Science Platforms

Translational / Basic Science Research

Knowledge gaps exist on causal mechanisms for venous thromboembolism (VTE) and, in particular, chronic complications of VTE. The translational/basic science platform is primarily designed to provide CanVECTOR’s basic scientists with translational research opportunities by providing samples that permit exploration of “bench to bedside and back” questions. By piggy-backing translational research questions and biomarker sub-studies onto our current and future clinical studies, the Network will provide a unique, efficient and cost-effective opportunity to test novel hypotheses on the pathogenesis of VTE and may thereby identify new targets for preventing VTE or its complications.

The Team

Platform Co-Leads

Jeffrey Weitz (Hamilton, ON)
Edward Conway (Vancouver, BC)

Working Group

Peter Gross (Hamilton, ON)
Patricia Liaw (Hamilton, ON)

The Projects

1. Explore the roles of the contact and complement systems in the pathogenesis of venous thromboembolism and complications

Study Aims: To test the hypothesis that lowering factor XI levels reduces thrombin generation and complement activation.

Population: Pre- and post-operative plasma samples from knee arthroplasty patients who were randomized to the factor XI ASO or enoxaparin.

Study Timeline: 2016-2017 (study being conducted at McMaster, Weitz lab)

2. Examine the role of inflammation in the post-thrombotic syndrome

Study Aims: To examine the hypothesis that chronic inflammation contributes to the post-thrombotic syndrome (PTS) and determine whether there is more complement activation and histidine-rich glycoprotein (HRG) levels are lower in patients with versus without PTS.

Population: Samples from patients with a first, symptomatic, proximal DVT who participated in the SOX trial.

Study Timeline: 2016-2017 (study being conducted at UBC Centre for Blood Research, Conway lab)

3. Studies of cell-free DNA, thrombin generation, and fibrinolysis in patients with unprovoked VTE

Principal Investigator: Patricia Liaw, PhD

Study Summary

Venous thromboembolism (VTE) is the third leading cause of cardiovascular mortality after myocardial infarction and stroke.  In recent years, neutrophils have been shown to be indispensable for the initiation and propagation of VTE.  Neutrophils contribute to VTE through the delivery of neutrophil extracellular traps (NETs), consisting of cell-free DNA (cfDNA), histones, and neutrophil granular enzymes.  We have previously shown that cfDNA contributes to the prothrombotic potential of NETs by triggering the intrinsic pathway of blood coagulation and by inhibiting plasmin-mediated fibrin degradation.  This study explores the hypothesis that cfDNA is not only a predictor of recurrent VTE in patients with unprovoked VTE, but also contributes to the pathogenesis of VTE by promoting blood coagulation and by inhibiting fibrinolysis.  This is a translational study in collaboration with Dr. Clive Kearon which will utilize plasma samples from the DODS study (D-dimer Optimal Duration Study). 

4. FXIII and EACA increase thrombus stability and decrease pulmonary embolism in an in vivo mouse model of Venous Thromboembolism, but EACA increases thrombus size.

Title: FXIII and EACA increase thrombus stability and decrease pulmonary embolism in an in vivo mouse model of Venous Thromboembolism, but EACA increases thrombus size.

Authors: Shana A. Shaya, Jeff I. Weitz, Peter L. Gross

Affiliation: Thrombosis and Atherosclerosis Research Institute, Department of Medicine, McMaster University.

Background: Whether a patient presents with deep vein thrombosis (DVT) or pulmonary embolism (PE) varies based on clinical factors. The biological mechanisms that determine DVT stability in the progression of DVT to PE are not known.

Anticoagulation is contraindicated in patients presenting with DVT and severe bleeding. Inferior vena cava filters are used instead but associated with high morbidity. Are there alternative treatments that can stabilize clots, minimize embolization and PE burden, without causing further bleeding? We have previously described a mouse model of venous thromboembolism (VTE) that can assess the thrombus size, quantify embolic events that break off the thrombus, and correlate this to the resulting PE burden, and shown the requirement of thrombin-mediated factor XIII (FXIII) activation in this model. 

Aim: Determine the effects of epsilon aminocaproic acid (EACA) and FXIII on thrombus stability and PE burden.

Methods: Platelets were fluorescently labelled using CD41 Fab fragments conjugated to an Alexa Fluor 488. The femoral vein of C57BL/6 female mice was subjected to ferric chloride injury to initiate thrombus formation. Treatment with saline, dalteparin (0.2 IU/g, dabigatran (33 mg/g), EACA (1 mg/kg), or FXIII (1mg/kg) was administered 12 minutes after thrombus formation. Intravital videomicroscopy recorded the thrombus sizes (TSs) and embolic events (EEs) leaving the thrombus for 2 hours. Lungs were harvested, sectioned and stained for the presence of PE.

Results: EACA increases TS significantly and therefore would not be a feasible treatment as it will increase DVT size. FXIII marginally increased TS. Treatment with FXIII decreases total and large EEs in saline, dalteparin or dabigatran-treated mice, similar to EACA-treated mice. The number of emboli per lung slice was reduced after treatment with FXIII and EACA compared to non-treated mice. PE burden was not significantly different between FXIII anticoagulated mice or EACA-treated mice. The large EEs correlate positively with PE burden.

Conclusion: Attenuating fibrinolysis with EACA, but not FXIII, increases TS, but both increase DVT stability and decrease PE burden. This suggests that administration of FXIII is a better treatment option for DVT patients who are bleeding than EACA, since EACA may increase DVT size.

Acknowledgment:  We thank Canvector for partial funding of this study