Small extracellular vesicles are released ex vivo from platelets into serum and from residual blood cells into stored plasma

Small extracellular vesicles (sEV) purified from blood have great potential clinically as biomarkers for systemic disease; however interpretation is complicated by release of sEV ex vivo after taking. To quantify the problem and devise ways to minimise it, we characterised in paired serum, plasma platelet poor (PPP) samples healthy donors. Immunoblotting showed twofold greater abundance CD9 fractions fresh serum than or PPP. MACSPlex confirmed this, that proteins expressed on sEV, either exclusively (CD41b, CD42a CD62P) more widely (HLA-ABC, CD24, CD29 CD31) were also abundant; contrast non-platelet (including CD81) no different. Storage (but not serum) increased selected leukocyte at least this could be recapitulated activating cells Ca2+, an effect abrogated This suggests a substantial proportion stored generated vivo, which case Thus provide strategies generation criteria identifying those present vivo.