High Quality Content by WIKIPEDIA articles! Osteopontin (OPN), also known as bone sialoprotein I (BSP-1 or BNSP), early T-lymphocyte activation (ETA-1), secreted phosphoprotein 1 (SPP1), 2ar and Rickettsia resistance (Ric), is a human gene product, which is also conserved in other species. Osteopontin is a SIBLING glycoprotein that was first identified in 1986 in osteoblasts.