Releasates of riboflavin/UV‐treated platelets: Microvesicles suppress cytokine‐mediated endothelial cell migration/proliferation

Background Accelerated development of the platelet (PLT) storage lesion upon pathogen inactivation (PI) is associated with the release of proteins from granules and platelet microvesicles (PMVs). Whether PI treatments alter the interaction between PLT factors and the vessel endothelium is of interest in understanding the risk profile of these technologies. Study Design and Methods In a pool‐and‐split study, one platelet concentrate (PC) was treated with riboflavin/UV (RF/UV) light, while the other one was kept as an untreated control. Releasates and PMV‐depleted releasates were prepared by differential centrifugation steps on days 0, 1, 5, and 7 of storage. Cytokine/chemokine release following PI treatment was analyzed by an antibody array, and results were verified by the enzyme‐linked immunosorbent assay. PMVs were enumerated by CD41 labeling and flow cytometry. Wound scratch assays were performed using cultured Ea.hy926 cells exposed to the differently prepared releasates. Effects of releasates on the phosphorylation levels of kinases ERK and p38 expressed by endothelial cells were analyzed by immunoblot. Results Cytokine/chemokine assays identified a 2‐fold increase in epidermal growth factor released from PCs treated with RF/UV light compared with control. PMV count increased ~100‐fold following PI treatment. Unmodified releasates and PMV‐depleted releasates displayed different contributions to the kinetics of endothelial cell wound closure. This observation was associated with an increased ERK versus unaltered p38 activation in the endothelial cells. Conclusion This study identified an inhibitory impact of PMVs on endothelial cell migration/proliferation upon stimulation by released cytokines and PMVs from PLTs treated with RF/UV light for endothelial cell wound closure.