INFLUENCE OF LIVER ENVIRONMENT ON THE MATURATION OF ISOLATED EPIPHYSEAL CHONDROCYTE TRANSPLANTS

To study the phenomenon of chondrocyte hypertrophy, rat or mouse isola ted epiphyseal chondrocytes were transplanted into the kidney, spleen or liver for 7 days. Each transplant had its own control transplanted intramuscularly. Rat chondrocytes were also placed on a chorioallantoi c membrane of chick embryos, incubated for 11 days and transferred for the next 11 days either onto another chorioallantoic membrane or into rat muscle. The surface area of largest lacunae cross-sections in car tilage produced by transplants was measured as an indicator of chondro cyte hypertrophy. In cartilage from the chorioallantoic membrane chond rocytes remained small but hypertrophied after transfer into a muscle. Lacunae in seven-day-old cartilage nodules in the liver were consider ably larger than in muscle, kidney or spleen. After 7 days matrix calc ification was observed only in liver transplants. Thus, liver environm ent, stimulated chondrocyte hypertrophy. Taken together these results suggest that chondrocytes are unable to hypertrophy spontaneously and that the rate of hypertrophy is subjected to regulation by extra-carti laginous factor(s).