Contribution of B cells to cortical damage in multiple sclerosis

In vivo evidence for cell body loss in cortical lesions in people with multiple sclerosis

OBJECTIVE

To quantify alterations in soma and neurite density imaging measures within and surrounding cortical lesions in people with multiple sclerosis using in vivo high-gradient diffusion MRI.

METHODS

In this cross-sectional study, 41 people with multiple sclerosis and 34 age- and sex-matched healthy controls underwent 3 T high-gradient diffusion MRI. Cortical lesions were segmented on artificial intelligence-enabled double inversion recovery images. "Inner" and "outer" perilesional layers were segmented as two expanding shells of 2 mm surrounding a cortical lesion. Intracellular, intra-neurite, and extracellular signal fractions and apparent soma radius were estimated in (peri)lesional and normal-appearing cortex.

RESULTS

Cortical lesions were present in all people with multiple sclerosis with a median count of 8 [IQR 5-18] and total volume of 0.16 [0.09-0.46 mL]. People with multiple sclerosis (mean 0.27 ± 0.03) showed lower normalized cortical volumes compared to healthy controls (0.30 ± 0.02). Compared to healthy controls (mean 0.58 ± 0.028), normal-appearing cortex in multiple sclerosis (0.57 ± 0.034) showed lower intra-cellular signal fraction. Cortical lesions (0.49 ± 0.089) exhibited lower intra-cellular signal fractions compared to perilesional ("inner": 0.55 ± 0.049, "outer": 0.55 ± 0.039) and normal-appearing cortex, demonstrating a gradation of change. The soma radius varied significantly across cortices, becoming smaller when moving outward from cortical lesions (cortical lesions: 10.38 ± 0.209 μm, "inner" layer: 10.19 ± 0.140 μm, "outer" layer: 10.07 ± 0.149 μm, normal-appearing cortex: 9.99 ± 0.127 μm).

INTERPRETATION

Cortical cell body loss in multiple sclerosis is most pronounced in cortical lesions and also present in normal-appearing cortex. Gradients of diffusion microstructural alterations moving outward from cortical lesions toward normal-appearing cortex highlight the potential of high-gradient diffusion MRI to identify both focal and diffuse cortical pathology.

Spatial transcriptomics of meningeal inflammation reveals inflammatory gene signatures in adjacent brain parenchyma

While modern high efficacy disease modifying therapies have revolutionized the treatment of relapsing-remitting multiple sclerosis, they are less effective at controlling progressive forms of the disease. Meningeal inflammation is a recognized risk factor for cortical gray matter pathology which can result in disabling symptoms such as cognitive impairment and depression, but the mechanisms linking meningeal inflammation and gray matter pathology remain unclear. Here, we performed magnetic resonance imaging (MRI)-guided spatial transcriptomics in a mouse model of autoimmune meningeal inflammation to characterize the transcriptional signature in areas of meningeal inflammation and the underlying brain parenchyma. We found broadly increased activity of inflammatory signaling pathways at sites of meningeal inflammation, but only a subset of these pathways active in the adjacent brain parenchyma. Subclustering of regions adjacent to meningeal inflammation revealed the subset of immune programs induced in brain parenchyma, notably complement signaling and antigen processing/presentation. Trajectory gene and gene set modeling analysis confirmed variable penetration of immune signatures originating from meningeal inflammation into the adjacent brain tissue. This work contributes a valuable data resource to the field, provides the first detailed spatial transcriptomic characterization in a model of meningeal inflammation, and highlights several candidate pathways in the pathogenesis of gray matter pathology.

Effects of anti-CD20 therapy on circulating and intrathecal follicular helper T cell subsets in multiple sclerosis

Follicular helper T (Tfh) cells and their interplay with B cells likely contribute to the pathogenesis of relapsing-remitting multiple sclerosis (RRMS). Tfh cells are enriched in cerebrospinal fluid (CSF) in RRMS, but effects of anti-CD20 therapy are unknown. We investigated Tfh cells in controls, untreated and anti-CD20-treated patients with RRMS using flow cytometry. CSF Tfh cells were increased in untreated patients. Compared to paired blood samples, CD25- Tfh cells were enriched in CSF in RRMS, but not in controls. Contrast-enhancing brain MRI lesions and IgG index correlated with CSF CD25- Tfh cell frequency in untreated patients with RRMS. Anti-CD20 therapy reduced the numbers of circulating PD1+ Tfh cells and CD25- Tfh cells, and the frequency of CSF CD25- Tfh cells. The study suggests that CD25- Tfh cells are recruited to the CSF in RRMS, associated with focal inflammation, and are reduced by anti-CD20 therapy.

