Multiple System Atrophy Mouse Research Articles

Distinct forebrain regions define a dichotomous astrocytic profile in multiple system atrophy

The growing recognition of a dichotomous role of astrocytes in neurodegenerative processes has heightened the need for unraveling distinct astrocytic subtypes in neurological disorders. In multiple system atrophy (MSA), a rare, rapidly progressing atypical Parkinsonian disease characterized by increased astrocyte reactivity. However the specific contribution of astrocyte subtypes to neuropathology remains elusive. Hence, we first set out to profile glial fibrillary acidic protein levels in astrocytes across the human post mortem motor cortex, putamen, and substantia nigra of MSA patients and observed an overall profound astrocytic response. Matching the post mortem human findings, a similar astrocytic phenotype was present in a transgenic MSA mouse model. Notably, MSA mice exhibited a decreased expression of the glutamate transporter 1 and glutamate aspartate transporter in the basal ganglia, but not the motor cortex. We developed an optimized astrocyte isolation protocol based on magnetic-activated cell sorting via ATPase Na+/K+ transporting subunit beta 2 and profiled the transcriptomic landscape of striatal and cortical astrocytes in transgenic MSA mice. The gene expression profile of astrocytes in the motor cortex displayed an anti-inflammatory signature with increased oligodendroglial and pro-myelinogenic expression pattern. In contrast, striatal astrocytes were defined by elevated pro-inflammatory transcripts accompanied by dysregulated genes involved in homeostatic functions for lipid and calcium metabolism. These findings provide new insights into a region-dependent, dichotomous astrocytic response—potentially beneficial in the cortex and harmful in the striatum—in MSA suggesting a differential role of astrocytes in MSA-related neurodegenerative processes.

Pharmacological inhibition of FABP7 by MF 6 counteracts cerebellum dysfunction in an experimental multiple system atrophy mouse model.

Multiple system atrophy (MSA) is a rare, fatal neurodegenerative disease characterized by the accumulation of misfolded α-synuclein (αSyn) in glial cells, leading to the formation of glial cytoplasmic inclusions (GCI). We previous found that glial fatty acid-binding protein 7 (FABP7) played a crucial role in alpha-synuclein (αSyn) aggregation and toxicity in oligodendrocytes, inhibition of FABP7 by a specific inhibitor MF 6 reduced αSyn aggregation and enhanced cell viability in cultured cell lines and mouse oligodendrocyte progenitor cells. In this study we investigated whether MF 6 ameliorated αSyn-associated pathological processes in PLP-hαSyn transgenic mice (PLP-αSyn mice), a wildly used MSA mouse model with overexpressing αSyn in oligodendroglia under the proteolipid protein (PLP) promoter. PLP-αSyn mice were orally administered MF6 (0.1, 1 mg ·kg-1 ·d-1) for 32 days starting from the age of 6 months. We showed that oral administration of MF 6 significantly improved motor function assessed in a pole test, and reduced αSyn aggregation levels in both cerebellum and basal ganglia of PLP-αSyn mice. Moreover, MF 6 administration decreased oxidative stress and inflammation levels, and improved myelin levels and Purkinje neuron morphology in the cerebellum. By using mouse brain tissue slices and αSyn aggregates-treated KG-1C cells, we demonstrated that MF 6 reduced αSyn propagation to Purkinje neurons and oligodendrocytes through regulating endocytosis. Overall, these results suggest that MF 6 improves cerebellar functions in MSA by inhibiting αSyn aggregation and propagation. We conclude that MF 6 is a promising compound that warrants further development for the treatment of MSA.

Epsin2, a novel target for multiple system atrophy therapy via α-synuclein/FABP7 propagation.

Multiple system atrophy (MSA) is a neurodegenerative disease characterized by the accumulation of misfolded α-synuclein (αSyn) and myelin disruption. However, the mechanism underlying αSyn accumulation in MSA brains remains unclear. Here, we aimed to identify epsin-2 as a potential regulator of αSyn propagation in MSA brains. In the MSA mouse model, PLP-hαSyn mice, and FABP7/αSyn hetero-aggregate-injected mice, we initially discovered that fatty acid-binding protein 7 (FABP7) is related to MSA development and forms hetero-aggregates with αSyn, which exhibit stronger toxicity than αSyn aggregates. Moreover, the injected FABP7/αSyn hetero-aggregates in mice selectively accumulated only in oligodendrocytes and Purkinje neurons, causing cerebellar dysfunction. Furthermore, bioinformatic analyses of whole blood from MSA patients and FABP7 knockdown mice revealed that epsin-2, a protein expressed in both oligodendrocytes and Purkinje cells, could potentially regulate FABP7/αSyn hetero-aggregate propagation via clathrin-dependent endocytosis. Lastly, adeno-associated virus type 5-dependent epsin-2 knockdown mice exhibited decreased levels of αSyn aggregate accumulation in Purkinje neurons and oligodendrocytes, as well as improved myelin levels and Purkinje neuron function in the cerebellum and motor performance. These findings suggest that epsin-2 plays a significant role in αSyn accumulation in MSA, and we propose epsin-2 as a novel therapeutic target for MSA.

