Retinoic acid can change normal differentiation of rat egg-cylinders cultured in vitro

The modified organ culture of rat egg cylinders provides favorable conditions for 2 weeks for the differentiation of main tissue types. To study the effect of retinoids on early rodent differentiation, retinoic acid (RA) was added in various concentrations to serum-supplemented or serum-free medium. Explant survival decreased when RA was added to serum-free medium. Although the cartilage was well differentiated even in cultures deprived of serum, RA inhibited chondrogenesis in all cultures without or with serum. The frequency of columnar epithelium was higher and its folds more often present when RA was added to the medium. Keratinization of squamous epithelium depended on the RA concentration added to the medium, and was almost absent when the concentration was high. Other tissues often present in serum-supplemented medium (such as neuroblasts and myotubes) were not affected by RA, a result that differs from those obtained in other experimental systems.