Beyond Basic Characterization and Omics: Immunomodulatory Roles of Platelet-Derived Extracellular Vesicles Unveiled by Functional Testing

The proteome of anuclear platelets comprises >5000 proteins and is impacted e.g. by age and disease. The platelet secretome of over 300 proteins contains e.g. growth factors and immunomodulatory proteins and therefore, platelet products, such as platelet rich plasma are used in regenerative medicine. Platelets also release extracellular vesicles (EVs), both constitutively and upon activation. We studied 1) the tunability of platelet EVs by agonists engaging different critical platelet signaling pathways, 2) the characteristics of these EVs, and 3) macrophage responses to these EVs. Upon activating platelets, agonists have distinct impacts on the characteristics of secreted EVs, their protein and miRNA contents and functionality. These results imply that by differential activation it is possible to create tunable EVs e.g. for immunomodulatory purposes. Overall design: The goal of this study was to compare the small RNA content of platelet derived EVs (PEVS) derived from differentially activated, or non-activated platelets, as well as platelets itself. We found that different activation routes affect the small RNA cargo of PEVS suggesting that these PEVS may have diverse impact on recipient cells.