The present invention provides
muscle-derived
progenitor cells that show long-term survival following
transplantation into body tissues and which can augment non-
soft tissue following introduction (e.g. via injection,
transplantation, or implantation) into
a site of non-
soft tissue (e.g. bone). Also provided are methods of isolating
muscle-derived
progenitor cells, and methods of genetically modifying the cells for
gene transfer therapy. The invention further provides methods of using compositions comprising
muscle-derived
progenitor cells for the augmentation and bulking of mammalian, including human, bone tissues in the treatment of various functional conditions, including
osteoporosis, Paget's
Disease, osteogenesis imperfecta,
bone fracture,
osteomalacia, decrease in bone trabecular strength, decrease in bone cortical strength and decrease in
bone density with old age.