Abstract 16448: Role of Platelet Fragility in the Formation of Leukocyte Aggregates

IntroductionMicrovascular obstruction is a key contributor to tissue damage in ischemia-reperfusion injury and may be caused by platelet-leukocyte interactions resulting from platelet death. Platelet-leukocyte interactions are supported by biochemical changes on the platelet surface. We recently found that biomechanical changes during platelet death may provide additional support to the formation of platelet-leukocyte aggregates.HypothesisPlatelets undergoing cell death lose structural integrity, thereby becoming an adhesive membrane shell that can link leukocytes together.MethodsPlatelet death was initiated with reactive oxygen species, as demonstrated by flow cytometry. We quantified the structural integrity and membrane tension of these platelets through aspiration and optical tweezers. We further investigated the role of membrane tension in the interaction between platelets and leukocytes by utilizing a microfluidic device at various values of wall shear stress (WSS). For these experiments, a monolayer of platelets was created within the channel before treatment with reactive oxygen species. Leukocytes were then perfused through the channel with a drag force controlled by the WSS. Corresponding interactions were quantified through microscopy analysis.ResultsAfter treatment with reactive oxygen species, a subset of platelets, exhibiting traits of cell death, become fragile with a membrane tension of 20 pN/micron. Fragility plays a role in tether formation between platelets and leukocytes in flow experiments. These tethers rupture, leaving platelet fragments on the leukocytes. Leukocytes also displace complete platelets from the surface during rolling. Platelet remnants on the leukocytes express P-selectin and phosphatidylserine, indicating the potential for additional leukocyte recruitment to the heterotypic aggregate.ConclusionsDying platelets lose structural integrity, resulting in fragmentation during leukocyte interactions. These fragments can play a role in heterotypic platelet-leukocyte aggregate formation.