Transendothelial electrical resistance of bovine retinal capillary endothelial cells is influenced by cell growth patterns: an ultrastructural study.

The purpose of this study was to describe the ultrastructural features of an in vitro capillary endothelial cell model of blood-retinal barrier permeability and to relate morphological features with transendothelial electrical resistance. The electrical resistance of endothelial cell monocultures on small and large pore size polycarbonate Transwell filters was measured and compared with cocultures of endothelial cells and Müller cells. There was a wide variation in electrical resistance measurements with many preparations not achieving a functional barrier. The ultrastructural features associated with barrier function in vitro were studied by comparing cultures that exhibited a 'tight' or 'leaky' barrier when measured immediately prior to processing for electron microscopy. Preparations with low transendothelial electrical resistance were associated with irregular cell growth when studied morphologically. It was concluded that parallel light and electron microscopic studies are important for validation of in vitro models of vascular endothelial permeability.