Changes in glial cell activation and extracellular vesicles production precede the onset of disease symptoms in transgenic hSOD1G93A pigs

SOD1 gene is associated with progressive motor neuron degeneration in the familiar forms of amyotrophic lateral sclerosis. Although studies on mutant human SOD1 transgenic rodent models have provided important insights into disease pathogenesis, they have not led to the discovery of early biomarkers or effective therapies in human disease. The recent generation of a transgenic swine model expressing the human pathological hSOD1G93A gene, which recapitulates the course of human disease, represents an interesting tool for the identification of early disease mechanisms and diagnostic biomarkers. Here, we analyze the activation state of CNS cells in transgenic pigs during the disease course and investigate whether changes in neuronal and glial cell activation state can be reflected by the amount of extracellular vesicles they release in biological fluids. To assess the activation state of neural cells, we performed a biochemical characterization of neurons and glial cells in the spinal cords of hSOD1G93A pigs during the disease course. Quantification of EVs of CNS cell origin was performed in cerebrospinal fluid and plasma of transgenic pigs at different disease stages by Western blot and peptide microarray analyses. We report an early activation of oligodendrocytes in hSOD1G93A transgenic tissue followed by astrocyte and microglia activation, especially in animals with motor symptoms. At late asymptomatic stage, EV production from astrocytes and microglia is increased in the cerebrospinal fluid, but not in the plasma, of transgenic pigs reflecting donor cell activation in the spinal cord. Estimation of EV production by biochemical analyses is corroborated by direct quantification of neuron- and microglia-derived EVs in the cerebrospinal fluid by a Membrane Sensing Peptide enabled on-chip analysis that provides fast results and low sample consumption. Collectively, our data indicate that alteration in astrocytic EV production precedes the onset of disease symptoms in the hSODG93A swine model, mirroring donor cell activation in the spinal cord, and suggest that EV measurements from the cells first activated in the ALS pig model, i.e. OPCs, may further improve early disease detection.

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.

Intramuscular IL-10 Administration Enhances the Activity of Myogenic Precursor Cells and Improves Motor Function in ALS Mouse Model

Amyotrophic Lateral Sclerosis (ALS) is the most common adult motor neuron disease, with a poor prognosis, a highly unmet therapeutic need, and a burden on health care costs. Hitherto, strategies aimed at protecting motor neurons have missed or modestly delayed ALS due to a failure in countering the irreversible muscular atrophy. We recently provided direct evidence underlying the pivotal role of macrophages in preserving skeletal muscle mass. Based on these results, we explored whether the modulation of macrophage muscle response and the enhancement of satellite cell differentiation could effectively promote the generation of new myofibers and counteract muscle dysfunction in ALS mice. For this purpose, disease progression and the survival of SOD1G93A mice were evaluated following IL-10 injections in the hindlimb skeletal muscles. Thereafter, we used ex vivo methodologies and in vitro approaches on primary cells to assess the effect of the treatment on the main pathological signatures. We found that IL-10 improved the motor performance of ALS mice by enhancing satellite cells and the muscle pro-regenerative activity of macrophages. This resulted in delayed muscle atrophy and motor neuron loss. Our findings provide the basis for a suitable adjunct multisystem therapeutic approach that pinpoints a primary role of muscle pathology in ALS.

Immune-mediated myogenesis and acetylcholine receptor clustering promote a slow disease progression in ALS mouse models

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a heterogeneous disease in terms of onset and progression rate. This may account for therapeutic clinical trial failure. Transgenic SOD1G93A mice on C57 or 129Sv background have a slow and fast disease progression rate, mimicking the variability observed in patients. Based on evidence inferring the active influence of skeletal muscle on ALS pathogenesis, we explored whether dysregulation in hindlimb skeletal muscle reflects the phenotypic difference between the two mouse models.

METHODS

Ex vivo immunohistochemical, biochemical, and biomolecular methodologies, together with in vivo electrophysiology and in vitro approaches on primary cells, were used to afford a comparative and longitudinal analysis of gastrocnemius medialis between fast- and slow-progressing ALS mice.

RESULTS

We reported that slow-progressing mice counteracted muscle denervation atrophy by increasing acetylcholine receptor clustering, enhancing evoked currents, and preserving compound muscle action potential. This matched with prompt and sustained myogenesis, likely triggered by an early inflammatory response switching the infiltrated macrophages towards a M2 pro-regenerative phenotype. Conversely, upon denervation, fast-progressing mice failed to promptly activate a compensatory muscle response, exhibiting a rapidly progressive deterioration of muscle force.

CONCLUSIONS

Our findings further pinpoint the pivotal role of skeletal muscle in ALS, providing new insights into underestimated disease mechanisms occurring at the periphery and providing useful (diagnostic, prognostic, and mechanistic) information to facilitate the translation of cost-effective therapeutic strategies from the laboratory to the clinic.

Cell therapy in ALS: An update on preclinical and clinical studies

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by the loss of motor neurons and neuromuscular impairment leading to complete paralysis, respiratory failure and premature death. The pathogenesis of the disease is multifactorial and noncell-autonomous involving the central and peripheral compartments of the neuromuscular axis and the skeletal muscle. Advanced clinical trials on specific ALS-related pathways have failed to significantly slow the disease. Therapy with stem cells from different sources has provided a promising strategy to protect the motor units exerting their effect through multiple mechanisms including neurotrophic support and excitotoxicity and neuroinflammation modulation, as evidenced from preclinical studies. Several phase I and II clinical trial of ALS patients have been developed showing positive effects in terms of safety and tolerability. However, the modest results on functional improvement in ALS patients suggest that only a coordinated effort between basic and clinical researchers could solve many problems, such as selecting the ideal stem cell source, identifying their mechanism of action and expected clinical outcomes. A promising approach may be stem cells selected or engineered to deliver optimal growth factor support at multiple sites along the neuromuscular pathway. This review covers recent advances in stem cell therapies in animal models of ALS, as well as detailing the human clinical trials that have been done and are currently undergoing development.

Effect of RNS60 in amyotrophic lateral sclerosis: a phase II multicentre, randomized, double-blind, placebo-controlled trial

BACKGROUND AND PURPOSE

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with limited treatment options. RNS60 is an immunomodulatory and neuroprotective investigational product that has shown efficacy in animal models of ALS and other neurodegenerative diseases. Its administration has been safe and well tolerated in ALS subjects in previous early phase trials.

METHODS

This was a phase II, multicentre, randomized, double-blind, placebo-controlled, parallel-group trial. Participants diagnosed with definite, probable or probable laboratory-supported ALS were assigned to receive RNS60 or placebo administered for 24 weeks intravenously (375 ml) once a week and via nebulization (4 ml/day) on non-infusion days, followed by an additional 24 weeks off-treatment. The primary objective was to measure the effects of RNS60 treatment on selected biomarkers of inflammation and neurodegeneration in peripheral blood. Secondary objectives were to measure the effect of RNS60 on functional impairment (ALS Functional Rating Scale-Revised), a measure of self-sufficiency, respiratory function (forced vital capacity, FVC), quality of life (ALS Assessment Questionnaire-40, ALSAQ-40) and survival. Tolerability and safety were assessed.

RESULTS

Seventy-four participants were assigned to RNS60 and 73 to placebo. Assessed biomarkers did not differ between arms. The mean rate of decline in FVC and the eating and drinking domain of ALSAQ-40 was slower in the RNS60 arm (FVC, difference 0.41 per week, standard error 0.16, p = 0.0101; ALSAQ-40, difference -0.19 per week, standard error 0.10, p = 0.0319). Adverse events were similar in the two arms. In a post hoc analysis, neurofilament light chain increased over time in bulbar onset placebo participants whilst remaining stable in those treated with RNS60.

CONCLUSIONS

The positive effects of RNS60 on selected measures of respiratory and bulbar function warrant further investigation.

