Autologous mesenchymal progenitor cells in articular cartilage repair

The lack of repair of articular cartilage where the damage does not penetra te the subchondral bone indicates the importance of marrow components in th e repair of the articular cartilage. In adult animals, there is an inabilit y of articular cartilage chondrocytes to heal chondral defects, but if the damage extends beyond the subchondral bone, a repair process ensues in whic h mesenchymal progenitor cells migrate into the injured site and undergo ch ondrogenic differentiation. However, analysis of animal models and human bi opsy samples indicates that fibrocartilage, rather than true articular cart ilage is the predominant tissue synthesized, To improve this outcome, the u se of cell based implants of culture expanded progenitor cells from various sources has been proposed and attempted. This paper describes some of the age related differences in the natural repair of osteochondral defects, the in vitro characterization of the chondrogenic potential of certain mesench ymal cell types, and some of the characteristics required of cell and matri x constructs that may be used for repair or regeneration of articular carti lage.