Orthodontic tooth movement and HMGB1

Background: High mobility group box 1 (HMGB1) has been recognized as a DNA binding protein that modulates transcription, and is secreted by activated dendritic cells, macrophages, and necrotic cells. Alveolar bone resorption in the compression zone and bone formation in the tension zone of the periodontal ligament (PDL) ensure that it is possible to move the tooth during orthodontic treatment. Considering that the ankylosed tooth and the dental implant cannot be moved, the PDL fibroblasts play an important role in bone remodeling during orthodontic tooth movement (OTM). In the compression zone of the PDL, cell death and necrotic degenerative tissues cause an aseptic inflammatory reaction, which results in the removal of the tissues by macrophages and foreign body giant cells. This is followed by the undermining resorption of the bone by osteoclasts. These findings suggest that HMGB1 is involved in tissue remodeling during OTM. In this manuscript, research papers published from 2013 onwards that investigated the relationship between OTM and HMGB1 are reviewed. Highlight: The HMGB1 was induced in the PDL of experimental animals during OTM. Cell culture experiments using PDL fibroblasts revealed that induction of HMGB1 expression in PDL cells is mediated by mechanical stress. In addition, HMGB1 is partly involved in macrophage migration and osteoclastogenesis. Furthermore, HMGB1 partially augmented cell proliferation, migration, and osteoblastic differentiation in PDL cells. Conclusion: Orthodontic force modulates HMGB1 expression in PDL fibroblasts, and HMGB1 is an accessory regulator of bone resorption and bone formation during OTM. (C) 2018 Japanese Association for Oral Biology. Published by Elsevier B.V. All rights reserved.