Three-dimensional quantitative analysis of CGRP during physiological tooth movement

Objectives:Calcitonin gene-related peptide (CGRP) has been shown to inhibit osteoclast activity and suggested to up-regulate osteoblast recruitment and osteogenic activity. There have been several studies that have reported the presence of the CGRP-ir fibers in the PDL. However, there has been no report that has quantitatively analyzed the CGRP-ir fibers in the PDL. Since nerve fibers ramify in several branches in 3-dimension, it is known to be extremely difficult to quantitatively analyze it in 2-dimension.Therefore, in the present study immuno-reactive (CGRP-ir)nerve fibers for CGRP were analyzed quantitatively in 3-dimensional images. Methods:Ten male Sprague-Dawley rats were used. Rats were deeply anesthetized with pentobarbital sodium and trransvascularly perfused with saline for exsanguinations followed by 4% formaldehyde and decalcified with 4.13% ethylene diaminetetraacetic acid disodium. These tissues were cut by cryostat and stained with an Anti -CGRP Rabbit, tartrate-resistant acid phosphatase, and alkaline phosphatase. The CGRP-ir nerve fibers , osteoclast and osteoblast were observed at periodontium of mesial root in first molar,using confocal laser scanning microscopy and reconstracted 3-dimentional images.The 3-dimensional images of CGRP-ir nerve fibers were analyzed quantitatively using Neuron -Tracer. The results were examined between the areas by two-way analysis of variance and Scheffe's F test for post hoc comparison. Results:The total length of CGRP nerve fibers in the mesial region were significantly longer than distal regions in the PDL. The total length of CGRP-ir nerve fibers were longest in the apical region compared to other regions. More osteoclasts were observed in the distal surface than mesial surface of alveolar bone. More osteoblasts were found in the mesial surface than distal surface.The fine CGRP -ir nerve fibers were located near to osteoblasts less than 3μm in mesial surface. Conclusion:It is suggested that CGRP-ir nerve fibers were related to osteoblastic activity.