Axonal damage in acute multiple sclerosis lesions

Progressive visual function impairment as the predominant symptom of the transition phase to secondary progressive multiple sclerosis: A case report

BACKGROUND

No reliable indicators of the transition to the progressive course in multiple sclerosis (MS) have been identified so far. The main clinical feature of the progressive phase of MS is usually impairment of walking. Magnetic resonance imaging and optical coherence tomography have emerged recently as promising tools to assess increasing neurodegeneration and axonal loss in disease progression in MS.

METHODS

CASE REPORT

RESULTS

We report a case of progressive visual impairment as the dominant symptom in the transition to secondary progressive MS.

CONCLUSIONS

Impairment of vision, together with walking and cognition, should be considered to better define the transition from relapsing/remitting to secondary-progressive MS.

Disease activity in progressive multiple sclerosis can be effectively reduced by cladribine

BACKGROUND

Evidence suggests people with non-relapsing deteriorating ("progressive") multiple sclerosis (pwPMS) may benefit from disease-modifying immune therapy (DMT). However, only one such treatment (ocrelizumab) has been licensed and is highly restricted to pwPMS suffering from the primary progressive phenotype. The difficulties assessing treatment outcome in pwPMS is one important reason for the lack of respective DMT. The concentration of neurofilaments in the cerebrospinal fluid (CSF) provides a biomarker of neuro-axonal damage, and both neurofilament light (NfL) and heavy chain (NfH) levels have been used as outcome indices and to guide treatment choices.

METHODS

We report on two pwPMS, who were treated with subcutaneous cladribine undergoing CSF NfL testing, alongside MRI and clinical follow-up, before and after treatment.

RESULTS

Cladribine treatment was well tolerated without any side effects. CSF NfL after treatment revealed significant reduction (by 73% and 80%, respectively) corroborating the MRI detectable drop in disease activity. Disability mildly progressed in one, and remained stable in the other pwPMS.

CONCLUSIONS

pwPMS with detectable disease activity (MRI, elevated NfL) should be considered for DMT. NfL appears to be a sensitive index of treatment effect in pwPMS, and may be a useful outcome in clinical trials targeting this patient group. Over and above its licensed indication (relapsing MS), cladribine may be an effective treatment option for pwPMS.

DNA damage-associated oligodendrocyte degeneration precedes amyloid pathology and contributes to Alzheimer's disease and dementia

INTRODUCTION

In looking for novel non-amyloid-based etiologies for Alzheimer's disease, we explore the hypothesis that age-related myelin loss is an attractive explanation for age-associated cognitive decline and dementia.

METHODS

We performed a meta-analysis of data in the National Alzheimer's Coordinating Center database accompanied by quantitative histopathology of myelin and oligodendrocytes (OLs) in frontal cortices of 24 clinically characterized individuals. Pathological findings were further validated in an Alzheimer's disease mouse model and in culture.

RESULTS

Myelin lesions increased with cognitive impairment in an amyloid-independent fashion with signs of degeneration appearing before neuronal loss. Myelinating OLs in the gray matter showed greater vulnerability than those in white matter, and the degenerative changes correlated with evidence of DNA damage. Similar results were found in myelinating OL cultures where DNA damage caused aberrant OL cell cycle re-entry and death.

DISCUSSION

We present the first comprehensive analysis of the cell biology of early myelin loss in sporadic Alzheimer's disease.

Axonal loss in the multiple sclerosis spinal cord revisited

Preventing chronic disease deterioration is an unmet need in people with multiple sclerosis, where axonal loss is considered a key substrate of disability. Clinically, chronic multiple sclerosis often presents as progressive myelopathy. Spinal cord cross-sectional area (CSA) assessed using MRI predicts increasing disability and has, by inference, been proposed as an indirect index of axonal degeneration. However, the association between CSA and axonal loss, and their correlation with demyelination, have never been systematically investigated using human post mortem tissue. We extensively sampled spinal cords of seven women and six men with multiple sclerosis (mean disease duration= 29 years) and five healthy controls to quantify axonal density and its association with demyelination and CSA. 396 tissue blocks were embedded in paraffin and immuno-stained for myelin basic protein and phosphorylated neurofilaments. Measurements included total CSA, areas of (i) lateral cortico-spinal tracts, (ii) gray matter, (iii) white matter, (iv) demyelination, and the number of axons within the lateral cortico-spinal tracts. Linear mixed models were used to analyze relationships. In multiple sclerosis CSA reduction at cervical, thoracic and lumbar levels ranged between 19 and 24% with white (19-24%) and gray (17-21%) matter atrophy contributing equally across levels. Axonal density in multiple sclerosis was lower by 57-62% across all levels and affected all fibers regardless of diameter. Demyelination affected 24-48% of the gray matter, most extensively at the thoracic level, and 11-13% of the white matter, with no significant differences across levels. Disease duration was associated with reduced axonal density, however not with any area index. Significant association was detected between focal demyelination and decreased axonal density. In conclusion, over nearly 30 years multiple sclerosis reduces axonal density by 60% throughout the spinal cord. Spinal cord cross sectional area, reduced by about 20%, appears to be a poor predictor of axonal density.

Traumatic Brain Injury Disrupts Pain Signaling in the Brainstem and Spinal Cord

Chronic pain is a common consequence of traumatic brain injury (TBI) that can increase the suffering of a patient and pose a significant challenge to rehabilitative efforts. Unfortunately, the mechanisms linking TBI to pain are poorly understood, and specific treatments for TBI-related pain are still lacking. Our laboratory has shown that TBI causes pain sensitization in areas distant to the site of primary injury, and that changes in spinal gene expression may underlie this sensitization. The aim of this study was to examine the roles that pain modulatory pathways descending from the brainstem play in pain after TBI. Deficiencies in one type of descending inhibition, diffuse noxious inhibitory control (DNIC), have been suggested to be responsible for the development of chronic pain by allowing excess and uncontrolled afferent nociceptive inputs. Here we expand our knowledge of pain after TBI in two ways: (1) by outlining the neuropathology in pain-related centers of the brain and spinal cord involved in DNIC using the rat lateral fluid percussion (LFP) model of TBI, and (2) by evaluating the effects of a potent histone acetyl transferase inhibitor, anacardic acid (AA), on LFP-induced pain behaviors and neuropathology when administered for several days after TBI. The results revealed that TBI induces transient mechanical allodynia and a chronic persistent loss of DNIC. Further, while short-term AA treatment can block acute nociceptive sensitization and some early neuropathological changes, this treatment neither prevented the loss of DNIC nor did it alter long-term neuropathological changes in the brain or spinal cord.

