THE CHEMICAL MORPHOLOGY OF THE VITREOUS

The water of the vitreous is stabilised by an ordered meshwork of very fine collagen fibrils that are tied together in loosely parallel bundles or sprays by bridges of sulphated glycosaminoglycan. Some fibril bundles run at right angles to other bundles. In these respects vitreous resembles a very dilute corneal stroma. The glycosaminoglycans of the vitreous (hyaluronan and chondroitin sulphate) aggregate with themselves and with each other in solution. The protein cores of the proteoglycans are attached to collagen fibrils. Thus, a three-component cross-linked structure is formed: collagen fibril --> proteoglycan protein core --> glycosaminoglycan chain --> glycosaminoglycan chain --> protein core --> collagen fibril. Hyaluronan can aggregate directly with chondroitin-6-sulphate, or with aggregated glycan cross-links, thus entering into an infinite meshwork.