Illustrated State-of-the-Art Capsules of the ISTH 2024 Congress.

Here, we present a series of illustrated capsules from the State of the Art (SOA) speakers at the 2024 International Society on Thrombosis and Haemostasis Congress in Bangkok, Thailand. This year's Congress marks the first time that the International Society on Thrombosis and Haemostasis has held its flagship scientific meeting in Southeast Asia and is the first to be organized by an international Planning Committee. The Bangkok program will feature innovative science and clinical updates from around the world, reflecting the diversity and multidisciplinary growth of our field. In these illustrated SOA capsules, you will find an exploration of novel models of thrombosis and bleeding and biomaterial discoveries that can trigger or block coagulation. Thromboinflammation is now understood to drive many disease states, and the SOA speakers cover cellular and coagulation responses to COVID-19 and other infections. The theme of crosstalk between coagulation and inflammation expands with capsules on protein S signaling, complement, and fibrinolytic inhibitors. Novel agents for hemophilia and thrombosis prevention are introduced. Challenging clinical conditions are also covered, such as inherited platelet disorders and antiphospholipid antibody syndrome. The scientific program in Bangkok will also showcase the work of clinicians and scientists from all parts of the world and chronicle real-world challenges. For example, 2 SOA capsules address the diagnosis and management of von Willebrand disease in low-income settings. Take some time to browse through these short illustrated reviews; we're sure that you'll be entertained, educated, and inspired to further explore the world of thrombosis and hemostasis.

EXAMINING VARIABILITY IN THE DIAGNOSIS AND MANAGEMENT OF PEOPLE WITH BLEEDING DISORDERS OF UNKNOWN CAUSE: COMMUNICATION FROM THE ISTH SSC SUBCOMMITTEE ON VON WILLEBRAND FACTOR.

BACKGROUND: Bleeding disorder of unknown cause (BDUC) is characterised by a bleeding phenotype in the setting of normal haemostatic testing. No standardised diagnostic criteria or treatment algorithms exist for people with BDUC. To address the unmet need, the International Society on Thrombosis and Haemostasis von Willebrand Factor Scientific Subcommittee (ISTH VWF SCC) performed a real-world survey, aimed at addressing knowledge gaps, developing consensus pathways and ultimately improving care. OBJECTIVES AND METHODS: We sought to determine current international clinical practices in the investigation, registration, and treatment of people with BDUC through an online structured survey of health care providers (HCPs) who managed patient with bleeding disorders. RESULTS: Two hundred and sixteen respondents from 39 countries were included in the final analysis. The clinical assessment of those with a possible bleeding disorder varied, with only 55% excluding hypermobility but high levels (80%) of bleeding assessment tools (BAT) usage. In haemostatic testing only the prothrombin time (PT) and activated partial thromboplastin time (APTT) tests gained universal support. Tranexamic acid (TXA) was favoured for prophylaxis for minor (71%)/major (59%) surgeries and pregnancy (58%) but advice on the treatment advised if bleeding occurred was heterogeneous. The management of heavy menstrual bleeding (HMB) in women despite combined oral contraceptive pill (COCP) use also proved challenging with HCPs selecting multiple alternative strategies. CONCLUSION: Significant variation exists in the recognition, registration and management of people with BDUC worldwide. This survey emphasises the need for consensus pathways to diagnose and treat BDUC to standardise and improve care for patients internationally.

Standardization of definition and management for bleeding disorder of unknown cause: communication from the SSC of the ISTH.

