Expression of heat shock protein 47 in the periodontal ligament during orthodontic tooth movement

Abstract

The aim of this study was to investigate the kinetics of heat shock protein 47 (HSP47) and proliferating cell nuclear antigen (PCNA) immunohistochemistry in periodontal ligament (PDL) cells during orthodontic tooth movement in a mouse model. An orthodontic appliance was set between the upper incisors and the upper left first molar. The mice were killed 2, 6 and 10 days after initiation of orthodontic tooth movement. Computer-assisted image analysis was used to compare the quantitative expression of HSP47 in the PDL. HSP47 expression was significantly higher on the tension side 2 days after application of the appliance, whereas no significant change was observed on the pressure side at any time point. Furthermore, the PCNA labelling indices of PDL cells were increased significantly on the tension side 6 and 10 days after application of the appliance, and on the pressure side 2, 6 and 10 days after application of the appliance. These data suggest that collagen is metabolised predominantly on the tension side, and that PDL cells actively proliferate on both the tension and pressure sides during orthodontic tooth movement.