[Recent advances in biology of bone resorption]

Bone resorption is a unique process which requires function of highly specialized cells, i.e., osteoclasts, Osteoclasts are terminally differentiated multinuclear cells that originate from multipotent hematopoietic stem cells and are closely related to the monocyte/macrophage lineage. Recent advances in molecular biological techniques and development of useful experimental systems both in vitro and in vivo have made it possible to identify several factors essential to osteoclast differentiation or function under physiological and/or pathological conditions. Such factors include transcription factors such as c-Fos and PU.1, cytokines such as IL-6 and TNF-alpha, and other various molecules such as tyrosine kinases and adhesion molecules. This review will focus on recent progress in our understanding of osteoclast biology.