Titanium surface topography alters cell shape and modulates bone morphogenetic protein 2 expression in the J774A.1 macrophage cell line.

Abstract

Macrophage cytokine expression significantly affects wound healing. Macrophage secretion of transforming growth factor beta 1 (TGFbeta1) and bone morphogenetic proteins (BMP) may affect osteogenesis at endosseous implant surfaces. The aim of this investigation was to determine the effect of commercially pure titanium (cpTi) substrate topography on adherent macrophage osteogenic and osteoinductive cytokine expression. J774A.1 murine macrophage cell adhesion was examined by scanning electron microscopy, 0-72 h following plating onto polished, machined, and grit-blasted cpTi surfaces. TGFbeta1 and BMP-2 gene expression by adherent macrophages was determined by the reverse transcription polymerase chain reaction. Macrophage adhesion increased with time on all surfaces and spreading increased with increasing surface roughness (polished < machined < grit-blasted). BMP-2 expression was not evident for cells adherent to polished cpTi at 24 h. In contrast, BMP-2 expression occurred at 24 h in cells adherent to machined and grit-blasted cpTi. BMP-2 expression was evident on all surfaces at 72 h and was greatest in grit-blasted titanium adherent cells. Increasing concentrations of cytochalasin B (0-50 microM) inhibited macrophage spreading and reduced BMP-2 mRNA expression, suggesting a relationship between cell shape and BMP-2 expression. This was further characterized using anti-beta1 and anti-beta3 integrin antibodies. The anti-beta1 integrin antibodies inhibited adherent macrophage BMP-2 mRNA expression. Anti-beta3 integrin antibody treatment only modestly reduced BMP-2 mRNA expression. Endosseous implant surface topography induced changes in macrophage shape that were associated with changes in BMP-2 expression in J774A.1 mouse macrophage cell line. This first demonstration of BMP-2 expression by cpTi adherent macrophages suggests that the macrophage may contribute surface-specific osteoinductive signals during bone formation at implanted alloplastic surfaces.