Probably plays a role in cartilage scaffolding. May act by antagonizing TGF-beta1 (TGFB1) and IGF1 functions. Has the ability to suppress IGF1-induced proliferation and sulfated proteoglycan synthesis, and inhibits ligand-induced IGF1R autophosphorylation. May inhibit TGFB1-mediated induction of cartilage matrix genes via its interaction with TGFB1. Overexpression may lead to impair chondrocyte growth and matrix repair and indirectly promote inorganic pyrophosphate (PPi) supersaturation in aging and osteoarthritis cartilage (By similarity). Monomer. Interacts with TGFB1 (By similarity). Specifically expressed in cartilage. Expressed at lower level in young cartilage than in adult cartilage. In adult cartilage, it is highly expressed throughout middeep zones. Up-regulated upon TGFB1 treatment, and down-regulated by IGF1. Cleaved into 2 chains possibly by a furin-like protease upon or preceding secretion. Was originally (PubMed:9332376 and PubMed:7860751) thought to constitute the ATP pyrophosphatase enzyme (NTPPH). However, it was later shown that it is probably not the case.