AbstractThe aim of this study was to investigate the in vitro effect of Silicon, in the soluble form of sodium orthosilicate, combined and not with the concentrated growth factors (CGF), a platelet‐rich preparation, on three different human cell lines of fibroblasts (NHDF), endothelial cells (HUVEC), and osteoblasts (HOBs). Each cell type was treated with sodium orthosilicate at the final concentration of 0.5 mM and 1 mM, CGF, and sodium orthosilicate combined with CGF, for 72 h. At the end of the experimental period, the in vitro effect on cell growth, proliferation, and metabolic activity was evaluated by performing a simple cell count, using an automated cell counter and by evaluating the expression of the intracellular proliferation marker Ki‐67, using Fluorescence‐activated cell sorting (FACS) analysis. Moreover, the expression of other cell markers and active molecules, such as Collagen type I, Osteopontin, Vascular Endothelial Growth Factor, and endothelial Nitric Oxide Synthase, was evaluated, through immunohistochemistry. Results obtained showed that the combined use of CGF and sodium orthosilicate stimulates cell growth, proliferation, and metabolic activity, suggesting that this treatment could be effective in tissue regeneration.