Publications by authors named "Nigel S Key"

196 Publications

Development and application of global assays of hyper- and hypofibrinolysis.

Res Pract Thromb Haemost 2020 Jan 6;4(1):46-53. Epub 2019 Nov 6.

Department of Pathology and Laboratory Medicine University of North Carolina Chapel Hill North Carolina.

Numerous methods for evaluation of global fibrinolytic activity in whole blood or plasma have been proposed, with the majority based on tissue-type plasminogen activator (t-PA) addition to initiate fibrinolysis. We propose that such an approach is useful to reveal hypofibrinolysis, but t-PA concentrations should be kept to a minimum. In this paper, we describe a low-concentration t-PA plasma turbidity assay to evaluate several congenital factor deficiencies, including plasminogen activator inhibitor-1 (PAI-1) and plasminogen deficiency, as well as hemophilia A and B. In addition, we demonstrate a threshold dependency on endogenous PAI-1 levels. To assess endogenous hyperfibrinolysis, we suggest that assays that avoid t-PA addition are preferable, with assays based on euglobulin fractionation remaining a viable choice. We describe a euglobulin fraction clot lysis time (ECLT) assay with spectrophotometric readout and other modifications, and evaluate it as a tool to measure hyperfibrinolysis in inherited clotting factor deficiency states. We demonstrate that the ECLT is predominantly driven by residual amounts of PAI-1, t-PA, and α-antiplasmin. These assays should be further evaluated for the detection of hypo- or hyperfibrinolysis in acquired thrombotic or hemorrhagic disorders.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/rth2.12275DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6971323PMC
January 2020

Thrombin activation of PAR-1 contributes to microvascular stasis in mouse models of sickle cell disease.

Blood 2020 05;135(20):1783-1787

UNC Blood Research Center, Division of Hematology/Oncology, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC.

Vaso-occlusive crisis (VOC) is the primary cause of morbidity and hospitalization in sickle cell disease (SCD); however, only 4 therapies (hydroxyurea, l-glutamine, crizanlizumab, and voxeletor) are currently approved in SCD. These agents limit the duration, severity, and frequency of crises. Activation of coagulation is a hallmark of SCD. Studies in animal models of SCD have shown that coagulation contributes to the chronic inflammation and end-organ damage associated with the disease; however, it is unknown whether coagulation directly contributes to the microvascular stasis that causes VOC. Herein, we demonstrate that inhibition of tissue factor (TF) and the downstream coagulation proteases factor Xa and thrombin significantly attenuates heme-induced microvascular stasis in mouse models of VOC. Pharmacologic inhibition of the principal thrombin receptor, protease activated receptor-1 (PAR-1), as well as deficiency of PAR-1 in all nonhematopoietic cells, also reduces stasis in sickle mice. PAR-1 deficiency was associated with reduced endothelial von Willebrand factor expression, which has been shown to mediate microvascular stasis. In addition, TF inhibition reduces lung vaso-occlusion in sickle mice mediated by arteriolar neutrophil-platelet microemboli. In sum, these results suggest that prophylactic anticoagulation might attenuate the incidence of VOC.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1182/blood.2019003543DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7225686PMC
May 2020

Red blood cell microvesicles activate the contact system, leading to factor IX activation via 2 independent pathways.

Blood 2020 03;135(10):755-765

Department of Medicine.

Storage lesion-induced, red cell-derived microvesicles (RBC-MVs) propagate coagulation by supporting the assembly of the prothrombinase complex. It has also been reported that RBC-MVs initiate coagulation via the intrinsic pathway. To elucidate the mechanism(s) of RBC-MV-induced coagulation activation, the ability of storage lesion-induced RBC-MVs to activate each zymogen of the intrinsic pathway was assessed in a buffer system. Simultaneously, the thrombin generation (TG) assay was used to assess their ability to initiate coagulation in plasma. RBC-MVs directly activated factor XII (FXII) or prekallikrein, but not FXI or FIX. RBC-MVs initiated TG in normal pooled plasma and in FXII- or FXI-deficient plasma, but not in FIX-deficient plasma, suggesting an alternate pathway that bypasses both FXII and FXI. Interestingly, RBC-MVs generated FIXa in a prekallikrein-dependent manner. Similarly, purified kallikrein activated FIX in buffer and initiated TG in normal pooled plasma, as well as FXII- or FXI-deficient plasma, but not FIX-deficient plasma. Dual inhibition of FXIIa by corn trypsin inhibitor and kallikrein by soybean trypsin inhibitor was necessary for abolishing RBC-MV-induced TG in normal pooled plasma, whereas kallikrein inhibition alone was sufficient to abolish TG in FXII- or FXI-deficient plasma. Heating RBC-MVs at 60°C for 15 minutes or pretreatment with trypsin abolished TG, suggesting the presence of MV-associated proteins that are essential for contact activation. In summary, RBC-MVs activate both FXII and prekallikrein, leading to FIX activation by 2 independent pathways: the classic FXIIa-FXI-FIX pathway and direct kallikrein activation of FIX. These data suggest novel mechanisms by which RBC transfusion mediates inflammatory and/or thrombotic outcomes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1182/blood.2019001643DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7059516PMC
March 2020

Hemoglobin levels and coronary heart disease risk by age, race, and sex in the reasons for geographic and racial differences in stroke study (REGARDS).

Am J Hematol 2020 03 22;95(3):258-266. Epub 2019 Dec 22.

Department of Pathology and Laboratory Medicine, Larner College of Medicine at the University of Vermont, Burlington, Vermont.

