Shi, Min2025-10-012025-10-012025-09-30https://hdl.handle.net/1773/53853Clinical diagnosis and differential diagnosis of Parkinson disease (PD) and multiple system atrophy (MSA), two progressive and fatal neurodegenerative disorders, can be quite challenging, especially at early disease stages, due to the overlapping clinical symptoms among various parkinsonian disorders. Biomarkers such as neuroimaging measurements and α-syn seeding aggregation assays (Real-Time Quaking-Induced Conversion or RT-QuIC) in cerebrospinal fluid (CSF) and some biopsy samples have shown promising results in improving PD and MSA diagnosis, but simpler, less expensive, accurate, and reliable biochemical markers, particularly those in easily accessible body fluids (e.g., blood), are still urgently needed to aid in clinical assessments. Growing evidence suggests that membrane-bound extracellular vesicles (EVs) play important roles in cell-to-cell communication and signaling and the pathology of neurodegenerative diseases, including PD and MSA. Additionally, EVs carrying unique disease-specific and functionally important cargo may cross the blood-brain barrier and be detected in vivo in blood, suggesting that blood-based but brain cell-derived EVs can be a valuable source of biomarkers for neurodegenerative diseases. We have recently developed a new flow cytometry-based technology (Apogee) to analyze individual EVs carrying brain cell-specific and/or disease-related protein markers in body fluids for improved biomarker accuracy and utility. These sensitive and rapid assays directly quantify intact, individual EVs, without extensive purification before quantifying disease markers, which potentially reduce inter-lab variability and increasing the clinical utility of EV-based biomarkers. Further, in recent pilot studies, we and others observed that applying modified RT-QuIC assays to plasma EV samples could clearly distinguish between PD or MSA and healthy controls as well as between PD and MSA. In this study, we propose to further fine tune and optimize our Apogee and RT-QuIC assays to analyze EVs carrying both brain cell-specific markers (e.g., L1CAM or NMDAR2A for neurons, CNPase for oligodendrocytes, and GLAST for astrocytes) and disease-related markers (e.g., α-syn species, amyloid β and tau species). The optimized assays will then be validated for their performance in MSA and PD diagnosis and differential diagnosis in two independent plasma sample cohorts. These proposed experiments will likely establish two compensatory blood-based biomarker assays for MSA and PD – a rapid screening tool (Apogee) and a more accurate assay (RT-QuIC) to replace corresponding CSF assays. Both assays can be used in future larger-scale MSA and PD biomarker studies, which may establish the foundation leading to inexpensive and widely available blood tests to aid in PD/MSA diagnosis and/or disease tracking.Attribution-NonCommercial-NoDerivs 3.0 United Stateshttp://creativecommons.org/licenses/by-nc-nd/3.0/us/Article