Progressive multiple sclerosis patients show substantial lesion activity that correlates with clinical disease severity and sex: a retrospective autopsy cohort analysis

Circulating myeloid-derived suppressor cell load and disease severity are associated to an enhanced oligodendroglial production in a murine model of multiple sclerosis

Multiple sclerosis (MS) is a highly heterogeneous immune-mediated demyelinating disease. Myelin restoration is essential to prevent disability progression in MS patients. However, remyelinating therapies are failing in clinical trials, in part, due to the lack of biomarkers that classify the differing endogenous regenerative capacities of enrolled patients. In the experimental autoimmune encephalomyelitis (EAE) MS model, circulating monocytic myeloid-derived suppressor cells (M-MDSCs) are associated to milder disease courses, better recovery and less degree of tissue damage. Here, we show that disease severity affects the gradient of oligodendrocyte precursor cells (OPCs) present in mixed active-inactive lesions of MS patients, along with a positive correlation between M-MDSC density and OPC abundance. EAE disease severity negatively influences the density of total and newly generated OPCs found associated to the demyelinated lesions. In addition, disease severity also impacts the abundance of newly generated oligodendrocytes throughout the EAE disease course. Interestingly, circulating M-MDSCs at EAE onset and peak of the disease are directly associated to a higher density of newly generated oligodendrocytes in the demyelinated lesions. Our results set the basis for further studies on M-MDSCs as a promising new biomarker that identify a CNS prone to new oligodendrocyte generation in response to an inflammatory insult.

New approaches to lesion assessment in multiple sclerosis

PURPOSE OF REVIEW

To summarize recent advancements in artificial intelligence-driven lesion segmentation and novel neuroimaging modalities that enhance the identification and characterization of multiple sclerosis (MS) lesions, emphasizing their implications for clinical use and research.

RECENT FINDINGS

Artificial intelligence, particularly deep learning approaches, are revolutionizing MS lesion assessment and segmentation, improving accuracy, reproducibility, and efficiency. Artificial intelligence-based tools now enable automated detection not only of T2-hyperintense white matter lesions, but also of specific lesion subtypes, including gadolinium-enhancing, central vein sign-positive, paramagnetic rim, cortical, and spinal cord lesions, which hold diagnostic and prognostic value. Novel neuroimaging techniques such as quantitative susceptibility mapping (QSM), χ-separation imaging, and soma and neurite density imaging (SANDI), together with PET, are providing deeper insights into lesion pathology, better disentangling their heterogeneities and clinical relevance.

SUMMARY

Artificial intelligence-powered lesion segmentation tools hold great potential for improving fast, accurate and reproducible lesional assessment in the clinical scenario, thus improving MS diagnosis, monitoring, and treatment response assessment. Emerging neuroimaging modalities may contribute to advance the understanding MS pathophysiology, provide more specific markers of disease progression, and novel potential therapeutic targets.

Multiple sclerosis severity variant in DYSF-ZNF638 locus associates with neuronal loss and inflammation

The genetic variant rs10191329AA has been identified to associate with faster disability accrual in multiple sclerosis (MS). We investigated the impact of rs10191329AA carriership on MS pathology and flanking genes dysferlin (DYSF) and zinc finger protein 638 (ZNF638) in the Netherlands Brain Bank cohort (n = 290) by comparing rs10191329AA (n = 6) to matched rs10191329CC carriers (n = 12). rs10191329AA carriership associated with more acute axonal stress, reduced layer 2 neuronal density, and a higher proportion of lesions with foamy microglia. In rs10191329AA donors, normal appearing white matter was characterized by a higher proportion of ZNF638+ oligodendrocytes, and normal appearing gray matter showed more DYSF+ cells. Nuclear RNA sequencing showed an upregulation of mitochondrial genes in rs10191329AA carriers. These data suggest that MS severity associates with an increased susceptibility to neurodegeneration and chronic inflammation. Understanding the role of DYSF, ZNF638, and mitochondrial pathways may reveal new therapeutic targets to attenuate MS progression.

Subcortical plaques and inflammation reflect cortical and meningeal pathologies in progressive multiple sclerosis

It remains elusive whether lesions and inflammation in the sub/juxtacortical white matter reflect cortical and/or meningeal pathologies. Elucidating this could have implications for MRI monitoring as sub/juxtacortical lesions are detectable by routine MRI, while cortical lesions and meningeal inflammation are not. By large-area microscopy, we quantified total and mixed active plaque loads along with densities and sizes of perivascular mononuclear infiltrates (infiltrates) in the sub/juxtacortical white matter ≤2 mm from the cortex, intra-cortically and in the meninges. Data were related to ante-mortem clinical parameters in a false discovery rate-corrected analysis. We compared 12 patients with primary progressive multiple sclerosis (PPMS) and 15 with secondary progressive MS to 22 controls. Fifteen patients and 11 controls contributed with hemispheric sections. Sections were stained with haematoxylin-eosin, for myelin and for microglia/macrophages. B cells and T cells were confirmed in a subset. Immunoglobulin G depositions in selected cortical plaques resembled depositions described before in "slowly expanding" plaques in the white matter. We quantified plaque activity by measuring microglia-dominated and macrophage-dominated areas. Sub/juxtacortical plaques (load and activity) reflected plaque activity in the cerebral cortex. Plaque activity and infiltrates were more pronounced in the sub/juxtacortical white matter than in the cerebral cortex while conversely, the total plaque load was highest in the cortex. Infiltrates correlated trans-cortically and sub/juxtacortical plaque activity reflected cortical and meningeal infiltrates. Sub/juxtacortical infiltrate sizes correlated with shorter survival after progression onset. Two patients with PPMS and putatively fatal brain stem lesions argue against incidental findings. Trans-cortical inflammatory flares and plaque activity may be pathogenic in progressive MS. We suggest emphasis on sub/juxtacortical MRI lesions as plausible surrogates for cortical and meningeal pathologies and, when present, as indicators for cognitive testing.

Broad rim lesions are a new pathological and imaging biomarker for rapid disease progression in multiple sclerosis

Current multiple sclerosis (MS) treatments reduce relapse activity but have limited impact on disease progression. Clinical trials targeting progression often fail because of insufficient understanding of its underlying mechanisms. This study analyzed a clinically well-characterized MS autopsy cohort from the Netherland Brain Bank (186 individuals) from which we selected donors exhibiting opposite disease trajectories of slow versus rapid progression. We performed extensive unbiased histology and spatial transcriptomics, which unveiled a distinct MS lesion type marked by an extensive myeloid cell rim with cellular and transcriptional signatures of innate immune activation, inflammatory cytokine production, unfolded protein response and apoptosis. Presence of this particular lesion type was linked to rapid disease progression. An independent translocator protein 18-kDa positron emission tomography study (114 individuals) validates the association between lesions with a broad myeloid cell rim and disease progression in individuals with MS. Our findings offer crucial insights into the mechanisms behind MS progression, identifying broad rim lesions as a biomarker for rapid disease progression and potentially guiding patient selection for future therapeutic trials targeting central nervous system intrinsic inflammation.

Multiple sclerosis: what have we learned and can we still learn from electron microscopy

Multiple sclerosis (MS) is an inflammatory neurodegenerative disease marked by the formation of demyelinated lesions in the central nervous system. MS lesions can undergo remyelination, temporarily alleviating symptoms, but as the disease advances, remyelination becomes less effective. Beyond lesions, normal-appearing brain tissue exhibits subtle alterations, potentially indicating a broader, diffuse pathology and/or increased susceptibility to lesion formation. The pathology of MS varies between grey and white matter lesions and their normal-appearing regions, which most likely relates to their distinct cellular composition. Despite insights gained from MRI studies, serum and blood analyses, and post-mortem tissue examination, the molecular mechanisms driving MS lesion formation and persistent demyelination remain poorly understood. Exploring less conventional methods, such as electron microscopy (EM), may provide valuable new insights. EM offers detailed, nanometre-scale structural analysis that may enhance findings from immunohistochemistry and 'omics' approaches on MS brain tissue. Although earlier EM studies from before the 1990's provided some foundational data, advancements in EM technology now enable more comprehensive and detailed structural analysis. In this review we outline the pathogenesis of MS, summarize current knowledge of its ultrastructural features, and highlight how cutting-edge EM techniques could uncover new insights into pathological processes, including lesion formation, remyelination failure and diffuse pathology, which may aid therapeutic development.

The characteristics and influencing factors of paramagnetic rim lesions in Chinese MS patients: A 7T MRI study

BACKGROUND

Paramagnetic rim lesions (PRLs) in multiple sclerosis (MS) are a significant factor for disability progression and prognosis, but their characteristics in the Chinese population are unclear.

OBJECTIVE

To explore PRLs in Chinese MS patients using 7T magnetic resonance imaging (MRI), including their number, proportion, distribution, and associated factors.