The Physiological Roles of Amyloid-β Peptide Hint at New Ways to Treat Alzheimer's Disease

Amyloid-ß (Aß) is best known as the misfolded peptide that is involved in the pathogenesis of Alzheimer's disease (AD), and it is currently the primary therapeutic target in attempts to arrest the course of this disease. This notoriety has overshadowed evidence that Aß serves several important physiological functions. Aß is present throughout the lifespan, it has been found in all vertebrates examined thus far, and its molecular sequence shows a high degree of conservation. These features are typical of a factor that contributes significantly to biological fitness, and this suggestion has been supported by evidence of functions that are beneficial for the brain. The putative roles of Aß include protecting the body from infections, repairing leaks in the blood-brain barrier, promoting recovery from injury, and regulating synaptic function. Evidence for these beneficial roles comes from in vitro and in vivo studies, which have shown that the cellular production of Aß rapidly increases in response to a physiological challenge and often diminishes upon recovery. These roles are further supported by the adverse outcomes of clinical trials that have attempted to deplete Aß in order to treat AD. We suggest that anti-Aß therapies will produce fewer adverse effects if the known triggers of Aß deposition (e.g., pathogens, hypertension, and diabetes) are addressed first.

Progress in understanding the pathophysiology of multiple sclerosis

Multiple sclerosis (MS) arises in people who have a genetic susceptibility to environmental factors and events, which ultimately trigger the disease. It is thought that peripheral immune cells are mobilized and enter the CNS through the impaired blood-brain barrier in the subarachnoid space, as acute lesions show large numbers of macrophages and CD8+ T cells and, to a lesser extent, CD4+ T cells, B cells and plasma cells. Demyelination is mostly localized to focal lesions in early relapsing-remitting (RR) MS, whereas other areas of white matter appear normal. Over time, T-cell and B-cell infiltration becomes more diffuse and axonal injury more widespread, leading to self-perpetuating atrophy in both white and gray matter. With disease progression, inflammatory processes are predominantly driven by the action of CNS resident microglia cells. In addition, there is evidence that meningeal lymphoid-like structures can form and contribute to late-stage inflammation. In general, however, despite dynamic changes over time in MS pathology, lesions do not appear to differ significantly in the different classic forms of MS already identified. While all treatments approved for MS management target inflammatory components of RRMS, the B-cell-depleting antibody ocrelizumab is the first such treatment approved recently for primary progressive (PP) MS. However, recent pathological and imaging findings have prompted reconsideration of the clinical phenotypes of MS patients proposed by Lublin's 2013 classification, including clinical and MRI signs of activity, and new imaging biomarkers of remyelination are now being investigated for new strategies of MS management.

Epigenomic signature of adrenoleukodystrophy predicts compromised oligodendrocyte differentiation

Epigenomic changes may either cause disease or modulate its expressivity, adding a layer of complexity to mendelian diseases. X‐linked adrenoleukodystrophy (X‐ALD) is a rare neurometabolic condition exhibiting discordant phenotypes, ranging from a childhood cerebral inflammatory demyelination (cALD) to an adult‐onset mild axonopathy in spinal cords (AMN). The AMN form may occur with superimposed inflammatory brain demyelination (cAMN). All patients harbor loss of function mutations in the ABCD1 peroxisomal transporter of very‐long chain fatty acids. The factors that account for the lack of genotype‐phenotype correlation, even within the same family, remain largely unknown. To gain insight into this matter, here we compared the genome‐wide DNA methylation profiles of morphologically intact frontal white matter areas of children affected by cALD with adult cAMN patients, including male controls in the same age group. We identified a common methylomic signature between the two phenotypes, comprising (i) hypermethylation of genes harboring the H3K27me3 mark at promoter regions, (ii) hypermethylation of genes with major roles in oligodendrocyte differentiation such as MBP, CNP, MOG and PLP1 and (iii) hypomethylation of immune‐associated genes such as IFITM1 and CD59. Moreover, we found increased hypermethylation in CpGs of genes involved in oligodendrocyte differentiation, and also in genes with H3K27me3 marks in their promoter regions in cALD compared with cAMN, correlating with transcriptional and translational changes. Further, using a penalized logistic regression model, we identified the combined methylation levels of SPG20, UNC45A and COL9A3 and also, the combined expression levels of ID4 and MYRF to be good markers capable of discriminating childhood from adult inflammatory phenotypes. We thus propose the hypothesis that an epigenetically controlled, altered transcriptional program may drive an impaired oligodendrocyte differentiation and aberrant immune activation in X‐ALD patients. These results shed light into disease pathomechanisms and uncover putative biomarkers of interest for prognosis and phenotypic stratification.

Remyelination: A Potential Therapeutic Strategy for Alzheimer's Disease?

Myelin is a lipid-rich multilamellar membrane that wraps around long segments of neuronal axons and it increases the conduction of action potentials, transports the necessary trophic support to the neuronal axons, and reduces the energy consumed by the neuronal axons. Together with axons, myelin is a prerequisite for the higher functions of the central nervous system and complex forms of network integration. Myelin impairments have been suggested to lead to neuronal dysfunction and cognitive decline. Accumulating evidence, including brain imaging and postmortem and genetic association studies, has implicated myelin impairments in Alzheimer's disease (AD). Increasing data link myelin impairments with amyloid-β (Aβ) plaques and tau hyperphosphorylation, which are both present in patients with AD. Moreover, aging and apolipoprotein E (ApoE) may be involved in the myelin impairments observed in patients with AD. Decreased neuronal activity, increased Aβ levels, and inflammation further damage myelin in patients with AD. Furthermore, treatments that promote myelination contribute to the recovery of neuronal function and improve cognition. Therefore, strategies targeting myelin impairment may provide therapeutic opportunities for patients with AD.

Multiple Sclerosis Pathology

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS), which gives rise to focal lesions in the gray and white matter and to diffuse neurodegeneration in the entire brain. In this review, the spectrum of MS lesions and their relation to the inflammatory process is described. Pathology suggests that inflammation drives tissue injury at all stages of the disease. Focal inflammatory infiltrates in the meninges and the perivascular spaces appear to produce soluble factors, which induce demyelination or neurodegeneration either directly or indirectly through microglia activation. The nature of these soluble factors, which are responsible for demyelinating activity in sera and cerebrospinal fluid of the patients, is currently undefined. Demyelination and neurodegeneration is finally accomplished by oxidative injury and mitochondrial damage leading to a state of "virtual hypoxia."

Nimodipine confers clinical improvement in two models of experimental autoimmune encephalomyelitis

Multiple sclerosis is characterised by inflammatory neurodegeneration, with axonal injury and neuronal cell death occurring in parallel to demyelination. Regarding the molecular mechanisms responsible for demyelination and axonopathy, energy failure, aberrant expression of ion channels and excitotoxicity have been suggested to lead to Ca2+ overload and subsequent activation of calcium-dependent damage pathways. Thus, the inhibition of Ca2+ influx by pharmacological modulation of Ca2+ channels may represent a novel neuroprotective strategy in the treatment of secondary axonopathy. We therefore investigated the effects of the L-type voltage-gated calcium channel blocker nimodipine in two different models of mouse experimental autoimmune encephalomyelitis (EAE), an established experimental paradigm for multiple sclerosis. We show that preventive application of nimodipine (10 mg/kg per day) starting on the day of induction had ameliorating effects on EAE in SJL/J mice immunised with encephalitic myelin peptide PLP139-151 , specifically in late-stage disease. Furthermore, supporting these data, administration of nimodipine to MOG35-55 -immunised C57BL/6 mice starting at the peak of pre-established disease, also led to a significant decrease in disease score, indicating a protective effect on secondary CNS damage. Histological analysis confirmed that nimodipine attenuated demyelination, axonal loss and pathological axonal β-amyloid precursor protein accumulation in the cerebellum and spinal cord in the chronic phase of disease. Of note, we observed no effects of nimodipine on the peripheral immune response in EAE mice with regard to distribution, antigen-specific proliferation or activation patterns of lymphocytes. Taken together, our data suggest a CNS-specific effect of L-type voltage-gated calcium channel blockade to inflammation-induced neurodegeneration.

