Absence of platelet-dependent fibrin formation in a patient with Scott syndrome

Summary

To gain insight into the contribution of platelet-dependent thrombin formation in haemostasis and thrombosis, we investigated under flow conditions the haemostatic functions of platelets from a patient with Scott syndrome. Scott platelets are characterised by a diminished platelet-dependent thrombin generation. Thrombin generation was determined by calibrated automated thrombography and flow-based experiments were performed to reveal collagen-mediated platelet activation and fibrin deposition. Our studies indicate that adherent Scott platelets do not differ from control platelets in the formation of stable platelet aggregates under static and flow conditions. While for adherent control platelets a shape change, e.g. balloon formation, and externalisation of phosphatidylserine (PS) is associated with an increase in intracellular calcium concentration, this is not the case for Scott platelets. The calcium-induced morphological changes in control platelets are accompanied with a diminished recruitment of free flowing platelets. Scott platelets, not showing a calcium-induced shape change, also lost the ability to recruit free flowing platelets. These findings rebut the hypothesis that the mild bleeding tendency of Scott syndrome patients is due to a preserved adhesive activity of patient’s platelets. Perfusion of tissue factor (TF)-activated control blood over immobilised collagen results in the formation of fibrin fibers that radiate from platelet aggregates. Although platelet aggregates were also observed after perfusion with TF-activated Scott blood, fibrin deposition was not observed. In conclusion, our findings indicate that platelet adhesion and spreading on a collagen matrix in the absence of fibrin formation is sufficient to sustain haemostasis under non-traumatic conditions.

Keywords

Haemostasis - platelet physiology - thrombin - fibrinogen / fibrin - Scott syndrome

• References

• 1 Jackson SP. The growing complexity of platelet aggregation. Blood 2007; 109: 5087-5095.
• 2 Furie B, Furie BC. Mechanisms of thrombus formation. N Engl J Med 2008; 359: 938-949.
• 3 Ono A, Westein E, Hsiao S. et al. Identification of a fibrin-independent platelet contractile mechanism regulating primary hemostasis and thrombus growth. Blood 2008; 112: 90-99.
• 4 Sixma JJ, van den Berg A. The haemostatic plug in haemophilia A: a morphological study of haemostatic plug formation in bleeding time skin wounds of patients with severe haemophilia A. Br J Haematol 1984; 58: 741-753.
• 5 Wolberg AS, Monroe DM, Roberts HR. et al. Elevated prothrombin results in clots with an altered fiber structure: a possible mechanism of the increased thrombotic risk. Blood 2003; 101: 3008-3013.
• 6 Monroe DM, Hoffman M. What does it take to make the perfect clot?. Arterioscler Thromb Vasc Biol 2006; 26: 41-48.
• 7 Weiss HJ, Vicic WJ, Lages BA. et al. Isolated deficiency of platelet procoagulant activity. Am J Med 1979; 67: 206-213.
• 8 Zwaal RF, Comfurius P, Bevers EM. Scott syndrome, a bleeding disorder caused by defective scrambling of membrane phospholipids. Biochim Biophys Acta 2004; 1636: 119-128.
• 9 Weiss HJ, Turitto VT, Baumgartner HR. Role of shear rate and platelets in promoting fibrin formation on rabbit subendothelium. Studies utilizing patients with quantitative and qualitative platelet defects. J Clin Invest 1986; 78: 1072-1082.
• 10 Parry DH, Giddings JC, Bloom AL. Familial haemostatic defect associated with reduced prothrombin consumption. Br J Haematol 1980; 44: 323-334.
• 11 Toti F, Satta N, Fressinaud E. et al. Scott syndrome, characterized by impaired transmembrane migration of procoagulant phosphatidylserine and hemorrhagic complications, is an inherited disorder. Blood 1996; 87: 1409-1415.
• 12 Munnix IC, Harmsma M, Giddings JC. et al. Storemediated calcium entry in the regulation of phosphatidylserine exposure in blood cells from Scott patients. Thromb Haemost 2003; 89: 687-695.
• 13 Albrecht C, McVey JH, Elliott JI. et al. A novel missense mutation in ABCA1 results in altered protein trafficking and reduced phosphatidylserine translocation in a patient with Scott syndrome. Blood 2005; 106: 542-549.
• 14 Wielders SJ, Bennaghmouch A, Reutelingsperger CP. et al. Anticoagulant and antithrombotic properties of intracellular protease-activated receptor antagonists. J Thromb Haemost 2007; 05: 571-576.
• 15 Billy D, Briede J, Heemskerk JW. et al. Prothrombin conversion under flow conditions by prothrombinase assembled on adherent platelets. Blood Coagul Fibrinolysis 1997; 08: 168-174.
• 16 Heemskerk JW, Vuist WM, Feijge MA. et al. Collagen but not fibrinogen surfaces induce bleb formation, exposure of phosphatidylserine, and procoagulant activity of adherent platelets: evidence for regulation by protein tyrosine kinase-dependent Ca2+ responses. Blood 1997; 90: 2615-2625.
• 17 Briede JJ, Heemskerk JWM, Hemker HC. et al. Heterogeneity in microparticle formation and exposure of anionic phospholipids at the plasma membrane of single adherent platelets. Biochimica et Biophysica Acta (BBA) - Molecular Cell Res 1999; 1451: 163-172.
• 18 Wielders SJ, Ungethum L, Reutelingsperger CP. et al. Factor Xa-driven thrombin generation in plasma: dependency on the aminophospholipid density of membranes and inhibition by phospholipid-binding proteins. Thromb Haemost 2007; 98: 1056-1062.
• 19 Kulkarni S, Jackson SP. Platelet factor XIII and calpain negatively regulate integrin αIIbβ3 adhesive function and thrombus growth. J Biol Chem 2004; 279: 30697-30706.
• 20 Briede JJ, Heemskerk JW, Hemker HC. et al. Heterogeneity in microparticle formation and exposure of anionic phospholipids at the plasma membrane of single adherent platelets. Biochim Biophys Acta 1999; 1451: 163-172.
• 21 Ruggeri ZM, Orje JN, Habermann R. et al. Activation-independent platelet adhesion and aggregation under elevated shear stress. Blood 2006; 108: 1903-1910.
• 22 Watanabe N, Bodin L, Pandey M. et al. Mechanisms and consequences of agonist-induced talin recruitment to platelet integrin {alpha}IIb{beta}3. J Cell Biol 2008; 181: 1211-1222.
• 23 Drake TA, Morrissey JH, Edgington TS. Selective cellular expression of tissue factor in human tissues. Implications for disorders of hemostasis and thrombosis. Am J Pathol 1989; 134: 1087-1097.
• 24 Orfeo T, Brummel-Ziedins KE, Gissel M. et al. The nature of the stable blood clot procoagulant activities. J Biol Chem 2008; 283: 9776-9786.