Differential lipid and protein compositions of PL-EVs suggest their unique cellular origins and functions, partly overlapping with PLT granule secretion. Dense PL-MVs might represent autophagic vesicles released during PLT activation and apoptosis and PL-EXs resemble lipid rafts, with a potential role in PLT aggregation and immunity. Segregation of α-synuclein and Aβ precursor protein, ApoE, and ApoJ into less dense and dense PL-MVs, respectively, show their differential carrier role of neurologic disease-related cargo.

BACKGROUND: Stored platelet concentrates (PLCs) for transfusion develop a platelet storage lesion (PSL), resulting in decreased platelet (PLT) viability and function. The processes leading to PSL have not been described in detail and no data describe molecular changes occurring in all three components of stored PLCs: PLTs, PLC extracellular vesicles (PLC‐EVs), and plasma. STUDY DESIGN AND METHODS: Fifty PLCs from healthy individuals were stored under standard blood banking conditions for 5 days. Changes in cholesterol, glycerophospholipid, and sphingolipid species were analyzed in PLTs, PLC‐EVs, and plasma by mass spectrometry and metabolic labeling. Immunoblots were performed to compare PLT and PLC‐EV protein expression. RESULTS: During 5 days, PLTs transferred glycerophospholipids, cholesterol, and sphingolipids to newly formed PLC‐EVs, which increased corresponding lipids by 30%. Stored PLTs significantly increased ceramide (Cer; +53%) and decreased sphingosine‐1‐phosphate (−53%), shifting sphingolipid metabolism toward Cer. In contrast, plasma accumulated minor sphingolipids. Compared to PLTs, fresh PLC‐EVs were enriched in lysophosphatidic acid (60‐fold) and during storage showed significant increases in cholesterol, sphingomyelin, dihydrosphingomyelin, plasmalogen, and lysophosphatidylcholine species, as well as accumulation of apolipoproteins A‐I, E, and J/clusterin. CONCLUSION: This is the first detailed analysis of lipid species in all PLC components during PLC storage, which might reflect mechanisms active during in vivo PLT senescence. Stored PLTs reduce minor sphingolipids and shift sphingolipid metabolism toward Cer, whereas in the plasma fraction minor sphingolipids increase. The composition of PLC‐EVs resembles that of lipid rafts and confirms their role as carriers of bioactive molecules and master regulators in vascular disease.

During in vitro senescence, PLTs degrade large RNA species. Concomitantly, they up-regulate a distinct set of known small RNA species involved in atherosclerosis, inflammation, and neurodegeneration. PL-EVs enrich miRNA species, likely supporting the role of PLTs and PL-EVs in vascular homeostasis and as carriers of neurodegenerative disease-related miRNA cargo.

BACKGROUND Platelet‐derived extracellular vesicles (PL‐EVs) are present in plateletpheresis concentrates (PCs) and may influence the quality of PCs. The aim of the study was to analyze PC‐derived PL‐EVs and to correlate them with standard quality control (QC) variables of PCs and with donor‐specific laboratory variables. STUDY DESIGN AND METHODS PL‐EVs were analyzed by standard as well as advanced high‐sensitivity flow cytometry (FCM) and nanoparticle tracking analysis. A hematology analyzer was applied to the determination of platelet (PLT) count and immature PLT fraction (IPF). Functional capacity of PLTs (CD62P in response to thrombin receptor‐activating peptide 6 activation) was measured by FCM. All in vitro measurements were carried out on Day 0 and on Day 5. Altogether, a total of 42 PC samples, 15 irradiated on Day 0, were investigated. RESULTS Externalization of CD62P, as an indicator of intact PLT function, significantly decreased during in vitro PLT senescence and CD62P expression inversely correlated with increased PL‐EV levels. Interestingly, in fresh PCs a significant correlation was found between PL‐EVs and different hemapheresis instruments, duration of apheresis, and IPF count in peripheral blood of the donor before apheresis. In senescent PCs, the body mass index of donors inversely correlated with the PL‐EV counts. CONCLUSION Loss of PLT function in PCs was associated with increased PL‐EV levels. Shedding of PL‐EVs depends on shear stress influenced by different hemapheresis settings and diverse preanalytical conditions of donors. PL‐EV analysis may stimulate new quality and apheresis strategies for more vital PLTs for transfusion.

nHDL3 and apoA-I improve PLT membrane homeostasis and intracellular lipid processing and increase CE efflux, antagonizing PSL-related reduction in PLT viability and function and PL-EV release. We suggest uptake and catabolism of nHDL3 into the PLT open canalicular system. As supplement in PLCs, nHDL3 or apoA-I from Fraction IV of plasma ethanol fractionation have the potential to improve PLC quality to prolong storage.