Background: Retinoic acid (RA) is a vitamin A derivative and one of the most important inducing signals in vertebrates that is involved in differentiation, morphogenesis, apoptosis, and reproduction. This study was done to evaluate the role of RA in in vitro neural patterning of mouse embryonic stem cells (mESCs).

Materials and Methods: In this experimental study, upon formation, embryoid bodies (EBs) from mESCs, Royan B1, were induced by 1 µM RA for four days and then plated for eight days. Untreated EBs were considered as the control group. Finally, in both groups, neural induction and patterning of EB-derived neural cells were evaluated by using immunostaining, flowcytometry, and RT-PCR methods.

Results: RA induced neurogenesis in ES cells, from which 35% showed to express MAP2. RT-PCR analysis also indicated that RA-treated neural cells derived from ES cells could at the same time express Mash1, Pax6/7, and Dbx1/2 as dorso-ventral (DV) pattering markers and Hoxb4, Hoxc5, and Hoxc8 as the rostro-caudal (RC) axis markers.

Conclusion: RA induces in vitro neural induction along with neural patterning of ES-derived neural cells in DV and RC axes. Keywords: Mouse embryonic stem cells, neural patterning, retinoic acid