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Ex vivo gene therapy for hemophilia A that enhances safe delivery and sustained in vivo factor VIII expression from lentivirally engineered endothelial progenitors.

Abstract
Novel therapeutic strategies for hemophilia must be at least as effective as current treatments and demonstrate long-term safety. To date, several small clinical trials of hemophilia gene transfer have failed to show the promise of preclinical evaluations. Therefore, we wanted to develop and evaluate the feasibility of a novel ex vivo gene transfer strategy whereby cells derived from progenitor cells are engineered to express factor VIII (FVIII) and then implanted subcutaneously to act as a depot for FVIII expression. Circulating blood outgrowth endothelial cells (BOECs) were isolated from canine and murine blood and transduced with a lentiviral vector encoding the canine FVIII transgene. To enhance safety, these cells were implanted subcutaneously in a Matrigel scaffold, and the efficacy of this strategy was compared with i.v. delivery of engineered BOECs in nonhemophilic nonobese diabetic/severe combined immunodeficiency mice. Therapeutic levels of FVIII persisted for 15 weeks, and these levels of stable expression were extended to 20 weeks when the cytomegalovirus promoter was replaced with the thrombomodulin regulatory element. Subsequent studies in immunocompetent hemophilic mice, pretreated with tolerizing doses of FVIII or with transient immunosuppression, showed therapeutic FVIII expression for 27 weeks before the eventual return to baseline levels. This loss of transgene expression appears to be due to the disappearance of the implanted cells. The animals treated with either of the two tolerizing regimens did not develop anti-FVIII antibodies. Biodistribution analysis demonstrated that BOECs were retained inside the subcutaneous implants. These results indicate, for the first time, that genetically modified endothelial progenitor cells implanted in a subcutaneous scaffold can provide sustained therapeutic levels of FVIII and are a promising and safe treatment modality for hemophilia A. Disclosure of potential conflicts of interest is found at the end of this article.
AuthorsHideto Matsui, Masaru Shibata, Brian Brown, Andrea Labelle, Carol Hegadorn, Chandler Andrews, Robert P Hebbel, Jacques Galipeau, Christine Hough, David Lillicrap
JournalStem cells (Dayton, Ohio) (Stem Cells) Vol. 25 Issue 10 Pg. 2660-9 (Oct 2007) ISSN: 1549-4918 [Electronic] England
PMID17615271 (Publication Type: Evaluation Study, Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
Chemical References
  • Recombinant Fusion Proteins
  • Factor VIII
Topics
  • Animals
  • Cells, Cultured (metabolism, transplantation)
  • Desensitization, Immunologic
  • Dogs
  • Endothelial Cells (metabolism, transplantation)
  • Factor VIII (administration & dosage, biosynthesis, genetics, immunology)
  • Feasibility Studies
  • Genetic Therapy (methods)
  • Genetic Vectors (administration & dosage, genetics, therapeutic use)
  • Graft Survival
  • Hemophilia A (blood, genetics, therapy)
  • Injections, Subcutaneous
  • Lentivirus (genetics)
  • Mice
  • Mice, Inbred NOD
  • Mice, Mutant Strains
  • Mice, SCID
  • Recombinant Fusion Proteins (biosynthesis, physiology)
  • Tissue Scaffolds
  • Transduction, Genetic

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