Identity and nature of neural stem cells in the adult human subventricular zone

The existence of neural stem cells (NSCs) in adult human brain neurogenic regions remains unresolved. To address this, we created a cell atlas of the adult human subventricular zone (SVZ) derived from fresh neurosurgical samples using single-cell transcriptomics. We discovered 2 adult radial glia (RG)-like populations, aRG1 and aRG2. aRG1 shared features with fetal early RG (eRG) and aRG2 were transcriptomically similar to fetal outer RG (oRG). We also captured early neuronal and oligodendrocytic NSC states. We found that the biological programs driven by their transcriptomes support their roles as early lineage NSCs. Finally, we show that these NSCs have the potential to transition between states and along lineage trajectories. These data reveal that multipotent NSCs reside in the adult human SVZ.

Disease-associated astrocyte epigenetic memory promotes CNS pathology

Astrocytes play important roles in the central nervous system (CNS) physiology and pathology. Indeed, astrocyte subsets defined by specific transcriptional activation states contribute to the pathology of neurologic diseases, including multiple sclerosis (MS) and its pre-clinical model experimental autoimmune encephalomyelitis (EAE) 1-8 . However, little is known about the stability of these disease-associated astrocyte subsets, their regulation, and whether they integrate past stimulation events to respond to subsequent challenges. Here, we describe the identification of an epigenetically controlled memory astrocyte subset which exhibits exacerbated pro-inflammatory responses upon re-challenge. Specifically, using a combination of single-cell RNA sequencing (scRNA-seq), assay for transposase-accessible chromatin with sequencing (ATAC-seq), chromatin immunoprecipitation with sequencing (ChIP-seq), focused interrogation of cells by nucleic acid detection and sequencing (FIND-seq), and cell-specific in vivo CRISPR/Cas9-based genetic perturbation studies we established that astrocyte memory is controlled by the metabolic enzyme ATP citrate lyase (ACLY), which produces acetyl coenzyme A (acetyl-CoA) used by the histone acetyltransferase p300 to control chromatin accessibility. ACLY + p300 + memory astrocytes are increased in acute and chronic EAE models; the genetic targeting of ACLY + p300 + astrocytes using CRISPR/Cas9 ameliorated EAE. We also detected responses consistent with a pro-inflammatory memory phenotype in human astrocytes in vitro ; scRNA-seq and immunohistochemistry studies detected increased ACLY + p300 + astrocytes in chronic MS lesions. In summary, these studies define an epigenetically controlled memory astrocyte subset that promotes CNS pathology in EAE and, potentially, MS. These findings may guide novel therapeutic approaches for MS and other neurologic diseases.

ALCAM on human oligodendrocytes mediates CD4 T cell adhesion

Multiple sclerosis is a chronic neuroinflammatory disorder characterized by demyelination, oligodendrocyte damage/loss and neuroaxonal injury in the context of immune cell infiltration in the CNS. No neuroprotective therapy is available to promote the survival of oligodendrocytes and protect their myelin processes in immune-mediated demyelinating diseases. Pro-inflammatory CD4 Th17 cells can interact with oligodendrocytes in multiple sclerosis and its animal model, causing injury to myelinating processes and cell death through direct contact. However, the molecular mechanisms underlying the close contact and subsequent detrimental interaction of Th17 cells with oligodendrocytes remain unclear. In this study we used single cell RNA sequencing, flow cytometry and immunofluorescence studies on CNS tissue from multiple sclerosis subjects, its animal model and controls to characterize the expression of cell adhesion molecules by mature oligodendrocytes. We found that a significant proportion of human and murine mature oligodendrocytes express melanoma cell adhesion molecule (MCAM) and activated leukocyte cell adhesion molecule (ALCAM) in multiple sclerosis, in experimental autoimmune encephalomyelitis and in controls, although their regulation differs between human and mouse. We observed that exposure to pro-inflammatory cytokines or to human activated T cells are associated with a marked downregulation of the expression of MCAM but not of ALCAM at the surface of human primary oligodendrocytes. Furthermore, we used in vitro live imaging, immunofluorescence and flow cytometry to determine the contribution of these molecules to Th17-polarized cell adhesion and cytotoxicity towards human oligodendrocytes. Silencing and blocking ALCAM but not MCAM limited prolonged interactions between human primary oligodendrocytes and Th17-polarized cells, resulting in decreased adhesion of Th17-polarized cells to oligodendrocytes and conferring significant protection of oligodendrocytic processes. In conclusion, we showed that human oligodendrocytes express MCAM and ALCAM, which are differently modulated by inflammation and T cell contact. We found that ALCAM is a ligand for Th17-polarized cells, contributing to their capacity to adhere and induce damage to human oligodendrocytes, and therefore could represent a relevant target for neuroprotection in multiple sclerosis.

Translocator protein is a marker of activated microglia in rodent models but not human neurodegenerative diseases

Microglial activation plays central roles in neuroinflammatory and neurodegenerative diseases. Positron emission tomography (PET) targeting 18 kDa Translocator Protein (TSPO) is widely used for localising inflammation in vivo, but its quantitative interpretation remains uncertain. We show that TSPO expression increases in activated microglia in mouse brain disease models but does not change in a non-human primate disease model or in common neurodegenerative and neuroinflammatory human diseases. We describe genetic divergence in the TSPO gene promoter, consistent with the hypothesis that the increase in TSPO expression in activated myeloid cells depends on the transcription factor AP1 and is unique to a subset of rodent species within the Muroidea superfamily. Finally, we identify LCP2 and TFEC as potential markers of microglial activation in humans. These data emphasise that TSPO expression in human myeloid cells is related to different phenomena than in mice, and that TSPO-PET signals in humans reflect the density of inflammatory cells rather than activation state.

Clinical course, imaging, and pathological features of 45 adult and pediatric cases of myelin oligodendrocyte glycoprotein antibody-associated disease

BACKGROUND

Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is a recently described neuroinflammatory demyelinating disease.

OBJECTIVE

To better understand the clinical spectrum, risk factors and outcomes in MOGAD.

