Characterization of the apatite crystals of bone and their maturation in osteoblast cell culture: comparison with native bone crystals.

Calcium phosphate crystals deposited in the organic matrix synthesized by chick bone osteoblasts in culture were studied by x-ray and electron diffraction, Fourier transform infrared spectroscopy and chemical composition. The amounts of mineral phase deposited with time and the extent of calcification (% of mineral phase in the tissue) were also determined as a function of time, as were the nature of the changes in the short range order of the crystals. The amount of mineral deposited and the extent of calcification increased with time; the tissue not only contained more crystals of apatite, but the extent of calcification also increased with time as it does in vivo. After 30 days of culture the extent of calcification in the cell culture matrix was similar to that in late chick embryonic and early postnatal chick tibiae. The nature of the CO3 and HPD4 environments were similar to those found in vivo although the concentrations of these ions and the changes in their concentrations with time appeared to develop more slowly in cell culture than they do in vivo. However, the general overall pathway of maturation was similar in cell culture to that observed in vivo.