Vascular-bed--specific hemostasis and hypercoagulable states

Human Umbilical Vein Endothelial Cells as a Versatile Cellular Model System in Diverse Experimental Paradigms: An Ultrastructural Perspective

Human umbilical vein endothelial cells (HUVECs) are primary cells isolated from the vein of an umbilical cord, extensively used in cardiovascular studies and medical research. These cells, retaining the characteristics of endothelial cells in vivo, serve as a valuable cellular model system for understanding vascular biology, endothelial dysfunction, pathophysiology of diseases such as atherosclerosis, and responses to different drugs or treatments. Transmission electron microscopy (TEM) has been a cornerstone in revealing the detailed architecture of multiple cellular model systems including HUVECs, allowing researchers to visualize subcellular organelles, membrane structures, and cytoskeletal elements. Among them, the endoplasmic reticulum, Golgi apparatus, mitochondria, and nucleus can be meticulously examined to recognize alterations indicative of cellular responses to various stimuli. Importantly, Weibel-Palade bodies are characteristic secretory organelles found in HUVECs, which can be easily distinguished in the TEM. These distinctive structures also dynamically react to different factors through regulated exocytosis, resulting in complete or selective release of their contents. This detailed review summarizes the ultrastructural features of HUVECs and highlights the utility of TEM as a pivotal tool for analyzing HUVECs in diverse research frameworks, contributing valuable insights into the comprehension of HUVEC behavior and enriching our knowledge into the complexity of vascular biology.

Mechanisms regulating heterogeneity of hemostatic gene expression in endothelial cells

The hemostatic system involves an array of circulating coagulation factors that work in concert with platelets and the vascular endothelium to promote clotting in a space- and time-defined manner. Despite equal systemic exposure to circulating factors, bleeding and thrombotic diseases tend to prefer specific sites, suggesting an important role for local factors. This may be provided by endothelial heterogeneity. Endothelial cells differ not only between arteries, veins, and capillaries but also between microvascular beds from different organs, which present unique organotypic morphology and functional and molecular profiles. Accordingly, regulators of hemostasis are not uniformly distributed in the vasculature. The establishment and maintenance of endothelial diversity are orchestrated at the transcriptional level. Recent transcriptomic and epigenomic studies have provided a global picture of endothelial cell heterogeneity. In this review, we discuss the organotypic differences in the hemostatic profile of endothelial cells; we focus on 2 major endothelial regulators of hemostasis, namely von Willebrand factor and thrombomodulin, to provide examples of transcriptional mechanisms that control heterogeneity; finally, we consider some of the methodological challenges and opportunities for future studies.

Bleeding Control in Advanced Gastric Cancer; Role of Radiotherapy

Objectives

The aim of our study is to see the efficacy of palliative radiotherapy (RT) for bleeding control in patients with advanced gastric cancer (AGC).

Materials and Methods

It is a retrospective review based on observations of 74 AGC patients with a median age of 60 years (range 50-82 years) who had active tumour bleeding and were treated with palliative RT. Treatment response was assessed by both subjective symptom relief and objective change in parameters. Objective response to RT was defined by an increase in the median haemoglobin (Hb) level of patients and a decrease in number of packed red blood cell (RBC) units needed by patients after RT.

Results

Response to haemostatic RT was observed in 52 patients out of 74 patients (70.27%). We observed a significant increase in mean Hb level after palliative RT. Pre-RT mean Hb was 6.14 ± 1.01 and post-RT mean Hb was 7.19 ± 1.75 (P < 0.05). Response to RT was also evident in a significant decrease in the number of packed RBC units post-haemostatic RT. The mean number of pre-RT transfused packed RBC units was 8.28 ± 3.76 and post-RT, it was 4.34 ± 2.91 (P < 0.05). The median overall survival was 90 days and the median transfusion-free survival was 40 days.

Conclusion

RT may be an effective treatment option for bleeding control in AGC. In our study, we observed fair and reasonably durable haemostasis. A success rate of 70.24% was documented with clinical palliation, a higher Hb level and fewer transfusions after RT. This modality for bleeding control is more important and reliable in situations where alternative modalities are not feasible.

Angiotensin II and dengue

Dengue is a disease caused by a flavivirus that is transmitted principally by the bite of an Aedes aegypti mosquito and represents a major public-health problem. Many studies have been carried out to identify soluble factors that are involved in the pathogenesis of this infection. Cytokines, soluble factors, and oxidative stress have been reported to be involved in the development of severe disease. Angiotensin II (Ang II) is a hormone with the ability to induce the production of cytokines and soluble factors related to the inflammatory processes and coagulation disorders observed in dengue. However, a direct involvement of Ang II in this disease has not been demonstrated. This review primarily summarizes the pathophysiology of dengue, the role of Ang II in various diseases, and reports that are highly suggestive of the involvement of this hormone in dengue.

Blood tissue Plasminogen Activator (tPA) of liver origin contributes to neurovascular coupling involving brain endothelial N-Methyl-D-Aspartate (NMDA) receptors

BACKGROUND

Regulation of cerebral blood flow (CBF) directly influence brain functions and dysfunctions and involves complex mechanisms, including neurovascular coupling (NVC). It was suggested that the serine protease tissue-type plasminogen activator (tPA) could control CNV induced by whisker stimulation in rodents, through its action on N-methyl-D-Aspartate receptors (NMDARs). However, the origin of tPA and the location and mechanism of its action on NMDARs in relation to CNV remained debated.

METHODS

Here, we answered these issues using tPA^Null mice, conditional deletions of either endothelial tPA (VECad-Cre^ΔtPA) or endothelial GluN1 subunit of NMDARs (VECad-Cre^ΔGluN1), parabioses between wild-type and tPA^Null mice, hydrodynamic transfection-induced deletion of liver tPA, hepatectomy and pharmacological approaches.

RESULTS

We thus demonstrate that physiological concentrations of vascular tPA, achieved by the bradykinin type 2 receptors-dependent production and release of tPA from liver endothelial cells, promote NVC, through a mechanism dependent on brain endothelial NMDARs.

CONCLUSIONS

These data highlight a new mechanism of regulation of NVC involving both endothelial tPA and NMDARs.

To Clot or Not to Clot: Deepening Our Understanding of Alterations in the Hemostatic System

The session on the hemostatic system focused on new developments in coagulation and platelet biology as well as how therapeutic agents may affect hemostasis. The classic cascade model of coagulation was compared with the more recent models of cell-based and vascular-based coagulation, which may provide better insight on how the coagulation cascade works in vivo. A review of platelet biology highlighted that, as platelets age, desialylated platelets form and are recognized by Ashwell-Morell receptor (AMR), leading to hepatic uptake and subsequent increase in thrombopoietin (TPO) production. Administration of therapeutics that induce thrombocytopenia was also discussed, including Mylotarg, which is an antibody-drug conjugate that was shown to decrease human megakaryocyte development but had no effect on platelet aggregation. An acetyl co-A carboxylase inhibitor was shown to cause thrombocytopenia by inhibiting de novo lipogenesis, which is critical for the formation of the megakaryocyte demarcation membrane system responsible for platelet production. It was also illustrated how preclinical translation models have been very helpful in the development of adeno-associated virus (AAV) hemophilia B gene therapy and what old and new preclinical tools we have that can predict the risk of a prothrombotic state in people.

Intracerebral hemorrhage and thrombin-induced alterations in cerebral microvessel matrix

Four phase III clinical trials of oral direct factor Xa or thrombin inhibitors demonstrated significantly lower intracranial hemorrhage compared to warfarin in patients with nonvalvular-atrial fibrillation. This is counter-intuitive to the principle that inhibiting thrombosis should increase hemorrhagic risk. We tested the novel hypothesis that anti-thrombin activity decreases the risk of intracerebral hemorrhage by directly inhibiting thrombin-mediated degradation of cerebral microvessel basal lamina matrix, responsible for preventing hemorrhage. Collagen IV, laminin, and perlecan each contain one or more copies of the unique α-thrombin cleavage site consensus sequence. In blinded controlled experiments, α-thrombin significantly degraded each matrix protein in vitro and in vivo in a concentration-dependent fashion. In vivo stereotaxic injection of α-thrombin significantly increased permeability, local IgG extravasation, and hemoglobin (Hgb) deposition together with microvessel matrix degradation in a mouse model. In all formats the direct anti-thrombin dabigatran completely inhibited matrix degradation by α-thrombin. Fourteen-day oral exposure to dabigatran etexilate-containing chow completely inhibited matrix degradation, the permeability to large molecules, and cerebral hemorrhage associated with α-thrombin. These experiments demonstrate that thrombin can degrade microvessel matrix, leading to hemorrhage, and that inhibition of microvessel matrix degradation by α-thrombin decreases cerebral hemorrhage. Implications for focal ischemia and other conditions are discussed.

