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

Abstract

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)-1 beta, IL-6, and tumor necrosis factor (TNF)-alpha] and chemokines (monocyte chemoattractant protein-1 and macrophage inflammatory protein-1 alpha). 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 comparison between the surfaces and the controls was determined by using the two-way analysis of variance including interaction effect (two tailed and p < or = 0.05). Unstimulated macrophages increased their secretion of the proinflammatory cytokine (TNF-alpha) when attached to rough surfaces (acid etching and SLA, p < or = 0.05). In macrophages stimulated with LPS, the roughest surface SLA produced higher levels of IL-1 beta, IL-6, and TNF-alpha at 24 and 48 h than all other surfaces (p < or = 0.05). Surface topography also modulated the secretion of the chemokines monocyte chemoattractant protein-1 and macrophage inflammatory protein-1 alpha by macrophages. Unstimulated macrophages attached to the SLA surface down-regulated their production of chemokines (p < or = 0.05) whereas LPS-stimulated macrophages attached to the SLA surface up-regulated their production (p < or = 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 < or = 0.05). This in 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.

Effects of Titanium Surfaces on the Developmental Profile of Monocytes/Macrophages

“…Another possibility is that TNFα might be expressed and released at basal levels, without the expected potential for inflammation. This assumption is consistent with the statement that a single cytokine has many different effects, not only on different cell types, but even on the same cell type (1). Furthermore, TNFα is not always related to deleterious phenomena around implants.…”

“…These cells are considered to be key regulators in both the initiation and the resolution of inflammatory responses (1), releasing a large array of products into the extracellular environment, including intermediate reactive oxygen and nitrogen species (3), chemokines (1,4,5), cytokines (5,6), and growth factors (7).…”

“…The mediators released by monocyte/macrophage cells can be divided into two major categories: pro-inflammatory, such as interleukin-1 beta (IL1β) (1,2,4,5), tumor necrosis factor alpha (TNFα) (1,(4)(5)(6), and IL6 (1-2,4,5); and antiinflammatory or modulatory, such as IL10 (4)(5)(6)8) and transforming growth factor-beta (TGFβ) (9). This dichotomy established the concept that monocytes/macrophages develop into two major functional types: M1 (classically activated) and M2 (alternatively activated) (10)(11)(12).…”

“…Taking into account that the cytokine profile released by monocytes/macrophages around dental implants is modulated by the surface characteristics of the implant (1,6), it is possible to postulate that the properties of the implant material can influence both cell activity (14,15) and phenotypes (12,13). In other words, the differential wound healing responses elicited by the different biomaterials might be due to the different macrophage functional profiles induced by the materials' surfaces (12).…”

Acid and alkali etching of grit blasted zirconia: Impact on adhesion and osteogenic differentiation of MG63 cells in vitro

“…Future in vitro studies should therefore include a larger spectrum of biofunctionality assays with osteogenic cells. Moreover, research on the impact of surface modifications on the formation of blood clots 24) and aspects of macrophage activity 25) might provide greater insight into the biofunctionality of the biomaterial we have used in the present study.…”