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Mathews N, Pluthero FG, Rand ML, Stain AM, Carcao M, Blanchette VS, Kahr WHA. Thromboelastography and thrombin generation assessments for pediatric severe hemophilia A patients are highly variable and not predictive of clinical phenotypes. Res Pract Thromb Haemost 2022; 6:e12800. [PMID: 36186102 PMCID: PMC9511091 DOI: 10.1002/rth2.12800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 07/02/2022] [Accepted: 07/23/2022] [Indexed: 11/24/2022] Open
Abstract
Background Severe hemophilia A (SHA) patients vary in severity of bleeding, arthropathy, and requirements for replacement factor VIII (FVIII). Baseline hemostatic activity assays using calibrated automated thrombography (CAT) and thromboelastography (TEG) may offer insights into the physiological basis of clinical heterogeneity. Objectives Use CAT and TEG to measure baseline hemostatic activity in a cohort of 30 pediatric SHA patients with available clinical data. Determine effect of contact activation inhibition with corn trypsin inhibitor (CTI). Assess heterogeneity among patients for baseline hemostatic activity and examine correlations between assay results and clinical parameters including FVIII dosing regimen, von Willebrand factor level, and Pettersson arthropathy score. Methods SHA blood after FVIII washout was subjected to TEG, and platelet‐rich (PRP) and platelet‐poor plasma was used for CAT assays. Varying concentrations of tissue factor (TF) were used. Statistical analysis examined relationships between assay results, and clinical parameters. Results CTI treatment was required to obtain TEG and CAT results representative of baseline hemostatic activity. Weak activity was observed in assays with low TF concentrations (0.5–2 pM), and most but not all samples approached normal activity levels at high TF concentrations (10–20 pM). A significant positive correlation was observed between results of TEG and CAT‐PRP assays. Correlations were not detected between hemostatic assay results and clinical parameters. Conclusions In vitro hemostatic assay results of samples containing platelets showed concordance. Assay results were not predictive of FVIII requirements or correlated with other clinical parameters. SHA patient heterogeneity is influenced by factors other than baseline hemostatic activity.
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Affiliation(s)
- Natalie Mathews
- Division of Haematology/Oncology Hospital for Sick Children Toronto Ontario Canada
| | - Fred G Pluthero
- Cell Biology Program Research Institute, Hospital for Sick Children Toronto Ontario Canada
| | - Margaret L Rand
- Division of Haematology/Oncology Hospital for Sick Children Toronto Ontario Canada.,Translational Medicine Program Hospital for Sick Children Toronto Ontario Canada.,Departments of Laboratory Medicine & Pathobiology Biochemistry, and Pediatrics, University of Toronto Toronto Ontario Canada
| | - Ann Marie Stain
- Division of Haematology/Oncology Hospital for Sick Children Toronto Ontario Canada
| | - Manuel Carcao
- Division of Haematology/Oncology Hospital for Sick Children Toronto Ontario Canada.,Department of Pediatrics University of Toronto Toronto Ontario Canada
| | - Victor S Blanchette
- Division of Haematology/Oncology Hospital for Sick Children Toronto Ontario Canada.,Department of Pediatrics University of Toronto Toronto Ontario Canada
| | - Walter H A Kahr
- Division of Haematology/Oncology Hospital for Sick Children Toronto Ontario Canada.,Cell Biology Program Research Institute, Hospital for Sick Children Toronto Ontario Canada.,Departments of Pediatrics and Biochemistry University of Toronto Toronto Ontario Canada
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2
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Yesudasan S, Wang X, Averett RD. Molecular dynamics simulations indicate that deoxyhemoglobin, oxyhemoglobin, carboxyhemoglobin, and glycated hemoglobin under compression and shear exhibit an anisotropic mechanical behavior. J Biomol Struct Dyn 2017; 36:1417-1429. [PMID: 28441918 DOI: 10.1080/07391102.2017.1323674] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We developed a new mechanical model for determining the compression and shear mechanical behavior of four different hemoglobin structures. Previous studies on hemoglobin structures have focused primarily on overall mechanical behavior; however, this study investigates the mechanical behavior of hemoglobin, a major constituent of red blood cells, using steered molecular dynamics (SMD) simulations to obtain anisotropic mechanical behavior under compression and shear loading conditions. Four different configurations of hemoglobin molecules were considered: deoxyhemoglobin (deoxyHb), oxyhemoglobin (HbO2), carboxyhemoglobin (HbCO), and glycated hemoglobin (HbA1C). The SMD simulations were performed on the hemoglobin variants to estimate their unidirectional stiffness and shear stiffness. Although hemoglobin is structurally denoted as a globular protein due to its spherical shape and secondary structure, our simulation results show a significant variation in the mechanical strength in different directions (anisotropy) and also a strength variation among the four different hemoglobin configurations studied. The glycated hemoglobin molecule possesses an overall higher compressive mechanical stiffness and shear stiffness when compared to deoxyhemoglobin, oxyhemoglobin, and carboxyhemoglobin molecules. Further results from the models indicate that the hemoglobin structures studied possess a soft outer shell and a stiff core based on stiffness.