Prognostic relevance of the C-X-C motif chemokine ligand 13 and interleukin-8 in predicting the transition from clinically isolated syndrome to multiple sclerosis

The initial phase of multiple sclerosis (MS), often known as clinically isolated syndrome (CIS), is a critical period for identifying individuals at high risk of progressing to full-blown MS and initiating timely treatment. In this study, we aimed to evaluate the prognostic value of C-X-C motif chemokine ligand 13 (CXCL13) and interleukin-8 (IL-8) as potential markers for CIS patients' conversion to MS. Our study encompassed patients with CIS, those with relapsing-remitting MS (RRMS), and control subjects, with sample analysis conducted on both cerebrospinal fluid (CSF) and serum. Patients were categorized into four groups: CIS-CIS (no MS development within 2 years), CIS-RRMS (conversion to RRMS within 2 years), RRMS (already diagnosed), and a control group (CG) with noninflammatory central nervous system disorders. Results showed significantly elevated levels of CXCL13 in CSF across all patient groups compared with the CG (p < 0.0001, Kruskal-Wallis test). Although CXCL13 concentrations were slightly higher in the CIS-RRMS group, statistical significance was not reached. Similarly, significantly higher levels of IL-8 were detected in CSF samples from all patient groups compared with the CG (p < 0.0001, Kruskal-Wallis test). Receiver operating characteristic analysis in the CIS-RRMS group identified both CXCL13 (area under receiver operating characteristic curve = .959) and IL-8 (area under receiver operating characteristic curve = .939) in CSF as significant predictors of CIS to RRMS conversion. In conclusion, our study suggests a trend towards elevated CSF IL-8 and CSF CXCL13 levels in CIS patients progressing to RRMS. These findings emphasize the importance of identifying prognostic markers to guide appropriate treatment strategies for individuals in the early stages of MS.

Seroreactivity against lytic, latent and possible cross-reactive EBV antigens appears on average 10 years before MS induced preclinical neuroaxonal damage

BACKGROUND

Multiple sclerosis (MS) and presymptomatic axonal injury appear to develop only after an Epstein-Barr virus (EBV) infection. This association remains to be confirmed across a broad preclinical time range, for lytic and latent EBV seroreactivity, and for potential cross-reacting antigens.

METHODS

We performed a case-control study with 669 individual serum samples obtained before clinical MS onset, identified through cross-linkage with the Swedish MS register. We assayed antibodies against EBV nuclear antigen 1 (EBNA1), viral capsid antigen p18, glycoprotein 350 (gp350), the potential cross-reacting protein anoctamin 2 (ANO2) and the level of sNfL, a marker of axonal injury.

RESULTS

EBNA1 (latency) seroreactivity increased in the pre-MS group, at 15-20 years before clinical MS onset, followed by gp350 (lytic) seroreactivity (p=0.001-0.009), ANO2 seropositivity appeared shortly after EBNA1-seropositivity in 16.7% of pre-MS cases and 10.0% of controls (p=0.001).With an average lag of almost a decade after EBV, sNfL gradually increased, mainly in the increasing subgroup of seropositive pre-MS cases (p=8.10-5 compared with non-MS controls). Seropositive pre-MS cases reached higher sNfL levels than seronegative pre-MS (p=0.038). In the EBNA1-seropositive pre-MS group, ANO2 seropositive cases had 26% higher sNfL level (p=0.0026).

CONCLUSIONS

Seroreactivity against latent and lytic EBV antigens, and in a subset ANO2, was detectable on average a decade before the appearance of a gradually increasing axonal injury occurring in the last decade before the onset of clinical MS. These findings strengthen the hypothesis of latent EBV involvement in the pathogenesis of MS.

