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