Factor VIII ectopically expressed in platelets: efficacy in hemophilia A treatment.
Activated platelets release their granule content in a concentrated fashion at sites of injury. We examined whether ectopically expressed factor VIII in developing megakaryocytes would be stored in alpha-granules and whether its release from circulating platelets would effectively ameliorate bleeding in a factor VIIInull mice model. Using the proximal glycoprotein 1b alpha promoter to drive expression of a human factor VIII cDNA construct, transgenic lines were established. One line had detectable human factor VIII that colocalizes with von Willebrand factor in platelets. These animals had platelet factor VIII levels equivalent to 3% to 9% plasma levels, although there was no concurrent plasma human factor VIII detectable. When crossed onto a factor VIIInull background, whole blood clotting time was partially corrected, equivalent to a 3% correction level. In a cuticular bleeding time study, these animals also had only a partial correction, but in an FeCl3 carotid artery, thrombosis assay correction was equivalent to a 50% to 100% level. These studies show that factor VIII can be expressed and stored in platelet alpha-granules. Our studies also suggest that platelet-released factor VIII is at least as potent as an equivalent plasma level and perhaps even more potent in an arterial thrombosis model.
Yarovoi
Helen V
HV
The Children's Hospital of Philadelphia, 1 Civic Center, ARC, Rm 317, Philadelphia, PA 19104, USA.
Kufrin
Dubravka
D
Eslin
Don E
DE
Thornton
Michael A
MA
Haberichter
Sandra L
SL
Shi
Qizhen
Q
Zhu
Hua
H
Camire
Rodney
R
Fakharzadeh
Steve S
SS
Kowalska
M Anna
MA
Wilcox
David A
DA
Sachais
Bruce S
BS
Montgomery
Robert R
RR
Poncz
Mortimer
M
D000818:Animals; D001780:Blood Coagulation Tests; D001792:Blood Platelets / Q000378:metabolism* / Q000648:ultrastructure; D002339:Carotid Arteries; D003594:Cytoplasmic Granules / Q000737:chemistry; D004195:Disease Models, Animal; D005169:Factor VIII / Q000008:administration & dosage* / Q000096:biosynthesis* / Q000235:genetics; D015316:Genetic Therapy / Q000379:methods*; D006467:Hemophilia A / Q000628:therapy*; D006470:Hemorrhage / Q000517:prevention & control / Q000628:therapy; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D017384:Sequence Deletion; D013927:Thrombosis / Q000517:prevention & control / Q000628:therapy
D005169:Factor VIII