University of Pittsburgh Findings at Feb. 1-4 Orthopaedic Research Society in Anaheim
PITTSBURGH, Feb. 1 -- University of Pittsburgh researchers have found that muscle-derived stem cells are capable of forming bone inside animals, opening a field of research that may one day allow physicians to deliver bone-producing cells in a highly specific manner to fractures which currently lead to incomplete healing.
In a clever set of experiments, University of Pittsburgh researchers have isolated a group of bone-precursor cells from skeletal muscle, transferred into them a gene that fosters bone growth and injected these genetically altered cells into mice. The results show that these muscle-derived stem cells are capable of forming bone inside animals, opening a field of research that may one day allow physicians to deliver bone-producing cells in a highly specific manner to fractures which currently lead to incomplete healing. The results are being presented Feb. 1 at the annual national meeting of the Orthopaedic Research Society in Anaheim, Calif.
"These results provide a good indication that stem cells for bone live within muscle," said Johnny Huard, Ph.D., assistant professor of orthopaedic surgery and of molecular genetics and biochemistry at the University of Pittsburgh, and director of the Growth and Development Laboratory at Children's Hospital of Pittsburgh.
In the experiments, Dr. Huard's research team first isolated several groups of muscle cells taken from two strains of mice. For five days, they bathed the different groups of cells in bone morphogenic protein 2 (bmp-2), which stimulates cells to form bone. Only one group of cells produced alkaline phosphatase, a marker for osteoblasts (bone cells). Without stimulation using bmp-2, none of the cell groups produced this enzyme.
"In the next step, we took the bmp-2-sensitive cells and transferred two genes into them. First, we put the gene for bmp-2 into the cells so that they could produce bmp-2 and stimulate their own transformation into bone," noted Dr. Huard. "We also put in a marker gene that would allow us to track the movement of the cells within an animal."
The research team injected the genetically altered muscle-derived cells into muscles of SCID mice, mice that do not reject the normally foreign-looking cells from different strains of mice. Two weeks later, the investigators examined the treated muscles in the SCID mice and discovered that the injected cells were capable of participating in bone formation.
The investigators are currently conducting experiments to investigate whether these muscle-derived cells are pluripotent stem cells and can differentiate into osteogenic (bone) and chondrogenic (cartilage) cell lineages.