Glass reinforced hydroxyapatite for hard tissue surgery - Part II: in vitro evaluation of bone cell growth and function

Hydroxyapatite (HA)-based materials are considered to be potentially useful as bone implant materials, particularly those reinforced with glass to imp rove mechanical strength. However, the precise effects of glass-reinforced HA on the growth and functions of bone cells are still unclear. The present study has therefore examined the response of human osteoblast-like cells t o HA and HA reinforced with two different proportions of glass, namely 2.5% and 5%. All materials enabled the cells to attach and proliferate during 7 days in culture and, although the growth was less than on control plastic surfaces, there was no deleterious effect of the 5% glass composite compare d with HA alone. Flow cytometry analysis showed that there was no effect on cell size and granularity, but there were marked and highly selective chan ges in the expression of certain connective tissue proteins. Thus, while bo ne sialoprotein and osteonectin were down-regulated on HA alone, the expres sion of these antigens was relatively enhanced on the composite materials, and collagen type I was also up-regulated on the glass-reinforced HA. Thus, modulation of the glass composition of HA materials could be used to produ ce not only improved mechanical strength, but also enhanced biocompatibilit y. (C) 2001 Elsevier Science Ltd. All rights reserved.