FIGURE 1.

Primary RPE cells have a terminal differentiation phenotype on Transwell filters. Primary RPE cells were cultured on Transwell filters, and their phenotype was evaluated by TEM, TER and tight junction protein ICC. (A) RPE cells grew in a single monolayer with apical microvilli (black arrowhead), melanosomes, basal nuclei (asterisks), and membrane infoldings. (B) Magnification of the indicated area in A shows RPE cells with clearly visible tight junctions (red arrowhead) and melanosomes (white arrowhead). (C) Barrier function was assessed by quantifying TER over time. After four weeks, the TER plateaued at ∼1,400 Ω cm². (D) ZO-1 immunoreactivity was continuous along the cell borders.