Alterations in staining intensity for calcitonin gene-related peptide (CGRP) in osteoblasts of the periodontal ligament during orthodontic tooth movement

抄録

Calcitonin gene-related peptide (CGRP) is a neuropeptide, which has multiple functions, and CGRP-containing nerves are prolific in the periodontal tissues. Tooth movement accompanies active tissue remodeling, including bone formation and resorption in the periodontal ligament. Although it has been suggested that CGRP contributes to tissue remodeling incident to tooth movement, little information is available for this issue. In the present study, immunohistochemistry combined with a computer-assisted quantitative analysis was employed to examine chronological changes in staining intensity for CGRP in osteoblasts during experimental tooth movement. The maxillary canine on one side was moved distally and fixed for 1 h to 56 days, leaving an untreated canine at the opposite side to serve as a control. Undecalcified sagittal sections of each maxilla, 6 μm in thickness, were processed by immunohistochemistry for CGRP. The distal alveolar bone around the root apex was selected for the analysis because of active bone formation in this area, due to constant tension during tooth movement. Percent staining intensity (SI) for osteoblastic CGRP in the experimental and control groups was calculated using a Zeiss microphotometer equipped with a Microscope Analysis with Photometric Scanning (MAPS) program. The mean SI for CGRP increased daily, peaked at postoperative Day 7, and decreased gradually thereafter. The relative ratio of SI in the experimental and control groups was about 200% at 1 h postoperatively and increased to approximately 300% during postoperative Days 7—14. The surface area of CGRP-labeled osteoblasts also showed the same alternation pattern as that of SI. These findings indicate that CGRP is released from neurons and can be bound to osteoblasts, and that orthodontic forces can alter the levels of SI for CGRP, suggesting the involvement of CGRP in regulation of osteoblastic activity. High SI for CGRP in the osteoblasts at time periods when the surface area of osteoblasts was increased, suggests that CGRP possibly participates in mediating the effects of orthodontic forces on alveolar osteoblasts.