Glycosaminoglycan and collagen distribution in the developing human vitreous

Background: We determined the distribution of glycosaminoglycans and collagens in the developing human vitreous. Methods: Eighty human eyes from 5 gestational weeks to 2 postnatal years of age were used. Glycosaminoglycan components were determined by enzyme digestion with hyaluronidase or chondroitinase AC and ABC and immunohistochemistry for chondroitin, chondroitin-4-sulfate, chondroitin-6-sulfate, and dermatan sulfate. Collagen distribution was determined by immunohistochemistry for types I, II, and III collagens. a Results: Enzyme digestion showed that throughout development hyaluronic acid is the main glycosaminoglycan in the vitreous and in the extraocular space at 5-7 gestational weeks. Both areas were filled with mesenchymal cells. Immunohistochemistry showed chondroitin-6-sulfate in the vitreous between 6 and 40 gestational weeks, and chondroitin-4-sulfate between 12 and 40 gestational weeks. Hyaluronic acid and chondroitin sulfate appeared in the retina and around the hyaloid vessels at 12-40 weeks. Immunohistochemistry showed type III collagen in the vitreous and around the mesenchymal cells at 5-7 weeks that was replaced by type II collagen after 8 weeks. Conclusions: Hyaluronic acid is the major glycosaminoglycan in the vitreous throughout development, except for the transient appearance of chondroitin sulfate at 6-40 gestational weeks. Type III is the main collagen in the early developing vitreous that converts to type II collagen at 8 weeks. The primary and secondary vitreous has the same components as these macromolecules. These vitreous glycosaminoglycans and collagens seem to be produced by mesenchymal cells at an early stage and by the retina and hyaloid vessels during middle and late development.