Osteocytes are the most abundant cell type in bone; however, they remain the least characterised of these. Several theories have been proposed regarding their function, including osteolysis, sensing the strains produced in response to mechanical loading of bones and producing signals that affect the function of osteoblasts and osteoclasts as well as the expression of molecules that directly affect the turnover process. This review also discusses the role of osteocyte apoptosis in targeted bone remodeling and proposes that the incidence of osteocyte apoptosis is in line with the description of apoptosis as an essential homeostatic mechanism for the healthy maintenance of tissues.
Inappropriate targeting of bone remodeling underlies a number of musculoskeletal disease states including Pagets disease and Osteoporosis. The mechanism driving the targeting of bone resorption is unknown. Our previous studies have demonstrated a close association between regions of bone containing apoptotic osteocytes and resorption surfaces in both healthy and pathological conditions. Such findings raise the possibility of a currently unknown causal signaling mechanism between the dying osteocyte and effector cells at the bone surface.
Identification of the specific signals implicated in this phenomenon and the method by which they are delivered will profoundly increase our understanding of the effector cell targeting system in bone providing a platform to production of novel intervention strategies.