendrocyte density. In vivo, 2-week intraperitoneal administration of clemastine also normalized oligodendrocyte precursor cell and oligodendrocyte density in the cortex of Tcf4 mutant mice and appeared to increase the number of axons undergoing myelination, as EM imaging of the corpus callosum showed a significant increase in the proportion of uncompacted myelin and an overall reduction in the g-ratio. Importantly, this treatment paradigm resulted in functional rescue by improving electrophysiology and behaviour. To confirm behavioural rescue was achieved via enhancing myelination, we show that treatment with the thyroid hormone receptor agonist sobetirome or its brain penetrating prodrug Sob-AM2, was also effective at normalizing oligodendrocyte precursor cell and oligodendrocyte densities and behaviour in the Pitt-Hopkins syndrome mouse model. Together, these results provide preclinical evidence that promyelinating therapies may be beneficial in Pitt-Hopkins syndrome and potentially other neurodevelopmental disorders characterized by dysmyelination.

Remyelination by surviving oligodendrocytes is inefficient in the inflamed mammalian cortex

In multiple sclerosis, an inflammatory attack results in myelin loss, which can be partially reversed by remyelination. Recent studies suggest that mature oligodendrocytes could contribute to remyelination by generating new myelin. Here, we show that in a mouse model of cortical multiple sclerosis pathology, surviving oligodendrocytes can indeed extend new proximal processes but rarely generate new myelin internodes. Furthermore, drugs that boost myelin recovery by targeting oligodendrocyte precursor cells did not enhance this alternate mode of myelin regeneration. These data indicate that the contribution of surviving oligodendrocytes to myelin recovery in the inflamed mammalian CNS is minor and inhibited by distinct remyelination brakes.

Schwann Cell Remyelination in the Multiple Sclerosis Central Nervous System

Multiple sclerosis (MS) is a central nervous system (CNS) demyelinating disease. Failure to remyelinate successfully is common in MS lesions, often with consequent neuronal/axonal damage. CNS myelin is normally produced by oligodendroglial cells. Remyelination by Schwann cells (SchC) has been reported in spinal cord demyelination, in which SchCs are in close proximity to CNS myelin. We identified an MS cerebral lesion that was remyelinated by SchCs. This prompted us to query the extent of SchC remyelination in the brain and spinal cords of additional autopsied MS specimens. CNS tissues were obtained from the autopsies of 14 MS cases. Remyelinated lesions were identified by Luxol fast blue-periodic-acid Schiff and solochrome cyanine staining. Deparaffinized sections containing remyelinated lesions were stained with anti-glial fibrillary acid protein to identify reactive astrocytes. Glycoprotein P zero (P0) is a protein exclusive to peripheral but not CNS myelin. Areas of SchC remyelination were identified by staining with anti-P0. Myelinated regions in the index case cerebral lesion were confirmed to be of SchC origin using anti-P0 staining. Subsequently, 64 MS lesions from 14 autopsied MS cases were examined, and 23 lesions in 6 cases showed remyelination by SchCs. Lesions from the cerebrum, brainstem, and spinal cord were examined in each case. When present, SchC remyelination was most commonly located adjacent to the venules and associated with a lower surrounding density of glial fibrillary acid protein+ reactive astrocytes than areas of only oligodendroglial cell remyelination. The difference was significant only for spinal cord and brainstem lesions but not for lesions located in the brain. In conclusion, we demonstrated SchC remyelination in the cerebrum, brainstem, and spinal cord of 6 autopsied MS cases. To our knowledge, this is the first report of supratentorial SchC remyelination in MS.

Nervonic acid and its sphingolipids: Biological functions and potential food applications

Nervonic acid, a 24-carbon fatty acid with only one double bond at the 9th carbon (C24:1n-9), is abundant in the human brain, liver, and kidney. It not only functions in free form but also serves as a critical component of sphingolipids which participate in many biological processes such as cell membrane formation, apoptosis, and neurotransmission. Recent studies show that nervonic acid supplementation is not only beneficial to human health but also can improve the many medical conditions such as neurological diseases, cancers, diabetes, obesity, and their complications. Nervonic acid and its sphingomyelins serve as a special material for myelination in infants and remyelination patients with multiple sclerosis. Besides, the administration of nervonic acid is reported to reduce motor disorder in mice with Parkinson's disease and limit weight gain. Perturbations of nervonic acid and its sphingolipids might lead to the pathogenesis of many diseases and understanding these mechanisms is critical for investigating potential therapeutic approaches for such diseases. However, available studies about this aspect are limited. In this review, relevant findings about functional mechanisms of nervonic acid have been comprehensively and systematically described, focusing on four interconnected functions: cellular structure, signaling, anti-inflammation, lipid mobilization, and their related diseases.

