Effects of Cell Density on Proliferation and Matrix Synthesis of Chondrocytes Embedded in Atelocollagen Gel

The effects of cell density on the proliferation and chondroitin sulfate synthesis of chondrocytes embedded in Atelocollagen gel were examined. Chondrocytes of 21 10-week-old Japanese white rabbits isolated by collagenasedigestion were embedded in Atelocollagen gel and cultured in Dulbecco's modified Eagles medium at cell densities of 2 × 10 5 cells/ml (10 5 group), 2 x 10 6 cells/ml (10 6 group), and 2 x 10 7 cells/ml (10 7 group) for 4 weeks. Chondrocytes in the 10 5 group gradually proliferated more than the other two groups. In contrast, most chondrocytes in the 10 7 group showed increased capability to produce chondroitin 6-sulfate. Cartilage-like tissue was produced from high-density cultures (10 7 cells/ml), although a decrease in cell number was seen. Even in three-dimensional cultures, the proliferation and chondroitin sulfate synthesis of chondrocytes were influenced by the cell density. These results are informative for the clinical application of chondrocyte transplantation in three-dimensional cultures for cartilage repair.