The Distinct Roles of Growth/Differentiation Factor-5 in Cell Proliferation and Odontoblast Differentiation from Dental Pulp Cells

Growth/differentiation factor-5 (GDF-5) belongs to the bone morphogenetic protein (BMP) family, which is expressed in dental pulp tissues. To date, various studies have reported that BMP-family growth factors can induce cells isolated from dental pulp tissues to differentiate into odontoblasts. Nevertheless, the effect of GDF-5 on odontoblast differentiation from dental pulp tissues remains unknown. In this study, we assayed the effect of exogenous mouse recombinant GDF-5 on cell proliferation of dental pulp cells and determined the expression levels of odontoblast differentiation marker genes in the cells of isolated mouse dental pulp tissues in the presence of GDF-5. There were no significant differences in dental pulp cell proliferation patterns related to the absence or presence of GDF-5 after seven days of culture. Odontoblast marker gene levels, on the other hand, were significantly elevated after seven days of culture in the presence of GDF-5. GDF-5 also increased the gene expression and enzyme activity of alkaline phosphatase. Furthermore, dental pulp cells cultured in the presence of GDF-5 formed alizarin redpositive nodules after 10 days of culture. These results indicate that, although GDF-5 may have no effect on cell proliferation in isolated dental pulp tissue, it could promote odontoblast differentiation.