Abstract: A myogenic protein isolate from mammalian bone is provided that stimulates lineage commitment and differentiation of stem cells in vitro and in vivo. The protein isolate is characterized by its ability to cause muscle stem cell differentiation without excessive proliferation of connective tissue proximal to the delivery site. Treated muscle stem cells differentiate into myotubes and multinucleated structures with minimal formation of scar tissue, resulting in functional muscle tissue restoration in vivo, and therefore useful in the treatment of a number of disorders and injuries. The protein isolate is preferably administered by implanting a bioerodible polymer matrix, preferably a surface erodible polymer such as a polyanhydride or a polyorthoester, interspersed with the protein isolate near the site of muscle injury or degeneration, but can be administered directly to cells cultured in vitro.