Silica-based bioactive glasses modulate expression of bone morphogenetic protein-2 mRNA in Saos-2 osteoblasts in vitro.
A chemical exchange of the silica gel layer forming on the surface of bioactive glasses is thought to be the principal reaction for bone-bioactive glass bonding. The contribution of biological molecules on cell-bioactive glass interaction is largely unknown. To further analyze the mechanisms involved in efficient bone bonding to bioactive glass, Saos-2 osteoblastic cells with proven osteogenic phenotype were cultured for 4, 7 and 14 days on two bioactive glasses with different Si contents. Culture plates and dishes made of bioactive (BAG, 53 % SiO2), biocompatible (BCG, 58% SiO2) and control (GO) glasses were extensively conditioned with phosphate buffer and DMEM medium before seeding the cells. Northern hybridization was used for analysis of mRNA levels of collagen type I (Col-I), alkaline phosphatase (ALP) and bone morphogenetic protein-2 (BMP-2). A significant increase was observed in Col-I mRNA levels in cells grown on the two bioactive glasses when compared with those grown on controls at 4 and 7 days (p < 0.04). The mRNA level for ALP in the cultures of bioactive glasses-made plates and dishes was also increased over control at 7 days (p < 0.02) and remained this way between BAG and G0 at 14 days. Striking differences in BMP-2 mRNA levels existed between BAG and G0 plates and dishes at 7 days (p < 0.05). BMP-2 mRNA level in BAG group was higher than in BCG group at 4, 7 and 14 days, but without statistical significance. Saos-2 osteoblastic cells with strong ALP staining were mostly seen on BAG plates under a light microscope. In confocal microscopy, a bright FITC-stained F-actin ring was present in the cytoplasm of cells grown on BAG dish, demonstrating an active functional status. Stimulation of the expression of BMP-2 and other bone mRNAs by bioactive glasses in osteoblastic cells suggests biological involvement of bone related growth factors, peptides and cytokines in bone-bioactive glass bonding.
Gao
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Department of Medical Biochemistry and Molecular Biology, University of Turku, Finland. tgao@ualberta.ca
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Ylänen
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Vuorio
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D000469:Alkaline Phosphatase / Q000235:genetics; D001672:Biocompatible Materials / Q000494:pharmacology*; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000235:genetics*; D003094:Collagen / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects*; D005898:Glass; D006801:Humans; D007700:Kinetics; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D012516:Osteosarcoma; D012333:RNA, Messenger / Q000235:genetics; D012822:Silicon Dioxide / Q000494:pharmacology*; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects*; D016212:Transforming Growth Factor beta; D014407:Tumor Cells, Cultured
C525718:BMP2 protein, human; D001672:Biocompatible Materials; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D012822:Silicon Dioxide; D003094:Collagen; D000469:Alkaline Phosphatase