Signaling mechanisms involved in the regulation of remyelination in multiple sclerosis: a mini review

Multiple sclerosis is an autoimmune neurodegenerative disease of the CNS that causes progressive disabilities, owing to CNS axon degeneration as a late result of demyelination. In the search for the prevention of axonal loss, mitigating inflammatory attacks in the CNS and myelin restoration are two possible approaches. As a result, therapies that target diverse signaling pathways involved in neuroprotection and remyelination have the potential to overcome the challenges in the development of multiple sclerosis treatments. LINGO1 (Leucine rich repeat and Immunoglobulin domain containing, Nogo receptor- interaction protein), AKT/PIP3/mTOR, Notch, Wnt, RXR (Retinoid X receptor gamma), and Nrf2 (nuclear factor erythroid 2-related factor 2) signaling pathways are highlighted in this section. This article reviews the present knowledge regarding numerous signaling pathways and their functions in regulating remyelination in multiple sclerosis pathogenesis. These pathways are potential biomarkers and therapeutic targets in MS.

Nogo-A and LINGO-1: Two Important Targets for Remyelination and Regeneration

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS) that causes progressive neurological disability in most patients due to neurodegeneration. Activated immune cells infiltrate the CNS, triggering an inflammatory cascade that leads to demyelination and axonal injury. Non-inflammatory mechanisms are also involved in axonal degeneration, although they are not fully elucidated yet. Current therapies focus on immunosuppression; however, no therapies to promote regeneration, myelin repair, or maintenance are currently available. Two different negative regulators of myelination have been proposed as promising targets to induce remyelination and regeneration, namely the Nogo-A and LINGO-1 proteins. Although Nogo-A was first discovered as a potent neurite outgrowth inhibitor in the CNS, it has emerged as a multifunctional protein. It is involved in numerous developmental processes and is necessary for shaping and later maintaining CNS structure and functionality. However, the growth-restricting properties of Nogo-A have negative effects on CNS injury or disease. LINGO-1 is also an inhibitor of neurite outgrowth, axonal regeneration, oligodendrocyte differentiation, and myelin production. Inhibiting the actions of Nogo-A or LINGO-1 promotes remyelination both in vitro and in vivo, while Nogo-A or LINGO-1 antagonists have been suggested as promising therapeutic approaches for demyelinating diseases. In this review, we focus on these two negative regulators of myelination while also providing an overview of the available data on the effects of Nogo-A and LINGO-1 inhibition on oligodendrocyte differentiation and remyelination.

Regulatory T cells alleviate myelin loss and cognitive dysfunction by regulating neuroinflammation and microglial pyroptosis via TLR4/MyD88/NF-κB pathway in LPC-induced demyelination

Demyelination occurs in multiple central nervous system (CNS) disorders and is tightly associated with neuroinflammation. Pyroptosis is a form of pro-inflammatory and lytic cell death which has been observed in CNS diseases recently. Regulatory T cells (Tregs) have exhibited immunoregulatory and protective effects in CNS diseases. However, the roles of Tregs in pyroptosis and their involvement in LPC-induced demyelination have not been explicated. In our study, Foxp3-diphtheria toxin receptor (DTR) mice treated with diphtheria toxin (DT) or PBS were subjected to two-site lysophosphatidylcholine (LPC) injection. Immunofluorescence, western blot, Luxol fast blue (LFB) staining, quantitative real-time PCR (qRT-PCR) and neurobehavior assessments were performed to evaluate the severity of demyelination, neuroinflammation and pyroptosis. Pyroptosis inhibitor was further used to investigate the role of pyroptosis in LPC-induced demyelination. RNA-sequencing was applied to explore the potential regulatory mechanism underlying the involvement of Tregs in LPC-induced demyelination and pyroptosis. Our results showed that depletion of Tregs aggravated microgliosis, inflammatory responses, immune cells infiltration and led to exacerbated myelin injury as well as cognitive defects in LPC-induced demyelination. Microglial pyroptosis was observed after LPC-induced demyelination, which was aggravated by Tregs depletion. Inhibition of pyroptosis by VX765 reversed myelin injury and cognitive function exacerbated by Tregs depletion. RNA-sequencing showed TLR4/myeloid differentiation marker 88 (MyD88) as the central molecules in Tregs-pyroptosis pathway, and refraining TLR4/MyD88/NF-κB pathway alleviated the aggravated pyroptosis induced by Tregs depletion. In conclusion, our findings for the first time indicate that Tregs alleviate myelin loss and improve cognitive function by inhibiting pyroptosis in microglia via TLR4/MyD88/NF-κB pathway in LPC-induced demyelination.

Noncancerous disease-targeting AIEgens

Noncancerous diseases include a wide plethora of medical conditions beyond cancer and are a major cause of mortality around the world. Despite progresses in clinical research, many puzzles about these diseases remain unanswered, and new therapies are continuously being sought. The evolution of bio-nanomedicine has enabled huge advancements in biosensing, diagnosis, bioimaging, and therapeutics. The recent development of aggregation-induced emission luminogens (AIEgens) has provided an impetus to the field of molecular bionanomaterials. Following aggregation, AIEgens show strong emission, overcoming the problems associated with the aggregation-caused quenching (ACQ) effect. They also have other unique properties, including low background interferences, high signal-to-noise ratios, photostability, and excellent biocompatibility, along with activatable aggregation-enhanced theranostic effects, which help them achieve excellent therapeutic effects as an one-for-all multimodal theranostic platform. This review provides a comprehensive overview of the overall progresses in AIEgen-based nanoplatforms for the detection, diagnosis, bioimaging, and bioimaging-guided treatment of noncancerous diseases. In addition, it details future perspectives and the potential clinical applications of these AIEgens in noncancerous diseases are also proposed. This review hopes to motivate further interest in this topic and promote ideation for the further exploration of more advanced AIEgens in a broad range of biomedical and clinical applications in patients with noncancerous diseases.

