HSP70 is Highly Expressed in Pdl During the Tooth Movement

Objectives: A continuous orthodontic force on the tooth is considered to be a kind of physical stress loaded to the periodontal ligament. This stress causes a circulatory disturbance such as ischemia and hypoxia in the pressure zone of the periodontal ligament. We demonstrated that the gene of Heat Shock Protein 70 (HSP70) was highly expressed in the pressure zone of the PDL after 6 hours of tooth movement (JADR2007). In this study we investigate the longitudinal changes of the HSP70 in the PDL during tooth movement, using microallay analysis and immunohistochemistry. Methods: 12 weeks old Wistar rats were divided into four groups (n=12): Tooth movement group (6hours, 24hours, 5days after tooth movement ) and control group ( without tooth movement ). The maxillary first molars were moved lingually with the fixed appliances ( orthodontic force 10g ). After tooth movement, maxilla of the rats was dissected. 7-µm thick undecalcified frozen sections of the first molar areas were used in this study. Gene expression in the pressure zone of the PDL cells and control groups was examined respectively, using laser-captured micro dissection and microarray analysis. Localization of HSP70 in the PDL was also examined with immunohistochemistry. Results: The gene expression of HSP70 in the pressure zone of PDL was higher in 6 hours of the tooth movement than that in the control group. The expression of HSP70 was decreased with the course of time. Meanwhile, HSP70 was detected in the pressure zone of the PDL at protein level in 24 hours when the initial tissue change had occurred. Conclusions: These results suggest that the expression of HSP70 in the early stage of tooth movement is a critical factor in the tissue reaction of PDL during tooth movement.