An interaction between synapsin and C9orf72 regulates excitatory synapses and is impaired in ALS/FTD

Dysfunction and degeneration of synapses is a common feature of amyotrophic lateral sclerosis and frontotemporal dementia (ALS/FTD). A GGGGCC hexanucleotide repeat expansion in the C9ORF72 gene is the main genetic cause of ALS/FTD (C9ALS/FTD). The repeat expansion leads to reduced expression of the C9orf72 protein. How C9orf72 haploinsufficiency contributes to disease has not been resolved. Here we identify the synapsin family of synaptic vesicle proteins, the most abundant group of synaptic phosphoproteins, as novel interactors of C9orf72 at synapses and show that C9orf72 plays a cell-autonomous role in the regulation of excitatory synapses. We mapped the interaction of C9orf72 and synapsin to the N-terminal longin domain of C9orf72 and the conserved C domain of synapsin, and show interaction of the endogenous proteins in synapses. Functionally, C9orf72 deficiency reduced the number of excitatory synapses and decreased synapsin levels at remaining synapses in vitro in hippocampal neuron cultures and in vivo in the hippocampal mossy fibre system of C9orf72 knockout mice. Consistent with synaptic dysfunction, electrophysiological recordings identified impaired excitatory neurotransmission and network function in hippocampal neuron cultures with reduced C9orf72 expression, which correlated with a severe depletion of synaptic vesicles from excitatory synapses in the hippocampus of C9orf72 knockout mice. Finally, neuropathological analysis of post-mortem sections of C9ALS/FTD patient hippocampus with C9orf72 haploinsufficiency revealed a marked reduction in synapsin, indicating that disruption of the interaction between C9orf72 and synapsin may contribute to ALS/FTD pathobiology. Thus, our data show that C9orf72 plays a cell-autonomous role in the regulation of neurotransmission at excitatory synapses by interaction with synapsin and modulation of synaptic vesicle pools, and identify a novel role for C9orf72 haploinsufficiency in synaptic dysfunction in C9ALS/FTD.

The p97-Nploc4 ATPase complex plays a role in muscle atrophy during cancer and amyotrophic lateral sclerosis

BACKGROUND

The p97 complex participates in the degradation of muscle proteins during atrophy upon fasting or denervation interacting with different protein adaptors. We investigated whether and how it might also be involved in muscle wasting in cancer, where loss of appetite occurs, or amyotrophic lateral sclerosis (ALS), where motoneuron death causes muscle denervation and fatal paralysis.

METHODS

As cancer cachexia models, we used mice bearing colon adenocarcinoma C26, human renal carcinoma RXF393, or Lewis lung carcinoma, with breast cancer 4T1-injected mice as controls. As ALS models, we employed 129/SvHsd mice carrying the mutation G93A in human SOD1. The expression of p97 and its adaptors was analysed in their muscles by quantitative real-time polymerase chain reaction (qPCR) and western blot. We electroporated plasmids into muscles or treated mice with disulfiram (DSF) to test the effects of inhibiting p97 and nuclear protein localization protein 4 (Nploc4), one of its adaptors, on atrophy.

RESULTS

The mRNA levels of p97 were induced by 1.5-fold to 2-fold in tibialis anterior (TA) of all the cachectic models but not in the non-cachectic 4T1 tumour-bearing mice (P ≤ 0.05). Similarly, p97 was high both in mRNA and protein in TA from 17-week-old SOD1^G93A mice (P ≤ 0.01). Electroporation of a shRNA for murine p97 into mouse muscle reduced the fibre atrophy caused by C26 (P = 0.0003) or ALS (P ≤ 0.01). When we interrogated a microarray, we had previously generated for the expression of p97 adaptors, we found Derl1, Herpud1, Nploc4, Rnf31, and Hsp90ab1 induced in cachectic TA from C26-mice (Fold change > 1.2, adjusted P ≤ 0.05). By qPCR, we validated their inductions in TA of cachectic and ALS models and selected Nploc4 as the one also induced at the protein level by 1.5-fold (P ≤ 0.01). Electroporation of a CRISPR/Cas9 vector against Nploc4 into muscle reduced the fibre atrophy caused by C26 (P = 0.01) or ALS (P ≤ 0.0001). Because DSF uncouples p97 from Nploc4, we treated atrophying myotubes with DSF, and found accumulated mono and polyubiquitinated proteins and reduced degradation of long-lived proteins by 35% (P ≤ 0.0001), including actin (P ≤ 0.05). DSF halves Nploc4 in the soluble muscle fraction (P ≤ 0.001) and given to C26-bearing mice limited the body and muscle weight loss (P ≤ 0.05), with no effect on tumour growth.

CONCLUSIONS

Overall, cancer cachexia and ALS seem to display similar mechanisms of muscle wasting at least at the catabolic level. The p97-Nploc4 complex appears to have a crucial role in muscle atrophy during these disorders and disrupting this complex might serve as a novel drug strategy.

Boosting the peripheral immune response in the skeletal muscles improved motor function in ALS transgenic mice

Monocyte chemoattractant protein-1 (MCP1) is one of the most powerful pro-inflammatory chemokines. However, its signalling is pivotal in driving injured axon and muscle regeneration.

Interplay between immunity and amyotrophic lateral sclerosis: Clinical impact

Amyotrophic lateral sclerosis (ALS) is a debilitating and rapidly fatal neurodegenerative disease. Despite decades of research and many new insights into disease biology over the 150 years since the disease was first described, causative pathogenic mechanisms in ALS remain poorly understood, especially in sporadic cases. Our understanding of the role of the immune system in ALS pathophysiology, however, is rapidly expanding. The aim of this manuscript is to summarize the recent advances regarding the immune system involvement in ALS, with particular attention to clinical translation. We focus on the potential pathophysiologic mechanism of the immune system in ALS, discussing local and systemic factors (blood, cerebrospinal fluid, and microbiota) that influence ALS onset and progression in animal models and people. We also explore the potential of Positron Emission Tomography to detect neuroinflammation in vivo, and discuss ongoing clinical trials of therapies targeting the immune system. With validation in human patients, new evidence in this emerging field will serve to identify novel therapeutic targets and provide realistic hope for personalized treatment strategies.

CXCL13/CXCR5 signalling is pivotal to preserve motor neurons in amyotrophic lateral sclerosis

BACKGROUND

CXCL13 is a B and T lymphocyte chemokine that mediates neuroinflammation through its receptor CXCR5. This chemokine is highly expressed by motoneurons (MNs) in Amyotrophic Lateral Sclerosis (ALS) SOD1G93A (mSOD1) mice during the disease, particularly in fast-progressing mice. Accordingly, in this study, we investigated the role of this chemokine in ALS.

METHODS

We used in vitro and in vivo experimental paradigms derived from ALS mice and patients to investigate the expression level and distribution of CXCL13/CXCR5 axis and its role in MN death and disease progression. Moreover, we compared the levels of CXCL13 in the CSF and serum of ALS patients and controls.

FINDINGS

CXCL13 and CXCR5 are overexpressed in the spinal MNs and peripheral axons in mSOD1 mice. CXCL13 inhibition in the CNS of ALS mice resulted in the exacerbation of motor impairment (n = 4/group;Mean_Diff.=27.81) and decrease survival (n = 14_Treated:19.2 ± 1.05wks, n = 17_Controls:20.2 ± 0.6wks; 95% CI: 0.4687-1.929). This was corroborated by evidence from primary spinal cultures where the inhibition or activation of CXCL13 exacerbated or prevented the MN loss. Besides, we found that CXCL13/CXCR5 axis is overexpressed in the spinal cord MNs of ALS patients, and CXCL13 levels in the CSF discriminate ALS (n = 30) from Multiple Sclerosis (n = 16) patients with a sensitivity of 97.56%.

INTERPRETATION

We hypothesise that MNs activate CXCL13 signalling to attenuate CNS inflammation and prevent the neuromuscular denervation. The low levels of CXCL13 in the CSF of ALS patients might reflect the MN dysfunction, suggesting this chemokine as a potential clinical adjunct to discriminate ALS from other neurological diseases.

FUNDING

Vaccinex, Inc.; Regione Lombardia (TRANS-ALS).

