The hemostatic activity of cryopreserved platelets is mediated by phosphatidylserine-expressing platelets and platelet microparticles
- We acknowledge that the Australian Government fully funds the Australian Red Cross Blood Service for the provision of blood products and services to the Australian Community. This study was partly funded by the Defence Health Foundation. CPC was supported by a Summer Research Scholarship from the University of Sydney Medical School.
Cryopreservation of platelets (PLTs) at −80°C with dimethyl sulfoxide (DMSO) can extend the shelf life from 5 days to 2 years. Cryopreserved PLTs are reported to have a greater in vivo hemostatic effect than liquid-stored PLTs. As such, the aim of this study was to understand the mechanisms responsible for the hemostatic potential of cryopreserved PLTs and the contribution of the reconstitution solution to this activity.
Study Design and Methods
DMSO (5% final concentration) was added to buffy coat–derived PLTs, followed by prefreeze removal of DMSO and storage at −80°C. Cryopreserved PLTs (n = 8 per group) were thawed at 37°C, reconstituted with either 1 unit of thawed frozen plasma or PLT additive solution (PAS-G). In vitro assays were performed before freezing and after thawing to assess the hemostatic activity of PLTs.
Cryopreserved PLTs expressed high levels of phosphatidylserine and contained significantly more phosphatidylserine-positive PLT microparticles than liquid-stored PLTs. This was accompanied by a significant decrease in the time to clot formation and clot strength, as measured by thromboelastography. The supernatant from cryopreserved PLTs was sufficient to reduce the phosphatidylserine-dependent clotting time and increase the thrombin generation potential. Overall, plasma-reconstituted cryopreserved PLTs were more procoagulant than those reconstituted in PAS-G.
PLT cryopreservation results in the generation of phosphatidylserine-expressing PLT microparticles which contribute to the hemostatic activity. Understanding the hemostatic activity of these components may assist in extending the use of these specialized components beyond military applications.