Choosing a Mouse Model of Venous Thrombosis.

Murine models are widely used valuable tools to study deep vein thrombosis. Leading experts in venous thrombosis research came together through the American Venous Forum to develop a consensus on maximizing the utility and application of available mouse models of venous thrombosis. In this work, we provide an algorithm for model selection, with discussion of the advantages, disadvantages, and applications of the main mouse models of venous thrombosis. Additionally, we provide a detailed surgical description of the models with guidelines to validate surgical technique.

Collateral vein dynamics in mouse models of venous thrombosis: Pathways consistent with humans.

INTRODUCTION: Prolific collateralization in the venous system has been associated with more severe disease. However, there is a scarcity of information on venogenesis and collateral vessel progression over time. Further, little is understood regarding the relevance of the most common preclinical model-the mouse-for studying venous collateralization. The purpose of this work was to non-invasively and quantitatively characterize collateral vein development and progression in two murine models of deep vein thrombosis using magnetic resonance imaging (MRI). METHODS: Venous thrombosis (VT) was induced in 12-14-week-old male C57BL/6 mice using either the inferior vena cava (IVC) ligation model (n = 5) or the electrolytic IVC model (n = 5). Magnetic Resonance Imaging (MRI) methods optimized for small venous imaging were used on days 2, 6, 14, and 21 following venous thrombosis induction to quantify collateral development and thrombus volume. RESULTS: Collateral veins ~150-200 µm in diameter could be tracked in three dimensions. Collateral pathways were influenced by pre-existing anatomy; mice with bilateral IVC branches showed a predominant superficial collateral pathway (superficial and internal epigastric veins), whereas mice with no lateral branches exhibited a strong intermediate collateral pathway (gonadal and periureteric veins) and were less likely to develop ascending lumbar collaterals. The degree of venogenesis showed a positive correlation with thrombus volume in both models (combined R2 = 0.64, p < 0.0001). CONCLUSIONS: Venous collateral pathways in C57BL/6 mice are consistent with those described in humans. Collateral pathways are influenced by pre-existing anatomy, and the degree of collateralization correlates with thrombus volume.

Choosing a mouse model of venous thrombosis: a consensus assessment of utility and application.

Murine models are widely used valuable tools to study deep vein thrombosis (VT). Leading experts in VT research came together through the American Venous Forum to develop a consensus on maximizing the utility and application of available mouse models of VT. In this work, we provide an algorithm for model selection, with discussion of the advantages, disadvantages, and applications of the main mouse models of VT. Additionally, we provide a detailed surgical description of the models with guidelines to validate surgical technique.

Adenosine receptor agonism protects against NETosis and thrombosis in antiphospholipid syndrome.

Potentiation of neutrophil extracellular trap (NET) release is one mechanism by which antiphospholipid antibodies (aPL Abs) effect thrombotic events in patients with antiphospholipid syndrome (APS). Surface adenosine receptors trigger cyclic AMP (cAMP) formation in neutrophils, and this mechanism has been proposed to regulate NETosis in some contexts. Here we report that selective agonism of the adenosine A2A receptor (CGS21680) suppresses aPL Ab-mediated NETosis in protein kinase A-dependent fashion. CGS21680 also reduces thrombosis in the inferior vena cavae of both control mice and mice administered aPL Abs. The antithrombotic medication dipyridamole is known to potentiate adenosine signaling by increasing extracellular concentrations of adenosine and interfering with the breakdown of cAMP. Like CGS21680, dipyridamole suppresses aPL Ab-mediated NETosis via the adenosine A2A receptor and mitigates venous thrombosis in mice. In summary, these data suggest an anti-inflammatory therapeutic paradigm in APS, which may extend to thrombotic disease in the general population.

Update on the electrolytic IVC model for pre-clinical studies of venous thrombosis.

BACKGROUND: The electrolytic inferior vena cava model (EIM) is a murine venous thrombosis (VT) model that produces a non-occlusive thrombus. The thrombus forms in the direction of blood flow, as observed in patients. The EIM is valuable for investigations of therapeutics due to the presence of continuous blood flow. However, the equipment used to induce thrombosis in the original model description was expensive and has since been discontinued. Further, the fibrinolytic system had not been previously studied in the EIM. OBJECTIVES: We aimed to provide an equipment alternative. Additionally, we further characterized the model through mapping the current and time dependency of thrombus resolution dynamics, and investigated the fibrinolytic system from acute to chronic VT. RESULTS: A voltage to current converter powered by a direct current power supply was constructed and validated, providing an added benefit of significantly reducing costs. The current and time dependency of thrombus volume dynamics was assessed by MRI, demonstrating the flexibility of the EIM to investigate both pro-thrombotic and anti-thrombotic conditions. Additionally, the fibrinolytic system was characterized in EIM. Centripetal distribution of plasminogen was observed over time, with peak staining at day 6 post thrombus induction. Both active circulating plasminogen activator inhibitor-1 (PAI-1) and vein wall gene expression of PAI-1 peaked at day 2, coinciding with a relative decrease in tissue plasminogen activator and urokinase plasminogen activator. CONCLUSIONS: The EIM is a valuable model of VT that can now be performed at low cost and may be beneficial in investigations of the fibrinolytic system.

In vivo characterization of the murine venous system before and during dobutamine stimulation: implications for preclinical models of venous disease.

Although widely used as a preclinical model for studying venous diseases, there is a scarcity of in vivo characterizations of the naïve murine venous system. Additionally, previous studies on naïve veins (ex vivo) have not included the influence of surrounding structures and biomechanical forces. Using MRI, we noninvasively quantified the cross-sectional area, cyclic strain, and circularity of the venous system in young and old, male and female C57BL/6 mice. We investigated the most common venous locations used to perform venous disease research: the common jugular vein, suprarenal inferior vena cava (IVC), infrarenal IVC, common iliac vein, and common femoral vein. Our results elucidate age-dependent changes in venous cross-sectional area, which varied by location. Maximum cyclic strain, a parameter of lumen expansion, showed 10% change across the cardiac cycle, approximately half the magnitude of arteries. Veins demonstrated noncircular shapes, particularly in the core vasculature. The cardiovascular stressor dobutamine had only a small impact on the venous system. Also, our data demonstrate that the peripheral veins tend to decrease in cross-sectional area and circularity with age. Conversely, the IVC tends to increase in size and circularity with age, with males exhibiting larger variability in response to dobutamine compared to females. This work provides a foundation for drawing age and sex comparisons in disease models, and represents the first in vivo characterization of the murine venous system at rest and during the application of a pharmacological exercise surrogate.