Histochemical study on glycosaminoglycans in the developing mouse vitreous

The distribution of polyanionic glycosaminoglycans (GAGs) in the developing mouse vitreous was studied histologically by P.A.S. reaction, metachromatic staining by toluidin blue at various pH's, alcian blue at pH 0.5 and alcian blue at various pH's, alcian blue at pH 0.5 and alcian blue C.E.C. stainings, modified Hale's method with colloidal iron, and enzymatically with bovine testicular hyaluronidase. A subdivision of the vitreous developmental period into four phases and an early distinction between, the posterior and equatorial vitreous portions are suggested on basis of the results. The early vitreous, during the first developmental phase, exhibits a high content in GAGs. This property gradually vanishes in the posterior part during the second phase of development, while acid GAGs including possibly hyaluronate are present in the equatorial zone. During this second phase, the lens capsule present a strong P.A.S.-reactivity, especially positive in it's posterior part. During the third phase, sulphated GAGs reappear in the posterior vitreous while non-sulphated material remains present in the equatorial zone. During the first two postnatal weeks (fourth developmental phase), acid GAG's disappear in the equatorial part of the vitreous but the maturing zonular fibres display the properties of sulphated GAGs. It is suggested that the histochemical maturation of the secondary vitreous starts around the 16th or 17th fetal day, i.e. much earlier than its morphological differentiation.