White matter paramagnetic rim and non-rim lesions share a periventricular gradient in multiple sclerosis: A 7-T imaging study

BACKGROUND

Paramagnetic rim white matter (WM) lesions (PRL) are thought to be a main driver of non-relapsing multiple sclerosis (MS) progression. It is unknown whether cerebrospinal fluid (CSF)-soluble factors diffusing from the ventricles contribute to PRL formation.

OBJECTIVE

To investigate the distribution of PRL and non-rim brain WM lesions as a function of distance from ventricular CSF, their relationship with cortical lesions, the contribution of lesion phenotype, and localization to neurological disability.

METHODS

Lesion count and volume of PRL, non-rim WM, leukocortical lesion (LCL), and subpial/intracortical lesions were obtained at 7-T. The brain WM was divided into 1-mm-thick concentric rings radiating from the ventricles to extract PRL and non-rim WM lesion volume from each ring.

RESULTS

In total, 61 MS patients with ⩾1 PRL were included in the study. Both PRL and non-rim WM lesion volumes were the highest in the periventricular WM and declined with increasing distance from ventricles. A CSF distance-independent association was found between non-rim WM lesions, PRL, and LCL, but not subpial/intracortical lesions. Periventricular non-rim WM lesion volume was the strongest predictor of neurological disability.

CONCLUSIONS

Non-rim and PRL share a gradient of distribution from the ventricles toward the cortex, suggesting that CSF proximity equally impacts the prevalence of both lesion phenotypes.

Brain perivascular macrophages: current understanding and future prospects

Brain perivascular macrophages are specialized populations of macrophages that reside in the space around cerebral vessels, such as penetrating arteries and venules. With the help of cutting-edge technologies, such as cell fate mapping and single-cell multi-omics, their multifaceted, pivotal roles in phagocytosis, antigen presentation, vascular integrity maintenance and metabolic regulation have more recently been further revealed under physiological conditions. Accumulating evidence also implies that perivascular macrophages are involved in the pathogenesis of neurodegenerative disease, cerebrovascular dysfunction, autoimmune disease, traumatic brain injury and epilepsy. They can act in either protective or detrimental ways depending on the disease course and stage. However, the underlying mechanisms of perivascular macrophages remain largely unknown. Therefore, we highlight potential future directions in research on perivascular macrophages, including the utilization of genetic mice and novel therapeutic strategies that target these unique immune cells for neuroprotective purposes. In conclusion, this review provides a comprehensive update on the current knowledge of brain perivascular macrophages, shedding light on their pivotal roles in central nervous system health and disease.

Bioavailable central nervous system disease-modifying therapies for multiple sclerosis

Disease-modifying therapies for relapsing multiple sclerosis reduce relapse rates by suppressing peripheral immune cells but have limited efficacy in progressive forms of the disease where cells in the central nervous system play a critical role. To our knowledge, alemtuzumab, fumarates (dimethyl, diroximel, and monomethyl), glatiramer acetates, interferons, mitoxantrone, natalizumab, ocrelizumab, ofatumumab, and teriflunomide are either limited to the periphery or insufficiently studied to confirm direct central nervous system effects in participants with multiple sclerosis. In contrast, cladribine and sphingosine 1-phosphate receptor modulators (fingolimod, ozanimod, ponesimod, and siponimod) are central nervous system-penetrant and could have beneficial direct central nervous system properties.

Mechanisms underlying the beneficial effects of physical exercise on multiple sclerosis: focus on immune cells

Multiple sclerosis (MS) is a prevalent neuroimmunological illness that leads to neurological disability in young adults. Although the etiology of MS is heterogeneous, it is well established that aberrant activity of adaptive and innate immune cells plays a crucial role in its pathogenesis. Several immune cell abnormalities have been described in MS and its animal models, including T lymphocytes, B lymphocytes, dendritic cells, neutrophils, microglia/macrophages, and astrocytes, among others. Physical exercise offers a valuable alternative or adjunctive disease-modifying therapy for MS. A growing body of evidence indicates that exercise may reduce the autoimmune responses triggered by immune cells in MS. This is partially accomplished by restricting the infiltration of peripheral immune cells into the central nervous system (CNS) parenchyma, curbing hyperactivation of immune cells, and facilitating a transition in the balance of immune cells from a pro-inflammatory to an anti-inflammatory state. This review provides a succinct overview of the correlation between physical exercise, immune cells, and MS pathology, and highlights the potential benefits of exercise as a strategy for the prevention and treatment of MS.

