Immune reactivity to neurofilament proteins in the clinical staging of amyotrophic lateral sclerosis

The presence and clinical significance of autoantibodies in amyotrophic lateral sclerosis: a narrative review

Amyotrophic lateral sclerosis (ALS) is a debilitating and rapidly fatal neurodegenerative disease, which is characterized by the selective loss of the upper and lower motor neurons. The pathogenesis of ALS remains to be elucidated and has been connected to genetic, environmental and immune conditions. Evidence from clinical and experimental studies has suggested that the immune system played an important role in ALS pathophysiology. Autoantibodies are essential components of the immune system. Several autoantibodies directed at antigens associated with ALS pathogenesis have been identified in the serum and/or cerebrospinal fluid of ALS patients. The aim of this review is to summarize the presence and clinical significance of autoantibodies in ALS.

Role of Specific Autoantibodies in Neurodegenerative Diseases: Pathogenic Antibodies or Promising Biomarkers for Diagnosis

Neurodegenerative diseases (NDDs) affect millions of people worldwide. They develop due to the pathological accumulation and aggregation of various misfolded proteins, axonal and synaptic loss and dysfunction, inflammation, cytoskeletal abnormalities, defects in DNA and RNA, and neuronal death. This leads to the activation of immune responses and the release of the antibodies against them. Recently, it has become clear that autoantibodies (Aabs) can contribute to demyelination, axonal loss, and brain and cognitive dysfunction. This has significantly changed the understanding of the participation of humoral autoimmunity in neurodegenerative disorders. It is crucial to understand how neuroinflammation is involved in neurodegeneration, to aid in improving the diagnostic and therapeutic value of Aabs in the future. This review aims to provide data on the immune system's role in NDDs, the pathogenic role of some specific Aabs against molecules associated with the most common NDDs, and their potential role as biomarkers for monitoring and diagnosing NDDs. It is suggested that the autoimmune aspects of NDDs will facilitate early diagnosis and help to elucidate previously unknown aspects of the pathobiology of these diseases.

Senescent-like Blood Lymphocytes and Disease Progression in Amyotrophic Lateral Sclerosis

BACKGROUND AND OBJECTIVES

Aging is known to exacerbate neuroinflammation, and in the neurodegenerative disorder amyotrophic lateral sclerosis (ALS), an older age is associated with a worse prognosis. We have previously shown the activation of cell senescence pathways in the proteome of peripheral blood mononuclear cells and the increase of proinflammatory cytokines in blood from individuals living with ALS. In this single-center, retrospective study, we investigated the expression of senescent-like blood mononuclear cells in ALS.

METHODS

We first applied multidimensional cytometry by time-of-flight (CyTOF) to study the senescent immunophenotype of blood mononuclear cells from 21 patients with ALS and 10 healthy controls (HCs). We then used targeted flow cytometry (FC) to investigate frequencies of senescent blood lymphocytes in 40 patients with ALS and 20 HCs. Longitudinal analysis included 2 additional time points in 17 patients with ALS. Frequencies of senescent-like lymphocytes were analyzed in relation to survival.

RESULTS

Unsupervised clustering of CyTOF data showed higher frequencies of senescent CD4+CD27-CD57+ T cells in patients with ALS compared with those in HCs (p = 0.0017, false discovery (FDR)-adjusted p = 0.029). Moderate to strong negative correlations were identified between CD4 T central memory-cell frequencies and survival (R = -061, p = 0.01; FDR-adjusted p < 0.1) and between CD95 CD8 cells and ALS functional rating scale revised at baseline (R = -0.72, p = 0.001; FDR-adjusted p < 0.1).Targeted FC analysis showed higher memory T regulatory cells (p = 0.0052) and memory CD8+ T cell (M-Tc; p = 0.0006) in bulbar ALS (A-B) compared with those in limb ALS (A-L), while late memory B cells (LM-B) were also elevated in A-B and fast-progressing ALS (p = 0.0059). Higher M-Tc levels separated A-B from A-L (AUC: 0.887; p < 0.0001). A linear regression model with prespecified clinical independent variables and neurofilament light chain plasma concentration showed that higher frequencies of LM-B predicted a shorter survival (hazard ratio: 1.094, CI: 1.026-1.167; p = 0.006).

DISCUSSION

Our data suggest that a systemic elevation of senescent and late memory T and B lymphocytes is a feature of faster progressing ALS and of ALS individuals with bulbar involvement. Lymphocyte senescence and their memory state may be central to the immune dysregulation known to drive disease progression in ALS and a target for biomarkers and therapeutics discovery.

Blood biomarkers in ALS: challenges, applications and novel frontiers

Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disease among adults. With diagnosis reached relatively late into the disease process, extensive motor cell loss narrows the window for therapeutic opportunities. Clinical heterogeneity in ALS and the lack of disease-specific biomarkers have so far led to large-sized clinical trials with long follow-up needed to define clinical outcomes. In advanced ALS patients, there is presently limited scope to use imaging or invasive cerebrospinal fluid (CSF) collection as a source of disease biomarkers. The development of more patient-friendly and accessible blood biomarker assays is hampered by analytical hurdles like the matrix effect of blood components. However, blood also provides the opportunity to identify disease-specific adaptive changes of the stoichiometry and conformation of target proteins and the endogenous immunological response to low-abundance brain peptides, such as neurofilaments (Nf). Among those biomarkers under investigation in ALS, the change in concentration before or after diagnosis of Nf has been shown to aid prognostication and to allow the a priori stratification of ALS patients into smaller sized and clinically more homogeneous cohorts, supporting more affordable clinical trials. Here, we discuss the technical hurdles affecting reproducible and sensitive biomarker measurement in blood. We also summarize the state of the art of non-CSF biomarkers in the study of prognosis, disease progression, and treatment response. We will then address the potential as disease-specific biomarkers of the newly discovered cryptic peptides which are formed down-stream of TDP-43 loss of function, the hallmark of ALS pathobiology.

Serum Neurofilament Light Chain Levels May Be a Marker of Lower Motor Neuron Damage in Amyotrophic Lateral Sclerosis

Objectives The aims of this study were to investigate whether serum neurofilament light chain (NfL) levels were correlated with the severity of the axonal degeneration of lower motor neurons (LMNs) in the early symptomatic phase of amyotrophic lateral sclerosis (ALS). Methods In this prospective study, the serum samples used for NfL measurement were obtained from 103 sporadic ALS outpatients within 2 years of disease duration. The severity of axonal degeneration was assessed by assessing the decrease in the compound muscle action potentials (CMAPs) within a 1-month interval from serum sampling. Results The NfL levels showed a significant positive correlation with the relative score as a proxy for the axonal damage of LMNs in patients with ALS (coefficient: 0.264, p = 0.009). Furthermore, this correlation became stronger (coefficient: 0.582, p = 0.037) when estimated only among patients with disease subtypes that involve only LMNs, that is, patients with flail arm or leg syndrome (FAS or FLS). The levels of NfL increased with the severity of axonal damage of LMNs (F = 6.694, P = 0.0001). Conclusions Serum NfL levels mirrored the severity of the axonal degeneration of LMNs, particularly in patients with signs of predominant LMN involvement. These results may have a profound effect on the selection of patients and the monitoring of treatment efficacy in future disease-modifying clinical trials.

