Platelet-neutrophil interactions are important for innate immunity, but also contribute to the pathogenesis of deep vein thrombosis, myocardial infarction and stroke. Here we report that, under flow, von Willebrand factor/glycoprotein Ibα-dependent platelet ‘priming’ induces integrin α_IIbβ₃activation that, in turn, mediates neutrophil and T-cell binding. Binding of platelet α_IIbβ₃to SLC44A2 on neutrophils leads to mechanosensitive-dependent production of highly prothrombotic neutrophil extracellular traps. A polymorphism inSLC44A2(rs2288904-A) present in 22% of the population causes an R154Q substitution in an extracellular loop of SLC44A2 that is protective against venous thrombosis results in severely impaired binding to both activated α_IIbβ₃and VWF-primed platelets. This was confirmed using neutrophils homozygous for theSLC44A2R154Q polymorphism. Taken together, these data reveal a previously unreported mode of platelet-neutrophil crosstalk, mechanosensitive NET production, and provide mechanistic insight into the protective effect of theSLC44A2rs2288904-A polymorphism in venous thrombosis.

Platelets are essential for the formation of a haemostatic plug to prevent bleeding, while neutrophils are the guardians of our immune defences against invading pathogens. The interplay between platelets and innate immunity, and subsequent triggering of the activation of coagulation is part of the host system to prevent systemic spread of pathogen in the blood stream. Aberrant immunothrombosis and excessive inflammation can however, contribute to the thrombotic burden observed in many cardiovascular diseases. In this review, we highlight how platelets and neutrophils interact with each other and how their crosstalk is central to both arterial and venous thrombosis and in COVID-19. While targeting platelets and coagulation enables efficient antithrombotic treatments, they are often accompanied with a bleeding risk. We also discuss how novel approaches to reduce platelet-mediated recruitment of neutrophils could represent promising therapies to treat thrombosis without affecting haemostasis.

Management of recurrent gastrointestinal (GI) bleeding is a clinical unmet need for patients with von Willebrand disease (VWD) and is linked to the presence of gut vascular malformations (angiodysplasia). We previously demonstrated that von Willebrand factor (VWF) regulates angiogenesis and vascular integrity. VWF controls the storage of the angiogenesis regulator angiopoietin-2 (Angpt-2) in endothelial cells (EC), suggesting a candidate for the genesis of angiodysplasia; however, no direct evidence of the role of Angpt-2 in VWF-dependent angiogenesis is available. Using VWF-deficient human umbilical vein EC (HUVEC) and endothelial colony-forming cells (ECFCs) from patients with severe VWD, we found that loss of VWF resulted in increased Angpt-2 expression through the positive feedback loop Angpt-2–Tie-2–Akt–FOXO1–Angpt-2. In the gut of VWF-deficient mice, Angpt-2 expression was increased, whereas Angpt-1 expression was decreased, suggesting that VWF regulates the Angpt/Tie2 balance in the gut. Moreover, the intestinal vasculature in the jejunum of VWF-deficient mice appeared abnormal, with hypersprouting and lumen formation defects. The findings reveal VWF-deficient mice as a model to study gut angiodysplasia. We investigated sprouting angiogenesis in vitro using a fibrin bead assay and found increased sprouting in VWF-deficient EC. We developed a 3-dimensional microfluidic model of angiogenesis and found that ECFCs from patients with severe VWD exhibit defective remodeling and abnormal lumen formation, reminiscent of the defects in the gut of VWF-deficient mice. Importantly, inhibition of Angpt-2 reduced sprouting in VWF-deficient HUVEC and normalized vascular remodeling in VWD-ECFCs, suggesting that Angpt-2 inhibitors may be effective in patients with VWD with GI bleeding and angiodysplasia.