New knowledge on the origin, function and fate of osteoclasts

摘要: The most recent findings on the origin, life-span and fate of osteoclast can be summarized as follows. Osteoclasts originate from progenitor, mononuclear, lymphoid cells which reach bone surface through bloodstream. resorb by secreting lysosomal enzymes procollagenase in osteoclast-bone interspace. organic components matrix (first interfibrillary substance, then collagen fibrils) are digested extracellular space. Dislodged crystals residual constituents phagocytosed collected cytoplasmic vacuoles where they completely solubilized. ruffled border adjacent "clear" zone constitute resorbing apparatus, whose development is roughly proportional to activity. Osteoclast nuclei continuously incorporated shed, so that individual renewed. This makes extremely difficult determine. life each might theoretically continue long stimulus resorption persists sufficient available. Primary abnormalities osteoclasts induce pathologic skeletal changes, case osteopetrosis Paget's disease bone. Conversely, may damage osteoclasts, lead intoxication. When this happens, essentially characterized an underdeveloped border, pyknotic nuclei, detachment and, finally, shrinkage fragmentation. It not yet known whether these changes only occur conditions, or alterations senescent death even normal