Particulate beta-tricalcium phosphate and hydroxyapatite doped with silver promote in vitro osteoblast differentiation in MC3T3-E1 cells.

BACKGROUND: Calcium phosphates including ß-tricalcium phosphate (ß-TCP) and hydroxyapatite (HAp) have been widely used for bone regeneration application because of their high osteoconductive activities. In addition, various kinds of inorganic ions enhance differentiation, proliferation, and mineralization of osteoblasts. However, information about the effects of silver-doped ß-TCP [ß-TCP (Ag)] and HAp [HAp (Ag)] particles on osteogenic differentiation is not available yet. OBJECTIVE: We focused on the impact of ß-TCP (Ag) and HAp (Ag) particles on the osteogenic differentiation of MC3T3-E1 osteoblast precursor cells. METHODS: MC3T3-E1 osteoblast precursor cells were pre-treated by ß-TCP (Ag) or HAp (Ag). And then the medium was changed to differentiation medium. Subsequently, osteoblast differentiation-related markers were determined. RESULTS: We found that treatment with ß-TCP (Ag) or HAp (Ag) particles increased alkaline phosphatase activity in MC3T3-E1 cells. Expression of osteoblast differentiation-related genes also increased after treatment with ß-TCP (Ag) or HAp (Ag) particles, a response thought to be regulated by zinc finger-containing transcription factor osterix. The ratio of the receptor activator of nuclear factor kappa-B ligand (RANKL) to osteoprotegerin (OPG) was decreased by ß-TCP (Ag) and HAp (Ag) particles. CONCLUSION: Silver doping of ß-TCP and HAp particles is effective for bone regeneration.

In vivo bioresorbability and bone formation ability of sintered highly pure calcium carbonate granules.

Calcium carbonate-based bone substitutes derived from natural coral exoskeleton (aragonite) are resorbed and remodeled faster than calcium phosphate-based substitutes. However, coral species with structures appropriate for use as bone substitutes are very limited. Therefore, it is important to evaluate potential of artificial calcium carbonate ceramics as a bone substitute. In this study, calcium carbonate granules with various porosities and pore sizes were prepared by sintering a highly pure (>99.98%) calcium carbonate powder (calcite), and their resorption properties and bone formation abilities were examined in vivo for the first time. The sintered calcium carbonate was resorbed faster than ß-tricalcium phosphate, which has a similar structure. However, sintered calcium carbonate did not promote new bone formation during long-term implantation. Furthermore, both resorption and new bone formation were affected by the pore structure. The optimal structures of the artificially sintered calcium carbonate bone substitute were also discussed.

Effect of silicate incorporation on in vivo responses of α-tricalcium phosphate ceramics.

In addition to calcium phosphate-based ceramics, glass-based materials have been utilized as bone substitutes, and silicate in these materials has been suggested to contribute to their ability to stimulate bone repair. In this study, a silicate-containing α-tricalcium phosphate (α-TCP) ceramic was prepared using a wet chemical process. Porous granules composed of silicate-containing α-TCP, for which the starting composition had a molar ratio of 0.05 for Si/(P + Si), and silicate-free α-TCP were prepared and evaluated in vivo. When implanted into bone defects that were created in rat femurs, α-TCP ceramics either with or without silicate were biodegraded, generating a hybrid tissue composed of residual ceramic granules and newly formed bone, which had a tissue architecture similar to physiological trabecular structures, and aided regeneration of the bone defects. Supplementation with silicate significantly promoted osteogenesis and delayed biodegradation of α-TCP. These results suggest that silicate-containing α-TCP is advantageous for initial skeletal fixation and wound regeneration in bone repair.