Higher and lower hemoglobin concentrations are associated with coronary heart disease (CHD), but whether this risk is consistent across age, sex, and race is unclear. The Reasons for Geographic And Racial Differences in Stroke (REGARDS) study is an observational cohort study of 30 239 black, and white, adults aged 45 and older recruited 2003-7. Participants were included if they had hemoglobin measures, were CHD-free at baseline, and had all baseline variables. The primary outcome was incident CHD. Multivariable Cox proportional hazards models were used to estimate the hazard ratios (HR) and 95% confidence intervals (CI) for incident CHD by hemoglobin concentration. This was expressed as a continuous variable and divided into age-, sex-, and race-specific quintiles. The 16 332 participants were included, contributing 114 362 person-years of follow-up and 915 incident CHD events. The mean age was 63 years, 35% were male, 41% were black, and the mean baseline hemoglobin was 13.6 g/dL (SD 1.4). A significant non-linear association between hemoglobin and CHD was identified (P < .001). This association differed significantly by race (P = .025) but not by sex or age. In whites, the risk for incident CHD was higher in the lowest (HR 2.28, 95% CI 1.61, 3.33) and highest (HR 1.94, 95% CI 1.35, 2.79) hemoglobin quintiles relative to the third quintile. For blacks, only those in the lowest hemoglobin quintile had an increased risk for incident CHD events (HR 1.70, 95% CI 1.20, 2.41). Hemoglobin is an independent risk factor for CHD in whites and blacks but with different hemoglobin concentrations conferring different risks.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/ajh.25703DOI Listing
March 2020

Etranacogene dezaparvovec (AMT-061 phase 2b): normal/near normal FIX activity and bleed cessation in hemophilia B.

Blood Adv 2019 11;3(21):3241-3247

Department of Pediatrics and Pathology, University of Michigan, Ann Arbor, MI.

Etranacogene dezaparvovec (AMT-061) is a recombinant AAV5 vector including a gene cassette containing the factor IX (FIX) Padua variant under the control of a liver-specific promoter. A phase 2b study was conducted to confirm that a single dose of 2 × 1013 genome copies per kilogram of etranacogene dezaparvovec will result in FIX activity ≥5% 6 weeks after dosing. Secondary end points included FIX activity at other time points, bleed frequency, FIX replacement, and safety. Etranacogene dezaparvovec was administered as a single IV infusion to 3 adults with severe to moderately severe hemophilia B. Before treatment, participants had low levels of preexisting neutralizing antibodies to AAV5. This article reports a planned 26-week interim assessment. At week 6, mean FIX activity was 31% (23.9%-37.8%), increasing to 47% (33.2%-57.0%) at 26 weeks, with 2 subjects exhibiting sustained activity >40%. Consistent with the FIX activity, etranacogene dezaparvovec was associated with a complete bleed cessation with no need for FIX replacement therapy up to 26 weeks. Etranacogene dezaparvovec was generally well tolerated. No clinically significant elevations in levels of liver enzymes or inflammatory markers were observed, and no use of corticosteroids related to treatment was required. In individuals with severe to moderately severe hemophilia B, etranacogene dezaparvovec resulted in clinically relevant increases in FIX activity, cessation of bleeds, and abrogation of the need for FIX replacement, despite the presence of preexisting anti-AAV5 neutralizing antibodies detected by using a highly sensitive luciferase assay. Consistency of results in the 3 participants supported an expanded evaluation of the safety/efficacy of etranacogene dezaparvovec in the HOPE-B (Health Outcomes With Padua Gene; Evaluation in Hemophilia-B) phase 3 trial. The current trial was registered at www.clinicaltrials.gov as #NCT03489291.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1182/bloodadvances.2019000811DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6855101PMC
November 2019

Quantitative HLA-class-II/factor VIII (FVIII) peptidomic variation in dendritic cells correlates with the immunogenic potential of therapeutic FVIII proteins in hemophilia A.

J Thromb Haemost 2020 01;18(1):201-216

South Texas Diabetes and Obesity Institute, University of Texas Rio Grande Valley, Brownsville, Texas.

Background: Plasma-derived (pd) or recombinant (r) therapeutic factor VIII proteins (FVIIIs) are infused to arrest/prevent bleeding in patients with hemophilia A (PWHA). However, FVIIIs are neutralized if anti-FVIII-antibodies (inhibitors) develop. Accumulating evidence suggests that pdFVIIIs with von Willebrand factor (VWF) are less immunogenic than rFVIIIs and that distinct rFVIIIs are differentially immunogenic. Since inhibitor development is T-helper-cell-dependent, human leukocyte antigen (HLA)-class-II (HLAcII) molecules constitute an important early determinant.

Objectives: Use dendritic cell (DC)-protein processing/presentation assays with mass-spectrometric and peptide-proteomic analyses to quantify the DP-bound, DQ-bound, and DR-bound FVIII-derived peptides in individual HLAcII repertoires and compare the immunogenic potential of six distinct FVIIIs based on their measured peptide counts.

Patients/methods: Monocyte-derived DCs from normal donors and/or PWHA were cultured with either: Mix-rFVIII, a VWF-free equimolar mixture of a full-length (FL)-rFVIII [Advate (Takeda)] and four distinct B-domain-deleted (BDD)-rFVIIIs [Xyntha (Pfizer), NovoEight (Novo-Nordisk), Nuwiq (Octapharma), and Afstyla (CSL Behring GmBH)]; a pdFVIII + pdVWF [Beriate (CSL Behring GmBH)]; Advate ± pdVWF; Afstyla ± pdVWF; and Xyntha + pdVWF.

Results: We showed that (i) Beriate had a significantly lower immunogenic potential than Advate ± pdVWF, Afstyla - pdVWF, and Mix-rFVIII; (ii) distinct FVIIIs differed significantly in their immunogenic potential in that, in addition to (i), Afstyla + pdVWF had a significantly lower immunogenic potential than Beriate, while the immunogenic potential of Beriate was not significantly different from that of Xyntha + pdVWF; and (iii) rFVIIIs with pdVWF had significantly lower immunogenic potentials than the same rFVIIIs without pdVWF.

Conclusions: Our results provide HLAcII peptidomic level explanations for several important clinical observations/issues including the differential immunogenicity of distinct FVIIIs and the role of HLAcII genetics in inhibitor development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/jth.14647DOI Listing
January 2020

Thirty-year risk of ischemic stroke in individuals with sickle cell trait and modification by chronic kidney disease: The atherosclerosis risk in communities (ARIC) study.

Am J Hematol 2019 12 10;94(12):1306-1313. Epub 2019 Sep 10.

Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.

