Inhibitory effect of enamel matrix derivative on osteoblastic differentiation of rat calvaria cells in culture

Background and Objective:  The effect of enamel matrix derivative (EMD) on bone differentiation remains unclear. Transforming growth factor β1 (TGF - β1) is reported to be contained in EMD. The aim of this study was to clarify the effect of EMD on osteoblastic cell differentiation and the possible role of TGF - β1.
Material and Methods:  Fetal rat carvarial cells were treated with 10, 50 or 100 µg/ml EMD for 5–17 days. Alkaline phosphatase (ALP) activity and bone nodule formation were measured, and mRNA expressions of bone matrix proteins and core binding factor were analysed.
Results:  Enamel matrix derivative inhibited ALP activity from the early stage of culture (29–44% inhibition) on days 5 and 10 and decreased bone nodule formation by 37–67% on day 17. These effects of EMD were concentration dependent. Enamel matrix derivative inhibited mRNA expression of osteocalcin and core binding factor. A high level of the active form of TGF - β1 protein was detected in the conditioned medium treated with 100 µg/ml EMD. Treatment with TGF - β1 antibody partly restored the inhibitory effect of EMD on ALP activity.
Conclusion:  Enamel matrix derivative inhibited the osteoblastic differentiation of rat carvarial cells and this was partly mediated by an increase in the activated form of TGF - β1, suggesting that EMD may function initially to inhibit osteoblastic differentiation to allow a predominant formation of other periodontal tissues.