The effects of silicate ions on human osteoblast adhesion, proliferation, and differentiation

Silicon has been shown to have important effects on skeletal development and repair, and soluble silicate ions have been found to stimulate the expression of type-I collagen in osteoblast-like cell cultures. Furthermore, silicon has been incorporated into the hydroxyapatite lattice and enhanced metabolic activity of human osteosarcoma cells was observed when cells were cultured on this material. In vivo assessments have demonstrated enhanced bioactivity of silicon-substituted hydroxyapatite (Si-HA) over pure HA. However, detailed mechanisms for the stimulative effects of Si-HA have not been described. In this study, we found that silicon substitution into hydroxyapatite affects the adhesion of human osteoblast-like cells (HOBs) in culture, with 0.8 wt % silicon substitution being optimal. In addition, metabolic activity and proliferation of HOBs were increased by supplementation of the growth medium with 30 microM silicon. It was determined that this response may depend on the proportion of cells at different stages of differentiation within the cultures.