Direct and indirect effects of P2O5 glass reinforced-hydroxyapatite composites on the growth and function of osteoblast-like cells

Human osteoblast-like cells were plated on hydroxyapatite and P2O5-glass re inforced hydroxyapatite composite discs. They were also cultured in the pre sence of media obtained by incubating the discs in the absence of cells. Th e effects of these direct and indirect interactions were examined by measur ing cell proliferation and the expression of certain key extracellular matr ix antigens. One composite was found to initially delay cell growth, while the extract of a different composite appeared to down-regulate DNA synthesi s. Flow cytometry analysis showed that growth directly on the discs had lit tle effect on collagen type I, but reduced fibronectin and osteocalcin leve ls. The extracts of the materials generally had less effect, although one e xtract obtained from the glass-reinforced hydroxyapatite significantly down -regulated fibronectin. These in vitro studies thus suggest that there were only few differences overall in the growth of the cells directly on the gl ass-reinforced compared with the hydroxyapatite discs and also only relativ ely small effects of the extracts on the cells. However, the flow cytometry results suggest that both the materials and the extracts may have a potent ially important influence on connective tissue production, and that these e ffects are both material- and antigen-specific. (C) 2000 Elsevier Science L td. All rights reserved.