Aim:To investigate the possible inducible effects of icariin,icaritin,anddesmethylicaritin on the directional differentiation of embryonic stem(ES)cellsinto cardiomyocytes in vitro.Methods:ES cells were cultivated as embryoidbodies(EBs)in hanging drops with icariin,icaritin,or desmethylicaritin.ES cellstreated with retinoic acid and with solvent were used as positive and negativecontrols,respectively.The cardiomyocytes derived from the ES cells were veri-fied using immunocytochemistry.The expression of cardiac developmental-dependent genes was detected using the reverse transcription-polymerase chainreaction(RT-PCR)method.Cell cycle distribution and apoptosis were analyzedusing flow cytometry to determine the partly inducible effect mechanisms involved.Results:The total percentage of beating EBs treated with 1×10~(-7)mol/L icariin,icaritin,or desmethylicaritin was 87%(P<0.01),59%(P<0.01),and 49%,respectively.All the beating cardiomyocytes derived from the ES cells expressed cardiac-specific proteins for α-actinin and troponin T.Among them,1×10~(-7)mol/L icariintreatment resulted in a significantly advanced and increased mRNA level ofα-cardiac myosin heavy chain(MHC)and myosin light chain 2v(MLC-2v)in EBsin the early cardiac developmental stage.Before shifting to the cardiomyocytephenotype,icariin could evoke the accumulation of ES cells in G_0/G_1 and acceler-ate apoptosis of the cell population(P<0.05).Conclusion:Icariin facilitated thedirectional differentiation of ES cells into cardiomyocytes at a concentration of1×10~(-7)mol/L.The promoting effect of icariin on cardiac differentiation was relatedto increasing and accelerating gene expression of a-cardiac MHC and MLC-2v,aswell as regulating the cell cycles and inducing apoptosis. Aim:To investigate the possible inducible effects of icariin,icaritin,anddesmethylicaritin on the directional differentiation of embryonic stem(ES)cellsinto cardiomyocytes in vitro.Methods:ES cells were biolab as embryoidbodies(EBs)in hanging drops with icariin,icaritin,or desmethylicaritin .ES cellstreated with retinoic acid and with solvent were used as positive and negativecontrols,respectively.The cardiomyocytes derived from the ES cells were veri-fied using immunocytochemistry.The expression of cardiac developmental-dependent genes was detected using the reverse transcription-polymerase chainreaction( RT-PCR)method.Cell cycle distribution and apoptosis were conducting using flow cytometry to determine the partly inducible effect mechanisms affecting.Results:The total percentage of beating EBs treated with 1×10 -7 mol/L icariin, icaritin,or Desmethylicaritin was 87% (P<0.01), 59% (P<0.01), and 49%,respectively.All the beating cardiomyocytes derived from the ES cells stem cardiac-sp Ecific proteins for α-actinin and troponin T.Among them,1×10 -7 mol/L icariintreatment resulted in a significantly advanced and increased mRNA level of α-cardiac myosin heavy chain (MHC) and myosin light chain 2v(MLC -2v)in EBsin the early cardiac developmental stage.Before shifting to the cardiomyocytephenotype,icariin could evoke the accumulation of ES cells in G_0/G_1 and acceler-ate apoptosis of the cell population (P<0.05). Conclusion: Icariin facilitated the directional differentiation Of ES cells into cardiomyocytes at a concentration of1×10~(-7)mol/L.The promoting effect of icariin on cardiac differentiation was relatedto increasing and accelerating gene expression of a-cardiac MHC and MLC-2v,aswell as regulating the cell Cycles and inducing apoptosis.