The effect of strontium incorporation in hydroxyapatite on osteoblasts in vitro

The purpose of this study was to test the effects of a series of strontium-substituted HA (Sr-HA) ceramics (0, 1, 5, and 10 mol% Sr substitution) on osteoblasts, thereby demonstrating whether strontium incorporation with HA would favor osteoblast metabolism. Rat primary osteoblasts were cultured with culture media containing ions released from the Sr-HA ceramics as they dissolved. MTT test, alkaline phosphatase activity, osteoblast transcription factor gene (cbfa1) expression and Alizarin Red staining were conducted at different time-points. There is no significant difference in cell proliferation between groups. However, compared with HA group, Sr-HA groups presented significant enhancement with regard to ALP activity, cbfa1 mRNA expression, and mineralization nodules. Among Sr-HA groups, 5 and 10% groups showed much better performances in ALP activity, cbfa1 mRNA expression, and mineralization nodules than 1% group, however, no significant difference was found between 5 and 10% groups. This study has demonstrated that Sr incorporation in HA ceramic enhanced osteoblastic cell differentiation and mineralization. However, further detailed studies are needed to understand the mechanistic effects of this Sr incorporation on osteoblastic cells and the optimal percentage of calcium should be substituted with strontium in HA.