Bone morphogenetic protein-2 (BMP-2), is a potential factor to enhance osseointegration
of dental implants. However, the appropriate cellular system to investigate the osteogenic
effect of BMP-2 in vitro in a standardized manner still needs to be defined. The aim
of this study was to examine the effect of BMP-2 on the cell proliferation and osteogenic
differentiation of human osteogenic progenitors of various origins: dental pulp stem
cells (DPSC), human osteosarcoma cell line (Saos-2) and human embryonic palatal mesenchymal
cell line (HEPM). For induction of osteogenic differentiation, cell culture medium
was supplemented with BMP-2 homodimer alone or in combination with conventionally
used differentiation inducing agents. Differentiation was monitored for 6-18 days.
To assess differentiation, proliferation rate, alkaline phosphatase activity, calcium
deposition and the expression level of osteogenic differentiation marker genes (Runx2,
BMP-2) were measured. BMP-2 inhibited cell proliferation in a concentration and time-dependent
manner. In a concentration which caused maximal cell proliferation, BMP-2 did not
induce osteogenic differentiation in any of the tested systems. However, it had a
synergistic effect with the osteoinductive medium in both DPSC and Saos-2, but not
in HEPM cells. We also found that the differentiation process was faster in Saos-2
than in DPSCs. Osteogenic differentiation could not be induced in the osteoblast progenitor
HEPM cells. Our data suggest that in a concentration that inhibits proliferation the
differentiation inducing effect of BMP-2 is evident only in the presence of permissive
osteoinductive components. beta-glycerophosphate, was identified interacting with
BMP-2 in a synergistic manner.
