Cytokine response of human macrophage-like cells after contact with polyethylene and pure titanium particles

The aim of this study was to establish a human macrophage cell culture syst em to examine the effect of polyethylene (PE) and titanium panicles on cyto kine release by macrophage-like cells (MLC) and to quantify this response w ith respect to the nature and concentration of particles. Human monocytic l eukemia cells were differentiated under standard conditions with vitamin D- 3 and granulocyte macrophage-colony-stimulating factor. Cells were characte rized by fluorescence-activated cell-sorter Scan of CD 14 expression analys is as well as a phagocytosis test exploiting fluorescence-labeled particles of bacterial walls. To achieve a relevant contact between the floating PE panicles (approximately 1 mu m in size) and MLC, a rotation device was used (15 rotations/min) during incubation. The same was done with the titanium particles. Cell culture supernatants were then analyzed for interleukin (IL )-1 beta, IL-8, and tumor necrosis factor (TNF)-alpha using the enzyme-link ed immunosorbent assay technique in the absence or presence of panicles. Ro tation of incubated MLC alone did not influence the secretion of TNF-alpha. but it enhanced secretion of IL-1 beta and IL-8 about 30-fold compared to background levels. Both PE and titanium particles significantly enhanced ML C cytokine release, the amount of which depended on the concentration of pa rticles. Using 40 x 10(8) PE particles (0.7 x 10(8) titanium particles) and 10(6) MLC, the maximal release of IL-1 beta was about 20-fold (7-fold tita nium particles) higher than that of the rotating control sample. The stimul ation of IL-8 release was 4-fold (3-fold titanium particles) and of TNF-alp ha 300-fold (170-fold titanium particles) compared to controls. MLC were vi able (>90% cell survival) at concentrations less than 108 x 10(8) polyethyl ene particles per 10(6) MLC and 16 x 10(8) titanium panicles per 10(6) MLC. Rotation per se as well as exposure to increasing concentrations of PE and titanium particles stimulates cytokine release (TNF-alpha, IL-1 beta, IL-8 ) by macrophages in vitro. This in vitro model resembles the in vivo situat ion near arthroplasties, where implant particles make contact with inflamma tory cells, such as macrophages. Cytokine release by macrophages may impair osteoblast function as well as stimulate bone resorption by osteoclasts an d macrophages, thereby causing aseptic loosening of arthroplasties. Our in vitro model provides a reproducible human cell system that might shed light on the pathogenesis of particle disease and might serve as a reproducible in vitro test system for the biocompatibility of foreign materials.