Fluoride-substituted apatites support proliferation and expression of human osteoblast phenotype in vitro

This study aimed to test the hypothesis that fluoride (F) ions released from F-substituted apatite (FAp) modulate osteoblast behavior in vitro. FAp samples of varying F concentrations (0.01, 0.08, 2.01 and 3.34 wt% F) were used in this study. Human osteoblasts (1×10⁵/well) were incubated in the presence or absence of Fap (5mg/well) for four days at 37°C, 5% CO₂. Viability, proliferative capacity by radiolabeled thymidine uptake and RNA were determined. Results showed the following: viability and proliferative capacity of cells exposed to FAp particle suspension were similar to control cells; collagen Type 1 expression was comparable in all groups whereas alkaline phosphatase expression was variable; and osteocalcin expression was enhanced in osteoblasts cells exposed to FAp with F concentrations 0.08 wt% and higher. These results demonstrated that F ions released from F-substituted apatites support proliferative capacity of human osteoblast cells and enhance osteocalcin expression. These findings suggest that fluoride may play a role in bone formation and therefore F-releasing bone graft materials may provide added advantage.