Neuroinflammation in Amyotrophic Lateral Sclerosis and Frontotemporal Dementia and the Interest of Induced Pluripotent Stem Cells to Study Immune Cells Interactions With Neurons

Inflammation is a shared hallmark between amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). For long, studies were conducted on tissues of post-mortem patients and neuroinflammation was thought to be only bystander result of the disease with the immune system reacting to dying neurons. In the last two decades, thanks to improving technologies, the identification of causal genes and the development of new tools and models, the involvement of inflammation has emerged as a potential driver of the diseases and evolved as a new area of intense research. In this review, we present the current knowledge about neuroinflammation in ALS, ALS-FTD, and FTD patients and animal models and we discuss reasons of failures linked to therapeutic trials with immunomodulator drugs. Then we present the induced pluripotent stem cell (iPSC) technology and its interest as a new tool to have a better immunopathological comprehension of both diseases in a human context. The iPSC technology giving the unique opportunity to study cells across differentiation and maturation times, brings the hope to shed light on the different mechanisms linking neurodegeneration and activation of the immune system. Protocols available to differentiate iPSC into different immune cell types are presented. Finally, we discuss the interest in studying monocultures of iPS-derived immune cells, co-cultures with neurons and 3D cultures with different cell types, as more integrated cellular approaches. The hope is that the future work with human iPS-derived cells helps not only to identify disease-specific defects in the different cell types but also to decipher the synergistic effects between neurons and immune cells. These new cellular tools could help to find new therapeutic approaches for all patients with ALS, ALS-FTD, and FTD.

Antibodies to neurofilament light as potential biomarkers in multiple sclerosis

Background and objective

The concentration of neurofilament light (NfL) protein in cerebrospinal fluid (CSF) and blood is widely considered as a quantitative measure of neuro-axonal injury. Immune reactivity to NfL released into extracellular fluids induces specific autoantibody response. We investigated the levels and avidity of antibodies to NfL in patients with multiple sclerosis (MS) treated with disease-modifying therapies (DMTs) and their correlation with disease worsening and NfL protein concentration.

Methods

We conducted a prospective longitudinal study in 246 patients with MS (125 DMT-treated and 121 untreated at baseline). Serum levels of NfL antibodies, antibody avidity and immune complexes were determined by ELISA. NfL protein was measured using the Simoa platform. Clinical variables were tested for their association with the measured parameters in multivariate generalised estimating equation models.

Results

Multivariate analysis showed that levels of NfL antibodies were higher in progressive MS compared with clinically isolated syndrome (CIS)/relapsing remitting multiple sclerosis (RRMS) (p=0.010). Anti-NfL levels drop with increasing disability score (Expanded Disability Status Scale (EDSS)) (p=0.002), although conversely, were significantly elevated in CIS/RRMS after a recent EDSS increase (p=0.012). Patients receiving DMTs showed decreased levels of anti-NfL (p=0.008), high-avidity antibodies (p=0.017) and immune-complexes compared with untreated CIS/RRMS. Patients with MS switching to natalizumab showed lower levels of anti-NfL but higher immune complexes compared with healthy controls (p=0.0071). A weak association was observed between the levels of NfL protein and NfL antibodies.

Conclusions

These results support the potential usefulness of quantifying antibody response to NfL as potential markers of progression and treatment response in MS and need to be considered when interpreting peripheral blood NfL levels.

CSF Heavy Neurofilament May Discriminate and Predict Motor Neuron Diseases with Upper Motor Neuron Involvement

Objective: To assess whether phosphorylated neurofilament heavy chain (pNfH) can discriminate different upper motor neuron (UMN) syndromes, namely, ALS, UMN-predominant ALS, primary lateral sclerosis (PLS) and hereditary spastic paraparesis (hSP) and to test the prognostic value of pNfH in UMN diseases. Methods: CSF and serum pNfH were measured in 143 patients presenting with signs of UMN and later diagnosed with classic/bulbar ALS, UMNp-ALS, hSP, and PLS. Between-group comparisons were drawn by ANOVA and receiver operating characteristic (ROC) analysis was performed. The prognostic value of pNfH was tested by the Cox regression model. Results: ALS and UMNp-ALS patients had higher CSF pNfH compared to PLS and hSP (p < 0.001). ROC analysis showed that CSF pNfH could differentiate ALS, UMNp-ALS included, from PLS and hSP (AUC = 0.75 and 0.95, respectively), while serum did not perform as well. In multivariable survival analysis among the totality of UMN patients and classic/bulbar ALS, CSF pNfH independently predicted survival. Among UMNp-ALS patients, only the progression rate (HR4.71, p = 0.01) and presence of multifocal fasciculations (HR 15.69, p = 0.02) were independent prognostic factors. Conclusions: CSF pNfH is significantly higher in classic and UMNp-ALS compared to UMN diseases with a better prognosis such as PLS and hSP. Its prognostic role is confirmed in classic and bulbar ALS, but not among UMNp, where clinical signs remained the only independent prognostic factors.

Circulating miR-181 is a prognostic biomarker for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a relentless neurodegenerative disease of the human motor neuron system, where variability in progression rate limits clinical trial efficacy. Therefore, better prognostication will facilitate therapeutic progress. In this study, we investigated the potential of plasma cell-free microRNAs (miRNAs) as ALS prognostication biomarkers in 252 patients with detailed clinical phenotyping. First, we identified, in a longitudinal cohort, miRNAs whose plasma levels remain stable over the course of disease. Next, we showed that high levels of miR-181, a miRNA enriched in neurons, predicts a greater than two-fold risk of death in independent discovery and replication cohorts (126 and 122 patients, respectively). miR-181 performance is similar to neurofilament light chain (NfL), and when combined together, miR-181 + NfL establish a novel RNA-protein biomarker pair with superior prognostication capacity. Therefore, plasma miR-181 alone and a novel miRNA-protein biomarker approach, based on miR-181 + NfL, boost precision of patient stratification. miR-181-based ALS biomarkers encourage additional validation and might enhance the power of clinical trials.

Association of the Level of Neurofilament Light With Disease Severity in Patients With Spinocerebellar Ataxia Type 2

BACKGROUND AND OBJECTIVES

Few biochemical markers have been identified in spinocerebellar ataxia type 2 (SCA2). This study aimed to determine the levels of neurofilament light (NfL) in patients with SCA2 and identify whether they were associated with disease severity.

METHODS

Participants were recruited from one medical center in China, and individuals with SCA2 were genetically diagnosed. NfL levels were assessed using the single molecule array method. Disease severity was evaluated using the Scale for the Assessment and Rating of Ataxia (SARA), the International Cooperative Ataxia Rating Scale (ICARS), and the Inventory of Non-Ataxia Symptoms (INAS). Cerebellum and brainstem volumes were calculated using neuroimaging measurements. We used Pearson's correlation and partial correlation for correlation analyses.

