Involved in endochondral bone formation as negative regulator of bone mineralization. Stimulates the proliferation of endothelial cells and promotes angiogenesis. Inhibits MMP9 proteolytic activity (By similarity). Interacts (via C-terminus) with HSPG2 (via C-terminus). Interacts with EFEMP1/FBLN3 and LAMB3. Interacts with MMP9. Expressed in the connective tissues surronding developing long bones, but not in the cartilage. The long isoform is expressed in a number of tissues including liver, heart and lungs. The short isoform is expressed in skin and cartilage-containing tissues such as tail and front paw. No expression is found in brain.