Paracrine molecular mechanisms that regulate osteoclast formation and function.
Osteoclasts are derived from the same mononuclear cells that differentiate into macrophages.
Osteoblast/stromal cell membrane associated RANKL binds to its receptor RANK located on the cell surface of osteoclast precursors.
This interaction in the background of macrophage colony-stimulating factor (M-CSF) causes the precursor cells to produce functional osteoclasts.
Stromal cells also secrete osteoprotegerin (OPG), which acts as a “decoy” receptor for RANKL, preventing it from binding the RANK receptor on osteoclast precursors.
Consequently, OPG prevents bone resorption by inhibiting osteoclast differentiation.