Factor VIII contributes to platelet-fibrin thrombus formation via thrombin generation under low shear conditions.
BACKGROUND
Thrombus growth under low blood flow velocity plays an important role in the development of deep venous thrombosis (DVT). Increased plasma levels and activities of coagulation factor VIII (FVIII) comprise risk factors for DVT and pulmonary thromboembolism.


OBJECTIVE
To localize FVIII in human venous thrombi of DVT and to determine whether FVIII contributes to thrombus formation under low shear conditions.


METHODS
The localization of FVIII in venous thrombi obtained from patients with DVT was examined by immunohistochemistry. The role of FVIII in thrombus formation was investigated using a flow chamber system. Venous blood from healthy volunteers were incubated with an anti-FVIII monoclonal antibody (VIII-3776) or non-immunized mouse IgG(1). Blood samples were perfused on immobilized type III collagen at wall shear rates of 70/s and 400/s and then the surface area covered by platelets and fibrin was morphometrically evaluated. Prothrombin fragment 1+2 (PF1+2) generation was measured before and after perfusion.


RESULTS
Venous thrombi of DVT comprised a mixture of platelets, fibrin and erythrocytes. Factor VIII appeared to be colocalized with glycoprotein IIb/IIIa, fibrin and von Willebrand factor in the thrombi. VIII-3776 specifically recognized the light chain of FVIII and prolonged the activated partial thromboplastin time (aPTT), but not prothrombin time (PT). The antibody significantly reduced platelets and fibrin covering, as well as PF1+2 generation at wall shear rates of 70/s and 400/s.


CONCLUSIONS
These results suggest that FVIII contributes to platelet aggregation and fibrin formation via thrombin generation under low shear conditions.
Sugita
Chihiro
C
Department of Pathology, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan.
Yamashita
Atsushi
A
Moriguchi-Goto
Sayaka
S
Furukoji
Eiji
E
Takahashi
Misaki
M
Harada
Aya
A
Soeda
Tetsuhiro
T
Kitazawa
Takehisa
T
Hattori
Kunihiro
K
Tamura
Shozo
S
Asada
Yujiro
Y
D000328:Adult; D000368:Aged; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D003094:Collagen / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005169:Factor VIII / Q000378:metabolism*; D005260:Female; D005337:Fibrin / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D019463:Mice, Inbred MRL lpr; D008875:Middle Aged; D010974:Platelet Aggregation / Q000502:physiology; D033081:Shear Strength; D013917:Thrombin / Q000378:metabolism; D020246:Venous Thrombosis / Q000097:blood* / Q000628:therapy; D014841:von Willebrand Factor / Q000378:metabolism
D014841:von Willebrand Factor; D005169:Factor VIII; D005337:Fibrin; D003094:Collagen; D013917:Thrombin