Lens cell populations studied in human donor capsular bags with implanted intraocular lenses

PURPOSE. Posterior capsule opacification is an ongoing cellular redistribut ion process. The level of viable cell coverage was therefore determined in human donor capsular bags with implanted intraocular lenses, and cellular m orphology and ultrastructure were investigated in relation to cell type and level of differentiation. METHODS. Donor capsular bags, retrieved at intervals of 4 months to 13 year s after surgery, were investigated by phase optics before fixation. Postfix ation techniques included scanning electron microscopy and transmission ele ctron microscopy of sections and immunofluorescent staining of cytoskeletal proteins in wholemounts. RESULTS. All the capsular bags contained a large population of viable cells on the capsular surfaces. Cells on the anterior face of the anterior capsu le and in the spaces around the intraocular lens had an elongated morpholog y and expressed alpha-smooth muscle actin, The cells formed light-scatterin g, multilayered aggregates and strands that were surrounded by layers of ex tracellular matrix. The regions between the intraocular lens and the equato r of the bags were populated by monolayers of epithelial cells of normal mo rphology and ultrastructure, on both the anterior and posterior capsules. I n some regions the apical surfaces of the two epithelial monolayers were in contact, and in some parts of the equatorial regions, differentiation of c ells into well-organized fiberlike cells was evident. CONCLUSIONS. Human capsular bags contain a large population of viable cells for many years after cataract surgery. Cells in the regions around the int raocular lens undergo transition to a mesenchymal type. Cells peripheral to these regions can form a stable closed microenvironment in which both norm al epithelial morphology and differentiation to fiberlike cells are maintai ned.