Current concepts of platelet physiopathology

The genesis of the modern concept of platelet physiopathology can be traced historically to many individuals and developments, including the pioneering work of Giulio Bizzozero over 100 years ago. Much knowledge has since been gained to the point that we can now define many of the elements of the platelet function in relation to the hemostatic process in terms of their molecular biology. This presentation will attempt to synthesize a simple, understandable, yet global perspective of platelet function and of its participation to the pathogenesis of arterial thrombosis. Focus will be placed on the crucial importance of cell-cell interaction. A symbolic representation of platelet plug formation using simple mathematical figures like the line, point, and triangle is helpful. The line represents the vascular system with intact endothelial cell linings. The irritation/disruption of vascular endothelium can be viewed as a point on the line representative of a localized event. From this initial (often small) stimulus, amplification occurs rapidly to produce an appropriate cellular and humoral response, represented by a triangle. Each component (vessel wall, platelets, leukocytes, coagulation and fibrinolysis systems) of this complicated response has biological characteristics which localize and amplify subsequent reactions to the site of primary injury until bleeding is arrested and the wound is healed or arterial thrombosis progresses to vascular occlusion.