von Willebrand Factor Is a Critical Mediator of Deep Vein Thrombosis in a Mouse Model of Diet-Induced Obesity.

OBJECTIVE: Obesity is characterized by chronic low-grade inflammation and consequentially a hypercoagulable state, associating with an increased incidence of venous thromboembolism. Increased VWF (von Willebrand factor) plasma concentration and procoagulant function are independent risk factors for venous thromboembolism and are elevated in obese patients. Here, we explore the pathobiological role of VWF in obesity-associated venous thrombosis using murine models. Approach and Results: We first showed that diet-induced obese mice have increased VWF plasma levels and FVIII (factor VIII) activity compared with littermate controls. Elevated VWF levels appeared to be because of both increased synthesis and impaired clearance. Diet-induced obesity-associated venous thrombosis was assessed using the inferior vena cava-stenosis model of deep vein thrombosis. Diet-induced obese mice developed larger venous thrombi that were rich in VWF, erythrocytes, and leukocytes. Administering a polyclonal anti-VWF antibody or an anti-VWF A1 domain nanobody was protective against obesity-mediated thrombogenicity. Delayed administration (3 hours post-inferior vena cava stenosis) similarly reduced thrombus weight in diet-induced obese mice. CONCLUSIONS: This study demonstrates the critical role of VWF in the complex, thrombo-inflammatory state of obesity. It adds to the growing rationale for targeting VWF-specific interactions in thrombotic disease.

The mechanistic and structural role of von Willebrand factor in endotoxemia-enhanced deep vein thrombosis in mice.

BACKGROUND: Although the concept of immunothrombosis has established a link between inflammation and thrombosis, the role of inflammation in the pathogenesis of deep vein thrombosis remains to be fully elucidated. Further, although various constituents of venous thrombi have been identified, their localizations and cellular and molecular interactions are yet to be combined in a single, multiplexed analysis. OBJECTIVES: The objective of this study was to investigate the role of the von Willebrand factor (VWF) in inflammation-associated venous thrombosis. We also performed a proof-of-concept study of imaging mass cytometry to quantitatively and simultaneously analyze the localizations and interactions of 10 venous thrombus constituents. METHODS: We combined the murine inferior vena cava stenosis model of deep vein thrombosis with the lipopolysaccharide model of endotoxemia. We also performed a proof-of-concept study of imaging mass cytometry to assess the feasibility of this approach in analyzing the structural composition of thrombi. RESULTS: We found that lipopolysaccharide-treated mice had significantly higher incidences of venous thrombosis, an effect that was mitigated when VWF was inhibited using inhibitory αVWF antibodies. Our detailed structural analysis also showed that most thrombus components are localized in the white thrombus regardless of endotoxemia. Moreover, although endotoxemia modulated the relative representation and interactions of VWF with other thrombus constituents, the scaffolding network, comprised VWF, fibrin, and neutrophil extracellular traps, remained largely unaffected. CONCLUSIONS: We observe a key role for VWF in the pathogenesis of inflammation-associated venous thrombosis while providing a more comprehensive insight into the molecular interactions that constitute the architecture of venous thrombi.

Stabilin-2 deficiency increases thrombotic burden and alters the composition of venous thrombi in a mouse model.

BACKGROUND: Stabilin-2 is an endocytic scavenger receptor that mediates the clearance of glycosaminoglycans, phosphatidylserine-expressing cells, and the von Willebrand factor-factor VIII (FVIII) complex. In a genome-wide screening study, pathogenic loss-of-function variants in the human STAB2 gene associated with an increased incidence of unprovoked venous thromboembolism (VTE). However, the specific mechanism(s) by which stabilin-2 deficiency influences the pathogenesis of VTE is unknown. OBJECTIVES: The aim of this study was to assess the influence of stabilin-2 on deep vein thrombosis (DVT) and to characterize the underlying prothrombotic phenotype of stabilin-2 deficiency in a mouse model. METHODS: DVT was induced using the inferior vena cava (IVC) stenosis model in two independent cohorts (littermates and non-littermates) of wild-type (Stab2+/+ ) and stabilin-2 (Stab2-/- )-deficient mice. Thrombus structure and contents were quantified by immunohistochemistry. Plasma procoagulant activity was assessed and complete blood counts were performed. RESULTS: Incidence of thrombus formation was not altered between Stab2+/+ and Stab2-/- mice. When thrombi were formed, Stab2-/- mice developed significantly larger thrombi than Stab2+/+ controls. Thrombi from Stab2-/- mice contained significantly more leukocytes and citrullinated histone H3 than Stab2+/+ thrombi. Stab2-/- mice had increased FVIII activity. Circulating levels of monocytes and granulocytes were significantly elevated in Stab2-/- mice, and Stab2-/- mice had elevated plasma cell-free DNA 24 hours post-IVC stenosis compared to their Stab2+/+ counterparts. CONCLUSIONS: These data suggest that stabilin-2 deficiency associates with a prothrombotic phenotype involving elevated levels of neutrophil extracellular trap-releasing leukocytes coupled with endogenous procoagulant activity, resulting in larger and qualitatively distinct venous thrombi.