Descemet's membrane, the specialised basement membrane of the corneal endothelium, contains a form of extracellular matrix described as wide-spaced
collagen. In healthy human Descemet's membrane, wide-spaced
collagen forms a highly ordered array in a region called the anterior banded zone. However, in corneal endotheliopathies such as
Fuchs' endothelial dystrophy and the
iridocorneal-endothelial syndrome large amounts of wide-spaced
collagen are deposited posterior to Descemet's membrane in a grotesque parody of the anterior banded zone termed a posterior collagenous layer. The purpose of this study was to identify the composition of the wide-spaced
collagen found in the Descemet's membrane of normal and diseased human corneas. Tissue from three normal human corneas, three from patients with
Fuchs' endothelial dystrophy and five from patients with the
iridocorneal-endothelial syndrome was prepared for immuno-electron microscopy by freezing or embedding in
Lowicryl K4M resin. Immunocytochemistry on ultrathin sections was performed with
antibodies to
collagen Types I, III, V, VI and VIII,
fibronectin,
laminin, P component and
tenascin. Ultrastructural labelling of the wide-spaced
collagen in the anterior banded zone of normal and diseased corneas and also of the wide-spaced
collagen in the posterior collagenous layer of all the diseased corneas was demonstrated with antibody to
collagen Type VIII. Wide-spaced
collagen was not labelled by any of the other
antibodies used. Large amounts of
Type VIII collagen are present in discrete regions of healthy and diseased Descemet's membrane. The deposition of
Type VIII collagen may significantly influence the pathobiology of the corneal endotheliopathies.