Thein vivocharacterization of electrospun heparin-bonded polycaprolactone in small-diameter vascular reconstruction

ObjectiveTo evaluate the possibility of using heparin-bonded polycaprolactone grafts to replace small-diameter arteries.MethodsPolycaprolactone was bonded with heparin. The activated partial thromboplastin time of heparin-bonded polycaprolactone grafts was determined in vitro. Small-diameter grafts were electrospun with heparin-bonded polycaprolactone and polycaprolactone and were implanted in dogs to substitute part of the femoral artery. Angiography was used to investigate the patency and aneurysm of the grafts after transplantation. After angiography, the patent grafts were explanted for histology analysis. The degradation of the grafts and the collagen content of the grafts were measured.ResultsActivated partial thromboplastin time tests in vitro showed that heparin-bonded polycaprolactone grafts exhibit obvious anticoagulation. Arteriography showed that two heparin-bonded polycaprolactone and three polycaprolactone grafts were obstructed. Other grafts were patent, without aneurysm formation. Histological analysis showed that the tested grafts degraded evidently over the implantation time and that the luminal surface of the tested grafts had become covered by endothelial cells. Collagen deposition in heparin-bonded polycaprolactone increased with time. There were no calcifications in the grafts. Gel permeation chromatography showed the heparin-bonded polycaprolactone explants at 12 weeks lose about 32% for Mw and 24% for Mn. The collagen content on the heparin-bonded polycaprolactone grafts increased over time.ConclusionThis preliminary study demonstrates that heparin-bonded polycaprolactone is a suitable graft for small artery reconstruction. However, heparin-bonded polycaprolactone degrades more rapidly than polycaprolactone in vivo.

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Chemorheological Studies of the Effect of Heparin on the Course of Coagulation

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647977 ◽

1976 ◽

Vol 35 (02) ◽

pp. 447-459

Author(s):

K. A Overholser ◽

C. B Baysinger ◽

T. R Harris ◽

T Deveau

Keyword(s):

Whole Blood ◽

Partial Thromboplastin Time ◽

Time Course ◽

Normal Subjects ◽

Activated Partial Thromboplastin Time ◽

Weissenberg Rheogoniometer ◽

Rheological Measurements ◽

Kinetics Of

SummaryThe influence of sodium heparin on viscoelastic change during coagulation was determined in vitro for whole blood samples from ten normal subjects at heparin concentrations ranging from 0 to 1.45 units/(ml whole blood). A four-parameter chemorheological model was used to describe the time course of coagulation as measured by the Weissenberg Rheogoniometer. One parameter compares closely with the whole blood activated partial thromboplastin time, while the other three may be related to the chemical kinetics of clotting.The chemorheological model and experimental techniques were then tested in a dog preparation. It was found that rheological measurements are more self-consistent than either thrombelastography or the activated partial thromboplastin time for the assay of in vivo heparin in two dogs.

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Effect Of A Non-Activated Prothrombin Complex Concentrate (Prothrombinex) On Platelets: In Vitro And In Vivo Studies

10.1055/s-0038-1653035 ◽

1981 ◽

Author(s):

H Ekert ◽

F L Dean ◽

J L Lane

Keyword(s):

