Cytokine-Mediated Bone Destruction in Rheumatoid Arthritis

Figure 3

(a) Monocytes are differentiated into mature osteoclasts by the aid of RANKL. In pathological conditions such as inflammation, cancer, and hypermetabolism, various cells extraordinarily provide RANKL to the monocytes, resulting in overweighed osteoclastogenesis. In this condition, the osteoclasts outnumber the osteoblasts, disrupting the bone homeostasis. Bone erosion or osteoporosis is the major outcome of disrupted homeostasis. (b) In normal physiological conditions, a few cells, predominantly osteoblasts, express RANKL. A similar number of osteoclasts and osteoblasts maintain the bone mass by homeostatic equilibrium.