A revised model of platelet aggregation.

In this study we have examined the mechanism of platelet aggregation under physiological flow conditions using an in vitro flow-based platelet aggregation assay and an in vivo rat thrombosis model. Our studies demonstrate an unexpected complexity to the platelet aggregation process in which platelets in flowing blood continuously tether, translocate, and/or detach from the luminal surface of a growing platelet thrombus at both arterial and venous shear rates. Studies of platelets congenitally deficient in von Willebrand factor (vWf) or integrin alpha(IIb)beta(3) demonstrated a key role for platelet vWf in mediating platelet tethering and translocation, whereas integrin alpha(IIb)beta(3) mediated cell arrest. Platelet aggregation under flow appears to be a multistep process involving: (a) exposure of vWf on the surface of immobilized platelets; (b) a reversible phase of platelet aggregation mediated by the binding of GPIbalpha on the surface of free-flowing platelets to vWf on the surface of immobilized platelets; and (c) an irreversible phase of aggregation dependent on integrin alpha(IIb)beta(3). Studies of platelet thrombus formation in vivo demonstrate that this multistep adhesion mechanism is indispensable for platelet aggregation in arterioles and also appears to promote platelet aggregate formation in venules. Together, our studies demonstrate an important role for platelet vWf in initiating the platelet aggregation process under flow and challenge the currently accepted view that the vWf-GPIbalpha interaction is exclusively involved in initiating platelet aggregation at elevated shear rates.

[1]  M. Nakashima,et al.  Vessel Wall Injury and Arterial Thrombosis Induced by a Photochemical Reaction , 1995, Thrombosis and Haemostasis.

[2]  J. Moake,et al.  Platelets and shear stress. , 1996, Blood.

[3]  D. Fass,et al.  Transplantation of normal bone marrow into a pig with severe von Willebrand's disease. , 1986, The Journal of clinical investigation.

[4]  C. Samama,et al.  Function of von Willebrand factor after crossed bone marrow transplantation between normal and von Willebrand disease pigs: effect on arterial thrombosis in chimeras. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[5]  A. Colombatti,et al.  Identification of Domains Responsible for von Willebrand Factor Type VI Collagen Interaction Mediating Platelet Adhesion under High Flow* , 1999, The Journal of Biological Chemistry.

[6]  M. Ginsberg,et al.  Multimeric structure of platelet factor VIII/von Willebrand factor: the presence of larger multimers and their reassociation with thrombin-stimulated platelets. , 1982, Blood.

[7]  H. Weiss,et al.  Effect of shear rate on platelet interaction with subendothelium in citrated and native blood. I. Shear rate--dependent decrease of adhesion in von Willebrand's disease and the Bernard-Soulier syndrome. , 1978, The Journal of laboratory and clinical medicine.

[8]  H. Gralnick,et al.  Fibrinogen competes with von Willebrand factor for binding to the glycoprotein IIb/IIIa complex when platelets are stimulated with thrombin. , 1984, Blood.

[9]  Brian Savage,et al.  Specific Synergy of Multiple Substrate–Receptor Interactions in Platelet Thrombus Formation under Flow , 1998, Cell.

[10]  S. Jackson,et al.  Glycoprotein (GP) Ib-IX-transfected Cells Roll on a von Willebrand Factor Matrix under Flow , 1999, The Journal of Biological Chemistry.

[11]  A. van Dorsselaer,et al.  Gene cloning of rat and mouse platelet glycoprotein V: identification of megakaryocyte-specific promoters and demonstration of functional thrombin cleavage. , 1997, Blood.

[12]  R. Hynes,et al.  A mouse model of severe von Willebrand disease: defects in hemostasis and thrombosis. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[13]  H. Gralnick,et al.  Identification of platelet glycoprotein IIb/IIIa as the major binding site for released platelet-von Willebrand factor. , 1986, Blood.

[14]  S. Usami,et al.  A simplified method for culture of endothelial cells and analysis of adhesion of blood cells under conditions of flow. , 1993, Microvascular research.

