INTERLEUKIN-1 AND COLLAGENASES AROUND LOOSENING TOTAL HIP PROSTHESES

Objectives. The present study was carried out to assess the expression of IL-1 in periprosthetic tissue and to relate it to local collagenas e levels. Methods. Interface tissue between the implant and bone was o btained fr om hip revision operations and was compared to healthy join t capsular tissue. Membrane bound IL-1 alpha was stained using the avi din-biotin-peroxidase complex method nod was quantified using morphome try (VIDAS image analysis system). Soluble IL-1 beta was measured by E LISA. IL-1 levels were compared to collagenase activities in the same tissue as assessed by the degradation of triple helical type I collage n 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). Simila rly, 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 int erface (26.3 x 10(-6) +/- 7.57 x 10(-6) IU/l, p < 0.01) than in contro l 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, suggesti ng that they may play a role in loosening. However, the correlations b etween IL-1 and collagenase were not significant, indicating, that IL- 1 is probably not the only cytokine involved in the regulation of coll agenase activity in vivo. IL-1 may also contribute to loosening by its osteoclast activating properties.