Pig vitreous gel: macromolecular composition with particular reference to hyaluronan-binding proteoglycans

Abstract

The aim of this study was to examine the macromolecular composition of pig vitreous body with particular emphasis on hyaluronan-binding proteoglycans. The whole pig vitreous gel was found to contain 76 μg of hyaluronan-derived uronic acid, 700 μg of total protein and 150 μg of collagen per ml of gel. The contents of neutral hexoses and sialic acids were 80 and 22 μg/ml of vitreous gel, but only a minor proportion of them were found to be associated with the proteoglycan fraction. As estimated by gel chromatography on Sepharose CL-2B, hyaluronan presents a polydisperse hydrodynamic behavior with a lower molecular mass ( M r) value of 220 kDa. The existence of low amounts of a hyaluronan-binding proteoglycan population with structural and immunological characteristics similar to a member of the hyalectan family, versican, has also been demonstrated. The concentration of this versican-like proteoglycan in whole vitreous accounts for 50 μg proteoglycan protein per ml of vitreous gel and represents a minor proportion (about 7%) of the total protein content. The proteoglycan has an average M r of 360 kDa and is substituted by chondroitin sulphate (CS) side chains. Study of the CS sulphation pattern showed that the chains were composed of both type 4- and 6-sulphated disaccharide units.