[Osteocytic osteolysis : measurements of the volume of osteocytic lacunae]

Osteocytes are present in osteocytic lacunae in both cortical and trabecular bone, where they are interconnected by numerous dendrites in osteocytic canaliculi. In mammals, osteocytes are the most abundant bone cells, outnumbering osteoclasts and osteoblasts. Osteoclasts are the primary bone-resorbing cells ; however, the concept that osteocytes resorb bone by a process called osteocytic osteolysis has been postulated to explain dynamic calcium release from bone in conditions as diverse as parathyroid hormone (PTH) stimulation, hibernation, glucocorticoid stimulation, and lactation. Osteocytic osteolysis remains a controversial concept, mainly because it is difficult to demonstrate experimentally. Recently, novel functions of osteocytes in mineral metabolism and bone remodeling have been reported, and osteocytic osteolysis is being examined more closely experimentally. This review discusses published literature relevant to osteocytic osteolysis and compares 2D and 3D measurements of the volume of osteocytic lacunae, which serve as anatomical evidence for "periosteocytic osteolysis" .