Inflammation in multiple sclerosis: consequences for remyelination and disease progression

Despite the large number of immunomodulatory or immunosuppressive treatments available to treat relapsing-remitting multiple sclerosis (MS), treatment of the progressive phase of the disease has not yet been achieved. This lack of successful treatment approaches is caused by our poor understanding of the mechanisms driving disease progression. Emerging concepts suggest that a combination of persisting focal and diffuse inflammation within the CNS and a gradual failure of compensatory mechanisms, including remyelination, result in disease progression. Therefore, promotion of remyelination presents a promising intervention approach. However, despite our increasing knowledge regarding the cellular and molecular mechanisms regulating remyelination in animal models, therapeutic increases in remyelination remain an unmet need in MS, which suggests that mechanisms of remyelination and remyelination failure differ fundamentally between humans and demyelinating animal models. New and emerging technologies now allow us to investigate the cellular and molecular mechanisms underlying remyelination failure in human tissue samples in an unprecedented way. The aim of this Review is to summarize our current knowledge regarding mechanisms of remyelination and remyelination failure in MS and in animal models of the disease, identify open questions, challenge existing concepts, and discuss strategies to overcome the translational roadblock in the field of remyelination-promoting therapies.

Icariin ameliorates behavioral deficits and neuropathology in a mouse model of multiple sclerosis

Multiple sclerosis (MS) is a systemic inflammatory illness of the central nervous system that involves demyelinating lesions in the myelin-rich white matter and pathology in the grey matter. Despite significant advancements in drug research for MS, the disease's complex pathophysiology makes it difficult to treat the progressive forms of the disease. In this study, we identified a natural flavonoid compound icariin (ICA) as a potent effective agent for MS in ameliorating the deterioration of symptoms including the neurological deficit score and the body weight in a murine experimental autoimmune encephalomyelitis (EAE) model. These improvements were associated with decreased demyelination in the corpus callosum and neuron loss in the hippocampus and cortex confirmed by immunohistochemistry analysis. Meanwhile, it was observed that the activation of microglia in cerebral cortex and hippocampus were inhibited followed by the neuroinflammatory cytokines downregulation such as IL-1β, IL-6 and TNF-α after ICA treatment, which was probably attributable to the suppression of microglial NLRP3 inflammasome activation. Additionally, molecular docking also revealed the binding force of ICA to NLRP3 inflammasome protein complexes in vitro. Taken together, our findings have demonstrated that ICA, as pleiotropic agent, prevents EAE-induced MS by improving demyelination and neuron loss, which interferes with the neuroinflammation via microglial NLRP3 inflammasome activation.

B cell targeted therapies in inflammatory autoimmune disease of the central nervous system

Cumulative evidence along several lines indicates that B cells play an important role in the pathological course of multiple sclerosis (MS), neuromyelitisoptica spectrum disorders (NMOSD) and related CNS diseases. This has prompted extensive research in exploring the utility of targeting B cells to contain disease activity in these disorders. In this review, we first recapitulate the development of B cells from their origin in the bone marrow to their migration to the periphery, including the expression of therapy-relevant surface immunoglobulin isotypes. Not only the ability of B cells to produce cytokines and immunoglobulins seems to be essential in driving neuroinflammation, but also their regulatory functions strongly impact pathobiology. We then critically assess studies of B cell depleting therapies, including CD20 and CD19 targeting monoclonal antibodies, as well as the new class of B cell modulating substances, Bruton´s tyrosinekinase (BTK) inhibitors, in MS, NMOSD and MOGAD.

