The Effect Of Retinoic Acid On Normal Human Foreskin Epithelial Cells And HPV-Immortalized Cells Grown In Organotypic Raft Cultures
Previous studies have shown that epithelial cells immortalized by human papillomaviruses (HPVs) at late passages were more resistant to the effects of retinoic acid than late passage normal keratinocytes. Some of these late passage HPV-immortalized cells, however, lose the ability to form a cornified envelope with continued culturing. For this reason, early passage normal keratinocytes and early passage HPV-immortalized cells were studied to see if they also showed this resistance to retinoic acid. Normal epithelial cells and cells immortalized by HPVs were grown in organotypic raft cultures and treated with varying amounts of retinoic acid, which normally blocks terminal differentiation in keratinocytes. The cultures were grown for two weeks, fixed, sectioned, and stained with either hematoxylin and eosin (H&E) or an antibody against the keratin K1. The HPV-immortalized cell lines were found to be more resistant to the action of retinoic acid than the normal cells. The same cell lines were also grown in culture plates in the same concentrations of retinoic acid. These cultures were counted daily for one week, and the results were used to construct growth curves and viability charts. It was found that the normal and HPV-immortalized cells show the same response to the growth inhibitory effects of retinoic acid. In addition, the viability of all cell lines was not significantly reduced by the higher concentrations of retinoic acid This showed that the differences in morphology seen in the raft cultures were probably due to a different mechanism than that which causes growth inhibition.