Objective: To study the effects of retinoic acid(RA) alone or combined with purmorphamine(PM) on the differentiation of the human umbilical cord mesenchymal stem cells(hUCMSCs) into the motoneurons,and to provide the experimental data for further clinical practice.Methods: Purified hUCMSCs were extracted with the double enzyme digestion method.The expressions of the surface antigen CD29,CD31,CD34,CD44 were detected on the 3rd generation of hUCMSCs.Four groups were classified according to the different compo...