Cellular Changes in Cultured Lenses

Observations were made on the frog lens epithelium after culture of the entire lens or of capsular explants. General deviations from normal lens structure as well as specific changes in two media were studied. DNA synthesis and mitosis were induced in the central epithelial cells. Disruption of the orderly, single, epithelial layer that is characteristic of normal lenses was accompanied by the appearance of multilayered plaques of epithelial cells and invasion of vacuolated regions of the lens fibers by epithelial cells. Cells that are fibroblast-like in appearance were observed in regions of the capsule depleted of cells and at the free edges of epithelial sheets in cell culture. Epithelial cells were surrounded by capsule-like material even when situated in the lens interior. Nuclei derived from central epithelial cells of lenses cultured in L-15 medium and medium 199 had served as donors in previous nuclear transfer experiments in this laboratory. In our current observation of L-15-cultured lenses, cells were sparsely distributed on the capsule and nuclei were abnormally shaped; in 199-cultured lenses, cells were more densely distributed and nuclei resembled those of normal lenses. Medium 199 without serum could better maintain normal lens structure than L-15 medium without serum. In addition, the percentage of epithelial explants demonstrating cellular outgrowth was greater in medium 199. The differences in cellular behavior were shown not to be the result of different sugars, pH, or the presence of CO₂. The nuclear transfer results may reflect the structural changes in the epithelium after lens culture in the two media.