Therapeutic effect of combination vitamin D3 and siponimod on remyelination and modulate microglia activation in cuprizone mouse model of multiple sclerosis

Stimulation of remyelination is critical for the treatment of multiple sclerosis (MS) to alleviate symptoms and protect the myelin sheath from further damage. The current study aimed to investigate the possible therapeutic effects of combining vitamin D3 (Vit D3) and siponimod (Sipo) on enhancing remyelination and modulating microglia phenotypes in the cuprizone (CPZ) demyelination mouse model. The study was divided into two stages; demyelination (first 5 weeks) and remyelination (last 4 weeks). In the first 5 weeks, 85 mice were randomly divided into two groups, control (n = 20, standard rodent chow) and CPZ (n = 65, 0.3% CPZ mixed with chow for 6 weeks, followed by 3 weeks of standard rodent chow). At week 5, the CPZ group was re-divided into four groups (n = 14) for remyelination stages; untreated CPZ (0.2 ml of CMC orally), CPZ+Vit D3 (800 IU/kg Vit D3 orally), CPZ+Sipo (1.5 mg/kg Sipo orally), and CPZ+Vit D3 (800 IU/kg Vit D3) + Sipo (1.5 mg/kg Sipo orally). Various behavioral tasks were performed to evaluate motor performance. Luxol Fast Blue (LFB) staining, the expression level of myelin basic protein (MBP), and M1/M2 microglia phenotype genes were assessed in the corpus callosum (CC). The results showed that the combination of Vit D3 and Sipo improved behavioral deficits, significantly promoted remyelination, and modulated expression levels of microglia phenotype genes in the CC at early and late remyelination stages. These results demonstrate for the first time that a combination of Vit D3 and Sipo can improve the remyelination process in the cuprizone (CPZ) mouse model by attenuating the M1 microglia phenotype. This may help to improve the treatment of MS patients.

Glial aging and its impact on central nervous system myelin regeneration

Aging is a major risk factor for several neurodegenerative diseases and is associated with cognitive decline. In addition to affecting neuronal function, the aging process significantly affects the functional phenotype of the glial cell compartment, comprising oligodendrocyte lineage cells, astrocytes, and microglia. These changes result in a more inflammatory microenvironment, resulting in a condition that is favorable for neuron and synapse loss. In addition to facilitating neurodegeneration, the aging glial cell population has negative implications for central nervous system remyelination, a regenerative process that is of particular importance to the chronic demyelinating disease multiple sclerosis. This review will discuss the changes that occur with aging in the three main glial populations and provide an overview of the studies documenting the impact these changes have on remyelination.

Graph theoretical approach to brain remodeling in multiple sclerosis

Multiple sclerosis (MS) is a neuroinflammatory disorder damaging structural connectivity. Natural remodeling processes of the nervous system can, to some extent, restore the damage caused. However, there is a lack of biomarkers to evaluate remodeling in MS. Our objective is to evaluate graph theory metrics (especially modularity) as a biomarker of remodeling and cognition in MS. We recruited 60 relapsing-remitting MS and 26 healthy controls. Structural and diffusion MRI, plus cognitive and disability evaluations, were done. We calculated modularity and global efficiency from the tractography-derived connectivity matrices. Association of graph metrics with T2 lesion load, cognition, and disability was evaluated using general linear models adjusting for age, gender, and disease duration wherever applicable. We showed that MS subjects had higher modularity and lower global efficiency compared with controls. In the MS group, modularity was inversely associated with cognitive performance but positively associated with T2 lesion load. Our results indicate that modularity increase is due to the disruption of intermodular connections in MS because of the lesions, with no improvement or preserving of cognitive functions.

Depletion of regulatory T cells exacerbates inflammatory responses after chronic cerebral hypoperfusion in mice

Vascular cognitive impairment is the second most common cause of dementia which can be induced by chronic cerebral hypoperfusion. Regulatory T cells (Tregs) have been proven to provide beneficial effects in several central nervous system (CNS) diseases, but the roles of Tregs in chronic cerebral hypoperfusion-induced white matter damage have not been explored. In this study, Foxp3-diphtheria toxin receptor (DTR) mice treated with diphtheria toxin (DT) and wild type C57BL/6 mice treated with anti-CD25 antibody were subjected to bilateral carotid artery stenosis (BCAS). Flow cytometry analysis showed Tregs were widely distributed in spleen whereas barely distributed in brain under normal conditions. The distribution of lymphocytes and Tregs did not change significantly in spleen and brain after BCAS. Depletion of Tregs decreased the numbers of mature oligodendrocytes and anti-inflammatory microglia at 14 days and 28 days following BCAS. And pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6) and interferon-γ (IFN-γ) showed higher expression after Tregs depletion. In contrast, Tregs depletion did not change the overall severity of white matter injury as shown by the expression of myelin-associated glycoprotein (MAG), myelin basic protein (MBP), luxol fast blue (LFB) staining and electron microscopy assay. Moreover, Tregs depletion had marginal effect on cognition defects after BCAS revealed by Morris water maze and novel object recognition examination at 28 days after BCAS. In summary, our results suggest an anti-inflammatory role of Tregs with marginal effects on white matter damage in mice after BCAS-induced chronic cerebral hypoperfusion.

