Proteomic analysis of extracellular vesicles in cerebrospinal fluid of patients with Alzheimer's disease

Cerebrospinal fluid (CSF) contains different types of extracellular vesicles (EVs) with undisclosed biomarker potential for neurodegenerative diseases. The aims of the present study were: i) to compare the proteome EVs isolated using different ultracentrifugation speed ii) to preliminary explore the EVs proteome in a common neurodegenerative disorder, Alzheimers disease (AD) compared to neurological controls. CSF samples from control subjects and AD patients were pooled separately (15 mL) and subjected to ultracentrifugation (UC) at different speeds (20,000g and 100,000g) to isolate separate EV fractions (P20 and P100). The proteome was analysed using high-resolution mass spectrometry (LC-MS/MS) and comparisons were made using bioinformatic analysis. EVs isolated at 100,000g (P100) had a proteome consistent with vesicles secreted via an ESCRT-dependent mechanism, being highly enriched in alix (PDCD6IP), syntenin-1 (SDCBP) and TSG101. EVs isolated at 20,000g were substantially different, showing enrichment in cytoskeletal and cell adhesion molecules. The pools from patients diagnosed with AD showed a distinct protein profile of CSF EVs, with increased levels of ADAM10, SPON1, CH3IL1 and MDK in the P100 fraction. CSF EV offer a new potential biosource of protein markers for AD detection and a complementary framework to the analysis of whole biological fluids for biomarker discovery.