Microglial Phenotypes and Functions in Multiple Sclerosis

Microglia are the resident immune cells that constantly survey the central nervous system. They can adapt to their environment and respond to injury or insult by altering their morphology, phenotype, and functions. It has long been debated whether microglial activation is detrimental or beneficial in multiple sclerosis (MS). Recently, the two opposing yet connected roles of microglial activation have been described with the aid of novel microglial markers, RNA profiling, and in vivo models. In this review, microglial phenotypes and functions in the context of MS will be discussed with evidence from both human pathological studies, in vitro and in vivo models. Microglial functional diversity-phagocytosis, antigen presentation, immunomodulation, support, and repair-will also be examined in detail. In addition, this review discusses the emerging evidence for microglia-related targets as biomarkers and therapeutic targets for MS.

Microglial activation and the nitric oxide/cGMP/PKG pathway underlie enhanced neuronal vulnerability to mitochondrial dysfunction in experimental multiple sclerosis

During multiple sclerosis (MS), a close link has been demonstrated to occur between inflammation and neuro-axonal degeneration, leading to the hypothesis that immune mechanisms may promote neurodegeneration, leading to irreversible disease progression. Energy deficits and inflammation-driven mitochondrial dysfunction seem to be involved in this process. In this work we investigated, by the use of striatal electrophysiological field-potential recordings, if the inflammatory process associated with experimental autoimmune encephalomyelitis (EAE) is able to influence neuronal vulnerability to the blockade of mitochondrial complex IV, a crucial component for mitochondrial activity responsible of about 90% of total cellular oxygen consumption. We showed that during the acute relapsing phase of EAE, neuronal susceptibility to mitochondrial complex IV inhibition is markedly enhanced. This detrimental effect was counteracted by the pharmacological inhibition of microglia, of nitric oxide (NO) synthesis and its intracellular pathway (involving soluble guanylyl cyclase, sGC, and protein kinase G, PKG). The obtained results suggest that mitochondrial complex IV exerts an important role in maintaining neuronal energetic homeostasis during EAE. The pathological processes associated with experimental MS, and in particular the activation of microglia and of the NO pathway, lead to an increased neuronal vulnerability to mitochondrial complex IV inhibition, representing promising pharmacological targets.

Nogo receptor expression in microglia/macrophages during experimental autoimmune encephalomyelitis progression

Myelin-associated inhibitory factors within the central nervous system (CNS) are considered to be one of the main obstacles for axonal regeneration following disease or injury. The nogo receptor 1 (NgR1) has been well documented to play a key role in limiting axonal regrowth in the injured and diseased mammalian CNS. However, the role of nogo receptor in immune cell activation during CNS inflammation is yet to be mechanistically elucidated. Microglia/macrophages are immune cells that are regarded as pathogenic contributors to inflammatory demyelinating lesions in multiple sclerosis (MS). In this study, the animal model of MS, experimental autoimmune encephalomyelitis (EAE) was induced in ngr1^+/+ and ngr1^–/– female mice following injection with the myelin oligodendrocyte glycoprotein (MOG_35–55) peptide. A fate-map analysis of microglia/macrophages was performed throughout spinal cord sections of EAE-induced mice at clinical scores of 0, 1, 2 and 3, respectively (increasing locomotor disability) from both genotypes, using the CD11b and Iba1 cell markers. Western immunoblotting using lysates from isolated spinal cord microglia/macrophages, along with immunohistochemistry and flow cytometric analysis, was performed to demonstrate the expression of nogo receptor and its two homologs during EAE progression. Myelin protein engulfment during EAE progression in ngr1^+/+ and ngr1^–/– mice was demonstrated by western immunblotting of lysates from isolated spinal cord microglia/macrophages, detecting levels of Nogo-A and MOG. The numbers of M1 and M2 microglia/macrophage phenotypes present in the spinal cords of EAE-induced ngr1^+/+ and ngr1^–/– mice, were assessed by flow cytometric analysis using CD38 and Erg-2 markers. A significant difference in microglia/macrophage numbers between ngr1^+/+ and ngr1^–/– mice was identified during the progression of the clinical symptoms of EAE, in the white versus gray matter regions of the spinal cord. This difference was unrelated to the expression of NgR on these macrophage/microglial cells. We have identified that as EAE progresses, the phagocytic activity of microglia/macrophages with myelin debris, in ngr1^–/– mice, was enhanced. Moreover, we show a modulation from a predominant M1-pathogenic to the M2-neurotrophic cell phenotype in the ngr1^–/– mice during EAE progression. These findings suggest that CNS-specific macrophages and microglia of ngr1^–/– mice may exhibit an enhanced capacity to clear inhibitory molecules that are sequestered in inflammatory lesions.

Inflammatory demyelinating diseases of the central nervous system

Inflammatory demyelinating diseases are a heterogeneous group of disorders, which occur against the background of an acute or chronic inflammatory process. The pathologic hallmark of multiple sclerosis (MS) is the presence of focal demyelinated lesions with partial axonal preservation and reactive astrogliosis. Demyelinated plaques are present in the white as well as gray matter, such as the cerebral or cerebellar cortex and brainstem nuclei. Activity of the disease process is reflected by the presence of lesions with ongoing myelin destruction. Axonal and neuronal destruction in the lesions is a major substrate for permanent neurologic deficit in MS patients. The MS pathology is qualitatively similar in different disease stages, such as relapsing remitting MS or secondary or primary progressive MS, but the prevalence of different lesion types differs quantitatively. Acute MS and Balo's type of concentric sclerosis appear to be variants of classic MS. In contrast, neuromyelitis optica (NMO) and spectrum disorders (NMOSD) are inflammatory diseases with primary injury of astrocytes, mediated by aquaporin-4 antibodies. Finally, we discuss the histopathology of other inflammatory demyelinating diseases such as acute disseminated encephalomyelitis and myelin oligodendrocyte glycoprotein antibody-associated demyelination. Knowledge of the heterogenous immunopathology in demyelinating diseases is important, to understand the clinical presentation and disease course and to find the optimal treatment for an individual patient.

