Osteoclastogenesis--current knowledge and future perspectives.

The strength and integrity of the human skeleton depends on a delicate equilibrium between bone resorption by osteoclasts and bone formation by osteoblasts. This equilibrium is continuously compromised by a variety of genetic, humoral, and mechanical alterations. In osteoporosis, this balance shifts in favor of osteoclasts, and bone resorption exceeds bone formation. More detailed knowledge of the biology of osteoclasts and osteoclastogenesis has shown that the involved procedures can provide opportunities for developing therapeutic agents. Osteoclastogenesis is a multi-complex procedure that includes many stages, and each one of them presents as a potential target for therapeutic intervention, except for the stage of commitment of pre-osteoclasts,at least for the time being. Because the osteoclast is derived from the pluripotent hematopoietic stem cell, any intervention in this stage could result in serious adverse effects from the hematopoietic system. On the contrary, intervention in the later stages of differentiation, multi-nucleation, and activation, has proved to be very promising in the development of novel potent anti-resorptive agents. In the present review we summarized the current knowledge related to osteoclast differentiation and the new developing targets of pharmacological intervention in each stage of this extremely complicated and not completely elucidated process.