Role of Proteoglycans in the Trabecular Meshwork
The extracellular matrix (ECM) of the trabecular meshwork/Schlemm's Canal pathway (TM/SC) consists of a complex arrangement of proteoglycans (PGs) arranged into a three-dimensional structure with ECM proteins and glycoproteins. The specific arrangement and composition of glycosaminoglycans (GAGs) on these proteoglycans in the ECM provides structural support and signaling cues for cell survival, growth factor signaling, cytoskeletal organization, cell adhesion, and contractility, as well as influences the ECM aqueous imbibing/retention characteristics and stiffness. The major classes of the PGs found in the TM/SC are cell-surface associated PGs (syndecans, glypicans, chondroitin sulfate proteoglycan-4, and betaglycan), pericellular/basement membrane PGs (perlecan, bamacan, and type XVIII collagen) and extracellular PGs (hyalectans [e.g. versican], small leucine-rich proteoglycans [SLRPs] and testicans). This review discusses recent findings about the biological and structural properties of these PGs and how they could contribute to the regulation of aqueous humor outflow through the trabecular meshwork.
