Morphology of transplanted corneal endothelium derived from tissue culture

Rabbit corneal endothelial cells grown in vitro on glutaraldehyde-fixed gelatin membranes were examined by light and electron microscopy both before and after use as donor material in corneal endothelial transplants with autologous stroma and epithelium. The cultured cells had many of the morphologic characteristics of normal native endothelium, including polygonal cell shape stainable with silver nitrate, typical apical and lateral junctional complexes, terminal web, and cytoplasm dominated with profiles of granular endoplasmic reticulum and mitochondria. However, several distinct structural dissimilarities were also noted. These included intracellular accumulation of autophagocytic vacuoles and residual bodies, frequent pronounced swelling of intercellular spaces with retention of junctional complexes, excessive overlapping of cytoplasmic processes from 2 to 4 cells over long distances, and absence of normal cellular interdigitation. In contrast, the grafting of endothelial cell cultures into rabbit corneas resulted in clearing of residual bodies, appearance of normal intercellular spacing, elimination of abnormal cell overlapping, acquisition of complex basal and lateral cell interdigitation, and production of new, normal Descemet's membrane. The transplanted cells were morphologically indistinguishable from their native counterparts, except for the retention of the gelatin membrane, which showed no signs of degeneration. The reacquisition of normal cell morphology coincided with the re-establishment of normal endothelial cell function in the transplants. It was concluded that cultured endothelial cells possess the principal structural attributes of native endothelium but that their intercellular associations are incompletely developed.