Thyroid hormone-induced chondrocyte terminal differentiation in rat femur organ culture.

Thyroid hormone plays a role in skeletal maturation. The present study was undertaken to investigate the effect of thyroid hormone on growth and maturation of the epiphyseal cartilage in the rat femur organ culture system. The femora increased in both weight and size over time in culture in the absence of serum. The growth rate was suppressed by thyroxine treatment. Thyroxine induced chondrocyte hypertrophy in the area adjacent to the articular surface in the femoral condyle. In this area, the expression of type X collagen, a marker of chondrocyte terminal differentiation, was detected after 21 days in culture by immunohistochemistry and reverse transcription/polymerase chain reaction. These data suggest that thyroxine suppresses cartilage growth by stimulating chondrocyte terminal differentiation.