Osteoblast response to titanium regulates transcriptional activity of Runx2 through MAPK pathway.

Bone formation around an implant surface is indispensable for osseointegration of dental implants. Transcriptional factor Runx2 is essential for osteoblast differentiation and bone formation. However, little is known about the involvement of Runx2 in osseointegration. The purpose of this study was to investigate molecular interactions between Runx2 and implant titanium materials at the transcriptional level. Primary osteoblasts isolated from mouse calvaria and C3H10T1/2 cells were cultured on titanium plates or in the presence of titanium particles. Transcriptional activity of Runx2 was measured by reporter assay using osteocalcin gene promoter. We found significant increase (p < 0.05) in Runx2 transcriptional activity in cells cultured on titanium plates compared to plastic plates. Titanium particles also upregulated Runx2 transcriptional activity for over 2-folds compared to control and this effect was abolished by the specific inhibitor for ERK1/2, PD98059. Moreover, treatment with PD98059 clearly suppressed osteoblast mineralization cultured on titanium plates. These data suggest that osteoblast attachment to titanium enhanced Runx2 transcriptional activity and bone formation via MAPK pathway during the osseointegration of dental implants. Copyright 2006 Wiley Periodicals, Inc.