Chondrocyte source for cartilage regeneration in an immature animal: Is iliac apophysis a good alternative

Background: Autologous articular cartilage at present forms the main source of chondrocytes for cartilage tissue engineering. In children, iliac apophysis is a rich and readily accessible source of chondrocytes. This study compares the growth characteristics and phenotype maintenance of goat iliac apophysis growth plate chondrocytes with those sourced from goat articular cartilage, and thereby assesses their suitability for autologous chondrocyte transplantation in immature animals for growth plate and articular cartilage regeneration. Materials and Methods: Four sets of experiments were carried out. Cartilage samples were harvested under aseptic conditions from goat iliac apophysis and knee articular cartilage. The chondrocytes were isolated in each set and viable cells were counted and subsequently cultured as a monolayer in tissue culture flasks containing chondrogenic media at 2.5 × 10 ³ cells/cm ². The growth was periodically assessed with phase contrast microcopy and the cells were harvested on 8 ^th and 15 ^th days for morphology, cell yield, and phenotype assessment. Student's t-test was used for comparison of the means. Results: Confluence was reached in the iliac apophysis growth plate chondrocytes flasks on the 10 ^th day and the articular cartilage chondrocytes flasks on the 14 ^th day. Mean cell count of growth plate chondrocytes on the 8 ^th day was 3.64 × 10 ⁵ (SD = 0.601) and that of articular cartilage chondrocytes was 1.40 × 10 ⁵ (SD = 0.758) per flask. The difference in the means was statistically significant (P = 0.003). On the 15 ^th day, the mean cell number had increased to 1.35 × 10 ⁶ (SD = 0.20) and 1.19 × 10 ⁶ (SD = 0.064) per flask, respectively. This difference was not statistically significant (P = 0.26). The population doubling time on the 8 ^th day of cell culture was 3.18 and 6.24 days respectively, for iliac apophyseal and articular cartilage chondrocytes, which was altered to 3.59 and 3.1 days, respectively, on the 15 ^th day. The immunocytochemistry showed 100% retention of collagen 2 positive and collagen 1 negative cells in both sets of cultures in all samples. Conclusion: Iliac apophysis is a rich source of chondrocytes with a high growth rate and ability to retain phenotype when compared to articular cartilage derived chondrocytes. Further in vivo studies may determine the efficacy of physeal and articular repair in children with apophyseal chondrocytes.