Titanium particles modulate expression of Toll-like receptor proteins.
The role of Toll-like receptors (TLRs) responding to microbial remnants, indolent biofilms or cellular byproducts in aseptic loosening of joint replacements is unknown. Thus, the effect of titanium (Ti) particles on TLR protein levels was evaluated. To create a model of particle-induced inflammation, an intramedullary stainless steel rod with and without Ti particles was bilaterally placed in the femora of 14 mice. The animals were sacrificed at 2 or 10 weeks postoperatively and paraffin-embedded femur sections were evaluated for TLR1, 2, 4, 5, 8, and 9 proteins using immunohistochemistry. Decrease in the number of TLR immunoreactive cells was observed between weeks 2 and 10 in both settings. Furthermore, in the presence of Ti particles, the numbers of TLR immunoreactive cells were lower than in the presence of rod only at both time points, suggesting downregulation of TLR expression by Ti-particles per se. Accordingly, in a short-term 24 h stimulation, downregulation of TLR4 mRNA (p < 0.02) was observed in vitro in RAW 264.7 cells challenged with Ti particles. Results suggest that after an initial inflammatory stage, TLRs are downregulated in response to Ti particles, possibly to inhibit excessive inflammation, although TLR downregulation might at the same time render tissues more susceptible to pathogens.
Department of Medicine (Rheumatology), Institute of Clinical Medicine, Biomedicum Helsinki, University of Helsinki, Finland.
Jukka
J
Pajarinen
Zygmunt
Z
Mackiewicz
Raimo
R
Pöllänen
Michiaki
M
Takagi
Noah J
NJ
Epstein
Ting
T
Ma
Stuart B
SB
Goodman
Yrjö T
YT
Konttinen
D000818:Animals; D001672:Biocompatible Materials / Q000009:adverse effects / Q000737:chemistry; D001854:Bone Marrow Cells / Q000502:physiology; D002460:Cell Line; D005260:Female; D020007:Implants, Experimental; D007249:Inflammation / Q000139:chemically induced / Q000276:immunology; D008264:Macrophages / Q000166:cytology / Q000502:physiology; D008297:Male; D008422:Materials Testing; D051379:Mice; D008810:Mice, Inbred C57BL; D013193:Stainless Steel; D014025:Titanium / Q000276:immunology*; D051193:Toll-Like Receptors / Q000235:genetics / Q000378:metabolism*
D001672:Biocompatible Materials; D051193:Toll-Like Receptors; D013193:Stainless Steel; D014025:Titanium