Epithelial mesenchymal transition in human ocular chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) of the ocular surface and lacrimal gland is a vision-threatening condition that occurs after allogeneic bone marrow transplantation. In this study, we used immunohistochemistry and electron microscopy to investigate whether epithelial mesenchymal transition (EMT) contributed to the pathogenesis of ocular cGVHD. We detected down-regulation of E-cadherin and translocation of β-catenin from the intercellular junction to the cytoplasm and nucleus of cGVHD conjunctival basal epithelia and lacrimal gland myoepithelia. Notable findings included expression of Snail, an inducer of EMT, in the nucleus of ocular cGVHD epithelia. The fibrosis markers heat shock protein 47, α-smooth muscle actin, and fibroblast specific protein-1 were overexpressed in ocular cGVHD epithelia. In addition, p63, a marker of conjunctival basal epithelia, was observed in the nuclei of subconjunctival cells beneath disrupted basal lamina. Disrupted basal lamina and the presence of altered collagen bundles were observed in the cytoplasm and beneath cGVHD epithelia. In contrast, these observations were rarely observed in the normal conjunctiva and in Sjögren's syndrome lacrimal gland epithelia. These findings together indicate that ocular cGVHD epithelia gain the mesenchymal phenotype and the capacity to migrate into the subepithelial stroma. Our findings suggest that EMT may be partially responsible for the conjunctival and lacrimal gland fibrosis found in patients with cGVHD.