METHODS

Retrospective cohort study including all subjects harboring anti-MOG antibodies identified in major academic hospitals across the province of Quebec.

RESULTS

We identified 45 MOGAD cases. The minimal estimated point-prevalence was 0.52/100 000 in Quebec. Median age at presentation was 32 years (range 1-71) with equal sex ratio. Most frequent ethnic groups were Caucasians and Asians. The most frequent clinical manifestations at onset were optic neuritis (ON), affecting 56% of adults, and acute disseminated encephalomyelitis (ADEM), affecting 33% of children. First MRI was abnormal in 84% of cases. Most CSF samples showed pleocytosis without oligoclonal bands. Two brain biopsies revealed lipid-laden macrophages and reactive astrocytes. Despite steroids, only 38% had fully recovered at 4 weeks after onset. Half of pediatric and two thirds of adult-onset MOGAD subjects experienced relapses. At last follow-up, 69% showed residual deficits, which were moderate to severe in 17% of adults.

CONCLUSION

MOGAD has heterogeneous disease course, and it is not a benign disease for a substantial proportion of adults. Best disease-modifying therapies remain to be determined.

Analysis of the microglia transcriptome across the human lifespan using single cell RNA sequencing

BACKGROUND

Microglia are tissue resident macrophages with a wide range of critically important functions in central nervous system development and homeostasis.

METHOD

In this study, we aimed to characterize the transcriptional landscape of ex vivo human microglia across different developmental ages using cells derived from pre-natal, pediatric, adolescent, and adult brain samples. We further confirmed our transcriptional observations using ELISA and RNAscope.

RESULTS

We showed that pre-natal microglia have a distinct transcriptional and regulatory signature relative to their post-natal counterparts that includes an upregulation of phagocytic pathways. We confirmed upregulation of CD36, a positive regulator of phagocytosis, in pre-natal samples compared to adult samples in situ. Moreover, we showed adult microglia have more pro-inflammatory signature compared to microglia from other developmental ages. We indicated that adult microglia are more immune responsive by secreting increased levels of pro-inflammatory cytokines in response to LPS treatment compared to the pre-natal microglia. We further validated in situ up-regulation of IL18 and CXCR4 in human adult brain section compared to the pre-natal brain section. Finally, trajectory analysis indicated that the transcriptional signatures adopted by microglia throughout development are in response to a changing brain microenvironment and do not reflect predetermined developmental states.

CONCLUSION

In all, this study provides unique insight into the development of human microglia and a useful reference for understanding microglial contribution to developmental and age-related human disease.

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.

Granulocyte-macrophage colony-stimulating factor-stimulated human macrophages demonstrate enhanced functions contributing to T-cell activation

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been implicated in numerous chronic inflammatory diseases, including multiple sclerosis (MS). GM-CSF impacts multiple properties and functions of myeloid cells via species-specific mechanisms. Therefore, we assessed the effect of GM-CSF on different human myeloid cell populations found in MS lesions: monocyte-derived macrophages (MDMs) and microglia. We previously reported a greater number of interleukin (IL)-15⁺ myeloid cells in the brain of patients with MS than in controls. Therefore, we investigated whether GM-CSF exerts its deleterious effects in MS by increasing IL-15 expression on myeloid cells. We found that GM-CSF increased the proportion of IL-15⁺ cells and/or IL-15 levels on nonpolarized, M1-polarized and M2-polarized MDMs from healthy donors and patients with MS. GM-CSF also increased IL-15 levels on human adult microglia. When cocultured with GM-CSF-stimulated MDMs, activated autologous CD8⁺ T lymphocytes secreted and expressed significantly higher levels of effector molecules (e.g. interferon-γ and GM-CSF) compared with cocultures with unstimulated MDMs. However, neutralizing IL-15 did not attenuate enhanced effector molecule expression on CD8⁺ T lymphocytes triggered by GM-CSF-stimulated MDMs. We showed that GM-CSF stimulation of MDMs increased their expression of CD80 and ICAM-1 and their secretion of IL-6, IL-27 and tumor necrosis factor. These molecules could participate in boosting the effector properties of CD8⁺ T lymphocytes independently of IL-15. By contrast, GM-CSF did not alter CD80, IL-27, tumor necrosis factor and chemokine (C-X-C motif) ligand 10 expression/secretion by human microglia. Therefore, our results underline the distinct impact of GM-CSF on human myeloid cells abundantly present in MS lesions.

Multiple sclerosis: 2023 update

Multiple sclerosis (MS) is the most frequent inflammatory and demyelinating disease of the Central Nervous System (CNS). Significant progress has been made during recent years in preventing relapses by using systemic immunomodulatory or immunosuppressive therapies. However, the limited effectiveness of such therapies for controlling the progressive disease course indicates there is a continuous disease progression independent of relapse activity which may start very early during the disease course. Dissecting the underlying mechanisms and developing therapies for preventing or stopping this disease progression represent, currently, the biggest challenges in the field of MS. Here, we summarize publications of 2022 which provide insight into susceptibility to MS, the basis of disease progression and features of relatively recently recognized distinct forms of inflammatory/demyelinating disorders of the CNS, such as myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD).

The White Matter Rounds experience: The importance of a multidisciplinary network to accelerate the diagnostic process for adult patients with rare white matter disorders

Introduction

Adult genetic leukoencephalopathies are rare neurological disorders that present unique diagnostic challenges due to their clinical and radiological overlap with more common white matter diseases, notably multiple sclerosis (MS). In this context, a strong collaborative multidisciplinary network is beneficial for shortening the diagnostic odyssey of these patients and preventing misdiagnosis. The White Matter Rounds (WM Rounds) are multidisciplinary international online meetings attended by more than 30 physicians and scientists from 15 participating sites that gather every month to discuss patients with atypical white matter disorders. We aim to present the experience of the WM Rounds Network and demonstrate the value of collaborative multidisciplinary international case discussion meetings in differentiating and preventing misdiagnoses between genetic white matter diseases and atypical MS.

Methods

We retrospectively reviewed the demographic, clinical and radiological data of all the subjects presented at the WM Rounds since their creation in 2013.

