The histone methyltransferase MLL1/KMT2A in monocytes drives coronavirus-associated coagulopathy and inflammation.

Coronavirus-associated coagulopathy (CAC) is a morbid and lethal sequela of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. CAC results from a perturbed balance between coagulation and fibrinolysis and occurs in conjunction with exaggerated activation of monocytes/macrophages (MO/Mφs), and the mechanisms that collectively govern this phenotype seen in CAC remain unclear. Here, using experimental models that use the murine betacoronavirus MHVA59, a well-established model of SARS-CoV-2 infection, we identify that the histone methyltransferase mixed lineage leukemia 1 (MLL1/KMT2A) is an important regulator of MO/Mφ expression of procoagulant and profibrinolytic factors such as tissue factor (F3; TF), urokinase (PLAU), and urokinase receptor (PLAUR) (herein, "coagulopathy-related factors") in noninfected and infected cells. We show that MLL1 concurrently promotes the expression of the proinflammatory cytokines while suppressing the expression of interferon alfa (IFN-α), a well-known inducer of TF and PLAUR. Using in vitro models, we identify MLL1-dependent NF-κB/RelA-mediated transcription of these coagulation-related factors and identify a context-dependent, MLL1-independent role for RelA in the expression of these factors in vivo. As functional correlates for these findings, we demonstrate that the inflammatory, procoagulant, and profibrinolytic phenotypes seen in vivo after coronavirus infection were MLL1-dependent despite blunted Ifna induction in MO/Mφs. Finally, in an analysis of SARS-CoV-2 positive human samples, we identify differential upregulation of MLL1 and coagulopathy-related factor expression and activity in CD14+ MO/Mφs relative to noninfected and healthy controls. We also observed elevated plasma PLAU and TF activity in COVID-positive samples. Collectively, these findings highlight an important role for MO/Mφ MLL1 in promoting CAC and inflammation.

Low to Moderate Risk Non-orthopedic Surgical Patients Do Not Benefit From VTE Chemoprophylaxis.

This retrospective cohort study analyzes venous thromboembolism (VTE) incidence, morbidity, and mortality amongst postsurgical patients with and without VTE chemoprophylaxis within a quality collaborative. Postoperative thromboprophylaxis was broadly applied, yet was associated with no decrease in VTE, without affecting transfusion or mortality. Predictors of breakthrough VTE development despite evidence-based thromboprophylaxis are identified. OBJECTIVE: We hypothesized that a high rate of prescription of VTE chemoprophylaxis would be associated with decreased VTE incidence and mortality. SUMMARY BACKGROUND DATA: Recommendations for VTE prevention in surgical patients include chemoprophylaxis based upon preoperative risk stratification. METHODS: This retrospective cohort study analyzed VTE incidence, morbidity, and mortality amongst postsurgical patients with and without VTE chemoprophylaxis between April 2013 and September 2017 from 63 hospitals within the Michigan Surgical Quality Collaborative. A VTE risk assessment survey was distributed to providers. Bivariate and multivariate comparisons were made, as well as using propensity score matched cohorts to determine if VTE chemoprophylaxis was associated with decreased VTE events. Hospitals were compared using risk-reliability adjusted VTE prophylaxis and postoperative VTE event rates. RESULTS: Within the registry, 80% of practitioners reported performing formal VTE risk assessment. Amongst 32,856 operations, there were 480 (1.46%) postoperative VTE, and an overall mortality of 609 (1.85%) patients. Using a propensity matched cohort, we found that rates of VTE were similar in those receiving unfractionated heparin or low molecular weight heparin compared to those not receiving chemoprophylaxis (1.22 vs 1.13%, P = 0.57). When stratified further by VTE risk scoring, even the highest risk patients did not have an associated lower VTE rate (3.68 vs 4.22% P = 0.092). Postoperative transfusion (8.28 vs 7.50%, P = 0.057) and mortality (2.00% vs 1.62%, P = 0.064) rates were similar amongst those receiving and those not receiving chemoprophylaxis. No correlation was found between postoperative VTE chemoprophylaxis application and hospital specific risk adjusted postoperative VTE rates. CONCLUSIONS: In modern day postsurgical care, VTE remains a significant occurrence, despite wide adoption of VTE risk assessment. Although postoperative VTE chemoprophylaxis was broadly applied, after adjusting for confounders, no reduction in VTE was observed in at-risk surgical patients.

Choosing a Mouse Model of Venous Thrombosis.