Clinical and imaging risk factors for the persistence of thromboembolism following acute pulmonary embolism

Background

Predicting the progression of acute pulmonary embolism to chronic pulmonary thromboembolism (CPTE) disease is essential to monitoring and improving the long-term prognosis of pulmonary embolism. We explored the risk factors for chronic persistence of thromboembolism after acute pulmonary embolism.

Methods

Cases with newly onset acute pulmonary embolism in the China-Japan Friendship Hospital from November 2016 to November 2019 were retrospectively analyzed. The clinical characteristics, serological examination results, and treatment strategies of acute pulmonary embolism patients were obtained through the electronic medical record system (Goodwill E-Health Info Co., Ltd.). Imaging parameters on computed tomography pulmonary angiography (CTPA) images at the onset of the acute pulmonary embolism were measured and counted. Notably, we propose a new parameter based on CTPA images: the ratio of S_d (sum of residual segmental pulmonary artery diameter) to MPA_d (the main pulmonary artery diameter) (S_d/MPA_d). After 3 months of regular treatment for acute pulmonary embolism, patients were classified into a CPTE group or a non-CPTE group based on the presence of residual embolus. All data were compared between the CPTE group and non-CPTE group. Furthermore, logistic regression analysis was used to investigate risk factors for the progression of acute pulmonary embolism to CPTE.

Results

A total of 77 cases (male:female = 1:1.26) were included in the study. There were 43 cases (55.84%) in the CPTE group and 34 cases in the non-CPTE group (44.16%). The results of univariate analysis showed that there were statistically significant differences between the 2 groups in risk stratification (χ²=8.043; P=0.005), protein S activity (χ²=5.551; P=0.018), the ratio of sum of residual segmental pulmonary artery diameter to the main pulmonary artery diameter (S_d/MPA_d; t=–2.103; P=0.039), Mastora score (U=362.500; P<0.001), and embolus location (χ²=16.969; P<0.001). However, there were no statistically significant differences between the 2 groups in treatment options (P=0.381). According to multivariate logistic-regression analysis, protein S activity <55% (P=0.025), S_d/MPA_d ≥1.97 (P=0.011), and an embolus being located in the central pulmonary artery (P<0.001) were independent risk factors for chronic persistence of thromboembolism following acute pulmonary embolism.

Conclusions

The protein S activity, location of the embolus, and S_d/MPA_d on CTPA at the onset of acute pulmonary embolism may suggest the progression of acute pulmonary embolism to CPTE.

Molecular analysis of vascular gene expression

A State of the Art lecture entitled "Molecular Analysis of Vascular Gene Expression" was presented at the ISTH Congress in 2021. Endothelial cells (ECs) form a critical interface between the blood and underlying tissue environment, serving as a reactive barrier to maintain tissue homeostasis. ECs play an important role in not only coagulation, but also in the response to inflammation by connecting these two processes in the host defense against pathogens. Furthermore, ECs tailor their behavior to the needs of the microenvironment in which they reside, resulting in a broad display of EC phenotypes. While this heterogeneity has been acknowledged for decades, the contributing molecular mechanisms have only recently started to emerge due to technological advances. These include high-throughput sequencing combined with methods to isolate ECs directly from their native tissue environment, as well as sequencing samples at a high cellular resolution. In addition, the newest technologies simultaneously quantitate and visualize a multitude of RNA transcripts directly in tissue sections, thus providing spatial information. Understanding how ECs function in (patho)physiological conditions is crucial to develop new therapeutics as many diseases can directly affect the endothelium. Of particular relevance for thrombotic disorders, EC dysfunction can lead to a procoagulant, proinflammatory phenotype with increased vascular permeability that can result in coagulopathy and tissue damage, as seen in a number of infectious diseases, including sepsis and coronavirus disease 2019. In light of the current pandemic, we will summarize relevant new data on the latter topic presented during the 2021 ISTH Congress.

Correlation Between D-Dimer Concentrations and Thromboelastography in Dogs With Critical Illness: A Retrospective, Cross-Sectional Study

A hospital-based, retrospective, cross-sectional study was performed to assess the correlation of kaolin-activated thromboelastography (TEG) with D-dimer concentrations in 59 dogs with critical illness. Dogs were included if they had one or more serious disease detected upon performing TEG and D-dimer concentration determination based on the same blood sample. According to the coagulation index (CI), the 59 dogs were divided into two groups: a hypercoagulable state, with CI > 4 (44 dogs) and a normocoagulable state, with CI < 4 (15 dogs). Moreover, the 44 dogs with CI > 4 were divided into three sub-groups according to the disease etiology, i.e., inflammatory/tumor (I/T: 25 dogs), hemodynamic compromise (H: 11 dogs), and both conditions (I/TH: 8 dogs). The median values (interquartile ranges) of the CI and D-dimer concentration were 5.46 (4.55–6.33) and 410.25 (74.63–2206.12) in the 44 dogs with CI > 4 and 3.29 (2.92–3.75) and 1164.7 (50–2250.05) in the 15 dogs with CI < 4, respectively. The D-dimer concentration was significantly increased over the reference value in the 44 dogs with a CI > 4, particularly in dogs in the I/T group. It was also significantly increased in the 15 dogs with a CI < 4. D-dimer concentrations did not correlate with any of the TEG parameters in any of the dogs. Given this lack of correlation, the D-dimer concentration may be limited as an indicator of a possible hypercoagulable state in dogs with critical illness.

Factor IX(a) inhibitors: an updated patent review (2003-present)

INTRODUCTION

Anticoagulation with no bleeding complications is the current objective of drug discovery programs in the area of treating and/or preventing thromboembolism. Despite the promises of therapeutics targeting factors XI(a) and XII(a), none has been approved thus far. Clinically used thrombin- and/or factor Xa-based anticoagulants continue to be associated with a significant bleeding risk which limits their safe use in a broad range of thrombotic patients. Research findings in animals and humans indicate that it is possible to target factor IX(a) (FIX(a)) to achieve anticoagulation with a limited risk of bleeding.

AREAS COVERED

A review of patents literature has retrieved >35 patents on the development of molecules targeting FIX(a) since 2003. Small molecules, antibodies, and aptamers have been developed to target FIX(a) to potentially promote effective and safer anticoagulation. Most of these agents are in the pre-clinical development phase and few have been tested in clinical trials.

EXPERT OPINION

FIX(a) system is being considered to develop new anticoagulants with fewer bleeding complications. Our survey indicates that the number of FIX(a)-targeting agents is mediocre. The agents under development are diverse. Although additional development is essential, moving one or more of these agents to the clinic will facilitate achieving better clinical outcomes.

The EHA Research Roadmap: Blood Coagulation and Hemostatic Disorders

In 2016, the European Hematology Association (EHA) published the EHA Roadmap for European Hematology Research1 aiming to highlight achievements in the diagnostics and treatment of blood disorders, and to better inform European policy makers and other stakeholders about the urgent clinical and scientific needs and priorities in the field of hematology. Each section was coordinated by 1-2 section editors who were leading international experts in the field. In the 5 years that have followed, advances in the field of hematology have been plentiful. As such, EHA is pleased to present an updated Research Roadmap, now including 11 sections, each of which will be published separately. The updated EHA Research Roadmap identifies the most urgent priorities in hematology research and clinical science, therefore supporting a more informed, focused, and ideally funded future for European hematology research. The 11 EHA Research Roadmap sections include Normal Hematopoiesis; Malignant Lymphoid Diseases; Malignant Myeloid Diseases; Anemias and Related Diseases; Platelet Disorders; Blood Coagulation and Hemostatic Disorders; Transfusion Medicine; Infections in Hematology; Hematopoietic Stem Cell Transplantation; CAR-T and Other Cell-based Immune Therapies; and Gene Therapy.