Results

Seventy-four patients (mean age 44.3) have been referred and discussed at the WM Rounds since 2013. Twenty-five (33.8%) of these patients were referred by an MS specialist for having an atypical presentation of MS, while in most of the remaining cases, the referring physician was a geneticist (23; 31.1%). Based on the WM Rounds recommendations, a definite diagnosis was made in 36/69 (52.2%) patients for which information was available for retrospective review. Of these diagnosed patients, 20 (55.6%) had a genetic disease, 8 (22.2%) had MS, 3 (8.3%) had both MS and a genetic disorder and 5 (13.9%) had other non-genetic conditions. Interestingly, among the patients initially referred by an MS specialist, 7/25 were definitively diagnosed with MS, 5/25 had a genetic condition (e.g., X-linked adrenoleukodystrophy and hereditary small vessel diseases like Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) and COL4A1-related disorder), and one had both MS and a genetic demyelinating neuropathy. Thanks to the WM Rounds collaborative efforts, the subjects who currently remain without a definite diagnosis, despite extensive investigations performed in the clinical setting, have been recruited in research studies aimed at identifying novel forms of genetic MS mimickers.

Conclusions

The experience of the WM Rounds Network demonstrates the benefit of collective discussions on complex cases to increase the diagnostic rate and decrease misdiagnosis in patients with rare or atypical white matter diseases. Networks of this nature allow physicians and scientists to compare and share information on challenging cases from across the world, provide a basis for future multicenter research studies, and serve as model for other rare diseases.

Contact-Dependent Granzyme B-Mediated Cytotoxicity of Th17-Polarized Cells Toward Human Oligodendrocytes

Multiple sclerosis (MS) is characterized by the loss of myelin and of myelin-producing oligodendrocytes (OLs) in the central nervous system (CNS). Pro-inflammatory CD4+ Th17 cells are considered pathogenic in MS and are harmful to OLs. We investigated the mechanisms driving human CD4+ T cell-mediated OL cell death. Using fluorescent and brightfield in vitro live imaging, we found that compared to Th2-polarized cells, Th17-polarized cells show greater interactions with primary human OLs and human oligodendrocytic cell line MO3.13, displaying longer duration of contact, lower mean speed, and higher rate of vesicle-like structure formation at the sites of contact. Using single-cell RNA sequencing, we assessed the transcriptomic profile of primary human OLs and Th17-polarized cells in direct contact or separated by an insert. We showed that upon close interaction, OLs upregulate the expression of mRNA coding for chemokines and antioxidant/anti-apoptotic molecules, while Th17-polarized cells upregulate the expression of mRNA coding for chemokines and pro-inflammatory cytokines such as IL-17A, IFN-γ, and granzyme B. We found that secretion of CCL3, CXCL10, IFN-γ, TNFα, and granzyme B is induced upon direct contact in cocultures of human Th17-polarized cells with human OLs. In addition, we validated by flow cytometry and immunofluorescence that granzyme B levels are upregulated in Th17-polarized compared to Th2-polarized cells and are even higher in Th17-polarized cells upon direct contact with OLs or MO3.13 cells compared to Th17-polarized cells separated from OLs by an insert. Moreover, granzyme B is detected in OLs and MO3.13 cells following direct contact with Th17-polarized cells, suggesting the release of granzyme B from Th17-polarized cells into OLs/MO3.13 cells. To confirm granzyme B–mediated cytotoxicity toward OLs, we showed that recombinant human granzyme B can induce OLs and MO3.13 cell death. Furthermore, pretreatment of Th17-polarized cells with a reversible granzyme B blocker (Ac-IEPD-CHO) or a natural granzyme B blocker (serpina3N) improved survival of MO3.13 cells upon coculture with Th17 cells. In conclusion, we showed that human Th17-polarized cells form biologically significant contacts with human OLs and exert direct toxicity by releasing granzyme B.

MicroRNA-210 regulates the metabolic and inflammatory status of primary human astrocytes

Background

Astrocytes are the most numerous glial cell type with important roles in maintaining homeostasis and responding to diseases in the brain. Astrocyte function is subject to modulation by microRNAs (miRs), which are short nucleotide strands that regulate protein expression in a post-transcriptional manner. Understanding the miR expression profile of astrocytes in disease settings provides insight into the cellular stresses present in the microenvironment and may uncover pathways of therapeutic interest.

Methods

Laser-capture microdissection was used to isolate human astrocytes surrounding stroke lesions and those from neurological control tissue. Astrocytic miR expression profiles were examined using quantitative reverse transcription polymerase chain reaction (RT-qPCR). Primary human fetal astrocytes were cultured under in vitro stress conditions and transfection of a miR mimic was used to better understand how altered levels of miR-210 affect astrocyte function. The astrocytic response to stress was studied using qPCR, enzyme-linked immunosorbent assays (ELISAs), measurement of released lactate, and Seahorse.

Results

Here, we measured miR expression levels in astrocytes around human ischemic stroke lesions and observed differential expression of miR-210 in chronic stroke astrocytes compared to astrocytes from neurological control tissue. We also identified increased expression of miR-210 in mouse white matter tissue around middle cerebral artery occlusion (MCAO) brain lesions. We aimed to understand the role of miR-210 in primary human fetal astrocytes by developing an in vitro assay of hypoxic, metabolic, and inflammatory stresses. A combination of hypoxic and inflammatory stresses was observed to upregulate miR-210 expression. Transfection with miR-210-mimic (210M) increased glycolysis, enhanced lactate export, and promoted an anti-inflammatory transcriptional and translational signature in astrocytes. Additionally, 210M transfection resulted in decreased expression of complement 3 (C3) and semaphorin 5b (Sema5b).

Conclusions

We conclude that miR-210 expression in human astrocytes is modulated in response to ischemic stroke disease and under in vitro stress conditions, supporting a role for miR-210 in the astrocytic response to disease conditions. Further, the anti-inflammatory and pro-glycolytic impact of miR-210 on astrocytes makes it a potential candidate for further research as a neuroprotective agent.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02373-y.