Sickle cell trait (SCT) has been associated with hypercoagulability, chronic kidney disease (CKD), and ischemic stroke. Whether concomitant CKD modifies long-term ischemic stroke risk in individuals with SCT is uncertain. We analyzed data from 3602 genotyped black adults (female = 62%, mean baseline age = 54 years) who were followed for a median 26 years by the Atherosclerosis Risk in Communities Study. Ischemic stroke was verified by physician review. Associations between SCT and ischemic stroke were analyzed using repeat-events Cox regression, adjusted for potential confounders. SCT was identified in 236 (7%) participants, who more often had CKD at baseline than noncarriers (18% vs 13%, P = .02). Among those with CKD, elevated factor VII activity was more prevalent with SCT genotype (36% vs 22%; P = .05). From 1987-2017, 555 ischemic strokes occurred in 436 individuals. The overall hazard ratio of ischemic stroke associated with SCT was 1.31 (95% CI: 0.95-1.80) and was stronger in participants with concomitant CKD (HR = 2.18; 95% CI: 1.16-4.12) than those without CKD (HR = 1.09; 95% CI: 0.74-1.61); P for interaction = .04. The hazard ratio of composite ischemic stroke and/or death associated with SCT was 1.20 (95% CI: 1.01-1.42) overall, 1.44 (95% CI: 1.002-2.07) among those with CKD, and 1.15 (95% CI: 0.94-1.39) among those without CKD; P for interaction = .18. The long-term risk of ischemic stroke associated with SCT relative to noncarrier genotype appears to be modified by concomitant CKD.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/ajh.25615DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6858511PMC
December 2019

Association of sickle cell trait with measures of cognitive function and dementia in African Americans.

eNeurologicalSci 2019 Sep 22;16:100201. Epub 2019 Jul 22.

Aflac Cancer and Blood Disorder Center of Children's Healthcare of Atlanta, Emory Department of Pediatrics, Atlanta, GA, United States of America.

Objective: The incidence and prevalence of cognitive decline and dementia are significantly higher among African Americans compared with non-Hispanic Whites. The aim of this study was to determine whether inheritance of the sickle cell trait (SCT) i.e. heterozygosity for the sickle cell mutation increases the risk of cognitive decline or dementia Among African Americans.

Methods: We studied African American participants enrolled in the Atherosclerosis Risk in Communities study. SCT genotype at baseline and outcome data from cognitive assessments at visits 2, 4 and 5, and an MRI performed at visit 5 were analyzed for the association between SCT and risk of cognitive impairment and/or dementia.

Results: There was no significant difference in risk factors profile between participants with SCT ( = 176) and those without SCT ( = 2532). SCT was not independently associated with a higher prevalence of global or domain-specific cognitive impairment at baseline or with more rapid cognitive decline. Participants with SCT had slightly lower incidence of dementia (HR = 0.63 [0.38, 1.05]). On the other hand, SCT seems to interact with the apolipoprotein E ε4 risk allele resulting in poor performance on digit symbol substitution test at baseline (z-score = -0.08, P = 0.05) and over time (z-score = -0.12, P = 0.04); and with diabetes mellitus leading to a moderately increased risk of dementia (HR = 2.06 [0.89, 4.78], P = 0.01).

Conclusions: SCT was not an independent risk factor for prevalence or incidence of cognitive decline or dementia, although it may interact with and modify other putative risk factors for cognitive decline and dementia.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ensci.2019.100201DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6661502PMC
September 2019

Venous Thromboembolism Prophylaxis and Treatment in Patients With Cancer: ASCO Clinical Practice Guideline Update.

J Clin Oncol 2020 02 5;38(5):496-520. Epub 2019 Aug 5.

Hospital Papa Giovanni XXIII, Bergamo; and University of Milan Bicocca, Milan, Italy.

Purpose: To provide updated recommendations about prophylaxis and treatment of venous thromboembolism (VTE) in patients with cancer.

Methods: PubMed and the Cochrane Library were searched for randomized controlled trials (RCTs) and meta-analyses of RCTs published from August 1, 2014, through December 4, 2018. ASCO convened an Expert Panel to review the evidence and revise previous recommendations as needed.

Results: The systematic review included 35 publications on VTE prophylaxis and treatment and 18 publications on VTE risk assessment. Two RCTs of direct oral anticoagulants (DOACs) for the treatment of VTE in patients with cancer reported that edoxaban and rivaroxaban are effective but are linked with a higher risk of bleeding compared with low-molecular-weight heparin (LMWH) in patients with GI and potentially genitourinary cancers. Two additional RCTs reported on DOACs for thromboprophylaxis in ambulatory patients with cancer at increased risk of VTE.

Recommendations: Changes to previous recommendations: Clinicians may offer thromboprophylaxis with apixaban, rivaroxaban, or LMWH to selected high-risk outpatients with cancer; rivaroxaban and edoxaban have been added as options for VTE treatment; patients with brain metastases are now addressed in the VTE treatment section; and the recommendation regarding long-term postoperative LMWH has been expanded. Re-affirmed recommendations: Most hospitalized patients with cancer and an acute medical condition require thromboprophylaxis throughout hospitalization. Thromboprophylaxis is not routinely recommended for all outpatients with cancer. Patients undergoing major cancer surgery should receive prophylaxis starting before surgery and continuing for at least 7 to 10 days. Patients with cancer should be periodically assessed for VTE risk, and oncology professionals should provide patient education about the signs and symptoms of VTE.Additional information is available at www.asco.org/supportive-care-guidelines.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1200/JCO.19.01461DOI Listing
February 2020

Prolonged Remission of Cancer of Unknown Primary following Initiation of Eculizumab Therapy for Paroxysmal Nocturnal Hemoglobinuria.

Case Rep Hematol 2019 2;2019:2587597. Epub 2019 Jul 2.

Department of Medicine, Division of Hematology/Oncology, University of North Carolina, Chapel Hill, NC, USA.

We report the case of a 64-year-old woman who presented with cancer of unknown primary treated with carboplatin and paclitaxel, followed by maintenance erlotinib. Her chemotherapy regimen was discontinued due to the development of profound hemolysis that was later identified to be due to paroxysmal nocturnal hemoglobinuria (PNH). She was started on a complement inhibitory antibody, eculizumab 900 mg every 2 weeks, with marked suppression of hemolysis. Eight years after diagnosis of cancer, the patient remains on eculizumab with no signs of cancer recurrence on regular imaging. Regardless of whether the co-occurrence of cancer and PNH was any more than coincidental in this patient, the uniqueness of the case is emphasized by the remarkable and sustained response of not only PNH but also possibly the associated cancer to eculizumab.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1155/2019/2587597DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6636445PMC
July 2019

The relationship between pancreatic cancer and hypercoagulability: a comprehensive review on epidemiological and biological issues.

