Periostin is the cell adhesion molecule of osteoblasts and their precursor cells. It is strongly expressed in the periosteum and is indirectly involved in bone formation and repair process. Moreover, it is expressed in connective tissues, such as periodontal ligament, tendons, heart valves, and skin fibers. The periostin protein gene in humans and rodents is located in chromosome 6p21 and the 17, respectively. Periostin protein has an N-terminal structure, a cysteine-rich structure, four homologous repeat region, and a C-terminal. It has a typical N-terminal signal sequence, which suggests that it may be a secretory protein. In the cap stage of tooth germ, periostin is expressed in the mesenchyme between the inner enamel epithelium and predentin, and around cervical loop. It is also expressed in the dental sac cell in the bell stage. The bell-shaped tooth dental follicle cells also contain periostin protein. In the process of moving the tooth, periostin is the local contributing factor of the remodeling process of bone and periodontal tissue under mechanical stress. The key factors of periodontal tissue repair and regeneration are the promotion of the cells derived from periodontal ligament cells, which preferentially adhere to the root surface, as well as the proliferation, differentiation, and formation of new periodontal ligament, cementum, and alveolar bone, that is, formation of new periodontal attachment. Periostin is a bone adhesion protein with a specific expression in periosteum and periodontal ligament tissue. It plays an important role in the early mineralization of bone cells and tissue differentiation.
