[Molecular mechanisms of bone destruction in rheumatoid arthritis].

Osteoclast in the synovium of rheumatoid arthritis (RA) plays an important role for bone destruction of the affected joints. The osteoclast is differentiated from macrophage-like synoviocyte, which is migrated from peripheral blood monocytes. In the RA synovium, receptor activator of NF-kappaB ligand (RANKL) which is expressed by T cells and fibroblast-like synoviocytes (FLS) and macrophage colony-stimulating factor (M-CSF) which is expressed by FLS induce the differentiation into osteoclast from macrophage-like synoviocyte. TNF-alpha, interleukin (IL) -1, IL-6, and IL-17 which are expressed by macrophages, FLS, and/or T cells in the synovium enhance the differentiation and activation of the osteoclast. Thus, such synovial cells contribute osteoclastgenesis and bone destruction.