Rabbit corneal epithelial cells grown in vitro without serum

Some continuous or transformed cell lines can be cultivated in vitro in serum free media of defined composition. This property has been compared with the well known serum requirements for normal diploid cells grown in vitro, and it has been suggested that there may be a relation between reduced serum requirements and biologic behavior. However, the real significance of this property is still unclear because there is much variation in serum requirements between different types of transformed cells. The present communication reports an instance of limited, but striking proliferation of normal cells in serum free medium, as follows: primary outgrowth cultures of normal rabbit corneal epithelium can be initiated and propagated in vitro up to 6 days in serum free medium. By the 8th day the majority of cells have ceased to divide. Epithelial cells grown without serum show DNA synthetic activity at a level comparable to control cultures grown with added serum.