5'ValCAC tRNA fragment generated as part of a protective angiogenin response provides prognostic value in amyotrophic lateral sclerosis

Loss-of-function mutations in the ribonuclease angiogenin are associated with amyotrophic lateral sclerosis. Angiogenin has been shown to cleave transfer RNAs during stress to produce ‘transfer-derived stress-induced RNAs’. Stress-induced tRNA cleavage is preserved from single-celled organisms to humans indicating it represents part of a highly conserved stress response. However, to date, the role of tRNA cleavage in amyotrophic lateral sclerosis remains to be fully elucidated. To this end, we performed small RNA sequencing on a human astrocytoma cell line to identify the complete repertoire of tRNA fragments generated by angiogenin. We found that only a specific subset of tRNAs is cleaved by angiogenin and identified 5′ValCAC transfer-derived stress-induced RNA to be secreted from neural cells. 5′ValCAC was quantified in spinal cord and serum from SOD1^G93A amyotrophic lateral sclerosis mouse models where we found it to be significantly elevated at symptom onset correlating with increased angiogenin expression, imbalanced protein translation initiation factors and slower disease progression. In amyotrophic lateral sclerosis patient serum samples, we found 5′ValCAC to be significantly higher in patients with slow disease progression, and interestingly, we find 5′ValCAC to hold prognostic value for amyotrophic lateral sclerosis patients. Here, we report that angiogenin cleaves a specific subset of tRNAs and provide evidence for 5′ValCAC as a prognostic biomarker in amyotrophic lateral sclerosis. We propose that increased serum 5′ValCAC levels indicate an enhanced angiogenin-mediated stress response within motor neurons that correlates with increased survival. These data suggest that the previously reported beneficial effects of angiogenin in SOD1^G93A mice may result from elevated levels of 5′ValCAC transfer RNA fragment.

Focus on the heterogeneity of amyotrophic lateral sclerosis

The clinical manifestations of amyotrophic lateral sclerosis (ALS) are variable in terms of age at disease onset, site of onset, progression of symptoms, motor neuron involvement, and the occurrence of cognitive and behavioral changes. Genetic background is a key determinant of the ALS phenotype. The mortality of the disease also varies with the ancestral origin of the affected population and environmental factors are likely to be associated with ALS at least within some cohorts. Disease heterogeneity is likely underpinned by the presence of different pathogenic mechanisms. A variety of ALS animal models can be informative about the heterogeneity of the neuropathological or genetic aspects of the disease and can support the development of new therapeutic intervention. Evolving biomarkers can contribute to the identification of differing genotypes and phenotypes, and can be used to explore whether genotypic and phenotypic differences in animal models might help to provide a better definition of the heterogeneity of ALS in humans. These include neurofilaments, peripheral blood mononuclear cells, extracellular vesicles, microRNA and imaging findings. These biomarkers might predict not only the development of the disease, but also the variability in progression, although robust validation is required. A promising area of progress in modeling the heterogeneity of human ALS is represented by the use of human induced pluripotent stem cell (iPSCs)-derived motor neurons. Although the translational value of iPSCs remains unclear, this model is attractive in the perspective of replicating the heterogeneity of sporadic ALS as a first step toward a personalized medicine strategy.

Creatine Kinase and Progression Rate in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with no recognized clinical prognostic factor. Creatinine kinase (CK) increase in these patients is already described with conflicting results on prognosis and survival. In 126 ALS patients who were fast or slow disease progressors, CK levels were assayed for 16 months every 4 months in an observational case-control cohort study with prospective data collection conducted in Italy. CK was also measured at baseline in 88 CIDP patients with secondary axonal damage and in two mouse strains (129SvHSD and C57-BL) carrying the same SOD1G93A transgene expression but showing a fast (129Sv-SOD1G93A) and slow (C57-SOD1G93A) ALS progression rate. Higher CK was found in ALS slow progressors compared to fast progressors in T1, T2, T3, and T4, with a correlation with Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) scores. Higher CK was found in spinal compared to bulbar-onset patients. Transgenic and non-transgenic C57BL mice showed higher CK levels compared to 129SvHSD strain. At baseline mean CK was higher in ALS compared to CIDP. CK can predict the disease progression, with slow progressors associated with higher levels and fast progressors to lower levels, in both ALS patients and mice. CK is higher in ALS patients compared to patients with CIDP with secondary axonal damage; the higher levels of CK in slow progressors patients, but also in C57BL transgenic and non-transgenic mice designs CK as a predisposing factor for disease rate progression.

miR-129-5p: A key factor and therapeutic target in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a relentless and fatal neurological disease characterized by the selective degeneration of motor neurons. No effective therapy is available for this disease. Several lines of evidence indicate that alteration of RNA metabolism, including microRNA (miRNA) processing, is a relevant pathogenetic factor and a possible therapeutic target for ALS. Here, we showed that the abundance of components in the miRNA processing machinery is altered in a SOD1-linked cellular model, suggesting consequent dysregulation of miRNA biogenesis. Indeed, high-throughput sequencing of the small RNA fraction showed that among the altered miRNAs, miR-129-5p was increased in different models of SOD1-linked ALS and in peripheral blood cells of sporadic ALS patients. We demonstrated that miR-129-5p upregulation causes the downregulation of one of its targets: the RNA-binding protein ELAVL4/HuD. ELAVL4/HuD is predominantly expressed in neurons, where it controls several key neuronal mRNAs. Overexpression of pre-miR-129-1 inhibited neurite outgrowth and differentiation via HuD silencing in vitro, while its inhibition with an antagomir rescued the phenotype. Remarkably, we showed that administration of an antisense oligonucleotide (ASO) inhibitor of miR-129-5p to an ALS animal model, SOD1 (G93A) mice, result in a significant increase in survival and improved the neuromuscular phenotype in treated mice. These results identify miR-129-5p as a therapeutic target that is amenable to ASO modulation for the treatment of ALS patients.

P2X7 activation enhances skeletal muscle metabolism and regeneration in SOD1G93A mouse model of amyotrophic lateral sclerosis

Muscle weakness plays an important role in neuromuscular disorders comprising amyotrophic lateral sclerosis (ALS). However, it is not established whether muscle denervation originates from the motor neurons, the muscles or more likely both. Previous studies have shown that the expression of the SOD1G93A mutation in skeletal muscles causes denervation of the neuromuscular junctions, inability to regenerate and consequent atrophy, all clear symptoms of ALS. In this work, we used SOD1G93A mice, a model that best mimics some pathological features of both familial and sporadic ALS, and we investigated some biological effects induced by the activation of the P2X7 receptor in the skeletal muscles. The P2X7, belonging to the ionotropic family of purinergic receptors for extracellular ATP, is abundantly expressed in the healthy skeletal muscles, where it controls cell duplication, differentiation, regeneration or death. In particular, we evaluated whether an in vivo treatment in SOD1G93A mice with the P2X7 specific agonist 2'(3')-O-(4-Benzoylbenzoyl) adenosine5'-triphosphate (BzATP) just before the onset of a pathological neuromuscular phenotype could exert beneficial effects in the skeletal muscles. Our findings indicate that stimulation of P2X7 improves the innervation and metabolism of myofibers, moreover elicits the proliferation/differentiation of satellite cells, thus preventing the denervation atrophy of skeletal muscles in SOD1G93A mice. Overall, this study suggests that a P2X7-targeted and site-specific modulation might be a strategy to interfere with the complex multifactorial and multisystem nature of ALS.