RESULTS

Forty-nine manifest patients with SCA2, 10 preclinical individuals with SCA2 and 92 controls were enrolled. A high consistency was identified between serum and CSF NfL (r = 0.868, p < 0.0001). In individuals with SCA2, levels of serum NfL were associated with disease severity (SARA, r = 0.425, p = 0.003; ICARS, r = 0.383, p = 0.009; INAS, r = 0.390, p = 0.007; cerebellum volume, r = - 0.393, p = 0.024) after adjustment for age. NfL levels were higher close to the expected age of onset in preclinical individuals with SCA2 (R ² = 0.43, p = 0.04).

DISCUSSION

Levels of serum NfL were correlated with disease intensity in individuals with SCA2, and were higher close to the estimated age of onset in preclinical SCA2. Therefore, NfL is a potential serum biomarker of disease severity in SCA2.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that elevated NfL levels are associated with disease severity in individuals with SCA2.

Imaging immunological processes from blood to brain in amyotrophic lateral sclerosis

Neuropathology studies of amyotrophic lateral sclerosis (ALS) and animal models of ALS reveal a strong association between aberrant protein accumulation and motor neurone damage, as well as activated microglia and astrocytes. While the role of neuroinflammation in the pathology of ALS is unclear, imaging studies of the central nervous system (CNS) support the idea that innate immune activation occurs early in disease in both humans and rodent models of ALS. In addition, emerging studies also reveal changes in monocytes, macrophages and lymphocytes in peripheral blood as well as at the neuromuscular junction. To more clearly understand the association of neuroinflammation (innate and adaptive) with disease progression, the use of biomarkers and imaging modalities allow monitoring of immune parameters in the disease process. Such approaches are important for patient stratification, selection and inclusion in clinical trials, as well as to provide readouts of response to therapy. Here, we discuss the different imaging modalities, e.g. magnetic resonance imaging, magnetic resonance spectroscopy and positron emission tomography as well as other approaches, including biomarkers of inflammation in ALS, that aid the understanding of the underlying immune mechanisms associated with motor neurone degeneration in ALS.

Humoral response to neurofilaments and dipeptide repeats in ALS progression

Objective

To appraise the utility as biomarkers of blood antibodies and immune complexes to neurofilaments and dipeptide repeat proteins, the products of translation of the most common genetic mutation in amyotrophic lateral sclerosis (ALS).

Methods

Antibodies and immune complexes against neurofilament light, medium, heavy chains as well as poly‐(GP)‐(GR) dipeptide repeats were measured in blood samples from the ALS Biomarkers (n = 107) and the phenotype–genotype biomarker (n = 129) studies and in 140 healthy controls. Target analyte levels were studied longitudinally in 37 ALS cases. Participants were stratified according to the rate of disease progression estimated before and after baseline and C9orf72 genetic status. Survival and longitudinal analyses were undertaken with reference to matched neurofilament protein expression.

Results

Compared to healthy controls, total neurofilament proteins and antibodies, neurofilament light immune complexes (p < 0.0001), and neurofilament heavy antibodies (p = 0.0061) were significantly elevated in ALS, patients with faster progressing disease (p < 0.0001) and in ALS cases with a C9orf72 mutation (p < 0.0003). Blood neurofilament light protein discriminated better ALS from healthy controls (AUC: 0.92; p < 0.0001) and faster from slower progressing ALS (AUC: 0.86; p < 0.0001) compared to heavy‐chain antibodies and light‐chain immune complexes (AUC: 0.79; p < 0.0001 and AUC: 0.74; p < 0.0001). Lower neurofilament heavy antibodies were associated with longer survival (Log‐rank Chi‐square: 7.39; p = 0.0065). Increasing levels of antibodies and immune complexes between time points were observed in faster progressing ALS.

Conclusions

We report a distinctive humoral response characterized by raising antibodies against neurofilaments and dipeptide repeats in faster progressing and C9orf72 genetic mutation carriers ALS patients. We confirm the significance of plasma neurofilament proteins in the clinical stratification of ALS.

Toll-Like Receptor Signaling Pathways: Novel Therapeutic Targets for Cerebrovascular Disorders

Toll-like receptors (TLRs), a class of pattern recognition proteins, play an integral role in the modulation of systemic inflammatory responses. Cerebrovascular diseases (CVDs) are a group of pathological conditions that temporarily or permanently affect the brain tissue mostly via the decrease of oxygen and glucose supply. TLRs have a critical role in the activation of inflammatory cascades following hypoxic-ischemic events and subsequently contribute to neuroprotective or detrimental effects of CVD-induced neuroinflammation. The TLR signaling pathway and downstream cascades trigger immune responses via the production and release of various inflammatory mediators. The present review describes the modulatory role of the TLR signaling pathway in the inflammatory responses developed following various CVDs and discusses the potential benefits of the modulation of different TLRs in the improvement of functional outcomes after brain ischemia.

Anti-neurofilament antibodies and neurodegeneration: Markers and generators

Neuroaxonal injury and loss result in the release of cytoskeleton components, including neurofilaments, into the cerebrospinal fluid and peripheral blood. Once released, neurofilaments are highly immunogenic, inducing a specific antibody response. Anti-neurofilament antibody levels correlate with the progression of diverse neurological diseases; however, their role both in the pathogenesis of disease and as a tool for monitoring disease progression is not well understood. This study reviews the current literature on anti-neurofilament antibodies. We suggest the testing of anti-neurofilament antibodies be further developed for diagnosis and targeted for treatment.

The role of Toll-like receptor signaling pathways in cerebrovascular disorders: the impact of spreading depolarization

Cerebral vascular diseases (CVDs) are a group of disorders that affect the blood supply to the brain and lead to the reduction of oxygen and glucose supply to the neurons and the supporting cells. Spreading depolarization (SD), a propagating wave of neuroglial depolarization, occurs in different CVDs. A growing amount of evidence suggests that the inflammatory responses following hypoxic-ischemic insults and after SD plays a double-edged role in brain tissue injury and clinical outcome; a beneficial effect in the acute phase and a destructive role in the late phase. Toll-like receptors (TLRs) play a crucial role in the activation of inflammatory cascades and subsequent neuroprotective or harmful effects after CVDs and SD. Here, we review current data regarding the pathophysiological role of TLR signaling pathways in different CVDs and discuss the role of SD in the potentiation of the inflammatory cascade in CVDs through the modulation of TLRs.

Serum neurofilament light chain in genetic frontotemporal dementia: a longitudinal, multicentre cohort study

BACKGROUND

Neurofilament light chain (NfL) is a promising blood biomarker in genetic frontotemporal dementia, with elevated concentrations in symptomatic carriers of mutations in GRN, C9orf72, and MAPT. A better understanding of NfL dynamics is essential for upcoming therapeutic trials. We aimed to study longitudinal NfL trajectories in people with presymptomatic and symptomatic genetic frontotemporal dementia.

