Aberrant Patterns of Key Epithelial Basement Membrane Components in Keratoconus

Purpose: In the cornea, the epithelial basement membrane (BM) plays an important role in maintaining corneal integrity and homeostasis. Aberrations in this vital structure are associated with several corneal pathologies including keratoconus. The aim of this study was to investigate the expression of key structural components of the epithelial BM in keratoconic corneas and to identify and describe any aberrant patterns. Methods: Immunohistochemical labeling of key BM components including fibronectin, laminin, and type IV and VII collagen was performed in healthy and keratoconic corneas. Results: Clear changes in the BM components in the keratoconic corneas were seen with the key structural components either being absent or forming a discontinuous pattern. Another aberrant pattern, the expression of BM proteins, particularly fibronectin, laminin, and type IV collagen, in the anterior stroma of keratoconic corneas was also observed. Conclusions: These results indicate the activation of keratocytes into the fibroblast and myofibroblast wound phenotypes and the potential source of corneal scarring commonly observed in keratoconic corneas. Our data also support the hypothesis of dysregulated collagen synthesis and breakdown in the keratoconic cornea, in particular, the BM, and suggest a role for the BM in initiation and progression of keratoconus.