Osteoclast and osteoblast activities on carbonate apatite plates in cell cultures

Previous studies have demonstrated that carbonate apatite (CA) is superior to hydroxyapatite (HA) and β-tricalciumphosphate (β-TCP) with regard to osteoclastic resorption, but evidence on osteoclast and osteoblast response remains controversial. In the present study, the expression of bone related mRNA is examined on CA, HA, β-TCP, and titanium plates. ICR mouse osteoblast cells are cocultured with ICR mouse bone marrow cells. Crude osteoclast-like cell-rich suspensions are then seeded onto plates and cultured for 48 h. Total RNA is extracted and mRNA expression is examined by real-time RT-PCR. Amounts of vacuolar-type ATPase, cathepsin K, and TRAP mRNA are significantly greater on CA than on the other plates. The amount of osteoprotegerin mRNA is significantly greater on CA than on the other plates. RANKL mRNA expression, which is generally regarded as an osteoblast maker, varies with material, but shows no significant differences between CA and the other plates. The formation and activity of osteoclasts is greater with CA than with the other plates. Thus, CA is superior to β-TCP as a bioresorbable bone substitute for tissue engineering.