Spinal Cord Metabolic Signatures in Models of Fast- and Slow-Progressing SOD1G93A Amyotrophic Lateral Sclerosis

The rate of disease progression in amyotrophic lateral sclerosis (ALS) is highly variable, even between patients with the same genetic mutations. Metabolic alterations may affect disease course variability in ALS patients, but challenges in identifying the preclinical and early phases of the disease limit our understanding of molecular mechanisms underlying differences in the rate of disease progression. We examined effects of SOD1^G93A on thoracic and lumbar spinal cord metabolites in two mouse ALS models with different rates of disease progression: the transgenic SOD1^G93A-C57BL/6JOlaHsd (C57-G93A, slow progression) and transgenic SOD1^G93A-129SvHsd (129S-G93A, fast progression) strains. Samples from three timepoints (presymptomatic, disease onset, and late stage disease) were analyzed using Gas Chromatography-Mass Spectrometry metabolomics. Tissue metabolome differences in the lumbar spinal cord were driven primarily by mouse genetic background, although larger responses were observed in metabolic trajectories after the onset of symptoms. The significantly affected lumbar spinal cord metabolites were involved in energy and lipid metabolism. In the thoracic spinal cord, metabolic differences related to genetic background, background-SOD1 genotype interactions, and longitudinal SOD1^G93A effects. The largest responses in thoracic spinal cord metabolic trajectories related to SOD1^G93A effects before onset of visible symptoms. More metabolites were significantly affected in the thoracic segment, which were involved in energy homeostasis, neurotransmitter synthesis and utilization, and the oxidative stress response. We find evidence that initial metabolic alterations in SOD1^G93A mice confer disadvantages for maintaining neuronal viability under ALS-related stressors, with slow-progressing C57-G93A mice potentially having more favorable spinal cord bioenergetic profiles than 129S-G93A. These genetic background-associated metabolic differences together with the different early metabolic responses underscore the need to better characterize the impact of germline genetic variation on cellular responses to ALS gene mutations both before and after the onset of symptoms in order to understand their impact on disease development.

A pilot trial of RNS60 in amyotrophic lateral sclerosis

INTRODUCTION

RNS60 is a novel immune-modulatory agent that has shown neuroprotective effects in amytrophic lateral sclerosis (ALS) preclinical models. RNS60 is administered by weekly intravenous infusion and daily nebulization. The objective of this pilot open-label trial was to test the feasibility, safety, and tolerability of long-term RNS60 administration in ALS patients.

METHODS

The planned treatment duration was 23 weeks and the primary outcomes were safety and tolerability. Secondary outcomes included PBR28 positron emission tomography (PET) imaging and plasma biomarkers of inflammation.

RESULTS

Sixteen participants with ALS received RNS60 and 13 (81%) completed 23 weeks of RNS60 treatment. There were no serious adverse events and no participants withdrew from the trial due to drug-related adverse events. There were no significant changes in the biomarkers.

DISCUSSION

Long-term RNS60 administration was safe and well-tolerated. A large, multicenter, phase II trial of RNS60 is currently enrolling participants to test the effects of RNS60 on ALS biomarkers and disease progression. Muscle Nerve 59:303-308, 2019.

Tissue-enhanced plasma proteomic analysis for disease stratification in amyotrophic lateral sclerosis

Background

It is unclear to what extent pre-clinical studies in genetically homogeneous animal models of amyotrophic lateral sclerosis (ALS), an invariably fatal neurodegenerative disorder, can be informative of human pathology. The disease modifying effects in animal models of most therapeutic compounds have not been reproduced in patients. To advance therapeutics in ALS, we need easily accessible disease biomarkers which can discriminate across the phenotypic variants observed in ALS patients and can bridge animal and human pathology. Peripheral blood mononuclear cells alterations reflect the rate of progression of the disease representing an ideal biological substrate for biomarkers discovery.

Methods

We have applied TMTcalibrator™, a novel tissue-enhanced bio fluid mass spectrometry technique, to study the plasma proteome in ALS, using peripheral blood mononuclear cells as tissue calibrator. We have tested slow and fast progressing SOD1G93A mouse models of ALS at a pre-symptomatic and symptomatic stage in parallel with fast and slow progressing ALS patients at an early and late stage of the disease. Immunoassays were used to retest the expression of relevant protein candidates.

Results

The biological features differentiating fast from slow progressing mouse model plasma proteomes were different from those identified in human pathology, with only processes encompassing membrane trafficking with translocation of GLUT4, innate immunity, acute phase response and cytoskeleton organization showing enrichment in both species. Biological processes associated with senescence, RNA processing, cell stress and metabolism, major histocompatibility complex-II linked immune-reactivity and apoptosis (early stage) were enriched specifically in fast progressing ALS patients. Immunodetection confirmed regulation of the immunosenescence markers Galectin-3, Integrin beta 3 and Transforming growth factor beta-1 in plasma from pre-symptomatic and symptomatic transgenic animals while Apolipoprotein E differential plasma expression provided a good separation between fast and slow progressing ALS patients.

Conclusions

These findings implicate immunosenescence and metabolism as novel targets for biomarkers and therapeutic discovery and suggest immunomodulation as an early intervention. The variance observed in the plasma proteomes may depend on different biological patterns of disease progression in human and animal model.

Electronic supplementary material

The online version of this article (10.1186/s13024-018-0292-2) contains supplementary material, which is available to authorized users.

Counteracting roles of MHCI and CD8+ T cells in the peripheral and central nervous system of ALS SOD1G93A mice

BACKGROUND

The major histocompatibility complex I (MHCI) is a key molecule for the interaction of mononucleated cells with CD8⁺T lymphocytes. We previously showed that MHCI is upregulated in the spinal cord microglia and motor axons of transgenic SOD1^G93A mice.

METHODS

To assess the role of MHCI in the disease, we examined transgenic SOD1^G93A mice crossbred with β2 microglobulin-deficient mice, which express little if any MHCI on the cell surface and are defective for CD8⁺ T cells.

RESULTS

The lack of MHCI and CD8⁺ T cells in the sciatic nerve affects the motor axon stability, anticipating the muscle atrophy and the disease onset. In contrast, MHCI depletion in resident microglia and the lack of CD8⁺ T cell infiltration in the spinal cord protect the cervical motor neurons delaying the paralysis of forelimbs and prolonging the survival of SOD1^G93A mice.

CONCLUSIONS

We provided straightforward evidence for a dual role of MHCI in the peripheral nervous system (PNS) compared to the CNS, pointing out regional and temporal differences in the clinical responses of ALS mice. These findings offer a possible explanation for the failure of systemic immunomodulatory treatments and suggest new potential strategies to prevent the progression of ALS.

RNS60 exerts therapeutic effects in the SOD1 ALS mouse model through protective glia and peripheral nerve rescue

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that affects the motor neuromuscular system leading to complete paralysis and premature death. The multifactorial nature of ALS that involves both cell-autonomous and non-cell-autonomous processes contributes to the lack of effective therapies, usually targeted to a single pathogenic mechanism. RNS60, an experimental drug containing oxygenated nanobubbles generated by modified Taylor-Couette-Poiseuille flow with elevated oxygen pressure, has shown anti-inflammatory and neuroprotective properties in different experimental paradigms. Since RNS60 interferes with multiple cellular mechanisms known to be involved in ALS pathology, we evaluated its effect in in vitro and in vivo models of ALS.

METHODS

Co-cultures of primary microglia/spinal neurons exposed to LPS and astrocytes/spinal neurons from SOD1^G93A mice were used to examine the effect of RNS60 or normal saline (NS) on the selective motor neuron degeneration. Transgenic SOD1^G93A mice were treated with RNS60 or NS (300 μl/mouse intraperitoneally every other day) starting at the disease onset and examined for disease progression as well as pathological and biochemical alterations.

RESULTS

RNS60 protected motor neurons in in vitro paradigms and slowed the disease progression of C57BL/6-SOD1^G93A mice through a significant protection of spinal motor neurons and neuromuscular junctions. This was mediated by the (i) activation of an antioxidant response and generation of an anti-inflammatory environment in the spinal cord; (ii) activation of the PI3K-Akt pro-survival pathway in the spinal cord and sciatic nerves; (iii) reduced demyelination of the sciatic nerves; and (iv) elevation of peripheral CD4+/Foxp3+ T regulatory cell numbers. RNS60 did not show the same effects in 129Sv-SOD1^G93A mice, which are unable to activate a protective immune response.

CONCLUSION

RNS60 demonstrated significant therapeutic efficacy in C57BL/6-SOD1^G93A mice by virtue of its effects on multiple disease mechanisms in motor neurons, glial cells, and peripheral immune cells. These findings, together with the excellent clinical safety profile, make RNS60 a promising candidate for ALS therapy and support further studies to unravel its molecular mechanism of action. In addition, the differences in efficacy of RNS60 in SOD1^G93A mice of different strains may be relevant for identifying potential markers to predict efficacy in clinical trials.

