[Mechanism of neuronal degeneration of multiple system atrophy]

Abstract

Multiple system atrophy (MSA) is a sporadic neurodegenerative disorder that encompasses olivopontocerebellar atrophy (OPCA), striatonigral degeneration (SND) and Shy-Drager syndrome (SDS). The histopathological hallmarks are alpha-synuclein (AS) positive glial cytoplasmic inclusions (GCIs) in oligodendroglias. AS aggregation is also found in glial nuclear inclusions (GNIs), neuronal cytoplasmic inclusions (NCIs), neuronal nuclear inclusions (NNIs) and dystrophic neurites. Reviewing the pathological features in 102 MSA cases revealed that the, OPCA-type was relatively more frequent and SND-type was less frequent in Japanese MSA cases. The frequency of the SND-type is relatively high in Western countries. This different in the dominant type suggests that the phenotypic patterns of MSA may vary with the race. In early stages of MSA, in addition to GCIs, NNIs, NCIs, and diffuse homogenous stain of AS in neuronal nuclei and cytoplasm were observed in various vulnerable lesions including the pontine nuclei, putamen, substantia nigra, locus ceruleus, inferior olivary nucleus, intermediolateral column of the thoracic cord, lower motor neurons, and cortical pyramidal neurons. These findings indicated that the primary nonfibrillar and fibrillar AS aggregation also occurred in neurons. Therefore, both the direct involvement of neurons themselves and the oligodendroglia-myelin-axon mechanism may synergistically accelerate the degenerative process of MSA.