Efficient RT-QuIC seeding activity for α-synuclein in olfactory mucosa samples of patients with Parkinson’s disease and multiple system atrophy

Abstract

Background Parkinson’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). Methods We 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. Results Our 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. Conclusions Our 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. Electronic supplementary material The online version of this article (10.1186/s40035-019-0164-x) contains supplementary material, which is available to authorized users.

Effect of the micro-environment on α-synuclein conversion and implication in seeded conversion assays

“…Finally, De Luca et al [112] performed a cross-sectional observational study, carried out by seeding the RT-QuIC reaction with brain material derived from cases affected by PSP, frontotemporal dementia (FTD) and corticobasal degeneration (CBD), PD and MSA. Serial steps of high speed centrifugation were conducted to enrich the seeding-competent α-synuclein species and diluted to a working concentration of 10 − 3 .…”

PMCA Applications for Prion Detection in Peripheral Tissues of Patients with Variant Creutzfeldt-Jakob Disease

“…Therefore, PMCA and RT-QuIC might be exploited for detecting peripheral disease-specific biomarkers associated with these more frequent disorders. In this regard, we and others have already shown that traces of aberrantly folded α-synuclein, amyloid-β, and tau can be detected in the cerebrospinal fluid and olfactory mucosa of patients with different neurodegenerative diseases [110][111][112][113][114][115][116][117][118][119]. However, these studies are in their very early phases of development and additional studies are required before these amplification technologies can be used as robust and reliable diagnostic tools.…”

Multiplicity of α-Synuclein Aggregated Species and Their Possible Roles in Disease

“…Along the most recent improvements regarding identifying and studying the variety of amyloid polymorphs in synucleinopathies, protein misfolding cyclic amplification (PMCA) [133] together with real-time quaking-induced conversion (RT-QuIC) [134] are providing highly valuable insights into the characteristics of patient-derived αS aggregated species as well as helping to bring about new diagnostic tools in the field of neurodegeneration [135]. Both techniques allow replicating and amplifying the structure of abnormal αS by repeatedly fragmenting the parent aggregates and using them as templates for seeding reactions with recombinant monomeric αS in the presence of the thioflavin T probe.…”