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Affiliation(s)
- Sumith Yesudasan
- a School of Chemical, Materials, and Biomedical Engineering , College of Engineering, University of Georgia , 597 D.W. Brooks Drive, Athens , GA 30602 , USA
| | - Xianqiao Wang
- b School of Environmental, Civil, Agricultural and Mechanical Engineering , College of Engineering, University of Georgia , 712G Boyd Graduate Studies Research Center, Athens , GA 30602 , USA
| | - Rodney D Averett
- a School of Chemical, Materials, and Biomedical Engineering , College of Engineering, University of Georgia , 597 D.W. Brooks Drive, Athens , GA 30602 , USA
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3
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Adler M, Ivic S, Bodmer NS, Ten Cate H, Bachmann LM, Wuillemin WA, Nagler M. Thromboelastometry and Thrombelastography Analysis under Normal Physiological Conditions - Systematic Review. Transfus Med Hemother 2017; 44:78-83. [PMID: 28503123 DOI: 10.1159/000464297] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2017] [Accepted: 02/20/2017] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Studies investigating thromboelastometry or thrombelastography analyses in a physiological context are scattered and not easy to access. OBJECTIVE To systematically retrieve and describe published reports studying healthy subjects and targeting at the correlation of ROTEM® and TEG® measurements with conventional parameters of hemostasis. METHODS Systematic Review: Papers were searched in Medline, Scopus and the Science Citation Index database. Reference lists of included studies and of reviews were screened. To be included papers had to report ROTEM or TEG data on healthy subjects. Two reviewers screened papers for inclusion, read full texts of potentially relevant papers, and extracted data of included papers. RESULTS Searches identified 1,721 records of which 1,713 were either excluded immediately or after reading the full text. The remaining 8 studies enrolled 632 subjects. The association of conventional parameters of hemostasis with ROTEM and with TEG was investigated in one and two studies, respectively. Overall correlation was limited and ranged from 0.0 to 0.40 (total thrombus generation vs. fibrinogen; clotting time INTEM vs. activated partial thromboplastin time). CONCLUSIONS Studies assessing the relationship between thromboelastometry or thromboelastography analyses and conventional parameters of hemostasis in healthy subjects remains scarce, and correlations are limited. Further research is needed to understand the physiology of thromboelastometry and thromboelastography parameters.
