異なった細胞の状態が骨芽細胞のリン酸カルシウム粒子に対する反応に影響する

抄録

Calcium phosphates are the most popular biomaterials for implantation into bone. However, it is still unclear how calcium phosphates affect the activities of osteoblasts. In this study, we investigated the effects of calcium phosphates that have different solubilities on osteoblastic proliferation and differentiation using osteoblastic cell-line MC3T3-E1. In addition, we investigated how the cell situation influenced osteoblastic response to calcium phosphates.
Particles (diameter 53-106 μm) of tetracalcium phosphate (TTCP), α-tricalcium phosphate (α-TCP), β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) were used for this experiment. All kinds of calcium phosphate particles inhibited osteoblastic proliferation. Though the calcium and phosphorus content in the medium was influenced by calcium phosphate particles, culture medium incubated with calcium phosphates (experimental medium) did not influence osteoblastic proliferation.
The effects of calcium phosphate particles on osteoblastic differentiation were investigated by alkaline phosphatase (ALP) activity and reverse transcription polymerase chain reaction (RT-PCR) using dispersed cells or confluent cells. When the calcium phosphate particles were added to confluent cells, ALP activity was not changed, and there was no change of mRNA levels of osteoblast-related genes. However, when the calcium phosphate particles were added to dispersed cells, ALP activity was enhanced by TTCP and α-TCP. The mRNA level of osteopontin (OPN) was enhanced especially by TTCP and α-TCP. The mRNA level of type I collagen (COL) was enhanced especially by α-TCP, and β-TCP. On the other hand, mRNA levels of osteocalcin (OCN), bone sialoprotein (BSP) were not affected by calcium phosphate particles.
These results indicate that the inhibitory effects of calcium phosphate particles on osteoblastic proliferation are not due to the changes of calcium and phosphate ions in the medium but are due to the surface property of the materials. The effects of the calcium phosphate particles on osteoblastic differentiation may be changed by the cell situations such as confluent cells or dispersed cells.