Pro-inflammatory T helper 17 directly harms oligodendrocytes in neuroinflammation

T helper (Th)17 cells are considered to contribute to inflammatory mechanisms in diseases such as multiple sclerosis (MS). However, the discussion persists regarding their true role in patients. Here, we visualized central nervous system (CNS) inflammatory processes in models of MS live in vivo and in MS brains and discovered that CNS-infiltrating Th17 cells form prolonged stable contact with oligodendrocytes. Strikingly, compared to Th2 cells, direct contact with Th17 worsened experimental demyelination, caused damage to human oligodendrocyte processes, and increased cell death. Importantly, we found that in comparison to Th2 cells, both human and murine Th17 cells express higher levels of the integrin CD29, which is linked to glutamate release pathways. Of note, contact of human Th17 cells with oligodendrocytes triggered release of glutamate, which induced cell stress and changes in biosynthesis of cholesterol and lipids, as revealed by single-cell RNA-sequencing analysis. Finally, exposure to glutamate decreased myelination, whereas blockade of CD29 preserved oligodendrocyte processes from Th17-mediated injury. Our data provide evidence for the direct and deleterious attack of Th17 cells on the myelin compartment and show the potential for therapeutic opportunities in MS.

Size and ligand effects of gold nanoclusters in alteration of organellar state and translocation of transcription factors in human primary astrocytes

Ultra-small gold nanoclusters (AuNCs) with designed sizes and ligands are gaining popularity for biomedical purposes and ultimately for human imaging and therapeutic applications. Human non-tumor brain cells, astrocytes, are of particular interest because they are abundant and play a role in functional regulation of neurons under physiological and pathological conditions. Human primary astrocytes were treated with AuNCs of varying sizes (Au10, Au15, Au18, Au25) and ligand composition (glutathione, polyethylene glycol, N-acetyl cysteine). Concentration and time-dependent studies showed no significant cell loss with AuNC concentrations <10 μM. AuNC treatment caused marked differential astrocytic responses at the organellar and transcription factor level. The effects were exacerbated under severe oxidative stress induced by menadione. Size-dependent effects were most remarkable with the smallest and largest AuNCs (10, 15 Au atoms versus 25 Au atoms) and might be related to the accessibility of biological targets toward the AuNC core, as demonstrated by QM/MM simulations. In summary, these findings suggest that AuNCs are not inert in primary human astrocytes, and that their sizes play a critical role in modulation of organellar and redox-responsive transcription factor homeostasis.

Transcriptomic and clonal characterization of T cells in the human central nervous system

T cells provide critical immune surveillance to the central nervous system (CNS), and the cerebrospinal fluid (CSF) is thought to be a main route for their entry. Further characterization of the state of T cells in the CSF in healthy individuals is important for understanding how T cells provide protective immune surveillance without damaging the delicate environment of the CNS and providing tissue-specific context for understanding immune dysfunction in neuroinflammatory disease. Here, we have profiled T cells in the CSF of healthy human donors and have identified signatures related to cytotoxic capacity and tissue adaptation that are further exemplified in clonally expanded CSF T cells. By comparing profiles of clonally expanded T cells obtained from the CSF of patients with multiple sclerosis (MS) and healthy donors, we report that clonally expanded T cells from the CSF of patients with MS have heightened expression of genes related to T cell activation and cytotoxicity.

Multiple Sclerosis as a Syndrome-Implications for Future Management

We propose that multiple sclerosis (MS) is best characterized as a syndrome rather than a single disease because different pathogenetic mechanisms can result in the constellation of symptoms and signs by which MS is clinically characterized. We describe several cellular mechanisms that could generate inflammatory demyelination through disruption of homeostatic interactions between immune and neural cells. We illustrate that genomics is important in identifying phenocopies, in particular for primary progressive MS. We posit that molecular profiling, rather than traditional clinical phenotyping, will facilitate meaningful patient stratification, as illustrated by interactions between HLA and a regulator of homeostatic phagocytosis, MERTK. We envisage a personalized approach to MS management where genetic, molecular, and cellular information guides management.

Single-cell RNA-seq reveals that glioblastoma recapitulates a normal neurodevelopmental hierarchy

Cancer stem cells are critical for cancer initiation, development, and treatment resistance. Our understanding of these processes, and how they relate to glioblastoma heterogeneity, is limited. To overcome these limitations, we performed single-cell RNA sequencing on 53586 adult glioblastoma cells and 22637 normal human fetal brain cells, and compared the lineage hierarchy of the developing human brain to the transcriptome of cancer cells. We find a conserved neural tri-lineage cancer hierarchy centered around glial progenitor-like cells. We also find that this progenitor population contains the majority of the cancer's cycling cells, and, using RNA velocity, is often the originator of the other cell types. Finally, we show that this hierarchal map can be used to identify therapeutic targets specific to progenitor cancer stem cells. Our analyses show that normal brain development reconciles glioblastoma development, suggests a possible origin for glioblastoma hierarchy, and helps to identify cancer stem cell-specific targets.

Vitamin D Regulates MerTK-Dependent Phagocytosis in Human Myeloid Cells

Vitamin D deficiency is a major environmental risk factor for the development of multiple sclerosis. The major circulating metabolite of vitamin D (25-hydroxyvitamin D) is converted to the active form (calcitriol) by the hydroxylase enzyme CYP27B1 In multiple sclerosis lesions, the tyrosine kinase MerTK expressed by myeloid cells regulates phagocytosis of myelin debris and apoptotic cells that can accumulate and inhibit tissue repair and remyelination. In this study, we explored the effect of calcitriol on homeostatic (M-CSF, TGF-β-treated) and proinflammatory (GM-CSF-treated) human monocyte-derived macrophages and microglia using RNA sequencing. Transcriptomic analysis revealed significant calcitriol-mediated effects on both Ag presentation and phagocytosis pathways. Calcitriol downregulated MerTK mRNA and protein expression in both myeloid populations, resulting in reduced capacity of these cells to phagocytose myelin and apoptotic T cells. Proinflammatory myeloid cells expressed high levels of CYP27B1 compared with homeostatic myeloid cells. Only proinflammatory cells in the presence of TNF-α generated calcitriol from 25-hydroxyvitamin D, resulting in repression of MerTK expression and function. This selective production of calcitriol in proinflammatory myeloid cells has the potential to reduce the risk for autoantigen presentation while retaining the phagocytic ability of homeostatic myeloid cells.

