Immunohistochemical and Immuno-electron Microscopic Characterization of Mononuclear Cells in the Site of Alveolar Bone Remodeling

P(論文)
Mechanical force applied to a tooth evokes local cellular responses in the periodontal tissue and induces an adaptive remodeling of the alveolar bone. This event is mediated by a variety of mononuclear cells present in and/or recruited de novo from the bloodstream. In this study the author examined the kinetics of mononuclear cells in the crestarea of the inter-radicular alveolar bone of rat maxillary first molars by immuno-histochemistry and electron microscopy. Orthodontic elastic was inserted between the maxillary first and second molars of 10 to 11-week-old male Wistar rats. At 6 and 12hrs, 1, 2, 3, and 5 days after elastic insertion, the maxillae were fixed and decalcified. Cryostat sections were prepared for immunohistochemistry and vibratome sections for electron microscopic immuno-histochemistry. Consistently observed in the test area of unloading controls, ED1-positive mononuclear cells, indicative of all subtypes of monocyte/macrophage lineage, significantly increased in number 12hrs after elastic insertion, while there was no significant change in the number of tissue macrophage (ED2-positive) and cells expressing Ia antigen (OX6-positive). No infiltration of T cells was observed in the test area throughout the experimental period. The number of capillary loops expressing ICAM-1was increased 12hrs after elastic insertion. These immunohistochemical results suggest that mononuclear cells increasing in the test area are exudative types of monocyte/macrophage lineage. The time course of the recruitment of TRAP-positive mononuclear cells was almost parallel to that of ED1-positive mononuclear cells from which ED2-positive cells were subtracted, indicating a possibility that the majority of exudating cells are osteoclast precursors. Electron microscopically, three types of mononuclear cells were identified ; typical macrophages exhibiting active phagocytosis, cells with cytoplasmic profiles identical to those of osteoclasts, and cells with intermediate cytoplasmic profiles of the above two. Immuno-electron microscopically, ICAM-1 was expressed mostly in the mononuclear cells of osteoclast type, Mac-1 in osteoclast type and intermediate type, Ia antigenselectively in intermediate type. In the electron microscopic enzyme histochemistry, the reaction product for TRAP activity was detected not only in the mononuclear cells of osteoclast types but also intermediate type.