Platelet cryopreservation using a reduced dimethyl sulfoxide concentrationand second-messenger effectors as cryopreserving solution

Cryopreservation of platelets is of great interest since it could extend to years the shelf life of therapeutic platelet concentrates (PCs) and facili tate stockpiling and inventory control in blood banking. We have compared t he cryopreservation of PCs by the standard method using 6% Me2SO as cryopro tectant with the method of freezing employing low concentrations of Me2SO ( 2%) plus ThromboSol, a mixture of second-messenger effecters that protect p latelets from cold damage. PC pools were treated either with 6% Me2SO or wi th ThromboSol and 2% Me2SO and then placed directly in a -80 degrees C free zer or in the vapor phase of a liquid nitrogen freezer (-120 degrees C). Af ter storage for 1 week or for 3 months, samples were removed, thawed, and a nalyzed. Measurements included cell recovery, biochemical parameters, membr ane glycoproteins (GPs), platelet aggregation, and binding of radiolabeled von Willebrand factor (vWF) and fibrinogen. PCs cryopreserved with ThromboS ol and 2% Me2SO displayed a platelet recovery (90%) equivalent to those fro zen with 6% Me2SO. Following either cryopreservation procedure, platelets s howed increased surface expression of P-selectin and moderate loss of GP Ib alpha in comparison to fresh platelets. The aggregatory response to ristoc etin and the binding of vWF were similar in platelets frozen by either proc edure. Finally, both methods promoted comparable impairment of the reactivi ty of platelets to thrombin, aggregation and binding of fibrinogen and vWF, compared to that of fresh platelets. In summary, cryopreservation of PCs u sing reduced Me2SO concentration and ThromboSol yields platelets with in vi tro functional characteristics equivalent to those of cells frozen with the conventional method using 6% Me2SO. (C) 1999 Academic Press.