METHODS

Patients from the 7T MRI subgroup of the China National Registry of Neuro-Inflammatory Diseases (CNRID) were prospectively included. PRLs were assessed on susceptibility-weighted imaging (SWI)-phase images. Patients were grouped by PRL count (0, 1-3, 4-10, >10). Associations between clinical characteristics and PRL count were analyzed using multivariable linear regression, while correlations with disease duration were assessed using Pearson partial correlation and regression.

RESULTS

Among 110 participants, 96 (87.3%) had at least one PRL. In PRL groups, proportions were 12.7%, 20.0%, 29.1%, and 38.2%. PRL count positively correlated with Expanded Disability Status Scale (EDSS), total lesion count, and volume and negatively with Symbol Digit Modality Test (SDMT; p < 0.05). Longer disease duration was associated with a lower PRL proportion after adjusting for age and sex (β = -0.006, p = 0.032).

CONCLUSION

A high proportion of Chinese MS patients in our 7T MRI cohort had PRLs, with many exhibiting multiple PRLs (⩾4). PRL count was influenced by EDSS, SDMT, total lesion count, and volume, while PRL proportion negatively correlated with disease duration.

Impact of oral Cladribine on paramagnetic rim lesions of Multiple Sclerosis patients

BACKGROUND

Paramagnetic rim lesions (PRLs), marked by chronic inflammation and iron-loaded microglia, are linked to severe disease progression in multiple sclerosis (MS). The impact of cladribine, an immune reconstitution therapy, on PRLs remains underexplored.

OBJECTIVE

To evaluate the effect of cladribine tablets on PRLs in relapsing-remitting MS (RRMS) patients and explore the association between PRLs dynamics and brain atrophy.

METHODS

We conducted a retrospective analysis of 52 RRMS patients treated with cladribine in Buenos Aires between 2018 and 2021. Brain MRIs were analyzed at baseline, 12, and 24 months post-treatment, focusing on PRLs count and brain volume measurements. Statistical analyses included Wilcoxon tests, Poisson mixed models, and linear mixed models.

RESULTS

The cohort included 52 patients (32 women) with a median age of 36 years (range 21-66 years). PRLs were present in 61.5% of patients at baseline. Cladribine treatment significantly reduced PRLs count (IRR=0.68, 95% CI [0.49, 0.95], p=0.02), independent of prior treatment or disease activity. While no significant relationship was found between PRLs changes and overall brain atrophy, a significant interaction between PRLs dynamics and atrophy in the right thalamus was observed (p<0.05).

CONCLUSION

Cladribine tablets are associated with a reduction in PRLs in RRMS patients, potentially influencing regional brain atrophy over time.

Presence of slowly expanding lesions in multiple sclerosis predicts progressive demyelination within lesions and normal-appearing tissue over time

BACKGROUND

Multiple sclerosis (MS) slowly expanding lesions (SELs) are defined on magnetic resonance imaging (MRI) as contiguous regions of pre-existing focal non-contrast-enhancing T2 lesions with constant and concentric local expansion on conventional T1-weighted and T2-weighted images. SELs are associated with an increased risk of disability progression.

METHODS

Myelin-related changes detected using myelin water fraction (MWF) and magnetisation transfer ratio (MTR) in SELs and T2 lesions were measured over 192 weeks in participants with relapsing MS.

RESULTS

In participants with SELs (SEL+), SELs (MWF: 0.12 ± 0.03, MTR: 33.1 ± 3.6 pu) showed reduced myelin measures at baseline compared to T2 lesions (MWF: 0.13 ± 0.02, MTR: 35.1 ± 2.4 pu). In participants without SELs (SEL-), T2 lesions had higher myelin measures (MWF: 0.15 ± 0.02, MTR: 36.2 ± 2.0 pu) compared to T2 lesions in SEL+. Over 4 years, only SELs showed decreases in MWF (-11.4%). The percentage of abnormal voxels within normal-appearing white matter was higher in SEL+ and increased over time (SEL+ MWF Week 0: 0.56%, Week 192: 0.98%; SEL- MWF Week 0: 0.13%, Week 192: 0.25%).

CONCLUSION

Our results indicate progressive focal and global demyelination in SEL+ participants and that the presence of SELs might be a biomarker for participants with ongoing diffuse or smouldering inflammation within the whole brain.

Neurological disability and brain grey matter atrophy in primary progressive multiple sclerosis are determined by microstructural lesional changes, but not by lesion load

BACKGROUND

Conventional MRI measures, such as the number and volume of MS lesions, are histologically non-specific and cannot sufficiently explain clinical disability or brain atrophy in MS. Nevertheless, demyelinating plaques exhibit distinct histopathological features in relapsing and progressive multiple sclerosis (MS) subtypes. The aim of this study was to assess microstructural characteristics of MS lesions using quantitative MRI and explore their associations with grey matter (GM) atrophy and clinical disability.

METHODS

56 control subjects (CS), 121 patients with relapsing-remitting (RRMS), and 38 patients with primary progressive MS (PPMS) underwent 1.5 T MRI scans and clinical examinations. Lesion and brain segmentation based on T1-weighted and FLAIR images were performed using SAMSEG. The MDME sequence and SyMRI software were used to estimate relaxation rates and myelin volume fraction in MS lesions and normal-appearing white matter (NAWM). Associations between quantitative lesional and NAWM MRI parameters with GM atrophy and clinical disability were investigated.

RESULTS

Brain regional volumes and quantitative lesional and NAWM MRI parameters were significantly decreased in patients with PPMS compared to those with RRMS. Quantitative lesional MRI parameters demonstrated statistically significant associations with cortical and deep GM volumes as well as with disability scores in RRMS and especially in PPMS. In contrast to RRMS, lesion volume was not associated with either GM atrophy or clinical disability in the PPMS group.

CONCLUSIONS

Quantitative lesional MRI measures, but not lesion load, were strongly associated with clinical disability and GM atrophy in PPMS patients, likely reflecting differences in lesion pathology between MS subtypes.

Neurodegeneration correlates of iron-related lesions and leptomeningeal inflammation in multiple sclerosis clinical subtypes

PURPOSE

The aim of this study was to investigate the significant implications of different types of lesions as assessed by QSM (quantitative-susceptibility-mapping) as well as leptomeningeal contrast-enhancement in a cohort of Relapsing-Remitting (RR) and Primary Progressive (PP) MS patients and to assess their association with clinical disability and MRI-measures of brain structural damage.

METHODS

Different types of white-matter lesions were identified and quantified using QSM in 24 RRMS and 15 PPMS (11 patients with follow-up MRI). Leptomeningeal contrast-enhancement (LMCE; foci) was assessed on 3D-FLAIR post-gadolinium.

RESULTS

Both RRMS and PPMS presented PRL (paramagnetic-rim lesions) and LMCE, with PPMS showing a trend towards more LMCE (RRMS 37%, PPMS 53%). In QSM RRMS patients showed more hyperintense white-matter lesions with greater lesion volume. In RRMS PRL correlated with disease duration and lesion burden especially the volume of juxtacortical Flair-hyperintense lesions. Besides, the presence of PRL lesions in PPMS was associated with subcortical atrophy mainly thalamus and pallidum volumetry. In all MS-cohort, patients with more than 3-PRLs exhibited reduced regional cortical thickness in specific temporal areas and post/para central gyrus. Forest-analysis selected age, increased NAWM (normal appearing white-matter) QSM intensity, total lesion volume and the presence of LMCE as informative predictors of cortical thickness. After anti-CD20 treatment, no significant change was observed regarding the number of PRL and LMCE, but the percentage of PRL lesions over the total lesion types and the QSM rim intensity increased.

CONCLUSION

Our findings suggest that QSM-lesion types and leptomeningeal inflammation capture different aspects of progressive disease biology in both RRMS and PPMS.

Multiple Sclerosis and Other Acquired Demyelinating Diseases of the Central Nervous System

Acquired demyelinating diseases of the central nervous system (CNS) comprise inflammatory conditions, including multiple sclerosis (MS) and related diseases, as well as noninflammatory conditions caused by toxic, metabolic, infectious, traumatic, and neurodegenerative insults. Here, we review the spectrum of diseases producing acquired CNS demyelination before focusing on the prototypical example of MS, exploring the pathologic mechanisms leading to myelin injury in relapsing and progressive MS and summarizing the mechanisms and modulators of remyelination. We highlight the complex interplay between the immune system, oligodendrocytes and oligodendrocyte progenitor cells (OPCs), and other CNS glia cells such as microglia and astrocytes in the pathogenesis and clinical course of MS. Finally, we review emerging therapeutic strategies that exploit our growing understanding of disease mechanisms to limit progression and promote remyelination.

