The effect of strontium citrate on primary human alveolar bone cells
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Background . Strontium is a mineral closely similar to calcium and found in trace amounts in various foods and in drinking water. Among 26 strontium salts strontium ranelate is commonly given in pharmacological dosages, which seems to both enhance bone formation and slow bone resorption. This original mechanism of action holds promise for the treatment of osteoporosis, most notably in its postmenopausal form. The significance of the strontium use over the bisphosphonates is that no cases of osteonecrosis have been reported with any form of strontium. Strontium citrate is considered a natural form compared to other forms of strontium; which explains why most large scale research efforts done by the drug industry is directed to formulated types. We hypothesized that strontium citrate has proliferative and osteogenic effects on osteoblasts obtained from alveolar bone, similar or comparable to the effects of strontium ranelate on human osteoblasts. The aim of this study was to determine if strontium citrate may enhance or inhibit the proliferation and differentiation of primary human osteoblasts derived from alveolar bone cells and to compare the effect of strontium citrate alone and with indomethacin, an inhibitor of prostaglandin synthesis. Methods . Human alveolar bone cells were obtained during routine oral surgical procedure from healthy adult subjects. Following treatment with strontium citrate at 1,0.5,0.25,0.125 and 0.0625 mM, and a combination of indomethacin (10 -8 mM) at different time periods (24 and 48) hours, cells were examined for differentiation with the alkaline phosphate assay. The effect of strontium citrate on proliferation was assessed with the 3H-thymidine assay. The results were analyzed by (ANOVA) followed by Tukey HSD post hoc comparison analysis. Results . Strontium citrate increased alkaline phosphatase activity at 48 hours. Adding indomethacin did not affect the differentiation results. The proliferation rate was enhanced by strontium citrate at 48 hours and at 24 hours only in combination with indomethacin. Combining indomethacin significantly increased the proliferation rate at 24 and 48 hours compared to strontium citrate alone. Conclusion . Strontium citrate significantly increased the differentiation and proliferation of primary human osteoblasts derived from alveolar bone. There was a synergy effect when strontium citrate was combined with indomethacin in terms of proliferation rate, assuming strontium citrate induced proliferation was more marked when prostaglandin production by osteoblasts was inhibited.