Effects of metal ions on osteoblast-like cell metabolism and differentiation.

The objective of this study was to evaluate the effects of metal ions, which may be released from orthopedic or dental implants, on osteoblast metabolism and differentiation. ROS 17/2.8 cells were cultured in F-12 medium for 7 days. Then Al+3, Co+2, Cr+3, Ni+2, Ti+4, and V+3 were added at concentrations less than their cytotoxic concentrations. After 3 days, DNA synthesis, succinate dehydrogenase activity, alkaline phosphatase (ALP) activity, and culture calcification were assessed. Northern blots were performed for ALP, osteocalcin (OCN), and osteopontin (OPN) mRNA transcription. The data indicated that Cr+3 and A1+3 had few inhibitory effects on ROS cell metabolism below their cytotoxic concentrations, Ni+2, Co+2, Ti+4, and V+3 affected all these parameters of ROS cell metabolism at concentrations below cytotoxic levels. For RNA analysis, A1+3 significantly suppressed the expression of ALP, OCN, and OPN at both cytotoxic and noncytoxic concentrations. Co+2 specifically suppressed ALP expression at cytotoxic concentrations. Cr+3 and Ni+2 inhibited OCN, OPN, and ALP gene expression only at cytotoxic concentrations. For Ti+4 and V+3 ions, gene expression at cytotoxic levels was not significantly affected as compared with the effects at noncytotoxic level. These results show that metal ions may alter osteoblast behavior even at subtoxic concentrations, but do not always affect the expression of all genes similarly.