Multiple Sclerosis: Glial Cell Diversity in Time and Space

Multiple sclerosis (MS) is the most prevalent human inflammatory disease of the central nervous system with demyelination and glial scar formation as pathological hallmarks. Glial cells are key drivers of lesion progression in MS with roles in both tissue damage and repair depending on the surrounding microenvironment and the functional state of the individual glial subtype. In this review, we describe recent developments in the context of glial cell diversity in MS summarizing key findings with respect to pathological and maladaptive functions related to disease-associated glial subtypes. A particular focus is on the spatial and temporal dynamics of glial cells including subtypes of microglia, oligodendrocytes, and astrocytes. We contextualize recent high-dimensional findings suggesting that glial cells dynamically change with respect to epigenomic, transcriptomic, and metabolic features across the inflamed rim and during the progression of MS lesions. In summary, detailed knowledge of spatially restricted glial subtype functions is critical for a better understanding of MS pathology and its pathogenesis as well as the development of novel MS therapies targeting specific glial cell types.

CLEC16A in astrocytes promotes mitophagy and limits pathology in a multiple sclerosis mouse model

Astrocytes promote neuroinflammation and neurodegeneration in multiple sclerosis (MS) through cell-intrinsic activities and their ability to recruit and activate other cell types. In a genome-wide CRISPR-based forward genetic screen investigating regulators of astrocyte proinflammatory responses, we identified the C-type lectin domain-containing 16A gene (CLEC16A), linked to MS susceptibility, as a suppressor of nuclear factor-κB (NF-κB) signaling. Gene and small-molecule perturbation studies in mouse primary and human embryonic stem cell-derived astrocytes in combination with multiomic analyses established that CLEC16A promotes mitophagy, limiting mitochondrial dysfunction and the accumulation of mitochondrial products that activate NF-κB, the NLRP3 inflammasome and gasdermin D. Astrocyte-specific Clec16a inactivation increased NF-κB, NLRP3 and gasdermin D activation in vivo, worsening experimental autoimmune encephalomyelitis, a mouse model of MS. Moreover, we detected disrupted mitophagic capacity and gasdermin D activation in astrocytes in samples from individuals with MS. These findings identify CLEC16A as a suppressor of astrocyte pathological responses and a candidate therapeutic target in MS.

RNA Binding Protein Dysfunction Links Smoldering/Slowly Expanding Lesions to Neurodegeneration in Multiple Sclerosis

OBJECTIVE

Despite the advances in treatments for multiple sclerosis (MS), unremitting neurodegeneration continues to drive disability and disease progression. Smoldering/slowly expanding lesions (SELs) and dysfunction of the RNA binding protein (RBP) heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) are pathologic hallmarks of MS cortex and intricately tied to disability and neurodegeneration, respectively. We hypothesized that neuronal hnRNP A1 dysfunction contributes to neurodegeneration and is exacerbated by smoldering/SELs in progressive MS.

METHODS

Neuronal hnRNP A1 pathology (nucleocytoplasmic mislocalization of hnRNP A1) was examined in healthy control and MS brains using immunohistochemistry. MS cases were stratified by severity of hnRNP A1 pathology to examine the link between RBP dysfunction, demyelination, and neurodegeneration.

RESULTS

We found that smoldering/SELs were only present within a subset of MS tissues characterized by elevated neuronal hnRNP A1 pathology (MS-A1high) in adjacent cortical gray matter. In contrast to healthy controls and MS with low hnRNP A1 pathology (MS-A1low), MS-A1high showed elevated markers of neurodegeneration, including neuronal loss and injury, brain atrophy, axonal loss, and axon degeneration. Additionally, we discovered a subpopulation of morphologically intact neurons lacking expression of NeuN, a neuron-specific RBP, in cortical projection neurons in MS-A1high cases.

INTERPRETATION

hnRNP A1 dysfunction contributes to neurodegeneration and may be exacerbated by smoldering/SELs in progressive MS. The discovery of NeuN-negative neurons suggests that some cortical neurons may only be injured and not lost. By characterizing RBP pathology in MS cortex, this study has important implications for understanding the pathogenic mechanisms driving neurodegeneration, the substrate of disability and disease progression. ANN NEUROL 2025;97:313-328.

Multifaceted Biomarkers Suggest a Similar Profile of CNS Pathology in Relapsing and Progressive MS

BACKGROUND

Relapsing-remitting (RR) and primary progressive (PP) multiple sclerosis (MS) have distinct clinical courses, but underlying pathophysiological differences remain unclear. We compared pathological components between RRMS, PPMS, and other inflammatory and neurodegenerative disorders, leveraging soluble biomarkers and post-mortem pathology.

METHODS

Serum and cerebrospinal fluid (CSF) of people diagnosed with (pw) PPMS (n = 104), RRMS (n = 38), Alzheimer's disease (AD, n = 22), neuromyelitis optica spectrum disorder (NMOSD, n = 10), and myelin oligodendrocyte glycoprotein-associated disease (MOGAD, n = 10) were collected. B-cell maturation antigen (BCMA), soluble CD27 (sCD27), osteopontin (OPN), chitinase-3-like-1 (CHI3L1), glial fibrillary acidic protein (GFAP), neurofilament light chain (NfL) and synaptosomal-associated protein-25 (SNAP25) were measured. Lymphocytes (CD20+, CD138+, CD3+) and pyramidal-tract axonal density in RR-onset (n = 86) and PPMS (n = 45) post-mortem brain tissue were quantified.

RESULTS

Soluble and post-mortem tissue biomarkers did not differ between pwRRMS and pwPPMS. Compared to AD, MS had higher CSF sCD27 (p < 0.001) but lower serum CHI3L1 and GFAP, and CSF OPN and SNAP25 (all p < 0.05). Serum OPN was lower in RRMS than NMOSD (p = 0.013). Principal component analyses and K-means clustering showed substantial overlap of RRMS and PPMS biomarkers, distinct from AD. In all pwMS, serum NfL and CSF BCMA correlated with clinical/radiological disease activity, CSF BCMA and sCD27 with inflammatory parameters, and serum GFAP, CSF GFAP, and CSF NfL with Expanded Disability Status Scale (EDSS) score.

CONCLUSIONS

Serum and CSF soluble biomarker profiles and post-mortem pathology do not differentiate RRMS from PPMS diagnoses but reflect the extent of inflammation and tissue damage. Detailed assessment of MS-associated inflammation and tissue damage may enhance classification and therapeutic strategies.

Towards a biological view of multiple sclerosis from early subtle to clinical progression: an expert opinion

The classification of multiple sclerosis (MS) into the two distinct phases of relapsing-remitting and progressive, including primary progressive and secondary progressive phenotypes (PPMS and SPMS, respectively) has long been accepted; however, there are several unmet needs associated with this particular model. The observation that both inflammation and neurodegeneration are present from the onset of MS has resulted in a paradigm shift towards MS as a disease continuum driven by pathological mechanisms underlying clinical progression. Here we report the results from a meeting of Italian MS specialists, exploring the evolving perception of MS pathobiology and its implications for diagnosis and treatment. Insights garnered from the expert panel advocate for a redefined understanding of MS. This expert opinion paper reviews the disease continuum and the intertwined nature of inflammatory and neurodegenerative processes. Also, the need for changes in diagnostic criteria and treatment strategies, including the development of novel biomarkers and new therapies targeting smouldering disease, is discussed.

Inflammatory microglia correlate with impaired oligodendrocyte maturation in multiple sclerosis

Introduction

Remyelination of demyelinated axons can occur as an endogenous repair mechanism in multiple sclerosis (MS), but its efficacy varies between both MS individuals and lesions. The molecular and cellular mechanisms that drive remyelination remain poorly understood. Here, we studied the relation between microglia activation and remyelination activity in MS.

Methods

We correlated regenerative (CD163+) and inflammatory (iNOS+) microglia with BCAS1+ oligodendrocytes, subdivided into early-stage (<3 processes) and late-stage (≥3 processes) cells in brain donors with high or low remyelinating potential in remyelinated lesions and active lesions with ramified/amoeboid (non-foamy) or foamy microglia. A cohort of MS donors categorized as efficiently remyelinating donors (ERDs; n=25) or poorly remyelinating donors (PRDs; n=17) was included, based on their proportion of remyelinated lesions at autopsy.

Results and discussion

We hypothesized more CD163+ microglia and BCAS1+ oligodendrocytes in remyelinated and active non-foamy lesions from ERDs and more iNOS+ microglia with fewer BCAS1+ oligodendrocytes in active foamy lesions from PRDs. For CD163+ microglia, however, no differences were observed between MS lesions and MS donor groups. In line with our hypothesis, we found that INOS+ microglia were significantly increased in PRDs compared to ERDs within remyelinated lesions. MS lesions, more late-stage BCAS1+ oligodendrocytes were detected in active lesions with non-foamy or foamy microglia in comparison with remyelinated lesions. Although no differences were found for early-stage BCAS1+ oligodendrocytes between MS lesions, we did find significantly more early-stage BCAS1+ oligodendrocytes in PRDs vs ERDs in remyelinated lesions. Interestingly, a positive correlation was identified between iNOS+ microglia and the presence of early-stage BCAS1+ oligodendrocytes. These findings suggest that impaired maturation of early-stage BCAS1+ oligodendrocytes, encountering inflammatory microglia, may underlie remyelination deficits and unsuccessful lesion repair in MS.

