Bone remodelling - RANK/RANKL/OPG pathway regulation
Core concept
- Osteoblasts control osteoclasts. The osteoclast has no receptor for PTH, vitamin D or oestrogen - every signal reaches it through the osteoblast/stromal cell
- Three molecules, one decoy
- RANKL (osteoblast/stromal surface) binds RANK (osteoclast precursor) -> NF-kB -> differentiation, fusion, activation, survival of osteoclasts
- OPG (osteoprotegerin) - soluble decoy receptor for RANKL, secreted by osteoblasts
- *The RANKL:OPG ratio is the final common determinant of bone resorption*
- inc ratio -> resorption; dec ratio -> bone formation favoured
- M-CSF is the obligatory second signal (osteoclast precursor proliferation and RANK expression)
3 more sections, plus exam facts
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