METHODS

We recruited participants from 14 centres collaborating in the Genetic Frontotemporal Dementia Initiative (GENFI), which is a multicentre cohort study of families with genetic frontotemporal dementia done across Europe and Canada. Eligible participants (aged ≥18 years) either had frontotemporal dementia due to a pathogenic mutation in GRN, C9orf72, or MAPT (symptomatic mutation carriers) or were healthy at-risk first-degree relatives (either presymptomatic mutation carriers or non-carriers), and had at least two serum samples with a time interval of 6 months or more. Participants were excluded if they had neurological comorbidities that were likely to affect NfL, including cerebrovascular events. We measured NfL longitudinally in serum samples collected between June 8, 2012, and Dec 8, 2017, through follow-up visits annually or every 2 years, which also included MRI and neuropsychological assessments. Using mixed-effects models, we analysed NfL changes over time and correlated them with longitudinal imaging and clinical parameters, controlling for age, sex, and study site. The primary outcome was the course of NfL over time in the various stages of genetic frontotemporal dementia.

FINDINGS

We included 59 symptomatic carriers and 149 presymptomatic carriers of a mutation in GRN, C9orf72, or MAPT, and 127 non-carriers. Nine presymptomatic carriers became symptomatic during follow-up (so-called converters). Baseline NfL was elevated in symptomatic carriers (median 52 pg/mL [IQR 24-69]) compared with presymptomatic carriers (9 pg/mL [6-13]; p<0·0001) and non-carriers (8 pg/mL [6-11]; p<0·0001), and was higher in converters than in non-converting carriers (19 pg/mL [17-28] vs 8 pg/mL [6-11]; p=0·0007; adjusted for age). During follow-up, NfL increased in converters (b=0·097 [SE 0·018]; p<0·0001). In symptomatic mutation carriers overall, NfL did not change during follow-up (b=0·017 [SE 0·010]; p=0·101) and remained elevated. Rates of NfL change over time were associated with rate of decline in Mini Mental State Examination (b=-94·7 [SE 33·9]; p=0·003) and atrophy rate in several grey matter regions, but not with change in Frontotemporal Lobar Degeneration-Clinical Dementia Rating scale score (b=-3·46 [SE 46·3]; p=0·941).

INTERPRETATION

Our findings show the value of blood NfL as a disease progression biomarker in genetic frontotemporal dementia and suggest that longitudinal NfL measurements could identify mutation carriers approaching symptom onset and capture rates of brain atrophy. The characterisation of NfL over the course of disease provides valuable information for its use as a treatment effect marker.

FUNDING

ZonMw and the Bluefield project.

A motor neuron strategy to save time and energy in neurodegeneration: adaptive protein stoichiometry

Neurofilament proteins (Nf) are a biomarker of disease progression in amyotrophic lateral sclerosis (ALS). This study investigated whether there are major differences in expression from in vivo measurements of neurofilament isoforms, from the light chain, NfL (68 kDa), compared with larger proteins, the medium chain (NfM, 150 kDa) and the heavy (NfH, 200‐210 kDa) chains in ALS patients and healthy controls. New immunological methods were combined with Nf subunit stoichiometry calculations and Monte Carlo simulations of a coarse‐grained Nf brush model. Based on a physiological Nf subunit stoichiometry of 7 : 3 : 2 (NfL:NfM:NfH), we found an ‘adaptive’ Nf subunit stoichiometry of 24 : 2.4 : 1.6 in ALS. Adaptive Nf stoichiometry preserved NfL gyration radius in the Nf brush model. The energy and time requirements for Nf translation were 56 ± 27k ATP (5.6 h) in control subjects compared to 123 ± 102k (12.3 h) in ALS with ‘adaptive’ (24:2.4:1.6) Nf stoichiometry (not significant) and increased significantly to 355 ± 330k (35.5 h) with ‘luxury’ (7:3:2) Nf subunit stoichiometry (p < 0.0001 for each comparison). Longitudinal disease progression‐related energy consumption was highest with a ‘luxury’ (7:3:2) Nf stoichiometry. Therefore, an energy and time‐saving option for motor neurons is to shift protein expression from larger to smaller (cheaper) subunits, at little or no costs on a protein structural level, to compensate for increased energy demands.

A standard operating procedure for King's ALS clinical staging

Objective: Clinical stages in amyotrophic lateral sclerosis (ALS) can be measured using a simple system based on the number of CNS regions involved and requirement for gastrostomy or noninvasive ventilation (NIV). We aimed to design a standard operating procedure (SOP) to define the standardized use and application of the King’s staging system. Methods: We designed a SOP for the King’s staging system. We wrote case vignettes representative of ALS patients at different disease stages. During two workshops, we taught health care professionals how to use the SOP, then asked them to stage the vignettes using the SOP. We measured the extent to which SOP staging corresponded with correct clinical stage. Results: The reliability of staging using the SOP was excellent, with a Spearman’s Rank coefficient of 0.95 (p < 0.001), and was high for different groups of health care professionals, and for those with different levels of experience in ALS. The limits of agreement between SOP staging and actual clinical stage lie within a single stage, confirming that there is a clinically acceptable level of agreement between staging using the SOP and actual King’s clinical stage. There were also no systematic biases of the SOP over the range of stages, either for over-staging or under-staging. Conclusions: We have demonstrated that the staging SOP provides a reliable method of calculating clinical stages in ALS patients and can be used prospectively by a range of health care professionals with different levels of experience, as for example may be the case in multicentre clinical trials.

Staging amyotrophic lateral sclerosis: A new focus on progression

Amyotrophic lateral sclerosis (ALS) is a heterogenous motoneuronal neurodegenerative condition with a panel of phenotypes exhibiting different clinical patterns. Two compounds are currently available for the treatment of ALS but the majority of trials have failed to show a positive effect on prognosis. One of the explanations which could be put forward involves the way efficacy is evaluated: clinicians agree that the ALSFRS-revised scale used in all trials does not fit with highlighting a positive effect. So, the development and validation of new tools allowing a reliable assessment of ALS has become a key issue in clinical research. Over the last three years, two functional scales (the King's College and MiToS staging systems) have been proposed. These scales rely on two different approaches to ALS: an anatomical and prognostic concept, and loss of autonomy. Both scales propose five stages. We will discuss below the contribution of these two scales to clinical evaluation and the questions which remain to be resolved in the future.

Paraneoplastic neuronal intermediate filament autoimmunity

Objective

To describe paraneoplastic neuronal intermediate filament (NIF) autoimmunity.

Methods

Archived patient and control serum and CSF specimens were evaluated by tissue-based indirect immunofluorescence assay (IFA). Autoantigens were identified by Western blot and mass spectrometry. NIF specificity was confirmed by dual tissue section staining and 5 recombinant NIF-specific HEK293 cell-based assays (CBAs, for α-internexin, neurofilament light [NfL], neurofilament medium, or neurofilament heavy chain, and peripherin). NIF–immunoglobulin Gs (IgGs) were correlated with neurologic syndromes and cancers.

