Absence of compensatory platelet activation in patients with severe haemophilia, but evidence for a platelet collagen-activation defect

Abstract

Severe haemophilia is a serious, haemorrhagic disorder of the plasmatic coagulation system. In this study we investigated, whether 'compensatory' activation of the platelet coagulation system occurs in this situation. Platelet function was investigated with aggregation, adhesion and flow cytometric assays. In addition, we performed clot and platelet plug formation tests and determined endogenous thrombin potentials in patients with severe haemophilia A or B; results were compared to those of healthy controls. Platelet aggregation in response to stimulation with ADP, ristocetin and epinephrine was similar in patients and controls; aggregation in response to collagen was reduced significantly in haemophiliacs. Flow cytometric analysis of P-selectin (CD 62P) and CD 63, of the conformationally changed GP IIb/IIIa with PAC 1 and of thrombospondin bound to CD 36 (GP IV) was performed at baseline and post stimulation. Baseline expression of all markers was similar in haemophiliacs and controls. After stimulation of the platelet thrombin receptors with the thrombin receptor activating peptide (TRAP) 6, the surface expression of all markers increased significantly; again, the expression was similar in haemophiliacs and controls. With thrombelastography and PFA 100 analysis, clot formation under low shear and platelet plug formation under high shear is measured. Both test results revealed a significantly reduced clot and platelet plug formation capacity in severe haemophiliacs. Our results did not reveal signs of enhanced platelet preactivation in haemophiliacs, indicating that baseline platelet reactivity in severe haemophilia remains in a neutral state, despite the severely haemorrhagic condition. As expected, both thrombin and clot formation capacities were impaired significantly in severe haemophilia. The reduced response to collagen-based platelet stimulation tests is indicative of a concomitant platelet function defect. This defect probably contributes to the intensity of bleeding events in patients with severe haemophilia.

Normal cleavage of von Willebrand factor by ADAMTS‐13 in the absence of factor VIII in patients with severe hemophilia A

“…Our results are consistent with a study by Grünewald et al [11], who studied 21 hemophilia patients, 12 with severe hemophilia A and 9 with severe hemophilia B, and found decreased collagen-induced platelet aggregation, reduced ristocetin-induced platelet aggregation (at a ristocetin concentration of 1.0 mg/ml), and prolonged closure times by Platelet Functional Analyzer (PFA) using both collagen/epinephrine and collagen/ADP cartridges, all consistent with depressed VWF antigen or activity [12–14]. ADP- and epinephrine-induced platelet aggregation was normal in these patients.…”

Factor VIII accelerates proteolytic cleavage of von Willebrand factor by ADAMTS13

“…It has previously been reported that VWF antigen and ristocetin cofactor activity are elevated (Ϸ2-fold) in severe hemophilia A patients compared with healthy controls (19). In addition, acquired von Willebrand disease has been reported in a patient receiving prolonged infusion of a high dose of recombinant FVIII after surgery (20), although other causes of VWF depletion cannot be ruled out.…”

Activation state of platelets in experimental severe hemophilia A

“…Maud Teyssandier, 1,2,3 Sandrine Delignat, 1,2,3 Julie Rayes, 1,2,3 Marijke Bryckaert, 4 Martine Jandrot-Perrus, 5 Srini V. Kaveri, 1,2,3,6 and Sébastien Lacroix-Desmazes 1,2,3,6…”

“…An earlier report had, however, failed to find signs of enhanced platelet pre-activation in patients with severe HA. 5 In order to address the question in vivo in a system that is not perturbed by the different genetic or environmental factors that are typical of the human population, we studied the state of activation and responsiveness of platelets from wild-type mice and FVIII-deficient (FVIII°) mice, an experimental model of severe hemophilia A. To this end, wild-type and FVIII° mice were crossed on the C57Bl/6 background in our laboratory to ensure the lowest genetic variability with the exception of the HA-causing gene alteration.…”