Alterations of epithelial adhesion molecules and basement membrane components in lattice corneal dystrophy (LCD)

The aim of the study was to investigate the histopathological and ultrastructural correlate of delayed epithelial healing in eyes with lattice corneal dystrophy (LCD).

Corneal buttons from 4 patients with LCD (two with subepithelial, two with stromal amyloid deposits) and 2 control corneas were examined. Cell-matrix adhesion molecules and basement membrane components of the corneal epithelium were analyzed by immunohistochemistry and hemidesmosomes between epithelium and stroma were quantified by transmission electron microscopy (TEM).

By TEM well-developed hemidesmosomes anchored the basal epithelial cells to the underlying basement membrane in all normal and LCD corneas. Hemidesmosome density was not significantly different in subepithelial (224.7 ± 34.1/100 µm) and stromal (234.3 ± 36.3/100 µm) LCD compared to controls (241.3 ± 26.8/100 µm). The basement membrane was interrupted in subepithelial, but continous in stromal LCD. Integrin α6 and ß4 staining formed a continous line along the basal surface of the corneal epithelium in control corneas, whereas it appeared discontinous and patchy both in subepithelial and stromal forms of LCD. Staining for αV integrin showed irregular staining patterns, i.e. enhanced labelling intensity in subepithelial and interrupted pattern in stromal LCD, respectively. Integrins α3, ß1, ß2, and ß5, dystroglycan, and plectin were not markedly different in dystrophic corneas. Type VII collagen showed a discontinuous staining in subepithelial forms of LCD. In stromal forms of LCD, type VII collagen staining occurred in additional patches underneath the epithelial basement membrane zone. Type XVII collagen staining was reduced in subepithelial LCD. Laminin-1, laminin-5 and laminin γ2 showed variable irregular staining patterns in dystrophic corneas with focal interruptions, focal thickenings, and reduplications of basement membrane. Some irregularities in corneas with subepithelial amyloid were observed for collagen types IV, V, and XVIII, laminin α1, α3, and γ1, nidogen-1 and -2, perlecan, fibrillin-1.

Immunohistochemical and electron microscopic evidence of structural alterations was found in LCD compared to normal corneas concerning cell-matrix adhesion molecules and basement membrane components. These alterations were more pronounced in dystrophic corneas with subepithelial amyloid deposits than in those with stromal deposits. Histopathological findings may correspond to reduced cell-matrix interactions and partly explain delayed epithelial healing in patients with lattice corneal dystrophy.