Chondrocyte progenitor cells are found in the surface zone of articular cartilage. This population of cells exhibits high affinity for fibronectin, possesses a high colony-forming efficiency, expresses the cell fate selector gene Notch 1 and also exhibits phenotypic plasticity.
A cartilage biopsy was taken from the superomedial edge of the femoral condyle and the lateral intercondylar notch in the same location, or from the superlateral edge of the femoral condyle. The tissue obtained is two or three small slivers of partial to full thickness cartilage with a depth the size of a fingernail clipping, with a mean weight of 280 mg, and contains 2600 cells/mg. During the time of biopsy, 100 mL of venous blood is collected from the patient for preparation of autologous serum.
Individual chondrocytes are isolated by collagenase digestion overnight and cultured in DMEM/F12 with autologous serum (10%). Primary cultures are performed in 25 cm2 flasks and after one week, cells are trypsinised and passaged to 75 cm2 flasks at a cell density of 8000 cells/cm2. After two weeks, cells are trypsinised, washed and resuspended to a treatment density of 30 million cells/mL before transplantation.