Abstract Number: PB0341
Meeting: ISTH 2020 Congress
Background: Haemophilia B is a blood clotting disorder caused by deficiency in coagulation Factor IX (FIX). Patients are treated by infusion of FIX concentrates based on the plasma concentration, however, significant evidence points towards an extravascular compartment of FIX. FIX binds reversibly to collagen IV in the basal lamina of blood vessels and may be the site of an extravascular store.
Aims: To evaluate the impact of the collagen-FIX interaction on thrombin generation.
Methods: Flat-bottomed plates were coated with collagen IV overnight at 4°C, prior to application of recombinant FIX (BeneFIX; Pfizer) for 1 h at 37°C. Wells were washed with PBS in between steps to remove any unbound collagen or FIX. Thrombin generation (TG) was performed on platelet-poor plasma (PPP) or FIX deficient plasma (FIX-DP) and measured using the Calibrated Automated Thrombogram (CAT). In some cases, 2 x 108plt/mL platelets were incorporated. FIX was measured using a commercial chromogenic assay.
Results: FIX-DP ± platelets did not generate thrombin on uncoated or collagen coated surfaces. However, on surfaces with the FIX-collagen complex present, FIX-DP + platelets generated a peak thrombin concentration comparable to the healthy control; 67.07 ± 7.0 vs. 101.4 ± 28.2 nM, respectively. The lag time was significantly delayed in FIX-DP (41.3 ± 2.9 min) compared to PPP (25.3 ± 2.3 min, p < 0.05). FIX binding to collagen was confirmed by chromogenic assay and FIX activity was found to be 34 % of normal circulating levels, approximately 1.7 µg/ml.
Conclusions: Our data suggests the FIX-collagen interaction is required for normal TG to occur. Collagen IV binding of FIX may provide a long-lasting extravascular reservoir of FIX at a haemostatic and functional location, such as the joints. Similar results were obtained in preliminary experiments with Factor VIII, suggesting the intrinsic tenase may be able to assemble on a collagen surface.
To cite this abstract in AMA style:
Morrow GB, Laffan MA, Curry N. Evaluation of Coagulation FIX Binding to Collagen IV and the Impact on Thrombin Generation [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/evaluation-of-coagulation-fix-binding-to-collagen-iv-and-the-impact-on-thrombin-generation/. Accessed March 21, 2024.« Back to ISTH 2020 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/evaluation-of-coagulation-fix-binding-to-collagen-iv-and-the-impact-on-thrombin-generation/