Effect of hydroxyapatite sol on cell proliferation and alkaline phosphatase activity of osteoblastic MC3T3-E1 cells

The effect of hydroxyapatite sol (HAm) which is composed of unheating hydroxyapatite microcrystal particle on cell proliferation and alkaline phophatase activity in osteoblastic MC3T3-E1 cells, was examined in the presence or absence of fetal calfe serum (FCS) in the medium. In the absence of FCS, HAm inhibited the cell proliferation of MC3T3-E1 cells in a dose-dependent manner, but not in the presence of FCS. Inhibitory effect by HAm was observed only in directly contact with the cells. Similar inhibition effects by HAm were also observed on ALP activity of the cells. However, inhibitory effect by HAm on ALP extracted from the cells was not observed. After HAm treatment, ALP activity in the medium was increased. HAm pretreated with FCS did not inhibit the ALP activity of the cells at all. These results suggest that serum may play an important role in the biocompatibility of HAm and osteoblastic cells.