Interleukin-1-like factor (mononuclear cell factor) modulates proteoglycan synthesis in cultured human synovial cells

Cultured human synovial cells treated with an interleukin-1-like mononuclear cell factor incorporated more 35S in proteoglycans than control cultures, but the radioactivity distribution between medium and cell layer was not modified. Proteoglycans were synthesized essentially in monomeric form and the mononuclear cell factor increased the molecular weight of these monomers. The [3H]hexosamine/[14C]serine ratio in purified proteoglycans on the one hand, and the study of [35S]glycosaminoglycan molecular weight, on the other hand, indicated that this increase is not modulated through enhanced synthesis of core protein but by an increase in the glycosaminoglycan chain length. After enzyme hydrolysis, dermatan sulfate (62% of the total glycosaminoglycans) and chondroitin 4/6-sulfate (30%) were found to be the major glycosaminoglycans synthesized by cultured synovial cells, and the existence of 8% heparan sulfate was evidenced by nitrous acid treatment. In the presence of the mononuclear cell factor, the dermatan sulfate synthesis was decreased (47%), with a concomitant increase of chondroitin sulfate synthesis (45%).