Platelet adhesion and thrombus formation on subendothelium in platelets deficient in glycoproteins IIb-IIIa, Ib, and storage granules

Abstract

Patients whose platelets are deficient in glycoprotein (GP) Ib, IIb- IIIa (thrombasthenia), or granule substances (storage pool deficiency, SPD) were studied to define further the properties of platelets that mediate platelet adhesion and thrombus formation on subendothelium. Both nonanticoagulated and citrated blood were exposed to everted, de- endothelialized rabbit vessel segments under controlled flow conditions and shear rates varying from 650 to 3,300 sec-1. Morphometry was used to measure platelet thrombus dimensions and the percentage of the subendothelial surface covered with contact (C) or spread (S) platelets. Adhesion was defined as C + S. The results in SPD demonstrated (1) reduced thrombus dimensions in delta-SPD (pure dense granule deficiency) in proportion to the magnitude of the dense granule defect; (2) an even greater reduction in thrombus dimensions in patients with combined deficiencies of alpha and dense granules (alpha delta-SPD); and (3) impaired platelet adhesion at several conditions in alpha delta-SPD and, in delta-SPD, a hematocrit-dependent impairment of adhesion in citrated blood at 2,600 sec-1. In thrombasthenia, platelets were present as a monolayer on the subendothelial surface in both nonanticoagulated and citrated blood, indicating an absolute requirement for GPIIb-IIIa in promoting platelet-platelet interaction at all shear rates and perfusion times. Two types of abnormalities in platelet-vessel wall interactions were observed. In nonanticoagulated blood, the percentage of platelets in the C phase was consistently increased at all shear rates, but C + S values were normal. These observations indicate that platelets deficient in GPIIb-IIIa do not spread normally on the subendothelial surface exposed to nonanticoagulated blood. With citrated blood, the C + S value in thrombasthenia was reduced at both 800 and 2,600 sec-1, as in von Willebrand's disease, and a similar degree of reduction (about 50%) was observed in normal blood treated with a monoclonal antibody to GPIIb- IIIa. The findings, together with theoretical considerations, are consistent with an hypothesis that GPIIb-IIIa mediates the spreading of platelets on subendothelium following the initial attachment through GPIb and that GPIIb-IIIa may be considered an adhesion site on the platelet membrane. Abnormalities of GPIIb-IIIa may, depending on the conditions of study, result in either increased values of C platelets or decreased values of C + S. The results of the study further suggest that a complex interaction of platelet granule factors and membrane GP mediate platelet adhesion and thrombus formation.

A review of inherited platelet disorders with guidelines for their management on behalf of the UKHCDO

“…Thrombasthenic platelets do not aggregate in response to agonists, such as ADP, collagen, thrombin and adrenaline, but do agglutinate in the presence of ristocetin. Affected platelets adhere normally to damaged subendothelium but fail to spread normally and do not form platelet aggregates (Weiss et al , 1986). Definitive diagnosis is made by flow cytometry using antibodies to GPIIb (CD41) and GPIIIa (CD61).…”

A systematic overview of the first pasteurised VWF/FVIII medicinal product, Haemate®P/ Humate®‐P: History and clinical performance

“…platelet aggregation and thrombus formation). Binding of VWF to platelets is at first via the glycoprotein Ibα (GPIbα) receptor, and then also via the integrin αIIbβ3 receptor, and ultimately leads to platelet activation and subsequent multi‐platelet adhesion (9). Platelet adhesion leads to the formation of a platelet plug and cessation of bleeding (10, 11).…”

Infusible platelet membranes improve hemostasis in thrombocytopenic blood: experimental studies under flow conditions

“…Platelets contribute to the hemostatic process in two ways. First, their adhesive and cohesive functions lead to the formation of a hemostatic plug 1 . Second, they can activate coagulation mechanisms though the exposure of an adequate phospholipid surface, acting as a catalytic site for the development of coagulation that will consolidate the hemostatic plug initially constituted 2 .…”