Opinions on mouse models of thrombosis

Hypoxia and HIF activation as a possible link between sepsis and thrombosis

Risk factors for thrombosis include hypoxia and sepsis, but the mechanisms that control sepsis-induced thrombus formation are incompletely understood. A recent article published in Thrombosis Journal: (i) reviews the role of endothelial cells in the pathogenesis of sepsis-associated microthrombosis; (ii) describes a novel ‘two-path unifying theory’ of hemostatic discorders; and (iii) refers to hypoxia as a consequence of microthrombus formation in sepsis patients. The current article adds to this review by describing how sepsis and thrombus formation could be linked through hypoxia and activation of hypoxia-inducible transcription factors (HIFs). In other words, hypoxia and HIF activation may be a cause as well as a consequence of thrombosis in sepsis patients. While microthrombosis reduces microvascular blood flow causing local hypoxia and tissue ischemia, sepsis-induced increases in HIF1 activation could conversely increase the expression of coagulant factors and integrins that promote thrombus formation, and stimulate the formation of pro-thrombotic neutrophil extracellular traps. A better understanding of the role of cell-specific HIFs in thrombus formation could lead to the development of novel prophylactic therapies for individuals at risk of thrombosis.

Can thrombus age guide thrombolytic therapy?

Venous thrombosis (VT) is a common yet complex clinical condition that has shown minimal alteration in clinical management for decades. It is well known that thrombus evolves structurally over time, with complex changes resulting from the interplay between coagulation factors, cytokines, leukocytes and a myriad of other factors. Our current treatment options are most effective in the acute thrombus, which is composed predominantly of a loose mesh of fibrin and red blood cells (RBCs), making current anticoagulation therapies and thrombolytics quite effective in treatment. Later stages of thrombus are more cellular containing leukocytes, and develop a fibrotic collagenous framework that is more resistant to our current treatments. Understanding the biology of an evolving thrombus will allow us to tailor our treatment and optimize outcomes, as well as focus on novel therapies for the treatment of chronic thrombus. Given the morbidity and mortality of both post thrombotic syndrome (PTS) in patients with deep VT, as well as chronic thromboembolic pulmonary hypertension (CTEPH) in patients with pulmonary embolism (PE), new and innovative therapies must continue to be explored to help prevent these potentially devastating conditions.

Close concordance between pulmonary angiography and pathology in a canine model with chronic pulmonary thromboembolism and pathological mechanisms after lung ischemia reperfusion injury

To investigate the pulmonary angiography and pathology in a canine model with chronic pulmonary thromboembolism (PTE). The cylindrical blood clots were selectively introduced into the left (n = 10) or right (n = 20) lower pulmonary arteries of dogs. Pulmonary arteriography (PA) was performed before or after embolization. The values after embolization and baseline of mean pulmonary arterial pressure, pulmonary vascular resistance, cardiac output had changed. After 1 or 2 weeks' embolization, local PA demonstrated the abrupt cut-off perfusion defects or webs, bands, and abrupt vascular narrowing. 2 weeks after embolization, the pathology showed that the fibrin networks of the thrombi had multiple recanalization channels, and pulmonary artery had the concentric, lamellar (onion-like) intimal hyperplasia, multilayered, irregular arrangements of endothelial cells, and the infiltration of inflammatory cells. After embolectomy-mediated reperfusion, 2 weeks' subgroup showed destroyed and incomplete alveolar structures, and a large number of exudative cells, primarily neutrophils, and exudate. There close concordance between pulmonary angiography and pathology in a canine model with chronic PTE. The LIRI mechanisms after embolectomy-mediated reperfusion involve the destroyed, incomplete alveolar structures, and infiltration of inflammatory cells, primarily neutrophils.

Mouse models of deep vein thrombosis

The pathogenesis of venous thromboembolism (VTE) is still not completely understood. Experimental animals in which human deep vein thrombosis can be modeled are useful tools to investigate the pathogenesis of VTE. Besides the availability of transgenic and genetically modified mice, the use of high frequency ultrasound and intravital microscopy plays an important role in identifying thrombotic processes in mouse models. In this article, an overview about the application of various new technologies and existing mouse models is provided, and the impact of venous side branches on deep vein thrombosis in the mouse model is discussed.