Interleukin-6 in aseptic loosening of total hip replacement prostheses.
OBJECTIVE
To 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.


METHODS
A 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).


RESULTS
IL-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.


CONCLUSIONS
IL-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.
Konttinen
Y T
YT
Department of Medicine/Invärtes Medicin, Helsinki University Hospital, Finland. yrjo.konttinen@helsinki.fi
Xu
J W
JW
Waris
E
E
Li
T F
TF
Gómez-Barrena
E
E
Nordsletten
L
L
Santavirta
S
S
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D001207:Asepsis; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006622:Hip Prosthesis; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007124:Immunoenzyme Techniques; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery*; D011475:Prosthesis Failure; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013582:Synovial Fluid / Q000378:metabolism; D013583:Synovial Membrane / Q000378:metabolism* / Q000473:pathology
D015850:Interleukin-6; D012333:RNA, Messenger