Choosing the optimal dilution medium for pooled platelet concentrates, thawed after cryopreservation

Background. The current methods of cryopreservation, working with pooled platelet concentrates (PPC), require optimization. An urgent task is to select adequate dilution of thawed doses in order to reduce the toxic effect of cryoprotector. The aim of work. To evaluate the effect of plasma-substituting solutions on the morphofunctional properties of pooled platelet concentrates after their cryopreservation, cryopreservation and defrosting. Materials and methods. We studied morphofunctional properties of platelets, cryopreserved in the presence of 5–6% dimethyl sulfoxide and 0.5% dextran and diluted after defrosting with different media. Autologous cell-free medium, isolated from PPC before platelet freezing, allogeneic fresh-frozen plasma (FFP), plasma-substituting InterSol solution, plasma substitute rheopolyglucine were used for platelet resuspension. To assess the quality of platelets we used the method of thromboelastography and the method of morphofunctional platelet analysis, including vital staining with fluorochrome dyes. Results. The initial PPC-samples significantly differed in the viability, structural and functional features of platelets. When thawed PPC-samples were diluted with in ratio 1:9, in experiments with autologous medium or FFP the safety of the total number of biologically complete platelets averaged 52–53%, with InterSol solution – 37%, rheopolyglucine – 8%. InterSol solution caused spontaneous platelet activation, while rheopolyglucine caused spontaneous activation associated with massive platelet destruction. Correlation was revealed between the preservation of biologically complete platelets after defrosting of the PPC and morphofunctional parameters in the initial PPC. When thawed PPC-samples were diluted with autologous medium or FFP in ratio 1:9, the morphofunctional status of platelets did not change for 2–3 hours, in ratio 1:4 – for 30 minutes. Conclusions. Before cryopreservation PPC presented decrease of morphofunctional characteristics of platelets, followed with their increased reactivity. Resuspension of thawed PPC in pure InterSol solution or polyglucine leads to rapid loss of platelet quality and is ineffective. For the dilution of thawed PPC it is recommended to use autologous plasma medium or allogeneic fresh frozen plasma.