Therapeutic potential of iron modulating drugs in a mouse model of multiple system atrophy

Multiple System Atrophy (MSA) is a rare neurodegenerative synucleinopathy which leads to severe disability followed by death within 6–9 years of symptom onset. There is compelling evidence suggesting that biological trace metals like iron and copper play an important role in synucleinopathies like Parkinson's disease and removing excess brain iron using chelators could slow down the disease progression. In human MSA, there is evidence of increased iron in affected brain regions, but role of iron and therapeutic efficacy of iron-lowering drugs in pre-clinical models of MSA have not been studied.We studied age-related changes in iron metabolism in different brain regions of the PLP-αsyn mice and tested whether iron-lowering drugs could alleviate disease phenotype in aged PLP-αsyn mice. Iron content, iron-ferritin association, ferritin protein levels and copper-ceruloplasmin association were measured in prefrontal cortex, putamen, substantia nigra and cerebellum of 3, 8, and 20-month-old PLP-αsyn and age-matched non-transgenic mice. Moreover, 12-month-old PLP-αsyn mice were administered deferiprone or ceruloplasmin or vehicle for 2 months. At the end of treatment period, motor testing and stereological analyses were performed.We found iron accumulation and perturbed iron-ferritin interaction in substantia nigra, putamen and cerebellum of aged PLP-αsyn mice. Furthermore, we found significant reduction in ceruloplasmin-bound copper in substantia nigra and cerebellum of the PLP-αsyn mice. Both deferiprone and ceruloplasmin prevented decline in motor performance in aged PLP-αsyn mice and were associated with higher neuronal survival and reduced density of α-synuclein aggregates in substantia nigra.This is the first study to report brain iron accumulation in a mouse model of MSA. Our results indicate that elevated iron in MSA mice may result from ceruloplasmin dysfunction and provide evidence that targeting iron in MSA could be a viable therapeutic option.

ATH434 Reduces α-Synuclein-Related Neurodegeneration in a Murine Model of Multiple System Atrophy.

Multiple system atrophy (MSA) is a fatal neurodegenerative disorder characterized by aggregated α-synuclein (α-syn) in oligodendrocytes and accompanied by striatonigral and olivopontocerebellar degeneration and motor symptoms. Key features of MSA are replicated in the PLP-α-syn transgenic mouse, including progressive striatonigral degeneration and motor deterioration. There are currently no approved treatments for MSA. ATH434 is a novel, orally bioavailable brain penetrant small molecule inhibitor of α-syn aggregation. To characterize ATH434 for disease modification in a mouse model of MSA. Six-month-old PLP-α-syn mice (MSA mice) were ATH434-treated (ATH434 in food) or untreated (normal food) for 6 months. Motor behavior and numbers of nigral and striatal neurons were evaluated. α-syn aggregates and oligomers were quantified by immunohistochemical and western blot analyses. Microglial activation and neuroinflammation were assessed by histological and molecular analyses. Ferric iron in the Substantia nigra was evaluated with the Perls method. ATH434-treated mice demonstrated preservation of motor performance in MSA mice that was associated with neuroprotection of nigral and striatal neurons. The rescue of the phenotype correlated with the reduction of α-syn inclusions and oligomers in animals receiving ATH434. ATH434-treated mice exhibited significantly increased lysosomal activity of microglia without increased pro-inflammatory markers, suggesting a role in α-syn clearing. ATH434-treatment was associated with lower intracellular nigral iron levels. Our findings demonstrate the beneficial disease-modifying effect of ATH434 in oligodendroglial α-synucleinopathy on both the motor phenotype and neurodegenerative pathology in the PLP-α-syn transgenic mouse and support the development of ATH434 for MSA. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Human alpha-synuclein overexpressing MBP29 mice mimic functional and structural hallmarks of the cerebellar subtype of multiple system atrophy