Partial Thromboplastin Time ◽

Prothrombin Complex Concentrate ◽

Platelet Rich Plasma ◽

Inhibitory Effect ◽

Activated Partial Thromboplastin Time ◽

In Vivo Studies ◽

Chromogenic Substrates ◽

Activated Prothrombin Complex Concentrate

Chromatography on Sephadex G-200 of the prothrombin complex concentrate, prothrombinex (Px) showed it to have inhibitor and potentiator fractions when tested by the non-activated partial thromboplastin time (NAPTT). The inhibitory effect was related to the heparin content of Px, as it was removed on ECTEOLA-cellulose. The potentiator fraction clotted fibrinogen and this could be inhibited by hirudin. Thrombin-like activity of this fraction was shown using chromogenic substrates. The effect of the potentiator fraction in the NAPTT was markedly enhanced by platelets. Diluted Px and the potentiator fractions caused aggregation of washed platelets which could be inhibited by hirudin. Aggregation was independent of the prostaglandin pathway, as it occurred in washed aspirin-treated platelets. Neither diluted Px nor potentiator fractions aggregated platelets in platelet rich plasma. Infusion of Px was followed by a rise in β-thromboglobulin (β-TG) in 2 of 3 patients two minutes after infusion. This rise could not be ascribed to the presence of β-TG in Px or to the heparin present in Px. These findings suggest that Px has a thrombin-like activity and that its mode of action in patients with factor VIII antibodies may result from its effect on platelets and their interaction with coagulation enzymes.

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One-step chromogenic equivalent of activated partial thromboplastin time evaluated for clinical application

Clinical Chemistry ◽

10.1093/clinchem/37.7.1235 ◽

1991 ◽

Vol 37 (7) ◽

pp. 1235-1244 ◽

Cited By ~ 4

Author(s):

Gabriëlle E Ponjee ◽

Huib L Vader ◽

Net J de Wild ◽

Ger W T Janssen ◽

Fedde van der Graaf

Keyword(s):

Partial Thromboplastin Time ◽

Clinical Laboratory ◽

Intrinsic Factor ◽

Activated Partial Thromboplastin Time ◽

Factor Vii ◽

Factor Deficiency ◽

One Step ◽

The One

Abstract We evaluated the clinical usefulness of a recently developed semi-automated one-step chromogenic equivalent of activated partial thromboplastin time (APTT; Behring). This simple test is easily adaptable for automation. Generally, the results with this chromogenic one-step APTT were at least as precise as those obtained with comparative coagulometric methods. The chromogenic one-step APTT showed, both in vitro and in vivo, adequate sensitivity to congenital intrinsic factor deficiency but no sensitivity to Factor VII deficiency. Unlike a two-step coagulometric APTT (Dade), the one-step chromogenic APTT seemed sensitive to activation products of the contact system, which are present in immunoadsorbed factor-deficient plasma. The in vitro sensitivity of the chromogenic APTT to heparin was comparable with that of a coagulometric APTT, but the sensitivity to heparin in patients' samples differed slightly. The chromogenic APTT is relatively insensitive to anomalies in the fibrinogen-fibrin conversion. Finally, we observed discrepancies between the chromogenic and coagulometric APTT results for plasma of patients with disseminated intravascular coagulation. We conclude that this one-step chromogenic APTT warrants further evaluation for possible use as a routine test for the clinical laboratory.

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Monitoring Heparin Therapy: Relationships between the Activated Partial Thromboplastin Time and Heparin Assays Based on Ex-Vivo Heparin Samples

Thrombosis and Haemostasis ◽

10.1055/s-0038-1645678 ◽

1990 ◽

Vol 63 (01) ◽

pp. 016-023 ◽

Cited By ~ 41

Author(s):

A M H P van den Bessekaar ◽

J Meeuwisse-Braun ◽

R M Bertina

Keyword(s):

