Effect of hydroxyapatite porosity on growth and differentiation of human osteoblast-like cells

To study whether hydroxyapatite (HA) porosity can influence its osteoconductive properties, cell adhesion, proliferation and differentiation were compared in human osteoblast-like cells grown on HA disks of different porosity (A = 20%, B = 40%, C = 60%). Human osteoblast-like cells were isolated and characterized. Proliferation rate and alkaline phosphatase (ALP) activity were assessed at 3, 7, 15, 21, and 28 days. Type I collagen and osteonectin production were demonstrated with fluorescence microscopy and osteoblast adhesion studied at 7 and 21 days by scanning electron microscopic analysis. Cell growth on HA was three- to six-fold lower than on polystyrene control disks. At 28 days, 2141 (+/-350) cells/well grew on the most porous disks (Group C), with highly significant differences from controls (p < 0.005). The ALP production was 2-3 fold lower on HA than on plastic. In the Group C the mean ALP activity was of 2.95 (+/-0.07) UI/well after 28 days, higher than in the other two groups. At 21 and 28 days, proliferation rate and ALP activity on the three HA cultures were significantly different (p < 0.05). A decrease in cell population and increased ALP activity were observed on the most porous material, and high proliferation and poor differentiation rates on the less porous disks. (C) 2002 Kluwer Academic Publishers.