Multiple system atrophy (MSA) is a rare, but fatal atypical parkinsonian disorder. The prototypical pathological hallmark are oligodendroglial cytoplasmic inclusions (GCIs) containing alpha-synuclein (α-syn). Currently, two MSA phenotypes are classified: the parkinsonian (MSA-P) and the cerebellar subtype (MSA-C), clinically characterized by predominant parkinsonism or cerebellar ataxia, respectively. Previous studies have shown that the transgenic MSA mouse model overexpressing human α-syn controlled by the oligodendroglial myelin basic protein (MBP) promoter (MBP29-hα-syn mice) mirrors crucial characteristics of the MSA-P subtype. However, it remains elusive, whether this model recapitulates important features of the MSA-C-related phenotype. First, we examined MSA-C-associated cerebellar pathology using human post-mortem tissue of MSA-C patients and controls. We observed the prototypical GCI pathology and a preserved number of oligodendrocytes in the cerebellar white matter (cbw) accompanied by severe myelin deficit, microgliosis, and a profound loss of Purkinje cells. Secondly, we phenotypically characterized MBP29-hα-syn mice using a dual approach: structural analysis of the hindbrain and functional assessment of gait. Matching the neuropathological features of MSA-C, GCI pathology within the cbw of MBP29-hα-syn mice was accompanied by a severe myelin deficit despite an increased number of oligodendrocytes and a high number of myeloid cells even at an early disease stage. Intriguingly, MBP29-hα-syn mice developed a significant loss of Purkinje cells at a more advanced disease stage. Catwalk XT gait analysis revealed decreased walking speed, increased stride length and width between hind paws. In addition, less dual diagonal support was observed toward more dual lateral and three paw support. Taken together, this wide-based and unsteady gait reflects cerebellar ataxia presumably linked to the cerebellar pathology in MBP29-hα-syn mice. In conclusion, the present study strongly supports the notion that the MBP29-hα-syn mouse model mimics important characteristics of the MSA-C subtype providing a powerful preclinical tool for evaluating future interventional strategies.

Shared Genetics of Multiple System Atrophy and Inflammatory Bowel Disease.

Background:Multiple system atrophy (MSA) is a rare neurodegenerative disease characterized by intracellular accumulations of α-synuclein and nerve cell loss in striatonigral and olivopontocerebellar structures. Epidemiological and clinical studies have reported potential involvement of autoimmune mechanisms in MSA pathogenesis. However, genetic etiology of this interaction remains unknown. We aimed to investigate genetic overlap between MSA and 7 autoimmune diseases and to identify shared genetic loci.Methods:Genome-wide association study summary statistics of MSA and 7 autoimmune diseases were combined in cross-trait conjunctional false discovery rate analysis to explore overlapping genetic background. Expression of selected candidate genes was compared in transgenic MSA mice and wild-type mice. Genetic variability of candidate genes was further investigated using independent whole-exome genotyping data from large cohorts of MSA and autoimmune disease patients and healthy controls.Results:We observed substantial polygenic overlap between MSA and inflammatory bowel disease and identified 3 shared genetic loci with leading variants upstream of the DENND1B and RSP04 genes, and in intron of the C7 gene. Further, the C7 gene showed significantly dysregulated expression in the degenerating midbrain of transgenic MSA mice compared with wild-type mice and had elevated burden of protein-coding variants in independent MSA and inflammatory bowel disease cohorts.Conclusion:Our study provides evidence of shared genetic etiology between MSA and inflammatory bowel disease with an important role of the C7 gene in both phenotypes, with the implication of immune and gut dysfunction in MSA pathophysiology.

A Pilot Microbiota Study in Parkinson's Disease Patients versus Control Subjects, and Effects of FTY720 and FTY720-Mitoxy Therapies in Parkinsonian and Multiple System Atrophy Mouse Models.

