Mechanisms of bone resorption.

Abstract

Resorption of mineralized tissues like bone is accomplished by a unique cell type: the osteoclast. This multinucleated cell has the capacity to dissolve the mineral by lowering the pH. Subsequently, the release of certain proteolytic enzymes, in particular cathepsin K, results in the digestion of the organic matrix mainly consisting of collagen. In this short review we will describe the unique features of the osteoclast making it possible for the cell to resorb mineralized tissues. • Multinucleated osteoclasts have the unique properties to resorb bone. • The osteoclast first lowers the pH in an area secluded by the sealing zone and dissolves the mineral. • Then proteolytic enzymes (e.g. cathepsin K) are released resulting in degradation of the organic matrix. • Osteoclasts resorb bone by making pits and/or trenches.