Plasma procoagulant phospholipid clotting time and venous thromboembolism risk.

BACKGROUND: Negatively charged procoagulant phospholipids, phosphatidylserine (PS) in particular, are vital to coagulation and expressed on the surface membrane of extracellular vesicles. No previous study has investigated the association between plasma procoagulant phospholipid clotting time (PPLCT) and future risk of venous thromboembolism (VTE). OBJECTIVES: To investigate the association between plasma PPLCT and the risk of incident VTE in a nested case-control study. METHODS: We conducted a nested case-control study in 296 VTE patients and 674 age- and sex-matched controls derived from a general population cohort (The Tromsø Study 1994-2007). PPLCT was measured in platelet-free plasma using a modified factor Xa-dependent clotting assay. Logistic regression was used to estimate odds ratio (OR) with 95% confidence intervals (CI) for VTE with PPLCT modelled as a continuous variable across quartiles and in dichotomized analyses. RESULTS: There was a weak inverse association between plasma PPLCT and risk of VTE per 1 standard deviation increase of PPLCT (OR 0.93, 95% CI 0.80-1.07) and when comparing those with PPLCT in the highest quartile (OR 0.89, 95% CI 0.60-1.30) with those in the lowest quartile. Subjects with PPLCT >95th percentile had substantially lowered OR for VTE (OR 0.35, 95% CI 0.13-0.81). The inverse association was stronger when the analyses were restricted to samples taken shortly before the event. The risk estimates by categories of plasma PPLCT were similar for deep vein thrombosis and pulmonary embolism. CONCLUSION: Our findings suggest that high plasma PPLCT is associated with reduced risk of VTE.

Impact of preanalytical conditions on plasma concentration and size distribution of extracellular vesicles using Nanoparticle Tracking Analysis.

Optimal pre-analytical handling is essential for valid measurements of plasma concentration and size distribution of extracellular vesicles (EVs). We investigated the impact of plasma preparation, various anticoagulants (Citrate, EDTA, CTAD, Heparin), and fasting status on concentration and size distribution of EVs measured by Nanoparticle Tracking Analysis (NTA). Blood was drawn from 10 healthy volunteers to investigate the impact of plasma preparation and anticoagulants, and from 40 individuals from a population-based study to investigate the impact of postprandial lipidemia. Plasma concentration of EVs was measured by NTA after isolation by high-speed centrifugation, and size distribution of EVs was determined using NTA and scanning electron microscopy (SEM). Plasma concentrations and size distributions of EVs were essentially similar for the various anticoagulants. Transmission electron microscopy (TEM) confirmed the presence of EVs. TEM and SEM-analyses showed that the EVs retained spherical morphology after high-speed centrifugation. Plasma EVs were not changed in postprandial lipidemia, but the mean sizes of VLDL particles were increased and interfered with EV measurements (explained 66% of the variation in EVs-concentration in the postprandial phase). Optimization of procedures for separating VLDL particles and EVs is therefore needed before NTA-assessment of EVs can be used as biomarkers of disease.

Antibody-based targeting of alternatively spliced tissue factor: a new approach to impede the primary growth and spread of pancreatic ductal adenocarcinoma.

Alternatively spliced Tissue Factor (asTF) is a secreted form of Tissue Factor (TF), the trigger of blood coagulation whose expression levels are heightened in several forms of solid cancer, including pancreatic ductal adenocarcinoma (PDAC). asTF binds to ß1 integrins on PDAC cells, whereby it promotes tumor growth, metastatic spread, and monocyte recruitment to the stroma. In this study, we determined if targeting asTF in PDAC would significantly impact tumor progression. We here report that a novel inhibitory anti-asTF monoclonal antibody curtails experimental PDAC progression. Moreover, we show that tumor-derived asTF is able to promote PDAC primary growth and spread during early as well as later stages of the disease. This raises the likelihood that asTF may comprise a viable target in early- and late-stage PDAC. In addition, we show that TF expressed by host cells plays a significant role in PDAC spread. Together, our data demonstrate that targeting asTF in PDAC is a novel strategy to stem PDAC progression and spread.

Low thrombogenicity of calcified atherosclerotic plaques is associated with bone morphogenetic protein-2-dependent inhibition of tissue factor expression.

Morphology of atherosclerotic plaque is a major determinant of plaque thrombogenicity. Calcified atherosclerotic lesions are less prone to thrombosis and contain less tissue factor (TF) than lipid-rich plaques. Although bone morphogenetic protein (BMP)-2 is a known mediator of vascular calcification, the role of BMP-2 in the regulation of plaque thrombogenicity has not been established. We hypothesized that the expression of BMP-2 within highly calcified atherosclerotic plaques inhibits TF expression and reduces thrombogenicity of calcified lesions. In the present study, we measured levels of TF and BMP-2 in human calcified and lipid-rich carotid plaques and studied the effects of BMP-2 on TF expression in human monocytes in vitro. Quantitative immunohistochemical analysis of endarterectomy specimens for TF and BMP-2 revealed that calcified plaques contained nearly three-times less TF antigen than lipid-rich ones. In contrast, calcified plaques expressed two-times more BMP-2 antigen than lipid-rich lesions. BMP-2 markedly decreased protein expression and surface redistribution of TF in activated human monocytes in vitro. BMP-2-mediated inhibition of TF expression in monocytes/macrophages could contribute to reduced thrombogenicity of calcified atherosclerotic plaques.