SELECTION AND USE OF LIGANDS FOR RECEPTOR-MEDIATED GENE DELIVERY TO MYOGENIC CELLS

Identification of myogenic cell targeting ligands is a critical step i n the development of synthetic vectors for gene delivery to skeletal m uscle. Here we describe the screening of six potential targeting ligan ds (insulin, insulin-like growth factor I, iron transferrin, gallium t ransferrin, alpha-bungaro-toxin and carnitine) for their ability to bi nd dystrophin-deficient myotubes in vitro. Those ligands showing high levels of binding to myotubes were then tested on fully differentiated , isolated, viable myofibers. Of the ligands tested, transferrin showe d the most promise based on high levels of binding to myogenic cells, high levels of receptor observed in regenerating fibers of patients wi th Duchenne muscular dystrophy and the ability to direct a large enzym e conjugate to the cytoplasm of myotubes. Finally, we show that incorp oration of transferrin into an artificial virus consisting of poly-L-l ysine-condensed DNA coated with a lipid shell (LPDII formulation) resu lts in ligand-directed delivery of DNA to myogenic cells. This is the first report of gene transfer to myogenic cells using a ligand-directe d synthetic vector. These results suggest that rational design of liga nd-directed fully synthetic, gene delivery vehicles is a viable approa ch to skeletal muscle vector development.