Results

Among 65 patients, NIF-IgG-positive by IFA and CBAs, 33 were female (51%). Median symptom onset age was 62 years (range 18–88). Patients fell into 2 groups, defined by the presence of NfL-IgG (21 patients, who mostly had ≥4 NIF-IgGs detected) or its absence (44 patients, who mostly had ≤2 NIF-IgGs detected). Among NfL-IgG-positive patients, 19/21 had ≥1 subacute onset CNS disorders: cerebellar ataxia (11), encephalopathy (11), or myelopathy (2). Cancers were detected in 16 of 21 patients (77%): carcinomas of neuroendocrine lineage (10) being most common (small cell [5], Merkel cell [3], other neuroendocrine [2]). Two of 257 controls (0.8%, both with small cell carcinoma) were positive by both IFA and CBA. Five of 7 patients with immunotherapy data improved. By comparison, the 44 NfL-IgG-negative patients had findings of unclear significance: diverse nervous system disorders (p = 0.006), as well as limited (p = 0.003) and more diverse (p < 0.0001) cancer accompaniments.

Conclusions

NIF-IgG detection by IFA, with confirmatory CBA testing that yields a profile including NfL-IgG, defines a paraneoplastic CNS disorder (usually ataxia or encephalopathy) accompanying neuroendocrine lineage neoplasia.

Temporospatial Analysis and New Players in the Immunology of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by progressive loss of lower and upper motor neurons (MN) leading to muscle weakness, paralysis and eventually death. Although a highly varied etiology results in ALS, it broadly manifests itself as sporadic and familial forms that have evident similarities in clinical symptoms and disease progression. There is a tremendous amount of knowledge on molecular mechanisms leading to loss of MNs and neuromuscular junctions (NMJ) as major determinants of disease onset, severity and progression in ALS. Specifically, two main opposing hypotheses, the dying forward and dying back phenomena, exist to account for NMJ denervation. The former hypothesis proposes that the earliest degeneration occurs at the central MNs and proceeds to the NMJ, whereas in the latter, the peripheral NMJ is the site of precipitating degeneration progressing backwards to the MN cell body. A large body of literature strongly indicates a role for the immune system in disease onset and progression via regulatory involvement at the level of both the central and peripheral nervous systems (CNS and PNS). In this review, we discuss the earliest reported immune responses with an emphasis on newly identified immune players in mutant superoxide dismutase 1 (mSOD1) transgenic mice, the gold standard mouse model for ALS.

Amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is characterised by the progressive loss of motor neurons in the brain and spinal cord. This neurodegenerative syndrome shares pathobiological features with frontotemporal dementia and, indeed, many patients show features of both diseases. Many different genes and pathophysiological processes contribute to the disease, and it will be necessary to understand this heterogeneity to find effective treatments. In this Seminar, we discuss clinical and diagnostic approaches as well as scientific advances in the research fields of genetics, disease modelling, biomarkers, and therapeutic strategies.

Neurofilament light as an immune target for pathogenic antibodies

Antibodies to neuronal antigens are associated with many neurological diseases including paraneoplastic neurological disorders, epilepsy, amyotrophic lateral sclerosis and multiple sclerosis. Immunization with neuronal antigens such as neurofilament light (NF-L), a neuronal intermediate filament in axons, has been shown to induce neurological disease and spasticity in mice. Also, although antibodies to NF-L are widely used as surrogate biomarkers of axonal injury in amyotrophic lateral sclerosis and multiple sclerosis, it remains to be elucidated if antibodies to NF-L contribute to neurodegeneration and neurological disease. To address this, we examined the pathogenic role of antibodies directed to NF-L in vitro using spinal cord co-cultures and in vivo in experimental autoimmune encephalomyelitis (EAE) and optic neuritis animal models of multiple sclerosis. Here we show that peripheral injections of antibodies to NF-L augmented clinical signs of neurological disease in acute EAE, increased retinal ganglion cell loss in experimental optic neuritis and induced neurological signs following intracerebral injection into control mice. The pathogenicity of antibodies to NF-L was also observed in spinal cord co-cultures where axonal loss was induced. Taken together, our results reveal that as well as acting as reliable biomarkers of neuronal damage, antibodies to NF-L exacerbate neurological disease, suggesting that antibodies to NF-L generated during disease may also be pathogenic and play a role in the progression of neurodegeneration.

Urinary Extracellular Domain of Neurotrophin Receptor p75 as a Biomarker for Amyotrophic Lateral Sclerosis in a Chinese cohort

To comprehensively assess whether p75^ECD in urine could be a candidate biomarker for ALS evaluation. Urine samples were collected from 101 ALS patients, 108 patients with other neurological disease (OND) and 97 healthy controls. 61 ALS patients were followed up with clinical data including ALSFRS-r every 6 to 12 months, 23 ALS patients died and 17 ALS patients lost touch during follow up period. Enzyme-linked immunoassay was employed to determine urine p75^ECD concentration. The ALSFRS-r was employed to assess the severity of ALS. The concentration of p75^ECD in ALS was significantly higher than that of OND and CTRL (p < 0.001). Additionally, urine p75^ECD concentrations in ALS-definite grade patients were significantly higher than that in ALS-probable grade and ALS-possible grade patients (p < 0.001). Higher urine p75^ECD concentrations were correlated with increased clinical stage (p = 0.0309); urine p75^ECD concentrations and ALSFRS-r were negatively correlated (p = 0.022); and urine p75^ECD concentration in the fast-progressing ALS group was significantly higher than that in slow-progression (p = 0.0026). Our finding indicates that urine p75^ECD concentration provides additional evidence for patients with clinically suspected ALS, and can be employed to evaluate ALS-severity.

Amyotrophic lateral sclerosis: moving towards a new classification system

Amyotrophic lateral sclerosis is a progressive adult-onset neurodegenerative disease that primarily affects upper and lower motor neurons, but also frontotemporal and other regions of the brain. The extent to which each neuronal population is affected varies between individuals. The subsequent patterns of disease progression form the basis of diagnostic criteria and phenotypic classification systems, with considerable overlap in the clinical terms used. This overlap can lead to confusion between diagnosis and phenotype. Formal classification systems such as the El Escorial criteria and the International Classification of Diseases are systematic approaches but they omit features that are important in clinical management, such as rate of progression, genetic basis, or functional effect. Therefore, many neurologists use informal classification approaches that might not be systematic, and could include, for example, anatomical descriptions such as flail-arm syndrome. A new strategy is needed to combine the benefits of a systematic approach to classification with the rich and varied phenotypic descriptions used in clinical practice.

