Increased extracellular deposition of fibrillin-containing fibrils in pseudoexfoliation syndrome.

PURPOSE To localize the distribution of fibrillin-containing microfibrils in normal human anterior segment tissues and to characterize the role of fibrillin in the pathogenesis of pseudoexfoliation syndrome. METHODS Anterior segment tissues were obtained from 10 eyes with pseudoexfoliation syndrome and 10 normal eyes and investigated by indirect immunofluorescence and electron microscopic immunogold labeling using a monoclonal antibody to fibrillin-1. RESULTS In addition to labeling of zonular fibers, fibrillin-immunoreactive microfibrillar bundles generally were found in the corneal stroma; the stromal connective tissues of conjunctiva, ciliary body, and iris, especially in the iris root area; the periphery of Schlemm's canal, the scleral spur, and the most anterior portion of the trabecular meshwork; the ciliary muscle, and the dilator and sphincter muscles of the iris; the basement membranes of peripheral corneal epithelium, conjunctival epithelium, ciliary pigmented epithelium, and the lens capsule. The microfibrillar bundles were found to be isolated or in association with elastic fibers and cellular basement membranes. In pseudoexfoliation eyes, an additional strong immunoreaction was localized to pseudoexfoliation fibers and their microfibrillar subunits in close proximity to surfaces of cells involved in pseudoexfoliation fiber production. CONCLUSIONS The fibrillin-containing microfibrillar system in normal ocular tissues is suggested to have a substantial role in the maintenance of tissue integrity by providing tensile strength and flexibility to mechanically strained tissues. The findings further provide evidence for fibrillin as an intrinsic component of pseudoexfoliation fibers, suggesting the possibility that enhanced expression of fibrillin or abnormal aggregation of fibrillin-containing microfibrils may be involved in the pathogenesis of pseudoexfoliation syndrome.