SUCCESSFUL TRANSPLANTATION OF GENETICALLY CORRECTED DMD MYOBLASTS FOLLOWING EX-VIVO TRANSDUCTION WITH THE DYSTROPHIN MINIGENE

Myoblast transplantation and gene therapy are two promising therapeuti cal approaches for the treatment of Duchenne Muscular-Dystrophy (DMD). So far, both strategies have met many hurdles, mainly because of immu ne reactions. In this study, we investigated a third and novel strateg y based on the combination of these two basic ones, i.e., transplantat ion of genetically modified myoblasts. Ne first derived a primary cult ure from a muscle biopsy of a young DMD patient (3 years old). Adenovi ral-mediated dystrophin gene transfer into these DMD cultures and expr ession of the dystrophin transgene were achieved in vitro. The transdu ced cultures were then transplanted the same day in immunodeficient SC ID mouse muscles, Three weeks following the graft, many human dystroph in positive fibers were observed throughout sections of the injected. muscles. However; many fibers expressed human MHC antigens without exp ressing human dystrophin due to the low percentage of infected primary muscle cells in vitro (even when a high MOI [400] was used) and to a reduction and even to a complete loss of transgene copy number curing myoblast replication. From our results, we conclude that, although not at a high proportion, (1) DMD primary myoblast cultures are infectabl e by adenoviruses; (2) they can be efficiently transplanted hack in a muscle, leading to normal fusion of infected myoblasts with the host f ibers; and (3) they can correct the dystrophin deficiency in the host fibers by the expression of a mini-dystrophin transgene. (C) 1998 Acad emic Press.