Abstract
Heat shock proteins (HSPs) play an important role in maintaining protein homeostasis within the cell, and they are also related to inflammation. However, it is not clear how HSPs regulate inflammatory cytokines in periodontal ligament (PDL) cells during mechanical stress. The present study focuses on the expression of HSP70 in the PDL during experimental tooth movement in rats. A total of 35 6-week-old male Wistar rats were subjected to orthodontic force of 10 g to induce mesial tipping movement of the upper first molars. Experimental tooth movement was accomplished for 14 days. We determined the expression of HSP70 proteins in the PDL during orthodontic tooth movement by immunohistochemistry. HSP70 immunoreactivity was detected in PDL fibroblasts on the compressive side by an orthodontic force of 10 g. On day 1 after tooth movement, the immunoreactivity of HSP70 was weak. On days 2, 3 and 4, we identified a greater positive reaction for HSP70 in the nucleus of fibroblasts than that recognized on the first day. The HSP70-positive reaction further increased on days 7 and 14. From our quantitative evaluation, the rate of HSP70-positive PDL fibroblasts significantly increased compared with control fibroblasts, and this occurred in a time-dependent manner. Therefore, HSP70 may function as a homeostatic factor to compensate for PDL-cell changes that occur during orthodontic force.
