Bone morphogenetic protein signaling in joint homeostasis and disease.

Despite advances in therapies that target inflammation and tissue destruction in chronic arthritis, stimulation of tissue repair and restoration of joint function, the ultimate goal of treatment, is far from achieved. We introduce a new paradigm that may help to improve our understanding and management of chronic arthritis. The presence or absence of tissue responses distinguishes destructive arthritis, steady-state arthritis and remodeling arthritis. Increasing evidence suggests that reactivation of embryonic molecular pathways is an important mechanism to stimulate postnatal tissue repair. Bone Morphogenetic Proteins (BMPs) have critical roles in skeletal development and joint morphogenesis, but also in postnatal joint homeostasis and joint tissue remodeling. Therefore, modulation of BMP signaling may be an attractive therapeutic target in chronic arthritis to restore homeostasis and function of synovial joints.