Chronic oligodendrocyte injury in central nervous system pathologies

Myelin, the membrane surrounding neuronal axons, is critical for central nervous system (CNS) function. Injury to myelin-forming oligodendrocytes (OL) in chronic neurological diseases (e.g. multiple sclerosis) ranges from sublethal to lethal, leading to OL dysfunction and myelin pathology, and consequent deleterious impacts on axonal health that drive clinical impairments. This is regulated by intrinsic factors such as heterogeneity and age, and extrinsic cellular and molecular interactions. Here, we discuss the responses of OLs to injury, and perspectives for therapeutic targeting. We put forward that targeting mature OL health in neurological disease is a promising therapeutic strategy to support CNS function.

Animal models to investigate the effects of inflammation on remyelination in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory, demyelinating, and neurodegenerative disease of the central nervous system (CNS). In people with MS, impaired remyelination and axonal loss lead to debilitating long-term neurologic deficits. Current MS disease-modifying drugs mainly target peripheral immune cells and have demonstrated little efficacy for neuroprotection or promoting repair. To elucidate the pathological mechanisms and test therapeutic interventions, multiple animal models have been developed to recapitulate specific aspects of MS pathology, particularly the acute inflammatory stage. However, there are few animal models that facilitate the study of remyelination in the presence of inflammation, and none fully replicate the biology of chronic demyelination in MS. In this review, we describe the animal models that have provided insight into the mechanisms underlying demyelination, myelin repair, and potential therapeutic targets for remyelination. We highlight the limitations of studying remyelination in toxin-based demyelination models and discuss the combinatorial models that recapitulate the inflammatory microenvironment, which is now recognized to be a major inhibitor of remyelination mechanisms. These models may be useful in identifying novel therapeutics that promote CNS remyelination in inflammatory diseases such as MS.

Promoting remyelination: A case study in regenerative medicine

Therapeutics that modulate regenerative mechanisms by targeting the activity of endogenous (adult) stem cell populations have the potential to revolutionize medicine. In many human disease states, capacity to repair damaged tissue underlies progressive decline and disease progression. Recent insights derived from efforts aimed at promoting remyelination for the treatment of multiple sclerosis (MS) highlight the importance of considering the limiting factors and underlying mechanisms associated with all aspects of disease onset, progression and recovery, during both the discovery and clinical stages of developing a regenerative medicine. This perspective presents general considerations for the development of regenerative therapies, using remyelination as a case study.

Enhancers of Human and Rodent Oligodendrocyte Formation Predominantly Induce Cholesterol Precursor Accumulation

Regeneration of myelin in the central nervous system is being pursued as a potential therapeutic approach for multiple sclerosis. Several labs have reported small molecules that promote oligodendrocyte formation and remyelination in vivo. Recently, we reported that many such molecules function by inhibiting a narrow window of enzymes in the cholesterol biosynthesis pathway. Here we describe a new high-throughput screen of 1,836 bioactive molecules and a thorough re-analysis of more than 60 molecules previously identified as promoting oligodendrocyte formation from human, rat, or mouse oligodendrocyte progenitor cells. These studies highlight that an overwhelming fraction of validated screening hits, including several molecules being evaluated clinically for remyelination, inhibit cholesterol pathway enzymes like emopamil-binding protein (EBP). To rationalize these findings, we suggest a model that relies on the high druggability of sterol-metabolizing enzymes and the ability of cationic amphiphiles to mimic the transition state of EBP. These studies further establish cholesterol pathway inhibition as a dominant mechanism among screening hits that enhance human, rat, or mouse oligodendrocyte formation.

Changes in thumb tapping rates and central motor conduction times are associated in persons with multiple sclerosis

Introduction

In persons with multiple sclerosis, nerve conductivity can be reduced. The assessment is generally performed via motor evoked potentials (MEP). So far, a strongly associated motor performance surrogate for changes in the extracted central motor conduction time (CMCT) is missing.

Methods

CMCT and performance in the nine-hole peg test and maximum thumb tapping frequencies over 10 s of 12 persons with multiple sclerosis were measured prior to and after training over 5 consecutive days. Each training consisted of 10,000 thumb taps at maximum effort with the dominant upper limb.

Results

The dominant upper limb improved in maximum tapping frequency over 10 s (d = 0.79) and 10,000 taps (d = 1.04), the nine-hole peg test (d = 0.60), and CMCT (d = 0.52). The nondominant upper limb only improved in the nine-hole peg test (d = 0.38). Models of multiple linear regression predicted 0.78 (model 1, tapping performance as factors) and 0.87 (model 2, patient baseline characteristics as factors) of the variance in CMCT changes.

Discussion

Changes in CMCT were well predictable, although the assessment of those surrogates is either not economic (model 1) or rather describing a potential of change (model 2). However, we were able to show moderate changes in CMCT within 5 days.