Partial Thromboplastin Time ◽

Plasma Sample ◽

Ex Vivo ◽

Correlation Coefficients ◽

Heparin Therapy ◽

Thromboembolic Disease ◽

Activated Partial Thromboplastin Time ◽

Venous Thromboembolic Disease ◽

Venous Thromboembolic

SummaryFive different APTT reagents, two amidolytic anti-ITa assays, one amidoiytic anti-Xa assay, and one coagulometric anti-Xa/ anti-IIa assay were used to assess the effect of heparin in patients treated for venous thromboembolic disease. Good correlations were observed between lug-transformed APYE> determined with the various reagents (correlation coefficients: 0.92-0.96).Nevertheless there were important differences in the slopes of the lines of relationship between the APTT reagents.Good correlations were observed between the anti-Xa and anti-IIa assay results (correlation coefficients: 0.92-0.97). However, the amidolytic anti-Xa activity was significantly higher (p <0.001) than the two amidolytic anti-IIa activities. Less good correlations were observed between the log-transformed APTTs and the anti-Xa or anti-IIa activities (correlation coefficients: 0.64-0.78). The correlations were improved by transforming the APTT into APTT-ratio, i.e. the ratio of the patient’s APTT to the same patient’s APTT after removal of heparin from the plasma sample by means of ECTEOLA-cellulose treatment. The correlation coefficients of log (AFTT-ratio) with anti-Xa or anti-IIa ranged from 0.76 to 0.87.For both APTT and amidolytic heparin assay, the response to in vitro heparin was different from the response to ex vivo heparin.Therefore, equivalent therapeutic ranges should be assessed by using ex vivo samples rather than in vitro heparin. Because of the response differences between the APTT reagents, it is not adequate to define a therapeutic range for heparin therapy without specification of the reagent.

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Monitoring Anticoagulant Therapy by Activated Partial Thromboplastin Time: Hirudin Assessment

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648943 ◽

1994 ◽

Vol 72 (05) ◽

pp. 685-692 ◽

Cited By ~ 43

Author(s):

Michael T Nurmohamed ◽

René J Berckmans ◽

Willy M Morriën-Salomons ◽

Fenny Berends ◽

Daan W Hommes ◽

...

Keyword(s):

Whole Blood ◽

Partial Thromboplastin Time ◽

Ex Vivo ◽

Fold Increase ◽

Heparin Therapy ◽

Activated Partial Thromboplastin Time ◽

Recombinant Hirudin ◽

Interindividual Differences ◽

The Relationship

SummaryBackground. Recombinant hirudin (RH) is a new anticoagulant for prophylaxis and treatment of venous and arterial thrombosis. To which extent the activated partial thromboplastin time (APTT) is suitable for monitoring of RH has not been properly evaluated. Recently, a capillary whole blood device was developed for bed-side monitoring of the APTT and it was demonstrated that this device was suitable to monitor heparin therapy. However, monitoring of RH was not evaluated.Study Objectives. To evaluate in vitro and ex vivo the responsiveness and reproducibility for hirudin monitoring of the whole blood monitor and of plasma APTT assays, which were performed with several reagents and two conventional coagulometers.Results. Large interindividual differences in hirudin responsiveness were noted in both the in vitro and the ex vivo experiments. The relationship between the APTT, expressed as clotting time or ratio of initial and prolonged APTT, and the hirudin concentration was nonlinear. A 1.5-fold increase of the clotting times was obtained at 150-200 ng/ml plasma. However, only a 2-fold increase was obtained at hirudin levels varying from 300 ng to more than 750 ng RH/ml plasma regardless of the assays. The relationship linearized upon logarithmic conversion of the ratio and the hirudin concentration. Disregarding the interindividual differences, and presuming full linearity of the relationship, all combinations were equally responsive to hirudin.Conclusions. All assays were equally responsive to hirudin. Levels up to 300 ng/ml plasma can be reliably estimated with each assay. The manual device may be preferable in situations where rapid availability of test results is necessary.

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In Vitro Thrombogenicity Tests of Factor IX Concentrates

Thrombosis and Haemostasis ◽

10.1055/s-0038-1657035 ◽

1979 ◽

Vol 42 (05) ◽

pp. 1355-1367 ◽

Cited By ~ 8

Author(s):

C V Prowse ◽

A Chirnside ◽

R A Elton

Keyword(s):

Factor Viii ◽

Partial Thromboplastin Time ◽

Generation Time ◽

Activated Partial Thromboplastin Time ◽

Factor Ix ◽

In Vitro Tests ◽

Factor Viii Inhibitor ◽

Factor Ixa ◽

Viii Inhibitor

SummaryVarious factor IX concentrates have been examined in a number of in vitro tests of thrombogenicity. The results suggest that some tests are superfluous as in concentrates with activity in any of these tests activation is revealed by a combination of the non-activated partial thromboplastin time, the thrombin (or Xa) generation time and factor VIII inhibitor bypassing activity tests. Assay of individual coagulant enzymes revealed that most concentrates contained more factor IXa than Xa. However only a small number of concentrates, chiefly those that had been purposefully activated, contained appreciable amounts of either enzyme.

