Laminins in normal, keratoconus, bullous keratopathy and scarred human corneas

The laminin composition (LM alpha 1-alpha 5, beta 1-beta 3, gamma 1 and gamma 2 chains) of normal corneas and corneal buttons from keratoconus, bullous keratopathy (BKP), Fuchs' dystrophy + BKP, Fuchs' dystrophy without BKP and scar after deep lamellar keratoplasty (DLKP) was investigated with immunohistochemistry. The epithelial basement membranes (BMs) of both normal and diseased corneas contained LM alpha 3, alpha 5, beta 1, beta 3, gamma 1 and gamma 2 chains. The epithelial BM morphology was altered in the different diseases. Scarring was associated with irregular BM and ectopic stromal localization of different laminin chains. The Descemet's membrane (DM) contained LM alpha 5, beta 1 and gamma 1 chains in all cases and additionally LM beta 3 and gamma 2 chains in the majority of keratoconus corneas. The interface in the DLKP cornea had patches of LM alpha 3, alpha 4, alpha 5, beta 1 and beta 2 chains, and an extra BM-like structure under the Bowman's membrane. These results suggest that laminin chains participate in the process of corneal scarring and in the pathogenesis of some corneal diseases. The novel finding of LM alpha 3, beta 3 and gamma 2 in the DM of keratoconus buttons indicates that this membrane is also involved in the disease and that some cases of keratoconus may have a congenital origin, without normal downregulation of the LM beta 3 chain.