Coagulopathy and sepsis: Pathophysiology, clinical manifestations and treatment

Sepsis is a complex syndrome with a high incidence, increasing by 8.7% annually over the last 20 years. Coagulopathy is a leading factor associated with mortality in patients with sepsis and range from slight thrombocytopenia to fatal disorders, such as disseminated intravascular coagulation (DIC). Platelet reactivity increases during sepsis but prospective trials of antiplatelet therapy during sepsis have been disappointing. Thrombocytopenia is a known predictor of worse prognosis during sepsis. The mechanisms underlying thrombocytopenia in sepsis have yet to be fully understood but likely involves decreased platelet production, platelet sequestration and increased consumption. DIC is an acquired thrombohemorrhagic syndrome, resulting in intravascular fibrin formation, microangiopathic thrombosis, and subsequent depletion of coagulation factors and platelets. DIC can be resolved with treatment of the underlying disorder, which is considered the cornerstone in the management of this syndrome. This review presents the current knowledge on the pathophysiology, diagnosis, and treatment of sepsis-associated coagulopathies.

Pathogenesis of cardiovascular events in BCR-ABL1-negative myeloproliferative neoplasms

Thrombosis, both in arterial and venous territories, is the major complication of myeloproliferative neoplasms and is responsible for a high rate of morbidity and mortality. The currently accepted risk factors are an age over 60 years and a history of thrombosis. However, many complex mechanisms contribute to this increased prothrombotic risk, with involvement of all blood cell types, plasmatic factors, and endothelial cells. Besides, some cardiovascular events may originate from arterial vasospasm that could contribute to thrombotic complications. In this review, we discuss recent results obtained in mouse models in the light of data obtained from clinical studies. We emphasize on actors of thrombosis that are currently not targeted with current therapeutics but could be promising targets, i.e, neutrophil extracellular traps and vascular reactivity.

New-onset acute rapidly deteriorating case of calciphylaxis after open heart surgery: a case report

Background 

Calciphylaxis is a rare life-threatening condition that is characterized by calcification of small blood vessels and soft tissues. This condition is classically described in uraemic patients with end-stage renal failure who are on dialysis or had previous renal transplant. It has also been reported in non-uraemic patients and those who are on warfarin therapy. It is typically associated with high calcium/phosphorus product. Patients classically present with painful skin lesion that evolve into painful ulcers. There are multiple risk factors that were reported to trigger or worsen calciphylaxis. Treatment is a multidisciplinary approach that involves elimination of risk factors, wound management, pain control, and optimization of calcium/phosphorus metabolism. Reported mortality rates are very high especially in the uraemic group.

Case summary 

Here we present a case of a patient, who is on chronic renal dialysis for stage renal failure, who underwent mechanical mitral valve replacement and tricuspid valve repair. In the perioperative period, she was exposed to multiple risk factors that are known to potentially trigger prophylaxis. In the early postoperative period, she developed new-onset rapidly deteriorating skin lesions and the histopathological diagnosis confirmed calciphylaxis. Her treatment plan included pain control, frequent wound care, and optimization of nutritional and metabolic status.

Discussion 

Calciphylaxis is a very serious condition that is usually associated with poor outcome. In this case, we discuss the unusual presentation of this condition with particular emphasis on the multiple perioperative risk factors that can potentially trigger the onset of calciphylaxis in postoperative cardiac patients. We also discuss the epidemiology, pathogenesis, diagnosis, histopathological findings, and different lines of treatment of this serious condition and the potential preventative strategies.

Old drug, new Trick? The rationale for the treatment of COVID-19 with activated protein C

As the COVID-19 pandemic continues, researchers seek to identify efficacious treatments. Current approaches to COVID-19 therapeutics focus on antiviral agents, convalescent plasma, monoclonal antibodies, immunomodulators and more traditional therapies such as steroids [1], [2], [3], [4], [5], [6]. Reversing disturbances in coagulation has also been identified as a priority area for candidate therapies, such as through the Accelerating COVID-19 Therapeutic Interventions and Vaccines 4 adaptive clinical trial (ACTIV-4) which is currently evaluating aspirin, heparins and apixaban [7]. Since there is a clear relationship between mechanisms of coagulation and the immune response, it is possible that reversing disturbances in coagulation may diminish the dysregulated immune response observed in COVID-19. The basis for this hypothesis is described below and is followed by discussion of a proposed candidate therapy - activated protein C. By treating COVID-19 patients using a novel approach, which does not focus on immune-based or antiviral treatments, but instead which addresses both the anti-thrombotic and inflammatory consequences of infection, the hope is that new therapeutic targets can be considered and new candidate therapies, such as activated protein C, may be evaluated.

Systemic Coagulopathy in Hospitalized Patients With Coronavirus Disease 2019: A Systematic Review and Meta-Analysis

Coagulation activation has been reported in several cohorts of patients Coronavirus Disease 2019 (COVID-19). However, the true burden of systemic coagulopathy in COVID-19 remains unknown. In this systematic review and meta-analysis, we performed a literature search using PubMed, EMBASE, and Cochrane Database to identify studies that reported the prevalence of systemic coagulopathy using established criteria in patients with COVID-19. The primary outcome was the prevalence of systemic coagulopathy (disseminated intravascular coagulation [DIC] and/or sepsis-induced coagulopathy [SIC]). Pooled prevalences and 95% confidence intervals [CIs] were calculated using random-effects model. A total of 5 studies including 1210 patients with confirmed COVID-19 were included. The pooled prevalence of systemic coagulopathy was 7.1% (95%CI: 3.2%,15.3%, I² = 93%). The pooled prevalence of DIC (N = 721) and SIC (N = 639) were 4.3% (95%CI 1.7%, 10.4%, I² = 84%) and 16.2% (95%CI: 9.3%, 26.8%, I² = 74%), respectively. Only 2 studies reported the prevalence of elevated D-dimer levels with the pooled prevalence of 84.6% (95%CI: 52.0%,96.5%, I² = 94%). Average D-dimer and fibrinogen levels were remarkably increased, while platelet counts, PT, and aPTT ratios were minimally affected in COVID-19. The estimated prevalence of systemic coagulopathy in patients with COVID-19 was low despite D-dimer elevation in most patients. Relatively low systemic coagulopathy in COVID-19 may contribute to the high incidence of thrombosis rather than bleeding in patients with COVID-19.

Effects of remote ischemic preconditioning on platelet activation and reactivity in patients undergoing cardiac surgery using cardiopulmonary bypass: a randomized controlled trial

During cardiopulmonary bypass (CPB), platelet activation and dysfunction are associated with adverse outcomes. Remote ischemic preconditioning (RIPC) has been shown to attenuate platelet activation. We evaluated the effects of RIPC on platelet activation during CPB in patients undergoing cardiac surgery. Among 58 randomized patients, 26 in the RIPC group and 28 in the sham-RIPC group were analyzed. RIPC consisted of 4 cycles of 5-min ischemia induced by inflation of pneumatic cuff pressure to 200 mmHg, followed by 5-min reperfusion comprising deflation of the cuff on the upper arm. Platelet activation was assessed using flow cytometry analysis of platelet activation markers. The primary endpoint was the AUC of CD62P expression during the first 3 h after initiation of CPB. Secondary outcomes were the AUC of PAC-1 expression and monocyte-platelet aggregates (MPA) during 3 h of CPB. The AUCs of CD62P expression during 3 h after initiation of CPB were 219.4 ± 43.9 and 211.0 ± 41.2 MFI in the RIPC and sham-RIPC groups, respectively (mean difference, 8.42; 95% CI, -14.8 and 31.7 MFI; p =.471). The AUCs of PAC-1 expression and MPA did not differ between groups. RIPC did not alter platelet activation and reactivity during CPB in patients undergoing cardiac surgery.

