Bioactive Glass Coatings and Bioglass^TM Corrosion Products Enhance Osteoblast Differentiation

Introduction: Direct bone bonding occurs between implanted bioactive glasses and bone matrix collagen (Hench et al.). Furthermore, it has been hypothesized that a key player in this bonding is the enhanced behavior of osteoblasts in the presence of bioactive glass corrosion products (Foppiano et al.). Objective: To test the hypothesis that bioactive glass coating (for Ti implants) corrosion products enhance the expression of key osteogenic markers during osteoblast differentiation. Methods: The corrosion products of glass specimens (6P53-b (53 wt.% SiO₂), 45S5 (Bioglass^TM, 45 wt. SiO₂)) were produced by soaking (48 h) glass specimens in α-MEM (ion extract, 0.2 μm filtered) and then adding supplements (10% FBS, 1% pen-strep) to make glass conditioned medium (GCM) and compared to control: (supplemented α-MEM). This GCM was added to osteoblast (MC3T3 E1.4) cultures during proliferation and differentiation. Ion concentrations were measured using Inductively Coupled Plasma Mass Spectrometry (ICPMS). Cells were assayed for their levels of expressed alkaline phosphatase and osteocalcin during differentiation, and increasing cell number during proliferation. Collagen type 1 and Runx2 expression was assayed using quantitative PCR. Results: Ion concentrations (Si: 47.9±10.4 ppm, Ca: 69.8±14.0 ppm for 45S5; Si: 33.4±3.8 ppm, Ca: 57.1±2.8 ppm for 6P53-b) were higher in ion extracts compared to controls (Si: < 0.1 ppm, Ca: 49.0 ppm in α-MEM). GCM enhanced MC3T3-E1.4 proliferation rate (1.5x control, within 3d). Both GCM induced increased levels of Runx2 and collagen type 1 after 7d in culture. Overall protein production of osteocalcin was higher over 10d in cells exposed to GCM.. Conclusions: These results indicated the corrosion products from bioactive glasses enhanced osteoblast proliferation and differentiation in vitro. Support: NIH/NIDCR Grants 1K25DE018230-01, R01DE11289, and T32DE07306