TDP-43 and Cytoskeletal Proteins in ALS

Amyotrophic lateral sclerosis (ALS) represents a rapidly progressing neurodegenerative disease and is characterized by a degeneration of motor neurons. Motor neurons are particularly susceptible to selective and early degeneration because of their extended axon length and their dependency on the cytoskeleton for its stability, signaling, and axonal transport. The motor neuron cytoskeleton comprises actin filaments, neurofilaments like peripherin, and microtubules. The Transactivating Response Region (TAR) DNA Binding Protein (TDP-43) forms characteristic cytoplasmic aggregates in motor neurons of ALS patients, and at least in part, the pathogenesis of ALS seems to be driven by toxic pTDP-43 aggregates in cytoplasm, which lead to a diminished axon formation and reduced axon length. Diminished axon formation and reduced axon length suggest an interaction of TDP-43 with the cytoskeleton of motor neurons. TDP-43 interacts with several cytoskeletal components, e.g., the microtubule-associated protein 1B (MAP1B) or the neurofilament light chain (NFL) through direct binding to its RNA. From a clinical perspective, cytoskeletal biomarkers like phosphorylated neurofilament heavy chain (pNFH) and NFL are already clinically used in ALS patients to predict survival, disease progression, and duration. Thus, in this review, we focus on the interaction of TDP-43 with the different cytoskeleton components such as actin filaments, neurofilaments, and microtubules as well as their associated proteins as one aspect in the complex pathogenesis of ALS.

Comparison of the King's and MiToS staging systems for ALS

Objective: To investigate and compare two ALS staging systems, King’s clinical staging and Milano-Torino (MiToS) functional staging, using data from the LiCALS phase III clinical trial (EudraCT 2008-006891-31). Methods: Disease stage was derived retrospectively for each system from the ALS Functional Rating Scale-Revised subscores using standard methods. The two staging methods were then compared for timing of stages using box plots, correspondence using chi-square tests, agreement using a linearly weighted kappa coefficient and concordance using Spearman’s rank correlation. Results: For both systems, progressively higher stages occurred at progressively later proportions of the disease course, but the distribution differed between the two methods. King’s stage 3 corresponded to MiToS stage 1 most frequently, with earlier King’s stages 1 and 2 largely corresponding to MiToS stage 0 or 1. The Spearman correlation was 0.54. There was fair agreement between the two systems with kappa coefficient of 0.21. Conclusion: The distribution of timings shows that the two systems are complementary, with King’s staging showing greatest resolution in early to mid-disease corresponding to clinical or disease burden, and MiToS staging having higher resolution for late disease, corresponding to functional involvement. We therefore propose using both staging systems when describing ALS.

Autoimmune Aspects of Neurodegenerative and Psychiatric Diseases: A Template for Innovative Therapy

Neurodegenerative and psychiatric diseases (NPDs) are today's most important group of diseases, surpassing both atherosclerotic cardiovascular disease and cancer in morbidity incidence. Although NPDs have a dramatic impact on our society because of their high incidence, mortality, and severe debilitating character, remarkably few effective interventions have become available. The current treatments, if available, comprise the lifelong intake of general immunosuppressants to delay disease progression or neurotransmitter antagonists/agonists to dampen undesired behaviors. The long-term usage of such medication, however, coincides with often severe adverse side effects. There is, therefore, an urgent need for safe and effective treatments for these diseases. Here, we discuss that many NPDs coincide with subtle chronic or flaring brain inflammation sometimes escalating with infiltrations of lymphocytes in the inflamed brain parts causing mild to severe or even lethal brain damage. Thus, NPDs show all features of autoimmune diseases. In this review, we postulate that NPDs resemble autoimmune-driven inflammatory diseases in many aspects and may belong to the same disease spectrum. Just like in autoimmune diseases, NPD symptoms basically are manifestations of a chronic self-sustaining inflammatory process with detrimental consequences for the patient. Specific inhibition of the destructive immune responses in the brain, leaving the patient's immune system intact, would be the ultimate solution to cure patients from the disease. To reach this goal, the primary targets, e.g., the primary self-antigens (pSAgs) of the patient's chronic (auto)immune response, need to be identified. For a few major NPDs, immunological studies led to the identification of the pSAgs involved in the autoimmune damage of specific brain parts. However, further research is needed to complete the list of pSAgs for all NPDs. Such immunological studies will not only provide crucial insights into NPD pathogenesis but also ultimately enable the development of a new generation of safe and effective immunotherapies for NPDs. Interventions that will dramatically improve the life expectancy and quality of life of individual patients and, moreover, will significantly reduce the health-care costs of the society in general.

Non-neuronal Cells in ALS: Role of Glial, Immune cells and Blood-CNS Barriers

Neurological dysfunction and motor neuron degeneration in amyotrophic lateral sclerosis (ALS) is strongly associated with neuroinflammation reflected by activated microglia and astrocytes in the CNS. In ALS endogenous triggers in the CNS such as aggregated protein and misfolded proteins activate a pathogenic response by innate immune cells. However, there is also strong evidence for a neuroprotective immune response in ALS. Emerging evidence also reveals changes in the peripheral adaptive immune responses as well as alterations in the blood brain barrier that may aid traffic of lymphocytes and antibodies into the CNS. Understanding the triggers of neuroinflammation is key to controlling neuronal loss. Here, we review the current knowledge regarding the roles of non-neuronal cells as well as the innate and adaptive immune responses in ALS. Existing ALS animal models, in particular genetic rodent models, are very useful to study the underlying pathogenic mechanisms of motor neuron degeneration. We also discuss the approaches used to target the pathogenic immune responses and boost the neuroprotective immune pathways as novel immunotherapies for ALS.

Neurofilaments in CSF As Diagnostic Biomarkers in Motor Neuron Disease: A Meta-Analysis

Objective: Neurofilaments in CSF are promising biomarkers which might help in the diagnosis of motor neuron disease (MND). We aim to assess the diagnostic value of neurofilaments in CSF for MND.

Methods: Pubmed, Emabase, and Web of Science were searched for relevant studies systematically. Articles in English that evaluated the utility of neurofilaments in CSF in the diagnosis of MND were included. Data were extracted by two independent investigators. Diagnostic indexes for neurofilament light chain (NFL) and phosphorylated neurofilament heavy chain (pNFH) were calculated separately. Stata 12.0 software with a bivariate mixed-effects model was used to summarize the diagnostic indexes from eligible studies.

Results: Five studies on NFL and eight studies on pNFH met inclusion criteria. For NFL, the pooled sensitivity and specificity were 81% (95% confidence interval [CI], 72–88%) and 85% (95% CI, 76–91%), respectively; the positive likelihood ratio (PLR) and negative likelihood ratio (NLR) were 5.5 (95% CI, 3.1–9.8) and 0.22 (95% CI, 0.14–0.35), respectively; the summary diagnostic odds ratio (DOR) was 25 (95% CI, 9–70), and the area under summary receiver operator characteristic curve (AUC) was 0.90 (95% CI, 0.87–0.92). For pNFH, the pooled sensitivity, specificity, PLR and NLR were 85% (95% CI, 80–88%), 85% (95% CI, 77–90%), 5.5 (95% CI, 3.6–8.4), and 0.18 (95% CI, 0.13–0.25), respectively; the DOR was 30 (95% CI, 16–58), and the AUC was 0.91 (95% CI, 0.88–0.93).

Conclusion: Neurofilaments in CSF have a high value in the diagnosis of MND, though the optimal cutoff value remains to be further investigated.

Voltage-Gated Potassium Channel Antibodies in Slow-Progression Motor Neuron Disease

BACKGROUND

The spectrum of autoimmune neurological diseases associated with voltage-gated potassium channel (VGKC)-complex antibodies (Abs) ranges from peripheral nerve disorders to limbic encephalitis. Recently, low titers of VGKC-complex Abs have also been reported in neurodegenerative disorders, but their clinical relevance is unknown.