tPA Deficiency Underlies Neurovascular Coupling Dysfunction by Amyloid-β

The amyloid-β (Aβ) peptide, a key pathogenic factor in Alzheimer's disease, attenuates the increase in cerebral blood flow (CBF) evoked by neural activity (functional hyperemia), a vital homeostatic response in which NMDA receptors (NMDARs) play a role through nitric oxide, and the CBF increase produced by endothelial factors. Tissue plasminogen activator (tPA), which is reduced in Alzheimer's disease and in mouse models of Aβ accumulation, is required for the full expression of the NMDAR-dependent component of functional hyperemia. Therefore, we investigated whether tPA is involved in the neurovascular dysfunction of Aβ. tPA activity was reduced, and the tPA inhibitor plasminogen inhibitor-1 (PAI-1) was increased in male mice expressing the Swedish mutation of the amyloid precursor protein (tg2576). Counteracting the tPA reduction with exogenous tPA or with pharmacological inhibition or genetic deletion of PAI-1 completely reversed the attenuation of the CBF increase evoked by whisker stimulation but did not ameliorate the response to the endothelium-dependent vasodilator acetylcholine. The tPA deficit attenuated functional hyperemia by suppressing NMDAR-dependent nitric oxide production during neural activity. Pharmacological inhibition of PAI-1 increased tPA activity, prevented neurovascular uncoupling, and ameliorated cognition in 11- to 12-month-old tg2576 mice, effects associated with a reduction of cerebral amyloid angiopathy but not amyloid plaques. The data unveil a selective role of the tPA in the suppression of functional hyperemia induced by Aβ and in the mechanisms of cerebral amyloid angiopathy, and support the possibility that modulation of the PAI-1-tPA pathway may be beneficial in diseases associated with amyloid accumulation.SIGNIFICANCE STATEMENT Amyloid-β (Aβ) peptides have profound neurovascular effects that may contribute to cognitive impairment in Alzheimer's disease. We found that Aβ attenuates the increases in blood flow evoked by neural activation through a reduction in tissue plasminogen activator (tPA) caused by upregulation of its endogenous inhibitor plasminogen inhibitor-1 (PAI-1). tPA deficiency prevents NMDA receptors from triggering nitric oxide production, thereby attenuating the flow increase evoked by neural activity. PAI-1 inhibition restores tPA activity, rescues neurovascular coupling, reduces amyloid deposition around blood vessels, and improves cognition in a mouse model of Aβ accumulation. The findings demonstrate a previously unappreciated role of tPA in Aβ-related neurovascular dysfunction and in vascular amyloid deposition. Restoration of tPA activity could be of therapeutic value in diseases associated with amyloid accumulation.

Associations between clinical features and therapy with macrophage subpopulations and T cells in inflammatory lesions in the aorta from patients with Takayasu arteritis

Takayasu arteritis (TAK) is a large-vessel granulomatous vasculitis; the inflammatory infiltration in arteries comprises macrophages, multi-nucleated giant cells, CD4⁺ and CD8⁺ T cells, γδ T cells, natural killer (NK) cells and neutrophils. However, it is unknown which subtype of macrophages predominates. This study aims to evaluate macrophages subpopulations in the aorta in TAK. Immunohistochemistry was performed in the aorta from TAK patients (n = 22), patients with atherosclerotic disease (n = 9) and heart transplant donors (n = 8) using the markers CD68, CD86, CD206, CD3, CD20 and CD56. Active disease was observed in 54·5% of patients and active histological lesions were found in 40·9%. TAK patients presented atherosclerotic lesions in 27·3% of cases. The frequency of macrophages, M1 macrophages, T, B and NK cells was higher in the aorta from TAK and atherosclerotic patients compared to heart transplant donors. In TAK, macrophages and T cells were the most abundant cells in the aorta, and the expression of CD206 was higher than CD86 (P = 0·0007). No associations were found between the expression of cell markers and active disease or with atherosclerotic lesions. In TAK patients, histological disease activity led to higher T cell counts than chronic fibrotic lesions (P = 0.030), whereas prednisone use was associated with lower T cell counts (P = 0·035). In conclusion, M1 macrophages were more frequent in TAK and atherosclerotic patients compared to heart transplant donors, while M2 macrophages dominated M1 macrophages in TAK. T cells were associated with histological disease activity and with prednisone use in TAK.

Expression profiles of the internal jugular and saphenous veins: Focus on hemostasis genes

INTRODUCTION

Venous bed specificity could contribute to differential vulnerability to thrombus formation, and is potentially reflected in mRNA profiles.

MATERIALS AND METHODS

Microarray-based transcriptome analysis in wall and valve specimens from internal jugular (IJV) and saphenous (SV) veins collected during IJV surgical reconstruction in patients with impaired brain outflow. Multiplex antigenic assay in paired jugular and peripheral plasma samples.

RESULTS

Most of the top differentially expressed transcripts have been previously associated with both vascular and neurological disorders. Large expression differences of HOX genes, organ patterning regulators, pinpointed the vein positional identity. The "complement and coagulation cascade" emerged among enriched pathways. In IJV, upregulation of genes for coagulation inhibitors (TFPI, PROS1), activated protein C pathway receptors (THBD, PROCR), fibrinolysis activators (PLAT, PLAUR), and downregulation of the fibrinolysis inhibitor (SERPINE1) and of contact/amplification pathway genes (F11, F12), would be compatible with a thromboprotective profile in respect to SV. Further, in SV valve the prothrombinase complex genes (F5, F2) were up-regulated and the VWF showed the highest expression. Differential expression of several VWF regulators (ABO, ST3GAL4, SCARA5, CLEC4M) was also observed. Among other differentially expressed hemostasis-related genes, heparanase (HPSE)/heparanase inhibitor (HPSE2) were up-/down-regulated in IJV, which might support procoagulant features and disease conditions. The jugular plasma levels of several proteins, encoded by differentially expressed genes, were lower and highly correlated with peripheral levels.

CONCLUSIONS

The IJV and SV rely on differential expression of many hemostasis and hemostasis-related genes to balance local hemostasis, potentially related to differences in vulnerability to thrombosis.

Therapeutic strategies for thrombosis: new targets and approaches

Antiplatelet agents and anticoagulants are a mainstay for the prevention and treatment of thrombosis. However, despite advances in antithrombotic therapy, a fundamental challenge is the side effect of bleeding. Improved understanding of the mechanisms of haemostasis and thrombosis has revealed new targets for attenuating thrombosis with the potential for less bleeding, including glycoprotein VI on platelets and factor XIa of the coagulation system. The efficacy and safety of new agents are currently being evaluated in phase III trials. This Review provides an overview of haemostasis and thrombosis, details the current landscape of antithrombotic agents, addresses challenges with preventing thromboembolic events in patients at high risk and describes the emerging therapeutic strategies that may break the inexorable link between antithrombotic therapy and bleeding risk.

Mouse venous thrombosis upon silencing of anticoagulants depends on tissue factor and platelets, not FXII or neutrophils

Tissue factor, coagulation factor XII, platelets, and neutrophils are implicated as important players in the pathophysiology of (experimental) venous thrombosis (VT). Their role became evident in mouse models in which surgical handlings were required to provoke VT. Combined inhibition of the natural anticoagulants antithrombin (Serpinc1) and protein C (Proc) using small interfering RNA without additional triggers also results in a venous thrombotic phenotype in mice, most notably with vessel occlusion in large veins of the head. VT is fatal but is fully rescued by thrombin inhibition. In the present study, we used this VT mouse model to investigate the involvement of tissue factor, coagulation factor XII, platelets, and neutrophils. Antibody-mediated inhibition of tissue factor reduced the clinical features of VT, the coagulopathy in the head, and fibrin deposition in the liver. In contrast, genetic deficiency in, and small interfering RNA-mediated depletion of, coagulation factor XII did not alter VT onset, severity, or thrombus morphology. Antibody-mediated depletion of platelets fully abrogated coagulopathy in the head and liver fibrin deposition. Although neutrophils were abundant in thrombotic lesions, depletion of circulating Ly6G-positive neutrophils did not affect onset, severity, thrombus morphology, or liver fibrin deposition. In conclusion, VT after inhibition of antithrombin and protein C is dependent on the presence of tissue factor and platelets but not on coagulation factor XII and circulating neutrophils. This study shows that distinct procoagulant pathways operate in mouse VT, dependent on the triggering stimulus.

