PROLIFERATION AND DIFFERENTIATION OF HUMAN TRABECULAR OSTEOBLASTIC CELLS ON HYDROXYAPATITE

In order to evaluate whether human osteoblastic cells differentiate no rmally on hydroxyapatite, we have compared the adhesion, proliferation , and differentiation of human trabecular (HT) osteoblastic cells on s ynthetic-dense hydroxyapatite and on standard plastic culture. We show here that initial HT cell attachment was 4-fold lower on hydroxyapati te than on plastic after 4 h of culture, and that normal cell attachme nt on hydroxyapatite was restored after 18 h of culture. HT cell proli feration was similar on the two substrates at 2-8 days of culture, but was lower on hydroxyapatite compared to plastic after 15 and 28 days of culture, as evaluated by DNA synthesis or cell number. HT cells cul tured on both substrates produced an abundant extracellular matrix whi ch immunostained for Type I collagen. The levels of carboxyterminal pr opeptide of Type I procollagen (P1CP) in the medium were lower in HT c ell cultures on hydroxyapatite than on plastic. In addition, (H-3)-pro line incorporation into matrix proteins and the mean thickness of matr ix layers were 52% and 26% lower, respectively, on hydroxyapatite comp ared to plastic after 4 weeks of culture, indicating that the total co llagenous matrix synthesized by HT cells was lower on hydroxyapatite. However, (H-3)-proline and calcium uptake expressed per cell was highe r on hydroxyapatite than on plastic. The results show that human osteo blastic cells attach, proliferate, and differentiate on dense hydroxya patite with a sequence similar to that of plastic. However, the growth of human osteoblastic cells is lower on hydroxyapatite in long-term c ulture, which results in a reduced amount of extracellular matrix, alt hough matrix production per cell may be increased. (C) 1997 John Wiley & Sons, Inc.