Effect of titanium surface topography on macrophage activation and secretion of proinflammatory cytokines and chemokines

The macrophage has a major role in normal wound healing and the reparative process around implants. Murine macrophage-like cells RAW 264.7 were used to investigate the effect of titanium surfaces on macrophage activation and secretion of proinflammatory cytokines [interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha] and chemokines (monocyte chemoattractant protein-1 and macrophage inflammatory protein-1alpha). Four topographies were used: those produced by mechanically polishing, coarse sand blasting, acid etching, and sandblasting and acid etching (SLA). Macrophages were plated on the four titanium surfaces at a population density of 5 X 10(5) cells/mL/well. Tissue culture plastic and tissue culture plastic plus lipopolysaccharide (LPS) served as negative and positive control, respectively. In addition, all surfaces were tested for their effects on macrophages in the presence of LPS. Supernatants were collected for assays after 6, 24, and 48 h and the numbers of macrophages attached to the surfaces were quantified using the DAPI (4,6-di-amidino-2-phenylindole) assay. Cytokine and chemokine levels were measured with sandwich enzyme-linked immunosorbent assays. Statistical co:nparison between the surfaces and the controls was determined by using the two-way analysis of variance including interaction effect (two tailed and p less than or equal to 0.05). Unstimulated macrophages increased their secretion of the proinflammatory cytokine (TNF-alpha) when attached to rough surfaces (acid etching and SLA, p less than or equal to 0.05). In macrophages stimulated with LPS, the roughest surface SLA produced higher levels of IL-Ibeta, IL-6, and TNF-alpha at 24 and 48 h than all other surfaces (p less than or equal to 0.05). Surface topography also modulated the secretion of the chemokines monocyte chemoattractant protein-1 and macrophage inflammatory protein-la by macrophages. Unstimulated macrophages attached to the SLA surface downregulated their production of chemokines (p 0.05) whereas LPS-stimulated macrophages attached to the SLA surface upregulated their production (p less than or equal to 0.05). Moreover, the SLA surface was found to act synergistically with LPS as well as the combination of blasting and etching features of the SLA surface resulted in significant release of proinflammatory cytokines and chemokines by stimulated macrophages at 24 and 48 h (p less than or equal to 0.05). This hi vitro study has demonstrated that surface topography, in particular the SLA surface, modulated expression of proinflammatory cytokines and chemokines by macrophages in a time-dependent manner. (C) 2004 Wiley Periodicals, Inc.