Comparison of osteoblast responses to hydroxyapatite and hydroxyapatite/soluble calcium phosphate composites

Hydroxyapatite/soluble calcium phosphate composites (HAp/SCaP) are novel HAp-based materials with enhanced solubility that have been developed by annealing HAp in a vacuum. This study compared the effects of HAp and HAp/SCaP on osteoblast proliferation, differentiation, and mineralization using an MC3T3-E1 cell culture system. MC3T3-E1 cells were cultured on HAp or HAp/SCaP, and the number of attached cells and their morphology were examined. The influence of the extract from HAp/SCaP on osteoblast differentiation was determined by the measurement of alkaline phosphatase activity and reverse transcriptase-polymerase chain reaction analysis of the expression of osteoblastic markers. In addition, mineralization was evaluated by the staining of calcium deposits with Alizarin red. Attachment of a greater number of cells exhibiting no degeneration in their morphology was observed on HAp/SCaP compared with HAp after incubation for 7 days or more. Culturing cells with the extract from HAp/SCaP resulted in promotion of alkaline phosphatase activity, the expression of type I collagen, and bone-like tissue formation. The results of the present study indicate that HAp/SCaP shows greater ability in osteogenesis than HAp by increasing collagen synthesis and calcification of the extracellular matrix.