The present invention provides muscle-derived progenitor cells (MDCs) that show long-term survival following transplantation into body tissues and which can augment soft tissue following introduction into a site of soft tissue. Also provided are methods of isolating MDCs. The invention further provides methods of using compositions comprising MDCs for the augmentation and bulking of mammalian, including human, soft tissues in the treatment of various cosmetic or functional conditions, including malformation, injury, weakness, disease, or dysfunction. The invention also relates to uses of MDCs for the treatment of cosmetic or functional conditions, including, but not limited to skeletal muscle weakness, muscular dystrophy, muscle atrophy, spasticity, myoclonus and myalgia. The invention also relates to the use of MDCs for the increase of skeletal muscle.