Amyloid-β Homeostasis Bridges Inflammation, Synaptic Plasticity Deficits and Cognitive Dysfunction in Multiple Sclerosis

Cognitive deficits are frequently observed in multiple sclerosis (MS), mainly involving processing speed and episodic memory. Both demyelination and gray matter atrophy can contribute to cognitive deficits in MS. In recent years, neuroinflammation is emerging as a new factor influencing clinical course in MS. Inflammatory cytokines induce synaptic dysfunction in MS. Synaptic plasticity occurring within hippocampal structures is considered as one of the basic physiological mechanisms of learning and memory. In experimental models of MS, hippocampal plasticity is profoundly altered by proinflammatory cytokines. Although mechanisms of inflammation-induced hippocampal pathology in MS are not completely understood, alteration of Amyloid-β (Aβ) metabolism is emerging as a key factor linking together inflammation, synaptic plasticity and neurodegeneration in different neurological diseases. We explored the correlation between concentrations of Aβ_1–42 and the levels of some proinflammatory and anti-inflammatory cytokines (interleukin-1β (IL-1β), IL1-ra, IL-8, IL-10, IL-12, tumor necrosis factor α (TNFα), interferon γ (IFNγ)) in the cerebrospinal fluid (CSF) of 103 remitting MS patients. CSF levels of Aβ_1–42 were negatively correlated with the proinflammatory cytokine IL-8 and positively correlated with the anti-inflammatory molecules IL-10 and interleukin-1 receptor antagonist (IL-1ra). Other correlations, although noticeable, were either borderline or not significant. Our data show that an imbalance between proinflammatory and anti-inflammatory cytokines may lead to altered Aβ homeostasis, representing a key factor linking together inflammation, synaptic plasticity and cognitive dysfunction in MS. This could be relevant to identify novel therapeutic approaches to hinder the progression of cognitive dysfunction in MS.

Use of interferon beta in multiple sclerosis: rationale for early treatment and evidence for dose- and frequency-dependent effects on clinical response

The current approach to the use of interferon (IFN) beta in the treatment of multiple sclerosis (MS) is, in general, conservative. However, recent findings about early events in MS and data on dose-response relationships with IFN beta indicate that such an approach may be suboptimal. Four lines of evidence suggest that delays in the initiation of therapy with IFN beta may be detrimental: I) axonal damage secondary to inflammation starts very early in the course of MS; 2) pathological events occurring early in MS are predictive of the future course of the disease; 3) inflammatory activity in relapsing MS is not confined to episodes of clinical impairment, but often starts before the first such episode and generally continues during remissions; and 4) the immune-mediated activity that underlies MS may become more difficult to control as the disease progresses. An early treatment strategy is also supported by data from two recently published clinical studies. In addition, preclinical and clinical results suggest that the beneficial effects of IFN may be dose- and frequency-dependent Taken together, these findings indicate that treatment with IFN beta should be started as early as possible in the course of MS, and suggest that, in order to maximize patient benefit, the highest possible dose of IFN beta should be chosen. Multiple Sclerosis (2002) 8, 2-9

International consensus statement on the use of disease-modifying agents in multiple sclerosis

Objective:To provide recommendations on the use of disease-modifying agents in the management of multiple sclerosis (MS) and to ensure that treatment will be available to those patients who may benefit.Methods:An initial draft of the consensus statement was prepared by the Steering Committee and amended in the light of written comments from a group of MS specialists. At a subsequent workshop, the wording of the consensus statement was discussed, modified if necessary, and the participants indicated their level of support using an electronic voting system. A new draft of the statement was then sent to a much larger group of international opinion leaders in MS for further comment.Results:A number of statements were agreed, which outline the criteria for consideration of disease-modifying therapy for MS and recommendations for treatment. Each statement was accepted completely, or with only minor reservations by 95% or more of those present at the workshop. Conclusions: Periodic reviews and modifications to the statement will be required, as new approaches to the treatment of MS and other therapeutic agents become available. Multiple Sclerosis (2002)8,19-23

Experimental autoimmune encephalomyelitis from a tissue energy perspective

Increasing evidence suggests a key role for tissue energy failure in the pathophysiology of multiple sclerosis (MS). Studies in experimental autoimmune encephalomyelitis (EAE), a commonly used model of MS, have been instrumental in illuminating the mechanisms that may be involved in compromising energy production. In this article, we review recent advances in EAE research focussing on factors that conspire to impair tissue energy metabolism, such as tissue hypoxia, mitochondrial dysfunction, production of reactive oxygen/nitrogen species, and sodium dysregulation, which are directly affected by energy insufficiency, and promote cellular damage. A greater understanding of how inflammation affects tissue energy balance may lead to novel and effective therapeutic strategies that ultimately will benefit not only people affected by MS but also people affected by the wide range of other neurological disorders in which neuroinflammation plays an important role.

Suppression of Inflammatory Demyelinaton and Axon Degeneration through Inhibiting Kv3 Channels

The development of neuroprotective and repair strategies for treating progressive multiple sclerosis (MS) requires new insights into axonal injury. 4-aminopyridine (4-AP), a blocker of voltage-gated K⁺ (Kv) channels, is used in symptomatic treatment of progressive MS, but the underlying mechanism remains unclear. Here we report that deleting Kv3.1—the channel with the highest 4-AP sensitivity—reduces clinical signs in experimental autoimmune encephalomyelitis (EAE), a mouse model for MS. In Kv3.1 knockout (KO) mice, EAE lesions in sensory and motor tracts of spinal cord were markedly reduced, and radial astroglia were activated with increased expression of brain derived neurotrophic factor (BDNF). Kv3.3/Kv3.1 and activated BDNF receptors were upregulated in demyelinating axons in EAE and MS lesions. In spinal cord myelin coculture, BDNF treatment promoted myelination, and neuronal firing via altering channel expression. Therefore, suppressing Kv3.1 alters neural circuit activity, which may enhance BNDF signaling and hence protect axons from inflammatory insults.

Differential contribution of microglia and monocytes in neurodegenerative diseases

Neuroinflammation is a hallmark of neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). Microglia, the innate immune cells of the CNS, are the first to react to pathological insults. However, multiple studies have also demonstrated an involvement of peripheral monocytes in several neurodegenerative diseases. Due to the different origins of these two cell types, it is important to distinguish their role and function in the development and progression of these diseases. In this review, we will summarize and discuss the current knowledge of the differential contributions of microglia and monocytes in the common neurodegenerative diseases AD, PD, and ALS, as well as multiple sclerosis, which is now regarded as a combination of inflammatory processes and neurodegeneration. Until recently, it has been challenging to differentiate microglia from monocytes, as there were no specific markers. Therefore, the recent identification of specific molecular signatures of both cell types will help to advance our understanding of their differential contribution in neurodegenerative diseases.

Targets of therapy in progressive MS

Highly effective anti-inflammatory therapies have so far been developed for patients with relapsing/remitting multiple sclerosis, which also show some benefits in the early progressive stage of the disease. However, treatment options for patients, who have entered the progressive phase, are still limited. Disease starts as an inflammatory process, which induces focal demyelinating lesions in the gray and white matter. This stage of the disease dominates in the relapsing phase, extends into the early stages of progressive disease, and can be targeted by current anti-inflammatory treatments. In parallel, inflammation accumulates behind a closed or repaired blood brain barrier, and this process peaks in the late relapsing and early progressive stage and then declines. Some data suggest that this process may be targeted by immune ablation and hematopoietic stem cell transplantation. In the late stage, inflammation may decline to levels seen in age-matched controls, but age and disease burden–related neurodegeneration ensues. Such neurodegeneration affects the damaged brain and spinal cord, in which functional reserve capacity is exhausted, giving rise to further disability progression. Anti-inflammatory treatments are unlikely to be beneficial in this stage of the disease, but neuroprotective and repair-inducing strategies may still be effective.

