Effects of adipocytokines on human pulpal fibroblasts

Objectives: Adipocytokines, such as adiponectin and leptin, are expressed by adipocytes and mediate fatty acid oxidation in fat tissue as well as glucose concentration in serum. They are also thought to mediate calcification in mineralized tissue. We investigated the effects of adiponectin and leptin on the kinetics of human pulp fibroblasts using ELISA and Western blotting techniques. Methods: After gaining informed consent, we obtained human pulpal fibroblasts from three patients. After cultivation in DMEM without serum, fibroblasts from the 4th to 6th passages were incubated with various concentrations of adiponectin (1, 10 or 100 ng/mL) in DME or leptin (0.1, 1 or 10 ng/mL) in DME for 24 h. Results: We confirmed that human pulpal fibroblasts express adiponectin receptor 1 and leptin receptor, but not adiponectin receptor 2. Although the proliferation index of these cells as measured by 5-bromo-2'-deoxyuridine (BrdU) incorporation increased in the presence of adiponectin in a dose-dependent manner, pulpal fibroblasts stimulated with leptin showed no significant changes in BrdU incorporation. Alkaline phosphatase activity showed no significant changes after stimulation with either adipocytokine. Adiponectin induced expression of BMP-2 and osteopontin more strongly than did leptin. In particular, expression of BMP-2 increased in the presence of adiponectin in a dose-dependent manner. In contrast, expression of dentin sialoprotein increased after stimulation with leptin. Conclusion: These results indicate that adiponectin may affect growth, differentiation and calcification of human pulpal fibroblasts, while leptin affects dentin formation.