Background:Parkinson’s disease (PD) and multiple system atrophy (MSA) patients often suffer from gastrointestinal (GI) dysfunction and GI dysbiosis (microbial imbalance). GI dysfunction also occurs in mouse models of PD and MSA.Objectives:To assess gut dysfunction and dysbiosis in PD subjects as compared to controls, identify potential shared microbial taxa in humans and mouse models of PD and MSA, and to assess the effects of potential therapies on mouse GI microbiota.Methods:In this human pilot study, GI function was assessed by fecal consistency/frequency measured using the Bristol Stool Form Scale and GI transit time assessed using Sitzmarks pills and abdominal radiology. Human and mouse microbiota were analyzed by extracting fecal genomic DNA followed by 16S rRNA sequencing.Results:In our PD patients genera Akkermansia significantly increased while a trend toward increased Bifidobacterium and decreased Prevotella was observed. Families Bacteroidaceae and Lachnospiraceae and genera Prevotella and Bacteroides were detected in both humans and PD mice, suggesting potential shared biomarkers. In mice treated with the approved multiple sclerosis drug, FTY720, or with our FTY720-Mitoxy-derivative, we saw that FTY720 had little effect while FTY720-Mitoxy increased beneficial Ruminococcus and decreased Rickenellaceae family.Conclusion:Akkermansia and Prevotellaceae data reported by others were replicated in our human pilot study suggesting the use of those taxa as potential biomarkers for PD diagnosis. The effect of FTY720-Mitoxy on taxa Rikenellaceae and Ruminococcus and the relevance of S24-7 await further evaluation. It also remains to be determined if mouse microbiota have predictive power for human subjects.

FTY720-Mitoxy reduces synucleinopathy and neuroinflammation, restores behavior and mitochondria function, and increases GDNF expression in Multiple System Atrophy mouse models

Multiple system atrophy (MSA) is a fatal disorder with no effective treatment. MSA pathology is characterized by α-synuclein (aSyn) accumulation in oligodendrocytes, the myelinating glial cells of the central nervous system (CNS). aSyn accumulation in oligodendrocytes forms the pathognomonic glial cytoplasmic inclusions (GCIs) of MSA. MSA aSyn pathology is also associated with motor and autonomic dysfunction, including an impaired ability to sweat. MSA patients have abnormal CNS expression of glial-cell-line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF). Our prior studies using the parent compound FTY720, a food and drug administration (FDA) approved immunosuppressive for multiple sclerosis, reveal that FTY720 protects parkinsonian mice by increasing BDNF. Our FTY720-derivative, FTY720-Mitoxy, is known to increase expression of oligodendrocyte BDNF, GDNF, and nerve growth factor (NGF) but does not reduce levels of circulating lymphocytes as it is not phosphorylated so cannot modulate sphingosine 1 phosphate receptors (S1PRs). To preclinically assess FTY720-Mitoxy for MSA, we used mice expressing human aSyn in oligodendrocytes under a 2,’ 3′-cyclic nucleotide 3′-phosphodiesterase (CNP) promoter. CNP-aSyn transgenic (Tg) mice develop motor dysfunction between 7 and 9 mo, and progressive GCI pathology. Using liquid chromatography-mass spectrometry (LC-MS/MS) and enzymatic assays, we confirmed that FTY720-Mitoxy was stable and active. Vehicle or FTY720-Mitoxy (1.1 mg/kg/day) was delivered to wild type (WT) or Tg littermates from 8.5–11.5 mo by osmotic pump. We behaviorally assessed their movement by rotarod and sweat production by starch‑iodine test. Postmortem tissues were evaluated by qPCR for BDNF, GDNF, NGF and GDNF-receptor RET mRNA and for aSyn, BDNF, GDNF, and Iba1 protein by immunoblot. MicroRNAs (miRNAs) were also assessed by qPCR. FTY720-Mitoxy normalized movement, sweat function and soleus muscle mass in 11.5 mo Tg MSA mice. FTY720-Mitoxy also increased levels of brain GDNF and reduced brain miR-96-5p, a miRNA that acts to decrease GDNF expression. Moreover, FTY720-Mitoxy blocked aSyn pathology measured by sequential protein extraction and immunoblot, and microglial activation assessed by immunohistochemistry and immunoblot. In the 3-nitropropionic acid (3NP) toxin model of MSA, FTY720-Mitoxy protected movement and mitochondria in WT and CNP-aSyn Tg littermates. Our data confirm potent in vivo protection by FTY720-Mitoxy, supporting its further evaluation as a potential therapy for MSA and related synucleinopathies.

Transcription factor EB overexpression prevents neurodegeneration in experimental synucleinopathies.