Exploring the role of sex hormones and gender diversity in multiple sclerosis

Sex and sex hormones are thought to influence multiple sclerosis (MS) through effects on inflammation, myelination and neurodegeneration, and exogenous hormones have been explored for their therapeutic potential. However, our understanding of how sex hormones influence MS disease processes and outcomes remains incomplete. Furthermore, our current knowledge is derived primarily from studies that focus exclusively on cisgender populations with exclusion of gender-diverse people. Gender-affirming hormone therapy comprising exogenous sex hormones or sex hormone blocking agents are commonly used by transgender and gender-diverse individuals, and it could influence MS risk and outcomes at various stages of disease. A better understanding of the impact and potential therapeutic effects of both endogenous and exogenous sex hormones in MS is needed to improve care and outcomes for cisgender individuals and, moreover, for gender-diverse populations wherein an evidence base does not exist. In this Perspective, we discuss the effects of endogenous and exogenous sex hormones in MS, including their potential therapeutic benefits, and examine both established sex-based dimorphisms and the potential for gender-diverse dimorphisms. We advocate for future research that includes gender-diverse people to enhance our knowledge of the interplay of sex and sex hormones in MS, leading to the development of more effective and inclusive treatment strategies and improvement of care for all individuals with MS.

Chronic active lesions in multiple sclerosis: classification, terminology, and clinical significance

In multiple sclerosis (MS), increasing disability is considered to occur due to persistent, chronic inflammation trapped within the central nervous system (CNS). This condition, known as smoldering neuroinflammation, is present across the clinical spectrum of MS and is currently understood to be relatively resistant to treatment with existing disease-modifying therapies. Chronic active white matter lesions represent a key component of smoldering neuroinflammation. Initially characterized in autopsy specimens, multiple approaches to visualize chronic active lesions (CALs) in vivo using advanced neuroimaging techniques and postprocessing methods are rapidly emerging. Among these in vivo imaging correlates of CALs, paramagnetic rim lesions (PRLs) are defined by the presence of a perilesional rim formed by iron-laden microglia and macrophages, whereas slowly expanding lesions are identified based on linear, concentric lesion expansion over time. In recent years, several longitudinal studies have linked the occurrence of in vivo detected CALs to a more aggressive disease course. PRLs are highly specific to MS and therefore have recently been incorporated into the MS diagnostic criteria. They also have prognostic potential as biomarkers to identify patients at risk of early and severe disease progression. These developments could significantly affect MS care and the evaluation of new treatments. This review describes the latest knowledge on CAL biology and imaging and the relevance of CALs to the natural history of MS. In addition, we outline considerations for current and future in vivo biomarkers of CALs, emphasizing the need for validation, standardization, and automation in their assessment.

Magnetic resonance imaging-based biomarkers of multiple sclerosis and neuromyelitis optica spectrum disorder: a systematic review and meta-analysis

BACKGROUND/OBJECTIVE

Multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) are neuroinflammatory conditions with overlapping clinical and imaging features. Distinguishing between these diseases is crucial for appropriate diagnosis and management. Magnetic resonance imaging (MRI) may have the potential to differentiate these disorders. Nonetheless, studies exhibit inconsistencies regarding which MRI measurements most effectively distinguish between these disorders. Hence, this review aimed to evaluate the differences in MRI volumetry between people with MS (PwMS) and people with NMOSD (PwNMOSD).

METHODS

A systematic search was conducted across PubMed/MEDLINE, Embase, Scopus, and Web of Science up to May 12, 2024, to identify studies assessing conventional and volumetric MRI in PwMS and PwNMOSD. The standard mean difference (SMD) of MRI measurements and its 95% confidence interval (CI) were estimated using R version 4.4.0 with a random-effects model.

RESULTS

Forty-eight original studies that assessed conventional MRI measurements in 2592 PwMS and 1979 PwNMOSD were included. The meta-analysis revealed that PwMS had significantly higher T2 lesion volume (SMD = 1.51, 95% CI: 0.53 to 2.48, p = 0.002) and T1 lesion count (SMD = 1.08, 95% CI: 0.56 to 1.6, p < 0.001) than PwNMOSD. PwMS also exhibited significantly reduced thalamic volume (SMD = -1.26, 95% CI: -1.8 to -0.73, p < 0.001) and grey matter volume (GMV) (SMD = -0.65, 95% CI: -0.92 to -0.37, p < 0.001). Other MRI volumetry, such as the brain and putamen volumes, showed more pronounced atrophy in PwMS.

CONCLUSION

Significant differences in MRI volumetry between MS and NMOSD highlight the potential of MRI as a critical diagnostic tool. These findings emphasize the need for standardized MRI protocols and advanced imaging techniques to enhance diagnostic accuracy and clinical management of these conditions.

The Search for a Universal Treatment for Defined and Mixed Pathology Neurodegenerative Diseases

The predominant neurodegenerative diseases, Alzheimer's disease, Parkinson's disease, dementia with Lewy Bodies, Huntington's disease, amyotrophic lateral sclerosis, and frontotemporal dementia, are rarely pure diseases but, instead, show a diversity of mixed pathologies. At some level, all of them share a combination of one or more different toxic biomarker proteins: amyloid beta (Aβ), phosphorylated Tau (pTau), alpha-synuclein (αSyn), mutant huntingtin (mHtt), fused in sarcoma, superoxide dismutase 1, and TAR DNA-binding protein 43. These toxic proteins share some common attributes, making them potentially universal and simultaneous targets for therapeutic intervention. First, they all form toxic aggregates prior to taking on their final forms as contributors to plaques, neurofibrillary tangles, Lewy bodies, and other protein deposits. Second, the primary enzyme that directs their aggregation is transglutaminase 2 (TGM2), a brain-localized enzyme involved in neurodegeneration. Third, TGM2 binds to calmodulin, a regulatory event that can increase the activity of this enzyme threefold. Fourth, the most common mixed pathology toxic biomarkers (Aβ, pTau, αSyn, nHtt) also bind calmodulin, which can affect their ability to aggregate. This review examines the potential therapeutic routes opened up by this knowledge. The end goal reveals multiple opportunities that are immediately available for universal therapeutic treatment of the most devastating neurodegenerative diseases facing humankind.

Myeloid antigen-presenting cells in neurodegenerative diseases: a focus on classical and non-classical MHC molecules

In recent years, increasing evidence has highlighted the critical role of myeloid cells, specifically those that present antigen (APCs) in health and disease. These shape the progression and development of neurodegenerative disorders, where considerable interplay between the immune system and neurons influences the course of disease pathogenesis. Antigen-presenting myeloid cells display different classes of major histocompatibility complex (MHC) and MHC-like proteins on their surface for presenting various types of antigens to a wide variety of T cells. While most studies focus on the role of myeloid MHC class I and II molecules in health and disease, there is still much that remains unknown about non-polymorphic MHC-like molecules such as CD1d and MR1. Thus, in this review, we will summarize the recent findings regarding the contributions of both classical and non-classical MHC molecules, particularly on myeloid microglial APCs, in neurodegenerative diseases. This will offer a better understanding of altered mechanisms that may pave the way for the development of novel therapeutic strategies targeting immune cell-MHC interactions, to mitigate neurodegeneration and its associated pathology.

The molecular subtypes of autoimmune diseases

Autoimmune diseases (ADs) are characterized by their complexity and a wide range of clinical differences. Despite patients presenting with similar symptoms and disease patterns, their reactions to treatments may vary. The current approach of personalized medicine, which relies on molecular data, is seen as an effective method to address the variability in these diseases. This review examined the pathologic classification of ADs, such as multiple sclerosis and lupus nephritis, over time. Acknowledging the limitations inherent in pathologic classification, the focus shifted to molecular classification to achieve a deeper insight into disease heterogeneity. The study outlined the established methods and findings from the molecular classification of ADs, categorizing systemic lupus erythematosus (SLE) into four subtypes, inflammatory bowel disease (IBD) into two, rheumatoid arthritis (RA) into three, and multiple sclerosis (MS) into a single subtype. It was observed that the high inflammation subtype of IBD, the RA inflammation subtype, and the MS "inflammation & EGF" subtype share similarities. These subtypes all display a consistent pattern of inflammation that is primarily driven by the activation of the JAK-STAT pathway, with the effective drugs being those that target this signaling pathway. Additionally, by identifying markers that are uniquely associated with the various subtypes within the same disease, the study was able to describe the differences between subtypes in detail. The findings are expected to contribute to the development of personalized treatment plans for patients and establish a strong basis for tailored approaches to treating autoimmune diseases.

