Interleukin-17 expression induced by orthodontic force in periodontal ligament in different periodontal condition

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To investigate interleukin (IL)-17 expression induced by orthodontic force in periodontal ligament under different periodontal conditions. Seventy-seven male SD rats were divided randomly into 5 groups: healthy movement group (HM), active periodontitis movement group (PM) recovery periodontitis movement group (RM), positive control group (PC) and normal control group (NC). Active periodontitis was set up by means of ligature + susceptible bacteria + suger water in PM, PC and RM groups. This stimulating factor was removed in RM group. NiTi spring was used to apply 0.49 N mesial force to move upper first molar of the rats in HM, PM and RM groups. HM, PM and RM group rats were sacrificed on day 3 (d3), day 7 (d7) and day 14 (d14). Expression changes of IL-17 in periodontal tissue in each group were measured using immunohistochemical stain and real time fluorescence quantitative PCR. IL-17 expression in periodontal ligament showed more positively in PM and RM groups compared with NC, PC and HM groups. No difference was found in the expression of IL-17 mRNA in NC (1.00 ± 0.00) (P > 0.05), except in HM d14 (1.00 ± 0.07) and RM d14 (1.19 ± 0.15). Higher expression of IL-17 mRNA (P < 0.05) was found in other groups. The expression of IL-17 mRNA in RM d3 and d7 increased more than that in HM group in the same period (P < 0.05) and it decreased significantly (P < 0.05) compared with that in PM groups in the same period. IL-17 was involved in the regulation of orthodontic tooth movement in different periodontal conditions. Orthodontic force caused limited increase of IL-17 mRNA expression in recovery phase of periodontitis at early stage, then back to normal. However, in active inflammatory periodontal tissue, orthodontic force kept IL-17 mRNA at high level.