[15]  S. Goto,et al.  Distinct mechanisms of platelet aggregation as a consequence of different shearing flow conditions. , 1998, The Journal of clinical investigation.

[16]  K Watanabe,et al.  The role of von Willebrand factor and fibrinogen in platelet aggregation under varying shear stress. , 1991, The Journal of clinical investigation.

[17]  R. Gordon,et al.  Localization of surface vWF on resting and stimulated platelets. , 1987, Blood.

[18]  P. Mannucci,et al.  Platelet von Willebrand factor in inherited and acquired bleeding disorders. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[19]  V. Fuster,et al.  Role of von Willebrand factor in mediating platelet-vessel wall interaction at low shear rate; the importance of perfusion conditions. , 1989, Blood.

[20]  H. Weiss,et al.  Decreased adhesion of platelets to subendothelium in von Willebrand's disease. , 1974, The Journal of laboratory and clinical medicine.

[21]  J. George,et al.  Human platelet surface binding of endogenous secreted factor VIII-von Willebrand factor and platelet factor 4. , 1982, Blood.

[22]  Yale Ce,et al.  Critical bleeding and plasma volumes of the adult germfree rat. , 1972 .

[23]  D. Baruch,et al.  Platelet von Willebrand factor: evidence for its involvement in platelet adhesion to collagen. , 1987, Blood.

[24]  A. Tosetto,et al.  The bleeding time in normal subjects is mainly determined by platelet von Willebrand factor and is independent from blood group. , 1992, Thrombosis research.

[25]  B. Cambou,et al.  Optimization of a Recombinant von Willebrand Factor Fragment as an Antagonist of the Platelet Glycoprotein Ib Receptor , 1993, Bio/Technology.

[26]  K. Kaplan,et al.  Factor VIII-related antigen in human blood platelets: localization and release by thrombin and collagen. , 1979, The Journal of laboratory and clinical medicine.

[27]  S. Jackson,et al.  Calpain Regulation of Cytoskeletal Signaling Complexes in Von Willebrand Factor-stimulated Platelets , 1997, The Journal of Biological Chemistry.

[28]  K. Clemetson.  Primary haemostasis: Sticky fingers cement the relationship , 1999, Current Biology.

[29]  H. Gralnick,et al.  Platelet von Willebrand factor: an important determinant of the bleeding time in type I von Willebrand's disease. , 1986, Blood.

[30]  H. Gralnick,et al.  Purification and characterization of human platelet von Willebrand factor , 1994, British journal of haematology.

[31]  M. Freund,et al.  Experimental Thrombosis on a Collagen Coated Arterioarterial Shunt in Rats: A Pharmacological Model to Study Antithrombotic Agents inhibiting Thrombin Formation and Platelet Deposition , 1993, Thrombosis and Haemostasis.

[32]  C. Mitchell,et al.  Tyrosine kinases regulate the cytoskeletal attachment of integrin alpha IIb beta 3 (platelet glycoprotein IIb/IIIa) and the cellular retraction of fibrin polymers. , 1994, The Journal of biological chemistry.

[33]  Z. Ruggeri,et al.  Mechanisms of Shear-induced Platelet Adhesion and Aggregation , 1993, Thrombosis and Haemostasis.

[34]  H. Holmsen.  Platelet responses and metabolism , 1986 .

[35]  R S Reneman,et al.  Wall shear rate in arterioles in vivo: least estimates from platelet velocity profiles. , 1988, The American journal of physiology.

[36]  C. Mitchell,et al.  Tyrosine Kinases Regulate the Cytoskeletal Attachment of Integrin a , , & ( Platelet Glycoprotein IIb / IIIa ) and the Cellular Retraction of Fibrin Polymers * , 2001 .

[37]  Brian Savage,et al.  Initiation of Platelet Adhesion by Arrest onto Fibrinogen or Translocation on von Willebrand Factor , 1996, Cell.