Platelet shape change

Platelets circulate quiescently in a flat, discoid state and undergo specific morphological changes to support granule secretion, integrin activation, platelet-platelet aggregation, adhesion, and contractile processes in the initial stages of the platelet activation program. Dynamic changes in platelet shape have long been associated with platelet activation and hemostatic and thrombotic function. Classical microscopy studies, together with the development of light transmission aggregometry, allowed for an advance of platelet shape change assays as important experimental and clinical tools. Pharmacology efforts have specified how platelet agonists, including thrombin, collagen, and ADP activate G proteincoupled receptors (GPCRs) or ITAM-bearing receptors to increase myosin light chain phosphorylation to drive actomyosin contractions and other dynamic cytoskeletal processes that form the basis for the initiation of platelet shape change. Advances in imaging technologies and molecular tools continue to provide mechanistic insights into platelet shape change as one of the earliest morphological manifestations of platelet activation, a potential biomarker for platelet-based disease states and a powerful tool in basic and translational studies of platelet function .