Enhanced osteocalcin expression by osteoblast-like cells (MC3T3-E1) exposed to bioactive coating glass (SiO2-CaO-P2O5-MgO-K2O-Na2O system) ions

This study tested the hypothesis that bioactive coating glass (SiO2-CaO-P2O5-MgO-K2O-Na2O system), used for implant coatings, enhanced the induction of collagen type I synthesis and in turn enhanced the expression of downstream markers alkaline phosphatase, Runx2 and osteocalcin during osteoblast differentiation. The ions from experimental bioactive glass (6P53-b) and commercial Bioglass (TM) (45S5) were added to osteoblast-like MC3T3-E1 subclone 4 cultures as a supplemented ion extract (glass conditioned medium (GCM)). Ion extracts contained significantly higher concentrations of Si and Ca (Si, 47.9 +/- 10.4 ppm; Ca, 69.8 +/- 14.0 for 45S5; Si, 33.4 +/- 3.8 ppm; Ca, 57.1 +/- 2.8 ppm for 6P53-b) compared with the control extract (Si < 0. 1 ppm, Ca 49.0 ppm in alpha-MEM) (ANOVA, p < 0.05). Cell proliferation rate was enhanced (1.5x control) within the first 3 days after adding 45S5 and 6P53-b GCM. MC3T3-E1 subclone 4 cultures were then studied for their response to the addition of test media (GCM and control medium along with ascorbic acid (AA; 50 ppm)). Each GCM + AA treatment enhanced collagen type I synthesis as observed in both gene expression results (day 1, Coll alpha 1, 45S5 GCM + AA: 3x control + AA; 6P53-b GCM + AA: 4x control + AA; day 5, Coll alpha 2, 45S5 GCM + AA: 3.15x control + AA; 6P53-b GCM + AA: 2.35x control + AA) and in histological studies (Picrosirius stain) throughout the time course of early differentiation. Continued addition of each GCM and AA treatment led to enhanced expression of alkaline phosphatase (1.4x control + AA after 5 days, 2x control + AA after 10 days), Runx2 (2x control + AA after 7 days) and osteocalcin gene (day 3, 45S5 GCM + AA: 14x control + AA; day 5, 6P53-b GCM + AA: 19x control + AA) and protein expression (40x-70x control + AA after 6 days). These results indicated the enhanced effect of bioactive glass ions on key osteogenic markers important for the bone healing process. (C) 2009 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.