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

Abstract

This study tested the hypothesis that bioactive coating glass (SiO(2)-CaO-P(2)O(5)-MgO-K(2)O-Na(2)O system), used for implant coatings, enhanced the induction of collagen type 1 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 1 synthesis as observed in both gene expression results (day 1, Col1alpha1, 45S5 GCM+AA: 3x control+AA; 6P53-b GCM+AA: 4x control+AA; day 5, Col1alpha2, 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.

Combinatorial effect of Si4+, Ca2+, and Mg2+ released from bioactive glasses on osteoblast osteocalcin expression and biomineralization

“…OCN binds extracellular matrix calcium to the developing bone matrix [1], and high serum levels are correlated with high bone mineral density [2,3]. An in vitro model showed OCN expression occurred within the ECM after 18 days [4], while endogenous expression occurred as early as 3 days after osteogenic induction [5]. Preceding or concurrent to OCN expression, other transcription factors, growth factors, and signaling proteins are expressed during osteoblast progenitor differentiation into the mineralizing phenotype.…”

Mechanical heterogeneity of dentin at different length scales as determined by AFM phase contrast

“…The slight decrease in cell number between days 3 and 5 was not significant and was attributed to the limitation of the assay reagent because of contact inhibition in confluent cultures. 1 Thus, cell density increased significantly with time but did not change with treatment.…”

“…Despite these and other studies that showed enhanced osteogenic effects by bioactive glass ionic products, no study has shown that these ions are involved in the combinatorial control of osteoblast gene expression. The combinatorial principle involves control over cellular gene expression by gene regulatory proteins 1 Xynos et al, 3 Table). Besides individual ion effects, the combined ion effect could also influence cellular gene expression through a combined ion ratio.…”

Potential Involvement of Twist2 and Erk in the Regulation of Osteoblastogenesis by HB-EGF-EGFR Signaling

“…Taken together, constitutive expression of Opn would be due to the differentiation stage which we observed, and the difference of transcriptional factor would be a reason that the expression of Opn was not affected by HB-EGF. ColI is also well known for the osteoblastic marker, but the expression in MC3T3-E1 cells was not changed in osteogenic media for 10 days (Varanasi et al, 2009), suggesting that ColI is not suitable as a marker gene in MC3T3-E1 cells at least for 10 days after differentiation stimulation.…”