Targeting Fibronectin to Overcome Remyelination Failure in Multiple Sclerosis: The Need for Brain- and Lesion-Targeted Drug Delivery

Multiple sclerosis (MS) is a neuroinflammatory and neurodegenerative disease with unknown etiology that can be characterized by the presence of demyelinated lesions. Prevailing treatment protocols in MS rely on the modulation of the inflammatory process but do not impact disease progression. Remyelination is an essential factor for both axonal survival and functional neurological recovery but is often insufficient. The extracellular matrix protein fibronectin contributes to the inhibitory environment created in MS lesions and likely plays a causative role in remyelination failure. The presence of the blood–brain barrier (BBB) hinders the delivery of remyelination therapeutics to lesions. Therefore, therapeutic interventions to normalize the pathogenic MS lesion environment need to be able to cross the BBB. In this review, we outline the multifaceted roles of fibronectin in MS pathogenesis and discuss promising therapeutic targets and agents to overcome fibronectin-mediated inhibition of remyelination. In addition, to pave the way for clinical use, we reflect on opportunities to deliver MS therapeutics to lesions through the utilization of nanomedicine and discuss strategies to deliver fibronectin-directed therapeutics across the BBB. The use of well-designed nanocarriers with appropriate surface functionalization to cross the BBB and target the lesion sites is recommended.

Hedgehog Signaling in CNS Remyelination

Remyelination is a fundamental repair process in the central nervous system (CNS) that is triggered by demyelinating events. In demyelinating diseases, oligodendrocytes (OLs) are targeted, leading to myelin loss, axonal damage, and severe functional impairment. While spontaneous remyelination often fails in the progression of demyelinating diseases, increased understanding of the mechanisms and identification of targets that regulate myelin regeneration becomes crucial. To date, several signaling pathways have been implicated in the remyelination process, including the Hedgehog (Hh) signaling pathway. This review summarizes the current data concerning the complicated roles of the Hh signaling pathway in the context of remyelination. We will highlight the open issues that have to be clarified prior to bringing molecules targeting the Hh signaling to demyelinating therapy.

Investigating the NLRP3 Inflammasome and its Regulator miR-223-3p in Multiple Sclerosis and Experimental Demyelination

Innate immune signalling pathways are essential mediators of inflammation and repair following myelin injury. Inflammasome activation has recently been implicated as a driver of myelin injury in multiple sclerosis (MS) and its animal models, although the regulation and contributions of inflammasome activation in the demyelinated central nervous system (CNS) are not completely understood. Herein, we investigated the NLRP3 (NBD-, LRR- and pyrin domain-containing protein 3) inflammasome and its endogenous regulator microRNA-223-3p within the demyelinated CNS in both MS and an animal model of focal demyelination. We observed that NLRP3 inflammasome components and microRNA-223-3p were upregulated at sites of myelin injury within activated macrophages and microglia. Both microRNA-223-3p and a small-molecule NLRP3 inhibitor, MCC950, supressed inflammasome activation in macrophages and microglia in vitro; compared with microglia, macrophages were more prone to inflammasome activation in vitro. Finally, systemic delivery of MCC950 to mice following lysolecithin-induced demyelination resulted in a significant reduction in axonal injury within demyelinated lesions. In conclusion, we demonstrate that NLRP3 inflammasome activity by macrophages and microglia is a critical component of the inflammatory microenvironment following demyelination and represents a potential therapeutic target for inflammatory-mediated demyelinating diseases, including MS.

Oligodendrocyte death and myelin loss in the cuprizone model: an updated overview of the intrinsic and extrinsic causes of cuprizone demyelination

The dietary consumption of cuprizone – a copper chelator – has long been known to induce demyelination of specific brain structures and is widely used as model of multiple sclerosis. Despite the extensive use of cuprizone, the mechanism by which it induces demyelination are still unknown. With this review we provide an updated understanding of this model, by showcasing two distinct yet overlapping modes of action for cuprizone-induced demyelination; 1) damage originating from within the oligodendrocyte, caused by mitochondrial dysfunction or reduced myelin protein synthesis. We term this mode of action ‘intrinsic cell damage’. And 2) damage to the oligodendrocyte exerted by inflammatory molecules, brain resident cells, such as oligodendrocytes, astrocytes, and microglia or peripheral immune cells – neutrophils or T-cells. We term this mode of action ‘extrinsic cellular damage’. Lastly, we summarize recent developments in research on different forms of cell death induced by cuprizone, which could add valuable insights into the mechanisms of cuprizone toxicity. With this review we hope to provide a modern understanding of cuprizone-induced demyelination to understand the causes behind the demyelination in MS.

