Repair of Articular Cartilage Defects Using Mesenchymal Stem Cells

Degeneration of articular cartilage in osteoarthritis is a serious medical problem. We have isolated a population of cells from the connective tissue of mammals termed mesenchymal stem cells (MSCs) for their apparent unlimited growth potential and their ability to differentiate into several phenotypes of the mesodermal lineage, including cartilage and bone. These qualities make them ideal candidates for cartilage repair. We isolated MSCs from adult rabbit muscle and cultured them in vitro into porous polyglycolic acid polymer matrices. The matrices were implanted into 3-mm-diameter full thickness defects in rabbit knees with empty polymer matrices serving as the contralateral controls. The implants were harvested 6 and 12 weeks postop. At 6 weeks, the controls contained fibrocartilage while the experimentals seemed to contain undifferentiated cells. By 12 weeks postop, the controls contained limited fibrocartilage and extensive connective tissue, but no subchondral bone. In contrast, the implants containi...