EFFECT OF TITANIUM SURFACE-ROUGHNESS ON PROLIFERATION, DIFFERENTIATION, AND PROTEIN-SYNTHESIS OF HUMAN OSTEOBLAST-LIKE CELLS (MG63)

The effect of surface roughness on osteoblast proliferation, different iation, and protein synthesis was examined. Human osteoblast-like cell s (MG63) were cultured on titanium (Ti) disks that had been prepared b y one of five different treatment regimens. All disks were pretreated with hydrofluoric acid-nitric acid and washed (PT). PT disks were also : washed, and then electropolished (EP); fine sandblasted, etched with HCl and H2SO4, and washed (FA); coarse sandblasted, etched with HCl a nd H2SO4, and washed (CA); or Ti plasma-sprayed (TPS). Standard tissue culture plastic was used as a control. Surface topography and profile were evaluated by brightfield and darkfield microscopy, cold field em ission scanning electron microscopy, and laser confocal microscopy, wh ile chemical composition was mapped using energy dispersion X-ray anal ysis and elemental distribution determined using Auger electron spectr oscopy. The effect of surface roughness on the cells was evaluated by measuring cell number, [H-3]thymidine incorporation into DNA, alkaline phosphatase specific activity, [H-3]uridine incorporation into RNA, [ H-3]proline incorporation into collagenase digestible protein (CDP) an d noncollagenase-digestible protein (NCP), and [S-35]sulfate incorpora tion into proteoglycan. Based on surface analysis, the five different Ti surfaces were ranked in order of smoothest to roughest: EP, PT, FA, CA, and TPS. A TiO2 layer was found on all surfaces that ranged in th ickness from 100 Angstrom in the smoothest group to 300 Angstrom in th e roughest. When compared to confluent cultures of cells on plastic, t he number of cells was reduced on the TPS surfaces and increased on th e EP surfaces, while the number of cells on the other surfaces was equ ivalent to plastic. [H-3]Thymidine incorporation was inversely related to surface roughness. Alkaline phosphatase specific activity in isola ted cells was found to decrease with increasing surface roughness, exc ept for those cells cultured on CA. In contrast, enzyme activity in th e cell layer was only decreased in cultures grown on FA- and TPS-treat ed surfaces. A direct correlation between surface roughness and RNA an d CDP production was found. Surface roughness had no apparent effect o n NCP production. Proteoglycan synthesis by the cells was inhibited on all the surfaces studied, with the largest inhibition observed in the CA and EP groups. These results demonstrate that surface roughness al ters osteoblast proliferation, differentiation, and matrix production in vitro. The results also suggest that implant surface roughness may play a role in determining phenotypic expression of cells in vivo. (C) 1995 John Wiley & Sons, Inc.