Effects of Biotin on survival, ensheathment, and ATP production by oligodendrocyte lineage cells in vitro

Mechanisms implicated in disease progression in multiple sclerosis include continued oligodendrocyte (OL)/myelin injury and failure of myelin repair. Underlying causes include metabolic stress with resultant energy deficiency. Biotin is a cofactor for carboxylases involved in ATP production that impact myelin production by promoting fatty acid synthesis. Here, we investigate the effects of high dose Biotin (MD1003) on the functional properties of post-natal rat derived oligodendrocyte progenitor cells (OPCs). A2B5 positive OPCs were assessed using an in vitro injury assay, culturing cells in either DFM (DMEM/F12+N1) or “stress media” (no glucose (NG)-DMEM), with Biotin added over a range from 2.5 to 250 μg/ml, and cell viability determined after 24 hrs. Biotin reduced the increase in OPC cell death in the NG condition. In nanofiber myelination assays, biotin increased the percentage of ensheathing cells, the number of ensheathed segments per cell, and length of ensheathed segments. In dispersed cell culture, Biotin also significantly increased ATP production, assessed using a Seahorse bio-analyzer. For most assays, the positive effects of Biotin were observed at the higher end of the dose-response analysis. We conclude that Biotin, in vitro, protects OL lineage cells from metabolic injury, enhances myelin-like ensheathment, and is associated with increased ATP production.

Extensive subpial cortical demyelination is specific to multiple sclerosis

Cortical demyelinated lesions are frequent and widespread in chronic multiple sclerosis (MS) patients, and may contribute to disease progression. Inflammation and related oxidative stress have been proposed as central mediators of cortical damage, yet meningeal and cortical inflammation is not specific to MS, but also occurs in other diseases. The first aim of this study was to test whether cortical demyelination was specific for demyelinating CNS diseases compared to other CNS disorders with prominent meningeal and cortical inflammation. The second aim was to assess whether oxidative tissue damage was associated with the extent of neuroaxonal damage. We studied a large cohort of patients diagnosed with demyelinating CNS diseases and non‐demyelinating diseases of autoimmune, infectious, neoplastic or metabolic origin affecting the meninges and the cortex. Included were patients with MS, acute disseminated encephalomyelitis (ADEM), neuromyelitis optica (NMO), viral and bacterial meningoencephalitis, progressive multifocal leukoencephalopathy (PML), subacute sclerosing panencephalitis (SSPE), carcinomatous and lymphomatous meningitis and metabolic disorders such as extrapontine myelinolysis, thus encompassing a wide range of adaptive and innate cytokine signatures. Using myelin protein immunohistochemistry, we found cortical demyelination in MS, ADEM, PML and extrapontine myelinolysis, whereby each condition showed a disease‐specific histopathological pattern. Remarkably, extensive ribbon‐like subpial demyelination was only observed in MS, thus providing an important pathogenetic and diagnostic cue. Cortical oxidative injury was detected in both demyelinating and non‐demyelinating CNS disorders. Our data demonstrate that meningeal and cortical inflammation alone accompanied by oxidative stress are not sufficient to generate the extensive subpial cortical demyelination found in MS, but require other MS‐specific factors.

Pre-treatment T-cell subsets associate with fingolimod treatment responsiveness in multiple sclerosis

Biomarkers predicting fingolimod (FTY) treatment response in relapsing-remitting multiple sclerosis (RRMS) are lacking. Here, we performed extensive functional immunophenotyping using multiparametric flow cytometry to examine peripheral immune changes under FTY treatment and explore biomarkers of FTY treatment response. From among 135 RRMS patients who initiated FTY in a 2-year multicentre observational study, 36 were classified as ‘Active’ or ‘Stable’ based on clinical and/or radiological activity on-treatment. Flow cytometric analysis of immune cell subsets was performed on pre- and on-treatment peripheral blood mononuclear cells (PBMC) samples. Decreased absolute counts of B cells and most T-cell subsets were seen on-treatment. Senescent CD8 + T cells, CD56 + T cells, CD56^dim natural killer cells, monocytes and dendritic cells were not reduced in number and hence relatively increased in frequency on-treatment. An unbiased multiparametric and traditional manual analysis of T-cell subsets suggested a higher pre-treatment frequency of CD4 + central memory T cells (TCM) in patients who were subsequently Active versus Stable on-treatment. Lower pre-treatment terminally differentiated effector memory (TEMRA) cell frequencies were also seen in the subsequently Active cohort. Together, our data highlight differential effects of FTY on peripheral immune cell subsets and suggest that pre-treatment T-cell subset frequencies may have value in predicting FTY treatment response.

Author Correction: Control of tumor-associated macrophages and T cells in glioblastoma via AHR and CD39

In the version of this article initially published, author Alexandre Prat's surname was misspelled. The error has been corrected in the HTML and PDF versions of the article.

Americas Committee for Treatment and Research in Multiple Sclerosis Forum 2017: Environmental factors, genetics, and epigenetics in MS susceptibility and clinical course

The Americas Committee for Treatment and Research in Multiple Sclerosis (ACTRIMS) Forum 2017 brought together a multidisciplinary team of basic and clinical researchers to discuss the impact of environmental, genetic, and epigenetic factors on multiple sclerosis (MS) susceptibility and clinical course. The series of articles in this special edition reflect the breadth and depth of the topics that were discussed.

