The mechanism of cell locomotion of cultured osteoclasts in three-dimensions ; the observation by time-cinematography

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Osteoclasts and macrophages of ddy strain mice were isolated, and then culturedwith or without dentine slices for 72 hours. After the incubation, tartrate-resistant acid phosphatase (TRACPase) and adic phosphateas (ACPase) activities were detected in them by the azo dye method. ACPasc-positive cells phagocytized indian inks, however, they showed neither TRACPase nor resosrptive activity. TRACPase-positive cells made lacunae on the dentine slices, and showed sthe ruffled border and clear zone. Therefore, ACPase-positive cells with phagocytosis were seemed to be macrophages, and TRACPase-positive cells were osteoclasts. These results suggested that TRACPase activity was specific for osteoclastic cells, not macrophages, in 72 hours culture of ddy mice.One multinucleated TRACPase-positive cell with comnplicated contours was observed on the dentine slice by light microscopy, and then this cell was serially sectioned by altermating semithin and ultrathin sections to observe its ultrastructure and three-dimensional sturcture. By transmission electron microscopy, this cell had the similar structure as those of osteoclasts, and possessed the clear zone-like structures, but showed no ruffled border. A three-dimensional reconstruction showed that this cell had very flat and complicated outlines, and extended its cell body to the back side of the dentine slice. These results suggested that this cell might be a locomoting osteoclast.