proteoglycanrich

Proteoglycan-rich is a descriptor used for tissues or extracellular matrices that contain high levels of proteoglycans, a class of macromolecules composed of a core protein with sulfated glycosaminoglycan chains. Proteoglycans include aggrecan, decorin, versican, perlecan, and many others. The sulfated GAG chains, such as chondroitin sulfate, dermatan sulfate, keratan sulfate, and heparan sulfate, confer a highly negatively charged, hydrated network.

Functionally, these proteoglycans attract water and create a gel-like matrix that resists compressive forces and maintains tissue turgor. They modulate collagen fiber organization, influence tissue elasticity and porosity, and bind growth factors and cytokines, shaping cell signaling and matrix turnover. Proteoglycan-rich matrices also help regulate diffusion of molecules through the extracellular space and participate in cell–matrix interactions that influence development and repair.

Proteoglycan-rich matrices are characteristic of cartilage, the nucleus pulposus of intervertebral discs, and the vitreous body of the eye, among others. In cartilage, large aggregates of aggrecan bound to hyaluronic acid give the tissue its osmotic swelling pressure. Changes in proteoglycan content are a feature of aging and disease; loss of proteoglycans is associated with osteoarthritis, while altered synthesis occurs in mucopolysaccharidoses and certain tumors.

Studying proteoglycan-rich tissues uses histology with Alcian blue or Safranin O staining, immunohistochemistry for specific proteoglycans, and biochemical assays (for example, the dimethylmethylene blue assay) to quantify sulfated GAGs.