Control of tumor-associated macrophages and T cells in glioblastoma via AHR and CD39

Tumor-associated macrophages (TAMs) play an important role in the immune response to cancer, but the mechanisms by which the tumor microenvironment controls TAMs and T cell immunity are not completely understood. Here we report that kynurenine produced by glioblastoma cells activates aryl hydrocarbon receptor (AHR) in TAMs to modulate their function and T cell immunity. AHR promotes CCR2 expression, driving TAM recruitment in response to CCL2. AHR also drives the expression of KLF4 and suppresses NF-κB activation in TAMs. Finally, AHR drives the expression of the ectonucleotidase CD39 in TAMs, which promotes CD8⁺ T cell dysfunction by producing adenosine in cooperation with CD73. In humans, the expression of AHR and CD39 was highest in grade 4 glioma, and high AHR expression was associated with poor prognosis. In summary, AHR and CD39 expressed in TAMs participate in the regulation of the immune response in glioblastoma and constitute potential targets for immunotherapy.

Microglial control of astrocytes in response to microbial metabolites

Microglia and astrocytes modulate inflammation and neurodegeneration in the central nervous system (CNS)^1-3. Microglia modulate pro-inflammatory and neurotoxic activities in astrocytes, but the mechanisms involved are not completely understood^4,5. Here we report that TGFα and VEGF-B produced by microglia regulate the pathogenic activities of astrocytes in the experimental autoimmune encephalomyelitis (EAE) mouse model of multiple sclerosis. Microglia-derived TGFα acts via the ErbB1 receptor in astrocytes to limit their pathogenic activities and EAE development. Conversely, microglial VEGF-B triggers FLT-1 signalling in astrocytes and worsens EAE. VEGF-B and TGFα also participate in the microglial control of human astrocytes. Furthermore, expression of TGFα and VEGF-B in CD14⁺ cells correlates with the multiple sclerosis lesion stage. Finally, metabolites of dietary tryptophan produced by the commensal flora control microglial activation and TGFα and VEGF-B production, modulating the transcriptional program of astrocytes and CNS inflammation through a mechanism mediated by the aryl hydrocarbon receptor. In summary, we identified positive and negative regulators that mediate the microglial control of astrocytes. Moreover, these findings define a pathway through which microbial metabolites limit pathogenic activities of microglia and astrocytes, and suppress CNS inflammation. This pathway may guide new therapies for multiple sclerosis and other neurological disorders.

Reconstitution of the peripheral immune repertoire following withdrawal of fingolimod

BACKGROUND

Following fingolimod cessation, immune reconstitution or lack thereof may have consequences for disease rebound or safety of commencing alternative therapies.

OBJECTIVE

To examine the degree and profile of peripheral blood lymphocyte reconstitution following fingolimod withdrawal.

METHODS

Total lymphocyte counts (TLC) and CD4+/CD8+ T-cell counts were measured in 18 multiple sclerosis (MS) patients pre-treatment, on fingolimod, and up to 8-9 months post-cessation. T-cell subsets were analyzed using flow cytometry.

RESULTS

At 2-week post-fingolimod cessation, TLC reconstitution was variable and not correlated with age, treatment duration, pre-, or on-treatment TLC. Despite normalization of TLC and CD4+:CD8+ ratios over months, naive subsets remained lower and effector memory subsets higher in frequency compared with pre-treatment. Drug-induced increases in ratios of regulatory to pathogenic Th17-containing central memory populations appeared to rapidly return to baseline.

CONCLUSION

Early peripheral lymphocyte reconstitution after fingolimod withdrawal remains partial and heterogeneous. Relative frequencies of circulating naive and memory T-cell subsets may not recover for many months, even when clinical laboratory tests have normalized. Analyzing specific components of the peripheral immune repertoire helps define the overall immune status of patients. To be determined is whether assessment of such immune measures will have implications for the timing and safety of commencing alternative therapies.

The role of MRI as a surrogate outcome measure in multiple sclerosis

The need for more specific and more sensitive outcome measures for use in testing new therapies in multiple sclerosis (MS) is generally accepted. This need has been accentuated by the realization that the ability to conduct large placebo-controlled trials will be limited in the future. From the first use of magnetic resonance imaging (MRI) to study MS, the ability of this imaging technique to identify areas of the central nervous system damage by the disease process in MS has been impressive. Thus, the possibility that MRI could serve as a surrogate outcome measure in clinical trials in MS has been attractive. The use of MRI as a surrogate outcome measure has been examined by an international group of investigators with expertise in clinical aspects of MS, the use of MRI in MS, and in experimental therapeutics. The group agreed that MRI does not represent a validated surrogate in any clinical form of MS. It was also agreed, however, that MRI does provide a reflection of the underlying pathology in the disease, but no single MRI measurement in isolation was seen as sufficient to monitor disease. The use for multiple imaging techniques, especially new, emerging techniques that may better reflect the underlying pathology, was seen as particularly important in monitoring studies of patients with either secondary or primary progressive MS. The choice of MRI techniques used to monitor new therapies needs to be consistent with the proposed mechanisms of the new therapy and phase of the disease. It was also noted, however, that additional validation is required for nonconventional imaging techniques. Finally, the participants noted that clinical trials using MRI as a primary outcome measure may fail to fully identify the effects of the therapy on clinical measures and that the risk and cost-benefit ratio of the treatment might be unresolved. Thus, before MRI is used as a primary outcome measure, new approaches to trial design must be given careful consideration. Multiple Sclerosis (2002)8, 40-51

Small-Molecule Stabilization of 14-3-3 Protein-Protein Interactions Stimulates Axon Regeneration

Damaged central nervous system (CNS) neurons have a poor ability to spontaneously regenerate, causing persistent functional deficits after injury. Therapies that stimulate axon growth are needed to repair CNS damage. 14-3-3 adaptors are hub proteins that are attractive targets to manipulate cell signaling. We identify a positive role for 14-3-3s in axon growth and uncover a developmental regulation of the phosphorylation and function of 14-3-3s. We show that fusicoccin-A (FC-A), a small-molecule stabilizer of 14-3-3 protein-protein interactions, stimulates axon growth in vitro and regeneration in vivo. We show that FC-A stabilizes a complex between 14-3-3 and the stress response regulator GCN1, inducing GCN1 turnover and neurite outgrowth. These findings show that 14-3-3 adaptor protein complexes are druggable targets and identify a new class of small molecules that may be further optimized for the repair of CNS damage.