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Affiliation(s)
- Marcel Adler
- Department of Hematology and Central Hematology Laboratory, Inselspital, Bern University Hospital, and Department of Clinical Research, University of Bern, Bern, Switzerland
| | - Sandra Ivic
- medignition Inc, Research Consultants, Zurich, Switzerland
| | | | - Hugo Ten Cate
- Laboratory of Clinical Thrombosis and Hemostasis, and Cardiovascular Research Institute, Maastricht University Medical Center, Maastricht, The Netherlands
| | | | - Walter A Wuillemin
- Division of Hematology and Central Hematology Laboratory, Luzerner Kantonsspital, University of Bern, Lucerne, Switzerland
| | - Michael Nagler
- Department of Hematology and Central Hematology Laboratory, Inselspital, Bern University Hospital, and Department of Clinical Research, University of Bern, Bern, Switzerland.,Division of Hematology and Central Hematology Laboratory, Luzerner Kantonsspital, University of Bern, Lucerne, Switzerland
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4
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Pike GN, Cumming AM, Thachil J, Hay CRM, Bolton-Maggs PHB, Burthem J. Evaluation of the use of rotational thromboelastometry in the assessment of FXI deficency. Haemophilia 2017; 23:449-457. [DOI: 10.1111/hae.13136] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/23/2016] [Indexed: 11/27/2022]
Affiliation(s)
- G. N. Pike
- Department of Haematology; Manchester Royal Infirmary; Central Manchester University Hospital NHS Trust; Manchester UK
- Institute of Cancer Sciences; The University of Manchester; Manchester UK
| | - A. M. Cumming
- Haematology Molecular Diagnostics Centre; Manchester Royal Infirmary; Central Manchester University Hospital NHS Trust; Manchester UK
| | - J. Thachil
- Department of Haematology; Manchester Royal Infirmary; Central Manchester University Hospital NHS Trust; Manchester UK
| | - C. R. M. Hay
- Department of Haematology; Manchester Royal Infirmary; Central Manchester University Hospital NHS Trust; Manchester UK
- Haematology Molecular Diagnostics Centre; Manchester Royal Infirmary; Central Manchester University Hospital NHS Trust; Manchester UK
| | - P. H. B. Bolton-Maggs
- The University of Manchester; Manchester UK
- SHOT Office; Manchester Blood Centre; Manchester UK
| | - J. Burthem
- Department of Haematology; Manchester Royal Infirmary; Central Manchester University Hospital NHS Trust; Manchester UK
- Institute of Cancer Sciences; The University of Manchester; Manchester UK
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Abstract
PURPOSE OF REVIEW There exists an imbalance between our understanding of the physiology of the blood coagulation process and the translation of this understanding into useful assays for clinical application. As technology advances, the capabilities for merging the two areas have become more attainable. Global assays have advanced our understanding of the dynamics of the blood coagulation process beyond end point assays and are at the forefront of implementation in the clinic. RECENT FINDINGS We will review recent advances in the main global assays with a focus on thrombin generation that have potential for clinical utility. These assays include direct (thrombogram, whole blood, purified systems) and indirect empirical measures of thrombin generation (thromboelastography) and mechanism-based computational models that use plasma composition data from individuals to generate thrombin generation profiles. SUMMARY Empirical thrombin generation assays (direct and indirect) and computational modeling of thrombin generation have greatly advanced our understanding of the hemostatic balance. Implementation of these types of assays and visualization approaches in the clinic will potentially provide a basis for the development of individualized patient care. Advances in both empirical and computational global assays have made the goal of predicting precrisis changes in an individual's hemostatic state one step closer.
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6
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Tran HTT, Sørensen B, Bjørnsen S, Pripp AH, Tjønnfjord GE, Andre Holme P. Monitoring bypassing agent therapy – a prospective crossover study comparing thromboelastometry and thrombin generation assay. Haemophilia 2014; 21:275-283. [DOI: 10.1111/hae.12570] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/21/2014] [Indexed: 01/24/2023]
Affiliation(s)
- H. T. T. Tran
- Research Institute of Internal Medicine Oslo University Hospital Oslo Norway
- Department of Haematology Oslo University Hospital Oslo Norway
- Institute of Clinical Medicine University of Oslo Oslo Norway
| | | | - S. Bjørnsen
- Research Institute of Internal Medicine Oslo University Hospital Oslo Norway
