[Morphological changes of osteogenic cells on hydroxyapatite ceramics sintered at different temperatures].

In order to clarify the relation between the synthetic condition and the biocompatibility in vitro, a dynamics of the osteogenic MC3T3-E1 cells cultured on hydroxyapatite ceramics (HAC) was examined. HAC used in this study was sintered at temperatures of 1000 degrees C or 1350 degrees C to produce the dense ceramics material, and then smoothly surfaced (0.3 micron). Disk (diameter: 10mm, thickness: 1mm) of HAC were placed in plastic disk. The cells were inoculated at 3000 cells/disk on HAC, and cultured for up to 18 Days. In scanning electron microscopic observation, cell proliferation cultured on the polished HAC was more active than that on the unpolished HAC. Furthermore, cell proliferation cultured on the 1000 degrees C-HAC was more active than that on the 1350 degrees C-HAC. Width, length and concentration of microvilli (MV) on the cell surface cultured on the 1000 degrees C-HAC were more dense, and increased with cultivation. Length and concentration of MV of the cells cultured on the 1000 degrees C-HAC were more dense than that on the 1350 degrees C-HAC. Most of the cells cultured on each material were intensely positive with alkaline phosphatase or von Kossa staining. However, the cells cultured on the 1000 degrees C-HAC were more positive than those on 1350 degrees C-HAC. In conclusion, these results suggest that the synthetic condition of HAC have close connection with the biocompatibility.

[Surface morphology of osteogenic cell].

In order to clear the relation between cell activity and morphology of their microvilli (MV), osteogenic MC3T3E-1 cells were cultured on plastic cover slips. Those cells have the capacity to differentiate into osteoblasts and mineralize in vitro. Histochemically, alkaline phosphatase (ALP) positive cells appeared with ALP staining at 4 days, and they increased gradually day by day. However ALP activity advanced rapidly in the culture adding dexamethasone (Dex) into the medium from 6 to 12 days culture. In scanning electron microscopic study, MV were observed on the surface of irregularly-shaped spread cells from 4 to 12 days. At the early stage, MV showed like fine filaments. Concentration, width and length of MV increased gradually with cultivation. On day 12, the long MV with a few particles were observed to some degree. In the presence of Dex, concentration and length of MV were much better than in the absence of Dex. Furthermore MV with many particles were seen more frequently. These results demonstrate that development of MV have close connection with differentiation of the cells.

Osteocompatibility of platinum-plated titanium assessed in vitro.

Suppression of dissolution is important to increase the biocompatibility of titanium implants. Therefore, the possibility of application of platinum-coated titanium as a biomaterial was explored in in vitro experiments using the MC3T3-E1 osteogenic cell line. The data obtained from long-term cultures indicated that pure platinum or titanium thickly coated with platinum inhibited calcification significantly, suggesting that the platinum ion fails to improve the osteocompatibility of titanium implants.