Opposing Biological Functions of Retinoic Acid in Normal Embryonic Development

Vitamin A and its metabolic derivative, retinoic acid (RA) are essential biomolecules for normal development regulation and regeneration in different organs. Too much and deficiency of vitamin A can be toxic for fetuses lead to birth defects or is associated with many congenital malformations. It has been known that RA alone or in combination with other morphogens promotes the developmental program such as neural differentiation and patterning. Here, we discussed RA role in the neural patterning of the embryonic stem cells and its function in promoting the neural differentiation in neural plate of the developing embryo through attenuating the fibroblast growth factor (FGF) signaling. By using different techniques, we also argued the opposite function of RA in inducing apoptosis in the human umbilical cord-derived mesenchymal stem cells (hUCMSCs) shown by upregulating the caspase expression. Finally, we discussed that some biological parameters including cell density and passage appeared to be involved in this cytotoxicity response