OBJECTIVE

The aim of the study was to explore the prevalence of VGKC-complex Abs in slow-progression motor neuron disease (MND).

METHODS

We compared 11 patients affected by slow-progression MND with 9 patients presenting typical progression illness. Sera were tested for VGKC-complex Abs by radioimmunoassay. The distribution of VGKC-complex Abs was analyzed with the Mann-Whitney U test.

RESULTS

The statistical analysis showed a significant difference between the mean values in the study and control groups. A case with long-survival MND harboring VGKC-complex Abs and treated with intravenous immunoglobulins is described.

CONCLUSION

Although VGKC-complex Abs are not likely to be pathogenic, these results could reflect the coexistence of an immunological activation in patients with slow disease progression.

Increased Incidence of Amyotrophic Lateral Sclerosis in Polymyositis: A Nationwide Cohort Study

OBJECTIVE

Past studies have shown common pathologic characteristics and shared immunologic features between polymyositis (PM) and amyotrophic lateral sclerosis (ALS). To explore the potential relationship between the 2 diseases, we performed a nationwide cohort study.

METHODS

We identified all newly diagnosed patients with PM from Taiwan's Registry of Catastrophic Illness Database between January 1, 1998 and December 31, 2011. Each PM patient was matched to ≤5 control patients from the National Health Insurance Research Database by sex, age, and entry date. Cumulative incidence of ALS was calculated by the Kaplan-Meier method and compared using the log rank test. Cox hazard regression was used to calculate the hazard ratio of ALS.

RESULTS

A total of 1,778 PM patients and 8,124 control patients were enrolled. PM patients had a higher cumulative incidence of ALS (P < 0.001). There was a positive correlation in being diagnosed with ALS in patients previously diagnosed with PM when stratified by sex. Consistent trends were conserved across different age strata. The strength of this association remained statistically significant after adjusting for sex, age, and concomitant autoimmune diseases (hazard ratio 25.72 [95% confidence interval 2.95-224.58]; P = 0.003).

CONCLUSION

This study demonstrates that a diagnosis of PM increased the likelihood of a subsequent ALS diagnosis, independent of sex, age, and concomitant autoimmune diseases. Future studies are warranted to clarify the underlying biologic mechanisms and to translate them into clinical therapeutic options.

Emerging molecular biomarker targets for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a rapidly progressive neurodegenerative disease that affects upper (UMN) and lower motor (LMN) neurons. It is associated with a short survival and there is no effective treatment, in spite of a large number of clinical trials. Strong efforts have been made to identify novel disease biomarkers to support diagnosis, provide information on prognosis, to measure disease progression in trials and increase our knowledge on disease pathogenesis. Electromyography by testing the function of the LMN can be used as a biomarker of its dysfunction. A number of electrophysiological and neuroimaging methods have been explored to identify a reliable marker of UMN degeneration. Recently, strong evidence from independent groups, large cohorts of patients and multicenter studies indicate that neurofilaments are very promising diagnostic biomarkers, in particular cerebrospinal fluid and blood levels of phosphoneurofilament heavy chain and neurofilament light chain. Furthermore, their increased levels are associated with poor prognosis. Additional studies have been performed aiming to identify other biomarkers, which alone or in combination with neurofilaments could increase the sensitivity and the specificity of the assays. Emerging molecular marker targets are being discovered, but more studies with standardized methods are required in larger cohorts of ALS patients.

Neurofilament light chain: A prognostic biomarker in amyotrophic lateral sclerosis

OBJECTIVE

To test blood and CSF neurofilament light chain (NfL) levels in relation to disease progression and survival in amyotrophic lateral sclerosis (ALS).

METHODS

Using an electrochemiluminescence immunoassay, NfL levels were measured in samples from 2 cohorts of patients with sporadic ALS and healthy controls, recruited in London (ALS/control, plasma: n = 103/42) and Oxford (ALS/control, serum: n = 64/36; paired CSF: n = 38/20). NfL levels in patients were measured at regular intervals for up to 3 years. Change in ALS Functional Rating Scale-Revised score was used to assess disease progression. Survival was evaluated using Cox regression and Kaplan-Meier analysis.

RESULTS

CSF, serum, and plasma NfL discriminated patients with ALS from healthy controls with high sensitivity (97%, 89%, 90%, respectively) and specificity (95%, 75%, 71%, respectively). CSF NfL was highly correlated with serum levels (r = 0.78, p < 0.0001). Blood NfL levels were approximately 4 times as high in patients with ALS compared with controls in both cohorts, and maintained a relatively constant expression during follow-up. Blood NfL levels at recruitment were strong, independent predictors of survival. The highest tertile of blood NfL at baseline had a mortality hazard ratio of 3.91 (95% confidence interval 1.98-7.94, p < 0.001).

CONCLUSION

Blood-derived NfL level is an easily accessible biomarker with prognostic value in ALS. The individually relatively stable levels longitudinally offer potential for NfL as a pharmacodynamic biomarker in future therapeutic trials.

CLASSIFICATION OF EVIDENCE

This report provides Class III evidence that the NfL electrochemiluminescence immunoassay accurately distinguishes patients with sporadic ALS from healthy controls.

Use of biomarkers in ALS drug development and clinical trials

The past decade has seen a dramatic increase in the discovery of candidate biomarkers for ALS. These biomarkers typically can either differentiate ALS from control subjects or predict disease course (slow versus fast progression). At the same time, late-stage clinical trials for ALS have failed to generate improved drug treatments for ALS patients. Incorporation of biomarkers into the ALS drug development pipeline and the use of biologic and/or imaging biomarkers in early- and late-stage ALS clinical trials have been absent and only recently pursued in early-phase clinical trials. Further clinical research studies are needed to validate biomarkers for disease progression and develop biomarkers that can help determine that a drug has reached its target within the central nervous system. In this review we summarize recent progress in biomarkers across ALS model systems and patient population, and highlight continued research directions for biomarkers that stratify the patient population to enrich for patients that may best respond to a drug candidate, monitor disease progression and track drug responses in clinical trials. It is crucial that we further develop and validate ALS biomarkers and incorporate these biomarkers into the ALS drug development process. This article is part of a Special Issue entitled ALS complex pathogenesis.

Plasma neurofilament heavy chain levels and disease progression in amyotrophic lateral sclerosis: insights from a longitudinal study

OBJECTIVE

To investigate the role of longitudinal plasma neurofilament heavy chain protein (NfH) levels as an indicator of clinical progression and survival in amyotrophic lateral sclerosis (ALS).

METHODS

A cross-sectional study involving 136 clinically heterogeneous patients with ALS and 104 healthy and neurological controls was extended to include a prospective analysis of 74 of these ALS cases, with samplings at approximately 3-month intervals in a follow-up period of up to 3 years. We analysed the correlation between longitudinal NfH-phosphoform levels and disease progression. Temporal patterns of NfH changes were evaluated using multilevel linear regression.