Multiple intracerebroventricular injections of human umbilical cord mesenchymal stem cells delay motor neurons loss but not disease progression of SOD1G93A mice

Stem cell therapy is considered a promising approach in the treatment of amyotrophic lateral sclerosis (ALS) and mesenchymal stem cells (MSCs) seem to be the most effective in ALS animal models. The umbilical cord (UC) is a source of highly proliferating fetal MSCs, more easily collectable than other MSCs. Recently we demonstrated that human (h) UC-MSCs, double labeled with fluorescent nanoparticles and Hoechst-33258 and transplanted intracerebroventricularly (ICV) into SOD1G93A transgenic mice, partially migrated into the spinal cord after a single injection. This prompted us to assess the effect of repeated ICV injections of hUC-MSCs on disease progression in SOD1G93A mice. Although no transplanted cells migrated to the spinal cord, a partial but significant protection of motor neurons (MNs) was found in the lumbar spinal cord of hUC-MSCs-treated SOD1G93A mice, accompanied by a shift from a pro-inflammatory (IL-6, IL-1β) to anti-inflammatory (IL-4, IL-10) and neuroprotective (IGF-1) environment in the lumbar spinal cord, probably linked to the activation of p-Akt survival pathway in both motor neurons and reactive astrocytes. However, this treatment neither prevented the muscle denervation nor delayed the disease progression of mice, emphasizing the growing evidence that protecting the motor neuron perikarya is not sufficient to delay the ALS progression.

Decreased Levels of Foldase and Chaperone Proteins Are Associated with an Early-Onset Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by a progressive upper and lower motor neuron degeneration. One of the peculiar clinical characteristics of ALS is the wide distribution in age of onset, which is probably caused by different combinations of intrinsic and exogenous factors. We investigated whether these modifying factors are converging into common pathogenic pathways leading either to an early or a late disease onset. This would imply the identification of phenotypic biomarkers, that can distinguish the two populations of ALS patients, and of relevant pathways to consider in a therapeutic intervention. Toward this aim a differential proteomic analysis was performed in peripheral blood mononuclear cells (PBMC) from a group of 16 ALS patients with an age of onset ≤55 years and a group of 16 ALS patients with an age of onset ≥75 years, and matched healthy controls. We identified 43 differentially expressed proteins in the two groups of patients. Gene ontology analysis revealed that there was a significant enrichment in annotations associated with protein folding and response to stress. We next validated a selected number of proteins belonging to this functional group in 85 patients and 83 age- and sex-matched healthy controls using immunoassays. The results of the validation study confirmed that there was a decreased level of peptidyl-prolyl cis-trans isomerase A (also known as cyclophilin A), heat shock protein HSP 90-alpha, 78 kDa glucose-regulated protein (also known as BiP) and protein deglycase DJ-1 in PBMC of ALS patients with an early onset. Similar results were obtained in PBMC and spinal cord from two SOD1^G93A mouse models with an early and late disease onset. This study suggests that a different ability to upregulate proteins involved in proteostasis, such as foldase and chaperone proteins, may be at the basis of a different susceptibility to ALS, putting forward the development of therapeutic approaches aiming at boosting the protein quality control system.

Altered Metabolic Profiles Associate with Toxicity in SOD1G93A Astrocyte-Neuron Co-Cultures

Non-cell autonomous processes involving astrocytes have been shown to contribute to motor neuron degeneration in amyotrophic lateral sclerosis. Mutant superoxide dismutase 1 (SOD1^G93A) expression in astrocytes is selectively toxic to motor neurons in co-culture, even when mutant protein is expressed only in astrocytes and not in neurons. To examine metabolic changes in astrocyte-spinal neuron co-cultures, we carried out metabolomic analysis by ¹H NMR spectroscopy of media from astrocyte-spinal neuron co-cultures and astrocyte-only cultures. We observed increased glucose uptake with SOD1^G93A expression in all co-cultures, but while co-cultures with only SOD1^G93A neurons had lower extracellular lactate, those with only SOD1^G93A astrocytes exhibited the reverse. Reduced branched-chain amino acid uptake and increased accumulation of 3-methyl-2-oxovalerate were observed in co-culture with only SOD1^G93A neurons while glutamate was reduced in all co-cultures expressing SOD1^G93A. The shifts in these coupled processes suggest a potential block in glutamate processing that may impact motor neuron survival. We also observed metabolic alterations which may relate to oxidative stress responses. Overall, the different metabolite changes observed with the two SOD1^G93A cell types highlight the role of the astrocyte-motor neuron interaction in the resulting metabolic phenotype, requiring further examination of altered met abolic pathways and their impact on motor neuron survival.

Immune response in peripheral axons delays disease progression in SOD1G93A mice

Background

Increasing evidence suggests that the immune system has a beneficial role in the progression of amyotrophic lateral sclerosis (ALS) although the mechanism remains unclear. Recently, we demonstrated that motor neurons (MNs) of C57SOD1^G93A mice with slow disease progression activate molecules classically involved in the cross-talk with the immune system. This happens a lot less in 129SvSOD1^G93A mice which, while expressing the same amount of transgene, had faster disease progression and earlier axonal damage. The present study investigated whether and how the immune response is involved in the preservation of motor axons in the mouse model of familial ALS with a more benign disease course.

Methods

First, the extent of axonal damage, Schwann cell proliferation, and neuromuscular junction (NMJ) denervation were compared between the two ALS mouse models at the disease onset. Then, we compared the expression levels of different immune molecules, the morphology of myelin sheaths, and the presence of blood-derived immune cell infiltrates in the sciatic nerve of the two SOD1G93A mouse strains using immunohistochemical, immunoblot, quantitative reverse transcription PCR, and rotating-polarization Coherent Anti-Stokes Raman Scattering techniques.

Results

Muscle denervation, axonal dysregulation, and myelin disruption together with reduced Schwann cell proliferation are prominent in 129SvSOD1^G93A compared to C57SOD1^G93A mice at the disease onset, and this correlates with a faster disease progression in the first strain. On the contrary, a striking increase of immune molecules such as CCL2, MHCI, and C3 was seen in sciatic nerves of slow progressor C57SOD1^G93A mice and this was accompanied by heavy infiltration of CD8⁺ T lymphocytes and macrophages. These phenomena were not detectable in the peripheral nervous system of fast-progressing mice.

Conclusions

These data show for the first time that damaged MNs in SOD1-related ALS actively recruit immune cells in the peripheral nervous system to delay muscle denervation and prolong the lifespan. On the contrary, the lack of this response has a negative impact on the disease course.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0732-2) contains supplementary material, which is available to authorized users.

NG2, a common denominator for neuroinflammation, blood-brain barrier alteration, and oligodendrocyte precursor response in EAE, plays a role in dendritic cell activation

In adult CNS, nerve/glial-antigen 2 (NG2) is expressed by oligodendrocyte progenitor cells (OPCs) and is an early marker of pericyte activation in pathological conditions. NG2 could, therefore, play a role in experimental autoimmune encephalomyelitis (EAE), a disease associated with increased blood–brain barrier (BBB) permeability, inflammatory infiltrates, and CNS damage. We induced EAE in NG2 knock-out (NG2KO) mice and used laser confocal microscopy immunofluorescence and morphometry to dissect the effect of NG2 KO on CNS pathology. NG2KO mice developed milder EAE than their wild-type (WT) counterparts, with less intense neuropathology associated with a significant improvement in BBB stability. In contrast to WT mice, OPC numbers did not change in NG2KO mice during EAE. Through FACS and confocal microscopy, we found that NG2 was also expressed by immune cells, including T cells, macrophages, and dendritic cells (DCs). Assessment of recall T cell responses to the encephalitogen by proliferation assays and ELISA showed that, while WT and NG2KO T cells proliferated equally to the encephalitogenic peptide MOG35-55, NG2KO T cells were skewed towards a Th2-type response. Because DCs could be responsible for this effect, we assessed their expression of IL-12 by PCR and intracellular FACS. IL-12-expressing CD11c+ cells were significantly decreased in MOG35-55-primed NG2KO lymph node cells. Importantly, in WT mice, the proportion of IL-12-expressing cells was significantly lower in CD11c+ NG2- cells than in CD11c+ NG2+ cells. To assess the relevance of NG2 at immune system and CNS levels, we induced EAE in bone-marrow chimeric mice, generated with WT recipients of NG2KO bone-marrow cells and vice versa. Regardless of their original phenotype, mice receiving NG2KO bone marrow developed milder EAE than those receiving WT bone marrow. Our data suggest that NG2 plays a role in EAE not only at CNS/BBB level, but also at immune response level, impacting on DC activation and thereby their stimulation of reactive T cells, through controlling IL-12 expression.

