ABSTRACT
<p><b>OBJECTIVE</b>To analyze the influence of retinoic acid (RA) on the undifferentiated state and EB formation abilities of human embryonic stem cells.</p><p><b>METHODS</b>The biological characteristics of H9 ESCs after RA treatment were characterized by real-time PCR, MTS proliferation assay and immunofluorescence staining. The expression of three germ layers markers, osteogenic differentiation markers and adipogenic differentiation markers in H9-differentiated embryoid bodies (EBs) with RA treatment were quantified by real time PCR.</p><p><b>RESULTS</b>The proliferation of H9 ESCs in the early logarithmic growth phase was accelerated by RA treatment. In addition, RA induced differentiation of H9 ESC coupled with morphology changes, decreased expression of undifferentiated markers Oct4, Nanog, Sox2 and OCT4 mRNA binding protein Lin28 at mRNA level, and reduced expression of Oct4 at protein level. RA induced formation of cavities in EBs. Real time PCR results showed that the expressions of ectodermal markers: NeuroD1, Noggin; mesodermal markers: Brachyury, Twist and endodermal markers: AFP, GATA-4 were significantly increased (P < 0.05), especially for AFP (P < 0.01), by RA treatment in a dose-dependent manner. In addition, the expression of adipogenic differentiation marker C/EBPalpha was increased while the osteogenic differentiation marker OPN was decreased in EBs after RA treatment for 5 days.</p><p><b>CONCLUSIONS</b>High concentrations of RA induced the loss of stemness in H9 ESCs and excessive differentiation in EBs, and damaged the balance between osteogenic and adipogenic differentiation during early EB differentiation, which may be relevant to the congenital malformations.</p>