MOG-IgG associated optic neuritis is not multiple sclerosis

ABSTRACT Autoantibodies against myelin oligodendrocyte glycoprotein (MOG-IgG) have been reported in patients with inflammatory central nervous system disorders including isolated optic neuritis (ON). We compared our MOG-IgG ON patients with multiple sclerosis (MS) patients presenting with ON. Methods and results: Among the total of 38 patients with optic neuropathies, six patients with isolated ON were MOG-IgG positive and eight patients with ON fulfilled the diagnostic criteria for MS. All MS patients were negative for MOG-IgG using a cell-based assay. When compared with the MS group, the MOG-IgG patients were older (mean 47 years), more frequently male (ratio 2:1) and had a higher frequency of bilateral and/or recurrent ON. The brain magnetic resonance imaging of all MOG-IgG positive patients was normal or had only unspecific white matter T2 lesions. Conclusion: These findings suggest that MOG-IgG is a biomarker of an inflammatory demyelinating CNS disease distinct from MS.

Lineage tracing reveals dynamic changes in oligodendrocyte precursor cells following cuprizone-induced demyelination

The regeneration of oligodendrocytes is a crucial step in recovery from demyelination, as surviving oligodendrocytes exhibit limited structural plasticity and rarely form additional myelin sheaths. New oligodendrocytes arise through the differentiation of platelet-derived growth factor receptor α (PDGFRα) expressing oligodendrocyte progenitor cells (OPCs) that are widely distributed throughout the CNS. Although there has been detailed investigation of the behavior of these progenitors in white matter, recent studies suggest that disease burden in multiple sclerosis (MS) is more strongly correlated with gray matter atrophy. The timing and efficiency of remyelination in gray matter is distinct from white matter, but the dynamics of OPCs that contribute to these differences have not been defined. Here, we used in vivo genetic fate tracing to determine the behavior of OPCs in gray and white matter regions in response to cuprizone-induced demyelination. Our studies indicate that the temporal dynamics of OPC differentiation varies significantly between white and gray matter. While OPCs rapidly repopulate the corpus callosum and mature into CC1 expressing mature oligodendrocytes, OPC differentiation in the cingulate cortex and hippocampus occurs much more slowly, resulting in a delay in remyelination relative to the corpus callosum. The protracted maturation of OPCs in gray matter may contribute to greater axonal pathology and disease burden in MS.

Loss of Gas6 and Axl signaling results in extensive axonal damage, motor deficits, prolonged neuroinflammation, and less remyelination following cuprizone exposure

The TAM (Tyro3, Axl, and MerTK) family of receptor tyrosine kinases (RTKs) and their ligands, Gas6 and ProS1, are important for innate immune responses and central nervous system (CNS) homeostasis. While only Gas6 directly activates Axl, ProS1 activation of Tyro3/MerTK can indirectly activate Axl through receptor heterodimerization. Therefore, we generated Gas6^-/- Axl^-/- double knockout (DKO) mice to specifically examine the contribution of this signaling axis while retaining ProS1 signaling through Tyro3 and MerTK. We found that naïve young adult DKO and WT mice have comparable myelination and equal numbers of axons and oligodendrocytes in the corpus callosum. Using the cuprizone model of demyelination/remyelination, transmission electron microscopy revealed extensive axonal swellings containing autophagolysosomes and multivesicular bodies, and fewer myelinated axons in brains of DKO mice at 3-weeks recovery from a 6-week cuprizone diet. Analysis of immunofluorescent staining demonstrated more SMI32+ and APP+ axons and less myelin in the DKO mice. There were no significant differences in the number of GFAP+ astrocytes or Iba1+ microglia/macrophages between the groups of mice. However, at 6-weeks cuprizone and recovery, DKO mice had increased proinflammatory cytokine and altered suppressor of cytokine signaling (SOCS) mRNA expression supporting a role for Gas6-Axl signaling in proinflammatory cytokine suppression. Significant motor deficits in DKO mice relative to WT mice on cuprizone were also observed. These data suggest that Gas6-Axl signaling plays an important role in maintaining axonal integrity and regulating and reducing CNS inflammation that cannot be compensated for by ProS1/Tyro3/MerTK signaling.

Nogo-A antibodies enhance axonal repair and remyelination in neuro-inflammatory and demyelinating pathology

Two hallmarks of chronic multiple sclerosis lesions are the absence of significant spontaneous remyelination and primary as well as secondary neurodegeneration. Both characteristics may be influenced by the presence of inhibitory factors preventing myelin and neuronal repair. We investigated the potential of antibodies against Nogo-A, a well-known inhibitory protein for neuronal growth and plasticity, to enhance neuronal regeneration and remyelination in two animal models of multiple sclerosis. We induced a targeted experimental autoimmune encephalomyelitis (EAE) lesion in the dorsal funiculus of the cervical spinal cord of adult rats resulting in a large drop of skilled forelimb motor functions. We subsequently observed improved recovery of forelimb function after anti-Nogo-A treatment. Anterograde tracing of the corticospinal tract revealed enhanced axonal sprouting and arborisation within the spinal cord gray matter preferentially targeting pre-motor and motor spinal cord laminae on lesion level and above in the anti-Nogo-A-treated animals. An important additional effect of Nogo-A-neutralization was enhanced remyelination observed after lysolecithin-induced demyelination of spinal tracts. Whereas remyelinated fiber numbers in the lesion site were increased several fold, no effect of Nogo-A-inhibition was observed on oligodendrocyte precursor proliferation, migration, or differentiation. Enhancing remyelination and promoting axonal regeneration and plasticity represent important unmet medical needs in multiple sclerosis. Anti-Nogo-A antibodies hold promise as a potential new therapy for multiple sclerosis, in particular during the chronic phase of the disease when neurodegeneration and remyelination failure determine disability evolution.

Loss of 'homeostatic' microglia and patterns of their activation in active multiple sclerosis

Microglia and macrophages accumulate at the sites of active demyelination and neurodegeneration in the multiple sclerosis brain and are thought to play a central role in the disease process. We used recently described markers to characterize the origin and functional states of microglia/macrophages in acute, relapsing and progressive multiple sclerosis. We found microglia activation in normal white matter of controls and that the degree of activation increased with age. This microglia activation was more pronounced in the normal-appearing white matter of patients in comparison to controls and increased with disease duration. In contrast to controls, the normal-appearing white matter of patients with multiple sclerosis showed a significant reduction of P2RY12, a marker expressed in homeostatic microglia in rodents, which was completely lost in active and slowly expanding lesions. Early stages of demyelination and neurodegeneration in active lesions contained microglia with a pro-inflammatory phenotype, which expressed molecules involved in phagocytosis, oxidative injury, antigen presentation and T cell co-stimulation. In later stages, the microglia and macrophages in active lesions changed to a phenotype that was intermediate between pro- and anti-inflammatory activation. In inactive lesions, the density of microglia/macrophages was significantly reduced and microglia in part converted to a P2RY12+ phenotype. Analysis of TMEM119, which is expressed on microglia but not on recruited macrophages, demonstrated that on average 45% of the macrophage-like cells in active lesions were derived from the resident microglia pool. Our study demonstrates the loss of the homeostatic microglial signature in active multiple sclerosis with restoration associated with disease inactivity.

