Development of a Computer Program to Analyze the Parameters of Platelet-Vessel Wall Interaction

Escolar, G; Bastida, E; Castillo, R; Ordinas, Antonio

doi:10.1159/000215263

Cited by 37 publications

(53 citation statements)

References 10 publications

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“…The presence of fibrin was also morphometrically quantified and expressed as a percentage of fibrin (% F) or as the mean area of the fibrin mesh (Area F; m 2 ). 36 …”

Section: Studies In Annular Perfusion Devicesmentioning

confidence: 99%

Redistribution and Hemostatic Action of Recombinant Activated Factor VII Associated with Platelets

López-Vílchez

Hedner

Altisent

et al. 2011

The American Journal of Pathology

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Clinical evidence accumulated from hemophilic patients during prophylaxis with recombinant activated factor VII (rFVIIa) suggests that the duration of the hemostatic action of rFVIIa exceeds its predicted plasma half-life. Mechanisms involved in this outcome have not been elucidated. We have investigated in vitro the redistribution of rFVIIa in platelets from healthy donors, patients with FVII deficiency, and one patient with Bernard-Soulier syndrome. Platelet-rich plasma was exposed to rFVIIa (3 to 60 g/mL). Flow cytometry, immunocytochemistry, and coagulation tests were applied to detect and quantify rFVIIa. The hemostatic effect of rFVIIa associated to platelets was evaluated using perfusion models. Our studies revealed a dose-dependent association of rFVIIa to the platelet cytoplasm with redistribution into the open canalicular system, and ␣ granules. Mechanisms implicated in the internalization are multiple, involve GPIb and GPIV, and require phospholipids and cytoskeletal assembly. After platelet activation with thrombin, platelets exposed rFVIIa on their membrane. Perfusion studies revealed that the presence of 30% of platelets containing FVIIa improved platelet aggregate formation and enhanced fibrin generation (P < 0.01 versus control). Our results indicate that, at therapeutic concentrations, rFVIIa can be internalized into platelets, where it is protected from physiological clearance mechanisms and can still promote hemostatic activity. Redistribution of rFVIIa into platelets may explain the prolonged prophylactic effectiveness of rFVIIa in hemophilia.

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“…The presence of fibrin was also morphometrically quantified and expressed as a percentage of fibrin (% F) or as the mean area of the fibrin mesh (Area F; m 2 ). 36 …”

Section: Studies In Annular Perfusion Devicesmentioning

confidence: 99%

Redistribution and Hemostatic Action of Recombinant Activated Factor VII Associated with Platelets

López-Vílchez

Hedner

Altisent

et al. 2011

The American Journal of Pathology

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“…After perfusion for 10 minutes, the segments were rinsed with PBS, fixed in glutaraldehyde/formaldehyde solution (2%: 3%, vol/ vol), and embedded in JB-4 compound (Polysciences, Warrington, Pa.) as previously described. 16 Three-micron sections were obtained from plastic blocks, stained with toluidine blue, and used for morphometric evaluations.…”

Section: Perfusion Studiesmentioning

confidence: 99%

“…A specially developed computer program was used. 16 Platelets or groups of platelets were classified as follows: contact (C), platelets that were attached but not spread on the subendothelium; adhesion (A), platelets that were spread on the subendothelium or that formed layers of less than 5 jam in height; and thrombi (T), platelet aggregates of 5 /im or more in height. All of these basic parameters are expressed as a percentage of the total length of the vessel screened.…”

Section: Morphometric Evaluationmentioning

confidence: 99%

Plasma from systemic lupus erythematosus patients with antiphospholipid antibodies promotes platelet aggregation. Studies in a perfusion system.

