• Y T Konttinen, J W Xu, E Waris, T F Li, E Gómez-Barrena, L Nordsletten, and S Santavirta.
• Department of Medicine/Invärtes Medicin, Helsinki University Hospital, Finland. yrjo.konttinen@helsinki.fi
• Clin Exp Rheumatol. 2002 Jul 1; 20 (4): 485-90.

ObjectiveTo investigate the level of interleukin-6 (IL-6) expression in the synovial-like interface membrane (SLIM) and in the pseudosynovial tissue surrounding the artificial hip joints, as well as in the pseudosynovial fluid from aseptically loosened total hip replacement (THR) prostheses.MethodsA series of methods were used in this study including immunohistochemical staining, double immunofluorescence labeling, enzyme-linked immunosorbent assay (ELISA), and reverse transcriptase polymerase chain reaction (RT-PCR).ResultsIL-6 was found in all SLIM and the pseudosynovial tissue samples from aseptic loosening of THR. Semi-quantitative morphometry showed that IL-6 containing cells were more numerous in the SLIM (911 +/- 197; p < 0.01) and the pseudosynovial tissue samples (883 +/- 310; p < 0.01) than in the control synovial tissue (291 +/- 184). Double labeling confirmed that macrophages and fibroblasts were the predominant cell types expressing IL-6. These findings were confirmed by RT-PCR. ELISA revealed no difference in the IL-6 concentration between the pseudosynovial fluid and the control synovial fluid obtained from the patients undergoing hip arthroscopy.ConclusionsIL-6 locally produced in SLIM may in a paracrine manner contribute to periprosthetic osteolysis of the nearby bone. In contrast, fluid phase IL-6 does not seem to contribute to this end.

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