Addressing the National Meeting of the Orthopedic Research Society in Anaheim, CA, at the beginning of February, Johnny Huard described work at the University of Pittsburgh and the Children's Hospital of Pittsburgh demonstrating the ability of muscle-derived stem cells to form bone when transplanted into mice. Huard and his colleagues accomplished this by isolating a special population of myogenic cells within skeletal muscle that appear capable of forming bone when stimulated in vitro with bone morphogenic protein BMP-2. To test whether these bone-forming cells could be induced experimentally, they then injected genetically altered muscle-derived stem cells expressing BMP-2 protein and β-galactosidase into the hindlimb muscles of mice. As predicted, the BMP-2-expressing cells were able to form ectopic bone in the muscle in vivo. As Huard explains: "The colocalization of β-galactosidase and the bone marker, osteocalcin, conclusively shows that these cells are not trapped, but active in bone formation." The findings may be clinically relevant to orthopedic patients suffering from severe bone fractures, as muscle-derived stem cells could be used to develop faster, more economical means of delivering osteoprogenitor cells directly to the wound site. Experiments are currently underway to investigate whether muscle stem cells are truly pluripotent.