Procoagulant activity, but not number, of microparticles increases with age and in individuals after a single venous thromboembolism

Abstract

The Calibrated Automated Thrombogram (CAT), a plate-based assay that measures thrombin generation and inhibition in plasma samples, is modified to measure the procoagulant activity of phospholipid associated with plasma microparticles (MP). The assay uses a tissue factor trigger without addition of 4 µM exogenous phospholipid (PL) used in the standard CAT. Calibrated with 4:1 posphatidylcholine-phosphatidylserine (PCPS) liposomes, the assay defines a median of 40 nM procoagulant phospholipid (PPL) equivalents in plasma containing MPs from 50 normal donors, with a range from 20 -200 nM. Like the standard CAT, the modified assay detected no difference in plasma from 36 individuals with a history of a single episode of venous thromboembolism. However the male cases had double the PPL activity, as measured by rate of thrombin generation, of females; and there was a significant correlation among cases of increased thrombin generation with age. In contrast, there were no gender disparities or age correlations among control plasmas. The findings suggest that procoagulant activity of plasma microparticles, facilitated by a simplified, one-stage plate-based assay, offer a promising avenue of investigation of mechanisms and management of venous thromboembolic disorders.

Endothelial and platelet microparticles in patients with antiphospholipid antibodies

“…Numerous adhesion molecules, receptors, enzymes and major histocompatibility complexes (MHC) are expressed on leucocyte, endothelial and platelet microparticles and this, in addition to their size, forms the basis for microparticle detection. Microparticles have been implicated in the pathogenesis of inflammation [4], thrombosis [4] and malignancy [5]; and have been studied in conditions of cardiovascular disease such as coronary artery disease and stroke [6], haemolytic states such as TTP [7] and sickle cell disease, inflammatory conditions including Crohn's disease in addition to pregnancy, miscarriage [8,9], pre-eclampsia and venous thrombosis [10,11].…”

Modulating thrombotic diathesis in hereditary thrombophilia and antiphospholipid antibody syndrome: a role for circulating microparticles?

“…Therefore, the effects of MPs formation on the inception of VTE remain unclear. Studies on the long-term trend of MPs after the acute thrombotic event [50][51][52][53][54], despite the different assays used and the different aims and settings seem to suggest that the levels of MPs after a thrombotic event remain high despite adequate anticoagulation therapy. Moreover, therapy with low molecular weight heparin seems to reduce MPs levels more effectively than oral anticoagulant [54,55].…”

Microvesicle Production After Trauma and Its Clinical Impact on Venothromboembolism

“…Technologies Inc. Essex Junction, VT) had been added were assayed with the Calibrated Automated Thrombogram (CAT) as described by Hemker et al [17][18] and Owen et al 19 For the canonical CAT, 5 nM exogenous tissue factor (TF) and 4 nM phospholipids (PL) was added to trigger thrombin generation. The CAT assay can be configured without addition of exogenous triggers, and is referred to as native CAT (nCAT).…”

“…Isolation and characterization of MP was carried out as described by Jayachandran et al 19 Briefly, MP were based on mechanism of injury); five samples were collected in the pre-hospital setting, while the remainder were collected on arrival to the ED. Of these 80 patients, consent was obtained from 52; 13 were women (25%), and the overall mean age was 40 ± 17 years.…”