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

Abstract

The aim of this study was to establish a human macrophage cell culture system to examine the effect of polyethylene (PE) and titanium particles on cytokine release by macrophage-like cells (MLC) and to quantify this response with respect to the nature and concentration of particles. Human monocytic leukemia cells were differentiated under standard conditions with vitamin D 3 and granulocyte macrophage-colony-stimulating factor. Cells were characterized by fluorescence-activated cell-sorter Scan of CD 14 expression analysis as well as a phagocytosis test exploiting fluorescence-labeled particles of bacterial walls. To achieve a relevant contact between the floating PE particles (approximately I μm 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)-Iβ, IL-8, and tumor necrosis factor (TNF)-α using the enzyme-linked immunosorbent assay technique in the absence or presence of particles. Rotation of incubated MLC alone did not influence the secretion of TNF-α, but it enhanced secretion of IL-Iβ and IL-8 about 30-fold compared to background levels. Both PE and titanium particles significantly enhanced MLC cytokine release, the amount of which depended on the concentration of particles. Using 40 × 10 8 PE particles (0.7 × 10 8 titanium particles) and 10 6 MLC, the maximal release of IL-Iβ was about 20-fold (7-fold titanium particles) higher than that of the rotating control sample. The stimulation of IL-8 release was 4-fold (3-fold titanium particles) and of TNF-α 300-fold (170-fold titanium particles) compared to controls. MLC were viable (>90% cell survival) at concentrations less than 108 × 10 8 polyethylene particles per 10 6 MLC and 16 × 10 8 titanium particles per 10 6 MLC. Rotation per se as well as exposure to increasing concentrations of PE and titanium particles stimulates cytokine release (TNF-α, IL-Iβ, IL-8) by macrophages in vitro. This in vitro model resembles the in vivo situation near arthroplasties, where implant particles make contact with inflammatory cells, such as macrophages. Cytokine release by macrophages may impair osteoblast function as well as stimulate bone resorption by osteoclasts and 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.