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Faxälv, Lars
Alternative names
Publications (10 of 27) Show all publications
Lindahl, T., Ramström, S., Boknäs, N. & Faxälv, L. (2016). Caveats in studies of the physiological role of polyphosphates in coagulation. Biochemical Society Transactions, 44, 35-39.
Open this publication in new window or tab >>Caveats in studies of the physiological role of polyphosphates in coagulation
2016 (English)In: Biochemical Society Transactions, ISSN 0300-5127, E-ISSN 1470-8752, Vol. 44, 35-39 p.Article in journal (Refereed) Published
Abstract [en]

Platelet-derived polyphosphates (polyP), stored in dense granule and released upon platelet activation, have been claimed to enhance thrombin activation of coagulation factor XI (FXI) and to activate FXII directly. The latter claim is controversial and principal results leading to these conclusions are probably influenced by methodological problems. It is important to consider that low-grade contact activation is initiated by all surfaces and is greatly amplified by the presence of phospholipids simulating the procoagulant membranes of activated platelets. Thus, proper use of inhibitors of the contact pathway and a careful choice of materials for plates and tubes is important to avoid artefacts. The use of phosphatases used to degrade polyP has an important drawback as it also degrades the secondary activators ADP and ATP, which are released from activated platelets. In addition, the use of positively charged inhibitors, such as polymyxin B, to inhibit polyP in platelet-rich plasma and blood is problematic, as polymyxin B also slows coagulation in the absence of polyP. In conclusion we hope awareness of the above caveats may improve research on the physiological roles of polyP in coagulation. © 2016 Authors; published by Portland Press Limited.

Place, publisher, year, edition, pages
Portland Press Ltd, 2016
Keyword
Blood; Coagulation; Contact activation; Phosphatase; Platelets; Polyphosphate
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-126155 (URN)10.1042/BST20150220 (DOI)26862185 (PubMedID)2-s2.0-84957871941 (Scopus ID)
Note

Funding Agencies|20140410, Hjärt-Lungfonden; K2013-65X-15060-10-3, Hjärt-Lungfonden

Available from: 2016-03-15 Created: 2016-03-15 Last updated: 2017-11-30
Claesson, K., Lindahl, T. & Faxälv, L. (2016). Counting the platelets: a robust and sensitive quantification method for thrombus formation. Thrombosis and Haemostasis, 115(6), 1178-1190.
Open this publication in new window or tab >>Counting the platelets: a robust and sensitive quantification method for thrombus formation
2016 (English)In: Thrombosis and Haemostasis, ISSN 0340-6245, Vol. 115, no 6, 1178-1190 p.Article in journal (Refereed) Published
Abstract [en]

Flow chambers are common tools used for studying thrombus formation in vitro. However, the use of such devices is not standardised and there is a large diversity among the flow chamber systems currently used, and also in the methods used for quantifying the thrombus development. It was the study objective to evaluate a new method for analysis and quantification of platelet thrombus formation that can facilitate comparison of results between research groups. Whole blood was drawn over a collagen patch in commercial Ibid or in-house constructed PDMS flow chambers. Five percent of the platelets were fluorescently labelled and z-stack time-lapse images were captured during thrombus formation. Images were processed in a Python script in which the number of platelets and their respective x-, y- and z-positions were obtained. For comparison with existing methods the platelets were also labelled and quantified using fluorescence intensity and thrombus volume estimations by confocal microscopy. The presented method was found less sensitive to microscope and image adjustments and provides more details on thrombus development dynamics than the methods for measuring fluorescence intensity and thrombus volume estimation. The platelet count method produced comparable results with commercial and PDMS flow chambers, and could also obtain information regarding the stability of each detected platelet in the thrombus. In conclusion, quantification of thrombus formation by platelet count is a sensitive and robust method that enables measurement of platelet accumulation and platelet stability in an absolute scale that could be used for comparisons between research groups.

Place, publisher, year, edition, pages
SCHATTAUER GMBH-VERLAG MEDIZIN NATURWISSENSCHAFTEN, 2016
Keyword
Platelet aggregation; microfluidics; thrombosis; fluorescence microscopy; computer-assisted image processing
National Category
Clinical Laboratory Medicine
Identifiers
urn:nbn:se:liu:diva-130073 (URN)10.1160/TH15-10-0799 (DOI)000377237400011 ()26842994 (PubMedID)
Note

Funding Agencies|Swedish Research Council [K2015-79X-22644-01-3]; Linkoping University

