Growth of the mandibular condylar cartilage of the rat in serum-free organ culture

To evaluate the intrinsic capacity for growth, the mandibular condylar cartilage of 4-day-old rats was cultured in a serum-free, chemically-defined medium for 28 days and compared with the condylar cartilage cultured in a serum-supplemented medium and with the normal growth in vivo. Under the serum-free culture conditions, cell proliferation, differentiation into functional chondroblasts and matrix formation continued, but chondroclasia and osteogenesis were absent. This resulted, after 28 days of culture, in an enlarged condylar cartilage with altered proportions, a severe reduction of the prechondroblastic and the transitional zone and a considerable increase of the hypertrophic zone. It appears that the serum-free culture system is unfavourable for endochondral osteogenesis and lacks factors modulating the rate of proliferation, differentiation and maturation of the prechondroblasts. In the functional environment of the condyle, humoral or mechanical factors seem to exert this essential modulating influence on the condylar-cartilage growth.