Murine models are widely used valuable tools to study deep vein thrombosis. Leading experts in venous thrombosis research came together through the American Venous Forum to develop a consensus on maximizing the utility and application of available mouse models of venous thrombosis. In this work, we provide an algorithm for model selection, with discussion of the advantages, disadvantages, and applications of the main mouse models of venous thrombosis. Additionally, we provide a detailed surgical description of the models with guidelines to validate surgical technique.

Tuning the Thromboinflammatory Response to Venous Flow Interruption by the Ectonucleotidase CD39.

Objective- Leukocyte flux contributes to thrombus formation in deep veins under pathological conditions, but mechanisms that inhibit venous thrombosis are incompletely understood. Ectonucleotide di(tri)phosphohydrolase 1 ( ENTPD1 or Cd39), an ectoenzyme that catabolizes extracellular adenine nucleotides, is embedded on the surface of endothelial cells and leukocytes. We hypothesized that under venous stasis conditions, CD39 regulates inflammation at the vein:blood interface in a murine model of deep vein thrombosis. Approach and Results- CD39-null mice developed significantly larger venous thrombi under venous stasis, with more leukocyte recruitment compared with wild-type mice. Gene expression profiling of wild-type and Cd39-null mice revealed 76 differentially expressed inflammatory genes that were significantly upregulated in Cd39-deleted mice after venous thrombosis, and validation experiments confirmed high expression of several key inflammatory mediators. P-selectin, known to have proximal involvement in venous inflammatory and thrombotic events, was upregulated in Cd39-null mice. Inferior vena caval ligation resulted in thrombosis and a corresponding increase in both P-selectin and VWF (von Willebrand Factor) levels which were strikingly higher in mice lacking the Cd39 gene. These mice also manifest an increase in circulating platelet-leukocyte heteroaggregates suggesting heterotypic crosstalk between coagulation and inflammatory systems, which is amplified in the absence of CD39. Conclusions- These data suggest that CD39 mitigates the venous thromboinflammatory response to flow interruption.

Apixaban Versus Warfarin for Mechanical Heart Valve Thromboprophylaxis in a Swine Aortic Heterotopic Valve Model.

OBJECTIVE: Warfarin is the current standard for oral anticoagulation therapy in patients with mechanical heart valves, yet optimal therapy to maximize anticoagulation and minimize bleeding complications requires routine coagulation monitoring, possible dietary restrictions, and drug interaction monitoring. As alternatives to warfarin, oral direct acting factor Xa inhibitors are currently approved for the prophylaxis and treatment of venous thromboembolism and reduction of stroke and systemic embolization. However, no in vivo preclinical or clinical studies have been performed directly comparing oral factor Xa inhibitors such as apixaban to warfarin, the current standard of therapy. APPROACH AND RESULTS: A well-documented heterotopic aortic valve porcine model was used to test the hypothesis that apixaban has comparable efficacy to warfarin for thromboprophylaxis of mechanical heart valves. Sixteen swine were implanted with a bileaflet mechanical aortic valve that bypassed the ligated descending thoracic aorta. Animals were randomized to 4 groups: control (no anticoagulation; n=4), apixaban oral 1 mg/kg twice a day (n=5), warfarin oral 0.04 to 0.08 mg/kg daily (international normalized ratio 2-3; n=3), and apixaban infusion (n=4). Postmortem valve thrombus was measured 30 days post-surgery for control-oral groups and 14 days post-surgery for the apixaban infusion group. Control thrombus weight (mean) was significantly different (1422.9 mg) compared with apixaban oral (357.5 mg), warfarin (247.1 mg), and apixiban 14-day infusion (61.1 mg; P<0.05). CONCLUSIONS: Apixaban is a promising candidate and may be a useful alternative to warfarin for thromboprophylaxis of mechanical heart valves. Unlike warfarin, no adverse bleeding events were observed in any apixaban groups.

Deep Vein Thrombosis Exhibits Characteristic Serum and Vein Wall Metabolic Phenotypes in the Inferior Vena Cava Ligation Mouse Model.

