Mechanism of Monosodium Titanate Inhibition of Cell Growth in Vitro

Objectives: The ion exchanger monosodium titanate (MST) has been proposed to therapeutically deliver calcium ions in dental situations that require calcium. However, previous results suggest that MST limits cell growth in vitro by mechanisms that remain obscure. It is critical to understand these mechanisms for any successful therapeutic use of MST. The current study tested the hypothesis that MST limits cell growth in vitro by binding to culture polystyrene, reducing attachments sites available to cells, thereby limiting cell culture growth.
Methods: MST was added to culture wells (8 concentrations between 0 and 200 mg/L) either 24 h after addition of L929 fibroblasts or prior to cell addition. Cell cultures (n = 8/condition) were left in contact with the MST for 72 h, after which cell growth was assessed using Cell TiterBlue®. Control groups received no MST; statistical differences were detected using ANOVA with Tukey post-hoc tests (α = 0.05).
Results: When MST was added after plating of the cells, cell growth was inhibited in a dose-dependent fashion to a maximum of 40% (p < 0.05 compared to no-MST controls). Yet when MST was added prior to the cells, the maximal inhibition of growth was 80% vs. controls. (p < 0.05).
Conclusions: The addition of MST before cells significantly decreased growth in the cultures (relative to conditions where cells were established first). Microscopic inspection of the culture wells revealed more attachment of the MST to the culture polystyrene than when cells were added first. These results and observations are consistent with our hypothesis that the MST attaches the polystyrene and reduces the ability of cells to attach and proliferate. Further testing with other cell types and additional cell densities is in progress.