Br J Cancer 2019 08 22;121(5):359-371. Epub 2019 Jul 22.

Division of Haematology/Oncology, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.

It has long been recognised that pancreatic cancer induces a hypercoagulable state that may lead to clinically apparent thrombosis. Although the relationship between pancreatic cancer and hypercoagulability is well described, the underlying pathological mechanism(s) and the interplay between these pathways remain a matter of intensive study. This review summarises existing data on epidemiology and pathogenesis of thrombotic complications in pancreatic cancer with a particular emphasis on novel pathophysiological pathways. Pancreatic cancer is characterised by high tumoural expression of tissue factor, activation of leukocytes with the release of neutrophil extracellular traps, the dissemination of tumour-derived microvesicles that promote hypercoagulability and increased platelet activation. Furthermore, other coagulation pathways probably contribute to these processes, such as those that involve heparanase, podoplanin and hypofibrinolysis. In the era in which heparin and its derivatives-the currently recommended therapy for cancer-associated thrombosis-might be superseded by direct oral anticoagulants, novel data from mouse models of cancer-associated thrombosis suggest the possibility of future personalised therapeutic approaches. In this dynamic era for cancer-associated thrombosis, the discovery of novel prothrombotic and proinflammatory mechanisms will potentially uncover pharmacological targets to prevent and treat thrombosis without adversely affecting haemostasis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41416-019-0510-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6738049PMC
August 2019

How to discuss gene therapy for haemophilia? A patient and physician perspective.

Haemophilia 2019 Jul 21;25(4):545-557. Epub 2019 May 21.

Sheffield Haemophilia and Thrombosis Centre, Royal Hallamshire Hospital, Sheffield, UK.

Gene therapy has the potential to revolutionise treatment for patients with haemophilia and is close to entering clinical practice. While factor concentrates have improved outcomes, individuals still face a lifetime of injections, pain, progressive joint damage, the potential for inhibitor development and impaired quality of life. Recently published studies in adeno-associated viral (AAV) vector-mediated gene therapy have demonstrated improvement in endogenous factor levels over sustained periods, significant reduction in annualised bleed rates, lower exogenous factor usage and thus far a positive safety profile. In making the shared decision to proceed with gene therapy for haemophilia, physicians should make it clear that research is ongoing and that there are remaining evidence gaps, such as long-term safety profiles and duration of treatment effect. The eligibility criteria for gene therapy trials mean that key patient groups may be excluded, eg children/adolescents, those with liver or kidney dysfunction and those with a prior history of factor inhibitors or pre-existing neutralising AAV antibodies. Gene therapy offers a life-changing opportunity for patients to reduce their bleeding risk while also reducing or abrogating the need for exogenous factor administration. Given the expanding evidence base, both physicians and patients will need sources of clear and reliable information to be able to discuss and judge the risks and benefits of treatment.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/hae.13769DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6852207PMC
July 2019

Peptides identified on monocyte-derived dendritic cells: a marker for clinical immunogenicity to FVIII products.

Blood Adv 2019 05;3(9):1429-1440

Hemostasis Branch, Division of Plasma Protein Therapeutics, Office of Tissues and Advanced Therapeutics, Center for Biologics Evaluation and Research, US Food and Drug Administration, Silver Spring, MD.

The immunogenicity of protein therapeutics is an important safety and efficacy concern during drug development and regulation. Strategies to identify individuals and subpopulations at risk for an undesirable immune response represent an important unmet need. The major histocompatibility complex (MHC)-associated peptide proteomics (MAPPs) assay directly identifies the presence of peptides derived from a specific protein therapeutic on a donor's MHC class II (MHC-II) proteins. We applied this technique to address several questions related to the use of factor VIII (FVIII) replacement therapy in the treatment of hemophilia A (HA). Although >12 FVIII therapeutics are marketed, most fall into 3 categories: (i) human plasma-derived FVIII (pdFVIII), (ii) full-length (FL)-recombinant FVIII (rFVIII; FL-rFVIII), and (iii) B-domain-deleted rFVIII. Here, we investigated whether there are differences between the FVIII peptides found on the MHC-II proteins of the same individual when incubated with these 3 classes. Based on several observational studies and a prospective, randomized, clinical trial showing that the originally approved rFVIII products may be more immunogenic than the pdFVIII products containing von Willebrand factor (VWF) in molar excess, it has been hypothesized that the pdFVIII molecules yield/present fewer peptides (ie, potential T-cell epitopes). We have experimentally tested this hypothesis and found that dendritic cells from HA patients and healthy donors present fewer FVIII peptides when administered pdFVIII vs FL-rFVIII, despite both containing the same molar VWF excess. Our results support the hypothesis that synthesis of pdFVIII under physiological conditions could result in reduced heterogeneity and/or subtle differences in structure/conformation which, in turn, may result in reduced FVIII proteolytic processing relative to FL-rFVIII.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1182/bloodadvances.2018030452DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6517663PMC
May 2019

Neutrophils and neutrophil extracellular traps enhance venous thrombosis in mice bearing human pancreatic tumors.

Haematologica 2020 01 2;105(1):218-225. Epub 2019 May 2.

Department of Medicine, Division of Hematology and Oncology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA

Pancreatic cancer is associated with a high incidence of venous thromboembolism. Neutrophils have been shown to contribute to thrombosis in part by releasing neutrophil extracellular traps (NET). A recent study showed that increased plasma levels of the NET biomarker, citrullinated histone H3 (H3Cit), are associated with venous thromboembolism in patients with pancreatic and lung cancer but not in those with other types of cancer, including breast cancer. In this study, we examined the contribution of neutrophils and NET to venous thrombosis in nude mice bearing human pancreatic tumors. We found that tumor-bearing mice had increased circulating neutrophil counts and levels of granulocyte-colony stimulating factor, neutrophil elastase, H3Cit and cell-free DNA compared with controls. In addition, thrombi from tumor-bearing mice contained increased levels of the neutrophil marker Ly6G, as well as higher levels of H3Cit and cell-free DNA. Thrombi from tumor-bearing mice also had denser fibrin with thinner fibers consistent with increased thrombin generation. Importantly, either neutrophil depletion or administration of DNase I reduced the thrombus size in tumor-bearing but not in control mice. Our results, together with clinical data, suggest that neutrophils and NET contribute to venous thrombosis in patients with pancreatic cancer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3324/haematol.2019.217083DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6939515PMC
January 2020

Efficacy, safety, and pharmacokinetics of emicizumab prophylaxis given every 4 weeks in people with haemophilia A (HAVEN 4): a multicentre, open-label, non-randomised phase 3 study.

