title: Recent advances in the ultrastructural assessment of osteoclastic resorptive functions.
abstract: Ultrastructural enzyme and immunocytochemical studies have made great contributions to clarifying intriguing questions as to the actual role of osteoclastic ruffled borders in bone resorption. In the present study, vacuolar-type H(+)-ATPase and cysteine-proteinase (cathepsin) were localized in osteoclasts by means of light and electron microscopic immunocytochemistry. The specific immunoreactivity of vacuolar-type H(+)-ATPase was detected along the ruffled border membranes, associated pale vacuoles, and cisterns of the rough-surfaced endoplasmic reticulum of osteoclasts. Anti-cathepsin B immunoreaction occurred in Golgi vesicles, lysosomes, pale vesicles and vacuoles, and the extracellular canals of ruffled borders of osteoclasts. The resorbing bone surfaces were also immunoreactive for anti-cathepsin B. In a coculture system of osteoclasts with devitalized dentine slices, a specific H(+)-ATPase inhibitor (bafilomycin A1) markedly reduced both demineralized areas and resorption lacuna formation on the dentine slices. On the other hand, the cathepsin inhibitor, E-64, inhibited only resorption lacuna formation but had no effect on demineralization of the dentine slices. These results suggest that H(+)-ATPase and cathepsins in osteoclasts are involved, respectively, in the extracellular solubilization of apatite crystals and subsequent degradation of bone matrix and that the ruffled border-clear zone complex of osteoclasts is the main site of cell-matrix interactions during bone resorption processes.
authors.affiliation: Second Department of Oral Anatomy,School of Dentistry, Showa University, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Sasaki
mesh_terms: D000818:Animals; D001862:Bone Resorption / Q000378:metabolism; D002401:Cathepsin B / Q000378:metabolism*; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D007150:Immunohistochemistry; D051379:Mice; D010010:Osteoclasts / Q000378:metabolism* / Q000648:ultrastructure; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D003094:Collagen; D002401:Cathepsin B; D006180:Proton-Translocating ATPases