Activation of phospholipase D1 by surface roughness of titanium in MG63 osteoblast-like cell

Although it is recognized that the surface roughness of titanium (Ti) promotes the osteogenic differentiation, the related mechanisms and factors remain elusive. The purpose of this study was to explore the potential correlation among phospholipase D (PLD) activity, Ti surface roughness and subsequent osteoblast differentiation. The machined Ti disks were sandblasted with aluminum oxide particles to produce surfaces of varying roughness (n=160). Normal or transfected MG63cells with PLD genes were cultured on roughened Ti specimens and assayed for PLD, alkaline phosphatase (ALP) and osteocalcin. The statistical significance was evaluated by analysis of variance. The activity, mRNA and protein levels of PLD significantly increased in MG63 cells with a roughness-dependent pattern (P<0.05). The ALP activity and osteocalcin production, promoted by Ti surface roughness, were enhanced by the PLD activator and inhibited by the PLD blocker. It was also found that the PLD1 isoform responds to Ti surface roughness and regulates selectively the ALP activity. These observations strongly suggest that PLD1 mediates the cellular signaling of and modulates osteoblast differentiation induced by Ti surface roughness in MG63 osteoblast-like cell.