Abstract
Background: Circulating small extracellular vesicles (sEVs) and its associated proteins are of great interest in the early detection of many diseases. However, there is no gold standard for plasma sEVs isolation, especially for proteomic profiling which could be largely affected by contamination such as lipoproteins. Previous studies suggested combinations of different sEVs isolation methods could improve the purity of the isolated fractions. Nevertheless, there is no systematic evaluation of size-exclusion chromatography (SEC), ultracentrifugation (UC) and their combination in a proteomic perspective. Results: Here we exhibited that SEC+UC showed comparable recovery of sEVs with higher purity in contrast to single-step UC or SEC isolation. In our proteomic analysis, there are 992 protein species identified in the sEVs fractions isolated by SEC+UC, much more than the sEVs fractions isolated by UC (453) or SEC (682) alone. As compared to Vesiclepedia and Exocarta databases, SEC+UC kept 584 previously identified sEV-associated proteins and 360 other proteins. Furthermore, detailed analysis suggested that sEV-associated proteins, such as CD9, CD81 and ITGB1, showed the better protein rank in SEC+UC group than UC group and SEC group. Lipoproteins, the most common contamination in sEVs proteomic analysis, along with other free-floating proteins in the plasma, were largely removed in SEC+UC. Conclusions: We suggested that combining SEC with UC could significantly improve the performance of mass-spectrum (MS)-based proteomic profiling in analyzing plasma-derived sEVs.
Single-step isolation of extracellular vesicles by size-exclusion chromatography
