Studies on Morphology and Cytoskeletal Organization of Retinal Pigment Epithelial Cells in Migration in vitro

Earlier studies on proliferative vitreoretinopathy （PVR） have shown that prolifera-tion and migration of retinal pigment epithelial cells （RPE） are responsible for the pathogenesis of PVR. In this study, we examined the cell morphology and migratory activity of cultured RPE with special reference to the cytoskeletal organization. After 7 days in culture, porcine RPE at the cen-ter of colonies displayed hexagonal configuration with close cell-cell contact. Confocal laser scan-ning microscopy （LSM） revealed that these cells were 10-20 μm in height with a hexagonal columnar configuration. They migrated and transformed into spindle shapes at the edges of a linear wound, suggesting that epithelial-mesenchymal transition of RPE takes place in association with in vitro wound healing. The RPE in well-differentiated columnar configuration displayed prominent apical circumferential microfilament bundles （CMBs） along the plasma membrane and thick microfilament bundles （stress fibers） at the base. Longitudinal microtubule bundles along the apical-basal axis of the columnar cells were also clearly demonstrated by LSM. On the other hand, the RPE of elongat-ed spindle shape at the edges of the wound and those in the colonies lacked CMBs and longitudinal microtubules, but had prominent stress fibers. Vimentin-containing intermediate filaments were ob-served at the leading margins of the migrating RPE. These results indicate that RPE turn into mesenchyme-like cells in response to a focal wound in vitro and that the cytoskeleton dramatically changes in association with the changes in cell morphology and motility of RPE.departmental bulletin pape