Spatially resolved gene signatures of white matter lesion progression in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system characterized by myelin loss and progressive neurodegeneration. To understand MS lesion initiation and progression, we generate spatial gene expression maps of white matter (WM) and grey matter (GM) MS lesions. In different MS lesion types, we detect domains characterized by a distinct gene signature, including an identifiable rim around active WM lesions. Expression changes in astrocyte-specific, oligodendrocyte-specific and microglia-specific gene sets characterize the active lesion rims. Furthermore, we identify three WM lesion progression trajectories, predicting how normal-appearing WM can develop into WM active or mixed active-inactive lesions. Our data shed light on the dynamic progression of MS lesions.

Imaging Outcomes for Phase 2 Trials Targeting Compartmentalized Inflammation

This comprehensive review aims to explore imaging outcome measures targeting compartmentalized inflammation in Phase 2 clinical trials for multiple sclerosis (MS). The traditional primary imaging outcomes used in Phase 2 MS trials, new or enhancing white matter lesions on MRI, target the effects of peripheral inflammation, but the widespread inflammation behind a mostly closed blood-brain barrier is not captured. This review discusses several emerging imaging technologies that could be used as surrogate markers of compartmentalized inflammation, targeting chronic active lesions, meningeal inflammation, and innate immune activation within the normal-appearing white matter and gray matter. The integration of specific imaging outcomes into Phase 2 trials can provide a more accurate assessment of treatment efficacy, ultimately contributing to the development of more effective therapies for MS.

Phenotyping in vivo chronic inflammation in multiple sclerosis by combined 11C-PBR28 MR-PET and 7T susceptibility-weighted imaging

BACKGROUND

11C-PBR28 positron emission tomography (PET), targeting the translocator protein, and paramagnetic rim lesions (PRL) have emerged as promising imaging markers of MS chronic inflammation. No consensus on which is the optimal marker exists.

OBJECTIVES

To investigate the ability of 11C-PBR28 PET and PRL assessment to identify chronic inflammation in white matter (WM) MS lesions and their relation to neurological impairment.

METHODS

Based on 11C-PBR28 uptake, brain WM lesions from 30 MS patients were classified as PET active or inactive. The PRL presence was assessed on 7T phase reconstructions, T1/T2 ratio was calculated to measure WM microstructural integrity.

RESULTS

Less than half (44%) of non-PRL WM lesions were active on 11C-PBR28 imaging either throughout the lesion (whole active) or at its periphery. PET peripherally active lesions and PRL did not differ in T1/T2 ratio and 11C-PBR28 uptake. A positive correlation was observed between PRL and active PET lesion count. Whole active PET lesion volume was the strongest predictor (β = 0.97, p < 0.001) of increased Expanded Disability Status Scale scores.

CONCLUSION

11C-PBR28 imaging reveals more active WM lesions than 7T PRL assessment. Although PRL and PET active lesion counts are related, neurological disability is better explained by PET whole active lesion volume.

Spinal cord evaluation in multiple sclerosis: clinical and radiological associations, present and future

Spinal cord disease is important in most people with multiple sclerosis, but assessment remains less emphasized in patient care, basic and clinical research and therapeutic trials. The North American Imaging in Multiple Sclerosis Spinal Cord Interest Group was formed to determine and present the contemporary landscape of multiple sclerosis spinal cord evaluation, further existing and advanced spinal cord imaging techniques, and foster collaborative work. Important themes arose: (i) multiple sclerosis spinal cord lesions (differential diagnosis, association with clinical course); (ii) spinal cord radiological-pathological associations; (iii) 'critical' spinal cord lesions; (iv) multiple sclerosis topographical model; (v) spinal cord atrophy; and (vi) automated and special imaging techniques. Distinguishing multiple sclerosis from other myelopathic aetiology is increasingly refined by imaging and serological studies. Post-mortem spinal cord findings and MRI pathological correlative studies demonstrate MRI's high sensitivity in detecting microstructural demyelination and axonal loss. Spinal leptomeninges include immune inflammatory infiltrates, some in B-cell lymphoid-like structures. 'Critical' demyelinating lesions along spinal cord corticospinal tracts are anatomically consistent with and may be disproportionately associated with motor progression. Multiple sclerosis topographical model implicates the spinal cord as an area where threshold impairment associates with multiple sclerosis disability. Progressive spinal cord atrophy and 'silent' multiple sclerosis progression may be emerging as an important multiple sclerosis prognostic biomarker. Manual atrophy assessment is complicated by rater bias, while automation (e.g. Spinal Cord Toolbox), and artificial intelligence may reduce this. Collaborative research by the North American Imaging in Multiple Sclerosis and similar groups with experts combining distinct strengths is key to advancing assessment and treatment of people with multiple sclerosis spinal cord disease.

The ageing central nervous system in multiple sclerosis: the imaging perspective

The interaction between ageing and multiple sclerosis is complex and carries significant implications for patient care. Managing multiple sclerosis effectively requires an understanding of how ageing and multiple sclerosis impact brain structure and function. Ageing inherently induces brain changes, including reduced plasticity, diminished grey matter volume, and ischaemic lesion accumulation. When combined with multiple sclerosis pathology, these age-related alterations may worsen clinical disability. Ageing may also influence the response of multiple sclerosis patients to therapies and/or their side effects, highlighting the importance of adjusted treatment considerations. MRI is highly sensitive to age- and multiple sclerosis-related processes. Accordingly, MRI can provide insights into the relationship between ageing and multiple sclerosis, enabling a better understanding of their pathophysiological interplay and informing treatment selection. This review summarizes current knowledge on the immunopathological and MRI aspects of ageing in the CNS in the context of multiple sclerosis. Starting from immunosenescence, ageing-related pathological mechanisms and specific features like enlarged Virchow-Robin spaces, this review then explores clinical aspects, including late-onset multiple sclerosis, the influence of age on diagnostic criteria, and comorbidity effects on imaging features. The role of MRI in understanding neurodegeneration, iron dynamics and myelin changes influenced by ageing and how MRI can contribute to defining treatment effects in ageing multiple sclerosis patients, are also discussed.

Towards Treating Multiple Sclerosis Progression

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system (CNS). In most patients, the disease starts with an acute onset followed by a remission phase, subsequent relapses and a later transition to steady chronic progression. In a minority of patients, this progressive phase develops from the beginning. MS relapses are characterized predominantly by the de novo formation of an inflammatory CNS lesion and the infiltration of immune cells, whereas the pathological features of MS progression include slowly expanding lesions, global brain atrophy and an inflammatory response predominantly mediated by macrophages/microglia. Importantly, this CNS-intrinsic pathophysiology appears to initiate early during the relapsing-remitting disease phase, while it turns into the key clinical MS feature in later stages. Currently approved disease-modifying treatments for MS are effective in modulating peripheral immunity by dampening immune cell activity or preventing the migration of immune cells into the CNS, resulting in the prevention of relapses; however, they show limited success in halting MS progression. In this manuscript, we first describe the pathological mechanisms of MS and summarize the approved therapeutics for MS progression. We also review the treatment options for progressive MS (PMS) that are currently under investigation. Finally, we discuss potential targets for novel treatment strategies in PMS.

Chronic active lesions preferentially localize in watershed territories in multiple sclerosis

OBJECTIVE

Paramagnetic rim lesions (PRLs) are a biomarker of chronic active lesions (CALs), and an important driver of neurological disability in multiple sclerosis (MS). The reason subtending some acute lesions evolvement into CALs is not known. Here we ask whether a relatively lower oxygen content is linked to CALs.

METHODS

In this prospective cross-sectional study, 64 people with multiple sclerosis (PwMS), clinically isolated syndrome and radiologically isolated syndrome underwent a 7.0 Tesla (7 T) brain magnetic resonance imaging (MRI). The scanning protocol included a T2-w fluid-attenuated inversion recovery (FLAIR), and a single echo gradient echo from which susceptibility-weighted imaging (SWI) was derived. WM lesions were identified on the T2-w-FLAIR whilst PRLs were identified on the SWI sequence. T2-lesions were classified as PRLs and rimless lesions (PRLs-). We registered a universal vascular atlas to each subject's T2-w-FLAIR and classified each T2-lesions according to its location into watershed- (ws), non-watershed- (nws), and mixed-lesion (m). Ws-lesions were defined as lesions that were fully located in a region between the territories of two major arteries.

RESULTS

Out of 1,975 T2-lesions, 88 (4.5%) were PRLs. Ws-regions had a higher number (p = 0.005) and proportion (p < 0.001) of PRLs- compared to nws-regions. Ws-PRL- were larger compared to nws-ones (p = 0.009). The number (p = 0.043) and proportion (p < 0.001) of PRLs was higher in ws-regions compared to nws-ones. Ws-PRLs were not significantly larger than nws-ones (p = 0.195).