Major Histocompatibility Complex I Expression by Motor Neurons and Its Implication in Amyotrophic Lateral Sclerosis

Neuronal expression of major histocompatibility complex I (MHCI)-related molecules in adults and during CNS diseases is involved in the synaptic plasticity and axonal regeneration with mechanisms either dependent or independent of their immune functions. Motor neurons are highly responsive in triggering the expression of MHCI molecules during normal aging or following insults and diseases, and this has implications in the synaptic controls, axonal regeneration, and neuromuscular junction stability of these neurons. We recently reported that MHCI and immunoproteasome are strongly activated in spinal motor neurons and their peripheral motor axon in a mouse model of familial amyotrophic lateral sclerosis (ALS) during the course of the disease. This response was prominent in ALS mice with slower disease progression in which the axonal structure and function was better preserved than in fast-progressing mice. This review summarizes and discusses our observations in the light of knowledge about the possible role of MHCI in motor neurons providing additional insight into the pathophysiology of ALS.

New Insights on the Mechanisms of Disease Course Variability in ALS from Mutant SOD1 Mouse Models

Amyotrophic Lateral Sclerosis (ALS) is a heterogeneous disease in terms of progression rate and survival. This is probably one of the reasons for the failure of many clinical trials and the lack of effective therapies. Similar variability is also seen in SOD1(G93A) mouse models based on their genetic background. For example, when the SOD1(G93A) transgene is expressed in C57BL6 background the phenotype is mild with slower disease progression than in the 129Sv mice expressing the same amount of transgene but showing faster progression and shorter lifespan. This review summarizes and discusses data obtained from the analysis of these two mouse models under different aspects such as the motor phenotype, neuropathological alterations in the central nervous system (CNS) and peripheral nervous system (PNS) and the motor neuron autonomous and non-cell autonomous mechanisms with the aim of finding elements to explain the different rates of disease progression. We also discuss the identification of promising prognostic biomarkers by comparative analysis of the two ALS mouse models. This analysis might possibly suggest new strategies for effective therapeutic intervention in ALS to slow significantly or even block the course of the disease.

ALS mouse model SOD1G93A displays early pathology of sensory small fibers associated to accumulation of a neurotoxic splice variant of peripherin

Growing evidence suggests that amyotrophic lateral sclerosis (ALS) is a multisystem neurodegenerative disease that primarily affects motor neurons and, though less evidently, other neuronal systems. About 75% of sporadic and familial ALS patients show a subclinical degeneration of small-diameter fibers, as measured by loss of intraepidermal nerve fibers (IENFs), but the underlying biological causes are unknown. Small-diameter fibers are derived from small-diameter sensory neurons, located in dorsal root ganglia (DRG), whose biochemical hallmark is the expression of type III intermediate filament peripherin. We tested here the hypothesis that small-diameter DRG neurons of ALS mouse model SOD1(G93A)suffer from axonal stress and investigated the underlying molecular mechanism. We found that SOD1(G93A)mice display small fiber pathology, as measured by IENF loss, which precedes the onset of the disease. In vitro small-diameter DRG neurons of SOD1(G93A)mice show axonal stress features and accumulation of a peripherin splice variant, named peripherin56, which causes axonal stress through disassembling light and medium neurofilament subunits (NFL and NFM, respectively). Our findings first demonstrate that small-diameter DRG neurons of the ALS mouse model SOD1(G93A)display axonal stress in vitro and in vivo, thus sustaining the hypothesis that the effects of ALS disease spread beyond motor neurons. These results suggest a molecular mechanism for the small fiber pathology found in ALS patients. Finally, our data agree with previous findings, suggesting a key role of peripherin in the ALS pathogenesis, thus highlighting that DRG neurons mirror some dysfunctions found in motor neurons.

Comparative Magnetic Resonance Imaging and Histopathological Correlates in Two SOD1 Transgenic Mouse Models of Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS) is a progressive and fatal disease due to motoneuron degeneration. Magnetic resonance imaging (MRI) is becoming a promising non-invasive approach to monitor the disease course but a direct correlation with neuropathology is not feasible in human. Therefore in this study we aimed to examine MRI changes in relation to histopathology in two mouse models of ALS (C57BL6/J and 129S2/SvHsd SOD1G93A mice) with different disease onset and progression. A longitudinal in vivo analysis of T2 maps, compared to ex vivo histological changes, was performed on cranial motor nuclei. An increased T2 value was associated with a significant tissue vacuolization that occurred prior to motoneuron loss in the cranial nuclei of C57 SOD1G93A mice. Conversely, in 129Sv SOD1G93A mice, which exhibit a more severe phenotype, MRI detected a milder increase of T2 value, associated with a milder vacuolization. This suggests that alteration within brainstem nuclei is not predictive of a more severe phenotype in the SOD1G93A mouse model. Using an ex vivo paradigm, Diffusion Tensor Imaging was also applied to study white matter spinal cord degeneration. In contrast to degeneration of cranial nuclei, alterations in white matter and axons loss reflected the different disease phenotype of SOD1G93A mice. The correspondence between MRI and histology further highlights the potential of MRI to monitor progressive motoneuron and axonal degeneration non-invasively in vivo. The identification of prognostic markers of the disease nevertheless requires validation in multiple models of ALS to ensure that these are not merely model-specific. Eventually this approach has the potential to lead to the development of robust and validated non-invasive imaging biomarkers in ALS patients, which may help to monitor the efficacy of therapies.

Longitudinal tracking of triple labeled umbilical cord derived mesenchymal stromal cells in a mouse model of Amyotrophic Lateral Sclerosis

The translational potential of cell therapy to humans requires a deep knowledge of the interaction between transplanted cells and host tissues. In this study, we evaluate the behavior of umbilical cord mesenchymal stromal cells (UC-MSCs), labeled with fluorescent nanoparticles, transplanted in healthy or early symptomatic transgenic SOD1G93A mice (a murine model of Amyotrophic Lateral Sclerosis). The double labeling of cells with nanoparticles and Hoechst-33258 enabled their tracking for a long time in both cells and tissues. Whole-body distribution of UC-MSCs was performed by in-vivo and ex-vivo analyses 1, 7, 21 days after single intravenous or intracerebroventricular administration. By intravenous administration cells were sequestered by the lungs and rapidly cleared by the liver. No difference in biodistribution was found among the two groups. On the other hand, UC-MSCs transplanted in lateral ventricles remained on the choroid plexus for the whole duration of the study even if decreasing in number. Few cells were found in the spinal cord of SOD1G93A mice exclusively. No migration in brain parenchyma was observed. These results suggest that the direct implantation in brain ventricles allows a prolonged permanence of cells close to the damaged areas and makes this method of tracking reliable for future studies of efficacy.