Lancet Haematol 2019 Jun 16;6(6):e295-e305. Epub 2019 Apr 16.

Hospital Universitario La Paz, Autónoma University, Madrid, Spain.

Background: Emicizumab, a subcutaneously administered, humanised, bispecific, monoclonal antibody, is approved to treat people with haemophilia A of all ages with and without coagulation factor VIII (FVIII) inhibitors. HAVEN 4 assessed emicizumab prophylaxis administered as one dose every 4 weeks in adults and adolescents with haemophilia A, regardless of FVIII inhibitor status.

Methods: In this phase 3, multicentre, open-label, two-stage study, patients aged 12 years and older with severe congenital haemophilia A (<1% of normal FVIII activity in blood) or haemophilia A with FVIII inhibitors, undergoing treatment with either FVIII concentrates or bypassing agents were recruited from three sites in Japan and Spain for a run-in cohort, and from 17 sites in Australia, Belgium, Japan, Poland, Spain, and the USA for a subsequent expansion cohort. Participants in the run-in and expansion cohorts were given emicizumab subcutaneously 6 mg/kg every 4 weeks for 24 weeks or more; for patients in the expansion cohort this regimen was preceded by four loading doses of 3 mg/kg once weekly. In the run-in cohort, we assessed pharmacokinetics after single and multiple (every 4 weeks) subcutaneous administration of 6 mg/kg emicizumab and safety. In the expansion cohort, the efficacy endpoint was efficacy of prophylactic emicizumab in maintaining adequate bleed prevention, assessed in all patients who received at least one dose of emicizumab and reported as annualised bleed rates for treated bleeds, all bleeds (treated and untreated), treated spontaneous bleeds, treated joint bleeds, and treated target joint bleeds. Safety was assessed in all participants given emicizumab. This study is registered with ClinicalTrials.gov, number NCT03020160, and is ongoing.

Findings: Between Jan 30, 2017, and Feb 27, 2017, seven patients were enrolled into the initial run-in cohort, which confirmed the expected pharmacokinetic profile and safety of the regimen based on model-based simulations, providing sufficient evidence for opening of the expansion cohort (n=41), which was recruited and enrolled between May 24, 2017, and June 30, 2017. The annualised rate of treated bleeds was 2·4 (95% CI 1·4-4·3). 23 (56·1%; 95% CI 39·7-71·5) of 41 reported no treated bleeds and 37 (90%; 76·9-97·3) reported zero to three treated bleeds. The annualised bleed rate was 4·5 (95% CI 3·1-6·6) for all bleeds, 0·6 (0·3-1·5), for treated spontaneous bleeds, 1·7 (0·8-3·7) for treated joint bleeds, and 1·0 (0·3-3·3) for treated target joint bleeds. The most frequent treatment-related adverse event was injection-site reaction (nine [22%] of 41 patients). We observed no thrombotic events or development of de-novo antidrug antibodies with neutralising potential or FVIII inhibitors.

Interpretation: Emicizumab given once every 4 weeks showed clinically meaningful bleed control while being well tolerated. This regimen could improve patient care by decreasing treatment burden and increasing adherence to effective prophylaxis, potentially decreasing the development of secondary complications for people with haemophilia A.

Funding: F Hoffmann-La Roche and Chugai Pharmaceutical.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/S2352-3026(19)30054-7DOI Listing
June 2019

Red blood cells modulate structure and dynamics of venous clot formation in sickle cell disease.

Blood 2019 06 5;133(23):2529-2541. Epub 2019 Apr 5.

Division of Hematology/Oncology, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC.

Sickle cell disease (SCD) is associated with chronic activation of coagulation and an increased risk of venous thromboembolism. Erythrocyte sickling, the primary pathologic event in SCD, results in dramatic morphological changes in red blood cells (RBCs) because of polymerization of the abnormal hemoglobin. We used a mouse model of SCD and blood samples from sickle patients to determine if these changes affect the structure, properties, and dynamics of sickle clot formation. Sickling of RBCs and a significant increase in fibrin deposition were observed in venous thrombi formed in sickle mice. During ex vivo clot contraction, the number of RBCs extruded from sickle whole blood clots was significantly reduced compared with the number released from sickle cell trait and nonsickle clots in both mice and humans. Entrapment of sickled RBCs was largely factor XIIIa-independent and entirely mediated by the platelet-free cellular fraction of sickle blood. Inhibition of phosphatidylserine, but not administration of antisickling compounds, increased the number of RBCs released from sickle clots. Interestingly, whole blood, but not plasma clots from SCD patients, was more resistant to fibrinolysis, indicating that the cellular fraction of blood mediates resistance to tissue plasminogen activator. Sickle trait whole blood clots demonstrated an intermediate phenotype in response to tissue plasminogen activator. RBC exchange in SCD patients had a long-lasting effect on normalizing whole blood clot contraction. Furthermore, RBC exchange transiently reversed resistance of whole blood sickle clots to fibrinolysis, in part by decreasing platelet-derived PAI-1. These properties of sickle clots may explain the increased risk of venous thromboembolism observed in SCD.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1182/blood.2019000424DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6557624PMC
June 2019

Neutrophils: back in the thrombosis spotlight.

Blood 2019 05 21;133(20):2186-2197. Epub 2019 Mar 21.

Department of Medicine.

