BACKGROUND:Previous studies have found that the expression level of miR-25 in differentiated P19 cels is significantly lower than that in undifferentiated P19 cels. However, the effect of miR-25 on cardiomyogenesis and the relevant mechanism remain unclear.
OBJECTIVE: To explore the effect and mechanism of miR-25 on the differentiation of P19 cels into cardiomyocytes.
METHODS:P19 cels were cultured and differentiated into cardiomyocytesin vitro. The expression of miR-25 in differentiated and undifferentiated P19 cels was detected by real-time PCR. miR-25-overexpressing P19 cels were constructed by lipofection transfection, and were used to investigate the effect of miR-25 on the differentiation of P19 cels into cardiomyocytes. MicroRNA target analysis tools were used to explore potential targets of miR-25, and dual luciferase reporter assay was used to identify whether the 3’UTR of Pax3 mRNA was a binding target of miR-25. In addition, we transfected P19 cels with Pax3 shRNAs to silence the expression of Pax3, and investigated the effect of Pax3 on the differentiation of P19 cels into cardiomyocytes.
RESULTS AND CONCLUSION: Expression level of miR-25 in differentiated P19 cels was obviously down-regulated compared with that in undifferentiated P19 cels. miR-25 overexpression promoted the differentiation of P19 cels into cardiomyocytes. By target prediction analysis, we confirmed that Pax3 was a potential target gene of miR-25. Luciferase assay further confirmed that miR-25 targeted Pax3 directly. Moreover, knockdown of Pax3 promoted the differentiation of P19 cels into cardiomyocytes. Taken together, miR-25 promotes the differentiation of P19 cels into cardiomyocytes by targeting Pax3. These findings offer new clues and theoretical basis for cardiomyogenesis and prevention and cure of congenital heart disease.

BACKGROUND: Human umbilical cord mesenchymal stem cells (UC-MSCs), characterized by great differentiation potential, strong proliferation ability and low immunogenicity, exert an immeasurable role in wound repair and vascular regeneration in ischemic tissues.OBJECTIVE: To investigate the effect of intraventricularly injected UC-MSCs on expression of granulocyte-colony stimulating factor (GM-CSF) and transforming growth factor-β1 (TGF-β1) in the myocardium of myocardial infarction rats.METHODS: 120 adult male Sprague-Dawley rats were selected randomly, among which, 20 healthy rats were randomly selected as controls and the rest rats were subcutaneously injected with isoproterenol to establish the myocardial infarction model. Model rats were randomized into model group, UC-MSC supernatant group, UC-MSC low-dose group,middle-dose group and high-dose group, with 20 rats in each group. Twenty-four hours after modeling, normal saline,UC-MSC supernatant, UC-MSC suspensions containing 0.25×106, 1.0×106, 4.0×106 cells (2 mL) were injected intraventricularly into the rats in the corresponding groups, respectively. Left ventricular ejection fraction (LVEF),end-systolic left ventricular volume (LVESV) and left ventricular end-diastolic volume (LVEDV) were measured by echocardiography at 2 weeks after treatment. Serum lactate dehydrogenase (LDH), creatine kinase (CK) and pro-brain natriuretic peptide (Pro-BNP) were measured by enzyme-linked immunosorbent assay (ELISA). At the end of the experiment, 10 rats were killed by dislocation and the cardiac specimens were taken. The myocardial infarct size was determined by nitroblue tetrazolium staining. The expressions of GM-CSF and TGF-β in the myocardium of rats in each group were determined by western blot method.RESULTS AND CONCLUSION: (1) Higher LVEF levels and lower LVESV and LVEDV were found in the low-, middleand high-dose UC-MSC groups than the model group and UC-MSC supernatant group (P < 0.05). LVEF, LVEDV and LVEDV in the middle- and high-dose UC-MSC group were lower than those in the low-dose UC-MSC group (P < 0.05). (2)The levels of serum LDH, CK, Pro-BNP and myocardial tissue GM-CSF and TGF-β1 in the low-, middle- and high-dose UC-MSC group were significantly lower than those in the model group and UC-MSC supernatant group (P < 0.05).Compared with the low-dose UC-MSC group, the levels of serum LDH, CK, Pro-BNP and myocardial tissue GM-CSF and TGF-β1 were significantly lower in the middle- and high-dose UC-MSC groups (P < 0.05). (3) The myocardial infarct sizes of the low-, middle- and high-dose UC-MSC groups were significantly lower than those of the model and UC-MSC supernatant groups (P < 0.05), while the myocardial infarct sizes of middle- and high-dose UC-MSC groups were significantly lower than that of low-dose UC-MSC group (P < 0.05). To conclude, UC-MSCs can significantly reduce the expression of GM-CSF and TGF-β1 in the rat myocardium after myocardial infarction, effectively protect myocardial tissues, and improve cardiac function.