Synergism of basic fibroblast growth factor and interleukin-1 beta to induce articular cartilage-degradation in the rabbit.

Interleukin-1 beta (IL-1) and basic fibroblast growth factor (bFGF) synergistically induce proteases in vitro. To investigate this synergy in vivo, we injected IL-1 and bFGF alone and in combination into the lapine knee. Three days later, we compared the glycosaminoglcan (GAG) content of tibial cartilage of cytokine-treated and contralateral control-knees. IL-1 caused significant increases of granulocytes and GAG in the synovial fluid but minor cartilage-GAG losses of 11, 11 & 16% at 5kU, 10 kU and 100 kU IL-1/knee, respectively. bFGF at 2 and 10 micrograms/knee caused no changes. 10 micrograms bFGF in combination with 10 kU IL-1 induced a 33% GAG loss (p less than 0.01) that lasted 21 days. IL-1/bFGF induced cartilage degradation may be useful to 1) evaluate agents which modulated proteoglycan catabolism and 2) assess factors that accelerate cartilage-repair.