Reactive and clonal neutrophil expansion has been associated with thrombosis, suggesting that neutrophils play a role in this process. However, although there is no doubt that activated monocytes trigger coagulation in a tissue factor-dependent manner, it remains uncertain whether stimulated neutrophils can also directly activate coagulation. After more than a decade of debate, it is now largely accepted that normal human neutrophils do not synthetize tissue factor, the initiator of the extrinsic pathway of coagulation. However, neutrophils may passively acquire tissue factor from monocytes. Recently, the contact system, which initiates coagulation via the intrinsic pathway, has been implicated in the pathogenesis of thrombosis. After the recent description of neutrophil extracellular trap (NET) release by activated neutrophils, some animal models of thrombosis have demonstrated that coagulation may be enhanced by direct NET-dependent activation of the contact system. However, there is currently no consensus on how to assess or quantify NETosis in vivo, and other experimental animal models have failed to demonstrate a role for neutrophils in thrombogenesis. Nevertheless, it is likely that NETs can serve to localize other circulating coagulation components and can also promote vessel occlusion independent of fibrin formation. This article provides a critical appraisal of the possible roles of neutrophils in thrombosis and highlights some existing knowledge gaps regarding the procoagulant activities of neutrophil-derived extracellular chromatin and its molecular components. A better understanding of these mechanisms could guide future approaches to prevent and/or treat thrombosis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1182/blood-2018-10-862243DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7218731PMC
May 2019

Re-evaluation of hematocrit as a determinant of thrombotic risk in erythrocytosis.

Haematologica 2019 04 14;104(4):653-658. Epub 2019 Mar 14.

Division of Hematology and Hematologic Malignancies, University of Utah and Huntsman Cancer Center, Salt Lake City, UT, USA

Here we critically evaluate the role of elevated hematocrit as the principal determinant of thrombotic risk in polycythemia and erythrocytosis, defined by an expansion of red cell mass. Since red cell volume determination is no longer readily available, in clinical practice, polycythemia and erythrocytosis are defined by elevated hemoglobin and hematocrit. Thrombosis is common in Chuvash erythrocytosis and polycythemia vera. Although the increased thrombotic risk is assumed to be due to the elevated hematocrit and an associated increase in blood viscosity, thrombosis does not accompany most types of erythrocytosis. We review studies indicating that the occurrence of thrombosis in Chuvash erythrocytosis is independent of hematocrit, that the thrombotic risk is paradoxically increased by phlebotomy in Chuvash erythrocytosis, and that, when compared to chemotherapy, phlebotomy is associated with increased thrombotic risk in polycythemia vera. Inherited and environmental causes that lead to polycythemia and erythrocytosis are accompanied by diverse cellular changes that could directly affect thrombotic risk, irrespective of the elevated hematocrit. The pressing issue in these disorders is to define factors other than elevated hematocrit that determine thrombotic risk. Defining these predisposing factors in polycythemia and erythrocytosis should then lead to rational therapies and facilitate development of targeted interventions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3324/haematol.2018.210732DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6442963PMC
April 2019

Prevalence of inherited blood disorders and associations with malaria and anemia in Malawian children.

Blood Adv 2018 11;2(21):3035-3044

Department of Pediatrics and.

In sub-Saharan Africa, inherited causes of anemia are common, but data are limited regarding the geographical prevalence and coinheritance of these conditions and their overall contributions to childhood anemia. To address these questions in Malawi, we performed a secondary analysis of the 2015-2016 Malawi Micronutrient Survey, a nationally and regionally representative survey that estimated the prevalence of micronutrient deficiencies and evaluated both inherited and noninherited determinants of anemia. Children age 6 to 59 months were sampled from 105 clusters within the 2015-2016 Malawi Demographic Health Survey. Hemoglobin, ferritin, retinol binding protein, malaria, and inflammatory biomarkers were measured from venous blood. Molecular studies were performed using dried blood spots to determine the presence of sickle cell disease or trait, α-thalassemia trait, and glucose-6-phosphate dehydrogenase (G6PD) deficiency. Of 1279 eligible children, 1071 were included in the final analysis. Anemia, iron deficiency, and malaria were common, affecting 30.9%, 21.5%, and 27.8% of the participating children, respectively. α-Thalassemia trait was common (>40% of children demonstrating deletion of 1 [33.1%] or 2 [10.0%] α-globin genes) and associated with higher prevalence of anemia ( < .001). Approximately 20% of males had G6PD deficiency, which was associated with a 1.0 g/dL protection in hemoglobin decline during malaria infection ( = .02). These data document that inherited blood disorders are common and likely play an important role in the prevalence of anemia and malaria in Malawian children.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1182/bloodadvances.2018023069DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6234379PMC
November 2018

Advances in Clinical and Basic Science of Coagulation: Illustrated abstracts of the 9th Chapel Hill Symposium on Hemostasis.

Res Pract Thromb Haemost 2018 Jul 12;2(3):407-428. Epub 2018 Apr 12.

Blood Research Institute Blood Center of Wisconsin Milwaukee WI USA.

This 9th Symposium on Hemostasis is an international scientific meeting held biannually in Chapel Hill, North Carolina. The meeting is in large measure the result of the close friendship between the late Dr. Harold R. Roberts of UNC Chapel Hill and Dr. Ulla Hedner of Novo Nordisk. When Novo Nordisk was developing the hemophilia therapy that would become NovoSeven, they sponsored a series of meetings to understand the basic biology and clinical applications of factor VIIa. The first meeting in Chapel Hill was held April 4-6, 2002 with Dr. Roberts as the organizer. Over the years, the conference emphasis has expanded from discussions of factor VIIa and tissue factor to additional topics in hemostasis and thrombosis. This year's meeting includes presentations by internationally renowned speakers that discuss the state-of-the-art on an array of important topics, including von Willebrand factor, engineering advances, coagulation and disease, tissue factor biology, therapeutic advances, and basic clotting factor biology. Included in this review article are illustrated abstracts provided by our speakers, which highlight the main conclusions of each invited talk. This will be the first meeting without Dr. Roberts in attendance, yet his commitment to excellent science and his focus on turning science to patient care are pervasively reflected in the presentations by our speakers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/rth2.12095DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6046595PMC
July 2018

Red Blood Cell Adhesion to Heme-Activated Endothelial Cells Reflects Clinical Phenotype in Sickle Cell Disease.

Am J Hematol 2018 Jun 15. Epub 2018 Jun 15.

Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH, USA.