Predictive value of combining the level of lipoprotein-associated phospholipase A2 and antithrombin III for acute coronary syndrome risk

The aim of the present study was to observe the role of lipoprotein-associated phospholipase A2 (Lp-PLA2) and antithrombin III (AT-III) in patients with acute coronary syndrome (ACS), and the combination of Global Registry of Acute Coronary Events (GRACE) score to determine the value of coronary heart disease risk stratification. A total of 309 patients admitted to the Affiliated Hospital of Xuzhou Medical University were enrolled. The patients were divided into two groups: The ACS (183 cases) and control (126 cases) groups. Blood levels of Lp-PLA2 and AT-III were measured. Based on GRACE score, the patients with ACS were divided into three subgroups: Low risk (GRACE score ≤108), middle risk (GRACE score 109-140) and high risk (GRACE score >140). The levels of Lp-PLA2 and AT-III were compared among different groups, and based on Gensini score, patients with ACS were divided into four groups by quartiles. Lp-PLA2 levels in the ACS group were significantly increased compared with the control group (P<0.05), but the AT-III levels were decreased compared with the control group (P<0.05). In the ACS group, Lp-PLA2 levels increased sequentially from the low risk to high risk subgroups (all P<0.05); compared with the low risk and middle risk subgroups, the AT-III activity levels were decreased in the high risk subgroup, and the Gensini scores were increased (all P<0.05). In the ACS group, with the increase of Gensini scores, the levels of Lp-PLA2 and AT-III exhibited increasing and decreasing trends, respectively (P<0.05). The logistic regression model demonstrated that Lp-PLA2 [odds ratio (OR) =1.077; P<0.001]; and GRACE score (OR=1.026; P=0.028) were risk factors, while AT-III was a protective factor (OR=0.958; P=0.012) for ACS. Correlation analysis indicated a positive association of Lp-PLA2 level with Gensini scores (r=0.52; P<0.01) and GRACE score (r=0.48; P<0.01), and a negative association between AT-III level and Gensini scores (r=-0.25; P<0.01) and GRACE scores (r=-0.34; P<0.01). The levels of Lp-PLA2 and AT-III exhibited predictive values in patients with ACS, and are associated with the severity of coronary artery stenosis.

Anti-tissue factor pathway inhibitor (TFPI) therapy: a novel approach to the treatment of haemophilia

Novel approaches to the treatment of haemophilia are needed due to the limitations of the current standard of care, factor replacement therapy. Aspirations include lessening the treatment burden and effectively preventing joint damage. Treating haemophilia by restoring thrombin generation may be an effective approach. A promising target for restoring thrombin generation is tissue factor pathway inhibitor (TFPI), a multivalent Kunitz-type serine protease inhibitor that regulates tissue factor-induced coagulation via factor Xa-dependent feedback inhibition of the tissue factor-factor VIIa complex. Inhibition of TFPI reverts the coagulation process to a more primitive state evolutionarily, whilst regulation by other natural inhibitors is preserved. An aptamer and three monoclonal antibodies directed against TFPI have been investigated in clinical trials. As well as improving thrombin generation in the range associated with mild haemophilia, anti-TFPI therapies have the advantage of subcutaneous administration. However, the therapeutic window needs to be defined along with the potential for complications due to the novel mechanism of action. This review provides an overview of TFPI, its role in normal coagulation, the rationale for TFPI inhibition, and a summary of anti-TFPI therapies, previously or currently in development.

Disseminated intravascular coagulation: an update on pathogenesis and diagnosis

INTRODUCTION

Activation of the hemostatic system can occur in many clinical conditions. However, a systemic and strong activation of coagulation complicating clinical settings such as sepsis, trauma or malignant disease may result in the occurrence disseminated intravascular coagulation (DIC). Areas covered: This article reviews the clinical manifestation and relevance of DIC, the various conditions that may precipitate DIC and the pathogenetic pathways underlying the derangement of the hemostatic system, based on clinical and experimental studies. In addition, the (differential) diagnostic approach to DIC is discussed. Expert commentary: In recent years a lot of precise insights in the pathophysiology of DIC have been uncovered, leading to a better understanding of pathways leading to the hemostatic derangement and providing points of impact for better adjunctive treatment strategies. In addition, simple diagnostic algorithms have been developed and validated to establish a diagnosis of DIC in clinical practice.

Patient Assessment: Clinical Presentation, Imaging Diagnosis, Risk Stratification, and the Role of Pulmonary Embolism Response Team

Pulmonary embolism (PE) is currently the third leading cause of death and moreover is likely underdiagnosed. PE remains the most common preventable cause of hospital deaths in the United States, which may be attributable to its diagnostic challenges. Although difficult to diagnose, patient mortality rates are time-dependent, and thus, the suspicion and diagnosis of PE in a timely manner is imperative. Diagnosis based on several criteria which may dictate imaging workup as well as laboratory tests and clinical parameters are discussed. The evolution of treatment guidelines via various clinical trials and recommendations is outlined, setting the stage for the use of fibrinolytics, whether systemic or catheter directed. Treatment, including fibrinolytics, is predicated on patient triage into three large categories-massive, submassive, or low-risk PE. Additionally, a relatively new concept of a multidisciplinary team composed of several subspecialty experts known as the PE response team (PERT) is discussed. PERT's timely and unified recommendations have been shown to optimize care and decrease mortality while tailoring treatment to each individual afflicted by PE.

Glycative and oxidative stress are associated with altered thrombus composition in diabetic patients with ST-elevation myocardial infarction

BACKGROUND

The role of type 2 diabetes (T2DM) on composition of thrombus has not been fully characterized in patients with ST-elevation myocardial infarction (STEMI).

AIMS

To elucidate the differences between diabetic and non-diabetic patients with STEMI in relation to the composition of coronary thrombus, and the potential association of these differences with glycated haemoglobin levels and markers of oxidative stress.

METHODS

Intracoronary thrombi from consecutive thrombus aspiration procedures in STEMI patients, 25 diabetic and 28 non-diabetic, were analyzed by immunofluorescence with confocal microscopy. Plasma biomarkers (P-selectin, vWF, PAI-1, t-PA, D-dimer, TF pathway markers, plasmin and CD34⁺) were measured in peripheral blood, and the oxidative capacity of plasma as indirect measure of oxidative stress was measured in parallel.

RESULTS

Patients with T2DM had higher levels of fibrin (P=0.03), P-selectin (P=0.0001), PAI-1 (P=0.03) and vWF (P=0.006) in the thrombus and higher plasma TF activity (P=0.01) compared to non-diabetics. TF activity and plasmin correlated with HbA₁C levels (R²=0.71, P=0.0001; R²=0.46, P=0.04, respectively) and TF was inversely correlated with TFPI (R²=-0.44, P=0.008) and tPA (R²=-0.48, P=0.003). Diabetic patients showed a higher oxidative response of plasma (26.47±6.88% vs 22.06±6.96% of oxidized lipids, P=0.04) (measured by H-NMR spectroscopy) that was associated to increased fibrin content into thrombus (R²=0.76, P=0.01).

CONCLUSION

Diabetic patients with STEMI display an increased thrombogenicity that results in a different thrombus composition respect to non-diabetic patients with STEMI. The increased thrombogenicity present in T2DM is related to higher glycoxidative stress, as quantified by HbA₁C levels and oxidative response in plasma.

VEGF pathway targeting agents, vessel normalization and tumor drug uptake: from bench to bedside

Vascular endothelial growth factor (VEGF) pathway targeting agents have been combined with other anticancer drugs, leading to improved efficacy in carcinoma of the cervix, stomach, lung, colon and rectum, ovary, and breast. Vessel normalization induced by VEGF pathway targeting agents influences tumor drug uptake. Following bevacizumab treatment, preclinical and clinical studies have shown a decrease in tumor delivery of radiolabeled antibodies and two chemotherapeutic drugs. The decrease in vessel pore size during vessel normalization might explain the decrease in tumor drug uptake. Moreover, the addition of bevacizumab to cetuximab, or panitumumab in colorectal cancer patients or to trastuzumab in breast cancer patients, did not improve efficacy. However, combining bevacizumab with chemotherapy did increase efficacy in some cancer types. Novel biomarkers to select patients who may benefit from combination therapies, such as the effect of an angiogenesis inhibitor on tumor perfusion, requires innovative trial designs and large clinical trials. Small imaging studies with radiolabeled drugs could be used in the interphase to gain further insight into the interplay between VEGF targeted therapy, vessel normalization and tumor drug delivery.

