Plays a role in boundary lubrication within articulating joints. Prevents protein deposition onto cartilage from synovial fluid by controlling adhesion-dependent synovial growth and inhibiting the adhesion of synovial cells to the cartilage surface.
Isoform F plays a role as a growth factor acting on the primitive cells of both hematopoietic and endothelial cell lineages.
Subcellular locations: Secreted
Highly expressed in synovial tissue, cartilage and liver and weakly in heart and lung. Isoform B is expressed in kidney, lung, liver, heart and brain. Isoform C and isoform D are widely expressed.