Outcome of MS relapses in the era of disease-modifying therapy

Background

In multiple sclerosis (MS), neurological disability results from incomplete remission of relapses and from relapse-independent progression. Intravenous high dose methylprednisolone (IVMP) is the established standard treatment to accelerate clinical relapse remission, although some patients do not respond. Most studies of relapse treatment have been performed when few patients received disease-modifying treatment and may no longer apply today.

Methods

We prospectively assessed, over one year, the course of patients who presented with a clinically isolated syndrome (CIS) or MS relapse, documenting demographic, clinical, treatment and outcome data. A standardized follow-up examination was performed 10–14 days after end of relapse treatment.

Results

We documented 119 relapses in 108 patients (31 CIS, 77 MS). 114 relapses were treated with IVMP resulting in full remission (29.2%), partial remission (38.7%), no change (18.2%) or worsening (4.4%). In 27 relapses (22.7%), escalating relapse treatment was indicated, and performed in 24, using double-dose IVMP (n = 18), plasmapheresis (n = 2) or immunoadsorption (n = 4).

Conclusions

Standardised follow-up visits and outcome documentation in treated relapses led to escalating relapse treatment in every fifth relapse. We recommend incorporating scheduled follow-up visits into routine relapse management. Our data facilitate the design of prospective trials addressing methods and timelines of relapse treatment.

Multimarker risk stratification approach at multiple sclerosis onset

Delay in the diagnosis of multiple sclerosis (MS) stems from the lack of specific clinical and analytical markers to assist in the early diagnosis and prediction of progressive course. We propose a decision-tree model that better defines early at onset MS patients and those with the progressive form by analysing a 12-biomarkers panel in serum and CSF samples of patients with MS, other neurological diseases (OND) and healthy contols. Thus, patients at onset of neurological disease were first classified by serum IL-7 levels <141pg/ml (OR=6.51, p<0.001). Combination of IL-7 and CXCL10 indicated risk for a specific MS clinical form, where IL-7<141 and CXCL10<570pg/ml were associated with the highest risk for PP-MS (OR=22, p=0.01). Unexpectedly, both PP-MS and RR-MS patients shared significantly decreased prototypical biomarkers of inflammation and tissue regeneration in CSF than OND suggesting a defective intrinsic immune response playing a role at the beginning of the disease.

Remyelination therapies: a new direction and challenge in multiple sclerosis

Multiple sclerosis is characterized by inflammatory activity that results in destruction of the myelin sheaths that enwrap axons. The currently available medications for multiple sclerosis are predominantly immune-modulating and do not directly promote repair. White matter regeneration, or remyelination, is a new and exciting potential approach to treating multiple sclerosis, as remyelination repairs the damaged regions of the central nervous system. A wealth of new strategies in animal models that promote remyelination, including the repopulation of oligodendrocytes that produce myelin, has led to several clinical trials to test new reparative therapies. In this Review, we highlight the biology of, and obstacles to, remyelination. We address new strategies to improve remyelination in preclinical models, highlight the therapies that are currently undergoing clinical trials and discuss the challenges of objectively measuring remyelination in trials of repair in multiple sclerosis.

Axonal transport deficits in multiple sclerosis: spiraling into the abyss

The transport of mitochondria and other cellular components along the axonal microtubule cytoskeleton plays an essential role in neuronal survival. Defects in this system have been linked to a large number of neurological disorders. In multiple sclerosis (MS) and associated models such as experimental autoimmune encephalomyelitis (EAE), alterations in axonal transport have been shown to exist before neurodegeneration occurs. Genome-wide association (GWA) studies have linked several motor proteins to MS susceptibility, while neuropathological studies have shown accumulations of proteins and organelles suggestive for transport deficits. A reduced effectiveness of axonal transport can lead to neurodegeneration through inhibition of mitochondrial motility, disruption of axoglial interaction or prevention of remyelination. In MS, demyelination leads to dysregulation of axonal transport, aggravated by the effects of TNF-alpha, nitric oxide and glutamate on the cytoskeleton. The combined effect of all these pathways is a vicious cycle in which a defective axonal transport system leads to an increase in ATP consumption through loss of membrane organization and a reduction in available ATP through inhibition of mitochondrial transport, resulting in even further inhibition of transport. The persistent activity of this positive feedback loop contributes to neurodegeneration in MS.

Contribution of the Degeneration of the Neuro-Axonal Unit to the Pathogenesis of Multiple Sclerosis

Multiple sclerosis (MS) is a demyelinating, autoimmune disease of the central nervous system. In recent years, it has become more evident that neurodegeneration, including neuronal damage and axonal injury, underlies permanent disability in MS. This manuscript reviews some of the mechanisms that could be responsible for neurodegeneration and axonal damage in MS and highlights the potential role that dysfunctional heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) and antibodies to hnRNP A1 may play in MS pathogenesis.

Modulating inflammation and neuroprotection in multiple sclerosis

Multiple sclerosis (MS) is a neurological disorder of the central nervous system with a presentation and disease course that is largely unpredictable. MS can cause loss of balance, impaired vision or speech, weakness and paralysis, fatigue, depression, and cognitive impairment. Immunomodulation is a major target given the appearance of focal demyelinating lesions in myelin-rich white matter, yet progression and an increasing appreciation for gray matter involvement, even during the earliest phases of the disease, highlights the need to afford neuroprotection and limit neurodegenerative processes that correlate with disability. This review summarizes key aspects of MS pathophysiology and histopathology with a focus on neuroimmune interactions in MS, which may facilitate neurodegeneration through both direct and indirect mechanisms. There is a focus on processes thought to influence disease progression and the role of oxidative stress and mitochondrial dysfunction in MS. The goals and efficacy of current disease-modifying therapies and those in the pipeline are discussed, highlighting recent advances in our understanding of pathways mediating disease progression to identify and translate both immunomodulatory and neuroprotective therapeutics from the bench to the clinic.

