7] Measurement of platelet and megakaryocyte interaction with the subendothelial extracellular matrix

Abstract

Publisher Summary This chapter discusses the platelet and megakaryocyte interaction with the subendothelial extracellular matrix (ECM). ECM can be used as an in vitro model for the study of platelet interaction with the subendothelium. ECM initiates the morphological and biochemical alterations occurring during platelet activation at sites of an endothelial injury. The results obtained are virtually similar to those obtained using mechanically deendothelialized vascular segments. Upon incubation with ECM, platelets undergo shape changes and aggregation associated with the release of vasoactive substances and thromboxane A production. Platelet interaction with the subendothelial ECM is dependent upon the presence of certain plasma proteins, especially fibrinogen and von Willebrand factor (vWF). ECM can also provide a model to test the interaction of megakaryocytes with vessel-wall components and for the in vitro activation of megakaryocytes. During the process of platelet liberation, megakaryocytes can penetrate the sinusoid walls; the process may require close association and interaction of megakaryocytes with subendothelial matrix components on the abluminal surface of the sinusoid to attach to and penetrate the vessel wall. Unlike platelets, isolated megakaryocytes do not adhere to glass or collagen-coated surfaces. In contrast, shortly after exposure to ECM, megakaryocytes show a nonreversible adhesion and extensive formation of filopodia with a tendency toward flattening. The interaction of megakaryocytes with ECM is associated with the production of significant amounts of thromboxane A.