Behavior of human RPE cultured on Bruch's membrane and on necrotic debris

Degeneration and necrosis of the retinal pigment epithelium (RPE) is found in several conditions associated with reactive alteration of the cell layer, and is probably involved in the formation of drusen and age-related macular degeneration. In the current study we describe a novel system for culturing human RPE. This system permits evaluation of the effect of necrotic material between the epithelium and Bruch's membrane, of drusen, and of other alterations in Bruch's membrane on the behavior of the RPE. In this system, dissociated RPE cells were seeded onto isolated Bruch's membrane. Cell behavior was assessed in areas with and without drusen, and also in areas covered with necrotic cells and fragmented debris. On both exposed Bruch's membrane and on the membrane covered with debris, the cells developed a polygonal shape, with a varying density of apical microvilli. The cultures were monolayered with some overlapping. In areas containing fragmented debris and dead cells, seeded RPE cells were found to adhere to the apical surface of necrotic cells, but were also seen to intrude between the necrotic debris and underlying Bruch's membrane, appearing to clear the membrane of such debris. Our study demonstrates the stability of epithelial histology of human RPE under not previously tested conditions. Further, it shows that the present system permits exposure of these cells to several in vivo physiological and pathological changes in a controlled in vitro environment.