| | - A. H. Pripp
- Research Institute of Internal Medicine Oslo University Hospital Oslo Norway
- Department of Biostatistics and Epidemiology Oslo University Hospital Oslo Norway
| | - G. E. Tjønnfjord
- Department of Haematology Oslo University Hospital Oslo Norway
- Institute of Clinical Medicine University of Oslo Oslo Norway
| | - P. Andre Holme
- Research Institute of Internal Medicine Oslo University Hospital Oslo Norway
- Department of Haematology Oslo University Hospital Oslo Norway
- Institute of Clinical Medicine University of Oslo Oslo Norway
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7
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Hansson KM, Nielsen S, Elg M, Deinum J. The effect of corn trypsin inhibitor and inhibiting antibodies for FXIa and FXIIa on coagulation of plasma and whole blood. J Thromb Haemost 2014; 12:1678-86. [PMID: 25142753 DOI: 10.1111/jth.12707] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 08/10/2014] [Indexed: 11/30/2022]
Abstract
BACKGROUND Corn trypsin inhibitor (CTI), an inhibitor of FXIIa, is used to prevent plasma coagulation by contact activation, to specifically investigate tissue factor (TF)-initiated coagulation. OBJECTIVE In the present work the specificity of CTI for factor (F) XIIa is questioned. METHODS AND RESULTS In the commercial available plasma coagulation assays CTI was found to double activated partial thromboplastin time (APTT) at a plasma concentration of 7.3 ± 1.5 μm CTI (assay concentration 2.4 μm). No effect was found on the prothrombin time (PT) when high TF concentrations were used. Also, with specific antibodies for FXIIa and for FXIa only APTT was found to be extended but not PT. With specific enzyme assays using chromogenic substrates CTI was shown to be a strong inhibitor of FXIIa and a competitive inhibitor of FXIa with Ki = 8.1 ± 0.3 μm, without effect on the coagulation factors FVIIa, FIXa, FXa and thrombin. In thrombin generation and coagulation (free oscillation rheometry, FOR) assays, initiated with low TF concentrations, no effect of CTI (plasma concentrations of 4.4 and 13.6 μm CTI, 25 resp. 100 mg L(-1) in blood) was found with ≥ 1 pm TF. At ≤ 0.1 pm TF in the FOR whole blood assay the coagulation time (CT) concentration dependently increased while the plasma CT became longer than the observation time. CONCLUSION To avoid inhibition of FXIa and the thrombin feedback loop we recommend that for coagulation assays the concentration of CTI in blood should be below 20 mg L(-1) (1.6 μm) and in plasma below 3 μm.
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Affiliation(s)
- K M Hansson
- CVMD iMED, AstraZeneca R&D Mölndal, Mölndal, Sweden
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8
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Comparative response of platelet fV and plasma fV to activated protein C and relevance to a model of acute traumatic coagulopathy. PLoS One 2014; 9:e99181. [PMID: 24921658 PMCID: PMC4055642 DOI: 10.1371/journal.pone.0099181] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 05/12/2014] [Indexed: 12/31/2022] Open
Abstract
Background Acute traumatic coagulopathy (ATC) has been linked to an increase in activated protein C (aPC) from 40 pM in healthy individuals to 175 pM. aPC exerts its activity primarily through cleavage of active coagulation factor Va (fVa). Platelets reportedly possess fVa which is more resistant to aPC cleavage than plasma fVa; this work examines the hypothesis that normal platelets are sufficient to maintain coagulation in the presence of elevated aPC. Methods Coagulation responses of normal plasma, fV deficient plasma (fVdp), and isolated normal platelets in fVdp were conducted: prothrombin (PT) tests, turbidimetry, and thromboelastography (TEG), including the dose response of aPC on the samples. Results PT and turbidimetric assays demonstrate that normal plasma is resistant to aPC at doses much higher than those found in ATC. Additionally, an average physiological number of washed normal platelets (200,000 platelets/mm3) was sufficient to eliminate the anti-coagulant effects of aPC up to 10 nM, nearly two orders of magnitude above the ATC concentration and even the steady-state pharmacological concentration of human recombinant aPC, as measured by TEG. aPC also demonstrated no significant effect on clot lysis in normal plasma samples with or without platelets. Conclusions Although platelet fVa shows slightly superior resistance to aPC's effects compared to plasma fVa in static models, neither fVa is sufficiently cleaved in simulations of ATC or pharmacologically-delivered aPC to diminish coagulation parameters. aPC is likely a correlative indicator of ATC or may play a cooperative role with other activity altering products generated in ATC.
