Conditioned medium factors of rabbit cranio-facial chondrocytes stimulate their own syntheses of sulfated glycosaminoglycans and DNA.

Previously, we reported methods for isolating chondrocytes from the craniofacial cartilage and culturing them in vitro. The cells actively synthesize glycosaminoglycan (GAG), a marker of the differentiated phenotype of chondrocytes and respond well to PTH and glucocorticoids. It has been suggested that chondrocytes produce somatomedin-like growth factors which support their own growth and GAG synthesis. In the present study, we reported studies on the effect of conditioned medium obtained from cultures of rabbit craniofacial chondrocytes on GAG and DNA syntheses in the same chondrocyte cultures. Serum-free medium, conditioned by exposure to rabbit chondrocytes from mandibular condyle, nasal septum and sphenooccipital synchondrosis in monolayer culture stimulated not only the synthesis of GAG by the same cells but also their own DNA synthesis. The stimulation of the syntheses of GAG and DNA by the conditioned-medium factor were concentration-dependent. In addition, these three kinds of conditioned media stimulated GAG and DNA syntheses of other types of chondrocytes. These findings suggest that rabbit chondrocytes from the craniofacial complex release factors into the culture medium that enhance their own growth and expression of the differentiated phenotype of chondrocytes as well as that of costal chondrocytes.