Glycosaminoglycans are large complex carbohydrate molecules that interact with a wide range of proteins involved in physiological and pathological processes. Glycosaminoglycans are sometimes known as mucopolysaccharides because of their viscous, lubricating properties, as found in mucous secretions. These molecules are present on all animal cell surfaces in the extracellular matrix, and some are known to bind and regulate a number of distinct proteins, including chemokines, cytokines, growth factors, morphogens, enzymes and adhesion molecules.