Dimethyl fumarate-induced lymphopenia in MS due to differential T-cell subset apoptosis

Objective:

To examine the mechanism underlying the preferential CD8⁺ vs CD4⁺ T-cell lymphopenia induced by dimethyl fumarate (DMF) treatment of MS.

Methods:

Total lymphocyte counts and comprehensive T-cell subset analyses were performed in high-quality samples obtained from patients with MS prior to and serially following DMF treatment initiation. Random coefficient mixed-effects analysis was used to model the trajectory of T-cell subset losses in vivo. Survival and apoptosis of distinct T-cell subsets were assessed following in vitro exposure to DMF.

Results:

Best-fit modeling indicated that the DMF-induced preferential reductions in CD8⁺ vs CD4⁺ T-cell counts nonetheless followed similar depletion kinetics, suggesting a similar rather than distinct mechanism involved in losses of both the CD8⁺ and CD4⁺ T cells. In vitro, DMF exposure resulted in dose-dependent reductions in T-cell survival, which were found to reflect apoptotic cell death. This DMF-induced apoptosis was greater for CD8⁺ vs CD4⁺, as well as for memory vs naive, and conventional vs regulatory T-cell subsets, a pattern which mirrored preferential T-cell subset losses that we observed during in vivo treatment of patients.

Conclusions:

Differential apoptosis mediated by DMF may underlie the preferential lymphopenia of distinct T-cell subsets, including CD8⁺ and memory T-cell subsets, seen in treated patients with MS. This differential susceptibility of distinct T-cell subsets to DMF-induced apoptosis may contribute to both the safety and efficacy profiles of DMF in patients with MS.

[Nutrition and mental diseases : Focus depressive disorders]

Dietary interventions are currently being discussed as additional treatment options for mental disorders. The pathological mechanisms are not yet fully understood. It is hypothesized that certain nutrients and dietary pattern influence immune and inflammatory processes, the microbiome, the leptin-melanocortinergic axis and hypothalamic-pituitary axis, as well as neurotransmitters of the cholinergic, noradrenergic, dopaminergic and serotonergic signaling cascades and neurotrophins. Observational studies have shown that traditional dietary patterns, such as the Mediterranean diet have a protective effect on mental health. Supplementation with long-chain polyunsaturated omega-3 fatty acids showed small to medium but significant effect sizes in meta-analyses from depression trials. The evidence with respect to the antidepressive effect of vitamin D supplementation is currently inconclusive.

Evidence for three genetic loci involved in both anorexia nervosa risk and variation of body mass index

The maintenance of normal body weight is disrupted in patients with anorexia nervosa (AN) for prolonged periods of time. Prior to the onset of AN, premorbid body mass index (BMI) spans the entire range from underweight to obese. After recovery, patients have reduced rates of overweight and obesity. As such, loci involved in body weight regulation may also be relevant for AN and vice versa. Our primary analysis comprised a cross-trait analysis of the 1000 single-nucleotide polymorphisms (SNPs) with the lowest P-values in a genome-wide association meta-analysis (GWAMA) of AN (GCAN) for evidence of association in the largest published GWAMA for BMI (GIANT). Subsequently we performed sex-stratified analyses for these 1000 SNPs. Functional ex vivo studies on four genes ensued. Lastly, a look-up of GWAMA-derived BMI-related loci was performed in the AN GWAMA. We detected significant associations (P-values <5 × 10-5, Bonferroni-corrected P<0.05) for nine SNP alleles at three independent loci. Interestingly, all AN susceptibility alleles were consistently associated with increased BMI. None of the genes (chr. 10: CTBP2, chr. 19: CCNE1, chr. 2: CARF and NBEAL1; the latter is a region with high linkage disequilibrium) nearest to these SNPs has previously been associated with AN or obesity. Sex-stratified analyses revealed that the strongest BMI signal originated predominantly from females (chr. 10 rs1561589; Poverall: 2.47 × 10-06/Pfemales: 3.45 × 10-07/Pmales: 0.043). Functional ex vivo studies in mice revealed reduced hypothalamic expression of Ctbp2 and Nbeal1 after fasting. Hypothalamic expression of Ctbp2 was increased in diet-induced obese (DIO) mice as compared with age-matched lean controls. We observed no evidence for associations for the look-up of BMI-related loci in the AN GWAMA. A cross-trait analysis of AN and BMI loci revealed variants at three chromosomal loci with potential joint impact. The chromosome 10 locus is particularly promising given that the association with obesity was primarily driven by females. In addition, the detected altered hypothalamic expression patterns of Ctbp2 and Nbeal1 as a result of fasting and DIO implicate these genes in weight regulation.

An updated histological classification system for multiple sclerosis lesions

Multiple sclerosis is a complex and heterogeneous, most likely autoimmune, demyelinating disease of the central nervous system (CNS). Although a number of histological classification systems for CNS lesions have been used by different groups in recent years, no uniform classification exists. In this paper, we propose a simple and unifying classification of MS lesions incorporating many elements of earlier histological systems that aims to provide guidelines for neuropathologists and researchers studying MS lesions to allow for better comparison of different studies performed with MS tissue, and to aid in understanding the pathogenesis of the disease. Based on the presence/absence and distribution of macrophages/microglia (inflammatory activity) and the presence/absence of ongoing demyelination (demyelinating activity), we suggest differentiating between active, mixed active/inactive, and inactive lesions with or without ongoing demyelination. Active lesions are characterized by macrophages/microglia throughout the lesion area, whereas mixed active/inactive lesions have a hypocellular lesion center with macrophages/microglia limited to the lesion border. Inactive lesions are almost completely lacking macrophages/microglia. Active and mixed active/inactive lesions can be further subdivided into lesions with ongoing myelin destruction (demyelinating lesions) and lesions in which the destruction of myelin has ceased, but macrophages are still present (post-demyelinating lesions). This distinction is based on the presence or absence of myelin degradation products within the cytoplasm of macrophages/microglia. For this classification of MS lesions, identification of myelin with histological stains [such as luxol fast blue-PAS] or by immunohistochemistry using antibodies against myelin basic-protein (MBP) or proteolipid-protein (PLP), as well as, detection of macrophages/microglia by, e.g., anti-CD68 is sufficient. Active and demyelinating lesions may be further subdivided into the early and late demyelinating lesions. The former is defined by the presence in macrophages of major and small molecular weight myelin proteins, such as cyclic nucleotide diphosphoesterase (CNP), myelin oligodendrocyte glycoprotein (MOG), or myelin-associated protein (MAG), whereas macrophages in the latter demonstrate merely the presence of the major myelin proteins MBP or PLP. We discuss the histological features and staining techniques required to classify MS lesions, and, in addition, describe the histological hallmarks of cortical pathology and diffuse white matter changes, as well as of remyelination.