OBJECTIVES: Deep vein thrombosis (DVT) is a major health problem, responsible for significant morbidity and mortality. The identification of a simple and effective diagnostic biomarker of DVT remains a challenge. Metabolomics have recently emerged as a new powerful scientific tool to characterise metabolic phenotypes of complex diseases and investigate small molecules in biofluids. The aim of the study was to identify the blood and vein wall metabolomic signature of DVT in a murine experimental model. METHODS: An established inferior vena cava ligation mouse model of DVT (n=10) was used and compared with sham surgery controls (n=10). Comprehensive untargeted metabolic profiling of serum and vein wall extracts was undertaken using liquid chromatography coupled mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy. RESULTS: Multivariate and univariate statistical analysis demonstrated a differential metabolic profile when comparing DVT mice and control animals. Serum from DVT mice was characterised by differential concentrations of adenosine (decreased in DVT mice 9.6 fold), adenine (decreased 10.6 fold), and tricyclic acid cycle (TCA) intermediates, including citrate, succinate, and fumarate (1.5, 2.3, and 2.8 fold decreases, respectively). l-carnitine was found to be of greater abundance in the serum of DVT animals (67.0 fold change). A number of lipid moiety classes, including sphingomyelins, phosphatidylcholines, and triglycerides, were differentially abundant. Several metabolites were found in vein wall, including acetylcarnitine (increased in DVT mice 1.9 fold), adenosine (increased 2.2 fold), and ceramide (increased 2.7 fold). Correlation analysis illustrated the biochemical relationships between assigned metabolites, with the discriminatory molecules being highly correlated with each other, in both serum and vein wall. CONCLUSIONS: The present findings demonstrate that metabolic dysregulations in DVT centre on energy metabolism, sphingolipid, and adenosine metabolism, representing a DVT specific metabolite signature in a murine experimental model.

New biomarkers and imaging approaches for the diagnosis of deep venous thrombosis.

PURPOSE OF REVIEW: Symptoms suggestive of deep vein thrombosis (DVT) are extremely common in clinical practice, but unfortunately nonspecific. In both ambulatory and inpatient settings, clinicians are often tasked with evaluating these concerns. Here, we review the most recent advances in biomarkers and imaging to diagnose lower extremity DVT. RECENT FINDINGS: The modified Wells score remains the most supported clinical decision rule for risk stratifying patients. In uncomplicated patients, the D-dimer can be utilized with risk stratification to reasonably exclude lower extremity DVT in some patients. Although numerous biomarkers have been explored, soluble P-selectin has the most promise as a novel marker for DVT. Imaging will be required for many patients and ultrasound is the primary modality. Nuclear medicine techniques are under development, and computed tomography (CT) and magnetic resonance venography are reasonable alternatives in select patients. SUMMARY: D-dimer is the only clinically applied biomarker for DVT diagnosis, with soluble P-selectin a promising novel biomarker. Recent studies have identified several other potential biomarkers. Ultrasound remains the imaging modality of choice, but CT, MRI, or nuclear medicine tests can be considered in select scenarios.

The role of galectin-3 and galectin-3-binding protein in venous thrombosis.

Galectin-3-binding protein (gal3bp) and its receptor/ligand, galectin-3 (gal3), are secreted proteins that initiate signaling cascades in several diseases, and recent human proteomic data suggest they may play a role in venous thrombosis (VT). We hypothesized that gal3bp and gal3 may promote VT. Using a mouse stasis model of VT, we found that gal3bp and gal3 were localized on vein wall, red blood cells, platelets, and microparticles, whereas leukocytes expressed gal3 only. Gal3 was dramatically increased during early VT and gal3bp:gal3 colocalized in the leukocyte/endothelial cell interface, where leukocytes were partially attached to the vein wall. Thrombus size correlated with elevated gal3 and interleukin-6 (IL-6) vein wall levels. Recombinant gal3 promoted VT and increased vein wall IL-6 mRNA. Although recombinant gal3 restored the VT size in gal3(-/-) mice, it had no effect on IL6(-/-) mice, suggesting that gal3:gal3bp promotes VT through IL-6. Moreover, significantly fewer activated neutrophils were present in the gal3(-/-) vein walls. In a group of human patients, elevated circulating gal3bp correlated with acute VT. In conclusion, gal3bp:gal3 play a critical role in VT, likely via IL-6 and PMN-mediated thrombotic mechanisms, and may be a potential biomarker in human VT.

Gram-Negative Pneumonia Alters Large-Vein Cell-Adhesion Molecule Profile and Potentiates Experimental Stasis Venous Thrombosis.