Lack of TNF-alpha receptor type 2 protects motor neurons in a cellular model of amyotrophic lateral sclerosis and in mutant SOD1 mice but does not affect disease progression

Changes in the homeostasis of tumor necrosis factor α (TNFα) have been demonstrated in patients and experimental models of amyotrophic lateral sclerosis (ALS). However, the contribution of TNFα to the development of ALS is still debated. TNFα is expressed by glia and neurons and acts through the membrane receptors TNFR1 and TNFR2, which may have opposite effects in neurodegeneration. We investigated the role of TNFα and its receptors in the selective motor neuron death in ALS in vitro and in vivo. TNFR2 expressed by astrocytes and neurons, but not TNFR1, was implicated in motor neuron loss in primary SOD1-G93A co-cultures. Deleting TNFR2 from SOD1-G93A mice, there was partial but significant protection of spinal motor neurons, sciatic nerves, and tibialis muscles. However, no improvement of motor impairment or survival was observed. Since the sciatic nerves of SOD1-G93A/TNFR2-/- mice showed high phospho-TAR DNA-binding protein 43 (TDP-43) accumulation and low levels of acetyl-tubulin, two indices of axonal dysfunction, the lack of symptom improvement in these mice might be due to impaired function of rescued motor neurons. These results indicate the interaction between TNFR2 and membrane-bound TNFα as an innovative pathway involved in motor neuron death. Nevertheless, its inhibition is not sufficient to stop disease progression in ALS mice, underlining the complexity of this pathology. We show evidence of the involvement of neuronal and astroglial TNFR2 in the motor neuron degeneration in ALS. Both concur to cause motor neuron death in primary astrocyte/spinal neuron co-cultures. TNFR2 deletion partially protects motor neurons and sciatic nerves in SOD1-G93A mice but does not improve their symptoms and survival. However, TNFR2 could be a new target for multi-intervention therapies.

Metabolomic Analysis Reveals Increased Aerobic Glycolysis and Amino Acid Deficit in a Cellular Model of Amyotrophic Lateral Sclerosis

Defects in energy metabolism are potential pathogenic mechanisms in amyotrophic lateral sclerosis (ALS), a rapidly fatal disease with no cure. The mechanisms through which this occurs remain elusive and their understanding may prove therapeutically useful. We used metabolomics and stable isotope tracers to examine metabolic changes in a well-characterized cell model of familial ALS, the motor neuronal NSC-34 line stably expressing human wild-type Cu/Zn superoxide dismutase (wtSOD1) or mutant G93A (G93ASOD1). Our findings indicate that wt and G93ASOD1 expression both enhanced glucose metabolism under serum deprivation. However, in wtSOD1 cells, this phenotype increased supply of amino acids for protein and glutathione synthesis, while in G93ASOD1 cells it was associated with death, aerobic glycolysis, and a broad dysregulation of amino acid homeostasis. Aerobic glycolysis was mainly due to induction of pyruvate dehydrogenase kinase 1. Our study thus provides novel insight into the role of deranged energy metabolism as a cause of poor adaptation to stress and a promoter of neural cell damage in the presence of mutant SOD1. Furthermore, the metabolic alterations we report may help explain why mitochondrial dysfunction and impairment of the endoplasmic reticulum stress response are frequently seen in ALS.

Peptidylprolyl isomerase A governs TARDBP function and assembly in heterogeneous nuclear ribonucleoprotein complexes

Peptidylprolyl isomerase A (PPIA), also known as cyclophilin A, is a multifunctional protein with peptidyl-prolyl cis-trans isomerase activity. PPIA is also a translational biomarker for amyotrophic lateral sclerosis, and is enriched in aggregates isolated from amyotrophic lateral sclerosis and frontotemporal lobar degeneration patients. Its normal function in the central nervous system is unknown. Here we show that PPIA is a functional interacting partner of TARDBP (also known as TDP-43). PPIA regulates expression of known TARDBP RNA targets and is necessary for the assembly of TARDBP in heterogeneous nuclear ribonucleoprotein complexes. Our data suggest that perturbation of PPIA/TARDBP interaction causes 'TDP-43' pathology. Consistent with this model, we show that the PPIA/TARDBP interaction is impaired in several pathological conditions. Moreover, PPIA depletion induces TARDBP aggregation, downregulates HDAC6, ATG7 and VCP, and accelerates disease progression in the SOD1(G93A) mouse model of amyotrophic lateral sclerosis. Targeting the PPIA/TARDBP interaction may represent a novel therapeutic avenue for conditions involving TARDBP/TDP-43 pathology, such as amyotrophic lateral sclerosis and frontotemporal lobar degeneration.

Differences in protein quality control correlate with phenotype variability in 2 mouse models of familial amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a disease of variable severity in terms of speed of progression of the disease course. We found a similar variability in disease onset and progression of 2 familial ALS mouse strains, despite the fact that they carry the same transgene copy number and express the same amount of mutant SOD1G93A messenger RNA and protein in the central nervous system. Comparative analysis of 2 SOD1G93A mouse strains highlights differences associated with the disease severity that are unrelated to the degree of motor neuron loss but that appear to promote early dysfunction of these cells linked to protein aggregation. Features of fast progressing phenotype are (1) abundant protein aggregates containing mutant SOD1 and multiple chaperones; (2) low basal expression of the chaperone alpha-B-crystallin (CRYAB) and β5 subunits of proteasome; and (3) downregulation of proteasome subunit expression at disease onset. In contrast, high levels of functional chaperones such as cyclophillin-A and CRYAB, combined with delayed alteration of expression of proteasome subunits and the sequestration of TDP43 into aggregates, are features associated with a more slowly progressing pathology. These data support the hypothesis that impairment of protein homeostasis caused by low-soluble chaperone levels, together with malfunction of the proteasome degradation machinery, contributes to accelerate motor neuron dysfunction and progression of disease symptoms. Therefore, modulating the activity of these systems could represent a rational therapeutic strategy for slowing down disease progression in SOD1-related ALS.

Human SOD1-G93A specific distribution evidenced in murine brain of a transgenic model for amyotrophic lateral sclerosis by MALDI imaging mass spectrometry

Amyotrophic lateral sclerosis (ALS) is a progressive, fatal neurodegenerative disease caused by the degeneration of motor neurons. The transgenic mouse model carrying the human SOD1G93A mutant gene (hSOD1G93A mouse) represents one of the most reliable and widely used model of this pathology. In the present work, the innovative technique of matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) was applied in the study of pathological alterations at the level of small brain regions such as facial and trigeminal nuclei, which in rodents are extremely small and would be difficult to analyze with classical proteomics approaches. Comparing slices from three mice groups (transgenic hSOD1G93A, transgenic hSOD1WT, and nontransgenic, Ntg), this technique allowed us to evidence the accumulation of hSOD1G93A in the facial and trigeminal nuclei, where it generates aggregates. This phenomenon is likely to be correlated to the degeneration observed in these regions. Moreover, a statistical analysis allowed us to highlight other proteins as differentially expressed among the three mice groups analyzed. Some of them were identified by reverse-phase HPLC fractionation of extracted proteins and mass spectrometric analysis before and after trypsin digestion. In particular, the 40S ribosomal protein S19 (RPS19) was upregulated in the parenkyma and reactive glial cells in facial nuclei of hSOD1G93A mice when compared to transgenic hSOD1WT and nontransgenic ones.

Increased axonal ribosome numbers is an early event in the pathogenesis of amyotrophic lateral sclerosis

Myelinating glia cells support axon survival and functions through mechanisms independent of myelination, and their dysfunction leads to axonal degeneration in several diseases. In amyotrophic lateral sclerosis (ALS), spinal motor neurons undergo retrograde degeneration, and slowing of axonal transport is an early event that in ALS mutant mice occurs well before motor neuron degeneration. Interestingly, in familial forms of ALS, Schwann cells have been proposed to slow disease progression. We demonstrated previously that Schwann cells transfer polyribosomes to diseased and regenerating axons, a possible rescue mechanism for disease-induced reductions in axonal proteins. Here, we investigated whether elevated levels of axonal ribosomes are also found in ALS, by analysis of a superoxide dismutase 1 (SOD1)^G93A mouse model for human familial ALS and a patient suffering from sporadic ALS. In both cases, we found that the disorder was associated with an increase in the population of axonal ribosomes in myelinated axons. Importantly, in SOD1^G93A mice, the appearance of axonal ribosomes preceded the manifestation of behavioral symptoms, indicating that upregulation of axonal ribosomes occurs early in the pathogenesis of ALS. In line with our previous studies, electron microscopy analysis showed that Schwann cells might serve as a source of axonal ribosomes in the disease-compromised axons. The early appearance of axonal ribosomes indicates an involvement of Schwann cells early in ALS neuropathology, and may serve as an early marker for disease-affected axons, not only in ALS, but also for other central and peripheral neurodegenerative disorders.

