HSP47 as a Possible Molecular Chaperone for the Collagen Synthesis in the Mouse Periodontal Ligament Cells due to Orthodontic Force

Orthodontic mechanical stress induces various molecules, which cause structural changes in the proteins in periodontal tissue. The expression kinetics of HSP47 in mouse periodontal ligament (PDL) tissue after application of corrective mechanical stress and HSP47 expression during the PDL recovery were observed. Our examination data are as follows: HSP47 is constitutively expressed in the PDL and defends cells from different types of stress and maintains homeostasis under normal conditions. HSP47 is expressed in PDL fibroblasts on the pressure side damaged by application of mechanical stress and contributes to the repair of collagen tissue by activating PDL fibroblasts, supporting recovery from cell damage. These data suggests that, during bone addition to the PDL on the tension side, HSP47 also acts as molecular chaperone, which assists the maturation of bone morphogenetic proteins and aids osteoblast activation. On the other hand, it is possible that, when a mechanical stress is applied to the periodontal membrane on the tension side for a time too short for bone addition and abnormalities are caused in the collagen structure of the PDL fibroblasts, by functioning at the damage site, HSP47 inhibits extracellular secretion of abnormal collagen, stores the modified protein in the endoplasmic reticulum, thereby controlling decalcification of the PDL. HSP47 investigated in this study acts differently depending of the time of expression.