Versican promotes T helper 17 cytotoxic inflammation and impedes oligodendrocyte precursor cell remyelination

Remyelination failure in multiple sclerosis (MS) contributes to progression of disability. The deficient repair results from neuroinflammation and deposition of inhibitors including chondroitin sulfate proteoglycans (CSPGs). Which CSPG member is repair-inhibitory or alters local inflammation to exacerbate injury is unknown. Here, we correlate high versican-V1 expression in MS lesions with deficient premyelinating oligodendrocytes, and highlight its selective upregulation amongst CSPG members in experimental autoimmune encephalomyelitis (EAE) lesions modeling MS. In culture, purified versican-V1 inhibits oligodendrocyte precursor cells (OPCs) and promotes T helper 17 (Th17) polarization. Versican-V1-exposed Th17 cells are particularly toxic to OPCs. In NG2^CreER:MAPT^mGFP mice illuminating newly formed GFP⁺ oligodendrocytes/myelin, difluorosamine (peracetylated,4,4-difluoro-N-acetylglucosamine) treatment from peak EAE reduces lesional versican-V1 and Th17 frequency, while enhancing GFP⁺ profiles. We suggest that lesion-elevated versican-V1 directly impedes OPCs while it indirectly inhibits remyelination through elevating local Th17 cytotoxic neuroinflammation. We propose CSPG-lowering drugs as potential dual pronged repair and immunomodulatory therapeutics for MS.

Ghorbani and colleagues describe versican-V1 as an inhibitor of remyelination using transgenic mice that illuminate new GFP ⁺ oligodendrocytes. Mechanisms of versican-V1 include the direct inhibition of oligodendrocytes, and elevating Th17 cells.

Bu Shen Yi Sui Capsules Promote Remyelination by Regulating MicroRNA-219 and MicroRNA-338 in Exosomes to Promote Oligodendrocyte Precursor Cell Differentiation

Remyelination is a refractory feature of demyelinating diseases such as multiple sclerosis (MS). Studies have shown that promoting oligodendrocyte precursor cell (OPC) differentiation, which cannot be achieved by currently available therapeutic agents, is the key to enhancing remyelination. Bu Shen Yi Sui capsule (BSYSC) is a traditional Chinese herbal medicine over many years of clinical practice. We have found that BSYSC can effectively treat MS. In this study, the effects of BSYSC in promoting OPCs differentiation and remyelination were assessed using an experimental autoimmune encephalomyelitis (EAE) model in vivo and cultured OPCs in vitro. The results showed that BSYSC reduced clinical function scores and increased neuroprotection. The expression of platelet-derived growth factor receptor α (PDGFR-α) was decreased and the level of 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase) was increased in the brains and spinal cords of mice as well as in OPCs after treatment with BSYSC. We further found that BSYSC elevated the expression of miR-219 or miR-338 in the serum exosomes of mice with EAE, thereby suppressing the expression of Sox6, Lingo1, and Hes5, which negatively regulate OPCs differentiation. Therefore, serum exosomes of BSYSC-treated mice (exos-BSYSC) were extracted and administered to OPCs in which miR-219 or miR-338 expression was knocked down by adenovirus, and the results showed that Sox6, Lingo1, and Hes5 expression was downregulated, MBP expression was upregulated, OPCs differentiation was increased, and the ability of OPCs to wrap around neuronal axons was improved. In conclusion, BSYSC may exert clinically relevant effects by regulating microRNA (miR) levels in exosomes and thus promoting the differentiation and maturation of OPCs.

Neuroprotective effect of liraglutide in an experimental mouse model of multiple sclerosis: role of AMPK/SIRT1 signaling and NLRP3 inflammasome

The heterogeneous nature of multiple sclerosis (MS) and the unavailability of treatments addressing its intricate network and reversing the disease state is yet an area that needs to be elucidated. Liraglutide, a glucagon-like peptide-1 analogue, recently exhibited intriguing potential neuroprotective effects. The currents study investigated its potential effect against mouse model of MS and the possible underlying mechanisms. Demyelination was induced in C57Bl/6 mice by cuprizone (400 mg/kg/day p.o.) for 5 weeks. Animals received either liraglutide (25 nmol/kg/day i.p.) or dorsomorphin, an AMPK inhibitor, (2.5 mg/Kg i.p.) 30 min before the liraglutide dose, for 4 weeks (starting from the second week). Liraglutide improved the behavioral profile in cuprizone-treated mice. Furthermore, it induced the re-myelination process through stimulating oligodendrocyte progenitor cells differentiation via Olig2 transcription activation, reflected by increased myelin basic protein and myelinated nerve fiber percentage. Liraglutide elevated the protein content of p-AMPK and SIRT1, in addition to the autophagy proteins Beclin-1 and LC3B. Liraglutide halted cellular damage as manifested by reduced HMGB1 protein and consequently TLR-4 downregulation, coupled with a decrease in NF-κB. Liraglutide also suppressed NLRP3 transcription. Dorsomorphin pre-administration indicated a possible interplay between AMPK/SIRT1 and NLRP3 inflammasome activation as it partially reversed liraglutide’s effects. Immunohistochemical examination of Iba⁺ microglia emphasized these findings. In conclusion, liraglutide exerts neuroprotection against cuprizone-induced demyelination via anti-inflammatory, autophagic flux activation, NLRP3 inflammasome suppression, and anti-apoptotic mechanisms, possibly mediated, at least in part, via AMPK/SIRT1, autophagy, TLR-4/ NF-κB/NLRP3 signaling.

