Osteogenic Potential of Biosilica on Human Osteoblast-Like (SaOS-2) Cells

• DOI: 10.1007/s00223-010-9408-6
• Publication Date: 2010-08-19T06:53:35Z
• Authors: Matthias Wiens; Xiaohong Wang; Ute Schloßmacher; Ingo Lieberwirth; Gunnar Glasser; Hiroshi Ushijima; Heinz C. Schröder; Werner E. G. Müller
• Keywords: 0303 health sciences; 03 medical and health sciences; Durapatite; Osteoblasts; Osteogenesis; Bone Morphogenetic Protein 2; Humans; Cell Differentiation; Silicon Dioxide; Cell Line; Cell Proliferation

Biosilica is a natural polymer, synthesized by the poriferan enzyme silicatein from monomeric silicate substrates. Biosilica stimulates mineralizing activity and gene expression of SaOS-2 cells. To study its effect on the formation of hydroxyapatite (HA), SaOS-2 cells were grown on different silicatein/biosilica-modified substrates (bone slices, Ca-P-coated coverslips, glass coverslips). Growth on these substrates induced the formation of HA nodules, organized in longitudinal arrays or spherical spots. Nodules of sizes above 1 μm were composed of irregularly arranged HA prism-like nanorods, formed by aggregates of three to eight SaOS-2 cells. Moreover, growth on silicatein/biosilica-modified substrates elicited increased [(3)H]dT incorporation into DNA, indicative of enhanced cell proliferation. Consequently, an in vitro-based bioassay was established to determine the ratio between [(3)H]dT incorporation and HA formation. This ratio was significantly higher for cells that grew on silicatein/biosilica-modified substrates than for cells on Ca-P-coated coverslips or plain glass slips. Hence, we propose that this ratio of in vitro-determined parameters reflects the osteogenic effect of different substrates on bone-forming cells. Finally, qRT-PCR analyses demonstrated that growth of SaOS-2 cells on a silicatein/biosilica matrix upregulated BMP2 (bone morphogenetic protein 2, inducer of bone formation) expression. In contrast, TRAP (tartrate-resistant acid phosphatase, modulator of bone resorption) expression remained unaffected. We conclude that biosilica shows pronounced osteogenicity in vitro, qualifying this material for studies of bone replacement also in vivo.