In many patients referred with significant bleeding phenotype, laboratory testing fails to define any hemostatic abnormalities. Clinical practice with respect to diagnosis and management of this patient cohort poses significant clinical challenges. We recommend that bleeding history in these patients should be objectively assessed using the International Society on Thrombosis and Haemostasis (ISTH) bleeding assessment tool. Patients with increased bleeding assessment tool scores should progress to hemostasis laboratory testing. To diagnose bleeding disorder of unknown cause (BDUC), normal complete blood count, prothrombin time, activated partial thromboplastin time, thrombin time, von Willebrand factor antigen, von Willebrand factor function, coagulation factors VIII, IX, and XI, and platelet light transmission aggregometry should be the minimum laboratory assessment. In some laboratories, additional specialized hemostasis testing may be performed to identify other rare causes of bleeding. We recommend that patients with a significant bleeding phenotype but normal laboratory investigations should be registered with a diagnosis of BDUC in preference to other terminology. Global hemostatic tests and markers of fibrinolysis demonstrate variable abnormalities, and their clinical significance remains uncertain. Targeted genomic sequencing examining candidate hemostatic genes has a low diagnostic yield. Underlying BDUC should be considered in patients with heavy menstrual bleeding since delays in diagnosis often extend to many years and negatively impact quality of life. Treatment options for BDUC patients include tranexamic acid, desmopressin, and platelet transfusions.

Type 1 VWD classification revisited: novel insights from combined analysis of the LoVIC and WiN studies.

ABSTRACT: There is significant ongoing debate regarding type 1 von Willebrand disease (VWD) defintion. Previous guidelines recommended patients with von Willebrand factor (VWF) levels <30 IU/dL be diagnosed type 1 VWD, whereas patients with significant bleeding and VWF levels from 30 to 50 IU/dL be diagnosed with low VWF. To elucidate the relationship between type 1 VWD and low VWF in the context of age-induced increases in VWF levels, we combined data sets from 2 national cohort studies: 162 patients with low VWF from the Low VWF in Ireland Cohort (LoVIC) and 403 patients with type 1 VWD from the Willebrand in The Netherlands (WiN) studies. In 47% of type 1 VWD participants, VWF levels remained <30 IU/dL despite increasing age. Conversely, VWF levels increased to the low VWF range (30-50 IU/dL) in 30% and normalized (>50 IU/dL) in 23% of type 1 VWD cases. Crucially, absolute VWF antigen (VWF:Ag) levels and increase of VWF:Ag per year overlapped between low VWF and normalized type 1 VWD participants. Moreover, multiple regression analysis demonstrated that VWF:Ag levels in low VWF and normalized type 1 VWD patients would not have been different had they been diagnosed at the same age (ß = 0.00; 95% confidence interval, -0.03 to 0.04). Consistently, no difference was found in the prevalence of VWF sequence variants; factor VIII activity/VWF:Ag or VWF propeptide/VWF:Ag ratios; or desmopressin responses between low VWF and normalized type 1 VWD patients. In conclusion, our findings demonstrate that low VWF does not constitute a discrete clinical or pathological entity. Rather, it is part of an age-dependent type 1 VWD evolving phenotype. Collectively, these data have important implications for future VWD classification criteria.

VWF-ADAMTS13 axis dysfunction in children with sickle cell disease treated with hydroxycarbamide vs blood transfusion.

Previous studies have reported elevated von Willebrand factor (VWF) levels in patients with sickle cell disease (SCD) and demonstrated a key role for the VWF-ADAMTS13 axis in the pathobiology of SCD vaso-occlusion. Although blood transfusion is the gold standard for stroke prevention in SCD, the biological mechanisms underpinning its improved efficacy compared with hydroxycarbamide are not fully understood. We hypothesized that the improved efficacy of blood transfusion might relate to differences in VWF-ADAMTS13 axis dysfunction. In total, 180 children with a confirmed diagnosis of SCD (hemoglobin SS) on hydroxycarbamide (n = 96) or blood transfusion (n = 84) were included. Despite disease-modifying treatment, plasma VWF and VWF propeptide were elevated in a significant proportion of children with SCD (33% and 47%, respectively). Crucially, all VWF parameters were significantly higher in the hydroxycarbamide compared with the blood transfusion cohort (P < .05). Additionally, increased levels of other Weibel-Palade body-stored proteins, including factor VIII (FVIII), angiopoietin-2, and osteoprotegerin were observed, indicated ongoing endothelial cell activation. Children treated with hydroxycarbamide also had higher FVIII activity and enhanced thrombin generation compared with those in the blood transfusion cohort (P < .001). Finally, hemolysis markers strongly correlated with VWF levels (P < .001) and were significantly reduced in the blood transfusion cohort (P < .001). Cumulatively, to our knowledge, our findings demonstrate for the first time that despite treatment, ongoing dysfunction of the VWF-ADAMTS13 axis is present in a significant subgroup of pediatric patients with SCD, especially those treated with hydroxycarbamide.

