Exfoliative epitheliopathy of bullous keratopathy with breaches in the MUC16 Glycocalyx.

Abstract

Expression of cellular adhesion molecules is altered in bullous keratopathy. The hypothesis that epithelial alterations in bullous keratopathy compromise the surface of the cornea and its glycocalyx was tested. Studies were performed on eight cases each of pseudophakic bullous keratopathy and healthy corneas. The number of epithelial cell layers was determined with a stereological method of point counting. The minimum distance between points was established by estimates of cell size with variable pressure scanning electron microscopy performed in backscatter mode. The mean number of cell layers with mucin expression was identified by immunohistochemistry with mouse monoclonal antibodies for MUC1 and MUC16. Data were analyzed by Student's t-test if values showed a normal distribution or, alternatively, by the Wilcoxon rank-sum test. Mean numbers of wing cell and superficial cell layers were lower in bullous keratopathy specimens (1.6 vs. 2.0; P < 0.0001) than in controls (1.1 vs. 1.8; P < 0.000001). The number of exfoliated cell layers evident in sections was increased in the bullous keratopathy specimens compared with controls (0.36 vs. 0.03; P < 0.0001). The number of cell layers decorated with antibodies to MUC16 was lower in bullous keratopathy specimens than in controls (0.5 vs. 1.2; P < 0.025). The reduction of layers expressing MUC1 in bullous keratopathy was not statistically significant. Pseudophakic bullous keratopathy manifests an abnormal corneal ocular surface in which superficial cell layers are exfoliated, leaving breaches in the protective MUC16 glycocalyx. The results provide a morphologic correlate for the surface epithelial abnormalities noted clinically in these patients.