Osteobridging protein (OPN), also known as BSP-1, ETA-1, SPP-1, or Ric, is encoded by the SPP1 gene in humans and is expressed predominantly in bone.The regulatory mechanisms of the OPN gene have not been fully elucidated and are different for different cell types.OPN has a role in biomineralization, bone remodeling, immune function, chemotaxis, cell activation, and apoptosis, and has been similarly implicated in cardiomyocyte Apoptosis and increased myocardial dysfunction.OPN is associated with many physiological and pathological processes including wound healing, bone conversion, tumorigenesis, inflammation, ischemia, and immune response. Modulation of plasma (or local) OPN levels has been useful in the treatment of autoimmune diseases, cancer metastasis, bone and tooth mineralization, osteoporosis, and some forms of stress.