Cartilage Staining Kit (Chondrocyte and Cartilage Tissue Staining Kit) can be used to easily detect aggrecan and type II collagen in cartilage. This kit contains an Anti-Rat type II Collagen monoclonal Antibody to detect type II collagen of rat chondrocyte and cartilage tissue by immunostaining. It also includes three stains: Toluidine blue, Safranin-O and Fast Green. Toluidine blue and Safranin-O are cationic stains (basic dyes) that stain acidic proteoglycan present in cartilage tissues. Toluidine blue, also called metachromasia dye, shows subtle color changes depending on the tertiary structure of the sample. Cytoplasm stains light blue, nuclear region dark blue, and mast cells purple. Safranin-O, which binds to glucosaminoglucan and shows an orange color, is often used to stain articular cartilage. Fast green, the contrast stain of Safranin-O, is a sulfate-group containing acidic substrate, which binds strongly to the amino group on protein and thereby strongly stains the noncollagen sites.
The main constituents of articular cartilage include aggrecan and type II collagen, both of which are proteolyzed when cartilage degenerates. Aggrecan, the major proteoglycan in cartilage, is a macromolecule consisting of an approximately 210-kDa core protein bound to a large number of sulfated chondroitin-side chains and multiple sulfated keratin-side chains. The core protein also has a domain capable of binding to hyaluronate produced by synoviocytes.
Type II collagen is a fibrillary element responsible for maintaining the special mesh structure in healthy cartilage and forms the structure that takes into its pores water-retentive proteoglycan. Type II collagen, unlike types I and III, exhibits a foreign-body antigenicity. Anti-type II collagen antibody, once generated in the body, induces rheumatism or arthritis.
