Osteocyte density changes in aging and osteoporosis

Recently, it was suggested that osteocytes are involved in the regulation of bone remodeling. We have examined human trabecular bone of the iliac crest of fracture patients and control subjects to determine if osteoporosis is associated with changes in osteocyte density or osteocyte death. The relationships of these parameters with age was also investigated. It was found that osteocyte death was not related to age, nor was it increased in osteoporosis compared with the controls. In healthy adults ranging from 30 to 91 years, lacunar number per bone area decreases with advancing age, from about 210/mm(2) to 150/mm(2). Significantly higher lacunar and osteocyte numbers per bone tissue volume were found in osteoporotics than in controls (17,100 lacunae/mm(3) and 13,300 osteocytes/mm(3) vs. 12,900 lacunae/mm(3) and 10,500 osteocytes/mm(3), respectively), whereas lacunar area was significantly reduced in osteoporotics (from 44.1 mu m(3) to 39.1 mu m(2)). These findings are compatible with the hypothesis that, in osteoporosis, osteoblasts produce less bone per cell. This can in turn explain the reduced wall thickness, which has previously been described as characteristic for osteoporosis.