Cellular pathology in multiple system atrophy

Multiple system atrophy (MSA) is a sporadic, adult‐onset neurodegenerative disease, which is characterized by striatonigral degeneration, olivopontocerebellar atrophy, and preganglionic autonomic lesions in any combination. The histological hallmark is the presence of argyrophilic fibrillary inclusions in the oligodendrocytes, referred to as glial cytoplasmic inclusions (GCIs). Fibrillary inclusions are also found in the neuronal somata, axons, and nucleus. Neuronal cytoplasmic inclusions are frequently found in the pontine and inferior olivary nuclei. Since the discovery of α‐synuclein as a major component of glial and neuronal inclusions in MSA, two neurodegenerative processes have been considered in this disease: one is due to the widespread occurrence of GCIs associated with oligodendroglia–myelin degeneration (oligodendrogliopathy) in the central nervous system, and the other is due to the filamentous aggregation of α‐synuclein in the neurons in several brain regions. These two degenerative processes might synergistically cause neuronal depletion in MSA.     

Review: Multiple system atrophy: emerging targets for interventional therapies

Multiple system atrophy (MSA) is a fatal orphan neurodegenerative disorder that manifests with rapidly progressive autonomic and motor dysfunction. The disease is characterized by the accumulation of α‐synuclein fibrils in oligodendrocytes that form glial cytoplasmic inclusions, a neuropathological hallmark and central player in the pathogenesis of MSA. Here, we summarize the current knowledge on the etiopathogenesis and neuropathology of MSA. We discuss the role of α‐synuclein pathology, microglial activation, oligodendroglial dysfunction and putative cell death mechanisms as candidate therapeutic targets in MSA.     

Microglial activation mediates neurodegeneration related to oligodendroglial alpha-synucleinopathy: implications for multiple system atrophy.

The role of microglial activation in multiple system atrophy (MSA) was investigated in a transgenic mouse model featuring oligodendroglial alpha-synuclein inclusions and loss of midbrain dopaminergic neurons by means of histopathology and morphometric analysis. Our findings demonstrate early progressive microglial activation in substantia nigra pars compacta (SNc) associated with increased expression of iNOS and correlating with dopaminergic neuronal loss. Suppression of microglial activation by early long-term minocycline treatment protected dopaminergic SNc neurons. The results suggest that oligodendroglial overexpression of alpha-synuclein may induce neuroinflammation related to nitrosive stress which is likely to contribute to neurodegeneration in MSA. Further, we detected increased toll-like receptor 4 immunoreactivity in both transgenic mice and MSA brains indicating a possible signaling pathway in MSA which needs to be further studied as a candidate target for neuroprotective interventions.     

Tau‐positive glial cytoplasmic granules in multiple system atrophy

Multiple system atrophy (MSA) is a sporadic neurodegenerative disease that is pathologically characterized by the filamentous aggregation of α‐synuclein. We report a case of MSA showing unusual neuropathological findings and review six autopsied cases of MSA. The patient progressively developed parkinsonism and ataxia for the 9 years prior to her death at the age of 72 years. Neuropathological examinations revealed neuronal loss restricted to the olivopontocerebellar and striatonigral region, which was more severe in the putamen. Staining with anti‐α‐synuclein antibody demonstrated widespread occurrence of glial cytoplasmic inclusions, which mainly accumulated in oligodendroglial cells and corresponded closely to the degree of disease progression. In addition, tau‐positive granules were detected within the glial cytoplasm in the neurodegenerative region, which was especially prominent in the putamen and internal capsule. Tau accumulation was also clearly recognized by staining with specific antibodies against three‐repeat or four‐repeat tau. The glia that demonstrated deposition of tau‐positive granules were distinguished from α‐synuclein‐positive oligodendroglia by double immunohistochemical staining. These characteristic glial accumulations of tau were also present in all six cases of MSA. These results indicate that tau‐positive granules in glia are common findings in MSA and that tau aggregation might be another pathway to neurodegeneration in MSA.     