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9
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Abstract
BACKGROUND Viscoelastic measurements are frequently being used in clinical and research settings for a rapid assessment of the hemostatic processes of blood clot formation and degradation. These measurements are being performed on either of two instruments (TEG and ROTEM) using their proprietary reagents. Standardization between the instruments and the reagents has been lacking but is necessary to compare results across instruments. In this study, we perform a crossover analysis between the TEG and ROTEM instruments using proprietary reagents from each manufacturer. METHODS We tested three sets of reagents as follows: (1) in-tem and ex-tem (Tem International GmbH); (2) kaolin and RapidTEG (Haemonetics); (3) a well-characterized control recombinant tissue factor-phospholipid reagent. Blood was drawn from six healthy donors, and each reagent was run concurrently in the TEG and ROTEM instruments. The volume of commercial reagent and calcium used was adjusted for crossover measurements to maintain the same concentration of each reagent in the blood. The outputs of clot time, rate of clot formation, and maximum firmness of the clot of the ROTEM and the TEG tracings were evaluated. RESULTS The in-tem and RapidTEG reagents showed no disparity between instruments for any parameter. Significant differences between the instruments were found in the α angle and maximum firmness of the clot for ex-tem and kaolin reagents as well as in the clot time and maximum firmness of the clot for the recombinant tissue factor-phospholipid reagent. CONCLUSION Although significant differences were observed for some parameters, the magnitudes were small compared with the differences between tests or the normal range variation in parameter values observed for these tests. These findings indicate that the instruments are more interchangeable than previously reported.
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10
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de Laforcade A, Goggs R, Wiinberg B. Systematic evaluation of evidence on veterinary viscoelastic testing Part 3: Assay activation and test protocol. J Vet Emerg Crit Care (San Antonio) 2014; 24:37-46. [DOI: 10.1111/vec.12147] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 11/15/2013] [Indexed: 11/30/2022]
Affiliation(s)
- Armelle de Laforcade
- From the Department of Clinical Sciences; Cummings School of Veterinary Medicine; Tufts University; North Grafton MA
| | - Robert Goggs
- Department of Clinical Sciences; College of Veterinary Medicine; Cornell University; Ithaca NY, 14853
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11
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Goggs R, Brainard B, de Laforcade AM, Flatland B, Hanel R, McMichael M, Wiinberg B. Partnership on Rotational ViscoElastic Test Standardization (PROVETS): Evidence-based guidelines on rotational viscoelastic assays in veterinary medicine. J Vet Emerg Crit Care (San Antonio) 2014; 24:1-22. [DOI: 10.1111/vec.12144] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 11/15/2013] [Indexed: 11/30/2022]
Affiliation(s)
- Robert Goggs
- From the Department of Clinical Sciences; College of Veterinary Medicine; Cornell University; Ithaca NY 14853
| | - Benjamin Brainard
- Department of Small Animal Medicine & Surgery, College of Veterinary Medicine; University of Georgia; Athens GA 30602
| | - Armelle M. de Laforcade
- Department of Clinical Sciences; Tufts Cummings School of Veterinary Medicine; North Grafton MA 01536
| | - Bente Flatland
- Department of Pathobiology, College of Veterinary Medicine; University of Tennessee; Knoxville TN 37996
| | - Rita Hanel
- Department of Clinical Sciences, College of Veterinary Medicine; NC State University; Raleigh NC 27607
| | - Maureen McMichael
- Department of Veterinary Clinical Medicine, College of Veterinary Medicine; University of Illinois; Urbana IL 61801
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12
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Platelets do not express the oxidized or reduced forms of tissue factor. Biochim Biophys Acta Gen Subj 2013; 1840:1188-93. [PMID: 24361609 DOI: 10.1016/j.bbagen.2013.11.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 11/11/2013] [Accepted: 11/25/2013] [Indexed: 02/07/2023]
Abstract
BACKGROUND Expression of tissue factor (TF) antigen and activity in platelets is controversial and dependent upon the laboratory and reagents used. Two forms of TF were described: an oxidized functional form and a reduced nonfunctional form that is converted to the active form through the formation of an allosteric disulfide. This study tests the hypothesis that the discrepancies regarding platelet TF expression are due to differential expression of the two forms. METHODS Specific reagents that recognize both oxidized and reduced TF were used in flow cytometry of unactivated and activated platelets and western blotting of whole platelet lysates. TF-dependent activity measurements were used to confirm the results. RESULTS Western blotting analyses of placental TF demonstrated that, in contrast to anti-TF#5, which is directed against the oxidized form of TF, a sheep anti-human TF polyclonal antibody recognizes both the reduced and oxidized forms. Flow cytometric analyses demonstrated that the sheep antibody did not react with the surface of unactivated platelets or platelets activated with thrombin receptor agonist peptide, PAR-1. This observation was confirmed using biotinylated active site-blocked factor (F)VIIa: no binding was observed. Likewise, neither form of TF was detected by western blotting of whole platelet lysates with sheep anti-hTF. Consistent with these observations, no FXa or FIXa generation by FVIIa was detected at the surface of these platelets. Similarly, no TF-related activity was observed in whole blood using thromboelastography. CONCLUSION AND SIGNIFICANCE Platelets from healthy donors do not express either oxidized (functional) or reduced (nonfunctional) forms of TF.
