Heterocyclic derivatives of all-trans retinoic acid: in vitro effects on fibroblast/keratinocyte growth and differentiation, and in vivo effects on guinea-pig skin

We investigated the biological effects of five all-trans retinoic acid derivatives, bearing heterocyclic ring systems in the side chain. Growth assays performed on submerged human fibroblast and keratinocyte cultures revealed that (E)4-[2-(5-terbuthyl-thiophen-2-yl)propenyl]benzoic acid (compound 5) is the best compound among the studied derivatives for it exhibits a weaker antiproliferative activity and induces, like all-trans retinoic acid does, a significant increase in fibroblast and keratinocyte growth. The morphological and morphometrical analyses of submerged human fibroblast cultures and human epidermis reconstructed in vitro showed that the compound 5 behaves similarly to all-trans retinoic acid: it induces a decrease in all the cell parameters of submerged fibroblast cultures, and modulates the differentiation of keratinocytes in in vitro reconstructed epidermis. Compound 5 induces thickening of epidermis in vivo, one of the most remarkable pharmacological effects of retinoids on skin, but compared to all-trans retinoic acid, it induces a weaker irritation on guinea-pig skin in terms of both erythema and scaling. Compound 5 could then represent a promising candidate for the treatment of certain dermatological diseases