Histologic and immunohistochemical characterization of lens capsular plaques in dogs with cataracts

Objective-To determine histologic and immunohistochemical characteristics o f the multifocal adherent plaques that commonly develop on the internal sur faces of the anterior and posterior lens capsules in dogs with cataracts. Sample Population-31 anterior and 4 posterior capsular specimens collected during lens extraction surgery in dogs with cataracts. Procedure-Specimens were evaluated, using light and transmission electron m icroscopy. immunohistochemical techniques were used to localize cytokeratin , vimentin, alpha-smooth muscle-specific actin, fibronectin, tenascin, and transforming growth factor-beta (TGF-beta) within plaques. Results-Histologically, plaques comprised elongated spindle-shaped cells th at formed a placoid mass, Cells were embedded in an extracellular matrix co ntaining collagen fibrils, often with duplicated or split basement membrane s, Immunohistochemically, normal lens epithelial cells and cells within pla ques stained for vimentin. Most cells and some areas of the extracellular m atrix within plaques stained for TGF-beta and alpha-smooth muscle-specific actin. Fibronectin and tenascin were also detected in the extracellular mat rix. Conclusions and Clinical Relevance-Canine lens capsular plaques are histolo gically and immunohistochemically similar to posterior capsule opacificatio n and subcapsular cataracts in humans, which suggests that the canine condi tion, like the human conditions, is associated with fibrous metaplasia of l ens epithelial cells. Transforming growth factor-beta may play a role in th e genesis of capsular plaques. Because severity of plaques was correlated w ith stage of cataract development, earlier surgical removal of cataracts ma y be useful to avoid complications associated with plaque formation.