T-helper 17 cells mediate the osteo/odontoclastogenesis induced by excessive orthodontic forces.
OBJECTIVE
The aim of this study was to investigate how T-helper 17 cells (Th17 cells), interleukin (IL)-17, and interleukin-6 contribute to root resorption during orthodontic tooth movement.


METHODS
Fifteen male 6-week-old Wistar rats were subjected to orthodontic force of 10 or 50 g to induce a mesially tipping movement of the upper first molars for 7 days. The expression levels of TRAP, IL-17, the IL-17 receptor (IL-17R), and IL-6 proteins were determined in periodontal ligament (PDL) by immunohistochemical analysis. Moreover, the fluorescent localization immunoassay was performed to detect Th17 cells. Furthermore, the effects of IL-17 on IL-6 release were investigated using human PDL cells in vitro. The effect of IL-17 on osteoclastogenesis was evaluated by TRAP staining, actin ring staining, and the pit formation assay.


RESULTS
The immunoreactivity for Th17, IL-17, IL-17R, and IL-6 was detected in PDL tissue subjected to the orthodontic force on day 7. IL-17 increased the release of IL-6 from human periodontal ligament cells in a time-dependent manner. Moreover, IL-17 stimulated osteoclastogenesis from human osteoclast precursor cells, and these effects were partially suppressed by an anti-IL-6 antibody.


CONCLUSIONS
These results suggest that Th17 cells may aggravate the process of orthodontically induced inflammatory root resorption.
Department of Orthodontics, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
N
N
Hayashi
M
M
Yamaguchi
R
R
Nakajima
T
T
Utsunomiya
H
H
Yamamoto
K
K
Kasai
D000135:Acid Phosphatase / Q000032:analysis; D000199:Actins / Q000032:analysis; D000293:Adolescent; D000818:Animals; D015415:Biomarkers / Q000032:analysis; D001696:Biomechanical Phenomena; D018929:Cell Culture Techniques; D002460:Cell Line; D003238:Connective Tissue / Q000473:pathology; D003804:Dentin / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005347:Fibroblasts / Q000473:pathology; D006801:Humans; D020381:Interleukin-17 / Q000032:analysis / Q000494:pharmacology; D015850:Interleukin-6 / Q000032:analysis; D007527:Isoenzymes / Q000032:analysis; D008297:Male; D008963:Molar / Q000473:pathology; D009969:Orthodontic Wires; D010010:Osteoclasts / Q000187:drug effects / Q000276:immunology*; D010513:Periodontal Ligament / Q000187:drug effects / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D053722:Receptors, Interleukin-17 / Q000032:analysis; D012391:Root Resorption / Q000276:immunology / Q000473:pathology; D013314:Stress, Mechanical; D000071681:Tartrate-Resistant Acid Phosphatase; D058504:Th17 Cells / Q000276:immunology*; D013997:Time Factors; D014087:Tooth Movement Techniques / Q000295:instrumentation / Q000379:methods*
D000199:Actins; D015415:Biomarkers; D020381:Interleukin-17; D015850:Interleukin-6; D007527:Isoenzymes; D053722:Receptors, Interleukin-17; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase