Differentiation of rat lens epithelial cells in tissue culture. (I) Effects of cell density, medium and embryonic age of initial culture.

The growth and differentiation of rat lens epithelial cells in tissue culture were studied. Cells could be maintained for a number of generations in an undifferentiated state in suspension culture. When cultured as monolayers, they grew and differentiated in a series of six defined stages described here. These stages include morphological changes (elongation, followed by cell "spreading" or formation of cell aggregates), and biochemical changes (appearance of nu-crystallin protein as detected by immunofluorescence). The process of differentiation appeared to be accelerated in the vicinity of elongated cells, occurred more rapidly at high cell density, and required frequent changes of medium. This suggests that cell-cell communication, and not medium factors, may be essential for promoting differentiation. The final morphology of the differentiated cells differed, depending on the embryonic age of the rats used as a source of lens epithelial cells. This implies that the programme for differentiation changes as a function of the embryonic age of the lens.