Decorin is a small leucine-rich proteoglycan (SLRP) family member that consists of a glycosaminoglycan chain-containing core protein. The core protein contains ten leucine rich repeats that contain sites for glycosylation, flanked by disulfide bond stabilizing loops. Decorin binds to Collagen Type I, II and IV in vivo and promotes the formation of fibers with variations in stability and solubility. The Decorin core protein binds to growth factors, intercellular matrix molecules, such as Fibronectin and Thrombospondin, and to the Decorin endocytosis receptor. Decorin binds to and inhibits TGF尾 and is a direct or indirect negative modulator of TGF尾 synthesis. Inhibition of Decorin core protein gene expression by the combination of IFN-纬 and TNF伪 may contribute to cartilage destruction that is characteristic of inflammatory joint diseases. For immunostaining, pre-incubation with chondroitinase-SBC or testicular hyaluronidase may be required to expose the epitope.