BACKGROUND/AIMS: Pneumonia is a significant risk factor for the development of venous thrombosis (VT). Cell-adhesion molecules (CAMs) are linked to the pathogenesis of both pneumonia and VT. We hypothesized that remote infection would confer a prothrombogenic milieu via systemic elevation of CAMs. METHODS: Lung injury was induced in wild-type (C57BL/6) mice by lung contusion or intratracheal inoculation with Klebsiella pneumoniae or saline controls. K. pneumoniae-treated mice and controls additionally underwent inferior vena cava (IVC) ligation to generate VT. RESULTS: Lung-contusion mice demonstrated no increase in E-selectin or P-selectin whereas mice infected with K. pneumoniae demonstrated increased circulating P-selectin, ICAM-1, VCAM-1 and thrombin-antithrombin (TAT) complexes. Mice with pneumonia formed VT 3 times larger than controls, demonstrated significantly more upregulation of vein-wall and systemic CAMs, and formed erythrocyte-rich thrombi. CONCLUSION: Elevated CAM expression was identified in mice with pneumonia, but not lung contusion, indicating that the type of inflammatory stimulus and the presence of infection drive the vein-wall response. Elevation of CAMs was associated with amplified VT and may represent an alternate mechanism by which to target the prevention of VT.

P-selectin inhibition therapeutically promotes thrombus resolution and prevents vein wall fibrosis better than enoxaparin and an inhibitor to von Willebrand factor.

OBJECTIVE: Aptamers are oligonucleotides targeting protein-protein interactions with pharmacokinetic profiles and activity reversal options. Although P-selectin and von Willebrand factor (vWF) have been implicated in the development of venous thrombosis (VT), no studies have directly compared aptamer efficacy with standard of care in VT. In this study, ARC5692, an anti-P-selectin aptamer, and ARC15105, an anti-vWF aptamer, were compared with low-molecular-weight heparin, enoxaparin, to test the efficacy of P-selectin or vWF inhibition in promoting thrombus resolution and preventing vein wall fibrosis, in a baboon model of VT. APPROACH AND RESULTS: Groups were as follows: treatment arm: animals received P-selectin or vWF aptamer inhibitors or enoxaparin (n=3 per group). Controls received no treatment (n=3). Prophylactic arm: animals received P-selectin inhibitor (n=4) or vWF inhibitor (n=3). Treatment arm: P-selectin-inhibitor demonstrated a significant improvement in vein recanalization by magnetic resonance venography (73% at day 21), and significantly decreased vein wall collagen, compared with all groups. Anti-P-selectin equaled enoxaparin in maintaining valve competency by ultrasound. All control animals had compromised valve competency post thrombosis. Prophylactic arm: animals receiving P-selectin and vWF inhibitors demonstrated improved vein recanalization by magnetic resonance venography versus controls (80% and 85%, respectively, at day 21). Anti-P-selectin protected iliac valve function better than anti-vWF, and both improved valve function versus controls. No adverse bleeding events were observed. CONCLUSIONS: The P-selectin inhibitor aptamer promoted iliac vein recanalization, preserved valve competency, and decreased vein wall fibrosis. The results of this work suggest that P-selectin inhibition maybe an ideal target in the treatment and prophylaxis of deep VT, warranting clinical trials.

Recanalization of the intentionally interrupted inferior vena cava.

Intentional interruption of the inferior vena cava with caval ligation and a Mobin-Uddin filter was once commonly used to prevent recurrent pulmonary emboli and was associated with significant mortality and morbidity, including a high incidence of post-thrombotic syndrome. Recanalization of an intentionally interrupted inferior vena cava has been rarely described in literature and is commonly considered futile. We describe two patients with post-thrombotic syndrome as a late complication of caval ligation and a thrombosed Mobin-Uddin filter, with significant and sustained improvement after endovascular recanalization.

Reliability of hospital readmission rates in vascular surgery.

OBJECTIVE: The Center for Medicare and Medicaid Services recently began assessing financial penalties to hospitals with high readmission rates for a narrow set of medical conditions. Because these penalties will be extended to surgical conditions in the near future, we sought to determine whether readmissions are a reliable predictor of hospital performance with vascular surgery. METHODS: We examined 4 years of national Medicare claims data from 1576 hospitals on beneficiaries undergoing three common vascular procedures: open or endovascular abdominal aortic aneurysm repair (n = 81,520) or lower extremity arterial bypass (n = 57,190). First, we divided our population into two groups on the basis of operative date (2005-2006 and 2007-2008) and generated hospital risk- and reliability-adjusted readmission rates for each time period. We evaluated reliability through the use of the "test-retest" method; highly reliable measures will show little variation in rates over time. Specifically, we evaluated the year-to-year reliability of readmissions by calculating Spearman rank correlation and weighted κ tests for readmission rates between the two time periods. RESULTS: The Spearman coefficient between 2005-2006 readmissions rankings and 2007-2008 readmissions rankings was 0.57 (P < .001) and weighted κ was 0.42 (P < .001), indicating a moderate correlation. However, only 32% of the variation in hospital readmission rates in 2007-2008 was explained by readmissions during the 2 prior years. There were major reclassifications of hospital rankings between years, with 63% of hospitals migrating among performance quintiles between 2005-2006 and 2007-2008. CONCLUSIONS: Risk-adjusted readmission rates for vascular surgery vary substantially year to year; this implies that much of the observed variation in readmission rates is either random or caused by unmeasured factors and not caused by changes in hospital quality that may be captured by administrative data.