The synucleinopathies Parkinson’s disease (PD) and Multiple system atrophy (MSA) — characterized by α-synuclein intracytoplasmic inclusions into, respectively, neurons and oligodendrocytes — are associated with impairment of the autophagy-lysosomal pathways (ALP). Increased expression of the master regulator of ALP, transcription factor EB (TFEB), is hypothesized to promote the clearance of WT α-synuclein and survival of dopaminergic neurons. Here, we explore the efficacy of targeted TFEB overexpression either in neurons or oligodendrocytes to reduce the pathological burden of α-synuclein in a PD rat model and a MSA mouse model. While TFEB neuronal expression was sufficient to prevent neurodegeneration in the PD model, we show that only TFEB oligodendroglial overexpression leads to neuroprotective effects in the MSA model. These beneficial effects were associated with a decreased accumulation of α-synuclein into oligodendrocytes through recovery of the ALP machinery. Our study demonstrates that the cell type where α-synuclein aggregates dictates the target of TFEB overexpression in order to be protective, paving the way for adapted therapies.

Insulin resistance and exendin-4 treatment for multiple system atrophy.

See Stayte and Vissel (doi:10.1093/awx064) for a scientific commentary on this article. Multiple system atrophy is a fatal sporadic adult-onset neurodegenerative disorder with no symptomatic or disease-modifying treatment available. The cytopathological hallmark of multiple system atrophy is the accumulation of α-synuclein aggregates in oligodendrocytes, forming glial cytoplasmic inclusions. Impaired insulin/insulin-like growth factor-1 signalling (IGF-1) and insulin resistance (i.e. decreased insulin/IGF-1) have been reported in other neurodegenerative disorders such as Alzheimer's disease. Increasing evidence also suggests impaired insulin/IGF-1 signalling in multiple system atrophy, as corroborated by increased insulin and IGF-1 plasma concentrations in multiple system atrophy patients and reduced IGF-1 brain levels in a transgenic mouse model of multiple system atrophy. We here tested the hypothesis that multiple system atrophy is associated with brain insulin resistance and showed increased expression of the key downstream messenger insulin receptor substrate-1 phosphorylated at serine residue 312 in neurons and oligodendrocytes in the putamen of patients with multiple system atrophy. Furthermore, the expression of insulin receptor substrate 1 (IRS-1) phosphorylated at serine residue 312 was more apparent in inclusion bearing oligodendrocytes in the putamen. By contrast, it was not different between both groups in the temporal cortex, a less vulnerable structure compared to the putamen. These findings suggest that insulin resistance may occur in multiple system atrophy in regions where the neurodegenerative process is most severe and point to a possible relation between α-synuclein aggregates and insulin resistance. We also observed insulin resistance in the striatum of transgenic multiple system atrophy mice and further demonstrate that the glucagon-like peptide-1 analogue exendin-4, a well-tolerated and Federal Drug Agency-approved antidiabetic drug, has positive effects on insulin resistance and monomeric α-synuclein load in the striatum, as well as survival of nigral dopamine neurons. Additionally, plasma levels of exosomal neural-derived IRS-1 phosphorylated at serine residue 307 (corresponding to serine residue 312 in humans) negatively correlated with survival of nigral dopamine neurons in multiple system atrophy mice treated with exendin-4. This finding suggests the potential for developing this peripheral biomarker candidate as an objective outcome measure of target engagement for clinical trials with glucagon-like peptide-1 analogues in multiple system atrophy. In conclusion, our observation of brain insulin resistance in multiple system atrophy patients and transgenic mice together with the beneficial effects of the glucagon-like peptide-1 agonist exendin-4 in transgenic mice paves the way for translating this innovative treatment into a clinical trial.

α-Synuclein-induced myelination deficit defines a novel interventional target for multiple system atrophy.