The effect of exercise on cognitive function in people with multiple sclerosis: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

A growing body of research examining the effect of exercise on cognitive function in people with multiple sclerosis (MS), while findings of available studies were conflicting. We aimed to explore the effect of exercise on cognitive function in MS patients.

METHODS

For this systematic review and meta-analysis, we searched PubMed, Web of Science, EBSCO, Cochrane, and Scopus electronic databases, through July 18, 2022. Cochrane risk assessment tool was used to evaluate the methodological quality of the included literature.

RESULTS

Twenty-one studies with a total of 23 experimental groups and 21 control groups met the inclusion criteria. There was a significant effect of exercise on improving cognitive function in MS patients, while the effect size was small (Cohen's d = 0.20, 95% CI 0.06-0.34, p < 0.001, I² = 39.31%). Subgroup analysis showed that exercise significantly improved memory (Cohen's d = 0.17, 95% CI 0.02-0.33, p = 0.03, I² = 7.59%). In addition, multicomponent training, exercise conducted 8 weeks and 10 weeks, up to 60 min per session, 3 times or more per week, 180 min or more per week increased cognitive function significantly. Furthermore, a worse basal MS status (defined by the Expanded Disability Status Scale) and an older age were associated with greater improvement in cognitive function.

CONCLUSION

MS patients are recommended to participate in at least three multicomponent training sessions per week, with each session lasting up to 60 min, and the exercise goal of 180 min per week can be achieved by increasing the frequency of exercise. Exercise lasting 8 or 10 weeks is best for cognitive function improvement. Additionally, a worse basal MS status, or the older the age, the greater effect on cognitive function.

Extracellular vesicles as contributors in the pathogenesis of multiple sclerosis

Extracellular vesicles (EVs) are a heterogeneous family of extracellular structures bounded by a phospholipid bilayer, released by all cell types in various biological fluids, such as blood and cerebrospinal fluid (CSF), playing important roles in intercellular communication, both locally and systemically. EVs carry and deliver a variety of bioactive molecules (proteins, nucleic acids, lipids and metabolites), conferring epigenetic and phenotypic changes to the recipient cells and thus resulting as important mediators of both homeostasis and pathogenesis. In neurological diseases, such as multiple sclerosis (MS), the EV ability to cross Blood-Brain Barrier (BBB), moving from central nervous system (CNS) to the peripheral circulation and vice versa, has increased the interest in EV study in the neurological field. In the present review, we will provide an overview of the recent advances made in understanding the pathogenic role of EVs regarding the immune response, the BBB dysfunction and the CNS inflammatory processes.

High levels of kappa free light chain synthesis predict cognitive decline in relapsing-remitting multiple sclerosis

Background

Evolving evidence suggests that measurement of cerebrospinal fluid (CSF) kappa free light chain (KFLC) synthesis has high diagnostic sensitivity and specificity for multiple sclerosis (MS), but its prognostic ability is less investigated. The usefulness of KFLC in predicting cognitive impairment (CI) is still unknown.

Methods

In a monocentric longitudinal retrospecitve cohort study, KFLC-index ([CSF KFLC/serum KFLC]/[CSF albumin/serum albumin]) measured by latex-enhanced immunonephelometry was prospectively determined as part of the diagnostic workup in patients with early relapsing-remitting MS (RRMS, n=77). The ability of KFLC-index to predict information processing speed (IPS) worsening as assessed with the symbol digit modalities test (SDMT) was investigated in univariable and multivariable models.

Results

In patients with KFLC-index>100 (n=31), 11 subjects (35.5%) showed reduced SDMT scores by ≥8 points at follow-up (mean follow-up time 7.3 ± 2.6 years), compared with their baseline scores (p=0.01). Baseline KFLC-index>100 was strongly associated with a higher hazard of SDMT score reduction at follow-up (adjusted hazard ratio 10.5, 95% confidence interval 2.2-50.8, p=0.003; median time to SDMT reduction 7 years).

Conclusion

Intrathecal KFLC synthesis has become an attractive diagnostic tool for MS. We show for the first time that in a real-world setting of early RRMS, KFLC-index predicted cognitive decline. Whether this predictive ability of KFLC-index also concerns other cognitive domains than IPS, warrants further investigations.