Definite familial multiple system atrophy with unknown genetics

Multiple system atrophy (MSA) is an oligodendrogliopathy of presumably sporadic origin, characterized by prominent α‐synuclein inclusions with neuronal multisystem degeneration, although a few Mendelian pedigrees have been reported. Here we report two familial cases of MSA of unknown genetic background. One patient was diagnosed as a possible MSA‐C (cerebellar dysfuntion) case, and the other as clinically possible MSA‐P (parkinsonism), which turned out to be definite MSA, based on a detailed autopsy. The neuropathology showed extensive deposition of α‐synuclein in the glia as well as in the neurons located in the cerebral cortices and hippocampal systems, although neither multiplication of the SNCA gene or mutations in COQ2 gene were identified in the family concerned.     

Neuropathological features of multiple system atrophy with cognitive impairment

Cognitive impairment (CI) is an exclusion criterion for the diagnosis of multiple system atrophy (MSA), according to the second consensus statement. This view was recently challenged by patients with pathologically confirmed MSA who were reported to have dementia. With an aim to investigate the pathological substrate of CI in MSA, quantitative assessment of the glial and neuronal cytoplasmic inclusions and semiquantitative assessment of neuronal loss in the cortical and limbic regions was performed. No differences in the severity of these MSA‐related pathological findings were identified between nine MSA cases with CI and nine MSA cases with normal cognition. Alzheimer's‐related pathological changes, cerebral amyloid angiopathy, and cerebrovascular disease did not differ between the two MSA groups. MSA‐specific α‐synuclein and secondary pathological conditions were not more severe in MSA cases with CI, suggesting that although CI may be intrinsic to the MSA disease process, further investigation into the pathological basis of cognitive impairment in MSA is warranted. © 2014 International Parkinson and Movement Disorder Society     

Breathing variability and brainstem serotonergic loss in a genetic model of multiple system atrophy

Breathing disorders like sleep apnea, stridor, and dysrythmic breathing are frequent in patients with multiple system atrophy (MSA). These observations have been related to neurodegeneration in several pontomedullary respiratory nuclei and may explain the occurrence of sudden death. In this study, we sought to determine whether these functional and neuropathological characteristics could be replicated in a transgenic model of MSA. Mice expressing human wild‐type α‐synuclein under the control of the proteolipid promoter (PLP‐αSYN) were compared with age‐matched controls. Using whole‐body, unrestrained plethysmography, the following breathing parameters were measured: inspiratory and expiratory times, tidal volume, expiratory volume, peak inspiratory and expiratory flows, and respiratory frequency. For each category, the mean, coefficient of variation, and irregularity score were analyzed. Brains were then processed for stereological cell counts of pontomedullary respiratory nuclei. A significant increase in the coefficient of variation and irregularity score was observed for inspiratory time, tidal volume, and expiratory volume in PLP‐αSYN mice (P < 0.05). Glial cytoplasmic inclusions were found in the medullary raphe of PLP‐αSYN mice, together with a loss of serotonergic immunoreactivity in the raphe obscurus (P < 0.001) and pallidus (P < 0.01). There was a negative correlation between α‐synuclein burden and raphe pallidus cell counts (P < 0.05). There was no significant neuronal loss in the pre‐Botzinger complex. The PLP‐αSYN mouse model replicates the breathing variability and part of the neuronal depletion in pontomedullary respiratory nuclei observed in patients with MSA. Our findings support the use of this model for future candidate drugs in the breathing disorders observed in MSA. © 2014 International Parkinson and Movement Disorder Society     

Olfactory bulb in multiple system atrophy.

Olfactory dysfunction is a characteristic clinical sign in Parkinson's disease (PD); it is also present in multiple system atrophy (MSA). The pathological basis of hyposmia or anosmia in PD is well known: the olfactory bulb (OB) contains numerous Lewy bodies and severe neuronal loss is present in the anterior olfactory nucleus (AON). We established that glial cytoplasmic inclusions (GCIs) are present in all the OBs from MSA cases. Their presence in the OB is diagnostic for MSA. Additionally, neuronal loss is present in the AON in MSA. These pathological changes might be responsible for the olfactory dysfunction seen in MSA.     