Multiple system atrophy (MSA) is a rare atypical parkinsonian disorder characterized by a rapidly progressing clinical course and at present without any efficient therapy. Neuropathologically, myelin loss and neurodegeneration are associated with α-synuclein accumulation in oligodendrocytes, but underlying pathomechanisms are poorly understood. Here, we analyzed the impact of oligodendrocytic α-synuclein on the formation of myelin sheaths to define a potential interventional target for MSA. Post-mortem analyses of MSA patients and controls were performed to quantify myelin and oligodendrocyte numbers. As pre-clinical models, we used transgenic MSA mice, a myelinating stem cell-derived oligodendrocyte-neuron co-culture, and primary oligodendrocytes to determine functional consequences of oligodendrocytic α-synuclein overexpression on myelination. We detected myelin loss accompanied by preserved or even increased numbers of oligodendrocytes in post-mortem MSA brains or transgenic mouse forebrains, respectively, indicating an oligodendrocytic dysfunction in myelin formation. Corroborating this observation, overexpression of α-synuclein in primary and stem cell-derived oligodendrocytes severely impaired myelin formation, defining a novel α-synuclein-linked pathomechanism in MSA. We used the pro-myelinating activity of the muscarinic acetylcholine receptor antagonist benztropine to analyze the reversibility of the myelination deficit. Transcriptome profiling of primary pre-myelinating oligodendrocytes demonstrated that benztropine readjusts myelination-related processes such as cholesterol and membrane biogenesis, being compromised by oligodendrocytic α-synuclein. Additionally, benztropine restored the α-synuclein-induced myelination deficit of stem cell-derived oligodendrocytes. Strikingly, benztropine also ameliorated the myelin deficit in transgenic MSA mice, resulting in a prevention of neuronal cell loss. In conclusion, this study defines the α-synuclein-induced myelination deficit as a novel and crucial pathomechanism in MSA. Importantly, the reversible nature of this oligodendrocytic dysfunction opens a novel avenue for an intervention in MSA.

Anle138b Partly Ameliorates Motor Deficits Despite Failure of Neuroprotection in a Model of Advanced Multiple System Atrophy.

The neurodegenerative disorder multiple system atrophy (MSA) is characterized by autonomic failure, cerebellar ataxia and parkinsonism in any combination associated with predominantly oligodendroglial α-synuclein (α-syn) aggregates (glial cytoplasmic inclusions = GCIs). To date, there is no effective disease modifying therapy. Previous experiments have shown that the aggregation inhibitor anle138b reduces neurodegeneration, as well as behavioral deficits in both transgenic and toxin mouse models of Parkinson's disease (PD). Here we analyzed whether anle138b improves motor skills and reduces neuronal loss, as well as oligodendroglial α-syn aggregation in the PLP-α-syn transgenic mouse challenged with the mitochondrial toxin 3-nitropropionic acid (3-NP) to model full-blown MSA. Following 1 month of treatment with anle138b, MSA mice showed signs of motor improvement affecting stride length, but not pole, grip strength, and beam test performance. Loss of dopaminergic nigral neurons and Purkinje cells was not attenuated and GCI density remained unchanged. These data suggest that the pathology in transgenic PLP-α-syn mice receiving 3-NP might be too advanced to detect significant effects of anle138b treatment on neuronal loss and intracytoplasmic α-syn inclusion bodies. However, the partial motor amelioration may indicate potential efficacy of anle138b treatment that may be mediated by its actions on α-syn oligomers or may reflect improvement of neuronal dysfunction in neural at risk populations. Further studies are required to address the efficacy of anle138b in transgenic α-syn models of early-stage MSA and in the absence of additional toxin application.

Involvement of Peripheral Nerves in the Transgenic PLP-α-Syn Model of Multiple System Atrophy: Extending the Phenotype.

Multiple system atrophy (MSA) is a fatal, rapidly progressive neurodegenerative disease with (oligodendro-)glial cytoplasmic α-synuclein (α-syn) inclusions (GCIs). Peripheral neuropathies have been reported in up to 40% of MSA patients, the cause remaining unclear. In a transgenic MSA mouse model featuring GCI-like inclusion pathology based on PLP-promoter driven overexpression of human α-syn in oligodendroglia motor and non-motor deficits are associated with MSA-like neurodegeneration. Since α-syn is also expressed in Schwann cells we aimed to investigate whether peripheral nerves are anatomically and functionally affected in the PLP-α-syn MSA mouse model.ResultsTo this end, heat/cold as well as mechanical sensitivity tests were performed. Furthermore, in vivo and ex vivo nerve conduction and the G-ratios of the sciatic nerve were analyzed, and thermosensitive ion channel mRNA expression in dorsal root ganglia (DRG) was assessed. The presence of human α-syn in Schwann cells was associated with subtle behavioral impairments. The G-ratio of the sciatic nerve, the conduction velocity of myelinated and unmyelinated primary afferents and the expression of thermosensitive ion channels in the sensory neurons, however, were similar to wildtype mice.ConclusionOur results suggest that the PNS appears to be affected by Schwann cell α-syn deposits in the PLP-α-syn MSA mouse model. However, there was no consistent evidence for functional PNS perturbations resulting from such α-syn aggregates suggesting a more central cause of the observed behavioral abnormalities. Nonetheless, our results do not exclude a causal role of α-syn in the pathogenesis of MSA associated peripheral neuropathy.

