Endothelial metaplasia in the iridocorneal endothelial syndrome

To test the hypothesis that the aberrant, cytokeratin-expressing cells that replace endothelium in the iridocorneal endothelial (ICE) syndrome are of endothelial origin. Corneas from four patients with Chandler's syndrome and three with essential iris atrophy were examined by two-color immunofluorescence for simultaneous expression of cytokeratins and two markers of endothelial lineage: vimentin and the antigen recognized by the antiendothelial monoclonal antibody 2B4.14.1. In six corneas, unequivocal endothelial staining for cytokeratins was present; in each of these, cells coexpressing cytokeratins and the two endothelial markers were clearly identifiable. In the remaining cornea, weak cytokeratin staining that colocalized with vimentin was present. These results lend strong support to the hypothesis that the "epithelial-like" endothelial cells in ICE syndrome are cells of endothelial lineage rather than heterotopia of epithelial cells; these cells probably arise via a metaplastic transformation of preexisting endothelium.