A comparative study of altered hemodynamics in iliac vein compression syndrome.

Introduction: Iliac vein compression syndrome (IVCS) is present in over 20% of the population and is associated with left leg pain, swelling, and thrombosis. IVCS symptoms are thought to be induced by altered pelvic hemodynamics, however, there currently exists a knowledge gap on the hemodynamic differences between IVCS and healthy patients. To elucidate those differences, we carried out a patient-specific, computational modeling comparative study. Methods: Computed tomography and ultrasound velocity and area data were used to build and validate computational models for a cohort of IVCS (N = 4, Subject group) and control (N = 4, Control group) patients. Flow, cross-sectional area, and shear rate were compared between the right common iliac vein (RCIV) and left common iliac vein (LCIV) for each group and between the Subject and Control groups for the same vessel. Results: For the IVCS patients, LCIV mean shear rate was higher than RCIV mean shear rate (550 ± 103 s-1 vs. 113 ± 48 s-1, p = 0.0009). Furthermore, LCIV mean shear rate was higher in the Subject group than in the Control group (550 ± 103 s-1 vs. 75 ± 37 s-1, p = 0.0001). Lastly, the LCIV/RCIV shear rate ratio was 4.6 times greater in the Subject group than in the Control group (6.56 ± 0.9 vs. 1.43 ± 0.6, p = 0.00008). Discussion: Our analyses revealed that IVCS patients have elevated shear rates which may explain a higher thrombosis risk and suggest that their thrombus initiation process may share aspects of arterial thrombosis. We have identified hemodynamic metrics that revealed profound differences between IVCS patients and Controls, and between RCIV and LCIV in the IVCS patients. Based on these metrics, we propose that non-invasive measurement of shear rate may aid with stratification of patients with moderate compression in which treatment is highly variable. More investigation is needed to assess the prognostic value of shear rate and shear rate ratio as clinical metrics and to understand the mechanisms of thrombus formation in IVCS patients.

Rodent Inferior Vena Cava Venoplasty Balloon Model.

Balloon venoplasty is a commonly used clinical technique to treat deep vein stenosis and occlusion as a consequence of trauma, congenital anatomic abnormalities, acute deep vein thrombosis (DVT), or stenting. Chronic deep venous obstruction is histopathologically characterized by thrombosis, fibrosis, or both. Currently, no direct treatment is available to target these pathological processes. Therefore, a reliable in vivo animal model to test novel interventions is necessary. The rodent survival inferior vena cava (IVC) venoplasty balloon model (VBM) allows the study of balloon venoplasty in non-thrombotic and post-thrombotic conditions across multiple time points. The local and systemic effect of coated and uncoated venoplasty balloons can be quantified via tissue, thrombus, and blood assays such as real-time polymerase chain reaction (RT-PCR), western blot, enzyme-linked immunosorbent assay (ELISA), zymography, vein wall and thrombus cellular analysis, whole blood and plasma assays, and histological analysis. The VBM is reproducible, replicates surgical human interventions, can identify local vein wall-thrombi protein changes, and allows multiple analyses from the same sample, decreasing the number of animals required per group.

von Willebrand factor-mediated platelet adhesion is critical for deep vein thrombosis in mouse models.

Deep vein thrombosis (DVT) and its complication, pulmonary embolism, are frequent causes of disability and mortality. Although blood flow disturbance is considered an important triggering factor, the mechanism of DVT initiation remains elusive. Here we show that 48-hour flow restriction in the inferior vena cava (IVC) results in the development of thrombi structurally similar to human deep vein thrombi. von Willebrand factor (VWF)-deficient mice were protected from thrombosis induced by complete (stasis) or partial (stenosis) flow restriction in the IVC. Mice with half normal VWF levels were also protected in the stenosis model. Besides promoting platelet adhesion, VWF carries Factor VIII. Repeated infusions of recombinant Factor VIII did not rescue thrombosis in VWF(-/-) mice, indicating that impaired coagulation was not the primary reason for the absence of DVT in VWF(-/-) mice. Infusion of GPG-290, a mutant glycoprotein Ibα-immunoglobulin chimera that specifically inhibits interaction of the VWF A1 domain with platelets, prevented thrombosis in wild-type mice. Intravital microscopy showed that platelet and leukocyte recruitment in the early stages of DVT was dramatically higher in wild-type than in VWF(-/-) IVC. Our results demonstrate a pathogenetic role for VWF-platelet interaction in flow disturbance-induced venous thrombosis.

