Comprehensive Phenotyping of Extracellular Vesicles in Blood of Healthy Humans - Insights into Cellular Origin and Biological Variability

Despite immense interest in biomarker applications of extracellular vesicles (EVs) from blood, our understanding of their physiological population in healthy humans remains limited. Using imaging and multiplex bead-based flow cytometry, we comprehensively quantified circulating EVs with respect to their cellular origin in a large cohort of healthy blood donors. We assessed coefficients of variations to characterise their biological variability and explored demographic, clinical, and lifestyle factors contributing to this variability. Cell-specific circulating EV subsets show a wide range of concentrations, which do not directly reflect concentrations of blood cells, indicating diverse patterns of EV subset release and/or uptake, even for EVs originating from the same cell type. Interestingly, tetraspanin+ circulating EVs largely originate from platelets and to a lesser extent from lymphocytes. PCA and association analyses demonstrate high biological inter-individual variability in circulating EVs across healthy humans, which can be only partly explained by the influence of sex, menopausal status, age and smoking on specific circulating EV and/or tetraspanin+ circulating EV subsets. No global influence of the explored subjects factors on circulating EVs was detected. Our findings provide the first comprehensive, quantitative data towards the cell-origin atlas of blood EVs, with important implications in the clinical use of EVs as biomarkers of disease.