In vitro investigations of the clot formation and resolution properties of cryopreserved platelets.

While platelets for transfusion are traditionally stored at room temperature (20-24°C), cryopreservation at -80°C is attractive, as it facilitates an extension of the shelf-life from 7 days to several years. Cryopreserved platelets display enhanced procoagulant capacity, which may distort the balance between clot formation and resolution. Platelets were frozen at -80°C using DMSO and thawed and resuspended in fresh plasma before testing. Fresh components (day 1) were tested in parallel. The supernatant of thawed platelets contained a higher concentration of fibrinogen, plasminogen, TAFI, FXIII, PAI-1, and tPA, compared to fresh platelets. However, this was primarily due to the addition of fresh plasma at the time of platelet thawing, with the exception of PAI-1. Thawed platelets displayed a higher surface abundance of PAI-1 and FXIII, compared to fresh platelets. The clots formed by thawed platelets underwent retraction; although this was affected by time and platelet concentration. tPA-induced fibrinolysis, measured by thromboelastography (TEG), was not statistically different between fresh and thawed platelets. Although differences in the abundance of fibrinolytic mediators were observed in thawed platelets, compared to room temperature platelets, clot resolution properties were conserved. This work provides a more complete understanding of the overall hemostatic capacity of cryopreserved platelets.