DISCOORDINATE EXPRESSION OF IL-1-ALPHA AND IL-1-BETA IN INTERFACIAL MEMBRANES OF FAILED JOINT PROSTHESES

Bone resorption following either cemented or uncemented total hip replacement has been implicated as an important etiologic factor in aseptic loosening of prostheses, the most frequent cause of clinical failure. Interleukin-1 beta (IL-1 beta), collagenase and prostaglandin E(2) are considered to play key roles in pathological bone resorption. We have measured the actual levels and quantified the genes coding for several cytokines [IL-1 alpha, IL-1 beta, IL-4, IL-6, platelet-derived growth factors (PDGF), transforming growth factor-beta (TGF beta) and tumor necrosis factor-alpha (TNF alpha)] in interfacial membranes obtained from cemented or uncemented loosened joint replacements. IL-1 alpha, IL-6 and TNF alpha were barely detectable in the interfacial membranes either at protein or mRNA levels, while IL-1 beta and TGF beta were found to be expressed at the highest levels in freshly isolated tissues. However, the expression of IL-1 alpha increased 10-1000-fold either in isolated cells or explant cultures of interfacial membranes within 24 h. The expression of other cytokines, measured directly in tissue or cells, did not suggest a discoordinate expression of bone-resorbing cellular mediators.