Engineered Microvessels for the Study of Human Disease

The microvasculature is an extensive, heterogeneous, and complex system that plays a critical role in human physiology and disease. It nourishes almost all living human cells and maintains a local microenvironment that is vital for tissue and organ function. Operating under a state of continuous flow, with an intricate architecture despite its small caliber, and subject to a multitude of biophysical and biochemical stimuli, the microvasculature can be a complex subject to study in the laboratory setting. Engineered microvessels provide an ideal platform that recapitulates essential elements of in vivo physiology and allows study of the microvasculature in a precise and reproducible way. Here, we review relevant structural and functional vascular biology, discuss different methods to engineer microvessels, and explore the applications of this exciting tool for the study of human disease.

Association Between Hypercoagulability and Severe Obstructive Sleep Apnea

Importance

Obstructive sleep apnea (OSA) is related to the increased risk of cardiovascular disease. Although the pathogenesis of this association remains unclear, an alteration in coagulability is suspected as a link.

Objective

To investigate the association between the severity of OSA and blood coagulability.

Design, Setting, and Participants

A retrospective cohort study conducted at a tertiary care university hospital evaluated 146 patients with OSA from January 1, 2009, to July 31, 2015. The participants were divided into 4 groups according to the severity of OSA: control, mild, moderate, and severe.

Main Outcomes and Measures

Association between the severity of OSA and coagulation test results, including platelet count, bleeding time, prothrombin time (PT) in seconds and as international normalized ratio (INR), and activated partial thromboplastin time.

Results

Of the 146 patients, 135 (92.5%) were men; mean (SD) age was 34.8 (11.1) years. The control group included 41 (28.1%) patients; mild OSA, 32 (21.9%); moderate OSA, 30 (20.5%); and severe OSA, 43 (29.5%). Significant correlations were found between the apnea-hypopnea index and the PT seconds (Spearman r coefficient, -0.30; 95% CI, -0.44 to -0.14) and PT INR (Spearman r coefficient, -0.30; 95% CI, -0.44 to -0.14). There were significant differences between the OSA severity groups for PT seconds for the control group (mean, 11.26 [0.78] seconds) vs the moderate OSA group (10.74 [0.62] seconds; mean difference [MD], 0.52; 95% CI, 0.27 to 1.01) and the severe OSA group (10.67 [0.77] seconds; MD, 0.59; 95% CI, 0.14 to 1.03). Significant differences were also noted in PT INR between the control group (1.00 [0.07]) vs the moderate OSA group (0.95 [0.05]; MD, 0.04; 95% CI, 0.01 to 0.07) and the severe OSA group (0.94 [0.07]; MD, 0.05; 95% CI, 0.02 to 0.08). However, there was no significant difference between the control and mild OSA groups in PT seconds.

Conclusions and Relevance

These results suggest that patients with moderate to severe OSA have elevated blood coagulability markers compared with healthy individuals, which may contribute to the occurrence of cardiovascular complications.

Efficacy of Laropiprant in Minimizing Brain Injury Following Experimental Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is one of the most devastating and disabling forms of stroke, yet effective treatments are still lacking. Prostaglandins and their receptors have been implicated in playing vital roles in ICH outcomes. Recently, laropiprant, a DP1 receptor antagonist, has been used in combination with niacin to abolish the prostaglandin D2-(PGD2)-induced flushing. Here, we test the hypothesis that laropiprant limits bleeding and rescues the brain from ICH. Wildtype (WT) and DP1-/- mice were subjected ICH and neurologic deficits and hemorrhagic lesion outcomes were evaluated at 72 hours after the ICH. To test the therapeutic potential of laropiprant, WT mice subjected to ICH were treated with laropiprant at 1 hour after the ICH. The putative effect of laropiprant on limiting hematoma expansion was tested by an in vivo tail bleeding cessation method and an ex vivo coagulation method. Finally, the roles of laropiprant on gliosis and iron accumulation were also investigated. A significant decrease in the injury volume was observed in DP1-/- as well as laropiprant-treated WT mice. The tail bleeding time was significantly lower in laropiprant group as compared with the vehicle group. Significantly lower Iba-1 and Perls' iron staining in DP1-/- and laropiprant-treated WT groups were observed. Altogether, the data suggest that laropiprant treatment post-ICH attenuates brain damage by targeting primary as well as secondary injuries.

Flow chamber and microfluidic approaches for measuring thrombus formation in genetic bleeding disorders

Platelet adhesion and aggregation, coagulation, fibrin formation, and fibrinolysis are regulated by the forces and flows imposed by blood at the site of a vascular injury. Flow chambers designed to observe these events are an indispensable part of doing hemostasis and thrombosis research, especially with human blood. Microfluidic methods have provided the flexibility to design flow chambers with complex geometries and features that more closely mimic the anatomy and physiology of blood vessels. Additionally, microfluidic systems with integrated optics and/or pressure sensors and on-board signal processing could transform what have been primarily research tools into clinical assays. Here, we describe a historical review of how flow-based approaches have informed biophysical mechanisms in genetic bleeding disorders, challenges and potential solutions for developing models of bleeding in vitro, and outstanding issues that need to be addressed prior to their use in clinical settings.

Warfarin-Associated Nonuremic Calciphylaxis

Importance

Classic calciphylaxis associated with renal failure is a life-threatening disease. Warfarin-associated calciphylaxis without renal injury has been described, but whether it is a subset of classic calciphylaxis or a different entity remains unknown. We describe 1 case of warfarin-associated calciphylaxis, present data from 2 others from our institution, and review all cases of warfarin-associated calciphylaxis available in the literature. Our review indicates that warfarin-associated calciphylaxis is clinically and pathophysiologically distinct from classic calciphylaxis.

Objective

To review warfarin-associated calciphylaxis and determine its relationship to classic calciphylaxis.

Design, Setting, and Participants

We searched MEDLINE and Ovid without language or date restrictions for case reports of calciphylaxis from the inpatient setting using the terms "calciphylaxis and warfarin," "non-uremic calciphylaxis," and "nonuremic calciphylaxis." We defined nonuremic calciphylaxis as a histopathologic diagnosis of calciphylaxis without severe kidney disease (serum creatinine level >3 mg/dL; glomerular filtration rate <15 mL/min; acute kidney injury requiring dialysis; and renal transplantation).

Exposures

Each patient had been exposed to warfarin before the onset of calciphylaxis.

Main Outcomes and Measures

Patient data were abstracted from published reports. Original patient medical records were requested and reviewed when possible.

Results

We identified 18 patients with nonuremic calciphylaxis, 15 from the literature, and 3 from our institution. Patients were predominantly female (15 of 18 [83%]) with ages ranging from 19 to 86 years. Duration of warfarin therapy prior to calciphylaxis onset averaged 32 months. Lesions were usually located below the knees (in 12 of 18 [67%]). No cases reported elevated calcium-phosphate products (0 of 17 [0%]). Calcifications were most often noted in the tunica media (n = 8 [44%]) or in the vessel lumen and tunica intima (n = 7 [39%]). The most common treatments included substitution of heparin or low-molecular weight heparin for warfarin (n = 13 [72%]), intravenous sodium thiosulfate (n = 9 [50%]), and hyperbaric oxygen (n = 3 [17%]). The survival rate on hospital discharge was remarkably high, with 15 cases (83%) reporting full recovery and 3 cases ending in death.

Conclusions and Relevance

Warfarin-associated calciphylaxis is distinct from classic calciphylaxis in pathogenesis, course, and, particularly, outcome. This finding should influence clinical management of the disease and informs targeted treatment of the disease.

Upper Gastrointestinal Bleed as a Manifestation of Poorly Differentiated Metastatic Squamous Cell Carcinoma of the Lung

Gastrointestinal (GI) metastasis from primary lung cancer is a rare clinical finding. Lung cancer most often metastasizes to the brain, bone, liver, and adrenal glands; with gastrointestinal involvement being very rare. We report a case of a 39-year-old female with a diagnosis of poorly differentiated Squamous Cell Carcinoma (SCC) of the lung presenting with dizziness and melena. Esophagogastroduodenoscopy (EGD) showed a bleeding mass in the stomach. Final biopsy report and Immunohistochemistry (IHC) of the specimen were consistent with SCC lung metastasis. While it is imperative to have a high clinical suspicion for GI metastasis in patients with primary lung cancer presenting with GI symptoms, it may be challenging to establish diagnosis. Endoscopy along with pathology and immunohistochemistry play a crucial role in differentiating primary GI malignancies from metastasis.

