Neutrophil extracellular traps form predominantly during the organizing stage of human venous thromboembolism development

Abstract

Background A growing health problem, venous thromboembolism (VTE), including pulmonary embolism (PE) and deep vein thrombosis (DVT), requires refined diagnostic and therapeutic approaches. Neutrophils contribute to thrombus initiation and development in experimental DVT. Recent animal studies recognized neutrophil extracellular traps (NETs) as an important scaffold supporting thrombus stability. However, the hypothesis that human venous thrombi involve NETs has not undergone rigorous testing. Objective To explore the cellular composition and the presence of NETs within human venous thrombi at different stages of development. Patients and Methods We examined sixteen thrombi obtained from 11 patients during surgery or at autopsy using histomorphological, immunohistochemical and immunofluorescence analyses. Results We classified thrombus regions as unorganized, organizing, and organized according to their morphological characteristics. We then evaluated them focusing on neutrophil and platelet deposition as well as micro-vascularization of the thrombus body. We observed evidence of NET accumulation, including the presence of citrullinated histone H3 (H3Cit)-positive cells. NETs, defined as extracellular diffuse H3Cit areas associated with myeloperoxidase and DNA, localized predominantly during the phase of organization in human venous thrombi. Conclusions NETs are present in organizing thrombi in patients with VTE. They are associated with thrombus maturation in humans. Dissolution of NETs might thus facilitate thrombolysis. This finding provides new insights into the clinical development and pathology of thrombosis and provides new perspectives for therapeutic advances.

Role of platelets, neutrophils, and factor XII in spontaneous venous thrombosis in mice

“…1 The role of neutrophils became evident by using an antibody-mediated depletion strategy identical to the method used in this study (depletion of Ly6G-positive cells). For the electrolytic inferior vena cava model of VT in which the vena cava is directly activated by an electric current thus causing endothelial damage, it was demonstrated that vein wall neutrophils were the most common cell type present in acute VT. 20 Moreover, neutrophils and NETs have also been identified in human VT. 21,22 When VT followed silencing of anticoagulant genes, Ly6G-positive neutrophils were abundantly present within the thrombi, seemingly recruited and aligned to the fibrin layers, which is consistent with previous observations. 1,2 However, in our model, neutrophils were not rate limiting in thrombus formation.…”

Beyond Virchow’s Triad: Does cardiovascular inflammation explain the recurrent nature of venous thromboembolism?

“…Staining of human acute PE specimens for CD42b, a platelet surface membrane glycoprotein, has demonstrated a high concentration of platelets in venous thrombus. 15 This observation challenges a long-held belief that platelets play little role in the pathogenesis of VTE.…”

Is Venous Thromboembolism a Chronic Inflammatory Disease?

“…Furthermore, polymorphisms in genes encoding factor VII, interleukin-1␤ (IL-1␤), and IL-10 modulate the risk of idiopathic VTE (11 ). The presence of neutrophils and neutrophil extracellular traps in human venous thrombus further highlight the importance of inflammation to the development of VTE (12 ).…”