Making cold platelets even cooler: Freezing cold-stored platelets to maximize inventory potential

Refrigeration and cryopreservation are attractive alternatives that could support an extension of the current room temperature shelf life of platelets. As transfusion of cold-stored platelets (CSP) is currently limited to bleeding patients, multiple platelet inventories will be required, which may lead to expiry and wastage. To avoid this, it may be beneficial to freeze CSP to further extend their shelf life. As such, the aim of this study was to determine whether cryopreservation of expiring CSP adversely affects in vitro platelet quality.

On Day 1 following collection, double-dose single-donor platelets harvested apheresis (60% PAS-E/40% plasma; n = 10) were frozen (-80°C with 5%-6% dimethylsulfoxide) or refrigerated (2-6°C without agitation) for 14 days. The CSP was then frozen. In vitro platelet quality was measured prior to freezing, and after thawing and reconstitution in plasma.

Platelet recovery was lower in the thawed CSP (70 ± 5%), compared to standard thawed components (77 ± 8%; p = .0340). However, the recovery of all thawed platelets was above the minimum specification of 50%. Platelet glycoproteins (GPIIIa, GPIbα, and GPVI) were equivalent between thawed groups. Thawed CSP had higher P-selectin exposure, but less externalized phosphatidylserine and extracellular vesicle release, compared to standard thawed platelets. Functional parameters, including ADP-induced PAC-1 activation and thromboelastography were similar after thawing, regardless of pre-freeze storage conditions.

These data suggest that cryopreservation may be a suitable way to further extend the shelf life of CSP, thus offering a strategy to reduce wastage and enhance inventory management.