Blue staining in connective tissue mucin is primarily due to which component that can be digested by hyaluronidase?

• A. Hyaluronic acid
• B. Type I collagen
• C. Elastin
• D. Fibrin

Answer: (A)

Blue staining of connective tissue mucin comes from acidic glycosaminoglycans in the ground substance. The component most responsible for this blue staining that can be digested by hyaluronidase is hyaluronic acid. Hyaluronic acid is a non-sulfated GAG that carries negative charges the dye binds to, producing the blue color with Alcian blue. When hyaluronidase acts, it cleaves hyaluronic acid, breaking down this mucopolysaccharide matrix and reducing or removing the blue stain.

The other options are structural proteins rather than glycosaminoglycans. Type I collagen, elastin, and fibrin do not form the acidic mucopolysaccharide component stained by Alcian blue, and they are not targeted by hyaluronidase in this staining context.