Effects Of Brushite Coating Extract With Strontium On Osteoblast-related Factors Expressed In MC3T3-E1Cells

Objectives Brushite is a kind of calcium phosphate cement (CPC), having goodbiocompatibility and faster rate of degradation under physiological conditions. Strontium(Sr) with low dose has advantages including, but not only, promoting bone formation andinhibiting bone resorption. In this thesis, a method of electrochemical depositionmodification was used to form brushite coating surface on titanium. Use extraction methodto prepare extracts containing different concentrations of strontium or not. In vitrosynergistic effect of Sr and brushite on osteoblasts was investigated to provide a theoreticalbasis for the optimization of strontium concentration.Methods Brushite coated titanium sheet by using electrochemical deposition wasprepared, then a series extractions contained different concentration of Sr were preparedusing culture medium. Then the MC3T3-E1cells were cultured in the extract. Severalkinds of experiments were performed to detect cell viability, Alkaline phosphatase (ALP)activity and Real-time Polymerase Chain Reaction (RT-PCR) were used to detectexpression of cytokines that include basic fibroblast growth factor (bFGF) and vascularendothelial growth factor (VEGF).Results The results showed brushite extract could affect MC3T3-E1cells. The relativecell viability of Br+Sr_M group and Br+Sr_H group are significantly higher than Brushitegroup (99.97±7.53vs.58.25±2.76，P<0.05;85.96±7.37vs.58.25±2.76，P<0.05). TheALP activity of Br+Sr_M group is significantly higher than Br+Sr_L group and Br+Sr_Hgroup (99.97±7.53vs.63.56±3.69， P<0.05；99.97±7.53vs.85.96±7.37， P<0.05).During3days incubation with brushite extract, the expression level of bFGF of Br+Sr_Lgroup, Br+Sr_M group and Br+Sr_H group, compared to Brushite group, are upregulatedsignificantly(8.54±0.49vs.0.87±0.02， P<0.05;12.05±0.20vs.0.87±0.02， P<0.05;4.88±0.14vs.0.87±0.02，P<0.05), but Br+Sr_L group is lower than Br+Sr_M group(8.54±0.49vs.12.05±0.20， P<0.05) and higher than Br+Sr_H group (8.54±0.49vs.4.88±0.14，P<0.05). During5days incubation with brushite extract, the expression levelof bFGF of Br+Sr_M group and Br+Sr_H group are upregulated than Brushite group151.72±6.33vs.14.11±1.05， P<0.05;200.74±14.43vs.14.11±1.05， P<0.05), andBr+Sr_H group is higher than Br+Sr_M group. The expression level of VEGF of Br+Sr_L group, Br+Sr_M group and Br+Sr_H group, compared to Brushite group, are upregulatedsignificantly (4.01±0.15vs.0.97±0.09， P<0.05;22.44±1.34vs.0.97±0.09， P<0.05;10.31±1.02vs.0.97±0.09，P<0.05), and Br+Sr_M group is higher than Br+Sr_L groupand Br+Sr_H group (22.44±1.34vs.4.01±0.15，P<0.05;22.44±1.34vs.10.31±1.02，P<0.05). The results indicate that Sr could affect viability and expression of cytokinesrelated to bone formation of MC3T3-E1cell.Conclusions The results showed brushite had good biological activity, and it was a finekind of bioactive material. Incorporate brushite with right amount of strontium, it cansignificantly enhanced the induction of osteoblast to differentiate into bone cells, thus as abiological engineering material, strontium-doped brushite may have broad applicationprospects. On the other hand, the results demonstrated that the effect of strontium onosteoblast involves enhancenment of ALP and upregulation of bFGF and VEGF mRNA.Thus, the results of the project may be referenced by developing bioengineering materials,as cytokines involved could become protential targets.