Proteoglycans and Their Role in Wound Repair

Proteoglycans are a heterogeneous group of protein-carbohydrate complexes that are distinguished from all other macromolecules by bearing glycosaminoglycan (GAG) chains. These linear polysaccharide chains are highly polyanionic (due to sulfate and carboxylate residues), bear the highest charge density of any vertebrate macro-molecule, and usually occupy a high proportion of the mass of the proteoglycans. The distinction is important because these properties differ from all other molecules in vertebrate tissues. Because of their chemical stability, the GAG chains have been known and well characterized for many years. Only relatively recently, with the identification of a large number of proteoglycan core proteins, have their roles in cellular behavior become apparent. The GAG chains play a primordial role in metazoans; they are produced by the simplest organisms and are synthesized very early during vertebrate development and by virtually every nucleated cell. While they have multiple potential functions, the explicit role of each GAG type depends both on its nature and on the core protein moiety to which the GAG chain is linked in a proteoglycan.