Direct oral anticoagulants or vitamin K antagonists in emergencies: comparison of management in an observational study.

Background: Restoring hemostasis in patients on oral anticoagulants presenting with major hemorrhage (MH) or before surgical intervention has changed, with the replacement of vitamin K antagonist (VKA) with direct oral anticoagulants (DOACs). Objectives: To observe the difference in urgent hemostatic management between patients on VKA and those on DOACs. Methods: A multicenter observational study evaluated the variation in laboratory testing, hemostatic management, mortality, and hospital length of stay (LOS) in patients on VKA or DOACs presenting with MH or urgent hemostatic restoration. Results: Of the 1194 patients analyzed, 783 had MH (61% VKA) and 411 required urgent hemostatic restoration before surgery (56% VKA). Compared to the international normalized ratio (97.6%), plasma DOAC levels were measured less frequently (<45%), and the time taken from admission for the coagulation sample to reach the laboratory varied widely (median, 52.3 minutes; IQR, 24.8-206.7). No significant plasma DOAC level (<50 ng/mL) was found in up to 19% of patients. There was a poor relationship between plasma DOAC level and the usage of a hemostatic agent. When compared with patients receiving VKA (96.5%) or dabigatran (93.7%), fewer patients prescribed a factor Xa inhibitor (75.5%) received a prohemostatic reversal agent. The overall 30-day mortality for MH (mean: 17.8%) and length of stay (LOS) (median: 8.7 days) was similar between VKA and DOAC patients. Conclusion: In DOAC patients, when compared to those receiving VKA, plasma DOAC levels were measured less frequently than the international normalized ratio and had a poor relationship with administering a hemostatic reversal agent. In addition, following MH, mortality and LOS were similar between VKA and DOAC patients.

Low von Willebrand Disease: A Bleeding Disorder of Unknown Cause?

von Willebrand disease (VWD) represents the most common inherited bleeding disorder. The majority of VWD cases are characterized by partial quantitative reductions in plasma von Willebrand factor (VWF) levels. Management of patients with mild to moderate VWF reductions in the range of 30 to 50 IU/dL poses a common clinical challenge. Some of these low VWF patients present with significant bleeding problems. In particular, heavy menstrual bleeding and postpartum hemorrhage can cause significant morbidity. Conversely, however, many individuals with mild plasma VWF:Ag reductions do not have any bleeding sequelae. In contrast to type 1 VWD, most patients with low VWF do not have detectable pathogenic VWF sequence variants, and bleeding phenotype correlates poorly with residual VWF levels. These observations suggest that low VWF is a complex disorder caused by variants in other genes beyond VWF. With respect to low VWF pathobiology, recent studies have shown that reduced VWF biosynthesis within endothelial cells likely plays a key role. However, pathological enhanced VWF clearance from plasma has also been described in approximately 20% of low VWF cases. For low VWF patients who require hemostatic treatment prior to elective procedures, tranexamic acid and desmopressin have both been shown to be efficacious. In this article, we review the current state of the art regarding low VWF. In addition, we consider how low VWF represents an entity that appears to fall between type 1 VWD on the one hand and bleeding disorders of unknown cause on the other.

Endothelial cell activation, Weibel-Palade body secretion, and enhanced angiogenesis in severe COVID-19.

