241. Lentivirus Mediated Dystrophin Expression in mdx Muscles

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Top of pageAbstract To study candidate treatments for Duchenne muscular dystrophy, we have generated a series of lentiviral vectors that express various reporter genes and mini-dystrophin cassettes and tested their ability to transduce a variety of cell types in vitro and in vivo. Direct injection of lentiviral vectors into adult skeletal muscle resulted in significantly lower levels of gene expression than were obtained using either AAV or adenoviral vectors. Since an advantage of lentiviral vectors is stable expression of a transgene that has integrated into host genomic DNA, stem cells are considered a good target of lentiviral vectors. During myogenesis, activated-satellite cells or muscle progenitor cells proliferate in the muscle microenvironment. Most of these cells become differentiated and form myofibers, while small numbers of them are stored adjacent to myofibers as mitotically quiescent satellite cells for future muscle regeneration. Skeletal muscle of newborn mice may be a good target for lentiviral vectors, because of relatively high numbers of activated muscle progenitor cells contributing to muscle growth and satellite cell pools. Therefore, we tried targeting satellite cells or muscle progenitor cells using lentivirual vectors expressing dystrophin mini-gene. We demonstrated that relatively higher levels of transuction were obtained with intra-muscular injection into neonatal muscles, and that both muscle fibers and primary cultured satellite cells stably expressed a GFP marker gene. We also demonstrated that lentiviral mediated truncated mini-dystrophin expression in mdx muscles may be useful for correction of pathological changes in dystrophic muscle. These data suggest that myogenic stem cells can be stably transduced with lentiviral vectors and may contribute to stable muscle regeneration in dystrophic muscle by enabling continuous expression of mini-dystrophin, which may have implications for gene therapy of Duchenne muscular dystrophy.