Electro transfer of naked DNA in the skeletal muscles of animal models of muscular dystrophies

The electrotransfer of naked DNA has recently been adapted to the transduct ion of skeletal muscle fibers. We investigated the short- and long-term eff icacy of this methodology in wild-type animals and in mouse models of conge nital muscular dystrophy (dy/dy, dy(2J)/dy(2J)), or Duchenne muscular dystr ophy (mdx/mdx). Using a reporter construct, the short-term efficacy of fibe r transduction reached 40% and was similar in wild-type, dy/dy and dy(2J)/d y(2J) animals, indicating that ongoing muscle fibrosis was not a major obst acle to the electrotranster-mediated gene transfer. Although the complete r ejection of transduced fibers was observed within 3 weeks in the absence of immunosuppression, the persistency was prolonged over 10 weeks when transi ent or continuous immunosuppressive regimens were used. Using therapeutic p lasmids, we demonstrated that electrotransfer also allowed the transduction of large constructs encoding the laminin alpha2 chain in dy/dy mouse, or a chimeric dystrophin-EGFP protein in mdx/mdx mouse. The correct sarcolemmal localization of these structural proteins demonstrated the functional rele vance of their expression in vivo, with a diffusion domain estimated to be 300 to 500 mum. However, degeneration-regeneration events hampered the long term stability of transduced fibers. Given its efficacy for naked DNA trans fer in these models of muscular dystrophies, and despite some limitations, gene electrotransfer methodology should be further explored as a potential avenue for treatment of muscular dystrophies.