Response of articular chondrocytes to pituitary fibroblast growth factor (FGF)

Rabbit chondrocytes from pooled articular joints have been delineated by their time of attachment to culture flasks after initiation of primary monolayer culture, either attached (48-AT) or floating (48-F) after 48 hours. A general population of chondrocytes (attached after 72 hours, 72-AT) was also studied. The growth-promoting activity of pituitary fibroblast growth factor (FGF) and its effect on sulfated-proteoglycan synthesis was studied on each chondrocyte population in secondary monolayer culture. 3H-thymidine incorporation during a 1-hour pulse was stimulated by FGF (100 ng/ml) in each chondrocyte population. The response of AT-72 chondrocytes to FGF required an additional fetal bovine serum supplement, while 48-F cells responded independent of serum. The response of 48-AT chondrocytes to FGF (100 ng/ml) during a 1-hour pulse with 3H-thymidine was increased in low serum (0.5-2.0%) rather than when high serum (8-10%) was present in the culture medium. FGF reduced 35SO4 incorporation into sulfated-proteoglycans in the 48-AT and 48-F chondrocyte populations, but not in the 72-AT population. The reduction in 35SO4 incorporation in the 48-AT and 48-F chondrocytes was not characterized by alterations in the hydrodynamic size of the sulfated-proteoglycans as measured by Sepharose CL-2B chromatography nor by changes in the types of sulfated-glycosaminoglycans produced. These results indicated that FGF produced quantitative rather than qualitative alterations in chondrocyte sulfated-proteoglycan synthesis. The latter appears uncoupled from the growth-promoting activity of FGF on chondrocytes.