Immunohistochemical expression and distribution of proteoglycans and collagens in sclerocornea

Abstract

To immunolocalize corneal keratan sulfate (KS) and its core protein lumican, aggrecan, type I and type III collagens in sclerocornea specimens and compare their expression and distribution to age-matched healthy corneas and scleras. Sclerocornea specimens (n = 3) and age-matched normal corneoscleral rim specimens (n = 3) were studied by light microscopy and histochemically. KS, lumican, aggrecan, type I and type III collagens were immunolocalized in the specimens using indirect immunofluorescence. The fluorescence intensity in each specimen was scored from 0 to 4, with 0 representing no fluorescence and 4 representing intense fluorescence. The sclerocornea specimens showed histologic features typical of sclerocornea. KS and lumican immunolabeling in the corneal stroma in sclerocornea was decreased, whereas aggrecan immunolabeling was increased compared to that seen in normal cornea and normal sclera. KS and lumican staining was more intense in the posterior part of sclerocornea specimens, whereas aggrecan staining was distributed throughout the stroma. The staining intensity and distribution of type I collagen in sclerocornea was similar to that seen in normal cornea. Type III collagen was faint to absent in both normal cornea and sclerocornea but strong labeling was noted in normal sclera. The immunophenotype of sclerocornea is similar to that of normal cornea but with reduced labeling intensity of KS and lumican and increased labeling intensity of aggrecan. This change could potentially contribute to the abnormal fibril assembly in sclerocornea.

Distribution and Function of Glycosaminoglycans and Proteoglycans in the Development, Homeostasis and Pathology of the Ocular Surface

“…Specifically, a thin line of KS (represented in red) can be seen lining the outer surfaces of the stromal lamellae ( Figure 3 ). In adult mouse corneas, immunohistochemistry shows an increasing concentration of lumican from low levels of non-specific staining in the epithelium to markedly increased levels in the posterior third of the stroma ( Figure 4 ) ( Chakravarti et al, 2000 ; Bouhenni et al, 2013 ). Studies in chick corneal development have shown that the switch from the glycoprotein form of lumican (containing polylactosamine – non-sulfated KS) side chains, at embryonic day 7 (E7) to the PG form of lumican (with sulfated KS side chains) after E15 is well correlated with development of corneal transparency ( Cornuet et al, 1994 ; Dunlevy et al, 2000 ).…”

Pathological and Immunohistochemical Alterations of the Cornea in Congenital Corneal Opacification Secondary to Primary Congenital Glaucoma and Peters Anomaly

“…A decrease in keratan sulfate labeling has been reported for other congenital corneal disorders such as sclerocornea and in the posterior stroma of lumican deficient mice. 11,12,14 Smooth muscle actin is a marker of myofibroblasts and its presence indicates an active healing process. 15 The increased level of smooth muscle actin in Peters anomalyrelated scars in comparison with acquired scars may indicate that the myofibroblastic changes in the keratocytes in Peters anomaly are similar to what is noted in acquired corneal stromal scarring.…”

A method to preserve limbus during penetrating keratoplasty for a case of presumed PHACES syndrome with sclerocornea

“…The lumican content in the scleralized cornea is reduced, while that of aggrecan is increased. [ 12 ]…”