Effects of Arachidonic Acid, Docosahexaenoic Acid, Prostaglandin E2 (PGE2), Oestrogen and Parathyroid Hormone on Osteoprotegerin (OPG) and RANKL Secretion by MG-63 and MC3T3-E1 Osteoblast-like Cells

Bone is continuously remodeled through resorption by osteoclasts and the subsequent synthesis of bone matrix by osteoblasts. (Refer to 2.4). The remodeling cycle is finely regulated by a variety of systemic and local factors e.g. oestrogen, parathyroid hormone (PTH), 1,25(OH)2D3, growth factors and cytokines. (Refer to 2.5). Cell-to-cell contact between osteoblasts (or bone marrow stroma cells) and hematopoietic osteoclast precursors (present in bone marrow, spleen, and peripheral blood) is required for osteoclast formation. (Refer to 2.3.3.2). During the past decade various research groups have identified some of the proteins involved in the interaction between cells of osteoblastic and osteoclastic lineage. These proteins belong to the families of tumor necrosis factors and receptors 8-12 and comprises RANKL (Receptor activator of nuclear factor-κB ligand) and its cognate receptor RANK (Receptor activator of nuclear factor-κB), as well as a decoy receptor osteoprotegerin (OPG).