Interleukin-1 and collagenases around loosening total hip prostheses

The present study was carried out to assess the expression of IL-1 in periprosthetic tissue and to relate it to local collagenase levels.

Interface tissue between the implant and bone was obtained from hip revision operations and was compared to healthy joint capsular tissue. Membrane bound IL-1 alpha was stained using the avidin-biotin-peroxidase complex method and was quantified using morphometry (VIDAS image analysis system). Soluble IL-1 beta was measured by ELISA. IL-1 levels were compared to collagenase activities in the same tissue as assessed by the degradation of triple helical type I collagen monomers analyzed by SDS-PAGE/laser densitometry.

The IL-1 alpha staining index was high in interface tissue (7.25 +/- 1.28, p < 0.01) compared to normal joint capsular tissue (0.50 +/- 0.04). Similarly, IL-1 beta levels (ng/ml; ELISA) were high in such tissue (139.0 +/- 71.9 vs 0 +/- 0, p < 0.02). Total collagenase was higher in the interface (26.3 x 10(-6) +/- 7.57 x 10(-6) IU/l, p < 0.01) than in control tissue (0.55 x 10(-6) +/- 0.44 x 10(-6) IU/l). IL-1 alpha (r = -0.04, p > 0.05) and IL-1 beta (r = 0.25, p > 0.05) did not correlate with collagenase activity in interface tissue.

Both IL-1 (alpha and beta) and collagenase are up-regulated around loose THR, suggesting that they may play a role in loosening. However, the correlations between IL-1 and collagenase were not significant, indicating, that IL-1 is probably not the only cytokine involved in the regulation of collagenase activity in vivo. IL-1 may also contribute to loosening by its osteoclast activating properties.