Escolar¹,

Font²,

Reverter³

et al. 1992

Arterioscler Thromb

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The possible platelet-aggregating effect of plasma from systemic lupus erythematosus (SLE) patients (n=19) was investigated under flow conditions. Aliquots of the SLE plasmas with (n=10) or without (n=9) anticardiolipin antibodies (ACAs) were added to anticoagulated blood (1:20, vol/vol). Plasma from normal donors was used as a control. Blood was incubated for 15 minutes at 37°C and then perfused through annular chambers containing denuded arterial segments. Perfusions were performed for 10 minutes at a shear rate of 800 sec"1 . The interaction of platelets with vessel subendothelium (SE) was morphometrically evaluated in thin sections. In control experiments, the percentage of the SE covered with platelets was 23.6±4_3% (mean±SD). Large aggregates (more than 5 /im in height) covering 11.8±5.7% of the exposed SE were noted. The deposition of platelets was statistically increased (38.5 ±7.6%,

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“…Adsorptioninduced unfolding can expose two distinctly different types of platelet-binding sites in FBN: one induces platelet adhesion alone, and the other induces both platelet adhesion and activation. 11,29,41 The present study, in contrast to its initial purpose, offers the possibility of developing new clinical strategies for regulating arterial or venous thrombosis based on the use of liposomes. Our data suggest that the antihemostatic effect observed on liposomes is probably related to the conformational structure adopted by the FBN after binding to the liposome.…”

Section: Discussionmentioning

confidence: 96%

Liposomes bearing fibrinogen could potentially interfere with platelet interaction and procoagulant activity

Hernández

Urbán²,

Casals³

et al. 2012

IJN

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Background:The contribution of fibrinogen (FBN) to hemostasis acting on platelet aggregation and clot formation is well established. It has been suggested that FBN-coated liposomes could be useful in restoring hemostasis. In the present study, we evaluated the modifications induced by multilamellar raw liposomes (MLV) or fibrinogen-coated liposomes (MLV-FBN) on hemostatic parameters. Materials and methods: Different experimental settings using whole blood or thrombocytopenic blood were used. Thromboelastometry, aggregation studies, platelet function analyzer (PFA-100 ® ) tests and studies under flow conditions were applied to detect the effect of MLV-FBN on hemostatic parameters. Results: The presence of MLV-FBN in whole blood modified its viscoelastic properties, prolonging clot formation time (CFT) (226.5 ± 26.1 mm versus 124.1 ± 9.4 mm; P , 0.01) but reducing clot firmness (45.4 ± 1.8 mm versus 35.5 ± 2.3 mm; P , 0.05). Under thrombocytopenic conditions, FIBTEM analysis revealed that MLV-FBN shortened clotting time (CT) compared to MLV (153.3 ± 2.8 s versus 128.0 ± 4.6 s; P , 0.05). Addition of either liposome decreased fibrin formation on the subendothelium (MLV 8.1% ± 4.7% and MLV-FBN 0.8% ± 0.5% versus control 36.4% ± 6.7%; P , 0.01), whereas only MLV-FBN significantly reduced fibrin deposition in thrombocytopenic blood (14.4% ± 6.3% versus control 34.5% ± 5.2%; P , 0.05). MLV-FBN inhibited aggregation induced by arachidonic acid (52.1% ± 8.1% versus 88.0% ± 2.1% in control; P , 0.01) and ristocetin (40.3% ± 8.8% versus 94.3% ± 1.1%; P , 0.005), but it did not modify closure times in PFA-100 ® studies. In perfusion experiments using whole blood, MLV and MLV-FBN decreased the covered surface (13.25% ± 2.4% and 9.85% ± 2.41%, respectively, versus control 22.0% ± 2.0%; P , 0.01) and the percentage of large aggregates (8.4% ± 2.3% and 3.3% ± 1.01%, respectively, versus control 14.6% ± 1.8%; P , 0.01). Conclusion:Our results reveal that, in addition to the main contribution of fibrinogen to hemostasis, MLV-FBN inhibits platelet-mediated hemostasis and coagulation mechanisms.

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Development of a Computer Program to Analyze the Parameters of Platelet-Vessel Wall Interaction

Cited by 37 publications

References 10 publications

Redistribution and Hemostatic Action of Recombinant Activated Factor VII Associated with Platelets

Redistribution and Hemostatic Action of Recombinant Activated Factor VII Associated with Platelets

Plasma from systemic lupus erythematosus patients with antiphospholipid antibodies promotes platelet aggregation. Studies in a perfusion system.

Liposomes bearing fibrinogen could potentially interfere with platelet interaction and procoagulant activity

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