Cytokeratin Expression in Stromal Corneal Dystrophies and Normal Corneas

Abstract

Abstract: : Purpose: Granular, lattice and combined (Avellino) corneal dystrophies have generally been considered to be diseases of the stroma because in their late stages, the pathologic deposits are mostly found in the corneal stroma. Recently, some investigations have indicated an epithelial rather than a stromal origin of the deposits. These findings are based on their presence in both the upper microlayers of the cornea and epithelial layer in early stages or recurrence of the disease. In addition, the immunoreactivity for keratoepithelin protein (BIGH3 gene product) was later found in the dystrophic deposits. Cytokeratins (CKs) are the largest and most complex intermediate–sized filament class and are characteristic of epithelial cells. CKs 3 and 12 are cornea–specific although other CKs have been reported in the cornea. The aim of this study is to identify an immunohistochemical pattern of epithelial markers in corneal dystrophies such as granular, lattice and Avellino and compare those findings to normal corneas. Methods: Twenty–two corneal buttons, diagnosed as stromal dystrophies, were retrieved from The Henry C. Witelson Ocular Pathology Laboratory, McGill University, Canada. One case was diagnosed as granular, 17 lattice and 4 were combined dystrophies. All cases were previously examined with H&E, periodic acid–Schiff, Masson’s trichrome, Congo red, Alcian blue and colloidal iron stains. Immunohistochemical studies of various CKs were performed on paraffin–embedded sections of all cases. Monoclonal antibodies for pan–CK (AE1/AE3) and CKs 3/12, 5/6, 8, 18 and 19 were used. Twenty–two enucleated eyes with normal corneas were used as control. Results: In all cases, the epithelium of corneas with dystrophies and the controls showed a positive staining with anti–pan–CK (AE1/AE3) and CK 3/12. Of 8 positive cases, 7 (5 lattice, 2 combined) stained positively with anti–CK 3/12 in both the corneal epithelium and in the deposits (32%). The remaining case (lattice) was positive for anti–pan–CK (AE1/AE3) with the same pattern. Conclusions: The fact that the AE1/AE3 and CK 3/12 anti–CK markers were positive in the stromal deposits of lattice and combined dystrophies may suggest an epithelial nature of those corneal deposits.

Keywords: cornea: basic science • cornea: stroma and keratocytes • immunohistochemistry