Dimethyl Fumarate Treatment Mediates an Anti-Inflammatory Shift in B Cell Subsets of Patients with Multiple Sclerosis

The therapeutic mode of action of dimethyl fumarate (DMF), approved for treating patients with relapsing-remitting multiple sclerosis, is not fully understood. Recently, we and others demonstrated that Ab-independent functions of distinct B cell subsets are important in mediating multiple sclerosis (MS) relapsing disease activity. Our objective was to test whether and how DMF influences both the phenotype and functional responses of disease-implicated B cell subsets in patients with MS. High-quality PBMC were obtained from relapsing-remitting MS patients prior to and serially after initiation of DMF treatment. Multiparametric flow cytometry was used to monitor the phenotype and functional response-profiles of distinct B cell subsets. Total B cell counts decreased following DMF treatment, largely reflecting losses of circulating mature/differentiated (but not of immature transitional) B cells. Within the mature B cell pool, DMF had a greater impact on memory than naive B cells. In keeping with these in vivo effects, DMF treatment in vitro remarkably diminished mature (but not transitional B cell) survival, mediated by inducing apoptotic cell death. Although DMF treatment (both in vivo and in vitro) minimally impacted B cell IL-10 expression, it strongly reduced B cell expression of GM-CSF, IL-6, and TNF-α, resulting in a significant anti-inflammatory shift of B cell response profiles. The DMF-mediated decrease in B cell proinflammatory cytokine responses was further associated with reduced phosphorylation of STAT5/6 and NF-κB in surviving B cells. Together, these data implicate novel mechanisms by which DMF may modulate MS disease activity through shifting the balance between pro- and anti-inflammatory B cell responses.

Type I interferons and microbial metabolites of tryptophan modulate astrocyte activity and central nervous system inflammation via the aryl hydrocarbon receptor

Astrocytes have important roles in the central nervous system (CNS) during health and disease. Through genome-wide analyses we detected a transcriptional response to type I interferons (IFN-Is) in astrocytes during experimental CNS autoimmunity and also in CNS lesions from patients with multiple sclerosis (MS). IFN-I signaling in astrocytes reduces inflammation and experimental autoimmune encephalomyelitis (EAE) disease scores via the ligand-activated transcription factor aryl hydrocarbon receptor (AHR) and the suppressor of cytokine signaling 2 (SOCS2). The anti-inflammatory effects of nasally administered interferon (IFN)-β are partly mediated by AHR. Dietary tryptophan is metabolized by the gut microbiota into AHR agonists that have an effect on astrocytes to limit CNS inflammation. EAE scores were increased following ampicillin treatment during the recovery phase, and CNS inflammation was reduced in antibiotic-treated mice by supplementation with the tryptophan metabolites indole, indoxyl-3-sulfate, indole-3-propionic acid and indole-3-aldehyde, or the bacterial enzyme tryptophanase. In individuals with MS, the circulating levels of AHR agonists were decreased. These findings suggest that IFN-Is produced in the CNS function in combination with metabolites derived from dietary tryptophan by the gut flora to activate AHR signaling in astrocytes and suppress CNS inflammation.

Are bidirectional associations of obesity and depression already apparent in childhood and adolescence as based on high-quality studies? A systematic review

Our aim was to evaluate bidirectional associations of obesity and depression in cross-sectional and longitudinal studies with initial assessments in childhood or adolescence. The clarification of these relationships may support the development of innovative interventions, e.g. based on nutrition and mental health. A systematic literature search was conducted in MEDLINE. Main inclusion criteria were (i) assessment of subjects <18 years at baseline, (ii) use of validated psychometric instruments and (iii) elicitation of objectively measured anthropometric data at least at one time point. Twenty-four studies met our inclusion criteria. Out of 19, 14 cross-sectional studies confirmed a significant association of obesity and depression. Three out of eight longitudinal studies reported associations between obesity and subsequent depression in female children and adolescents only, and three out of nine studies obtained evidence in favour of the other direction with two studies revealing significant results only for female and one only for male children and adolescents. Evidence is mixed, and secure conclusions are hampered by the methodological variance of the included studies. Relationships are seemingly more readily detectable in female children adolescents and in the cross-sectional compared with the longitudinal analyses. Possibly, the joint development of obesity and depression in predisposed subjects accounts for the latter discrepancy.

CXCR7 Is Involved in Human Oligodendroglial Precursor Cell Maturation

Differentiation of oligodendroglial precursor cells (OPCs), a crucial prerequisite for central nervous system (CNS) remyelination in diseases such as Multiple Sclerosis (MS), is modulated by a multitude of extrinsic and intrinsic factors. In a previous study we revealed that the chemokine CXCL12 stimulates rodent OPC differentiation via activation of its receptor CXCR7. We could now demonstrate that CXCR7 is also expressed on NogoA- and Nkx2.2-positive oligodendroglial cells in human MS brains and that stimulation of cultured primary fetal human OPCs with CXCL12 promotes their differentiation as measured by surface marker expression and morphologic complexity. Pharmacological inhibition of CXCR7 effectively blocks these CXCL12-dependent effects. Our findings therefore suggest that a specific activation of CXCR7 could provide a means to promote oligodendroglial differentiation facilitating endogenous remyelination activities.