Proteoglycans of the Intervertebral Disc

This chapter discusses the properties of hyaline cartilage proteoglycans and summarizes the proteoglycans of the disc. Proteoglycans and collagens constitute the two major classes of macromolecules in the nucleus pulposus, annulus fibrosus, and hyaline lamina of the intervertebral disc. The proteoglycan gel of the nucleus must play a key role in the communication mechanisms. The proteoglycans are therefore a subclass of glycoprotein distinguished by the presence of one or more glycosaminoglycan chains. The phenomenon of heterogeneity in proteoglycans is discussed again later in relation to the intervertebral disc. Histology of cat, dog, horse, ox, sheep, and pig intervertebral disc revealed an abundant sulfated glycosaminoglycan in the extracellular matrix of the nucleus pulposus, with a tendency towards heavier staining in the center of the tissue. Proteins that bind to glycosaminoglycan chains in the disc could also influence the water content of the tissue.