Background: Platelet concentrates are used to prevent/stop bleeding in thrombocytopenias and/or thrombocytopathies. Stored platelets undergo changes that can reduce their hemostatic potential and increase the risk of post-transfusion complications.

Aims: To study dynamic morphological and functional alterations in platelets during storage of platelet concentrates.

Methods: 150 samples of apheresis human platelet concentrates in a platelet additive solution SSP+ were analyzed within 1-7 days of storage at 20-24°C. Platelet functionality was assessed using flow cytometry by expression of P-selectin, active integrin αIIbβ3, and phosphatidylserine before and after stimulation with the TRAP peptide. In addition, the mitochondrial transmembrane potential, platelet contractility (quantified as the extent of plasma clot shrinkage), collagen- and TRAP-induced platelet aggregation were measured together with imaging of platelets by scanning electron microscopy.

Results: Expression of P-selectin and phosphatidylserine in unstimulated platelets increased during storage, while the level of active αIIbβ3 remained low. The TRAP-induced expression of P-selectin, αIIbβ3, and phosphatidylserine was highest in fresh platelet concentrates and decreased gradually during storage. Platelet aggregation followed similar dynamics. The ability of platelets to contract plasma clots was almost unchanged in most samples and the mitochondrial transmembrane potential also remained high throughout the period of observation. Morphologically, the discoid quiescent platelets predominated in all samples; however, starting from the 1st day, a fraction of spindle-like platelets appeared and increased progressively, and beginning from the 3rd day, spherical forms and platelet microaggregates were revealed.

Conclusion(s): The results obtained indicate that platelets in concentrates initially have a high functional potential, which declines progressively with time due to spontaneous activation and a simultaneous decrease in reactivity and structural alterations. Platelet contractility turns out to be stable up to one week. The results obtained substantiate the therapeutic efficacy of fresh platelet concentrates as hemostatic agents with their usefulness decreasing over time.

Grant 21-75-00010 from the Russian Science Foundation.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/changes-in-platelet-functionality-and-morphology-during-storage-of-platelet-concentrates/