High dose levodopa therapy is not toxic in multiple system atrophy: experimental evidence.

Levodopa is generally regarded the first choice therapy for parkinsonism associated with multiple system atrophy (MSA-P). However, MSA-P patients often show a poor or unsustained levodopa response which inflicts high dose therapy. This is generally attributed to progressive striatal degeneration with loss of dopamine receptors. Experimental evidence suggests that dopaminergic stimulation may accelerate the striatal disease process in MSA, possibly by pro-oxidative mechanisms. Intact nigrostriatal dopamine release augments striatal lesion size in the unilateral nigral and striatal double lesion rat model of MSA-P. Further, neuronal vulnerability to exogenous oxidative stress is increased in a transgenic MSA mouse model with oligodendroglial alpha-synuclein inclusions. The aim of the present study was to analyze whether high dose levodopa delivery in the transgenic MSA model is associated with neurotoxicity exacerbated by the presence of oligodendroglial alpha-synuclein inclusion pathology. Control and transgenic MSA mice underwent pulsatile treatment with either vehicle, low or high dose levodopa for a period of 1 month. Behavioral and neuropathological indices failed to show evidence for neurotoxic effects of high-dose levodopa in this alpha-synuclein transgenic MSA model. These findings support the idea that high dose levodopa therapy in MSA is not detrimental to the underlying neuropathological process.     

Somatic sprouts of the Purkinje cells in a patient with multiple system atrophy

We describe the post mortem case of a 71‐year‐old Japanese woman diagnosed as having multiple system atrophy (MSA), showing somatic sprouting formation of Purkinje cells. The patient had suffered from frequent falling episodes and clumsiness of the left hand since the age of 67 years. Orthostatic hypotension and parkinsonism subsequently emerged. Typical neuropathological features of MSA, including degeneration of the striatum, pontine base and cerebellum with abundance of phosphorylated α‐synuclein‐positive neuronal and glial cytoplasmic and nuclear inclusions in the brain, were observed. In addition to gliosis of the cerebellar white matter and notable loss of Purkinje cells, several Purkinje cells showed somatic sprouting. Somatic sprouting of Purkinje cells has been demonstrated in several specific conditions, such as developing brains and several neurodegenerative disorders, including Menkes kinky hair disease, familial spinocerebellar ataxia, acute encephalopathy linked to familial hemiplegic migraine, and Huntington’s disease; however, no MSA cases have been reported with sprouting from the soma of Purkinje cells. Axonal damage caused by oligodendroglial dysfunction could be crucial in the development of Purkinje cell loss in MSA. Moreover, no apparent α‐synuclein accumulation has been described in the Purkinje cells of MSA. We propose that MSA is another degenerative disorder associated with somatic sprouts of Purkinje cells.     

Glial cytoplasmic inclusions and tissue injury in multiple system atrophy: A quantitative study in white matter (olivopontocerebellar system) and gray matter (nigrostriatal system)

Glial cytoplasmic inclusions (GCIs) and microglia were quantified in 12 cases of multiple system atrophy (MSA) with special reference to their association with histologically defined lesion severity. The targets of the analysis were white matter (cerebellum, pontine base) and gray matter (putamen, substantia nigra). First, the lesion severity was defined: for white matter, the degree of demyelination and tissue rarefaction were semi‐quantified on Klüver‐Barrera (KB) sections as grade I (mildly injured), II (moderately injured), and III (severely injured); for gray matter, neurons and astrocytes were counted on KB and glial fibrillary acidic protein‐immunostained sections, respectively. Next, the GCI burden was quantified on sections immunostained for α‐synuclein, phosphorylated α‐synuclein, and ubiquitin and the microglial burden was quantified on sections immunostained for HLA‐DR. In white matter, the GCI and microglial burdens were the greatest when the tissue injury was mild and/or moderate (grade I and/or grade II), and they became less prominent when the tissue injury became more severe (grade III). In gray matter, in contrast, the GCI and microglial burdens failed to show significant correlations with the lesion severity. Our result suggests that the amount of GCIs as well as that of microglia is reduced when the tissue injury becomes severe in vulnerable white matter areas, but not in vulnerable gray matter areas, of MSA. It also suggests that there seems to be a difference between gray matter and white matter in the way GCIs and microglia participate in the degenerative process of MSA.     

