Evaluation of the effect of three calcium phosphate powders on osteoblast cells.

The aim of the present study was to assess the effect of three calcium phosphate powders entering in the composition of bone substitute materials on osteoblast-cells activity. These powders were hydroxyapatite (HA) widely used as a biomaterial, nanocrystalline carbonate apatite (C A) very close to bone mineral crystals, and an experimental one: calcium phosphate cement-1 (CPC-1) composed of an amorphous Ca-P phase and brushite. The powders were physico-chemically characterized. The very reactive CPC-1 powder became transformed in cell culture medium: recrystallization of amorphous precursors and hydrolysis of brushite into poorly crystalline apatite occurred. Osteoblast-cells activity was evaluated: for low level of calcium phosphates (>100 microg/ml) CPC-1 enhanced proliferation and, to a lesser degree, differentiation on alkaline phosphatase activity. For 100 microg/ml of powders we observed a great alteration of biological activity of the osteoblasts: evaluation of proliferation indicated an inhibition for all samples, and a decrease of two differentiation markers: alkaline phosphatase activity and osteocalcin release were noticed, suggesting a down regulation due to the presence of large amount of mineral powder. Copyright 2001 Kluwer Academic Publishers