Proliferation and differentiation rates of a human osteoblast-like cell line (SaOS-2) in contact with different bone substitute materials.

The aim of our study was to investigate the influence of four bone substitutes on the growth behavior of a human osteoblast-like cell line (SaOS-2) culture: pure alpha tricalcium phosphate (alpha-TCP = BIOBASE), a bioactive glass (bioglass), a neutralized glass-ceramic (GB9N), and solvent dehydrated bone. We established an in vitro cell culture model with three-dimensional scaffolds (cubes of 0.7 x 0.7 x 1.0 cm) of porous bone substitutes to investigate proliferation and differentiation rates of SaOS-2 cells. The cultures were analyzed for individual cell morphology after 5 days of growing using scanning electron microscopy. Fracture preparations of the cubes showed that cells could infiltrate the porous structures, but the cell shapes varied from individual round-shaped cells to wide spread cells and cell clusters, depending on the material. Also, the differentiation of the seeded cells was dissimilar after a 5-day incubation. The specific alkaline phosphatase (ALP) enzyme activity (ALP/DNA) measured in the supernatants of alpha-TCP-grown cells was nine times higher than the lowest activity, as observed by cells incubated on GB9N. Early (Collagen1, ALP) and late marker (osteocalcin, bone sialoprotein) of osteoblastic differentiation were proofed by reverse transcriptase-polymerase chain reaction analysis. Cells grown on bone substitutes and bioglass seem to be less differentiated than alpha-TCP-grown cells, because of noticeably less amounts of osteocalcin and bone sialoprotein. The cultivation on GB9N seems to dedifferentiate the cells, because even the ALP expression was reduced as well. Our results indicate that distinct bone substitutes influence proliferation and differentiation of osteoblastic cells in different manners. These results might influence the selection of an adequate bone substitute for clinical use as well, part from degradative and biomechanical properties.