Enhanced Shear-induced Platelet Aggregation due to Low Temperature Storage

Platelets are transfused to prevent bleeding and induce hemostasis in cases of traumatic blood loss, such as with soldiers sustaining injuries on the battlefield. Currently, platelets isolated from volunteers are stored at room temperature with gentle agitation for up to 5 days before transfusion. This short shelf-life severely compromises platelet inventories and creates chronic shortages with the major issue being bacterial contamination. Presumably, cold storage of platelets can mitigate these issues and alleviate severely compromised platelet inventories and chronic platelet shortages. Refrigeration of platelets induces clustering of surface receptor glycoprotein (GP) Iba. In this study, we evaluated the effect of refrigeration on shear-induced platelet aggregation mediated by the interaction of GP Iba with von Willebrand factor (VWF) ligand. We observed that at arterial and stenotic shear rates, platelets stored at 4 °C for 2 days aggregated two-fold more than fresh platelets. This was independent of platelet concentration or suspension viscosity. Further, refrigerated platelets bound more annexin V and VWF than fresh platelets both under static and shear conditions. However, GP Iba expression levels as measured by four different antibodies were lower in 4 °C–stored platelets than in fresh platelets, indicating that cold–induced clustering may increase the avidity of GP Iba–VWF interaction, thus amplifying the shear response leading to increased platelet aggregation. Clinically, enhanced shear–induced platelet aggregation due to low temperature storage may be a beneficial strategy to prevent severe bleeding in trauma.