title: Factor VIII ectopically expressed in platelets: efficacy in hemophilia A treatment.
abstract: 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.
authors.affiliation: The Children's Hospital of Philadelphia, 1 Civic Center, ARC, Rm 317, Philadelphia, PA 19104, USA.
authors.forename: Helen V
authors.initials: HV
authors.lastname: Yarovoi
authors.forename: Dubravka
authors.initials: D
authors.lastname: Kufrin
authors.forename: Don E
authors.initials: DE
authors.lastname: Eslin
authors.forename: Michael A
authors.initials: MA
authors.lastname: Thornton
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Haberichter
authors.forename: Qizhen
authors.initials: Q
authors.lastname: Shi
authors.forename: Hua
authors.initials: H
authors.lastname: Zhu
authors.forename: Rodney
authors.initials: R
authors.lastname: Camire
authors.forename: Steve S
authors.initials: SS
authors.lastname: Fakharzadeh
authors.forename: M Anna
authors.initials: MA
authors.lastname: Kowalska
authors.forename: David A
authors.initials: DA
authors.lastname: Wilcox
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Sachais
authors.forename: Robert R
authors.initials: RR
authors.lastname: Montgomery
authors.forename: Mortimer
authors.initials: M
authors.lastname: Poncz
mesh_terms: 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
chemical_list: D005169:Factor VIII