Cerebrospinal fluid of progressive multiple sclerosis patients reduces differentiation and immune functions of oligodendrocyte progenitor cells

Oligodendrocyte progenitor cells (OPCs) are responsible for remyelination in the central nervous system (CNS) in health and disease. For patients with multiple sclerosis (MS), remyelination is not always successful, and the mechanisms differentiating successful from failed remyelination are not well‐known. Growing evidence suggests an immune role for OPCs, in addition to their regenerative role; however, it is not clear if this helps or hinders the regenerative process. We studied the effect of cerebrospinal fluid (CSF) from relapsing MS (rMS) and progressive MS (pMS) patients on primary OPC differentiation and immune gene expression and function. We observed that CSF from either rMS or pMS patients has a differential effect on the ability of mice OPCs to differentiate into mature oligodendrocytes and to express immune functions. CSF of pMS patients impaired differentiation into mature oligodendrocytes. In addition, it led to decreased major histocompatibility complex class (MHC)‐II expression, tumor necrosis factor (TNF)‐α secretion, nuclear factor kappa‐B (NFκB) activation, and less activation and proliferation of T cells. Our findings suggest that OPCs are not only responsible for remyelination, but they may also play an active role as innate immune cells in the CNS.

Restoring nuclear entry of Sirtuin 2 in oligodendrocyte progenitor cells promotes remyelination during ageing

The age-dependent decline in remyelination potential of the central nervous system during ageing is associated with a declined differentiation capacity of oligodendrocyte progenitor cells (OPCs). The molecular players that can enhance OPC differentiation or rejuvenate OPCs are unclear. Here we show that, in mouse OPCs, nuclear entry of SIRT2 is impaired and NAD⁺ levels are reduced during ageing. When we supplement β-nicotinamide mononucleotide (β-NMN), an NAD⁺ precursor, nuclear entry of SIRT2 in OPCs, OPC differentiation, and remyelination were rescued in aged animals. We show that the effects on myelination are mediated via the NAD⁺-SIRT2-H3K18Ac-ID4 axis, and SIRT2 is required for rejuvenating OPCs. Our results show that SIRT2 and NAD⁺ levels rescue the aged OPC differentiation potential to levels comparable to young age, providing potential targets to enhance remyelination during ageing.

Age-dependent decline in remyelination in the CNS is associated with declined differentiation capacity of oligodendrocyte progenitor cells (OPCs). Here, the authors show nuclear entry of SIRT2 is impaired and NAD+ levels are reduced during ageing in mouse OPCs. β-nicotinamide mononucleotide (β-NMN) supplement delays myelin aging and enhances remyelination in the aged mice.

Are Cell-Based Therapies Safe and Effective in the Treatment of Neurodegenerative Diseases? A Systematic Review with Meta-Analysis

Over the past two decades, significant advances have been made in the field of regenerative medicine. However, despite being of the utmost clinical urgency, there remains a paucity of therapeutic strategies for conditions with substantial neurodegeneration such as (progressive) multiple sclerosis (MS), spinal cord injury (SCI), Parkinson's disease (PD) and Alzheimer's disease (AD). Different cell types, such as mesenchymal stromal cells (MSC), neuronal stem cells (NSC), olfactory ensheathing cells (OEC), neurons and a variety of others, already demonstrated safety and regenerative or neuroprotective properties in the central nervous system during the preclinical phase. As a result of these promising findings, in recent years, these necessary types of cell therapies have been intensively tested in clinical trials to establish whether these results could be confirmed in patients. However, extensive research is still needed regarding elucidating the exact mechanism of action, possible immune rejection, functionality and survival of the administered cells, dose, frequency and administration route. To summarize the current state of knowledge, we conducted a systematic review with meta-analysis. A total of 27,043 records were reviewed by two independent assessors and 71 records were included in the final quantitative analysis. These results show that the overall frequency of serious adverse events was low: 0.03 (95% CI: 0.01-0.08). In addition, several trials in MS and SCI reported efficacy data, demonstrating some promising results on clinical outcomes. All randomized controlled studies were at a low risk of bias due to appropriate blinding of the treatment, including assessors and patients. In conclusion, cell-based therapies in neurodegenerative disease are safe and feasible while showing promising clinical improvements. Nevertheless, given their high heterogeneity, the results require a cautious approach. We advocate for the harmonization of study protocols of trials investigating cell-based therapies in neurodegenerative diseases, adverse event reporting and investigation of clinical outcomes.

Central nervous system macrophages in progressive multiple sclerosis: relationship to neurodegeneration and therapeutics

There are over 15 disease-modifying drugs that have been approved over the last 20 years for the treatment of relapsing–remitting multiple sclerosis (MS), but there are limited treatment options available for progressive MS. The development of new drugs for the treatment of progressive MS remains challenging as the pathophysiology of progressive MS is poorly understood.

The progressive phase of MS is dominated by neurodegeneration and a heightened innate immune response with trapped immune cells behind a closed blood–brain barrier in the central nervous system. Here we review microglia and border-associated macrophages, which include perivascular, meningeal, and choroid plexus macrophages, during the progressive phase of MS. These cells are vital and are largely the basis to define lesion types in MS. We will review the evidence that reactive microglia and macrophages upregulate pro-inflammatory genes and downregulate homeostatic genes, that may promote neurodegeneration in progressive MS. We will also review the factors that regulate microglia and macrophage function during progressive MS, as well as potential toxic functions of these cells. Disease-modifying drugs that solely target microglia and macrophage in progressive MS are lacking. The recent treatment successes for progressive MS include include B-cell depletion therapies and sphingosine-1-phosphate receptor modulators. We will describe several therapies being evaluated as a potential treatment option for progressive MS, such as immunomodulatory therapies that can target myeloid cells or as a potential neuroprotective agent.

