Freeze dried platelets promote clot formation, rescue thrombin induced endothelial cell permeability, and decrease pulmonary vascular leak in a murine model of hemorrhagic shock.

BACKGROUND Hemorrhagic shock (HS) and trauma induce endothelial barrier compromise, inflammation, and aberrant clotting. We have shown that fresh human platelets (Plts) and platelet extracellular vesicles mitigate vascular leak in murine models of injury. Here, we investigate the potential of freeze-dried platelets (FDPlts) to attenuate pulmonary vascular permeability, decrease inflammation and promote clotting in a murine model of HS. METHODS Human FDPlts were characterized utilizing in vitro assays of platelet marker expression, aggregation, coagulation and endothelial cell permeability. An intravital model of vascular injury in the mouse cremaster muscle was used to assess the ability of FDPlts to incorporate into clots. Mice subjected to controlled hemorrhage for 90 minutes were 1) lactated Ringer's solution (LR), 2) FDPlts, 3) fresh human Plts, 4) murine whole blood (WB) and 5) shams (only instrumented). HS mouse endpoints included coagulation, pulmonary vascular permeability and lung injury. RESULTS FDPlts expressed platelet specific markers and retained functionality similar to fresh Plts. In in vitro assays of platelet aggregation differences were noted. In vivo, FDPlts and Plts were found to incorporate into clots in post capillary venules in the mouse cremaster. HS mice resuscitated with LR displayed increased pulmonary vascular permeability compared to sham (sham, 686.6±359.7; shock+LR, 2637±954.7; p=0.001), treatment with FDPlts or WB attenuated permeability compared to shock: (shock+FDPlts, 1328±462.6; p=0.05), and (shock+WB, 1024±370.5; p=0.0108). However, Plts (Day 1-3) did not attenuate vascular leak in HS mice compared to shock (shock+Plts, 3601±1581; p=0.33). CONCLUSIONS FDPlts contribute to clot formation similar to fresh human Plts. FDPlts also attenuated vascular permeability in vitro and in vivo. Mouse WB resuscitation but not fresh Plts attenuated vascular permeability after HS. These data suggest that the effect of FDPlts may be a suitable alternative to fresh Plts in modulating hemostasis and the endotheliopathy associated with injury. LEVEL OF EVIDENCE N/A.