Possible effects of various neuropeptides on cells related to bone resorption during tooth movement

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In this study, we investigated altered binding of neouropeptides such as CGRP to PDL cells including osteoclasts during experimental tooth movement. Heat Shock Protein (HSP)-immunoreactivity in the rat PDL and its change were also examined immunohistochemically since the orthodontic force had been thought to possibly induce alterations in the expression of stress protein like HSP. 50-day-old Wistar strain rats were used. Experimental tooth movement was performed according to Waldo's method.Each animal was euthanized at each appointed time. After decalcification, serial horizontal frozen sections, 40 μ in thickness were cut. Free-floating sections were processed for the ABC method by the use of an antiserum to each substance such as CGRP, Substance P or HSP.The following results were obtained :1. The nerve fibers containing CGRP and/or Substance P observed under physiological condition decreased or disappeared immediately after the onset of treatment, and then began to increase gradually a few days later again.2. CGRP-immunoreactivity was seen in the alveolar osteoblasts on the surface of newly formed osteoid in the tension site. Both CGRP- and Substance P-immunoreactivity were observed in some osteoclasts existing in the Hawship lacunae in the compression site. On the other hand, In vitro, addition of CGRP to cultured osteoclasts caused inhibition of osteoclastic activity.3. Immunohistochemical staining intensity for HSP in the PDL showed significant change during tooth movement, suggesting that HSP may be associated with defensive responses against physical or chemical stimuli with orthodontic tooth movement.