INTERPRETATION

We propose the novel concept of a link between arterial vascularization and chronic activity in MS by demonstrating a preferential localization of CALs in ws-territories.

Slowly expanding lesions are associated with disease activity and gray matter loss in relapse-onset multiple sclerosis

BACKGROUND AND PURPOSE

Slowly expanding lesions (SELs) have been proposed as novel MRI markers of chronic active lesions in multiple sclerosis (MS). However, the mechanism through which SELs affect brain volume loss in patients with MS remains unknown. Additionally, the prevalence and significance of SELs in Asian patients with MS remain unclear. This study aimed to investigate the association between SELs and no evidence of disease activity (NEDA)-3 status as well as brain volume loss in Japanese patients.

METHODS

A total of 99 patients with relapse-onset MS were retrospectively evaluated. SELs were identified on brain MRI based on local deformation when consecutive scans were registered longitudinally. We developed a logistic regression model and generalized linear mixed models (GLMMs) to evaluate the association between the number of SELs and disease activity and changes in brain volume.

RESULTS

During the observation period (2.0 ± 0.22 years), 35 patients developed at least one SEL. Multivariable logistic regression analysis showed that ≥2 SELs were associated with 0.2 times the risk of achieving a NEDA-3 status. GLMMs revealed that the number of SELs was negatively associated with volume changes in the cortex (p = .00169) and subcortical gray matter (p = .00964) after correction for multiple comparisons.

CONCLUSION

SELs were identified in Japanese patients with MS during the 2-year observation period. The number of SELs is associated with disease activity and brain volume loss, suggesting that the number of SELs could be a biomarker of disease activity in MS.

Neurofilaments light chains as a diagnostic and predictive biomarker for Tunisian Multiple Sclerosis patients

BACKGROUND

Multiple Sclerosis (MS) course was shown to be more severe among North Africans compared to Caucasians. Validation of prognostic biomarkers of disease activity and severity is a priority in our practice.

OBJECTIVE

We aimed to investigate the association between baseline cerebrospinal fluid (CSF) and serum NfL (sNFL) levels and disease activity and disability accrual in a cohort of Tunisian patients with MS.

METHODS

A cross-sectional study was conducted, in the department of Neurology of Razi Hospital, including patients diagnosed with MS. Patient's data were retrieved from our local MS database. Blood and CSF sampling were performed at the first visit. sNFL levels were measured using the Enzyme-Linked Immuno-Sorbent Assay (ELISA) sandwich technique.

RESULTS

Three hundred MS patients were enrolled (sex-ratio= 3.05; mean age at MS onset=28.83 years+9.55, mean MS course = 10.21 years+8.96). MS phenotype was predominately relapsing (73%). CSF NfL levels were significantly correlated to the serum ones. NfL concentrations were significantly associated with MS activity (p = 0.012), disease progression (p = 0.001), and higher Multiple Sclerosis Severity Scores (MSSS) (p = 0.0017, r = 0.28).

CONCLUSIONS

These results support the value of NfL as a sensitive and clinically meaningful CSF and blood biomarker to evaluate MS activity and outcomes among Tunisian MS patients.

Smouldering-Associated Worsening in Multiple Sclerosis: An International Consensus Statement on Definition, Biology, Clinical Implications, and Future Directions

Despite therapeutic suppression of relapses, multiple sclerosis (MS) patients often experience subtle deterioration, which extends beyond the definition of "progression independent of relapsing activity." We propose the concept of smouldering-associated-worsening (SAW), encompassing physical and cognitive symptoms, resulting from smouldering pathological processes, which remain unmet therapeutic targets. We provide a consensus-based framework of possible pathological substrates and manifestations of smouldering MS, and we discuss clinical, radiological, and serum/cerebrospinal fluid biomarkers for potentially monitoring SAW. Finally, we share considerations for optimizing disease surveillance and implications for clinical trials to promote the integration of smouldering MS into routine practice and future research efforts. ANN NEUROL 2024;96:826-845.

Intrathecal IgG and IgM synthesis correlates with neurodegeneration markers and corresponds to meningeal B cell presence in MS

Intrathecal synthesis of immunoglobulins (Igs) is a key hallmark of multiple sclerosis (MS). B cells are known to accumulate in the leptomeninges of MS patients and associate with pathology in the underlying cortex and a more severe disease course. However, the role of locally produced antibodies in MS brain pathology is poorly understood. Here, we quantified the protein levels of IgA, IgM, IgG and albumin in serum and cerebrospinal fluid (CSF) samples of 80 MS patients and 28 neurological controls to calculate Ig indices. In addition, we quantified presence of meningeal IgA+, IgM+ and IgG+ B cells in post-mortem brain tissue of 20 MS patients and 6 controls using immunostainings. IgM and IgG, but not IgA, indices were increased in CSF of MS patients compared to controls, with no observed differences between MS disease types. Both IgM and IgG indices correlated significantly with neurofilament light (NfL) levels in CSF, but not with clinical or radiological parameters of disease. Similarly, IgG+ and IgM+ B cells were increased in MS meninges compared to controls, whereas IgA+ B cells were not. Neuronal loss did not differ between sections with low or high IgA+, IgM+ and IgG+ B cells, but was increased in sections with high numbers of all CD19+ meningeal B cells. Similarly, high presence of CD19+ meningeal B cells and IgG+ meningeal B cells associated with increased microglial density in the underlying cortex. Taken together, intrathecal synthesis of IgG and IgM is elevated in MS, which corresponds to an increased number of IgG+ and IgM+ B cells in MS meninges. The significant correlation between intrathecal IgG and IgM production and NfL levels, and increased microglial activation in cortical areas adjacent to meningeal infiltrates with high levels of IgG+ B cells indicate a role for intrathecal IgM- and IgG-producing B cells in neuroinflammatory and degenerative processes in MS.

Neurodegeneration and demyelination in multiple sclerosis

Progressive multiple sclerosis (PMS) is an immune-initiated neurodegenerative condition that lacks effective therapies. Although peripheral immune infiltration is a hallmark of relapsing-remitting MS (RRMS), PMS is associated with chronic, tissue-restricted inflammation and disease-associated reactive glial states. The effector functions of disease-associated microglia, astrocytes, and oligodendrocyte lineage cells are beginning to be defined, and recent studies have made significant progress in uncovering their pathologic implications. In this review, we discuss the immune-glia interactions that underlie demyelination, failed remyelination, and neurodegeneration with a focus on PMS. We highlight the common and divergent immune mechanisms by which glial cells acquire disease-associated phenotypes. Finally, we discuss recent advances that have revealed promising novel therapeutic targets for the treatment of PMS and other neurodegenerative diseases.

Predicting multiple sclerosis disease progression and outcomes with machine learning and MRI-based biomarkers: a review

Multiple sclerosis (MS) is a demyelinating neurological disorder with a highly heterogeneous clinical presentation and course of progression. Disease-modifying therapies are the only available treatment, as there is no known cure for the disease. Careful selection of suitable therapies is necessary, as they can be accompanied by serious risks and adverse effects such as infection. Magnetic resonance imaging (MRI) plays a central role in the diagnosis and management of MS, though MRI lesions have displayed only moderate associations with MS clinical outcomes, known as the clinico-radiological paradox. With the advent of machine learning (ML) in healthcare, the predictive power of MRI can be improved by leveraging both traditional and advanced ML algorithms capable of analyzing increasingly complex patterns within neuroimaging data. The purpose of this review was to examine the application of MRI-based ML for prediction of MS disease progression. Studies were divided into five main categories: predicting the conversion of clinically isolated syndrome to MS, cognitive outcome, EDSS-related disability, motor disability and disease activity. The performance of ML models is discussed along with highlighting the influential MRI-derived biomarkers. Overall, MRI-based ML presents a promising avenue for MS prognosis. However, integration of imaging biomarkers with other multimodal patient data shows great potential for advancing personalized healthcare approaches in MS.

The Therapeutic Potential of Exosomes from Mesenchymal Stem Cells in Multiple Sclerosis

Although treatment for multiple sclerosis (MS) has undergone a revolution in the last decades, at least two important barriers remain: alleviation of innate inflammation driving disease progression and promotion of remyelination and neural regeneration. Mesenchymal stem cells (MSCs) possess immunomodulatory properties and promote remyelination in murine MS models. The main therapeutic mechanism has, however, been attributed to their potent paracrine capacity, and not to in vivo tissue implantation. Studies have demonstrated that exosomes released as part of the cells' secretome effectively encapsulate the beneficial properties of MSCs. These membrane-enclosed nanoparticles contain a variety of proteins and nucleic acids and serve as mediators of intercellular communication. In vitro studies have demonstrated that exosomes from MSCs modulate activated microglia from an inflammatory to an anti-inflammatory phenotype and thereby dampen the innate inflammation. Rodent studies have also demonstrated potent immunomodulation and remyelination with improved outcomes following exosome administration. Thus, exosomes from MSCs may represent a potential cell-free treatment modality to prevent disease progression and promote remyelination in MS. In this narrative review, we summarize the current knowledge of exosomes from MSCs as a potential treatment for MS and discuss the remaining issues before successful translation into clinical trials.