In sickle cell disease (SCD), 'disease severity' associates with increased RBC adhesion to quiescent endothelium, but the impact on activated endothelium is not known. Increased concentrations of free heme result from intravascular hemolysis in SCD. Heme is essential for aerobic metabolism, and plays an important role in numerous biological processes. Excess free heme induces reactive oxygen species generation and endothelial activation, which are associated with cardiovascular disorders including atherosclerosis, hypertension, and thrombosis. Here, we utilized an endothelialized microfluidic platform (Endothelium-on-a-chip) to assess adhesion of sickle hemoglobin-containing red blood cells (HbS RBCs), from adults with homozygous SCD, to heme-activated human endothelial cells (EC) in vitro. Confluent EC monolayers in microchannels were treated with pathophysiologically relevant levels of heme in order to simulate the highly hemolytic intravascular milieu seen in SCD. RBC adhesion to heme-activated ECs varied from subject to subject, and was associated with plasma markers of hemolysis (LDH) and reticulocytosis, thereby linking those RBCs that are most likely to adhere with those that are most likely to hemolyze. These results re-emphasize the critical contribution made by heterogeneous adhesive HbS RBCs to the pathophysiology of SCD. We found that adhesion of HbS RBCs to heme-activated ECs varied amongst individuals in the study population, and associated with biomarkers of hemolysis and inflammation, age, and a recent history of transfusion. Importantly, the microfluidic approach described herein holds promise as a clinically feasible Endothelium-on-a-chip platform with which to study complex heterocellular adhesive interactions in SCD. This article is protected by copyright. All rights reserved.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/ajh.25159DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6295270PMC
June 2018

A cross-sectional analysis of cardiovascular disease in the hemophilia population.

Blood Adv 2018 06;2(11):1325-1333

Bloodworks Northwest, Seattle, WA; and.

Men with hemophilia were initially thought to be protected from cardiovascular disease (CVD), but it is now clear that atherothrombotic events occur. The primary objective of the CVD in Hemophilia study was to determine the prevalence of CVD and CVD risk factors in US older men with moderate and severe hemophilia and to compare findings with those reported in age-comparable men in the Atherosclerosis Risk in Communities (ARIC) cohort. We hypothesized if lower factor levels are protective from CVD, we would see a difference in CVD rates between more severely affected and unaffected men. Beginning in October 2012, 200 patients with moderate or severe hemophilia A or B (factor VIII or IX level ≤ 5%), aged 54 to 73 years, were enrolled at 19 US hemophilia treatment centers. Data were collected from patient interview and medical records. A fasting blood sample and electrocardiogram (ECG) were obtained and assayed and read centrally. CVD was defined as any angina, any myocardial infarction by ECG or physician diagnosis, any self-reported nonhemorrhagic stroke or transient ischemic attack verified by physicians, or any history of coronary bypass graft surgery or coronary artery angioplasty. CVD risk factors were common in the population. Compared with men of similar age in the ARIC cohort, patients with hemophilia had significantly less CVD (15% vs 25.8%; < .001). However, on an individual patient level, CVD events occur and efforts to prevent cardiovascular events are warranted. Few men were receiving secondary prophylaxis with low-dose aspirin, despite published opinion that it can be used safely in this patient population.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1182/bloodadvances.2018018226DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5998925PMC
June 2018

Microparticles in sickle cell disease.

Clin Hemorheol Microcirc 2018 ;68(2-3):319-329

Department of Medicine, Division of Hematology/Oncology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.

Several pathophysiological pathways in sickle cell disease (SCD), the most prevalent hemoglobinopathy worldwide, result in activation of circulating blood cells and the release of submicron vesicles, so-called microparticles (MPs). MPs are candidate biomarkers in vascular disease that exhibit functional biological properties. Compared to healthy individuals, higher level of plasma MPs, mostly derived from platelets and red blood cells (RBC), has been repeatedly observed in SCD patients in their steady-state condition. In contrast, conflicting results have been obtained on the impact of SCD complications and hydroxyurea treatment on circulating MP concentrations, largely due to non-standardized pre- and analytical procedures. Several factors responsible for the increased release of MPs by RBC have been identified in SCD such as sickling/unsickling, oxidative stress and abnormal activity of RBC acid sphingomyelinase. Besides their well-known pro-coagulant effect, sickle RBC-derived MPs produced ex vivo can induce ROS production by endothelial cells and promote a pro-inflammatory and pro-adhesive phenotype that may lead to renal occlusion in SCD mice. However, the functional properties of circulating MPs in human sickle cell disease remain to be studied and fully characterized.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3233/CH-189014DOI Listing
May 2018

Nephrin as a biomarker of sickle cell glomerulopathy in Malawi.

Pediatr Blood Cancer 2018 06 7;65(6):e26993. Epub 2018 Feb 7.

Division of Hematology/Oncology, University of North Carolina, Chapel Hill, North Carolina.

Background: Glomerulopathy is an increasingly identified complication in young patients with sickle cell disease (SCD). Hyperfiltration and albuminuria followed by declining glomerular filtration rates and eventual end-stage renal disease (ESRD) is assumed to be the typical progression of glomerular disease. There are only a few reported biomarkers to identify early-stage renal disease in SCD.

Procedures: We detail the renal profile of 101 children with SCD in Malawi and propose a novel urinary biomarker for the identification of early renal disease.

Results: Among children with sickle cell anemia, 24.8% had a urine albumin-creatinine ratio of 30 mg/g or above. In univariate analysis, only patients with higher urinary nephrin, a urinary marker of glomerular injury, had significantly greater odds of having albuminuria. In multivariable analysis, nephrin remained significantly associated with albuminuria. A nephrin-creatinine ratio (NCR) cut-point of 622 ng/mg, the 50 percentile, was associated with a 45.8 times greater odds of having albuminuria in children with nephrinuria above this value. Further analysis revealed this urinary NCR cut-point to have 96% sensitivity, 64% specificity, 47% positive predictive value, and 98% negative predictive value for the presence of albuminuria.

Conclusions: These data suggest that a substantial number of children with SCD in Malawi have renal disease and could be at risk for worsening nephropathy and ESRD as they age. Our data suggest that urinary nephrin could be utilized as an early marker of glomerular disease in SCD.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/pbc.26993DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5911184PMC
June 2018

Effect of eptifibatide on inflammation during acute pain episodes in sickle cell disease.

Am J Hematol 2018 08 30;93(4):E99-E101. Epub 2018 Jan 30.