Failure of Neuroprotection Despite Microglial Suppression by Delayed-Start Myeloperoxidase Inhibition in a Model of Advanced Multiple System Atrophy: Clinical Implications.

Multiple system atrophy (MSA) is a rapidly progressive neurodegenerative disease. Post-mortem hallmarks of MSA neuropathology include oligodendroglial α-synuclein (αSYN) inclusions, striatonigral degeneration, olivopontocerebellar atrophy, and increased microglial activation that accompanies the wide spread neurodegeneration. Recently, we demonstrated upregulation of myeloperoxidase (MPO) in activated microglia and provided evidence for the role of microglial MPO in the mediation of MSA-like neurodegeneration (Stefanova et al. Neurotox Res 21:393–404, 2015). The aim of the current study was to assess the therapeutic potency of MPO inhibition (MPOi) in a model of advanced MSA. We replicated the advanced pathology of MSA by intoxicating transgenic PLP-α-synuclein transgenic mice with 3-nitropropionic acid (3NP). After onset of the full-blown pathology, MSA mice received either MPOi or vehicle over 3 weeks. Motor phenotype and neuropathology were analyzed to assess the therapeutic efficacy of MPOi compared to vehicle treatment in MSA mice. MPOi therapy initiated after the onset of severe MSA-like neuropathology in mice failed to attenuate motor impairments and neuronal loss within the striatum, substantia nigra pars compacta, inferior olives, pontine nuclei, and cerebellar cortex. However, we observed a significant reduction of microglial activation in degenerating brain areas. Further, nitrated αSYN accumulation was reduced in the striatonigral region. In summary, delayed-start MPOi treatment reduced microglial activation and levels of nitrated αSYN in a mouse model of advanced MSA. These effects failed to impact on motor impairments and neuronal loss in contrast to previously reported disease modifying efficacy of early-start therapy with MPOi in MSA.

Promoting oligodendrocyte progenitor cell maturation and remyelination as a novel therapeutical approach for multiple system atrophy

Alpha-synuclein (aSyn) aggregation within mature oligodendrocytes is the characteristic neuropathological feature of multiple system atrophy (MSA). In fact, dysfunction of oligodendrocytes is considered as a primary event in MSA pathogenesis leading to myelin loss and, ultimately, reduced axonal integrity and neuronal cell loss. Oligodendrocyte progenitor cells (OPCs) are widely distributed in the adult central nervous system and represent a potential endogenous source for replacement of such dysfunctional oligodendrocytes. The extent to which OPCs are affected in MSA or even contribute to MSA pathogenesis remains undefined. Thus, we analyzed OPCs post-mortem in MSA brains and in a pre-clinical MSA mouse model expressing aSyn under the myelin basic protein (MBP) promoter. Importantly, we detected elevated numbers of striatal OPCs in MSA and its model 1 . Observing aSyn-positive OPCs in MSA patients, we additionally established two independent in vitro models in order to explore the effect of intracellular aSyn on OPC maturation. Both stable aSyn expressing OPC-like central glia-4 (CG4) cells 1 and transiently aSyn expressing primary OPCs derived from neonatal rats 2 robustly showed a severely reduced maturation. Similarly, primary OPCs exhibit a delayed maturation upon uptake of recombinant aSyn 2 . Taken together, our findings indicate that OPC dysfunction is a pathological feature of MSA. In addition, promoting OPC differentiation may represent a novel and promising interventional strategy for therapeutic approaches in MSA.

β-III Tubulin Fragments Inhibit α-Synuclein Accumulation in Models of Multiple System Atrophy

Multiple system atrophy (MSA) is a neurodegenerative disease caused by α-synuclein aggregation in oligodendrocytes and neurons. Using a transgenic mouse model overexpressing human α-synuclein in oligodendrocytes, we previously demonstrated that oligodendrocytic α-synuclein inclusions induce neuronal α-synuclein accumulation and progressive neuronal degeneration. α-Synuclein binds to β-III tubulin, leading to the neuronal accumulation of insoluble α-synuclein in an MSA mouse model. The present study demonstrates that α-synuclein co-localizes with β-III tubulin in the brain tissue from patients with MSA and MSA model transgenic mice as well as neurons cultured from these mice. Accumulation of insoluble α-synuclein in MSA mouse neurons was blocked by the peptide fragment β-III tubulin (residues 235-282). We have determined the α-synuclein-binding domain of β-III tubulin and demonstrated that a short fragment containing this domain can suppress α-synuclein accumulation in the primary cultured cells. Administration of a short α-synuclein-binding fragment of β-III tubulin may be a novel therapeutic strategy for MSA.

