ABSTRACT
Osteopontin (OPN) is phosphorylated sialic acid –rich non-collagenous bone matrix protein. OPN is found in several biological fluids including human plasma, serum, breast milk and urine.OPN was named for its function as a bridge between cells and minerals. OPN has been implicated as an important factor in bone remodeling. Osteopontin is expressed in immune cells, including macrophages, neutrophils, dendritic cells with varying kinetics. OPN influences cell mediated immunity and has Th 1 cytokine functions .OPN is overexpressed in cancers of lung, breast, colorectal, stomach and ovary.OPN is found in atheromatous plaques within arteries. OPN plays an important role during both acute and chronic inflammation. OPN is upregulated in tissues during several pathological process including atherosclerosis, valve stenosis, myocardial infarction and rheumatic arthritis. OPN is a key cytokine regulating tissue repair. OPN’s plasma levels are elevated in overweight and obesity.