Background: Severe COVID-19 is associated with marked endothelial cell (EC) activation that plays a key role in immunothrombosis and pulmonary microvascular occlusion. However, the biological mechanisms through which SARS-CoV-2 causes EC activation and damage remain poorly defined. Objectives: We investigated EC activation in patients with acute COVID-19, and specifically focused on how proteins stored within Weibel-Palade bodies may impact key aspects of disease pathogenesis. Methods: Thirty-nine patients with confirmed COVID-19 were recruited. Weibel-Palade body biomarkers (von Willebrand factor [VWF], angiopoietin-2 [Angpt-2], and osteoprotegerin) and soluble thrombomodulin (sTM) levels were determined. In addition, EC activation and angiogenesis were assessed in the presence or absence of COVID-19 plasma incubation. Results: Markedly elevated plasma VWF antigen, Angpt-2, osteoprotegerin, and sTM levels were observed in patients with acute COVID-19. The increased levels of both sTM and Weibel-Palade body components (VWF, osteoprotegerin, and Angpt-2) correlated with COVID-19 severity. Incubation of COVID-19 plasma with ECs triggered enhanced VWF secretion and increased Angpt-2 expression, as well as significantly enhanced in vitro EC tube formation and angiogenesis. Conclusion: We propose that acute SARS-CoV-2 infection leads to a complex and multifactorial EC activation, progressive loss of thrombomodulin, and increased Angpt-2 expression, which collectively serve to promote a local proangiogenic state.

Adenosine 2A Receptor Activation Amplifies Ibrutinib Antiplatelet Effect; Implications in Chronic Lymphocytic Leukemia.

Chronic lymphocytic leukemia patients have an increased bleeding risk with the introduction of Bruton tyrosine kinase (BTK) inhibitors. BTK is a signaling effector downstream of the platelet GPVI receptor. Innate platelet dysfunction in CLL patients and the contribution of the leukemia microenvironment to the anti-platelet effect of BTK inhibitors are still not well defined. Herein, we investigated platelet function in stable, untreated CLL patients in comparison to age-matched healthy subjects as control. Secondly, we proposed a novel mechanism of platelet dysfunction via the adenosinergic pathway during BTK inhibitor therapy. Our data indicate that the nucleotidase that produces adenosine, CD73, was expressed on one-third of B-cells in CLL patients. Inhibition of CD73 improved platelet response to ADP in the blood of CLL patients ex vivo. Using healthy platelets, we show that adenosine 2A (A2A) receptor activation amplifies the anti-platelet effect of ibrutinib (10 nM). Ibrutinib plus an A2A agonist-but not ibrutinib as a single agent-significantly inhibited collagen (10 µg/mL)-induced platelet aggregation. Mechanistically, A2A activation attenuated collagen-mediated inhibition of p-VASP and synergized with ibrutinib to inhibit the phosphorylation of AKT, ERK and SYK kinases. This manuscript highlights the potential role of adenosine generated by the microenvironment in ibrutinib-associated bleeding in CLL patients.

Sustained VWF-ADAMTS-13 axis imbalance and endotheliopathy in long COVID syndrome is related to immune dysfunction.

BACKGROUND: Prolonged recovery is common after acute SARS-CoV-2 infection; however, the pathophysiological mechanisms underpinning Long COVID syndrome remain unknown. VWF/ADAMTS-13 imbalance, dysregulated angiogenesis, and immunothrombosis are hallmarks of acute COVID-19. We hypothesized that VWF/ADAMTS-13 imbalance persists in convalescence together with endothelial cell (EC) activation and angiogenic disturbance. Additionally, we postulate that ongoing immune cell dysfunction may be linked to sustained EC and coagulation activation. PATIENTS AND METHODS: Fifty patients were reviewed at a minimum of 6 weeks following acute COVID-19. ADAMTS-13, Weibel Palade Body (WPB) proteins, and angiogenesis-related proteins were assessed and clinical evaluation and immunophenotyping performed. Comparisons were made with healthy controls (n = 20) and acute COVID-19 patients (n = 36). RESULTS: ADAMTS-13 levels were reduced (p = 0.009) and the VWF-ADAMTS-13 ratio was increased in convalescence (p = 0.0004). Levels of platelet factor 4 (PF4), a putative protector of VWF, were also elevated (p = 0.0001). A non-significant increase in WPB proteins Angiopoietin-2 (Ang-2) and Osteoprotegerin (OPG) was observed in convalescent patients and WPB markers correlated with EC parameters. Enhanced expression of 21 angiogenesis-related proteins was observed in convalescent COVID-19. Finally, immunophenotyping revealed significantly elevated intermediate monocytes and activated CD4+ and CD8+ T cells in convalescence, which correlated with thrombin generation and endotheliopathy markers, respectively. CONCLUSION: Our data provide insights into sustained EC activation, dysregulated angiogenesis, and VWF/ADAMTS-13 axis imbalance in convalescent COVID-19. In keeping with the pivotal role of immunothrombosis in acute COVID-19, our findings support the hypothesis that abnormal T cell and monocyte populations may be important in the context of persistent EC activation and hemostatic dysfunction during convalescence.

