FIGURE 14.
Molecular control of bone resorption by the stroma-derived cell population. (Left) The stromal cells can be thought of as a rheostat in the resorptive process. M-CSF is required to activate the system, and once activated, the relative levels of RANK-L and OPG control osteoclastogenesis and resorptive activity. (Right) Both RANK receptors on the osteoclast (and pre-osteoclast) surface, and the soluble decoy OPG receptors in the extracellular fluid, bind RANK-L. The level of RANK-L and OPG therefore control the resorptive signal.