Neurodegenerative diseases (NDDs) are a group of diseases caused by chronic and progressive degeneration of neural tissue. The main pathological manifestations are neuronal degeneration and loss in the brain and/or spinal cord. Common NDDs include Alzheimer disease (AD), Parkinson disease (PD), Huntington disease (HD), and amyotrophic lateral sclerosis (ALS). The complicated pathological characteristics and different clinical manifestations of NDDs result in a lack of sensitive and efficient diagnostic methods. In addition, no sensitive biomarkers are available to monitor the course of NDDs, predict their prognosis, and monitor the therapeutic response. Despite extensive research in recent years, analysis of amyloid β (Aβ) and α-synuclein has failed to effectively improve NDD diagnosis. Although recent studies have indicated circulating miRNAs as promising diagnostic biomarkers of NDDs, the miRNA in the peripheral circulation is susceptible to interference by other components, making circulating miRNA results less consistent. Exosomes are small membrane vesicles with a diameter of approximately 30-100 nm that transport proteins, lipids, mRNA, and miRNA. Because recent studies have shown that exosomes have a double-membrane structure that can resist ribonuclease in the blood, giving exosomal miRNA high stability and making them resistant to degradation, they may become an ideal biomarker of circulating fluids. In this review, we discuss the applicability of circulating exosomal miRNAs as biomarkers, highlight the technical aspects of exosomal miRNA analysis, and review studies that have used circulating exosomal miRNAs as candidate diagnostic biomarkers of NDDs.

中文翻译：

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循环外泌体miRNA作为神经退行性疾病的诊断生物标志物。

神经退行性疾病（NDD）是由神经组织的慢性和进行性变性引起的一组疾病。主要病理表现是脑和/或脊髓神经元变性和丧失。常见的NDD包括阿尔茨海默病（AD），帕金森病（PD），亨廷顿病（HD）和肌萎缩性侧索硬化症（ALS）。NDDs的复杂病理特征和不同的临床表现导致缺乏灵敏而有效的诊断方法。另外，没有灵敏的生物标志物可用于监测NDD的病程，预测其预后以及监测治疗反应。尽管近年来进行了广泛的研究，但对淀粉样蛋白β（Aβ）和α-突触核蛋白的分析未能有效改善NDD诊断。尽管最近的研究表明循环miRNA是NDD的有前景的诊断生物标志物，但外周循环中的miRNA容易受到其他成分的干扰，从而使循环miRNA结果的一致性降低。外泌体是直径约30-100 nm的小膜囊泡，可转运蛋白质，脂质，mRNA和miRNA。因为最近的研究表明外泌体具有双膜结构，可以抵抗血液中的核糖核酸酶，赋予外泌体miRNA高稳定性并使其具有抗降解性，所以它们可能成为循环液的理想生物标志物。在这篇综述中，我们讨论了循环外泌体miRNA作为生物标记物的适用性，强调了外泌体miRNA分析的技术方面，