Congress of the International Society on Thrombosis and Haemostasis

Polyphosphate modifies fibrin structure and increases the resistance of clots to fibrinolysis

Abstract number: OC-MO-076

Mutch¹ N.J., Uitte de Willige² S., Engel¹ R., Philippou² H., Ariens² R.A.S.

¹¹Faculty of Biological Sciences ²²Division of Cardiovascular and Diabetes Research, Faculty of Medicine and Health, University of Leeds, Leeds, UK

How-to-cite Mutch NJ, Uitte de Willige S, Engel R, Philippou H, Ariens RAS. Polyphosphate modifies fibrin structure and increases the resistance of clots to fibrinolysis. Journal of Thrombosis and Haemostasis 2009; Volume 7, Supplement 2: Abstract OC-MO-076

Platelet dense granules contain polyphosphate (polyP), a negatively charged polymer that is secreted on activation and influences haemostasis. This study explores the interaction of polyP with fibrin(ogen) and its impact on fibrinolysis. Electrophoretic mobility assays showed that polyP binds fibrinogen and soluble fibrin. Clots formed in the presence of polyP exhibit reduced turbidity compared to control (0.45 ± 0.014 vs. 0.51 ± 0.015). Permeation (Ks) was lower in clots with polyP (3.35 ± 0.15 10⁻⁹ cm²) than without (5.02 ± 0.26 10⁻⁹ cm²). Reduced turbidity and Ks indicate formation of a tighter fibrin network. These changes in fibrin structure were confirmed using confocal and scanning electron microscopy; with clots formed with polyP displaying tight aggregates of fibrin fibers interspaced with large pores, compared to a homogenous distribution in control clots. Lysis by tPA was delayed in clots formed in the presence of polyP (t_1/2 = 108 ± 3 min) compared to controls (t_1/2 = 69 ±2.5 min) and was dependent on both concentration and chain length; longer chain polymers being more effective. PolyP also delayed lysis in clots generated with atroxin, suggesting its influence on fibrin structure is not dependent on thrombin or the release of fibrinopeptide B. In agreement with this, fibrinopeptide A and B release by thrombin was unaltered by the presence of polyP, as quantified by HPLC. Clots composed of repolymerised soluble fibrin in the presence of polyP exhibited similar lysis profiles. Preliminary data using an end-point plate assay indicated reduced binding of tPA to fibrin in the presence of polyP. These data suggest that polyP acts during conversion of fibrinogen to fibrin to generate a clot with an altered fibrin network and a significantly increased resistance to fibrinolysis. Reduced tPA binding to fibrin in the presence of polyP may contribute to the down-regulation of fibrinolysis by this polymer.

Disclosure of interest: none declared.

To cite this abstract use the following format:

Journal of Thrombosis and Haemostasis 2007; Volume 5, Supplement 2: abstract number

Session Details

Date:	Unpresented
Time:	N/A
Session name:	ISTH2009
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