Immunohistochemical localization of basement membrane components in pseudoexfoliation material of the lens capsule.

The pseudoexfoliation (PSX) syndrome has long been speculated to be a disorder of disturbed basement membrane metabolism. To test this concept, we investigated the presence of all principal basement membrane components in precapsular PSX deposits of 30 anterior lens capsules by immunofluorescence and electron microscopic immunogold techniques. We have shown heparan sulfate and chondroitin sulfate proteoglycans, laminin, entactin/nidogen, fibronectin, and amyloid P protein to be an integral constituent of PSX material; type IV collagen was restricted to a microfibrillar layer interposed between capsular surface and typical PSX material. The additional presence of elastin epitopes indicates that the PSX material is a multicomponent expression of a disordered extracellular matrix synthesis including the incorporation of the principal noncollagenous basement membrane components. The extensive labelling of PSX material for chondroitin sulfate suggests an overproduction and abnormal metabolism of glycosaminoglycans to be one of the key changes in this disorder.