Which is the main glycosaminoglycan in the vitreous?

• A. Hyaluronic acid
• B. Chondroitin sulfate
• C. Heparan sulfate
• D. Keratan sulfate

Answer: (A)

The vitreous gel is built mainly from a non-sulfated, very long glycosaminoglycan that tightly binds water and networks with collagen to create a clear, viscoelastic matrix. This GAG, hyaluronic acid, provides the high water content and gel-like consistency essential for the vitreous. Its large, unsulfated structure allows it to trap and retain water, forming a transparent, slippery gel that supports the retina and preserves optical clarity.

The other GAGs listed are sulfated and are more characteristic of other tissues: chondroitin sulfate is common in cartilage proteoglycans, keratan sulfate is prominent in cornea and cartilage, and heparan sulfate is a major component of basement membranes. They don’t form the primary hydrated network of the vitreous like hyaluronic acid does.