Primary and secondary hemostatic functionalities of rehydrated, lyophilized platelets

BACKGROUND: The rehydrated, lyophilized (RL) platelet (PLT) is being developed as a hemostatic infusion agent for the control of active bleeding. The key to the method for preparing RL PLTs is a mild aldehyde stabilization that allows for freezing and lyophilizing without cellular rupture. RL PLTs have been shown to be effective at rapidly controlling bleeding in animal models of cardiopulmonary bypass induced PLT dysfunction and washout thrombocytopenia, yet the rehydrated cells have proved to be safe with respect to induction of pathologic intravascular coagulation. STUDY DESIGN AND METHODS: In vitro and in vivo studies were performed to better understand the differential effect of the RL PLT manufacturing method on primary and secondary hemostatic processes. The functionality of the von Willebrand factor (VWF) receptor (glycoprotein Ib) complex, the PAR receptors, integrin-mediated aggregation (inside-out signaling), and surface membrane prothrombin to thrombin conversion systems were investigated. RESULTS: RL PLTs were found to retain native VWF-mediated adhesion and surface thrombin generation functions. In contrast, the coupling of thrombin receptors to integrin inside-out signaling was largely inhibited. CONCLUSION: These results suggest that RL PLTs may stop bleeding by forming primary hemostatic plugs and providing a localized source of thrombin for secondary hemostatic processes, yet do not build up occlusive pathologic clots possibly because integrin functions for forming PLT-PLT aggregates are partially inhibited.