Available from: 2016-07-06 Created: 2016-07-06 Last updated: 2017-11-28
Tynngård, N., Wallstedt, M., Södergren, A. L., Faxälv, L. & Ramström, S. (2015). Platelet adhesion changes during storage studied with a novel method using flow cytometry and protein-coated beads. Platelets, 26(2), 177-185.
Open this publication in new window or tab >>Platelet adhesion changes during storage studied with a novel method using flow cytometry and protein-coated beads
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2015 (English)In: Platelets, ISSN 0953-7104, E-ISSN 1369-1635, Vol. 26, no 2, 177-185 p.Article in journal (Refereed) Published
Abstract [en]

The aim of the present study was to set up and evaluate a novel method for studies of platelet adhesion and activation in blood and platelet suspensions such as platelet concentrate (PC) samples using protein-coated polystyrene beads and flow cytometry. To demonstrate its usefulness, we studied PCs during storage. PCs were prepared by aphaeresis technique (n = 7). Metabolic variables and platelet function was measured on day 1, 5, 7 and 12 of storage. Spontaneous and TRAP-6-induced adhesion to fibrinogen- and collagen-coated beads was analyzed by flow cytometry. P-selectin and phosphatidyl serine (PS) expression was assessed on platelets bound to beads as well as on non-adherent platelets. Platelet adhesion to fibrinogen beads had increased by day 12 and adhesion to collagen beads at day 7 of storage (p < 0.05). TRAP-6 stimulation significantly increased the platelet adhesion to fibrinogen beads (p < 0.05) as well as the P-selectin and PS exposure on platelets bound to beads (p < 0.01) during the first 7 days of storage, but by day 12, significant changes were no longer induced by TRAP-6 stimulation. We demonstrate that our adhesion assay using protein-coated polystyrene beads can be used to assess the adhesion properties of platelets during storage without the addition of red blood cells. Therefore it may offer a useful tool for future studies of platelet adhesive capacity in transfusion medicine and other settings.

National Category
Basic Medicine
Identifiers
urn:nbn:se:liu:diva-111533 (URN)10.3109/09537104.2014.891728 (DOI)000351740700012 ()24679340 (PubMedID)
Available from: 2014-10-22 Created: 2014-10-22 Last updated: 2018-01-11Bibliographically approved
Lindahl, T. & Faxälv, L. (2015). Stable solution. European Union PC-EP 2 533 788.
Open this publication in new window or tab >>Stable solution
2015 (English)Patent (Other (popular science, discussion, etc.))
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-126665 (URN)
Patent
European Union PC-EP 2 533 788 (2015-12-16)
Available from: 2016-04-01 Created: 2016-04-01 Last updated: 2016-04-01
Boknäs, N., Faxälv, L., Lindahl, T. L. & Ramström, S. (2014). Contact activation: important to consider when measuring the contribution of tissue factor-bearing microparticles to thrombin generation using phospholipid-containing reagents. Journal of Thrombosis and Haemostasis, 12(4), 515-518.
Open this publication in new window or tab >>Contact activation: important to consider when measuring the contribution of tissue factor-bearing microparticles to thrombin generation using phospholipid-containing reagents
2014 (English)In: Journal of Thrombosis and Haemostasis, ISSN 1538-7933, E-ISSN 1538-7836, Vol. 12, no 4, 515-518 p.Article in journal (Refereed) Published
Abstract [en]

Background A commercial MP reagent containing phospholipids is used for thrombin generation (TG) measurements to estimate the procoagulant activity of microparticles (MPs). Previous reports have shown that contact activation affects TG when TF levels are low, and that addition of phospholipids might augment this effect. Objectives To quantify the impact of contact activation on TG in the presence of phospholipids and low/no TF, as is the case using a commercially available MP-reagent. Methods Thrombin generation was analyzed using MP- or platelet-rich plasma (PRP)-reagent in the presence and absence of corn trypsin inhibitor and anti-TF antibodies, respectively. To quantify the impact of different experimental parameters on contact activation, microparticle-depleted plasma was analyzed in the presence of different concentrations of phospholipids, TF and/or contact activating agents (kaolin). Results Even with low contact activating blood collection tubes, substantial thrombin generation was observed with the MP-reagent, but this was completely inhibited by addition of corn trypsin inhibitor. Control experiments illustrate that the phospholipids in the reagent play a major role in enhancing TG initiated by FXIIa. Even with the PRP-reagent, which is recommended for determining the content of phospholipids from MPs, TG was partly dependent on contact activation. Conclusions Contact activation plays a major role in TG when using reagents/samples containing phospholipids but little or no tissue factor. This needs to be considered and accounted for in future clinical studies using TG to assess the procoagulant activity of MPs.

