Abstract
BackgroundParkinson’s disease (PD) is a neurodegenerative disorder whose diagnosis is often challenging because symptoms may overlap with neurodegenerative parkinsonisms. PD is characterized by intraneuronal accumulation of abnormal α-synuclein in brainstem while neurodegenerative parkinsonisms might be associated with accumulation of either α-synuclein, as in the case of Multiple System Atrophy (MSA) or tau, as in the case of Corticobasal Degeneration (CBD) and Progressive Supranuclear Palsy (PSP), in other disease-specific brain regions. Definite diagnosis of all these diseases can be formulated only neuropathologically by detection and localization of α-synuclein or tau aggregates in the brain. Compelling evidence suggests that trace-amount of these proteins can appear in peripheral tissues, including receptor neurons of the olfactory mucosa (OM).MethodsWe have set and standardized the experimental conditions to extend the ultrasensitive Real Time Quaking Induced Conversion (RT-QuIC) assay for OM analysis. In particular, by using human recombinant α-synuclein as substrate of reaction, we have assessed the ability of OM collected from patients with clinical diagnoses of PD and MSA to induce α-synuclein aggregation, and compared their seeding ability to that of OM samples collected from patients with clinical diagnoses of CBD and PSP.ResultsOur results showed that a significant percentage of MSA and PD samples induced α-synuclein aggregation with high efficiency, but also few samples of patients with the clinical diagnosis of CBD and PSP caused the same effect. Notably, the final RT-QuIC aggregates obtained from MSA and PD samples owned peculiar biochemical and morphological features potentially enabling their discrimination.ConclusionsOur study provide the proof-of-concept that olfactory mucosa samples collected from patients with PD and MSA possess important seeding activities for α-synuclein. Additional studies are required for (i) estimating sensitivity and specificity of the technique and for (ii) evaluating its application for the diagnosis of PD and neurodegenerative parkinsonisms. RT-QuIC analyses of OM and cerebrospinal fluid (CSF) can be combined with the aim of increasing the overall diagnostic accuracy of these diseases, especially in the early stages.
Highlights
Parkinson’s disease (PD) is a neurodegenerative disorder whose diagnosis is often challenging because symptoms may overlap with neurodegenerative parkinsonisms
Brain homogenates of patients with synucleinopathies efficiently seeded Real Time Quaking Induced Conversion assay (RT-QuIC) reaction Considering the high level of RT-QuIC sensitivity in detecting extremely low amounts of artificial seeds, we decided to verify its ability to detect pathological α-synuclein aggregates present in brain samples of patients with PD and Multiple System Atrophy (MSA)
The kinetics was accelerated by the addition of PD, MSA, Progressive Supranuclear Palsy (PSP), Corticobasal Degeneration (CBD), FTDP-17 and NDP brain homogenates, the fluorescence intensities were significantly higher in reactions seeded with PD or MSA compared to the others
Summary
Parkinson’s disease (PD) is a neurodegenerative disorder whose diagnosis is often challenging because symptoms may overlap with neurodegenerative parkinsonisms. These structural differences might dictate specific tropism of these proteins for defined neuroanatomical regions or even cell types Both α-synuclein and tau are considered disease-specific biomarkers and definite diagnosis of PD and neurodegenerative parkinsonisms relies on their identification and anatomical distribution in brains collected at autopsy. Compelling evidence suggests that trace amount of these abnormally folded proteins are present in cerebrospinal fluid (CSF) and peripheral tissues of diseased patients Their concentration is well below the limits of detection of the conventional diagnostic techniques. To the best of our knowledge, there are no reports that have evaluated the ability of RT-QuIC to detect trace amount of abnormally folded proteins in OM samples collected from patients with a clinical diagnosis of PD or neurodegenerative parkinsonisms. In contrast to the widely used CSF, OM samples can be periodically collected with a non-invasive procedure, representing optimal tissues for RT-QuIC analysis
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