To investigate the effect of fibronectin (FN) and/or RGDS tetrapeptide on osteoblastic proliferation and osteopontin expression.

Osteoblasts were cultured on tissue culture polystyrene (TCPS) and apatite-wallastonite glass ceramics (AW-GC) with or without FN and RGDS synthetic tetrapeptide. Osteoblastic proliferation and differentiation were measured after cultivation, by determining the number of attached cells, by [3H]-thymidine assay, and by measuring the activity of alkaline phosphatase. The expression of osteopontin (OPN) was determined by RT-PCR and western blotting.

Cellular proliferation was more increased by FN than the other variables examined (P<0.03). OPN mRNA expression by RT-PCR was induced two-fold, 24-hour after FN treatment (P<0.05). The expression of OPN by western blotting showed a five-fold increase in cells treated with FN compared with the controls. The synthetic RGDS peptides partially blocked the growth of cells induced by FN (P<0.05). RGDS tetrapeptide alone increased the OPN expression induced by cultured osteoblasts (P<0.05).

FN enhanced osteoblastic proliferation on glass ceramics and induced OPN expression. Integrin occupancy by RGD-containing molecules may play a role in the process of osteoblastic proliferation rather than in osteoblastic differentiation.