Remodeling Processes in Keratoconic Epithelium

Abstract

Purpose: The occurrence of keratoconus pathology is related to the expression of several enzimes that alters the extracellular matrix. The onset of this matrix deformation remains unclear. The aim of this work is to study the cellular changes in keratoconic corneas by immunohistochemical analysis.

Methods: Five keratoconic corneas obtained from patients who were submitted for keratoplasty were characterized by Hematoxylin-eosin and Periodic acid of Schiff staining and by immunohistochemistry techniques to demonstrate Ki67, E-cadherin, β-catenin, laminin and metalloproteinases 9 and 24. Two independent researchers analyzed the samples.

Results: Light microscopy evaluation reveals epithelial thinning at the site of the keratoconic ectasia surrounded by hyperplasic epithelium in the periphery. We found points of breakdown on the Bowman membrane with disorientation of underlying stroma and an increase of keratocyte density. Stromal thinning at the site of the ectasia was also observed in all conreas. The expression of β-catenin, which is critical in cell adherens junctions, was detected by immunohistochemical means in cell membrane in all epithelial cells in normal corneas. This pattern was coincident with the location of E-cadherin antibody. In the atrophic region of the keratoconic epithelium, β-catenin was absent and was detected only in the nucleus, demonstrating nuclear translocation and pointing to Wnt/β-catenin signaling activation. These cells were actively proliferating, as indicated by Ki67 staining. The absence of junction proteins in the epithelium was coincident with the presence of MMPs markers. MMP-9 immunostaining was increased along the epithelium, with numerous positive cells around the ectasia. MMP-24 marker was detected at ectasia areas of the epithelium and near the breakdown figures of the Bowmann membrane and disruption of laminin deposition.

Conclusions: Proliferation and remodeling of the corneal epithelium and stroma in keratoconus is possibly promoted by activation of canonical Wnt/β-catenin signaling.

Keywords: 574 keratoconus • 482 cornea: epithelium • 484 cornea: stroma and keratocytes