TNF and bone.

Bone is subject to permanent remodeling during development and through life. This activity is essential for (a) proper shaping and growth of each bone during development; (b) maintenance of bone mass as well as structural integrity of the micro architecture of bone through adult life, and (c) tissue repair needed for healing of fracture as well as of micro-damage. In addition to genetically linked rare developmental diseases, disturbances in bone remodeling are causing common bone pathologies, which severely impair the quality of life of patients. Among them are postmenopausal osteoporosis and local as well as systemic bone loss observed in chronic inflammatory diseases such as rheumatoid arthritis. The role of TNF-alpha in mediating bone remodeling will be presented and discussed in this chapter.