Accumulation of phosphorylated α‐synuclein in subpial and periventricular astrocytes in multiple system atrophy of long duration

The histological hallmark of multiple system atrophy (MSA) is accumulation of phosphorylated α‐synuclein in oligodendrocytes. However, it is uncertain whether phosphorylated α‐synuclein accumulates in astrocytes of MSA patients. We immunohistochemically examined the frontal and temporal lobes, basal ganglia, cerebellum, brainstem and spinal cord of patients with MSA (n = 15) and Lewy body disease (n = 20), and also in control subjects (n = 20). Accumulation of abnormally phosphorylated and aggregated α‐synuclein was found in subpial and periventricular astrocytes in six of the 15 patients with MSA (40%). The structures were confined to the subpial surface of the ventro‐lateral part of the spinal cord and brainstem, as well as the subependymal region of the lateral ventricles. They were not visualized by Gallyas‐Braak staining, and were immunonegative for ubiquitin and p62. Immunoelectron microscopy revealed that the phosphorylated α‐synuclein‐immunoreactive structures in astrocytes were non‐fibrillar and associated with granular and vesicular structures. The extent of phosphorylated α‐synuclein‐immunoreactive astrocytes was correlated with disease duration. No such structures were found in Lewy body disease or controls. Accumulation of phosphorylated α‐synuclein can occur in subpial and periventricular astrocytes in patients with MSA, especially in those with a long disease duration.     

An autopsy case of preclinical multiple system atrophy (MSA‐C)

Multiple system atrophy (MSA) is divided into two clinical subtypes: MSA with predominant parkinsonian features (MSA‐P) and MSA with predominant cerebellar dysfunction (MSA‐C). We report a 71‐year‐old Japanese man without clinical signs of MSA, in whom post mortem examination revealed only slight gliosis in the pontine base and widespread occurrence of glial cytoplasmic inclusions in the central nervous system, with the greatest abundance in the pontine base and cerebellar white matter. Neuronal cytoplasmic inclusions (NCIs) and neuronal nuclear inclusions (NNIs) were almost restricted to the pontine and inferior olivary nuclei. It was noteworthy that most NCIs were located in the perinuclear area, and the majority of NNIs were observed adjacent to the inner surface of the nuclear membrane. To our knowledge, only four autopsy cases of preclinical MSA have been reported previously, in which neuronal loss was almost entirely restricted to the substantia nigra and/or putamen. Therefore, the present autopsy case of preclinical MSA‐C is considered to be the first of its kind to have been reported. The histopathological features observed in preclinical MSA may represent the early pattern of MSA pathology.     

Bilateral striopallidodentate calcification (Fahr's syndrome) and multiple system atrophy in a patient with longstanding hypoparathyroidism

Recently, a family with idiopathic brain calcification was reported, in which one family member was diagnosed with multiple system atrophy (MSA) at autopsy. We report here a case showing similar neuropathological features in a patient with longstanding hypoparathyroidism. Our female patient had a history of hypoparathyroidism with hypocalcaemia and tetany since the age of 9 years. In her 50s she developed dementia and parkinsonism. She died of myocardial infarction aged 65 years. Neuropathology showed severe brain calcifications of the Fahr type in the basal ganglia, thalami, cerebral and cerebellar white matter and dentate nuclei. Additionally, there was prominent alpha‐synucleinopathy of the multiple system atrophy type (MSA). The patient has a healthy identical twin and there is no family history of hypoparathyroidism or neurological disease. Data on alpha‐synuclein accumulation in various cases of Fahr's syndrome are needed to establish the correlation between alpha‐synucleinopathy and bilateral striopallidodentate calcification.     