Splanchnic vein thrombosis in myeloproliferative neoplasms: pathophysiology and molecular mechanisms of disease

Myeloproliferative neoplasms (MPNs) are the most common underlying prothrombotic disorder found in patients with splanchnic vein thrombosis (SVT). Clinical risk factors for MPN-associated SVTs include younger age, female sex, concomitant hypercoagulable disorders, and the JAK2 V617F mutation. These risk factors are distinct from those associated with arterial or deep venous thrombosis (DVT) in MPN patients, suggesting disparate disease mechanisms. The pathophysiology of SVT is thought to derive from local interactions between activated blood cells and the unique splanchnic endothelial environment. Other mutations commonly found in MPNs, including CALR and MPL, are rare in MPN-associated SVT. The purpose of this article is to review the clinical and molecular risk factors for MPN-associated SVT, with particular focus on the possible mechanisms of SVT formation in MPN patients.

Clinical significance of hyperhomocysteinemia in infective endocarditis: A case-control study

Blood coagulation plays a key role in the pathogenesis of infective endocarditis (IE). Conditions associated with thrombophilia could enhance IE vegetation formation and promote embolic complications.In this study, we assessed prevalence, correlates, and clinical consequences of hyper-homocysteinemia (h-Hcy) in IE.Homocysteine (Hcy) plasma levels were studied in 246 IE patients and 258 valvular heart disease (VHD) patients, as well as in 106 healthy controls.IE patients showed Hcy levels comparable to VHD patients (14.9 [3-81] vs 16 [5-50] μmol/L, respectively; P = 0.08). H-Hcy was observed in 48.8% of IE patients and 55.8% of VHD (P = 0.13). Vegetation size and major embolic complications were not related to Hcy levels. IE patients with h-Hcy had a higher prevalence of chronic kidney disease and a higher 1-year mortality (19.6% vs 9.9% in those without h-Hcy; OR 2.21 [1.00-4.89], P = 0.05). However, at logistic regression analysis, h-Hcy was not an independent predictor of 1-year mortality (OR 1.87 [95% CI 0.8-4.2]; P = 0.13).Our data suggest h-Hcy in IE is common, is related to a worse renal function, and may be a marker of cardiac dysfunction rather than infection. H-Hcy does not appear to favor IE vegetation formation or its symptomatic embolic complications.

A combined deficiency of tissue factor and PAR-4 is associated with fatal pulmonary hemorrhage in mice

INTRODUCTION

Mice with a complete absence of tissue factor (TF) die during embryonic development whereas mice with low levels of TF (Low-TF mice) survive to adulthood. Low-TF mice exhibit spontaneous hemorrhage in various organs, including the lung. In contrast, mice can survive without protease-activated receptor (PAR)-4, which is the major thrombin receptor on mouse platelets. We determined the effect of combining a deficiency PAR-4 (primary hemostasis) with a deficiency in TF (secondary hemostasis) on embryonic development and survival of adult mice.

MATERIALS AND METHODS

Low-TF mice (mTF^-/-, hTF^+/+) were crossed with PAR-4^-/- mice to generate heterozygous mice (mTF^+/-, hTF^+/-, PAR-4^+/-). These mice were intercrossed to generate Low-TF mice lacking PAR-4. Mice surviving to wean were genotyped and survival was monitored for 6months.

RESULTS

We observed the expected number of Low-TF,PAR-4^-/- mice at wean indicating survival in utero and after birth. However, an absence of PAR-4 was associated with premature death of all Low-TF,PAR-4^-/- mice in the 6month observational period. This compares with 40% death of the Low-TF,PAR-4^+/+ mice (p=0.003). Low-TF,PAR-4^+/- mice had an intermediate phenotype with 55% of the mice dying within 6months. The primary cause of mortality of Low-TF,PAR-4^-/- mice was pulmonary hemorrhage.

CONCLUSIONS

Low-TF,PAR-4^-/- mice survive into adulthood, but combining a deficiency of primary hemostasis (PAR-4 deficiency) with secondary hemostasis (low levels of TF) leads to premature death primarily due to pulmonary hemorrhage.

Endothelium and the brain in CNS lupus

Central nervous system (CNS) involvement in systemic lupus erythematosus (SLE) is common and results in different clinical manifestations. Several pathogenic mechanisms have been suggested to play a rolein determiningsuch a varietyof clinicalsymptoms.The thrombophilicstateassociatedto the presence of antiphospholipidantibodies has been suggested to be responsible for a noninflammatory vasculopathywhichcauses clear ischaemiceventsas well as alterationsof the cerebralmicrocirculation that are likely associated to seizures, cognitive dysfunction or psychosis. Although less frequent, a true vasculitic process affecting cerebral circulation has also been reported. In both cases, brain endothelium does represent the target of the pathogenic mechanisms. Brain endothelial cells display peculiar functional and phenotypical characteristics in comparison with endothelial cells from other anatomical districts, raising the possibility that this might be the reason for its susceptibility in lupus disease. We review and present data suggesting that a higher and firmer expression of beta 2 glycoprotein I on endothelialcell membranes can be responsiblefor a selective damage/activation by circulating anti-beta 2 glycoprotein I, and that antiendothelial cell antibodies crossreact with brain endothelium and in some cases, specifically bind brain endothelial cells only in lupus patients with central nervous involvement.

Cerebral haemostasis and antiphospholipid antibodies

One of the major clinical concerns of the antiphospholipid syndrome (APS) is the propensity of antiphospholipid(aPL) antibodiesto cause thrombosis in both the large and small vessels of the brain. In this article, we review the current understandingof haemostasis in cerebral circulation and discuss this in the context of antiphospholipidantibodies. The systemic-defect-local-phenotypeparadox is of particular importance in this discussion. In this paradigm, a systemic defect in thrombosis and haemostasis leads to a localized pattern of thrombotic disease because the regional physiological variations in the several prothromboticand anticoagulantfactors and the defect interact so as to favour thrombosis at a particular site. One possible mechanism of initiation of thrombosis in APS is the activation of endothelialcells by aPL that could occur in the cerebral vessels and provoke thrombosis. We review the evidence from gene knockout mice, other animal models and human postmortem examination studies as to which pro- and antithrombotic mechanisms are effecting haemostasis in the cerebral circulation. We conclude that there are large deficits in the understanding of the regulation of haemostasis in the human brain. As a consequencethere is a lack of knowledgeabout the effect of aPL on cerebral endothelium and thrombosis. Recent developments in gene expression profiling may have an impact on our understandingof endothelialfunctionin the brain. More research is required.

Serum Amyloid A Activation of Inflammatory and Adhesion Molecules in Human Coronary Artery and Umbilical Vein Endothelial Cells

Inflammation is considered to be the driving force leading to atherogenic and atherosclerotic mechanisms. Increased levels of SAA predict the risk of coronary artery disease and even mortality from cardiovascular disease in humans. Recent animal and human studies have indicated that SAA plays a causal role in atherogenesis, although it is largely unclear how this occurs. The objectives of this study are to understand the role of SAA in activating possible atherogenic inflammatory responses in human coronary artery endothelial cells (HCAEC) and to compare them with human umbilical vein endothelial cells (HUVEC). Our hypothesis is that vein and artery endothelial cells have different expression patterns and levels, leading to differential inflammatory responses. HUVEC and HCAEC were grown in order to analyze the effects of SAA on endothelial expression of pro-inflammatory cytokines, such as IL-6, chemokines, such as IL-8, and adhesion molecules (s-ICAM, s-VCAM, E-selectin) by reverse transcription-PCR and ELISAs. We compared the dose responses of SAA between HUVEC and HCAEC. SAA activated both HUVEC and HCAEC pro-inflammatory factors in a dose-dependent manner. In comparison however, HCAEC showed a strikingly greater sensitivity to SAA, with a higher level of expression of all pro-inflammatory markers at much lower concentrations of SAA, and their much greater stimulation at higher SAA concentrations. SAA also generated a dose-dependent positive feedback response on its own mRNA expression in HCAEC as compared to HUVEC. In summary, there are distinct significant differences in the levels of inflammatory markers and adhesion molecules between HUVEC and HCAEC SAA induced dose responses that could potentially account for HCAEC greater susceptibility to inflammation and atherogenesis.