Division of Hematology and Oncology, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/ajh.25032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5926197PMC
August 2018

Antifibrinolytic Therapy and Perioperative Considerations.

Anesthesiology 2018 03;128(3):657-670

From the Division of Cardiothoracic Anesthesiology and Critical Care, Department of Anesthesiology, Duke University School of Medicine, Durham, North Carolina (J.H.L, Q.J.Q.); Institute of Anesthesiology, Heart and Diabetes Center North Rhine Westphalia, Bad Oeynhausen, Ruhr-University Bochum, Bochum, Germany (A.K.); Seton Dell Medical School Stroke Institute, Austin, Texas (T.J.M.); and the Department of Medicine, Division of Hematology/Oncology, University of North Carolina, Chapel Hill, North Carolina (N.S.K.).

Fibrinolysis is a physiologic component of hemostasis that functions to limit clot formation. However, after trauma or surgery, excessive fibrinolysis may contribute to coagulopathy, bleeding, and inflammatory responses. Antifibrinolytic agents are increasingly used to reduce bleeding, allogeneic blood administration, and adverse clinical outcomes. Tranexamic acid is the agent most extensively studied and used in most countries. This review will explore the role of fibrinolysis as a pathologic mechanism, review the different pharmacologic agents used to inhibit fibrinolysis, and focus on the role of tranexamic acid as a therapeutic agent to reduce bleeding in patients after surgery and trauma.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/ALN.0000000000001997DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5811331PMC
March 2018

Endothelial alterations in a canine model of immune thrombocytopenia.

Platelets 2019 28;30(1):88-97. Epub 2017 Nov 28.

h Department of Pathology and Laboratory Animal Medicine , University of North Carolina , Chapel Hill , NC , USA.

Bleeding heterogeneity amongst patients with immune thrombocytopenia (ITP) is poorly understood. Platelets play a role in maintaining endothelial integrity, and variable thrombocytopenia-induced endothelial changes may influence bleeding severity. Platelet-derived endothelial stabilizers and markers of endothelial integrity in ITP are largely underexplored. We hypothesized that, in a canine ITP model, thrombocytopenia would lead to alterations in the endothelial ultrastructure and that the Von Willebrand factor (vWF) would serve as a marker of endothelial injury associated with thrombocytopenia. Thrombocytopenia was induced in healthy dogs with an antiplatelet antibody infusion; control dogs received an isotype control antibody. Cutaneous biopsies were obtained prior to thrombocytopenia induction, at platelet nadir, 24 hours after nadir, and on platelet recovery. Cutaneous capillaries were assessed by electron microscopy for vessel thickness, the number of pinocytotic vesicles, the number of large vacuoles, and the number of gaps between cells. Pinocytotic vesicles are thought to represent an endothelial membrane reserve that can be used for repair of damaged endothelial cells. Plasma samples were assessed for vWF. ITP dogs had significantly decreased pinocytotic vesicle numbers compared to control dogs (P = 0.0357) and the increase in plasma vWF from baseline to 24 hours correlated directly with the endothelial large vacuole score (R = 0.99103; P < 0.0001). This direct correlation between plasma vWF and the number of large vacuoles, representing the vesiculo-vacuolar organelle (VVO), a permeability structure, suggests that circulating vWF could serve as a biomarker for endothelial alterations and potentially a predictor of thrombocytopenic bleeding. Overall, our results indicate that endothelial damage occurs in the canine ITP model and variability in the degree of endothelial damage may account for differences in the bleeding phenotype among patients with ITP.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/09537104.2017.1378807DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6355380PMC
March 2019

Synthetic oligosaccharides can replace animal-sourced low-molecular weight heparins.

Sci Transl Med 2017 09;9(406)

Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599, USA.

Low-molecular weight heparin (LMWH) is used clinically to treat clotting disorders. As an animal-sourced product, LMWH is a highly heterogeneous mixture, and its anticoagulant activity is not fully reversible by protamine. Furthermore, the reliability of the LMWH supply chain is a concern for regulatory agencies. We demonstrate the synthesis of heparin dodecasaccharides (12-mers) at the gram scale. In vitro experiments demonstrate that the anticoagulant activity of the 12-mers could be reversed using protamine. One of these, labeled as 12-mer-1, reduced the size of blood clots in the mouse model of deep vein thrombosis and attenuated circulating procoagulant markers in the mouse model of sickle cell disease. An ex vivo experiment demonstrates that the anticoagulant activity of 12-mer-1 could be reversed by protamine. 12-mer-1 was also examined in a nonhuman primate model to determine its pharmacodynamic parameters. A 7-day toxicity study in a rat model showed no toxic effects. The data suggest that a synthetic homogeneous oligosaccharide can replace animal-sourced LMWHs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/scitranslmed.aan5954DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6231235PMC
September 2017

Analysis of anticoagulation strategies for venous thromboembolism during severe thrombocytopenia in patients with hematologic malignancies: a retrospective cohort.

Leuk Lymphoma 2017 11 9;58(11):2573-2581. Epub 2017 Apr 9.

a Department of Medicine, Division of Hematology/Oncology , University of North Carolina , Chapel Hill , NC , USA.

The safety and efficacy of anticoagulation for venous thromboembolism (VTE) at times of severe thrombocytopenia is unclear. In this retrospective study, we evaluated patients with hematologic malignancy and either (1) acute or chronic VTE on anticoagulation before platelet count dropped below 50 × 10/L or (2) acute VTE occurring while platelets were <50 × 10/L. In 78 eligible patients, the primary outcomes of time to recurrent VTE or clinically significant bleeding within 100 d were compared by management strategy. Bleeding occurred in 27% of patients receiving anticoagulation versus 3% when anticoagulation was held (IRR 10.1, 95% CI 1.5-432.6). Recurrent VTE occurred in 2% of patients receiving anticoagulation versus 15% when anticoagulation was held (IRR 0.17, 95% CI 0.0-1.51). Most bleeding occurred before day 31(11/13), but recurrent VTE mostly occurred after day 40 (5/6). Our findings suggest that temporarily withholding anticoagulation for VTE during severe thrombocytopenia in patients with hematologic malignancies might reduce adverse outcomes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/10428194.2017.1306644DOI Listing
November 2017