Therapeutic levels of human factor VIII in mice implanted with encapsulated cells: potential for gene therapy of haemophilia A.
BACKGROUND
A gene therapy delivery system based on microcapsules enclosing recombinant cells engineered to secrete a therapeutic protein has been evaluated. The microcapsules are implanted intraperitoneally. In order to prevent cell immune rejection, cells are enclosed in non-antigenic biocompatible alginate microcapsules prior to their implantation into mice. It has been shown that encapsulated myoblasts can deliver therapeutic levels of Factor IX (FIX) in mice. The delivery of human Factor VIII (hFVIII) in mice using microcapsules was evaluated in this study.


METHODS
Mouse C2C12 myoblasts and canine MDCK epithelial kidney cells were transduced with MFG-FVIII (B-domain deleted) vector. Selected recombinant clones were enclosed in alginate microcapsules. Encapsulated recombinant clones were subsequently implanted intraperitoneally into C57BL/6 and immunodeficient SCID mice.


RESULTS
Plasma of mice receiving C2C12 and encapsulated MDCK cells had transient therapeutic levels of FVIII in immunocompetent C57BL/6 mice (up to 20% and 7% of physiological levels, respectively). In addition, FVIII delivery in SCID mice was also transient, suggesting that a non-immune mechanism must have contributed to the decline of hFVIII in plasma. Quantitative RT-PCR analysis confirmed directly that the decline of hFVIII is due to a reduction in steady-state hFVIII mRNA, consistent with transcriptional repression. Furthermore, encapsulated cells retrieved from implanted mice were viable, but secreted FVIII ex vivo at three-fold lower levels than the pre-implantation levels. In addition, antibodies to hFVIII were detected in immunocompetent C57BL/6 mice.


CONCLUSIONS
Implantable microcapsules can deliver therapeutic levels of FVIII in mice, suggesting the potential of this gene therapy approach for haemophilia A. The findings suggest vector down-regulation in vivo.
García-Martín
Carmen
C
Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
Chuah
Marinee K L
MK
Van Damme
An
A
Robinson
Kelly E
KE
Vanzieleghem
Beatrijs
B
Saint-Remy
Jean-Marie
JM
Gallardo
Dominique
D
Ofosu
Frederick A
FA
Vandendriessche
Thierry
T
Hortelano
Gonzalo
G
D000818:Animals; D002460:Cell Line; D004285:Dogs; D015536:Down-Regulation; D005169:Factor VIII / Q000096:biosynthesis* / Q000235:genetics*; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D006467:Hemophilia A / Q000628:therapy*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D016513:Mice, SCID; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014161:Transduction, Genetic
D005169:Factor VIII