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J. J. Engle, O. K. Gasymov, R. Casey, B. J. Glasgow; Superficial Epitheliopathy in Pseudophakic Bullous Keratopathy Associated with Loss of Muc 16. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4623.
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Alterations in the expression of cellular adhesion molecules have been documented in bullous keratopathy. A morphologic and immunohistochemical study was performed to characterize the ocular surface of bullous keratopathy and to test whether there is alteration in the protective mucin coat in this disorder.
Studies were performed on 8 cases each of pseudophakic bullous keratopathy and normal corneas (controls). Corneas were removed carefully to avoid disruption of the central epithelium, fixed in 10% formalin, and processed and embedded together. Histologic sections were stained with hematoxylin and eosin. The number of epithelial cell layers was determined using a stereologic method of point counting and standard histologic criteria for cell types. Data were collected at random points in the epithelium created by intersecting lines separated by 100 microns in an ocular grid at a total magnification 312.5x. The minimum interval point counting for cases of bullous keratopathy was determined by estimates of cell size with variable pressure scanning electron microscopy (Leo 1430) performed in backscatter mode.Immunohistochemistry was performed by the peroxidase anti-peroxidase technique with mouse monoclonal antibodies, Muc 1 (Transgene Inc.) and Muc 16 (DAKO Inc.), at dilutions 1/4000 and 1:50 respectively. For each cornea 12 measurements were obtained of every parameter and means of the values were taken. Data were analysed by a student’s t test if values showed a normal distribution or alternatively by the Wilcoxon rank-sum test.
The mean number of wing cell and superficial cell layers were lower in bullous keratopathy compared to normals (1.6 versus 2.0, p<0.0001, p<0.000001 respectively). The number of exfoliated cell layers evident in sections were increased in the bullous keratopathy compared to controls (0.36 versus 0.03, p<0.0001). The number of cell layers decorated with antibodies to Muc16 was lower in bullous keratopathy than controls (0.51 versus 1.24, p<0.025). The number of basal cell layers and layers expressing Muc1 were not significantly different between cases of bullous keratopathy and controls (1 versus 1.02 and 1 versus 0.53, respectively).
Pseudophakic bullous keratopathy manifests an abnormal corneal ocular surface in which superficial cell layers and Muc 16 expressing cells are exfoliated. The findings are congruous with previous work showing abnormal cellular adhesion molecule expression in bullous keratopathy. The results provide a morphologic correlate for the surface epithelial abnormalities noted clinically in these patients.
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