CHARACTERIZATION OF THE CELLS IN THE REPAIR TISSUE OF FULL-THICKNESS ARTICULAR-CARTILAGE DEFECTS

It is well established that a full-thickness articular cartilage defec t is repaired with a fibrocartilaginous tissue, cells of which are der ived from undifferentiated mesenchymal stem cells in the bone marrow. To characterize the repair cells biochemically, full-thickness defects were created in rabbit knee joints and the repair tissues taken at 3, 6, and 12 weeks after surgery. The repair cells were cultured and exa mined biochemically to investigate the effects of four exogenous growt h factors with regard to the metabolism of type II collagen and proteo glycans. A significant increase of carboxy-terminal type II procollage n peptide production was observed in the conditional medium of the rep air cells, especially taken at 6 weeks after surgery, in the presence of each growth factor. Glycosaminoglycan content was also in creased a nd proteoglycan synthesis stimulated. The repair cells taken at the ea rly stage of the repair process could originally have more activity of type II collagen synthesis, and the growth factors used could enhance the differentiation of the repair cells in vitro.