Gene expression in the process of the regeneration of articular cartilage defect-Comparison with the growth process of the articular joint

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We aimed to understand the regenerative process of the articular cartilage and by comparing with the process of the maturation of the articular cartilage at the aspect of the gene expression. As the result, chondroitin 6-sulfotransferase enzyme took part in the change in the growth process of the amount of articular cartilage, that is, maturities of the articular cartilage, and it was found that this enzyme was chiefly produced from the synovial tissue. Moreover, chondroitin 4-sulfotransferase enzyme took part in the early stage of the growth process of articular cartilage, which recruiting the cells and proliferating the chondrocytes. Expression of C6ST was correlated with the ratio of CS isomers in articular cartilage. Therefore C6ST may play important roles in maintaining or improving the quality of CS in articular cartilage. To compare adult and fetal repair potentials of the articular cartilage, we also investigated the early process after creating superficial defects in the femoral knee cartilage using rat models. In fetuses of 19th days of gestation, both chondrocytes and the extracellular matrix responded remarkably to the superficial defects in 48 hours after the injury. Staining patterns with safranin O revealed that some components of the extracellular matrix around the wound were modified from 1 hour after injury, and the change spread from the limited region to the entire knee cartilage in 24 hours. The chondrocytes in the area surrounding the wound transiently expressed increased level of c-fos from 1 to 6 hours. The wound remained 1 day after birth, I.e. 72 hours after injury, but was completely repaired 10 days after birth. In contrast, neither visible responses nor transient c-fos expression was observed in 12-weeks-old adult articular cartilage in 48 hours after injury.