Phenotypic correction of hemophilia A by ectopic expression of activated factor VII in platelets.
Platelets are receiving much attention as novel target cells to secrete a coagulation factor for hemophilia gene therapy. In order to extend the application of platelet-directed gene therapy, we examined whether ectopic expression of activated factor VII (FVIIa) in platelets would result in an efficient bypass therapy to induce sufficient thrombin generation on platelet surfaces in mice with hemophilia A. Transduction of bone marrow cells with a simian immunodeficiency virus (SIV)-based lentiviral vector harboring the platelet-specific GPIb alpha promoter resulted in efficient transgene expression in platelets. FVIIa antigen was expressed in platelets by this SIV system; FVII transgene products were found to localize in the cytoplasm and translocate toward the sub-membrane zone and cell surface after activation. Although FVII antigen levels in platelets did not reach the therapeutic levels seen with FVIIa infusion therapy, whole-blood coagulation, as assessed by thromboelastography, was significantly improved in mice with hemophilia A. Further, we observed correction of the bleeding phenotype in mice with hemophilia A after transplantation, even in the presence of FVIII-neutralizing antibodies. Our results demonstrate that FVIIa-expressing platelets can strengthen hemostatic function and may be useful in treating hemophilia and other inherited bleeding disorders. These findings are comparable to the proven therapeutic effects of FVIIa infusion.
Research Division of Cell and Molecular Medicine, Center for Molecular Medicine, Jichi Medical University School of Medicine, Tochigi, Japan. tohmori@jichi.ac.jp
Tsukasa
T
Ohmori
Akira
A
Ishiwata
Yuji
Y
Kashiwakura
Seiji
S
Madoiwa
Katsuyuki
K
Mitomo
Hidenori
H
Suzuki
Mamoru
M
Hasegawa
Jun
J
Mimuro
Yoichi
Y
Sakata
D000818:Animals; D000906:Antibodies / Q000008:administration & dosage / Q000494:pharmacology; D001792:Blood Platelets / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D002478:Cells, Cultured; D005169:Factor VIII / Q000276:immunology; D015942:Factor VIIa / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015870:Gene Expression / Q000187:drug effects; D005822:Genetic Vectors / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism; D006467:Hemophilia A / Q000235:genetics / Q000473:pathology / Q000628:therapy*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D016253:Microscopy, Immunoelectron; D010641:Phenotype; D015302:Simian Immunodeficiency Virus / Q000235:genetics
D000906:Antibodies; D049452:Green Fluorescent Proteins; D005169:Factor VIII; D015942:Factor VIIa