Decorin, also known as DCN, is a small leucine-rich proteoglycan (SLRP) that plays a multifaceted role in the extracellular matrix (ECM) and various biological processes. Decorin is involved in a range of cellular processes including collagen fibrillogenesis, wound repair, angiogenesis, tumor growth, and autophagy. It interacts with various ligands such as ECM constituents, cellular receptors, growth factors, proteases, and other signaling molecules. Decorin has been shown to play a role in immune regulation. It can initiate aseptic inflammation and activate innate immune cells, making it relevant in autoimmune and inflammatory diseases. It can participate in the activation of innate immune cells through interaction with Toll-like receptors (TLRs) or other receptors.