RESULTS

Baseline plasma NfH levels were higher than controls only in patients with ALS with short disease duration to baseline sampling. Compared with controls, fast-progressing patients with ALS, particularly those with a short diagnostic latency and disease duration, had higher plasma NfH levels at an early stage and lower levels closer to end-stage disease. Lower NfH levels between visits were associated with rapid functional deterioration. We also detected antibodies against NfH, NfH aggregates and NfH cleavage products.

CONCLUSIONS

Disease progression in ALS involves defined trajectories of plasma NfH levels, reflecting speed of neurological decline and survival. Intervisit plasma NfH changes are also indicative of disease progression. This study confirms that longitudinal measurements of NfH plasma levels are more informative than cross-sectional studies, where the time of sampling may represent a bias in the interpretation of the results. Autoantibodies against NfH aggregates and NfH cleavage products may explain the variable expression of plasma NfH with disease progression.

TRAIL REGISTRATION NUMBER

NIHRID6160.

Challenges in the Understanding and Treatment of Amyotrophic Lateral Sclerosis/Motor Neuron Disease

With the acceleration in our understanding of ALS and the related motor neuron disease has come even greater challenges in reconciling all of the proposed pathogenic mechanisms and how this will translate into impactful treatments. Fundamental issues such as diagnostic definition(s) of the disease spectrum, relevant biomarkers, the impact of multiple novel genetic mutations and the significant effect of symptomatic treatments on disease progression are all areas of active investigation. In this review, we will focus on these key issues and highlight the challenges that confront both clinicians and basic science researchers.

Amyotrophic lateral sclerosis as a spatiotemporal mislocalization disease: location, location, location

Spatiotemporal localization of signals is a fundamental feature impacting cell survival and proper function. The cell needs to respond in an accurate manner in both space and time to both intra- and intercellular environment cues. The regulation of this comprehensive process involves the cytoskeleton and the trafficking machinery, as well as local protein synthesis and ligand-receptor mechanisms. Alterations in such mechanisms can lead to cell dysfunction and disease. Motor neurons that can extend over tens of centimeters are a classic example for the importance of such events. Changes in spatiotemporal localization mechanisms are thought to play a role in motor neuron degeneration that occurs in amyotrophic lateral sclerosis (ALS). In this review we will discuss these mechanisms and argue that possible misregulated factors can lead to motor neuron degeneration in ALS.

Quantifying disease progression in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) exhibits characteristic variability of onset and rate of disease progression, with inherent clinical heterogeneity making disease quantitation difficult. Recent advances in understanding pathogenic mechanisms linked to the development of ALS impose an increasing need to develop strategies to predict and more objectively measure disease progression. This review explores phenotypic and genetic determinants of disease progression in ALS, and examines established and evolving biomarkers that may contribute to robust measurement in longitudinal clinical studies. With targeted neuroprotective strategies on the horizon, developing efficiencies in clinical trial design may facilitate timely entry of novel treatments into the clinic.

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in amyotrophic lateral sclerosis (ALS)

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases, responsible for the integrity of the basement membrane (BM) via degradation of extracellular matrix and BM components. These enzymes are presented in central and peripheral nervous system. They are considered to be involved in the pathogenesis of several neurological diseases, including amyotrophic lateral sclerosis (ALS). ALS is a motor neuron disease, leading to muscle atrophy, paralysis and death within 3–5 years from diagnosis. Currently, there is no treatment that can substantially prolong life of ALS patients. Despite the fact that MMPs are not specific for ALS, there is also strong evidence that these enzymes are involved in the pathology of ALS. MMPs are able to exert direct neurotoxic effects, or may cause cell death by degrading matrix proteins. The objective of this paper is to provide an updated and comprehensive review concerning the role of MMPs and their tissue inhibitors (TIMPs) in the pathology of ALS with an emphasis on the significance of MMP-2 and MMP-9 as well as their tissue inhibitors as potential biomarkers of ALS. Numerous hypotheses have been proposed regarding the role of selected MMPs and TIMPs in ALS pathogenesis. Moreover, selective MMPs’ inhibitors might be potential targets for therapeutic strategies for patients with ALS. However, future investigations are necessary before some of those non-specific for ALS enzymes could finally be used as biomarkers of this disease.

Inflammation in neurodegenerative diseases--an update

Neurodegeneration, the progressive dysfunction and loss of neurons in the central nervous system (CNS), is the major cause of cognitive and motor dysfunction. While neuronal degeneration is well-known in Alzheimer's and Parkinson's diseases, it is also observed in neurotrophic infections, traumatic brain and spinal cord injury, stroke, neoplastic disorders, prion diseases, multiple sclerosis and amyotrophic lateral sclerosis, as well as neuropsychiatric disorders and genetic disorders. A common link between these diseases is chronic activation of innate immune responses including those mediated by microglia, the resident CNS macrophages. Such activation can trigger neurotoxic pathways leading to progressive degeneration. Yet, microglia are also crucial for controlling inflammatory processes, and repair and regeneration. The adaptive immune response is implicated in neurodegenerative diseases contributing to tissue damage, but also plays important roles in resolving inflammation and mediating neuroprotection and repair. The growing awareness that the immune system is inextricably involved in mediating damage as well as regeneration and repair in neurodegenerative disorders, has prompted novel approaches to modulate the immune system, although it remains whether these approaches can be used in humans. Additional factors in humans include ageing and exposure to environmental factors such as systemic infections that provide additional clues that may be human specific and therefore difficult to translate from animal models. Nevertheless, a better understanding of how immune responses are involved in neuronal damage and regeneration, as reviewed here, will be essential to develop effective therapies to improve quality of life, and mitigate the personal, economic and social impact of these diseases.

The past, present and future of stem cell clinical trials for ALS

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder that is characterized by progressive degeneration of motor neurons in the cortex, brainstem and spinal cord. This leads to paralysis, respiratory insufficiency and death within an average of 3 to 5 years from disease onset. While the genetics of ALS are becoming more understood in familial cases, the mechanisms underlying disease pathology remain unclear and there are no effective treatment options. Without understanding what causes ALS it is difficult to design treatments. However, in recent years stem cell transplantation has emerged as a potential new therapy for ALS patients. While motor neuron replacement remains a focus of some studies trying to treat ALS with stem cells, there is more rationale for using stem cells as support cells for dying motor neurons as they are already connected to the muscle. This could be through reducing inflammation, releasing growth factors, and other potential less understood mechanisms. Prior to moving into patients, stringent pre-clinical studies are required that have at least some rationale and efficacy in animal models and good safety profiles. However, given our poor understanding of what causes ALS and whether stem cells may ameliorate symptoms, there should be a push to determine cell safety in pre-clinical models and then a quick translation to the clinic where patient trials will show if there is any efficacy. Here, we provide a critical review of current clinical trials using either mesenchymal or neural stem cells to treat ALS patients. Pre-clinical data leading to these trials, as well as those in development are also evaluated in terms of mechanisms of action, validity of conclusions and rationale for advancing stem cell treatment strategies for this devastating disorder.