en Cellular & Molecular Research Cellular & Molecular Research Original Research Original Research <strong>Background: </strong>A wide variety of cytokines are released from human amniotic membrane cells (hAMCs), which can increase the rate of differentiation of mesenchymal stem cells into the neurons. We studied the effect of Retinoic Acid (RA) on the differentiation rate of human Umbilical Cord Mesenchymal Stem Cells (hUMSCs) which were co-cultured with hAMCs.<br> &nbsp;&nbsp; <strong>Methods:</strong> In this experimental study, both hUMSCs and hAMCs were isolated from postpartum human umbilical cords and placenta respectively. The expression of mesenchymal (CD73, CD90 and CD105), hematopoietic and endothelial (CD34 and CD45) markers in hUMSCs were confirmed by flow cytometry. The hUMSCs were cultured in four distinct groups: group 1) Control, group 2) Co-culture with hAMCs, group 3) RA treatment and group 4) Co-culture with hAMCs treated by RA. Twelve days after culturing, the expression of NSE, MAP2 and ChAT differentiation genes and their related proteins were examined by real-time PCR and immunocytochemistry respectively.<br> &nbsp;&nbsp; <strong>Results:</strong> The flow-cytometry analysis indicated increased expression of mesenchymal markers and a low expression of both hematopoietic and endothelial markers (CD73:98.24%, CD90: 97.32%, CD105: 90.75%, CD34: 2.96%, and CD45:1.74%). Moreover, the expression of both NSE and MAP2 markers was increased significantly in all studied groups in comparison to the control group&nbsp; On the other hand, the expression of ChAT had a significant increase in the group 2 and 4 (RA and RA+ co-culture).<br> &nbsp;&nbsp; <strong>Conclusion:</strong> RA can be used as an effective inducer to differentiate hUMSCs into cholinergic-like cells, and hAMCs could increase the number of differentiated cells as an effective factor. Amniotic Membrane, Cell Differentiation, Mesenchymal Stem Cell, Neurons, Retinoic acid 962 968 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-5928-1&slc_lang=en&sid=1 Mohammad-Reza Kouchakian kouchakian.mr@gmail.com 200319475328460065774 200319475328460065774 No Department of Anatomy, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran Morteza Koruji koruji@iums.ac.ir 200319475328460065775 200319475328460065775 No Department of Anatomy, Faculty of Medicine, & Stem Cell and Regenerative Medicine Research Center, Iran University of Medical Scienc-es, Tehran, Iran Mohammad Najafi nbsmmsbn@tums.ac.ir 200319475328460065776 200319475328460065776 No Department of Biochemistry, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran Seyedeh Farzaneh Moniri monirifarzane@gmail.com 200319475328460065777 200319475328460065777 No Department of Anatomy, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Alireza Asgari alirezaasgari9@gmail.com 200319475328460065778 200319475328460065778 No School of Pharmacy, Zanjan University of medical sciences, Zanjan, Iran Marjan Shariatpanahi shariatpanahi.m@iums.ac.ir 200319475328460065779 200319475328460065779 No 6. Department of Toxicology & Pharmacology, School of Pharmacy, International Campus, Iran University of Medical Sciences, Tehran, Iran Seyed Akbar Moosavi seyedmoos@gmail.com 200319475328460065780 200319475328460065780 No Hamid Reza Asgari asgari.hr@iums.ac.ir, hamidrezaasgari99@gmail.com 200319475328460065781 200319475328460065781 Yes Department of Anatomy, Faculty of Medicine, & Stem Cell and Regenerative Medicine Research Center, & Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran, Iran