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

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.

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.

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.

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.

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.