Ultrastructural analysis of the retinoid-induced reversal of epithelial hyperplasia and metaplasia

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Abstract
The 7,12-dimethylbenzanthracene-induced skin papilloma of the mouse and the 3-methylcholanthrene-induced hyperplasia and metaplasia in prostate organ cultures were studied by electron microscopy. The two types of tissue both showed a reversal of hyperplasia and metaplasia when treated with retinoids (= vitamin A and analogs). This reversal was reached by means that are quite characteristic for a given type of tissue. In the skin, DNA-synthetic activity was not influenced by retinoid treatment. There was, however, considerable necrosis and an impressive mucous metaplasia. The latter might be at least partly responsible for the cell loss, probably through a loss of anchorage in the prickle-cell layer. In the prostate, no mucous metaplasia was observed, but there was an important depression of DNA-synthetic activity. The secretory apparatus reappeared together with the microvilli, possibly induced by the slowing down of cell division.