Their findings were presented today (Feb. 2, 2003) at the annual meeting of the Orthopedic Research Society.
Using a biochemical cocktail of steroids and growth factors, the researchers have "retrained" specific adult stem cells that would normally form the structure of fat into another type of cell known as a chondrocyte, or cartilage cell. During this process, if the cells were grown in the presence of "room air," which is about 20 percent oxygen, the stem cells tended to proliferate; however, if the level of oxygen was reduced to 5 percent, the stem cells transformed into chondrocytes.
This finding is important, the researchers say, because this low oxygen level more closely simulates the natural conditions of cartilage, a type of connective tissue that cushions many joints throughout the body. However, since it is a tissue type poorly supplied by blood vessels, nerves and the lymphatic system, cartilage has a very limited capacity for repair when damaged. For this reason, the Duke investigators are searching for a bioengineering approach to correct cartilage injury.
"Our findings suggest that oxygen is a key determinant between proliferation and differentiation, and that hypoxia, or low oxygen levels, is an important switch that tells cells to stop proliferating and start differentiating,' said David Wang, a fourth-year medical student at Duke, who presented the results of the Duke research.
Farshid Guilak, Ph.D., director of orthopedic research and senior member of the Duke team, said that the combination of growth factors sets the adult stem cells on the right path, while controlling oxygen levels inspires the cells to more readily transf
Contact: Richard Merritt
Duke University Medical Center