The synergism between platelet-activating factor and interleukin-1 on cartilage breakdown.

The breakdown of rat articular cartilage has been studied in vivo and in vitro to observe the effect of platelet-activating factor (PAF) and interleukin-1 alpha (IL-1 alpha) on the net loss of glycosaminoglycan (GAG). When PAF was infused over a 2-week period into rats, there was no increased breakdown of implanted, cotton-wrapped, femoral head cartilage. However, there was a loss of proteoglycan from the femoral head cartilage of the recipient rats (native cartilage). This loss from the native cartilage was not apparent if the animal had not been implanted with cartilage. Using an in vitro system, the effect of PAF and IL-1 alpha on rat femoral head cartilage was further examined. Separately, neither agent had any significant effect on GAG content. However, when combined, there was a significant loss of GAG. The significance of these results is discussed.