Niacin produces an inconsistent treatment response in the EAE model of multiple sclerosis

Niacin was found in the lysolecithin model of multiple sclerosis (MS) to promote the phagocytic clearance of debris and enhance remyelination. Lysolecithin lesions have prominent microglia/macrophages but lack lymphocytes that populate plaques of MS or its experimental autoimmune encephalomyelitis (EAE) model. Thus, the current study assessed the efficacy of niacin in EAE. We found that niacin inconsistently affects EAE clinical score, and largely does not ameliorate neuropathology. In culture, niacin enhances phagocytosis by macrophages, but does not reduce T cell proliferation. We suggest that studies of niacin for potential remyelination in MS should include a therapeutic that targets adaptive immunity.

Imaging chronic active lesions in multiple sclerosis: a consensus statement

Chronic active lesions (CAL) are an important manifestation of chronic inflammation in multiple sclerosis and have implications for non-relapsing biological progression. In recent years, the discovery of innovative MRI and PET-derived biomarkers has made it possible to detect CAL, and to some extent quantify them, in the brain of persons with multiple sclerosis, in vivo. Paramagnetic rim lesions on susceptibility-sensitive MRI sequences, MRI-defined slowly expanding lesions on T1-weighted and T2-weighted scans, and 18-kDa translocator protein-positive lesions on PET are promising candidate biomarkers of CAL. While partially overlapping, these biomarkers do not have equivalent sensitivity and specificity to histopathological CAL. Standardization in the use of available imaging measures for CAL identification, quantification and monitoring is lacking. To fast-forward clinical translation of CAL, the North American Imaging in Multiple Sclerosis Cooperative developed a consensus statement, which provides guidance for the radiological definition and measurement of CAL. The proposed manuscript presents this consensus statement, summarizes the multistep process leading to it, and identifies the remaining major gaps in knowledge.

The contribution of tumor necrosis factor to multiple sclerosis: a possible role in progression independent of relapse?

Tumor necrosis factor (TNF) is a pleiotropic cytokine regulating many physiological and pathological immune-mediated processes. Specifically, it has been recognized as an essential pro-inflammatory cytokine implicated in multiple sclerosis (MS) pathogenesis and progression. MS is a chronic immune-mediated disease of the central nervous system, characterized by multifocal acute and chronic inflammatory demyelination in white and grey matter, along with neuroaxonal loss. A recent concept in the field of MS research is disability resulting from Progression Independent of Relapse Activity (PIRA). PIRA recognizes that disability accumulation since the early phase of the disease can occur independently of relapse activity overcoming the traditional dualistic view of MS as either a relapsing-inflammatory or a progressive-neurodegenerative disease. Several studies have demonstrated an upregulation in TNF expression in both acute and chronic active MS brain lesions. Additionally, elevated TNF levels have been observed in the serum and cerebrospinal fluid of MS patients. TNF appears to play a significant role in maintaining chronic intrathecal inflammation, promoting axonal damage neurodegeneration, and consequently contributing to disease progression and disability accumulation. In summary, this review highlights the current understanding of TNF and its receptors in MS progression, specifically focusing on the relatively unexplored PIRA condition. Further research in this area holds promise for potential therapeutic interventions targeting TNF to mitigate disability in MS patients.

Cortical CD200-CD200R and CD47-SIRPα expression is associated with multiple sclerosis pathology

Control of microglia activity through CD200-CD200R and CD47-SIRPα interactions has been implicated in brain homeostasis. Here, we assessed CD200, CD47, CD200R and SIRPα expression with qPCR and immunohistochemistry in multiple sclerosis (MS) normal-appearing cortical grey matter (NAGM), normal-appearing white matter (NAWM), cortical grey matter (GM) lesions and perilesional GM, and compared this to control GM and white matter (WM), to investigate possible altered control of microglia in MS. In MS NAGM, CD200 expression is lower compared with control GM, specifically in cortical layers 1 and 2, and CD200 expression in NAGM negatively correlates with the cortical lesion rate. Interestingly, NAGM and NAWM CD200 expression is positively correlated, and NAGM CD200 expression negatively correlates with the proportion of active and mixed WM lesions. In GM lesions, CD200 and CD47 expressions are lower compared with NAGM and perilesional GM. CD200R expression is lower in MS NAGM, whereas SIRPα was increased in and around GM lesions. Taken together, our data indicate that CD200 and CD47 play a role in GM MS lesion formation and progression, respectively, and that targeting CD200 pathways may offer therapeutic avenues to mitigate MS pathology in both WM and GM.

Targeting the muscarinic M1 receptor with a selective, brain-penetrant antagonist to promote remyelination in multiple sclerosis

Multiple sclerosis (MS) is a chronic and debilitating neurological disease that results in inflammatory demyelination. While endogenous remyelination helps to recover function, this restorative process tends to become less efficient over time. Currently, intense efforts aimed at the mechanisms that promote remyelination are being considered promising therapeutic approaches. The M1 muscarinic acetylcholine receptor (M1R) was previously identified as a negative regulator of oligodendrocyte differentiation and myelination. Here, we validate M1R as a target for remyelination by characterizing expression in human and rodent oligodendroglial cells (including those in human MS tissue) using a highly selective M1R probe. As a breakthrough to conventional methodology, we conjugated a fluorophore to a highly M1R selective peptide (MT7) which targets the M1R in the subnanomolar range. This allows for exceptional detection of M1R protein expression in the human CNS. More importantly, we introduce PIPE-307, a brain-penetrant, small-molecule antagonist with favorable drug-like properties that selectively targets M1R. We evaluate PIPE-307 in a series of in vitro and in vivo studies to characterize potency and selectivity for M1R over M2-5R and confirm the sufficiency of blocking this receptor to promote differentiation and remyelination. Further, PIPE-307 displays significant efficacy in the mouse experimental autoimmune encephalomyelitis model of MS as evaluated by quantifying disability, histology, electron microscopy, and visual evoked potentials. Together, these findings support targeting M1R for remyelination and support further development of PIPE-307 for clinical studies.

Determinants and Biomarkers of Progression Independent of Relapses in Multiple Sclerosis

Clinical, pathological, and imaging evidence in multiple sclerosis (MS) suggests that a smoldering inflammatory activity is present from the earliest stages of the disease and underlies the progression of disability, which proceeds relentlessly and independently of clinical and radiological relapses (PIRA). The complex system of pathological events driving "chronic" worsening is likely linked with the early accumulation of compartmentalized inflammation within the central nervous system as well as insufficient repair phenomena and mitochondrial failure. These mechanisms are partially lesion-independent and differ from those causing clinical relapses and the formation of new focal demyelinating lesions; they lead to neuroaxonal dysfunction and death, myelin loss, glia alterations, and finally, a neuronal network dysfunction outweighing central nervous system (CNS) compensatory mechanisms. This review aims to provide an overview of the state of the art of neuropathological, immunological, and imaging knowledge about the mechanisms underlying the smoldering disease activity, focusing on possible early biomarkers and their translation into clinical practice. ANN NEUROL 2024;96:1-20.

Associations between diet and disease progression and symptomatology in multiple sclerosis: A systematic review of observational studies

BACKGROUND

Although many people with MS (pwMS) modify their diet after diagnosis, there is still no consensus on dietary recommendations for pwMS. A number of observational studies have explored associations of diet and MS progression, but no studies have systematically reviewed the evidence. This systematic review aimed to provide an objective synthesis of the evidence for associations between diet and MS progression, including symptoms and clinical outcomes from observational studies.

METHODS

We performed a systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Electronic database searches were performed for studies completed up to 26 July 2023 using PubMed (Medline), Web of Science, CINAHL, Embase (Ovid), and Scopus, followed by citation and reference list checking. We included studies using diet quality scores or dietary indices. Studies assessing individual foods, nutrients, or dietary supplements were excluded. We used the Newcastle-Ottawa Scale to assess the risk of bias of included studies.

RESULTS

Thirty-two studies met the inclusion criteria. Of these, 20 were cross-sectional and 12 prospective. The most frequent outcomes assessed were disability (n = 19), quality of life (n = 12), fatigue (n = 12), depression (n = 9), relapse (n = 8), anxiety (n = 3), and magnetic resonance imaging (MRI) outcomes (n = 4). Based on prospective studies, this review suggests that diet might be associated with quality of life and disability. There were also potential effects of higher diet quality scores on improved fatigue, disability, depression, anxiety, and MRI outcomes but more evidence is needed from prospective studies.