Examining international practices in the management of pregnant women with von Willebrand disease.

BACKGROUND: The management of pregnant women with von Willebrand disease (VWD) is complex as physiological pregnancy-induced increases in plasma von Willebrand factor (VWF) may be blunted or absent. Women with VWD experience a heightened risk of postpartum hemorrhage (PPH) and special consideration must be given regarding neuraxial anesthesia (NA) and the need for prophylaxis at time of delivery. These challenges are compounded by a lack of robust evidence to guide clinical decision-making. OBJECTIVES AND METHODS: To determine the current international clinical practices in the management of pregnancy for women with VWD, the International Society on Thrombosis and Haemostasis (ISTH) conducted an international survey of health-care providers (HCP). RESULTS: One hundred thirty-two respondents from 39 countries were included in the final analysis. Variations in clinical practice were identified in antenatal (monitoring of plasma VWF and ferritin levels), peripartum (optimal plasma VWF target at delivery) and postpartum management (definitions used for PPH and postpartum monitoring). A key area of divergence was suitability for NA for women with type 2 and type 3 VWD, with many respondents advising against the use of NA even with VWF supplementation (29% type 2 VWD, 37% type 3 VWD) but others advising use once plasma VWF activity was >50 IU/dL (57% type 2 VWD; 50% type 3 VWD). CONCLUSIONS: This survey highlighted areas of uncertainty surrounding common management issues for pregnant women with VWD. These data underscore the need for international collaborative research efforts focused on peripartum management to improve care for pregnant women with VWD.

Fc Binding by FcγRIIa Is Essential for Cellular Activation by the Anti-FcγRIIa mAbs 8.26 and 8.2.

FcγR activity underpins the role of antibodies in both protective immunity and auto-immunity and importantly, the therapeutic activity of many monoclonal antibody therapies. Some monoclonal anti-FcγR antibodies activate their receptors, but the properties required for cell activation are not well defined. Here we examined activation of the most widely expressed human FcγR; FcγRIIa, by two non-blocking, mAbs, 8.26 and 8.2. Crosslinking of FcγRIIa by the mAb F(ab')2 regions alone was insufficient for activation, indicating activation also required receptor engagement by the Fc region. Similarly, when mutant receptors were inactivated in the Fc binding site, so that intact mAb was only able to engage receptors via its two Fab regions, again activation did not occur. Mutation of FcγRIIa in the epitope recognized by the agonist mAbs, completely abrogated the activity of mAb 8.26, but mAb 8.2 activity was only partially inhibited indicating differences in receptor recognition by these mAbs. FcγRIIa inactivated in the Fc binding site was next co-expressed with the FcγRIIa mutated in the epitope recognized by the Fab so that each mAb 8.26 molecule can contribute only three interactions, each with separate receptors, one via the Fc and two via the Fab regions. When the Fab and Fc binding were thus segregated onto different receptor molecules receptor activation by intact mAb did not occur. Thus, receptor activation requires mAb 8.26 Fab and Fc interaction simultaneously with the same receptor molecules. Establishing the molecular nature of FcγR engagement required for cell activation may inform the optimal design of therapeutic mAbs.

Persistent endotheliopathy in the pathogenesis of long COVID syndrome.