Place, publisher, year, edition, pages
Wiley, 2014
Keyword
cell-derived microparticles; thromboplastin; blood coagulation; thrombin; factor XII
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-106682 (URN)10.1111/jth.12503 (DOI)000334157000012 ()
Available from: 2014-05-21 Created: 2014-05-19 Last updated: 2017-12-05
Hillarp, A., Gustafsson, K., Faxälv, L., Strandberg, K., Baghaei, F., Fagerberg Blixter, I., . . . Lindahl, T. (2014). Effects of the oral, direct factor Xa inhibitor apixaban on routine coagulation assays and anti-FXa assays. Journal of Thrombosis and Haemostasis, 12(9), 1545-1553.
Open this publication in new window or tab >>Effects of the oral, direct factor Xa inhibitor apixaban on routine coagulation assays and anti-FXa assays
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2014 (English)In: Journal of Thrombosis and Haemostasis, ISSN 1538-7933, E-ISSN 1538-7836, Vol. 12, no 9, 1545-1553 p.Article in journal (Refereed) Published
Abstract [en]

INTRODUCTION:

Apixaban is an oral direct factor Xa inhibitor developed for the prophylaxis and treatment of thromboembolic disorders. Laboratory monitoring is not necessary, but the effects on common coagulation reagents and assays constitute clinically valuable information.

OBJECTIVES:

To investigate the effects of apixaban on commonly used coagulation methods, and to evaluate anti-FXa assays for specific determination of the drug concentration.

MATERIALS AND METHODS:

Apixaban was added to plasma from healthy subjects in the concentration range 0-1000 μg L(-1) , and analyses were performed with different reagents for activated partial thromboplastin time (APTT), prothrombin time (PT), antithrombin, protein C, and protein S. A lupus anticoagulant assay and an APTT assay with varying phospholipid concentrations were used to study the phospholipid dependence.

RESULTS:

In general, apixaban showed fewer effects in vitro than have been shown for rivaroxaban, another direct FXa inhibitor. The concentration needed to double the APTT varied between 2200 and 4700 μg L(-1) , and the concentration needed to double the PT varied between 700 and 3900 μg L(-1) . The effects on antithrombin, protein C and protein S assays were dependent on the type of reagent. Apixaban did not cause false-positive lupus anticoagulant results. Chromogenic anti-FXa assays showed linear dose-response curves with apixaban.

CONCLUSIONS:

Therapeutic concentrations of apixaban variably affect different assay groups, and even different reagents within an assay group. The effects were much smaller than with rivaroxaban. The use of APTT and/or PT assays to screen the anticoagulant activity of apixaban cannot be recommended. A chromogenic anti-FXa assay can be used for reliable measurements of apixaban concentration.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2014
Keyword
analysis; anticogaulants; apixaban; blood coagulation tests; factorXa
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-111458 (URN)10.1111/jth.12649 (DOI)000342143900023 ()24965851 (PubMedID)
Note

Funding Agencies|Bristol Meyers Squibb

Available from: 2014-10-21 Created: 2014-10-17 Last updated: 2017-12-05Bibliographically approved
Faxälv, L., Bolin, M., Jager, E., Lindahl, T. & Berggren, M. (2014). Electronic control of platelet adhesion using conducting polymer microarrays. Lab on a Chip, 14(16), 3043-3049.
Open this publication in new window or tab >>Electronic control of platelet adhesion using conducting polymer microarrays
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2014 (English)In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 14, no 16, 3043-3049 p.Article in journal (Refereed) Published
Abstract [en]

We hereby report a method to fabricate addressable micropatterns of e-surfaces based on the conducting polymer poly(3,4-ethylenedioxythiophene) doped with the anion tosylate (PEDOT:Tos) to gain dynamic control over the spatial distribution of platelets in vitro. With thin film processing and microfabrication techniques, patterns down to 10 mu m were produced to enable active regulation of platelet adhesion at high spatial resolution. Upon electronic addressing, both reduced and oxidized surfaces were created within the same device. This surface modulation dictates the conformation and/or orientation, rather than the concentration, of surface proteins, thus indirectly regulating the adhesion of platelets. The reduced electrode supported platelet adhesion, whereas the oxidized counterpart inhibited adhesion. PEDOT:Tos electrode fabrication is compatible with most of the classical patterning techniques used in printing as well as in the electronics industry. The first types of tools promise ultra-low-cost production of low-resolution (greater than30 mu m) electrode patterns that may combine with traditional substrates and dishes used in a classical analysis setup. Platelets play a pronounced role in cardiovascular diseases and have become an important drug target in order to prevent thrombosis. This clinical path has in turn generated a need for platelet function tests to monitor and assess platelet drug efficacy. The spatial control of platelet adherence presented here could prove valuable for blood cell separation or biosensor microarrays, e.g. in diagnostic applications where platelet function is evaluated.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2014
National Category
Clinical Medicine Biological Sciences Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-109579 (URN)10.1039/c4lc00201f (DOI)000339470400020 ()24960122 (PubMedID)
Available from: 2014-08-21 Created: 2014-08-21 Last updated: 2017-12-05
Saleiban, A., Faxälv, L., Claesson, K., Jönsson, J.-I. & Osman, A. (2014). miR-20b regulates expression of proteinase-activated receptor-1 (PAR-1) thrombin receptor in melanoma cells. Pigment Cell & Melanoma Research, 27(3), 431-441.
Open this publication in new window or tab >>miR-20b regulates expression of proteinase-activated receptor-1 (PAR-1) thrombin receptor in melanoma cells
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2014 (English)In: Pigment Cell & Melanoma Research, ISSN 1755-1471, E-ISSN 1755-148X, Vol. 27, no 3, 431-441 p.Article in journal (Refereed) Published
Abstract [en]

