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How factor VIIa works in hemophilia
S Butenas1, K E Brummel, B A Bouchard
1Department of Biochemistry, University of Vermont, 89 Beaumont Avenue, Burlington, VT 05405-0068, USA.
Journal of Thrombosis and Haemostasis : JTH
|July 23, 2003
Summary
Elevated platelets and recombinant factor VIIa (rFVIIa) can improve thrombin generation in hemophilia B models. This suggests local TF expression and platelet accumulation enhance rFVIIa efficacy at vascular injury sites.
Area of Science:
- Hematology
- Biochemistry
- Molecular Biology
Background:
- Hemophilia B is a bleeding disorder caused by a deficiency in factor IX.
- Thrombin generation is critical for hemostasis and is impaired in hemophilia B.
- Recombinant factor VIIa (rFVIIa) is used to treat bleeding episodes in hemophilia.
Purpose of the Study:
- To evaluate the impact of elevated platelet concentration and rFVIIa on thrombin generation in hemophilia B models.
- To investigate the conditions under which rFVIIa can restore thrombin generation in vitro.
Main Methods:
- In vitro study using synthetic hemophilia B blood (SHB) and acquired hemophilia B blood (AHBB) models.
- Assessed thrombin generation at varying concentrations of tissue factor (TF), rFVIIa, and platelets (activated and nonactivated).
Main Results:
- Thrombin generation was significantly reduced and delayed in SHB and AHBB.
- Both 10 nM rFVIIa and 5x normal platelet concentration showed a slight increase in thrombin generation.
- Near-normal thrombin levels were achieved with 10 nM rFVIIa and 3-5x normal nonactivated platelets in the presence of TF.
Conclusions:
- rFVIIa can effectively restore thrombin generation in hemophilia B models under specific conditions.
- Local TF expression and platelet accumulation at vascular lesions enhance rFVIIa's hemostatic function.