Disseminated intravascular coagulation

Disseminated intravascular coagulation (DIC) is an acquired syndrome characterized by widespread intravascular activation of coagulation that can be caused by infectious insults (such as sepsis) and non-infectious insults (such as trauma). The main pathophysiological mechanisms of DIC are inflammatory cytokine-initiated activation of tissue factor-dependent coagulation, insufficient control of anticoagulant pathways and plasminogen activator inhibitor 1-mediated suppression of fibrinolysis. Together, these changes give rise to endothelial dysfunction and microvascular thrombosis, which can cause organ dysfunction and seriously affect patient prognosis. Recent observations have pointed to an important role for extracellular DNA and DNA-binding proteins, such as histones, in the pathogenesis of DIC. The International Society on Thrombosis and Haemostasis (ISTH) established a DIC diagnostic scoring system consisting of global haemostatic test parameters. This scoring system has now been well validated in diverse clinical settings. The theoretical cornerstone of DIC management is the specific and vigorous treatment of the underlying conditions, and DIC should be simultaneously managed to improve patient outcomes. The ISTH guidance for the treatment of DIC recommends treatment strategies that are based on current evidence. In this Primer, we provide an updated overview of the pathophysiology, diagnosis and management of DIC and discuss the future directions of basic and clinical research in this field.

Enhanced Megakaryopoiesis and Platelet Activity in Hypercholesterolemic, B6-Ldlr-/-, Cdkn2a-Deficient Mice

BACKGROUND

Genome-wide association studies for coronary artery disease/myocardial infarction revealed a 58 kb risk locus on 9p21.3. Refined genetic analyses revealed unique haplotype blocks conferring susceptibility to atherosclerosis per se versus risk for acute complications in the presence of underlying coronary artery disease. The cell proliferation inhibitor locus, CDKN2A, maps just upstream of the myocardial infarction risk block, is at least partly regulated by the noncoding RNA, ANRIL, overlapping the risk block, and has been associated with platelet counts in humans. Thus, we tested the hypothesis that CDKN2A deficiency predisposes to increased platelet production, leading to increased platelet activation in the setting of hypercholesterolemia.

METHODS AND RESULTS

Platelet production and activation were measured in B6-Ldlr(-/-)Cdkn2a(+/-) mice and a congenic strain carrying the region of homology with the human 9p21.3/CDKN2A locus. The strains exhibit decreased expression of CDKN2A (both p16(INK4a) and p19(ARF)) but not CDKN2B (p15(INK4b)). Compared with B6-Ldlr(-/-) controls, both Cdkn2a-deficient strains exhibited increased platelet counts and bone marrow megakaryopoiesis. The platelet overproduction phenotype was reversed by treatment with cyclin-dependent kinase 4/6 inhibitor, PD0332991/palbociclib, that mimics the endogenous effect of p16(INK4a). Western diet feeding resulted in increased platelet activation, increased thrombin/antithrombin complex, and decreased bleeding times in Cdkn2a-deficient mice compared with controls.

CONCLUSIONS

Together, the data suggest that one or more Cdkn2a transcripts modulate platelet production and activity in the setting of hypercholesterolemia, amenable to pharmaceutical intervention. Enhanced platelet production and activation may predispose to arterial thrombosis, suggesting an explanation, at least in part, for the association of 9p21.3 and myocardial infarction.

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

Recently, platelets, neutrophils, and factor XII (FXII) have been implicated as important players in the pathophysiology of venous thrombosis. Their role became evident in mouse models in which surgical handling was used to provoke thrombosis. Inhibiting anticoagulation in mice by using small interfering RNA (siRNA) targeting Serpinc1 and Proc also results in a thrombotic phenotype, which is spontaneous (no additional triggers) and reproducibly results in clots in the large veins of the head and fibrin deposition in the liver. This thrombotic phenotype is fatal but can be fully rescued by thrombin inhibition. The mouse model was used in this study to investigate the role of platelets, neutrophils, and FXII. After administration of siRNAs targeting Serpinc1 and Proc, antibody-mediated depletion of platelets fully abrogated the clinical features as well as microscopic aspects in the head. This was corroborated by strongly reduced fibrin deposition in the liver. Whereas neutrophils were abundant in siRNA-triggered thrombotic lesions, antibody-mediated depletion of circulating Ly6G-positive neutrophils did not affect onset, severity, or thrombus morphology. In addition, absence of circulating neutrophils did not affect quantitative liver fibrin deposition. Remarkably, siRNA-mediated depletion of plasma FXII accelerated the onset of the clinical phenotype; mice were affected with more severe thrombotic lesions. To summarize, in this study, onset and severity of the thrombotic phenotype are dependent on the presence of platelets but not circulating neutrophils. Unexpectedly, FXII has a protective effect. This study challenges the proposed roles of neutrophils and FXII in venous thrombosis pathophysiology.

Venous and Arterial Thrombotic Events in Systemic Lupus Erythematosus

Objective.

The incidence of thrombosis in patients with systemic lupus erythematosus (SLE) is 25 to 50-fold higher than in the general population; we aimed to define the characteristics of venous thrombotic events (VTE) and arterial thrombotic events (ATE) to identify the patients at highest risk.

Methods.

The study included 219 patients with recent-onset SLE. At baseline, standardized medical history and laboratory tests were done. Followup visits occurred quarterly, and information about damage accrual, comorbidities, and cardiovascular risk factors was updated annually. Main outcome was development of TE after SLE diagnosis.

Results.

Thirty-five patients (16%) developed TE (27 VTE, 8 ATE) during 5.21 years of followup; incidence rate 31/1000 patient-years. Most events (57%) developed within the first year of diagnosis, and 69% were not associated with lupus anticoagulant (LAC), determined with 1 method. VTE developed earlier than ATE (2.0 vs 57.5 mos, p = 0.02). In the multivariate analysis, variables preceding VTE included cutaneous vasculitis, nephrotic syndrome, dose of prednisone, and LAC in combination with anti-RNP/Sm antibodies (p < 0.03). Patients with ATE were older (median age 44 vs 29 yrs, p = 0.04), smokers, and had hypertension, diabetes mellitus, dyslipidemia, at least 2 traditional risk factors, nephrotic syndrome, chronic damage, and a higher cumulative dose of prednisone (p < 0.05). LAC in combination with anti-RNP/Sm antibodies was associated with VTE and improved the accuracy for predicting it.

Conclusion.

Our study suggests that in SLE, VTE and ATE have different risk factors. Understanding these differences is helpful for identifying patients at highest risk. The use of LAC plus anti-RNP/Sm for predicting VTE deserves further study.

Retrospective comparison of thromboelastography results to postmortem evidence of thrombosis in critically ill dogs: 39 cases (2005-2010)

OBJECTIVE

To determine whether there is an association between thromboelastography (TEG) data and necropsy evidence of thrombosis in a cohort of critically ill dogs.

DESIGN

Retrospective study (2005-2010).

SETTING

University teaching hospital.

ANIMALS

Thirty-nine client-owned critically ill dogs for which TEG was performed within 7 days of complete necropsy.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Thrombi were found in 26 (67%) dogs. Spayed females (n = 20) were significantly more likely to have thrombosis (P = 0.0127). No significant association was found between presence of thrombosis and any TEG parameter, the calculated coagulation index, results of coagulation testing, type of vascular access, or clinical diagnosis. D-dimers were significantly higher in dogs with thrombosis (P = 0.0207) and a weak positive correlation was found between D-dimer value and number of sites of thrombosis (ρ = 0.18, P = 0.0045). Dogs with WBC > 16 × 10(3) /μL were more likely to have thrombosis compared to others (odds ratio 5.56, 95% confidence interval 1.2-25.7, P = 0.025).

CONCLUSIONS

This study found no association between any TEG parameter and the presence of thrombosis on postmortem examination.