Inflammation-associated changes in bone homeostasis.

Bone is a dynamic tissue undergoing constant remodelling and repair. Its homeostasis is regulated by a coordinated process executed by bone forming and bone resorbing cells. Apart from being a major component of the locomotive system, bone provides protection for internal organs and represents a main mineral storage. Furthermore, it houses the haematopoietic system and is hence essential for the body's immune response. In turn, the innate and adaptive immune system itself, critically affect bone homeostasis. This is most evident during chronic inflammatory diseases, such as Rheumatoid Arthritis, where bone mass is critically reduced. Recently the field of osteoimmunology, focusing on this crosstalk between the immune system and bone homeostasis, has gained increasing attention. This review will highlight cellular and molecular mechanisms linking the innate and adaptive immune response to bone biology and provide an overview about involved cytokines and cells. Moreover, chronic inflammation and its consequences for bone turnover are discussed.