Modeling amyotrophic lateral sclerosis in hSOD1 transgenic swine

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that occurs in two clinically indistinguishable forms: sporadic (SALS) and familial (FALS), the latter linked to several gene mutations, mostly inheritable in a dominant manner. Nearly 20% of FALS forms are linked to mutations in the Cu/Zn superoxide dismutase (SOD1) gene. Research on ALS relies on transgenic models and particularly on mice carrying a glycine-to-alanine conversion at the 93rd codon (G93A) of the hSOD1 gene. Although G93A transgenic mice have been widely employed in clinical trials and basic research, doubts have been recently raised from numerous reliable sources about their suitability to faithfully reproduce human disease. Besides, the scientific community has already foreseen swine as an attractive and alternative model to nonhuman primates for modeling human diseases due to closer anatomical, physiological and biochemical features of swine rather than rodents to humans. On this basis, we have produced the first swine ALS model by in vitro transfection of cultured somatic cells combined with somatic cell nuclear transfer (SCNT). To achieve this goal we developed a SOD1(G93A) (superoxide dismutase 1 mutated in Gly93-Ala) vector, capable of promoting a high and stable transgene expression in primary porcine adult male fibroblasts (PAF). After transfection, clonal selection and transgene expression level assessment, selected SOD1(G93A) PAF colonies were used as nuclei donors in SCNT procedures. SOD1(G93A) embryos were transferred in recipient sows, and pregnancies developed to term. A total of 5 piglets survived artificial hand raising and weaning and developed normally, reaching adulthood. Preliminary analysis revealed transgene integration and hSOD1(G93A) expression in swine tissues and 360° phenotypical characterization is ongoing. We believe that our SOD1(G93A) swine would provide an essential bridge between the fundamental work done in rodent models and the reality of treating ALS.

Transcriptomic indices of fast and slow disease progression in two mouse models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is heterogeneous with high variability in the speed of progression even in cases with a defined genetic cause such as superoxide dismutase 1 (SOD1) mutations. We reported that SOD1(G93A) mice on distinct genetic backgrounds (C57 and 129Sv) show consistent phenotypic differences in speed of disease progression and life-span that are not explained by differences in human SOD1 transgene copy number or the burden of mutant SOD1 protein within the nervous system. We aimed to compare the gene expression profiles of motor neurons from these two SOD1(G93A) mouse strains to discover the molecular mechanisms contributing to the distinct phenotypes and to identify factors underlying fast and slow disease progression. Lumbar spinal motor neurons from the two SOD1(G93A) mouse strains were isolated by laser capture microdissection and transcriptome analysis was conducted at four stages of disease. We identified marked differences in the motor neuron transcriptome between the two mice strains at disease onset, with a dramatic reduction of gene expression in the rapidly progressive (129Sv-SOD1(G93A)) compared with the slowly progressing mutant SOD1 mice (C57-SOD1(G93A)) (1276 versus 346; Q-value ≤ 0.01). Gene ontology pathway analysis of the transcriptional profile from 129Sv-SOD1(G93A) mice showed marked downregulation of specific pathways involved in mitochondrial function, as well as predicted deficiencies in protein degradation and axonal transport mechanisms. In contrast, the transcriptional profile from C57-SOD1(G93A) mice with the more benign disease course, revealed strong gene enrichment relating to immune system processes compared with 129Sv-SOD1(G93A) mice. Motor neurons from the more benign mutant strain demonstrated striking complement activation, over-expressing genes normally involved in immune cell function. We validated through immunohistochemistry increased expression of the C3 complement subunit and major histocompatibility complex I within motor neurons. In addition, we demonstrated that motor neurons from the slowly progressing mice activate a series of genes with neuroprotective properties such as angiogenin and the nuclear factor (erythroid-derived 2)-like 2 transcriptional regulator. In contrast, the faster progressing mice show dramatically reduced expression at disease onset of cell pathways involved in neuroprotection. This study highlights a set of key gene and molecular pathway indices of fast or slow disease progression which may prove useful in identifying potential disease modifiers responsible for the heterogeneity of human amyotrophic lateral sclerosis and which may represent valid therapeutic targets for ameliorating the disease course in humans.

Specific induction of Akt3 in spinal cord motor neurons is neuroprotective in a mouse model of familial amyotrophic lateral sclerosis

Evidence is accumulating that an imbalance between pathways for degeneration or survival in motor neurons may play a central role in mechanisms that lead to neurodegeneration in amyotrophic lateral sclerosis (ALS). We and other groups have observed that downregulation, or lack of induction, of the PI3K/Akt prosurvival pathway may be responsible for defective response of motor neurons to injury and their consequent cellular demise. Some of the neuroprotective effects mediated by growth factors may involve activation of Akt, but a proof of concept of Akt as a target for therapy is lacking. We demonstrate that specific expression of constitutively activated Akt3 in motor neurons through the use of the promoter of homeobox gene Hb9 prevents neuronal loss induced by SOD1.G93A both in vitro (in mixed neuron/astrocyte cocultures) and in vivo (in a mouse model of ALS). Inhibition of ASK1 and GSK3beta was involved in the neuroprotective effects of activated Akt3, further supporting the hypothesis that induction of Akt3 may be a key step in activation of pathways for survival in the attempt to counteract motor neuronal degeneration in ALS.

The omega-3 fatty acid eicosapentaenoic acid accelerates disease progression in a model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive fatal neurodegenerative disease characterised by loss of motor neurons that currently has no cure. Omega-3 polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA), have many health benefits including neuroprotective and myoprotective potential. We tested the hypothesis that a high level of dietary EPA could exert beneficial effects in ALS. The dietary exposure to EPA (300 mg/kg/day) in a well-established mouse model of ALS expressing the G93A superoxide dismutase 1 (SOD1) mutation was initiated at a pre-symptomatic or symptomatic stage, and the disease progression was monitored until the end stage. Daily dietary EPA exposure initiated at the disease onset did not significantly alter disease presentation and progression. In contrast, EPA treatment initiated at the pre-symptomatic stage induced a significantly shorter lifespan. In a separate group of animals sacrificed before the end stage, the tissue analysis showed that the vacuolisation detected in G93A-SOD1 mice was significantly increased by exposure to EPA. Although EPA did not alter motor neurone loss, EPA reversed the significant increase in activated microglia and the astrocytic activation seen in G93A-SOD1 mice. The microglia in the spinal cord of G93A-SOD1 mice treated with EPA showed a significant increase in 4-hydroxy-2-hexenal, a highly toxic aldehydic oxidation product of omega-3 fatty acids. These data show that dietary EPA supplementation in ALS has the potential to worsen the condition and accelerate the disease progression. This suggests that great caution should be exerted when considering dietary omega-3 fatty acid supplements in ALS patients.

Mutant copper-zinc superoxide dismutase (SOD1) induces protein secretion pathway alterations and exosome release in astrocytes: implications for disease spreading and motor neuron pathology in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is the most common motor neuron disease and is still incurable. The mechanisms leading to the selective motor neuron vulnerability are still not known. The interplay between motor neurons and astrocytes is crucial in the outcome of the disease. We show that mutant copper-zinc superoxide dismutase (SOD1) overexpression in primary astrocyte cultures is associated with decreased levels of proteins involved in secretory pathways. This is linked to a general reduction of total secreted proteins, except for specific enrichment in a number of proteins in the media, such as mutant SOD1 and valosin-containing protein (VCP)/p97. Because there was also an increase in exosome release, we can deduce that astrocytes expressing mutant SOD1 activate unconventional secretory pathways, possibly as a protective mechanism. This may help limit the formation of intracellular aggregates and overcome mutant SOD1 toxicity. We also found that astrocyte-derived exosomes efficiently transfer mutant SOD1 to spinal neurons and induce selective motor neuron death. We conclude that the expression of mutant SOD1 has a substantial impact on astrocyte protein secretion pathways, contributing to motor neuron pathology and disease spread.