Occurrence and structural characterization of versican-like proteoglycan in human vitreous

Human vitreous gel is a special type of extracellular matrix, in which interpenetrating networks of collagen fibrils and hyaluronan are found. In this study, we report that apart from significant amounts of collagen, hyaluronan and sialylated glycoproteins, it was found that the human vitreous gel also contained low amounts of versican-like proteoglycan. The concentration of versican-like proteoglycan in the whole vitreous is 0.06 mg protein/ml of vitreous gel and represents a small percentage (about 5%) of the total protein content. The versican-like proteoglycan has a molecular mass of 380 kDa, as estimated by gel chromatography. Its core protein is substituted by chondroitin sulphate side chains (average molecular weight 37 kDa), in which 6-sulphated disaccharides predominated. According to the physicochemical data, the number of chondroitin sulphate chains is likely to be 5-7 per molecule. These proteoglycan monomers form large aggregates with endogenous hyaluronan. Versican, which is able to bind lectins via its C-terminal region, may bridge or interconnect various constituents of the extracellular matrix via its terminal domains in order to stabilize large supramolecular complexes at the vitreous, contributing towards the integrity and specific properties of the tissue.