An Experimental Study of the Mechanism of Osteoclastic Bone Resorption by Specific Cytoskeleton Inhibitor

Abstract

To determine the role of actin filaments in osteoclastic function, osteoclastic multinucleated cells were suspended on dentine slices and cultured for 24 hours in the presence or absence of cytochalasin D (CD), a specific and potent inhibitor of actin filament elongation to determine the role of this cytoskeleton. Cultured cells and co-cultured dentine slices were examined by means of backscattered-and immuno-electron microscopy. Unlike those in control cultures without CD, osteoclasts in CD-treated cultures became spherical in shape and lacked microvilli on their basolateral cell surfaces. CD treatment induced a complete disappearance of the ruffled border-clear zone complexes in osteoclasts, which resulted in strong inhibition of the formation of resorption lacunae in a dose dependent manner. CD treatment also reduced intensity of immunoreaction of anti-actin in the ruffled borders of osteoclasts. These results suggest that the cytoarchitecture, as well as the bone-resorbing function, of the osteoclast is highly regulated by the F-actin-containing microfilamentous cytoskeleton in the ruffled border-clear zone complex