α-Synuclein impairs oligodendrocyte progenitor maturation in multiple system atrophy

Multiple system atrophy (MSA), an atypical parkinsonian disorder, is characterized by α-synuclein (α-syn+) cytoplasmatic inclusions in mature oligodendrocytes. Oligodendrocyte progenitor cells (OPCs) represent a distinct cell population with the potential to replace dysfunctional oligodendrocytes. However, the role of OPCs in MSA and their potential to replace mature oligodendrocytes is still unclear. A postmortem analysis in MSA patients revealed α-syn within OPCs and an increased number of striatal OPCs. In an MSA mouse model, an age-dependent increase of dividing OPCs within the striatum and the cortex was detected. Despite of myelin loss, there was no reduction of mature oligodendrocytes in the corpus callosum or the striatum. Dissecting the underlying molecular mechanisms an oligodendroglial cell line expressing human α-syn revealed that α-syn delays OPC maturation by severely downregulating myelin-gene regulatory factor and myelin basic protein. Brain-derived neurotrophic factor was reduced in MSA models and its in vitro supplementation partially restored the phenotype. Taken together, efficacious induction of OPC maturation may open the window to restore glial and neuronal function in MSA.

Intact Olfaction in a Mouse Model of Multiple System Atrophy

BackgroundIncreasing evidence suggests that olfaction is largely preserved in multiple system atrophy while most patients with Parkinson's disease are hyposmic. Consistent with these observations, recent experimental studies demonstrated olfactory deficits in transgenic Parkinson's disease mouse models, but corresponding data are lacking for MSA models.MethodsOlfactory function and underlying neuropathological changes were investigated in a transgenic multiple system atrophy mouse model based on targeted oligodendroglial overexpression of α-synuclein as well as wild-type controls. The study was divided into (1) a pilot study investigating olfactory preference testing and (2) a long-term study characterizing changes in the olfactory bulb of aging transgenic multiple system atrophy mice.ResultsIn our pilot behavioral study, we observed no significant differences in investigation time in the olfactory preference test comparing transgenic with wild-type animals. These findings were accompanied by unaffected tyrosine hydroxylase-positive cell numbers in the olfactory bulb. Similarly, although a significant age-related increase in the amount of α-synuclein within the olfactory bulb was detected in the long-term study, progressive degeneration of the olfactory bulb could not be verified.ConclusionsOur experimental data show preserved olfaction in a transgenic multiple system atrophy mouse model despite α-synucleinopathy in the olfactory bulb. These findings are in line with the human disorder supporting the concept of a primary oligodendrogliopathy with variable neuronal involvement.

Bladder dysfunction in a transgenic mouse model of multiple system atrophy

Multiple system atrophy (MSA) is an adult-onset neurodegenerative disorder presenting with motor impairment and autonomic dysfunction. Urological function is altered in the majority of MSA patients, and urological symptoms often precede the motor syndrome. To date, bladder function and structure have never been investigated in MSA models. We aimed to test bladder function in a transgenic MSA mouse featuring oligodendroglial α-synucleinopathy and define its applicability as a preclinical model to study urological failure in MSA. Experiments were performed in proteolipid protein (PLP)-human α-synuclein (hαSyn) transgenic and control wild-type mice. Diuresis, urodynamics, and detrusor strip contractility were assessed to characterize the urological phenotype. Bladder morphology and neuropathology of the lumbosacral intermediolateral column and the pontine micturition center (PMC) were analyzed in young and aged mice. Urodynamic analysis revealed a less efficient and unstable bladder in MSA mice with increased voiding contraction amplitude, higher frequency of nonvoiding contractions, and increased postvoid residual volume. MSA mice bladder walls showed early detrusor hypertrophy and age-related urothelium hypertrophy. Transgenic hαSyn expression was detected in Schwann cells ensheathing the local nerve fibers in the lamina propria and muscularis of MSA bladders. Early loss of parasympathetic outflow neurons and delayed degeneration of the PMC accompanied the urological deficits in MSA mice. PLP-hαSyn mice recapitulate major urological symptoms of human MSA that may be linked to αSyn-related central and peripheral neuropathology and can be further used as a preclinical model to decipher pathomechanisms of MSA.