Expression and Significance of DLL4-–Notch Signaling Pathway in the Differentiation of Human Umbilical Cord Derived Mesenchymal Stem Cells into Cardiomyocytes Induced by 5-Azacytidine

hUCMSCs were isolated and purified from the umbilical cords of normal or cesarean term deliveries under sterile conditions. Flow cytometry analysis revealed that CD13, CD29, CD44, CD90, and CD105 were highly expressed on the surface of passage-3 hUCMSCs, but negative for CD31, CD34, CD45, and HLA-DR. Immunocytochemistry showed that 5-azacytidine (5-aza) could induce the cTnI expression of hUCMSCs. RT-PCR showed that a stable higher level expression of DLL4 and Notch1 gene in 5-aza-induced group was observed compared to that in the control group. There was a higher expression level in the induced group. Compared with control group, the expression levels of Notch1 were, respectively, increased 6.60, 7.36, 7.595, and 7.805 times at 1, 3, 5, and 7 days after intervention of 5-aza. Statistically higher Ct value of Notch1 mRNA in induced group was observed in comparison with that of the control group (0.51 ± 0.21 vs 7.85 ± 0.35, t = 35.98, P < 0.01). The expression level of DLL4 increased stably compared with the control group. Compared with control group, the expression levels of DLL4 were, respectively, increased 11.53, 10.1, 10.17, and 11.46 times at 1, 3, 5, and 7 days after intervention of 5-aza. There was a significant difference of DLL4 Ct value between the 5-aza-induced group and the control group (1.60 ± 0.49 vs 12.42 ± 0.73, t = 11.71, P < 0.01). In conclusion, hUCMSCs can be differentiated into myocardial cells in vitro. The DLL4–Notch signaling pathway may be involved in the differentiation of hUCMSCs into cardiomyocytes induced by 5-aza.