Morphogenetic Activity of Silica and Bio-silica on the Expression of Genes Controlling Biomineralization Using SaOS-2 Cells

Abstract

In a previous study (Schröder et al., J Biomed Mater Res B Appl Biomater 75:387-392, 2005) we demonstrated that human SaOS-2 cells, when cultivated on bio-silica matrices, respond with an increased hydroxyapatite deposition. In the present contribution we investigate if silica-based components (Na-silicate, tetraethyl orthosilicate [TEOS], silica-nanoparticles) (1) change the extent of biomineralization in vitro (SaOS-2 cells) and (2) cause an alteration of the expression of the genes amelogenin, ameloblastin, and enamelin, which are characteristic for an early stage of osteogenesis. We demonstrate that the viability of SaOS-2 cells was not affected by the silica-based components. If Na-silicate or TEOS was added together with ss-glycerophosphate, an organic phosphate donor, a significant increase in biomineralization was measured. Finally, expression levels of the amelogenin, ameloblastin, and enamelin genes were determined in SaOS-2 cells during exposure to the silica-based components. After exposure for 2 days, expression levels of amelogenin and enamelin strongly increased in response to the silica-based components, while no significant change was seen for ameloblastin. In contrast, exposure of SaOS-2 cells to ss-glycerophosphate resulted in increased expression of all three genes. We conclude that the levels of the structural molecules of the enamel matrix, amelogenin and enamelin, increase in the presence of silica-based components and substantially contribute to the extent of hydroxyapatite crystallite formation. These results demonstrate that silica-based components augment hydroxyapatite deposition in vitro and suggest that enzymatically synthesized bio-silica (via silicatein) might be a promising route for tooth reconstruction in vivo.

Inorganic polymeric phosphate/polyphosphate as an inducer of alkaline phosphatase and a modulator of intracellular Ca2+ level in osteoblasts (SaOS-2 cells) in vitro

“…Known since the seventies is the fact that silica is one inorganic component that is required during the early steps in bone formation [61,62]. However, recently the silicate metabolism has been investigated more intensively both in vivo [63] and in vitro [38,45,48]. The recent finding that biosilica, the polymer of silica, acts in vitro as an inducer of OPG while leaving the steady-state expression of RANKL unaffected suggests that the polymer is a new factor inhibiting osteoclast maturation [38] (see the scheme in Fig.…”

“…SaOS-2 cells (human osteogenic sarcoma cells [43]) were cultured in McCoy's medium (containing 1 mM CaCl 2 ), with 5% heat-inactivated fetal calf serum (FCS), 2 mM L-glutamine and gentamicin (50 lg ml -1 ) in 6-well plates (surface area 9.46 cm 2 ; Orange Scientifique, Braine-l'Alleud; Belgium) at a density of 5 Â 10 3 cells cm -2 in a humidified incubator at 37°C and 5% CO 2 , as described previously [44,45].…”

Ameloblastin Regulates Osteogenic Differentiation by Inhibiting Src Kinase via Cross Talk between Integrin β1 and CD63

“…AMBN is present in the secretory stage of enamel formation, as demonstrated by immunostaining of ameloblastin (21). It has recently been revealed that AMBN is also expressed in osteoblasts during craniofacial skeletal development and in an osteosarcoma cell line, SaOS-2, cultivated on biosilica matrices (19,25). However, the function of AMBN in osteoblasts is unknown.…”

Effect of amorphous silica nanoparticles on in vitro RANKL-induced osteoclast differentiation in murine macrophages

“…They also support the safety of nanosilicas that are used in the production of highly functional materials for oral care fields [1,20]. We believe that applications of nanosilica will extend to these new fields in the near future following further careful safety study.…”