Type I collagen production by osteoblast-like cells cultured in contact with different bioactive glasses

Bioactive glasses are silica-based, surface-active bone substitutes that have shown good biocompatibility both in bone and in soft tissue and are used in oral and maxillofacial bone augmentation. Previous in vitro studies showing that bioactive glasses support the growth and maturation of rat osteoblast-like cells and promote the expression and maintenance of the osteoblastic phenotype have suggested that there is both a solution-mediated and a surface-controlled effect on cell activity. In this study, we investigated the behavior of human primary osteoblast-like cells cultured in contact with three different bioactive glasses and compared them with amorphous silica (SiO2) used in the form of granules. The specific activity of alkaline phosphatase determined biochemically was significantly higher at 2 and 4 days on the bioactive glass with 46.1 mol % silica content (45S5 Bioglass®) cultures than in the control cultures and in the bioactive gel-glass cultures, which had 60 mol % (58S) and 80 mol % (77S) silica content. Osteoblasts synthesize collagen type I, which is subsequently mineralized. Immunoblot and biochemical studies showed increased collagen release from osteoblast-like cells cultured in contact with bioactive glasses over that of controls. Among the three bioactive glasses, 45S5 is the highest inducer of osteoblast-like cell collagen release; moreover, mRNA for type I collagen was stimulated approximately three- to fivefold after 45S5 treatment. 77S bioactive glass similarly increased type I collagen synthesis even though alkaline phosphatase was not higher. These results suggest that 45S5 Bioglass® not only induces osteogenic differentiation of human primary osteoblast-like cells, but can also increase collagen synthesis and release. The newly formulated bioactive gel-glass 77S seems to have potential applications for tissue engineering, inducing increased collagen synthesis.