Fig. 1.

Schematic illustration of the bone-cell interaction model. R _u uncommitted osteoblast progenitor, R responding osteoblast, B active osteoblast responsible for bone formation, C _p osteoclast progenitor, C active osteoclast responsible for bone resorption, PTH parathyroid hormone, TGF-β transforming growth factor-β, OPG osteoprotegerin, RANK receptor activator of NF-κB, RANKL receptor activator of NF-κB ligand. RANK-RANKL-OPG regulatory pathway: RANKL binds to RANK and promotes osteoclast differentiation, while OPG inhibits this differentiation by binding RANKL. Definitions and values of the rate constants are provided in Tables 1 and 2. This figure and its legend are taken from Ref. [13] and were slightly modified