Creating Cartilage from Stem Cells

In their research on turning adult stem cells isolated from fat into cartilage, Duke Medical Center researchers have demonstrated that the level of oxygen present during the transformation process is a key switch in stimulating the stem cells to change. Their findings were presented in February 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 changed 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 repairing itself when damaged. Duke's investigators are searching for a way to heal cartilage injury using bioengineering.

" 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," says David Wang, a fourth-year medical student at Duke, who presented the results of the Duke research.

Researchers anticipate that patients to benefit from this research would be those who have suffered some sort of cartilage damage from injury or trauma. They foresee a time when entire joints ravaged by osteoarthritis can be relined with bioengineered cartilage.