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Review: Tissue Engineering of Small-Diameter Vascular Grafts and Their In Vivo Evaluation in Large Animals and Humans

Cells ◽

10.3390/cells10030713 ◽

2021 ◽

Vol 10 (3) ◽

pp. 713

Author(s):

Shu Fang ◽

Ditte Gry Ellman ◽

Ditte Caroline Andersen

Keyword(s):

Animal Models ◽

Vascular Grafts ◽

Small Diameter ◽

Large Animal ◽

Large Animal Models ◽

Graft Outcome ◽

Limited Success ◽

Large Animals

To date, a wide range of materials, from synthetic to natural or a mixture of these, has been explored, modified, and examined as small-diameter tissue-engineered vascular grafts (SD-TEVGs) for tissue regeneration either in vitro or in vivo. However, very limited success has been achieved due to mechanical failure, thrombogenicity or intimal hyperplasia, and improvements of the SD-TEVG design are thus required. Here, in vivo studies investigating novel and relative long (10 times of the inner diameter) SD-TEVGs in large animal models and humans are identified and discussed, with emphasis on graft outcome based on model- and graft-related conditions. Only a few types of synthetic polymer-based SD-TEVGs have been evaluated in large-animal models and reflect limited success. However, some polymers, such as polycaprolactone (PCL), show favorable biocompatibility and potential to be further modified and improved in the form of hybrid grafts. Natural polymer- and cell-secreted extracellular matrix (ECM)-based SD-TEVGs tested in large animals still fail due to a weak strength or thrombogenicity. Similarly, native ECM-based SD-TEVGs and in-vitro-developed hybrid SD-TEVGs that contain xenogeneic molecules or matrix seem related to a harmful graft outcome. In contrast, allogeneic native ECM-based SD-TEVGs, in-vitro-developed hybrid SD-TEVGs with allogeneic banked human cells or isolated autologous stem cells, and in-body tissue architecture (IBTA)-based SD-TEVGs seem to be promising for the future, since they are suitable in dimension, mechanical strength, biocompatibility, and availability.

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Scaffolds in tissue engineering of blood vessels

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y10-073 ◽

2010 ◽

Vol 88 (9) ◽

pp. 855-873 ◽

Cited By ~ 60

Author(s):

Divya Pankajakshan ◽

Devendra K. Agrawal

Keyword(s):

Tissue Engineering ◽

Extracellular Matrix ◽

Blood Vessels ◽

Vascular Tissue ◽

Small Diameter ◽

Biological Scaffolds ◽

Hemodynamic Forces ◽

Biodegradable Scaffolds

Tissue engineering of small diameter (<5 mm) blood vessels is a promising approach for developing viable alternatives to autologous vascular grafts. It involves in vitro seeding of cells onto a scaffold on which the cells attach, proliferate, and differentiate while secreting the components of extracellular matrix that are required for creating the tissue. The scaffold should provide the initial requisite mechanical strength to withstand in vivo hemodynamic forces until vascular smooth muscle cells and fibroblasts reinforce the extracellular matrix of the vessel wall. Hence, the choice of scaffold is crucial for providing guidance cues to the cells to behave in the required manner to produce tissues and organs of the desired shape and size. Several types of scaffolds have been used for the reconstruction of blood vessels. They can be broadly classified as biological scaffolds, decellularized matrices, and polymeric biodegradable scaffolds. This review focuses on the different types of scaffolds that have been designed, developed, and tested for tissue engineering of blood vessels, including use of stem cells in vascular tissue engineering.

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