EVIDENCE THAT FAILURE OF OSTEOID BONE-MATRIX RESORPTION IS CAUSED BY PERTURBATION OF OSTEOCLAST POLARIZATION

Osteoclasts resorb bone by a complex dynamic process that initially in volves attachment, polarization and enzyme secretion, followed by thei r detachment and migration to new sites. In this study, we postulated that mineralized and osteoid bone matrix signal osteoclasts differentl y, resulting in the resorption of mineralized bone matrix only. We, th erefore, compared the cytoplasmic distribution of cytoskeletal protein s F-actin and vinculin using confocal laser-scanning microscopy in ost eoclasts cultured on mineralized and demineralized bone slices and cor related the observations with their functional activity. Our results h ave demonstrated significant differences in F-actin and vinculin stain ing patterns between osteoclasts cultured on mineralized bone matrix a nd those on demineralized bone matrix. In addition, the structural var iations were accompanied by significant differences in bone resorbing activity between osteoclasts grown on mineralized bone matrix and thos e on demineralized bone matrix after 24 h of culture - resorption only occurring in mineralized bone but not in demineralized bone. These re sults indicated that failure of osteoid bone resorption is caused by p erturbation of osteoclast polarization. (C) 1998 Chapman & Hall.