Objectives: Growth/Differentiation Factor-5 (GDF-5) is a member of the Transforming Growth Factor-ß superfamily and plays important roles in development of bones, cartilages, tendons, and ligaments. It has been reported that GDF-5 gene is expressed in dental sac, periodontal ligament and dental pulp cells, and odontoblasts during tooth development. However, the roles of GDF-5 in the differentiation of dental pulp cells are unknown. Thus, we investigated the effect of GDF-5 on the differentiation of dental pulp cells. We hypothesized that GDF-5 promotes differentiation of osteoblasts and odontoblasts from dental pulp cells. Methods: Mouse dental pulp cells were isolated from first molars of 1-week-old mice. After 2 or 4 passages, cells were cultured with or without recombinant mouse GDF-5 protein. The cell numbers were assayed by tetrazolium at each time point after 2, 4, 7 and 10 days of culture. Gene expressions related to the odontoblastic phenotype, such as those of alkaline phosphatase (ALP), osteopontin (OPN), bone sialoprotein (BSP) and dentin sialophosphoprotein (DSPP) were assayed by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) after 7 days. Gene expression levels were relatively evaluated against GAPDH, and statistically analyzed by using Fishers test. Results: Increase in cell number was not significantly different between in the presence or absence of recombinant GDF-5 after 7 days of culture despite of increase in the presence of basic fibroblast growth factor, which is a positive control of proliferation. In contrast, Gene expression of ALP, OPN and BSP increased significantly in the presence of GDF-5. Gene expression of DSPP was higher in the GDF-5-stimulated culture than that in the culture without GDF-5. Conclusion: GDF-5 promoted production of molecules characteristic for odontoblastic and/or osteoblastic phenotype, while it did not influence to cell proliferation. These findings suggested that GDF-5 could be useful for bone and dentin regeneration.

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