Oral Mucosa Derived α−Synuclein as a Potential Diagnostic Biomarker for Parkinson′s Disease

Abstract

BackgroundPathological α-synuclein (α-Syn) is not only exclusive to the central nervous system (CNS) in Parkinson’s disease (PD), but also extended to biofluids and peripheral tissues including oral cavity. Both oral mucosa and nervous system are derived from ectodermal tissue, and potentially share common disease-specific characteristics. Oral mucosal exfoliative cytology is a non-invasive technique, which is an easily acceptable for patients and ordinary people. The purpose of this study was to determine the abnormal accumulation of α-Syn in oral mucosa of PD patients and to learn the diagnostic utility of oral mucosa α-Syn for PD.MethodsThe oral mucosa samples were obtained from 57 patients with PD and 51 age-matched controls by cytological brush. Immunofluorescence analysis was used to investigate the presence and subcellular localization of α-Syn, phosphorylated α-Syn at Ser129 (pS129) and oligomeric α-Syn in the oral mucosa cells of PD patients and controls. Images taken as Z-stacks were analyzed for 3D reconstruction to visualize the α-Syn intracellular localization. Then, the concentrations of α-Syn, pS129, and oligomeric α-Syn in oral mucosa samples were measured using electrochemiluminescence assays.ResultsImmunofluorescence images revealed the increased α-Syn, pS129, and oligomeric α-Syn levels in oral mucosa cells of PD patients than age-matched controls. The intracellular distributions of α-Syn species were determine by Z-stack images with 3D reconstruction, and α-Syn was detected in both the nucleus and cytoplasm. However, pS129 was mainly located in the cytoplasm, and oligomeric α-Syn was highly expressed in the nucleus and perinuclear cytoplasm. The concentrations of three α-Syn species were significantly increased in the oral mucosa cell samples of PD patients than controls (α-Syn, p = 0.001; pS129, p = 0.002; oligomeric α-Syn, p = 0.013). In PD patients, the oral mucosa α-Syn and oligomeric α-Syn levels were significantly correlated with Hoehn-Yahr scales (α-Syn, r = 0.495, p = 0.001; oligomeric α-Syn, r = 0.324, p = 0.03). The area under curve (AUC) of ROC analysis using an integrative model including α-Syn, pS129, and oligomeric α-Syn for PD diagnosis was 0.749, with 66.7% sensitivity and 72.5% specificity.ConclusionThis study for the first time demonstrated increased expressions of α-Syn, pS129, and oligomeric α-Syn in oral mucosa cells from PD patients, which serve as useful and non-invasive PD diagnostic biomarkers.

Defining the Riddle in Order to Solve It: There Is More Than One “Parkinson's Disease”

“…However, recent evidence indicates that aSyn aggregates can be observed in different peripheral tissues already during diagnosis, challenging the concept of spreading as initially hypothesized by Braak for PD. 68,69 The distinction between DLB and PDD is based on clinical findings: in PDD the onset of parkinsonism should precede dementia by at least 1 year, and in DLB cognitive impairment manifests before, during, or within 1 year of the onset of parkinsonism, suggesting that the Braak stages for LBP progression are not valid for DLB, where severe LBP may be initially seen in limbic and neocortical areas. 70 In fact, the Braak stages were proposed based on the study of PD and PDD patients, not DLB.…”

Alpha-Synuclein species in oral mucosa as potential biomarkers for multiple system atrophy

“…The ECL assays used for detecting α-Syn, pS129, and α-Syn aggregates of oral mucosa were established previously ( Zheng et al, 2022 ) and have been applied to detect α-Syn, pS129, and α-Syn aggregates in erythrocytes ( Tian et al, 2019 ; Yu et al, 2022 ). Previous studies have validated the high sensitivity and reproducibility of ECL detection of disease-associated proteins on CSF samples ( Kruse et al, 2017 ).…”

“…The ECL assay of oral mucosal cells was made as described previously ( Zheng et al, 2022 ), with minor modifications. The Meso Scale Discovery (MSD, Rockville, MD, United States) U-Plex plates were used for the quantification of oral mucosa-derived α-Syn, pS129, and α-Syn aggregates.…”

“…A non-invasive sampling assay with high diagnostic efficiency is in urgent need for the diagnosis of MSA. We recently reported the increased expressions of α-Syn, phosphorylated α-Synuclein at Ser129 (pS129), and α-Syn aggregates in oral mucosal cells of PD, which serve as potential non-invasive biomarkers ( Zheng et al, 2022 ). These results suggested that oral mucosal cells may be the ideal source of biomarker for synucleinopathies including MSA.…”

Revisiting Alpha-Synuclein Pathways to Inflammation

“…The apparent specific oral microbiota profiling in PD raised other questions of major importance regarding the pathophysiological features of this movement disorder. Particularly, Zheng et al [ 112 ] collected oral mucosa samples using a cytological brush from people with PD and age-matched controls. Immunofluorescence analysis revealed increased α-Syn, pS129, and oligomeric α-Syn levels in oral mucosa cells of PD patients.…”