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

• Published in: Calcified tissue international Vol. 87; no. 6; pp. 513 - 524
• Main Authors: Wiens, Matthias, Wang, Xiaohong, Schloßmacher, Ute, Lieberwirth, Ingo, Glasser, Gunnar, Ushijima, Hiroshi, Schröder, Heinz C., Müller, Werner E. G.
• Format: Journal Article
• Language: English
• Published: New York Springer-Verlag 01.12.2010; Springer Nature B.V
• Subjects: Biochemistry; Biomedical and Life Sciences; Bone Morphogenetic Protein 2 - genetics; Bone Morphogenetic Protein 2 - metabolism; Cell Biology; Cell Differentiation; Cell Line; Cell Proliferation; Durapatite - metabolism; Endocrinology; Enzymes; Humans; Life Sciences; Orthopedics; Osteoblasts - drug effects; Osteoblasts - metabolism; Osteogenesis; Polymers; Silica; Silicon Dioxide - metabolism; Silicon Dioxide - pharmacology; Substrates; Bone morphogenetic protein-2; Osteogenic index; Biosilica; Hydroxyapatite; SaOS-2 cell; Nodule
• ISSN: 0171-967X; 1432-0827
• DOI: 10.1007/s00223-010-9408-6

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.