BACKGROUND: Persistent symptoms including breathlessness, fatigue, and decreased exercise tolerance have been reported in patients after acute SARS-CoV-2 infection. The biological mechanisms underlying this "long COVID" syndrome remain unknown. However, autopsy studies have highlighted the key roles played by pulmonary endotheliopathy and microvascular immunothrombosis in acute COVID-19. OBJECTIVES: To assess whether endothelial cell activation may be sustained in convalescent COVID-19 patients and contribute to long COVID pathogenesis. PATIENTS AND METHODS: Fifty patients were reviewed at a median of 68 days following SARS-CoV-2 infection. In addition to clinical workup, acute phase markers, endothelial cell (EC) activation and NETosis parameters and thrombin generation were assessed. RESULTS: Thrombin generation assays revealed significantly shorter lag times (p < .0001, 95% CI -2.57 to -1.02 min), increased endogenous thrombin potential (p = .04, 95% CI 15-416 nM/min), and peak thrombin (p < .0001, 95% CI 39-93 nM) in convalescent COVID-19 patients. These prothrombotic changes were independent of ongoing acute phase response or active NETosis. Importantly, EC biomarkers including von Willebrand factor antigen (VWF:Ag), VWF propeptide (VWFpp), and factor VIII were significantly elevated in convalescent COVID-19 compared with controls (p = .004, 95% CI 0.09-0.57 IU/ml; p = .009, 95% CI 0.06-0.5 IU/ml; p = .04, 95% CI 0.03-0.44 IU/ml, respectively). In addition, plasma soluble thrombomodulin levels were significantly elevated in convalescent COVID-19 (p = .02, 95% CI 0.01-2.7 ng/ml). Sustained endotheliopathy was more frequent in older, comorbid patients, and those requiring hospitalization. Finally, both plasma VWF:Ag and VWFpp levels correlated inversely with 6-min walk tests. CONCLUSIONS: Collectively, our findings demonstrate that sustained endotheliopathy is common in convalescent COVID-19 and raise the intriguing possibility that this may contribute to long COVID pathogenesis.

How I treat bleeding disorder of unknown cause.

Recent studies have demonstrated that only 30% of patients referred for assessment of a possible bleeding tendency will eventually be diagnosed with a mild bleeding disorder (MBD) such as von Willebrand disease (VWD) or platelet function defect (PFD). Rather, most of these patients will be diagnosed with bleeding disorder of unknown cause (BDUC). There remains an important unmet need to define consensus regarding the clinical and laboratory criteria necessary for a formal BDUC diagnosis. Accumulating recent data suggest that BDUC is being diagnosed with increasing frequency. Objective assessment of bleeding phenotype using a standardized bleeding assessment tool (BAT) therefore represents a fundamental first step in the diagnosis of BDUC. Because BDUC is a diagnosis by exclusion, accurate quantification of bleeding phenotype is critical because this will be the primary determinant on which a diagnosis of BDUC is reached. Importantly, BAT scores suggest that patients with BDUC display bleeding phenotypes comparable to those seen in patients with VWD or PFD. Despite the prevalence of BDUC, diagnosis and management of these patients commonly pose significant clinical dilemmas. We consider these challenges in the context of a number of typical case studies, discuss the available evidence, and outline our approach to the management of these patients.

ADAMTS13 regulation of VWF multimer distribution in severe COVID-19.

BACKGROUND: Consistent with fulminant endothelial cell activation, elevated plasma von Willebrand factor (VWF) antigen levels have been reported in patients with COVID-19. The multimeric size and function of VWF are normally regulated through A Disintegrin And Metalloprotease with ThrombSpondin Motif type 1 motif, member 13 (ADAMTS-13)--mediated proteolysis. OBJECTIVES: This study investigated the hypothesis that ADAMTS-13 regulation of VWF multimer distribution may be impaired in severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection contributing to the observed microvascular thrombosis. PATIENTS AND METHODS: Patients with COVID-19 (n = 23) were recruited from the Beaumont Hospital Intensive Care Unit (ICU) in Dublin. Plasma VWF antigen, multimer distribution, ADAMTS-13 activity, and known inhibitors thereof were assessed. RESULTS: We observed markedly increased VWF collagen-binding activity in patients with severe COVID-19 compared to controls (median 509.1 versus 94.3 IU/dl). Conversely, plasma ADAMTS-13 activity was significantly reduced (median 68.2 IU/dl). In keeping with an increase in VWF:ADAMTS-13 ratio, abnormalities in VWF multimer distribution were common in patients with COVID-19, with reductions in high molecular weight VWF multimers. Terminal sialylation regulates VWF susceptibility to proteolysis by ADAMTS-13 and other proteases. We observed that both N- and O-linked sialylation were altered in severe COVID-19. Furthermore, plasma levels of the ADAMTS-13 inhibitors interleukin-6, thrombospondin-1, and platelet factor 4 were significantly elevated. CONCLUSIONS: These findings support the hypothesis that SARS-CoV-2 is associated with profound quantitative and qualitative increases in plasma VWF levels, and a multifactorial down-regulation in ADAMTS-13 function. Further studies will be required to determine whether therapeutic interventions to correct ADAMTS-13-VWF multimer dysfunction may be useful in COVID-microvascular thrombosis and angiopathy.

