The Effect of Paricalcitol on Osteoprotegerin Production by Human Peripheral Blood Mononuclear Cells

It has been known for years that the ratio of receptor activator of nuclear factor-κB ligand (RANKL) relative to its decoy receptor, osteoprotegerin (OPG), controls osteoclastogenesis. Under normal conditions the main source of RANKL and OPG is the osteoblast. Osteoblasts express on their surface RANKL that induces the formation of osteclasts from their precursors as well as their survival and activation. OPG is also produced and then secreted by the osteblasts, but it inhibits osteoclast formation by binding to RANKL and preventing binding to its receptor RANK on the surface of the osteoclasts’ precursors1. However, a recent study suggests that both B and T lymphocytes also play a significant role in basal bone turnover, since T cells help B cells to produce 65% of total OPG in bone marrow in mice2. In inflammatory diseases the participation of activated lymphocytes in pathological bone erosion is established3. Vitamin D promotes … Address reprint requests to Dr. T. Eleftheriadis, Department of Nephrology, General Hospital of Serres, 3rd km Serres-Drama, 62100 Serres, Greece. E-mail: teleftheriadis{at}yahoo.com