The effect of matrix metalloproteinase 2 and matrix metalloproteinase 2/9 deletion in experimental post-thrombotic vein wall remodeling.

BACKGROUND: Vein wall fibrotic injury following deep venous thrombosis (VT) is associated with elevated matrix metalloproteinases (MMPs). Whether and by what mechanism MMP2 contributes to vein wall remodeling after VT is unknown. METHODS: Stasis VT was produced by ligation of the inferior vena cava and tissue was harvested at 2, 8, and 21 days in MMP2 -/- and genetic wild type (WT) mice. Tissue analysis by immunohistochemistry, enzyme-linked immunosorbent assay, real-time polymerase chain reaction, and zymography was performed. RESULTS: Thrombus resolution was less at 8 days in MMP2 -/- compared with WT, evidenced by a 51% increase in VT size (P < .01), and threefold fewer von Willebrand's factor positive channels (P < .05). In MMP2 -/- mice, the main phenotypic fibrotic differences occurred at 8 days post-VT, with significantly less vein wall collagen content (P = .013), fourfold lower procollagen III gene expression (P < .01), but no difference in procollagen I compared with WT. Decreased inflammation in MMP2 -/- vein walls was suggested by ∼ threefold reduced TNFα and IL-1ß at 2 days and 8 days post-VT (P < .05). A fourfold increase in vein wall monocytes (P = .03) with threefold decreased apoptosis (P < .05), but no difference in cellular proliferation at 8 days was found in MMP2 -/- compared with WT. As increased compensatory MMP9 activity was observed in the MMP2 -/-mice, MMP2/9 double null mice had thrombus induced with VT harvest at 8 days. Consistently, twofold larger VT, a threefold decrease in vein wall collagen, and a threefold increase in monocytes were found (all P < .05). Similar findings were observed in MMP9 -/- mice administered an exogenous MMP2 inhibitor. CONCLUSIONS: In stasis VT, deletion of MMP2 was associated with less midterm vein wall fibrosis and inflammation, despite an increase in monocytes. Consideration that VT resolution was impaired with MMP2 (and MMP2/9) deletion suggests direct inhibition will likely also require anticoagulant therapy.

Critical review of mouse models of venous thrombosis.

Deep vein thrombosis and pulmonary embolism are a significant health care concern, representing a major source of mortality and morbidity. In order to understand the pathophysiology of thrombogenesis and thrombus resolution, animal models are necessary. Mouse models of venous thrombosis contribute to our understanding of the initiation, propagation, and resolution of venous thrombus, as well as allow for the evaluation of new pharmaceutical approaches to prophylaxis and treatment of deep vein thrombosis. In this work we review the ferric chloride model, the inferior vena cava ligation model, the inferior vena cava stenosis models, and the electrolytic inferior vena cava model and compare their advantages and disadvantages.

Extracellular DNA traps promote thrombosis.

Neutrophil extracellular traps (NETs) are part of the innate immune response to infections. NETs are a meshwork of DNA fibers comprising histones and antimicrobial proteins. Microbes are immobilized in NETs and encounter a locally high and lethal concentration of effector proteins. Recent studies show that NETs are formed inside the vasculature in infections and noninfectious diseases. Here we report that NETs provide a heretofore unrecognized scaffold and stimulus for thrombus formation. NETs perfused with blood caused platelet adhesion, activation, and aggregation. DNase or the anticoagulant heparin dismantled the NET scaffold and prevented thrombus formation. Stimulation of platelets with purified histones was sufficient for aggregation. NETs recruited red blood cells, promoted fibrin deposition, and induced a red thrombus, such as that found in veins. Markers of extracellular DNA traps were detected in a thrombus and plasma of baboons subjected to deep vein thrombosis, an example of inflammation-enhanced thrombosis. Our observations indicate that NETs are a previously unrecognized link between inflammation and thrombosis and may further explain the epidemiological association of infection with thrombosis.