The proteinase-activated receptor 1 (PAR-1) plays a central role in melanoma progression and its expression level is believed to correlate with the degree of cancer invasiveness. Here, we show that PAR-1 is post-transcriptionally regulated by miR-20b microRNA in human melanoma cells. PAR-1 was found to be expressed in metastatic melanoma cells but was barely detectable in primary melanoma. By transducing primary melanoma cells with a lentivirus containing a 3-UTR construct of PAR-1 mRNA, we could show that endogenous melanoma microRNAs interacted with PAR-1 3-UTR and silenced a fused luciferase reporter. Transfection of an inhibitor against miR-20b into primary melanoma cells reversed this process. Finally, transfection of miR-20b mimic into metastatic melanoma cells caused downregulation of the luciferase reporter. We conclude that miR-20b regulates expression of melanoma PAR-1 receptor, which may explain the differential expression of PAR-1 observed in human melanoma.

Place, publisher, year, edition, pages
Wiley, 2014
Keyword
melanoma; metastasis; proteinase-activated receptor-1; gene expression regulation; microRNAs
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-106844 (URN)10.1111/pcmr.12217 (DOI)000334170900014 ()
Available from: 2014-05-28 Created: 2014-05-23 Last updated: 2017-12-05
Boknäs, N., Faxälv, L., Ström, J. O., Tengvall, P., Theodorsson, E., Ramström, S. & Lindahl, T. L. (2014). Response: platelets do not generate activated factor XII--how inappropriate experimental models have led to misleading conclusions [Letter to the editor]. Blood, 124(10), 1692-1694.
Open this publication in new window or tab >>Response: platelets do not generate activated factor XII--how inappropriate experimental models have led to misleading conclusions
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2014 (English)In: Blood, ISSN 0006-4971, E-ISSN 1528-0020, Vol. 124, no 10, 1692-1694 p.Article in journal, Letter (Other academic) Published
Place, publisher, year, edition, pages
American Society of Hematology, 2014
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-111531 (URN)10.1182/blood-2014-04-566067 (DOI)000342762300027 ()25190755 (PubMedID)
Available from: 2014-10-22 Created: 2014-10-22 Last updated: 2017-12-05Bibliographically approved
Boknäs, N., Faxälv, L., Sanchez Centellas, D., Wallstedt, M., Ramström, S., Grenegård, M. & Lindahl, T. (2014). Thrombin-induced platelet activation via PAR4: pivotal role for exosite II. Thrombosis and Haemostasis, 112(3), 558-565.
Open this publication in new window or tab >>Thrombin-induced platelet activation via PAR4: pivotal role for exosite II
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2014 (English)In: Thrombosis and Haemostasis, ISSN 0340-6245, Vol. 112, no 3, 558-565 p.Article in journal (Refereed) Published
Abstract [en]

Thrombin-induced platelet activation via PAR1 and PAR4 is an important event in haemostasis. Although the underlying mechanisms responsible for ensuring efficient PAR1 activation by thrombin have been extensively studied, the potential involvement of recognitions sites outside the active site of the protease in thrombin-induced PAR4 activation is largely unknown. In this study, we developed a new assay to assess the importance of exosite I and II for PAR4 activation with alpha- and gamma-thrombin. Surprisingly, we found that exosite II is critical for activation of PAR4. We also show that this dependency on exosite II likely represents a new mechanism, as it is unaffected by blockage of the previously known interaction between thrombin and glycoprotein Ib alpha.

Place, publisher, year, edition, pages
Schattauer Gmbh, 2014
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-111269 (URN)10.1160/TH13-12-1013 (DOI)000341547000015 ()24990072 (PubMedID)
Note

Funding Agencies|Swedish Research Council [K2010-65X-15060-07-3, K2013-65X-15060-10-3]; Swedish Heart and Lung Foundation [20100219, 20120263]

Available from: 2014-10-15 Created: 2014-10-14 Last updated: 2017-12-05Bibliographically approved
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