A Preliminary DTI Tractography Study of Developmental Neuroplasticity 5-15 Years After Early Childhood Traumatic Brain Injury

Plasticity is often implicated as a reparative mechanism when addressing structural and functional brain development in young children following traumatic brain injury (TBI); however, conventional imaging methods may not capture the complexities of post-trauma development. The present study examined the cingulum bundles and perforant pathways using diffusion tensor imaging (DTI) in 21 children and adolescents (ages 10–18 years) 5–15 years after sustaining early childhood TBI in comparison with 19 demographically-matched typically-developing children. Verbal memory and executive functioning were also evaluated and analyzed in relation to DTI metrics. Beyond the expected direction of quantitative DTI metrics in the TBI group, we also found qualitative differences in the streamline density of both pathways generated from DTI tractography in over half of those with early TBI. These children exhibited hypertrophic cingulum bundles relative to the comparison group, and the number of tract streamlines negatively correlated with age at injury, particularly in the late-developing anterior regions of the cingulum; however, streamline density did not relate to executive functioning. Although streamline density of the perforant pathway was not related to age at injury, streamline density of the left perforant pathway was significantly and positively related to verbal memory scores in those with TBI, and a moderate effect size was found in the right hemisphere. DTI tractography may provide insight into developmental plasticity in children post-injury. While traditional DTI metrics demonstrate expected relations to cognitive performance in group-based analyses, altered growth is reflected in the white matter structures themselves in some children several years post-injury. Whether this plasticity is adaptive or maladaptive, and whether the alterations are structure-specific, warrants further investigation.

Smoothened/AMP-Activated Protein Kinase Signaling in Oligodendroglial Cell Maturation

The regeneration of myelin is known to restore axonal conduction velocity after a demyelinating event. Remyelination failure in the central nervous system contributes to the severity and progression of demyelinating diseases such as multiple sclerosis. Remyelination is controlled by many signaling pathways, such as the Sonic hedgehog (Shh) pathway, as shown by the canonical activation of its key effector Smoothened (Smo), which increases the proliferation of oligodendrocyte precursor cells via the upregulation of the transcription factor Gli1. On the other hand, the inhibition of Gli1 was also found to promote the recruitment of a subset of adult neural stem cells and their subsequent differentiation into oligodendrocytes. Since Smo is also able to transduce Shh signals via various non-canonical pathways such as the blockade of Gli1, we addressed the potential of non-canonical Smo signaling to contribute to oligodendroglial cell maturation in myelinating cells using the non-canonical Smo agonist GSA-10, which downregulates Gli1. Using the Oli-neuM cell line, we show that GSA-10 promotes Gli2 upregulation, MBP and MAL/OPALIN expression via Smo/AMP-activated Protein Kinase (AMPK) signaling, and efficiently increases the number of axonal contact/ensheathment for each oligodendroglial cell. Moreover, GSA-10 promotes the recruitment and differentiation of oligodendroglial progenitors into the demyelinated corpus callosum in vivo. Altogether, our data indicate that non-canonical signaling involving Smo/AMPK modulation and Gli1 downregulation promotes oligodendroglia maturation until axon engagement. Thus, GSA-10, by activation of this signaling pathway, represents a novel potential remyelinating agent.

Analysis of Multifocal Visual Evoked Potentials Using Artificial Intelligence Algorithms

Purpose

Clinical trials for remyelination in multiple sclerosis (MS) require an imaging biomarker. The multifocal visual evoked potential (mfVEP) is an accurate technique for measuring axonal conduction; however, it produces large datasets requiring lengthy analysis by human experts to detect measurable responses versus noisy traces. This study aimed to develop a machine-learning approach for the identification of true responses versus noisy traces and the detection of latency peaks in measurable signals.

Methods

We obtained 2240 mfVEP traces from 10 MS patients using the VS-1 mfVEP machine, and they were classified by a skilled expert twice with an interval of 1 week. Of these, 2025 (90%) were classified consistently and used for the study. ResNet-50 and VGG16 models were trained and tested to produce three outputs: no signal, up-sloped signal, or down-sloped signal. Each model ran 1000 iterations with a stochastic gradient descent optimizer with a learning rate of 0.0001.

Results

ResNet-50 and VGG16 had false-positive rates of 1.7% and 0.6%, respectively, when the testing dataset was analyzed (n = 612). The false-negative rates were 8.2% and 6.5%, respectively, against the same dataset. The latency measurements in the validation and testing cohorts in the study were similar.

Conclusions

Our models efficiently analyze mfVEPs with <2% false positives compared with human false positives of <8%.

Translational Relevance

mfVEP, a safe neurophysiological technique, analyzed using artificial intelligence, can serve as an efficient biomarker in MS clinical trials and signal latency measurement.