Studies in mice showed tremendous promise for the eventual clinical utility of myoblast transplantation to treat human muscular dystrophies. Initial attempts to translate the murine studies to humans, however, were not successful, due in part to limited engraftability of expanded donor myoblasts. Conventionally, muscle cells have been cultured on collagen-coated tissue culture-treated polystyrene. However, this promotes lineage progression and differentiation of cells, which limits engraftment potential. This unit describes the isolation of canine muscle-derived cells, ex vivo expansion of cells on plates coated with a modified Notch ligand, and the xenotransplant method used to evaluate engraftment potential. Activation of Notch signaling in freshly isolated canine muscle-derived cells with Delta-1(ext)-IgG inhibits myogenic differentiation, and maintains cells earlier in myogenic lineage progression. Delta-1(ext)-IgG-expanded cells engraft into the regenerating muscle of NOD/SCID mice more effectively than control cells expanded on human IgG, as evidenced by a significant increase in the number of muscle fibers expressing canine dystrophin in recipient murine muscle. Therefore, this protocol provides the basis for further developing culture conditions for ex vivo expansion of donor muscle cells for transplant.