[Cytokines and osteoclastic action].

In spite of the major advances in our knowledge of the cell biology of the osteoclast, many questions still remain to be answered: where does the osteoclast comes from, what is his fate and how it is activated. Bone resorption is considered in a global perspective as the resultant of two successive steps which are the formation of osteoclast progenitors in hematopoietic tissues, the generation of osteoclasts in bone and the activation of osteoclasts at the contact of mineralized bone. Activated osteoclasts resorb both the mineral and the organic of mineralized bone. All these steps are regulated by hormones and growth factors. Hormones have been studied extensively, but recent work has reveal that growth factors also have significant effects on bone function. The purpose of this article is to review current knowledge in the area of the biology of the osteoclast and to index all the growth factors that are known to act mainly on the formation and/or the activation of the osteoclasts.