Higher levels of myelin phospholipids in brains of neuronal α-Synuclein transgenic mice precede myelin loss

α-Synuclein is a protein involved in the pathogenesis of synucleinopathies, including Parkinson’s disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy (MSA). We investigated the role of neuronal α-Syn in myelin composition and abnormalities. The phospholipid content of purified myelin was determined by ³¹P NMR in two mouse lines modeling PD, PrP-A53T α-Syn and Thy-1 wt-α-Syn. Significantly higher levels of phospholipids were detected in myelin purified from brains of these α-Syn transgenic mouse models than in control mice. Nevertheless, myelin ultrastructure appeared intact. To further investigate the effect of α-Syn on myelin abnormalities, we systematically analyzed the striatum, a brain region associated with neurodegeneration in PD. An age and disease-dependent loss of myelin basic protein (MBP) signal was detected by immunohistochemistry in striatal striosomes (patches). The age-dependent loss of MBP signal was associated with lower P25α levels in oligodendrocytes. In addition, we found that α-Syn inhibited oligodendrocyte maturation and the formation of membranous sheets in vitro. Based on these results we concluded that neuronal α-Syn is involved in the regulation and/or maintenance of myelin phospholipid. However, axonal hypomyelination in the PD models is evident only in progressive stages of the disease and associated with α-Syn toxicity.

Oral administration of the nitroxide radical TEMPOL exhibits immunomodulatory and therapeutic properties in multiple sclerosis models

Therapies with both immunomodulatory and neuroprotective properties are thought to have the greatest promise in reducing the severity and progression of multiple sclerosis (MS). Several reactive oxygen (ROS) and reactive nitrogen species (RNS) are implicated in inflammatory-mediated damage to the central nervous system (CNS) in MS and its animal model, experimental autoimmune encephalomyelitis (EAE). TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) is a stable nitroxide radical with potent antioxidant activity. The goal of our studies was to investigate the immunomodulatory effects and therapeutic potential of orally-delivered TEMPOL in the mouse EAE model. Mice receiving TEMPOL chow ad libitum for 2weeks prior to induction of active EAE showed delayed onset and reduced incidence of disease compared to control-fed animals. Reduced disease severity was associated with limited microglial activation and fewer inflammatory infiltrates. TEMPOL's effects were immunomodulatory, not immunosuppressive: T cells produced less interferon-γ and tumor necrosis factor-α, and TEMPOL-fed mice exhibited a shift towards T_H2-type antibody responses. Both myeloid and myeloid-dendritic cells of TEMPOL-fed EAE animals had significantly lower levels of MHC class II expression than controls; CD40 was also significantly reduced. TEMPOL administration was associated with an enrichment of CD8⁺ T cell populations and CD4⁺FoxP₃⁺ regulatory populations. TEMPOL reduced the severity of clinical disease when administered after the induction of disease, and also after the onset of clinical symptoms. To exclude effects on T cell priming in vivo, TEMPOL was tested with the passive transfer of encephalitogenic T cells and was found to reduce the incidence and peak severity of disease. Protection was associated with reduced infiltrates and a relative sparing of neurofilaments and axons. The ability of oral TEMPOL to reduce inflammation and axonal damage and loss demonstrate both anti-inflammatory and protective properties, with significant promise for the treatment of MS and related neurological disorders.

Multiple sclerosis: Pathology, diagnosis and treatments

Multiple sclerosis (MS) is a complex neurodegenerative disease affecting the central nervous system (CNS). The onset of MS has been typically observed in individuals aged from 20 to 40-years, with the female to male ratio of 1:2. MS appears as abrupt onset of focal sensory disturbances that is accompanied by unilateral painless damage of vision, double vision, limb weakness, unsteadiness of gait, and bowel or bladder symptoms. Whereas the exact etiology of the disease is unknown, observational research has suggested genetic and environment influences through an underlined pathophysiology widely believed to be autoimmune in nature. Indeed, plaque of demyelination inside of the CNS with relative conservation of axons remains the clinical symptoms of MS. However, considerable advances in understanding the pathology have contributed to an early diagnosis, particularly the exact neuroanatomical setting of plaques. Accordingly, magnetic resonance imaging has been considered as the primarily adjunctive modality for the constant detection of abnormal white matter. In addition, the analysis of cerebrospinal fluid contents has also been of interest for the diagnosis to discriminate other affections such infection or vasculitis. These resulted in a broad variety of therapies that considerably control the activity and change the course and prognosis of the disease. In the present review, we evaluate the current state of knowledge on MS with emphasis on the pathology itself, the diagnosis and common therapeutical approaches accurately used.

VEP and PERG in patients with multiple sclerosis, with and without a history of optic neuritis

PURPOSE

Visual electrophysiology is routinely used to detect the visual complications of multiple sclerosis, but the analysis mostly focuses on visual evoked potential (VEP) and especially the P100 component. Our goal was to analyze the components and waveform alterations of VEPs and pattern electroretinograms (PERGs) in patients with multiple sclerosis (MS) with good vision.

METHODS

The main VEP and PERG components of 85 patients with MS were analyzed in two groups: 38 patients who had optic neuritis in their history (ON group) and 47 patients who had never had optic neuritis (MS group). The results were compared against a control group of 47 healthy subjects.

RESULTS

Both VEP and PERG alterations occurred in a greater number of patients than expected, and these alterations were not necessarily linked to ON in the history or a deterioration of visual acuity.

CONCLUSIONS

Both VEP and PERG can detect dysfunction in the visual system in MS, even if the patient has no subjective symptoms. Even if PERG is not routinely used in neuro-ophthalmology, the results suggest that PERG assessment may provide useful information describing the retinal defect in MS.

Metabolic changes in normal appearing white matter in multiple sclerosis patients using multivoxel magnetic resonance spectroscopy imaging

Demyelination and axonal degeneration caused by multiple sclerosis (MS) exist in the white matter and not only in the lesion area. Magnetic resonance spectroscopy (MRS) could provide a unique insight into metabolic changes in the normal appearing white matter (NAWM). To evaluate the subtle axonal degeneration and delineate the spatial distribution of metabolite abnormalities in the NAWM in patients with MS. A total of 17 clinically definite relapsing-remitting MS (RRMS) patients and 21 healthy controls were enrolled in this study. 2D 1H magnetic resonance spectroscopic imaging (MRSI) performed at 3 Tesla was used to measure metabolite concentrations in the frontal-parietal-occipital NAWM. Ratios of N-acetyl-aspartate (NAA) and choline (Cho) to creatine (Cr) and Cho to NAA were calculated in each voxel. MS patients showed decreased NAA/Cr and increased Cho/NAA ratios in the NAWM compared to healthy controls. In the parietal NAWM, the extent of NAA/Cr decrease was significantly higher than that in the frontal and parietal-occipital NAWM. Decreased NAA in the NAWM would provide useful metabolic information for evaluation of disease progression in MS. The high extent of NAA decrease in the parietal NAWM helps improve the accuracy of the prediction.

Combining Diffusion Tensor Metrics and DSC Perfusion Imaging: Can It Improve the Diagnostic Accuracy in Differentiating Tumefactive Demyelination from High-Grade Glioma?

BACKGROUND AND PURPOSE

Tumefactive demyelinating lesions with atypical features can mimic high-grade gliomas on conventional imaging sequences. The aim of this study was to assess the role of conventional imaging, DTI metrics (p:q tensor decomposition), and DSC perfusion in differentiating tumefactive demyelinating lesions and high-grade gliomas.

MATERIALS AND METHODS

Fourteen patients with tumefactive demyelinating lesions and 21 patients with high-grade gliomas underwent brain MR imaging with conventional, DTI, and DSC perfusion imaging. Imaging sequences were assessed for differentiation of the lesions. DTI metrics in the enhancing areas and perilesional hyperintensity were obtained by ROI analysis, and the relative CBV values in enhancing areas were calculated on DSC perfusion imaging.

