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. Monomer. Interacts with TGFB1. Specifically expressed in cartilage. Localizes in the intermediates layer of articular cartilage but neither in the superficial nor in the deepest regions. Specifically and highly expressed in intervertebral disk tissue. Expression increases with aging in hip articular cartilage. Overexpressed in articular hyaline cartilage from patients with calcium pyrophosphate dihydrate crystal deposition disease (CPPD). Expression in intervertebral disk tissue from individuals with lumbar disk disease increases as disk degeneration progresses. Cleaved into 2 chains possibly by a furin-like protease upon or preceding secretion. Disease susceptibility is associated with variants affecting the gene represented in this entry. Antibodies against CILP are detected in patients with early-stage knee osteoarthritis and rheumatoid arthritis. Was originally thought to constitute the ATP pyrophosphatase enzyme (NTPPH). However, it was later shown (PubMed:12746903 and PubMed:15864306) that it is not the case.