Estradiol-Responsive miR-365a-3p Interacts with Tissue Factor 3'UTR to Modulate Tissue Factor-Initiated Thrombin Generation.

BACKGROUND: High estradiol (E2) levels are linked to an increased risk of venous thromboembolism; however, the underlying molecular mechanism(s) remain poorly understood. We previously identified an E2-responsive microRNA (miR), miR-494-3p, that downregulates protein S expression, and posited additional coagulation factors, such as tissue factor, may be regulated in a similar manner via miRs. OBJECTIVES: To evaluate the coagulation capacity of cohorts with high physiological E2, and to further characterize novel E2-responsive miR and miR regulation on tissue factor in E2-related hypercoagulability. METHODS: Ceveron Alpha thrombin generation assay (TGA) was used to assess plasma coagulation profile of three cohorts. The effect of physiological levels of E2, 10 nM, on miR expression in HuH-7 cells was compared using NanoString nCounter and validated with independent assays. The effect of tissue factor-interacting miR was confirmed by dual-luciferase reporter assays, immunoblotting, flow cytometry, biochemistry assays, and TGA. RESULTS: Plasma samples from pregnant women and women on the contraceptive pill were confirmed to be hypercoagulable (compared with sex-matched controls). At equivalent and high physiological levels of E2, miR-365a-3p displayed concordant E2 downregulation in two independent miR quantification platforms, and tissue factor protein was upregulated by E2 treatment. Direct interaction between miR-365a-3p and F3-3'UTR was confirmed and overexpression of miR-365a-3p led to a decrease of (1) tissue factor mRNA transcripts, (2) protein levels, (3) activity, and (4) tissue factor-initiated thrombin generation. CONCLUSION: miR-365a-3p is a novel tissue factor regulator. High E2 concentrations induce a hypercoagulable state via a miR network specific for coagulation factors.

Prognostic utility of ADAMTS13 activity for the atypical hemolytic uremic syndrome (aHUS) and comparison of complement serology between aHUS and thrombotic thrombocytopenic purpura.

BACKGROUND: Atypical hemolytic uremic syndrome (aHUS) involves dysregulation of the complement system, but whether this also occurs in thrombotic thrombocytopenic purpura (TTP) remains unclear. Although these conditions are difficult to differentiate clinically, TTP can be distinguished by low (<10%) ADAMTS13 activity. The aim was to identify the differences in complement activation products between TTP and aHUS and investigate ADAMTS13 activity as a prognostic factor in aHUS. METHODS: We analyzed patients with thrombotic microangiopathy diagnosed as TTP (N=48) or aHUS (N=50), selected from a Korean registry (N=551). Complement activation products in the plasma samples collected from the patients prior to treatment and in 40 healthy controls were measured by ELISA. RESULTS: The levels of generalized (C3a), alternate (factor Bb), and terminal (C5a and C5b-9) markers were significantly higher (all P<0.01) in the patients than in the healthy controls. Only the factor Bb levels significantly differed (P=0.008) between the two disease groups. In aHUS patients, high normal ADAMTS13 activity (≥77%) was associated with improved treatment response (OR, 6.769; 95% CI, 1.605-28.542; P=0.005), remission (OR, 6.000; 95% CI, 1.693-21.262; P=0.004), exacerbation (OR, 0.242; 95% CI, 0.064-0.916; P=0.031), and disease-associated mortality rates (OR, 0.155; 95% CI, 0.029-0.813; P=0.017). CONCLUSION: These data suggest that complement biomarkers, except factor Bb, are similarly activated in TTP and aHUS patients, and ADAMTS13 activity can predict the treatment response and outcome in aHUS patients.