RESULTS

Conventional imaging sequences had a sensitivity of 80.9% and specificity of 57.1% in differentiating high-grade gliomas (P = .049) from tumefactive demyelinating lesions. DTI metrics (p:q tensor decomposition) and DSC perfusion demonstrated a statistically significant difference in the mean values of ADC, the isotropic component of the diffusion tensor, the anisotropic component of the diffusion tensor, the total magnitude of the diffusion tensor, and rCBV among enhancing portions in tumefactive demyelinating lesions and high-grade gliomas (P ≤ .02), with the highest specificity for ADC, the anisotropic component of the diffusion tensor, and relative CBV (92.9%). Mean fractional anisotropy values showed no significant statistical difference between tumefactive demyelinating lesions and high-grade gliomas. The combination of DTI and DSC parameters improved the diagnostic accuracy (area under the curve = 0.901). Addition of a heterogeneous enhancement pattern to DTI and DSC parameters improved it further (area under the curve = 0.966). The sensitivity increased from 71.4% to 85.7% after the addition of the enhancement pattern.

CONCLUSIONS

DTI and DSC perfusion add profoundly to conventional imaging in differentiating tumefactive demyelinating lesions and high-grade gliomas. The combination of DTI metrics and DSC perfusion markedly improved diagnostic accuracy.

Relationship of acute axonal damage, Wallerian degeneration, and clinical disability in multiple sclerosis

BACKGROUND

Axonal damage and loss substantially contribute to the incremental accumulation of clinical disability in progressive multiple sclerosis. Here, we assessed the amount of Wallerian degeneration in brain tissue of multiple sclerosis patients in relation to demyelinating lesion activity and asked whether a transient blockade of Wallerian degeneration decreases axonal loss and clinical disability in a mouse model of inflammatory demyelination.

METHODS

Wallerian degeneration and acute axonal damage were determined immunohistochemically in the periplaque white matter of multiple sclerosis patients with early actively demyelinating lesions, chronic active lesions, and inactive lesions. Furthermore, we studied the effects of Wallerian degeneration blockage on clinical severity, inflammatory pathology, acute axonal damage, and long-term axonal loss in experimental autoimmune encephalomyelitis using Wallerian degeneration slow (Wld ^S ) mutant mice.

RESULTS

The highest numbers of axons undergoing Wallerian degeneration were found in the perilesional white matter of multiple sclerosis patients early in the disease course and with actively demyelinating lesions. Furthermore, Wallerian degeneration was more abundant in patients harboring chronic active as compared to chronic inactive lesions. No co-localization of neuropeptide Y-Y1 receptor, a bona fide immunohistochemical marker of Wallerian degeneration, with amyloid precursor protein, frequently used as an indicator of acute axonal transport disturbance, was observed in human and mouse tissue, indicating distinct axon-degenerative processes. Experimentally, a delay of Wallerian degeneration, as observed in Wld ^S mice, did not result in a reduction of clinical disability or acute axonal damage in experimental autoimmune encephalomyelitis, further supporting that acute axonal damage as reflected by axonal transport disturbances does not share common molecular mechanisms with Wallerian degeneration. Furthermore, delaying Wallerian degeneration did not result in a net rescue of axons in late lesion stages of experimental autoimmune encephalomyelitis.

CONCLUSIONS

Our data indicate that in multiple sclerosis, ongoing demyelination in focal lesions is associated with axonal degeneration in the perilesional white matter, supporting a role for focal pathology in diffuse white matter damage. Also, our results suggest that interfering with Wallerian degeneration in inflammatory demyelination does not suffice to prevent acute axonal damage and finally axonal loss.

Gut dysbiosis and neuroimmune responses to brain infection with Theiler's murine encephalomyelitis virus

Recent studies have begun to point out the contribution of microbiota to multiple sclerosis (MS) pathogenesis. Theiler's murine encephalomyelitis virus induced demyelinating disease (TMEV-IDD) is a model of progressive MS. Here, we first analyze the effect of intracerebral infection with TMEV on commensal microbiota and secondly, whether the early microbiota depletion influences the immune responses to TMEV on the acute phase (14 dpi) and its impact on the chronic phase (85 dpi). The intracranial inoculation of TMEV was associated with a moderate dysbiosis. The oral administration of antibiotics (ABX) of broad spectrum modified neuroimmune responses to TMEV dampening brain CD4⁺ and CD8⁺ T infiltration during the acute phase. The expression of cytokines, chemokines and VP2 capsid protein was enhanced and accompanied by clusters of activated microglia disseminated throughout the brain. Furthermore, ABX treated mice displayed lower levels of CD4⁺ and CD8⁺T cells in cervical and mesenteric lymph nodes. Increased mortality to TMEV was observed after ABX cessation at day 28pi. On the chronic phase, mice that survived after ABX withdrawal and recovered microbiota diversity showed subtle changes in brain cell infiltrates, microglia and gene expression of cytokines. Accordingly, the surviving mice of the group ABX-TMEV displayed similar disease severity than TMEV mice.

Age-related small vessel disease: a potential contributor to neurodegeneration in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disorder of the central nervous system wherein, after an initial phase of transient neurological defects, slow neurological deterioration due to progressive neuronal loss ensues. Age is a major determinant of MS progression onset and disability. Over the past years, several mechanisms have been proposed to explain the key drivers of neurodegeneration and disability accumulation in MS. However, the effect of commonly encountered age-related cerebral vessel disease, namely small vessel disease (SVD), has been largely neglected and constitutes the aim of this review. SVD shares some features with MS, that is, white matter demyelination and brain atrophy, and has been shown to contribute to the neuronal damage seen in vascular cognitive impairment. Several lines of evidence suggest that an interaction between MS and SVD may influence MS-related neurodegeneration. SVD may contribute to hypoperfusion, reduced vascular reactivity and tissue hypoxia, features seen in MS. Venule and endothelium abnormalities have been documented in MS but the role of arterioles and of other neurovascular unit structures, such as the pericyte, has not been explored. Vascular risk factors (VRF) have recently been associated with faster progression in MS, though the mechanisms are unclear since very few studies have addressed the impact of VRF and SVD on MS imaging and pathology outcomes. Therapeutic agents targeting the microvasculature and the neurovascular unit may impact both SVD and MS and may benefit patients with dual pathology.

Malignant multiple sclerosis: clinical and demographic prognostic factors

ABSTRACT Patients with malignant multiple sclerosis (MMS) reach a significant level of disability within a short period of time (Expanded Disability Status Scale score of 6 within five years). The clinical profile and progression of the disease were analyzed in a Brazilian cohort of 293 patients. Twenty-five (8,53%) patients were found to have MMS and were compared with the remaining 268 (91,47%). Women, non-white patients, older age at disease onset, shorter intervals between the first attacks, and more attacks in the first two years of the disease were all more common in the MMS group. These findings could serve as prognostic factors when making therapeutic decisions.