The neuropathology, pathophysiology and genetics of multiple system atrophy

Multiple system atrophy (MSA) is an unrelenting, sporadic, adult-onset, neurodegenerative disease of unknown aetiology. Its clinically progressive course is characterized by a variable combination of parkinsonism, cerebellar ataxia and/or autonomic dysfunction. Neuropathological examination often reveals gross abnormalities of the striatonigral and/or olivopontocerebellar systems, which upon microscopic examination are associated with severe neuronal loss, gliosis, myelin pallor and axonal degeneration. MSA is a member of a diverse group of neurodegenerative disorders termed α-synucleinopathies, due to the presence of abnormal α-synuclein positive cytoplasmic inclusions in oligodendrocytes, termed glial cytoplasmic inclusions. These are the hallmark neuropathological lesion of MSA and are thought to play a central role in the pathogenesis of the disease. In this review, neuropathological features of MSA are described in detail, along with recent advances in the pathophysiology and genetics of the disease. Our current knowledge of the expression and accumulation of α-synuclein, and efforts to model the disease in vitro and in vivo, are emphasized in this paper and have helped formulate a working hypothesis for the pathogenesis of MSA.     

Extensive distribution of glial cytoplasmic inclusions in an autopsied case of multiple system atrophy with a prolonged 18‐year clinical course

We describe herein an autopsied case of multiple system atrophy (MSA) with prolonged clinical course of 18 years, and evaluate the extent of neurodegeneration and glial cytoplasmic inclusions (GCIs) in the entire brain of this rare case. A 64‐year‐old woman presented with typical neurological symptoms and imaging features of MSA. Thereafter, she became bedridden, and breathing was assisted through a tracheostomy for 12 years. She died at the age of 82 after 18 years from the initial symptom. Post mortem examination revealed severe neurodegeneration in the inferior olive, pontine nuclei, substantia nigra, locus ceruleus, putamen and cerebellum. Notably, phosphorylated α‐synuclein (p‐α‐syn)‐positive GCIs were found in these areas, but their number was very low. In contrast, the density of GCIs was much higher in such regions as the tectum/tegmentum of the brainstem, pyramidal tracts, neocortices and limbic system, which usually contain a small number of GCIs. Another constituent of GCIs, ubiquitin (Ub) and Ub‐associated autophagy substrate p62, were also positive in some GCIs, and distribution of Ub/p62 immunoreactivity was proportionate to that of p‐α‐syn+ GCIs despite the very long duration of the disease. Furthermore, this case had complicated hypoxic encephalopathy, but p‐α‐syn+ GCIs were also found in the damaged white matter, indicating the contribution of α‐syncleinopathy as well as hypoxic effect to the secondary myelin and axonal loss in the white matter. Together, this rare case suggests the contribution of the disease duration to the prevalence of GCIs, and the possible involvement of the limbic system in extensive‐stage disease.     

Increase of the plasma α‐synuclein levels in patients with multiple system atrophy

Multiple system atrophy, a sporadic neurodegenerative disease, is characterized by the presence of high numbers of glial cytoplasmic inclusions mainly formed by α‐synuclein protein, which is encoded by the SNCA gene. To date, however, few studies have investigated the plasma α‐synuclein levels in patients with multiple system atrophy. We studied plasma α‐synuclein concentrations by using an enzyme‐linked immunosorbent assay in 74 patients with multiple system atrophy and 90 healthy controls. The plasma α‐synuclein levels were significantly elevated in patients who had multiple system atrophy compared with the control group (P = 0.000). In a subgroup of 48 patients who had probable multiple system atrophy, there was a weakly negative correlation between plasma α‐synuclein levels and subscores on Unified Multiple System Atrophy Rating Scale item VI (r_s = ?0.307; P = 0.034). Plasma α‐synuclein levels were elevated in patients with multiple system atrophy, and these levels may be decreased with the development of disease. © 2013 International Parkinson and Movement Disorder Society.