Platelet transfusions are a crucial component of support for patients with severe thrombocytopenia. Storage of platelet concentrates, however, is associated with a reduction in platelet posttransfusion recovery and hemostatic function. In this study, we established a model of mitochondrial injury that resembles platelet storage lesion. Mitochondrial injury, provoked by incubation of platelets with carbonyl cyanide m-chlorophenylhydrazone (CCCP), led to reduced posttransfusion recovery in mice, an effect that directly correlated with the duration of treatment. Damaged platelets were characterized by shape change, disruption of membrane asymmetry, surface expression of Pselectin, and profound proteolysis of GPIb␣. Using our model, we identified a key role for endogenous metalloproteinase(s) in platelet clearance, as their inhibition markedly improved posttransfusion recovery of both the mitochondriainjured and in vitro-aged mouse platelets. Metalloproteinase inhibition also prevented proteolysis of GPIb␣ on damaged platelets, thereby improving the hemostatic function of these cells in vivo. We propose that inhibition of metalloproteinase activity during storage could significantly improve the effectiveness of platelet transfusions. Surface expression of GPIb␣ might be a powerful marker to determine the quality of platelet concentrates, because it reflects metalloproteinase activity in vitro.
IntroductionPlatelet concentrates (PCs) are widely used to support patients who receive intensive therapies for hematologic malignancies and solid tumors. 1 Platelets in PCs undergo a number of events during collection, processing, and storage that adversely affect their structure and function, resulting in reduced posttransfusion recovery. 2 The observed changes are summarized as platelet storage lesion (PSL) and are indicative of partial platelet activation, including the rearrangement of the platelet cytoskeleton, microvesiculation, translocation of phosphatidyl serine (PS) to the outer leaflet of the plasma membrane, and surface expression of Pselectin. 3 GPIb-V-IX, a surface receptor mediating primary adhesion of circulating platelets to a thrombogenic surface, 4 is also affected during PSL. As shown by various groups, long-term storage induces proteolysis of an approximately 130-kDa fragment (glycocalicin) of the GPIb␣ subunit from the receptor complex. [5][6][7] The protease(s) involved in the cleavage and their relevance to platelet survival in vivo, however, remain elusive. The shelf-life of PCs is currently limited to 5 days by the risk of bacterial contamination rather than the quality of the stored platelets. However, as new methods of pathogen inactivation are currently tested for clinical use, 8,9 the potential of prolonged PC storage raises questions about what determines the survival of platelets in vivo and how PC quality can be accurately assessed in vitro.Microvesiculation and PS exposure are also hallmark characteristics of apoptosis, a physiologic program for the safe elimination of cells. In most pathway...