Conclusions
Our results indicate that human wild-type alpha-synuclein supports the prion-like spreading of alpha-synuclein pathology in the absence of endogenously expressed mouse alpha-synuclein in vivo.
Results
Here we show that brain extracts from two patients with MSA and two patients with probable incidental Lewy body disease (iLBD) but not phosphate-buffered saline induce prion-like spreading of pathological alpha-synuclein after intrastriatal injection into mice expressing human wild-type alpha-synuclein. Mice were sacrificed at 3, 6, and 9 months post injection and analyzed neuropathologically and biochemically. Mice injected with brain extracts from patients with MSA or probable iLBD both accumulated intraneuronal inclusion bodies, which stained positive for phosphorylated alpha-synuclein and appeared predominantly within the injected brain hemisphere after 6 months. After 9 months these intraneuronal inclusion bodies had spread to the contralateral hemisphere and more rostral and caudal areas. Biochemical analysis showed that brains of mice injected with brain extracts from patients with MSA and probable iLBD contained hyperphosphorylated alpha-synuclein that also seeded aggregation of recombinant human wild-type alpha-synuclein in a Thioflavin T binding assay. Conclusions: Our results indicate that human wild-type alpha-synuclein supports the prion-like spreading of alpha-synuclein pathology in the absence of endogenously expressed mouse alpha-synuclein in vivo.