A Multicenter Trial of Vena Cava Filters in Severely Injured Patients.

BACKGROUND: Whether early placement of an inferior vena cava filter reduces the risk of pulmonary embolism or death in severely injured patients who have a contraindication to prophylactic anticoagulation is not known. METHODS: In this multicenter, randomized, controlled trial, we assigned 240 severely injured patients (Injury Severity Score >15 [scores range from 0 to 75, with higher scores indicating more severe injury]) who had a contraindication to anticoagulant agents to have a vena cava filter placed within the first 72 hours after admission for the injury or to have no filter placed. The primary end point was a composite of symptomatic pulmonary embolism or death from any cause at 90 days after enrollment; a secondary end point was symptomatic pulmonary embolism between day 8 and day 90 in the subgroup of patients who survived at least 7 days and did not receive prophylactic anticoagulation within 7 days after injury. All patients underwent ultrasonography of the legs at 2 weeks; patients also underwent mandatory computed tomographic pulmonary angiography when prespecified criteria were met. RESULTS: The median age of the patients was 39 years, and the median Injury Severity Score was 27. Early placement of a vena cava filter did not result in a significantly lower incidence of symptomatic pulmonary embolism or death than no placement of a filter (13.9% in the vena cava filter group and 14.4% in the control group; hazard ratio, 0.99; 95% confidence interval [CI], 0.51 to 1.94; P = 0.98). Among the 46 patients in the vena cava filter group and the 34 patients in the control group who did not receive prophylactic anticoagulation within 7 days after injury, pulmonary embolism developed in none of those in the vena cava filter group and in 5 (14.7%) in the control group, including 1 patient who died (relative risk of pulmonary embolism, 0; 95% CI, 0.00 to 0.55). An entrapped thrombus was found in the filter in 6 patients. CONCLUSIONS: Early prophylactic placement of a vena cava filter after major trauma did not result in a lower incidence of symptomatic pulmonary embolism or death at 90 days than no placement of a filter. (Funded by the Medical Research Foundation of Royal Perth Hospital and others; Australian New Zealand Clinical Trials Registry number, ACTRN12614000963628.).

Construction of a Bivalent Thrombin Binding Aptamer and Its Antidote with Improved Properties.

Aptamers are short synthetic DNA or RNA oligonucleotides that adopt secondary and tertiary conformations based on Watson-Crick base-pairing interactions and can be used to target a range of different molecules. Two aptamers, HD1 and HD22, that bind to exosites I and II of the human thrombin molecule, respectively, have been extensively studied due to their anticoagulant potentials. However, a fundamental issue preventing the clinical translation of many aptamers is degradation by nucleases and reduced pharmacokinetic properties requiring higher dosing regimens more often. In this study, we have chemically modified the design of previously described thrombin binding aptamers targeting exosites I, HD1, and exosite II, HD22. The individual aptamers were first modified with an inverted deoxythymidine nucleotide, and then constructed bivalent aptamers by connecting the HD1 and HD22 aptamers either through a triethylene glycol (TEG) linkage or four consecutive deoxythymidines together with an inverted deoxythymidine nucleotide at the 3'-end. The anticoagulation potential, the reversal of coagulation with different antidote sequences, and the nuclease stability of the aptamers were then investigated. The results showed that a bivalent aptamer RNV220 containing an inverted deoxythymidine and a TEG linkage chemistry significantly enhanced the anticoagulation properties in blood plasma and nuclease stability compared to the existing aptamer designs. Furthermore, a bivalent antidote sequence RNV220AD efficiently reversed the anticoagulation effect of RNV220 in blood plasma. Based on our results, we believe that RNV220 could be developed as a potential anticoagulant therapeutic molecule.