ObjectiveEvidence of abnormal α‐synuclein (α‐Syn) deposition in the brain is required for definitive diagnosis of synucleinopathies, which remains challenging. The seed amplification assay (SAA) is an innovative technique that can detect the seeding activity of misfolded α‐Syn, enabling the amplification and detection of minute quantities of pathogenic α‐Syn aggregates. This study aimed to evaluate oral mucosa α‐Syn SAA as possible diagnostic and prodromal biomarkers for synucleinopathies.MethodsA total of 107 Parkinson's disease (PD) patients, 99 multiple system atrophy (MSA) patients, 33 patients with isolated rapid eye movement sleep behavior disorder (iRBD) and 103 healthy controls (HC) were included. The SAA was applied to detect the seeding activity of α‐Syn from oral mucosa. A combination of morphological, biochemical, and biophysical methods was also used to analyze the fibrils generated from the oral mucosa α‐Syn SAA.ResultsStructured illumination microscopy images revealed the increased α‐Syn species in oral mucosa of PD, MSA, and iRBD patients than in HCs. Oral mucosa α‐Syn SAA distinguished patients with PD from HC with 67.3% sensitivity and 90.3% specificity. Oral mucosa was α‐Syn SAA positive in 53.5% MSA patients and 63.6% iRBD patients. Furthermore, the α‐Syn fibrils generated from MSA demonstrated greater resistance to proteinase K digestion and exhibited stronger cytotoxicity compared to those from PD patients.ConclusionOral mucosa α‐Syn seeding activity may serve as novel non‐invasive diagnostic and prodromal biomarkers for synucleinopathies. The α‐Syn aggregates amplified from the oral mucosa of PD and MSA exhibited distinct biochemical and biophysical properties. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

中文翻译：

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通过种子扩增测定检测突触核蛋白病和孤立性快速眼动睡眠行为障碍口腔粘膜中的 α-突触核蛋白

目的 明确诊断突触核蛋白病需要大脑中异常 α-突触核蛋白 (α-Syn) 沉积的证据，但这仍然具有挑战性。种子扩增测定 (SAA) 是一种创新技术，可以检测错误折叠 α-Syn 的种子活性，从而能够扩增和检测微量致病性 α-Syn 聚集体。本研究旨在评估口腔粘膜 α-Syn SAA 作为突触核蛋白病的可能诊断和前驱生物标志物。方法总共 107 名帕金森病 (PD) 患者、99 名多系统萎缩 (MSA) 患者、33 名孤立性快速动眼睡眠行为障碍患者(iRBD) 和 103 名健康对照 (HC) 被纳入。应用SAA检测口腔粘膜中α-Syn的播种活性。还结合形态学、生化和生物物理方法分析了口腔粘膜 α-Syn SAA 生成的原纤维。结果结构照明显微镜图像显示，与 PD、MSA 和 iRBD 患者相比，口腔粘膜中 α-Syn 种类增多。在 HC 中。口腔粘膜 α-Syn SAA 区分 PD 和 HC 患者的敏感性为 67.3%，特异性为 90.3%。 53.5% MSA 患者和 63.6% iRBD 患者口腔粘膜 α-Syn SAA 阳性。此外，与PD患者相比，MSA产生的α-Syn原纤维对蛋白酶K消化具有更大的抵抗力，并且表现出更强的细胞毒性。结论口腔粘膜α-Syn播种活性可以作为突触核蛋白病的新型非侵入性诊断和前驱生物标志物。从 PD 和 MSA 口腔粘膜扩增的 α-Syn 聚集体表现出独特的生化和生物物理特性。 © 2024 作者。运动障碍由 Wiley periodicals LLC 代表国际帕金森和运动障碍协会出版。