Osteoclastic cell behaviors affected by the α-tricalcium phosphate based bone cements
Calcium phosphate cements (CPCs) have recently gained great interest as injectable bone substitutes for use in dentistry and orthopedics. α-tricalcium phosphate (α-TCP) is a popularly used precursor powder for CPCs. When mixed with appropriate content of liquid and kept under aqueous conditions, α-TCP dissolves to form a calcium-deficient hydroxyapatite and then hardens to cement. In this study, α-TCP based cement (CP) and its composite cement with chitosan (Ch-CP) were prepared and the osteoclastic responses to the cements and their elution products were evaluated. Preliminary evaluation of the cements revealed that the CP and Ch-CP hardened within ~10 min at an appropriate powder-to-liquid ratio (PL) of 3.0. In addition, CP and Ch-CP were transformed into an apatite phase following immersion in a saline solution. Moreover, the osteoblastic cells were viable on the cements for up to 10 days. Mouse-derived bone marrow cells were isolated and activated with osteoclastic differentiation medium, and the effects of the CP and Ch-CP substrates and their ionic eluants on the osteoclastic activity were investigated. Osteoclastic cells were viable for up to 14 days on both types of cements, maintaining a higher cell growth level than the control culture dish. Multi-nucleated osteoclastic cells that were tartrate-resistant acid phosphatase (TRAP)-positive were clearly observed when cultured on the cement substrates as well as treated with the cement eluants. The TRAP activity was found to be significantly higher in cells influenced by the cement substrates and their eluants with respect to the control culture dish (Ch-CP > CP ≫ control). Overall, the osteoclastic differentiation was highly stimulated by the α-TCP based experimental cements in terms of both the substrate interaction and their elution products.
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