Expression of type XII collagen and hemidesmosome-associated proteins in keratoconus corneas

Purpose. Keratoconus. is a disease characterized by thinning of the central and paracentral cornea and scarring in advanced cases. This study was perf ormed to examine the expression of type XII collagen, proteins associated w ith hemidesmosomes, and beta1 integrin in keratoconus corneas. Methods. Corneal buttons were collected from normal subjects and patients w ith keratoconus and other corneal diseases. Immunofluorescence staining was performed on frozen sections for type XII collagen, bullous pemphigoid ant igen (BP180), and integrin subunits alpha6, beta4, and beta1. Results. To varying degrees, all proteins examined were expressed in normal human corneas. The staining intensity of type XII collagen was diminished in keratoconus corneas in the epithelial basement membrane zone and the str omal matrix. No significant variation was found in either the staining patt erns or intensities for BP180, or integrins alpha6, beta4, and beta1. Conclusions. The level of type XII collagen was reduced in the epithelial b asement membrane zone and stromal matrices in keratoconus corneas. These al terations may affect critical interactions of the corneal epithelium with t he underlying basement membrane, and cell-matrix interactions and matrix or ganization in the stroma.