A COMPARISON OF CHONDROCYTE PROTEOGLYCAN METABOLISM IN MONOLAYER AND AGAROSE CULTURES

Bovine chondrocyte cultures were established in agarose and in monolay ers to compare the effects of cytokines and drugs on matrix metabolism . The production of sulfated glycosaminoglycans (S-GAG) from the mediu m and cell surface compartments were measured by a dimethylmethylene b lue assay. In the agarose cultures most of the proteoglycan remained i n the agar, but was continuously released into the medium for more tha n 50 days. In the monolayers, the cell surface compartment became satu rated with S-GAG in 5-6 days. Then a time-dependent decrease of accumu lation occurred in the medium after 8-10 days. The anabolic effects of insulin-like growth factor (IGF) and a protein kinase C activator (PM A) were measured in these cultures. IGF and PMA increased S-GAG accumu lation in the medium from monolayers but not from agarose cultures. In the agarose cultures, S-GAG was released into the medium after these cultures were changed to serum-free test conditions. This release over shadowed any increase in S-GAG synthesis. The catabolic effect of IL-1 was more evident in the monolayers than in the agarose cultures. Agar ose cultures maintain the chondrocyte phenotype longer than monolayers but for initial drug studies monolayer cultures appear to be more app ropriate.