Interleukin-17 is involved in orthodontically induced inflammatory root resorption in dental pulp cells

• Multinucleated cells were observed in the 50-g group in experimental tooth movements in rats.
• IL-17, IL-17R, and RANKL were found in dental pulp subjected to orthodontic force on day 7.
• IL-17 increased mRNA expression of RANKL and the ratio of RANKL/OPG from human dental pulp cells.

IntroductionThe objectives of this study were (1) to investigate the expressions of interleukin (IL)-17, RANKL (the receptor activator of NF-kappaB ligand), and osteoprotegerin (OPG) in root resorption areas during experimental tooth movement in rats, and (2) to determine the effect of IL-17 on the expressions of RANKL and OPG mRNA from human dental pulp cells.MethodsTwelve male 6-week-old Wistar rats were subjected to an orthodontic force of 50 g to induce a mesially tipping movement of the maxillary first molars for 7 days. The expression levels of tartrate resistant acid phosphatase (TRAP), interleukin (IL)-17, IL-17 receptor (IL-17R), receptor activator of nuclear factor-kappa B ligand (RANKL), and OPG proteins were determined in dental pulp by immunohistochemical analysis. Furthermore, the effects of IL-17 on the expressions of RANKL and OPG mRNA were investigated using human dental pulp cells in vitro.ResultsIn the experimental tooth movements in vivo, resorption lacunae with multinucleated cells were observed in the 50-g group. The immunoreactivities for IL-17, IL-17R, and RANKL were detected in dental pulp tissues subjected to the orthodontic force on day 7. Moreover, IL-17 increased the mRNA expression of RANKL from human dental pulp cells in vitro.ConclusionsThe results of this study suggest that IL-17 and RANKL may be involved in the process of orthodontically induced inflammatory root resorption in dental pulp cells.