Platelet density per monocyte predicts adverse events in patients after percutaneous coronary intervention

Platelet activation and prothrombotic properties in a mouse model of peritoneal sepsis

Sepsis is associated with thrombocytopenia and microvascular thrombosis. Studies have described platelets implication in this pathology but their kinetics of activation and behavior remain poorly known. We show in a mouse model of peritonitis, the appearance of platelet-rich thrombi in organ microvessels and organ damage. Complementary methods are necessary to characterize platelet activation during sepsis as circulating soluble markers and platelet-monocyte aggregates revealed early platelet activation, while surface activation markers were detected at later stage. A microfluidic based ex-vivo thrombosis assay demonstrated that platelets from septic mice have a prothrombotic behavior at shear rate encountered in microvessels. Interestingly, we found that even though phosphoinositide-3-kinase β-deficient platelet mice formed less thrombi in liver microcirculation, peritoneal sepsis activates a platelet alternative pathway to compensate the otherwise mandatory role of this lipid-kinase to form stable thrombi at high shear rate. Platelets are rapidly activated during sepsis. Thrombocytopenia can be attributed in part to platelet-rich thrombi formation in capillaries and platelet-leukocytes interactions. Platelets from septic mice have a prothrombotic phenotype at a shear rate encountered in arterioles. Further studies are necessary to unravel molecular mechanisms leading to this prothrombotic state of platelets in order to guide the development of future treatments of polymicrobial sepsis.

Whole Blood Analysis of Leukocyte-Platelet Aggregates

In inflammatory and thrombotic syndromes, platelets aggregate with circulating leukocytes, especially monocytes and neutrophils. This leukocyte-platelet aggregate formation is initiated primarily through platelet surface expression of P-selectin (CD62P), following activation-dependent degranulation of α-granules, binding to its constitutively expressed counter-receptor, P-selectin glycoprotein ligand 1 (PSGL-1), on leukocytes. Monocyte-platelet aggregates are a more sensitive marker of platelet activation than platelet surface P-selectin. Detection of leukocyte-platelet aggregates is relatively simple by whole-blood flow cytometry. Light scatter and at least one leukocyte-specific antibody are used to gate the desired population, and the presence of associated platelets is detected by immunostaining for abundant platelet-specific markers. © 2016 by John Wiley & Sons, Inc.