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13
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Abstract
Computational models can offer an integrated view of blood clotting dynamics and may ultimately be instructive regarding an individual's risk of bleeding or clotting. Appropriately, developed and validated models could allow clinicians to simulate the outcomes of therapeutics and estimate risk of disease. Computational models that describe the dynamics of thrombin generation have been developed and have been used in combination with empirical studies to understand thrombin dynamics on a mechanistic basis. The translation of an individual's specific coagulation factor composition data using these models into an integrated assessment of hemostatic status may provide a route for advancing the long-term goal of individualized medicine. This review details the integrated approaches to understanding: (i) What is normal thrombin generation in individuals? (ii) What is the effect of normal range plasma composition variation on thrombin generation in pathologic states? (iii) Can disease progression or anticoagulation be followed by understanding the boundaries of normal thrombin generation defined by plasma composition? (iv) What are the controversies and limitations of current computational approaches? Progress in these areas can bring us closer to developing models that can be used to aid in identifying hemostatic risk.
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Affiliation(s)
- K Brummel-Ziedins
- Colchester Research Facility, University of Vermont, Colchester, VT 05446, USA.
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14
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Gissel M, Orfeo T, Foley JH, Butenas S. Effect of BAX499 aptamer on tissue factor pathway inhibitor function and thrombin generation in models of hemophilia. Thromb Res 2012; 130:948-55. [PMID: 22951415 DOI: 10.1016/j.thromres.2012.08.299] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Revised: 08/02/2012] [Accepted: 08/14/2012] [Indexed: 11/26/2022]
Abstract
INTRODUCTION In hemophilia, thrombin generation is significantly suppressed due to decreased factor (F)X activation. Clinical studies and experiments with transgenic mice have suggested that the severity of hemophilia is substantially reduced by tissue factor pathway inhibitor (TFPI) deficiency. METHODS We evaluated the effect of TFPI antagonist aptamer BAX499 (formerly ARC19499) on TFPI function in purified systems and on thrombin generation and clot formation in plasma and blood. RESULTS BAX499 effectively neutralized TFPI inhibition of FXa and FXa dependent inhibition of TF/FVIIa by TFPI. BAX499 did not inhibit FXa or TF/FVIIa when used up to 500 nM. In the synthetic coagulation proteome with TFPI at its mean physiologic concentration, BAX499 at 1 - 10nM increased thrombin generation triggered with 5 pM relipidated TF in a concentration-dependent manner. In severe hemophilia A or B models using the synthetic coagulation proteome, the addition of BAX499 at 5 nM increased thrombin generation to the levels observed in normal control. Thrombin generation measured in induced hemophilia B plasma required ~100nM BAX499 to restore thrombin levels to those seen in untreated plasma. In induced hemophilia B whole blood, BAX499 repaired the clotting time but failed to appreciably impact the propagation phase of thrombin generation. CONCLUSION These data suggest that inhibition of TFPI by BAX499 may have potential for hemophilia treatment but requires further study in blood-based hemophilia systems.
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Affiliation(s)
- Matthew Gissel
- Department of Biochemistry, University of Vermont, Colchester, Vermont 05446, United States
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