Periostin and Twist mRNA Expression in the Hypofunctional Mouse Periodontal Ligament

Periostin is a secreted protein preferentially expressed in the periodontal ligament (PDL) and the periosteum. In a previous study it has been demonstrated that periostin had putative roles during tooth movement. Recently, it was also reported that Twist, a basic helix-loop-helix transcription factor important for cell type determination and differentiation, could bind to the periostin promoter in undifferentiated preosteoblasts and promote periostin gene expression in vitro. Since occlusal force is thought to be important in the homeostasis of the PDL, the expression of periostin and Twist mRNA in the mouse periodontal tissue following removal of antagonizing teeth was investigated in this study. Unilateral maxillary tooth extraction was performed in 3-week-old male mice to produce occlusal hypofunction of the right mandibular molars. The expressions of periostin and Twist mRNA were examined by real-time PCR and in situ hybridization at 12, 24, 72 and 168 hours after the tooth extraction. Periostin and Twist mRNA expressions at 24 hours following removal of occlusal force were significantly decreased to 14.5% and 49.9% of the control level, respectively. A recovery was observed at 72 hours, and at 168 hours no significant difference was observed. As determined by in situ hybridization, the number of periostin- and Twist-mRNA expressing cells showed a remarkable decrease at 24 hours, although a gradual increase was observed from 72 hours until the distribution was almost identical to that of normal animals at 168 hours. These results suggested that occlusal force might have putative roles in periostin and Twist gene expression in the PDL.