CONCLUSIONS

Observational studies show some evidence for an association between diet and MS symptoms, particularly quality of life and disability. However, the impact of diet on other MS outcomes remains inconclusive. Ultimately, our findings suggest more evidence is needed from prospective studies and well-designed tailored intervention studies to confirm associations.

Longitudinal myelin content measures of slowly expanding lesions using 7T MRI in multiple sclerosis

BACKGROUND AND PURPOSE

Slowly expanding lesions (SELs) are thought to represent a subset of chronic active lesions and have been associated with clinical disability, severity, and disease progression. The purpose of this study was to characterize SELs using advanced magnetic resonance imaging (MRI) measures related to myelin and neurite density on 7 Tesla (T) MRI.

METHODS

The study design was retrospective, longitudinal, observational cohort with multiple sclerosis (n = 15). Magnetom 7T scanner was used to acquire magnetization-prepared 2 rapid acquisition gradient echo and advanced MRI including visualization of short transverse relaxation time component (ViSTa) for myelin, quantitative magnetization transfer (qMT) for myelin, and neurite orientation dispersion density imaging (NODDI). SELs were defined as lesions showing ≥12% of growth over 12 months on serial MRI. Comparisons of quantitative measures in SELs and non-SELs were performed at baseline and over time. Statistical analyses included two-sample t-test, analysis of variance, and mixed-effects linear model for MRI metrics between lesion types.

RESULTS

A total of 1075 lesions were evaluated. Two hundred twenty-four lesions (21%) were SELs, and 216 (96%) of the SELs were black holes. At baseline, compared to non-SELs, SELs showed significantly lower ViSTa (1.38 vs. 1.53, p < .001) and qMT (2.47 vs. 2.97, p < .001) but not in NODDI measures (p > .27). Longitudinally, only ViSTa showed a greater loss when comparing SEL and non-SEL (p = .03).

CONCLUSIONS

SELs have a lower myelin content relative to non-SELs without a difference in neurite measures. SELs showed a longitudinal decrease in apparent myelin water fraction reflecting greater tissue injury.

Imaging phenotypic differences in multiple sclerosis: at the crossroads of aging, sex, race, and ethnicity

Clear sex differences are observed in clinical and imaging phenotypes of multiple sclerosis (MS), which evolve significantly over the age spectrum, and more specifically, during reproductive milestones such as pregnancy and menopause. With neuroimaging being an outcome measure and also a key subclinical biomarker of subsequent clinical phenotype in MS, this comprehensive review aims to provide an overview of sex and hormone differences in structural and functional imaging biomarkers of MS, including lesion burden and location, atrophy, white matter integrity, functional connectivity, and iron distribution. Furthermore, how therapies aimed at altering sex hormones can impact imaging of women and men with MS over the lifespan is discussed. This review also explores the key intersection between age, sex, and race/ethnicity in MS, and how this intersection may affect imaging biomarkers of MS.

Central Vein Sign and Paramagnetic Rim Lesions: Susceptibility Changes in Brain Tissues and Their Implications for the Study of Multiple Sclerosis Pathology

Multiple sclerosis (MS) is the most common acquired inflammatory and demyelinating disease in adults. The conventional diagnostic of MS and the follow-up of inflammatory activity is based on the detection of hyperintense foci in T2 and fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) and lesions with brain-blood barrier (BBB) disruption in the central nervous system (CNS) parenchyma. However, T2/FLAIR hyperintense lesions are not specific to MS and the MS pathology and inflammatory processes go far beyond focal lesions and can be independent of BBB disruption. MRI techniques based on the magnetic susceptibility properties of the tissue, such as T2*, susceptibility-weighted images (SWI), and quantitative susceptibility mapping (QSM) offer tools for advanced MS diagnostic, follow-up, and the assessment of more detailed features of MS dynamic pathology. Susceptibility-weighted techniques are sensitive to the paramagnetic components of biological tissues, such as deoxyhemoglobin. This capability enables the visualization of brain parenchymal veins. Consequently, it presents an opportunity to identify veins within the core of multiple sclerosis (MS) lesions, thereby affirming their venocentric characteristics. This advancement significantly enhances the accuracy of the differential diagnostic process. Another important paramagnetic component in biological tissues is iron. In MS, the dynamic trafficking of iron between different cells, such as oligodendrocytes, astrocytes, and microglia, enables the study of different stages of demyelination and remyelination. Furthermore, the accumulation of iron in activated microglia serves as an indicator of latent inflammatory activity in chronic MS lesions, termed paramagnetic rim lesions (PRLs). PRLs have been correlated with disease progression and degenerative processes, underscoring their significance in MS pathology. This review will elucidate the underlying physical principles of magnetic susceptibility and their implications for the formation and interpretation of T2*, SWI, and QSM sequences. Additionally, it will explore their applications in multiple sclerosis (MS), particularly in detecting the central vein sign (CVS) and PRLs, and assessing iron metabolism. Furthermore, the review will discuss their role in advancing early and precise MS diagnosis and prognostic evaluation, as well as their utility in studying chronic active inflammation and degenerative processes.

Digital Pathology Identifies Associations between Tissue Inflammatory Biomarkers and Multiple Sclerosis Outcomes

BACKGROUND

Multiple sclerosis (MS) is a clinically heterogeneous disease underpinned by inflammatory, demyelinating and neurodegenerative processes, the extent of which varies between individuals and over the course of the disease. Recognising the clinicopathological features that most strongly associate with disease outcomes will inform future efforts at patient phenotyping.

AIMS

We used a digital pathology workflow, involving high-resolution image acquisition of immunostained slides and opensource software for quantification, to investigate the relationship between clinical and neuropathological features in an autopsy cohort of progressive MS.

METHODS

Sequential sections of frontal, cingulate and occipital cortex, thalamus, brain stem (pons) and cerebellum including dentate nucleus (n = 35 progressive MS, females = 28, males = 7; age died = 53.5 years; range 38-98 years) were immunostained for myelin (anti-MOG), neurons (anti-HuC/D) and microglia/macrophages (anti-HLA). The extent of demyelination, neurodegeneration, the presence of active and/or chronic active lesions and quantification of brain and leptomeningeal inflammation was captured by digital pathology.

RESULTS

Digital analysis of tissue sections revealed the variable extent of pathology that characterises progressive MS. Microglia/macrophage activation, if found at a higher level in a single block, was typically elevated across all sampled blocks. Compartmentalised (perivascular/leptomeningeal) inflammation was associated with age-related measures of disease severity and an earlier death.

CONCLUSION

Digital pathology identified prognostically important clinicopathological correlations in MS. This methodology can be used to prioritise the principal pathological processes that need to be captured by future MS biomarkers.

Alemtuzumab treatment for multiple sclerosis in Austria: An observational long-term outcome study

BACKGROUND/OBJECTIVE

Observational real-world study to analyze the clinical effects of alemtuzumab (ALEM) and subsequent disease-modifying therapy (DMT) usage in multiple sclerosis (MS).

METHODS

Data retrieved from the Austrian MS treatment registry (AMSTR) included baseline (BL) characteristics (at ALEM start), annualized relapse rate (ARR), 6-month confirmed progression independent of relapse activity (PIRA; ≥ 0.5-point Expanded Disability Status Scale (EDSS) score increase), 6-month confirmed disability improvement (CDI; ≥ 0.5-point EDSS decrease), and safety outcomes until initiation of a subsequent DMT. The EDSS was re-baselined at 30 days from ALEM start (BL EDSS).

RESULTS

Eighty-seven ALEM-treated patients (median age: 32 years, 72% female, 14% treatment-naïve) were followed for a median of 55 (interquartile range 31-68) months. We found significant reductions in the ARR from 1.16 before ALEM to 0.15 throughout Years 1-9 (p < 0.001). Subsequent DMTs were initiated in 19 patients (22%, 74% anti-CD20 monoclonal antibodies). At Year 5 (n = 53), more patients achieved CDI (58%, 95% confidence interval (CI) 45%-71%) than had experienced PIRA (14%, CI 7.5%-24%), and 58% remained relapse-free. Shorter MS duration (p < 0.001, hazard ratio (HR) 0.86 (CI 0.80-0.93)) and no previous high-efficacy treatment (p < 0.001, HR 5.16 (CI 2.66-10.0)) were the best predictors of CDI, while PIRA was associated with a higher number of previous DMTs (p = 0.04, HR 3.06, CI 1.05-8.89). We found no new safety signals.

INTERPRETATION

ALEM had long-lasting beneficial effects on the ARR and disability improvement, especially when initiated early in the course of the disease. Only a subset of patients received subsequent DMTs.