NKX2-5 is expressed in the heart throughout life. We targeted eGFP sequences to the NKX2-5 locus of human embryonic stem cells (hESCs); NKX2-5(eGFP/w) hESCs facilitate quantification of cardiac differentiation, purification of hESC-derived committed cardiac progenitor cells (hESC-CPCs) and cardiomyocytes (hESC-CMs) and the standardization of differentiation protocols. We used NKX2-5 eGFP(+) cells to identify VCAM1 and SIRPA as cell-surface markers expressed in cardiac lineages.

Aims Differential microRNA expression in peripheral blood has been observed in patients with heart failure, suggesting their value as potential biomarkers and likely contributors to disease mechanisms. In the present study, we aimed to evaluate the transcardiac gradient of 84 cardio‐microRNAs in healthy and failing hearts to determine which microRNAs are released or absorbed by the myocardium in heart failure. Methods and results Eight healthy volunteers and nine patients with congestive heart failure were included. Arterial and coronary sinus blood samples were collected, and microRNAs were extracted. The expression of microRNAs was analysed using real‐time PCR by the miScript miRNA PCR Array Human Cardiovascular Disease. In coronary sinus samples, the microRNAs miR‐16‐5p, miR‐27a‐3p, miR‐27b‐3p, miR‐29b‐3p, miR‐29c‐3p, miR‐30e‐5p, miR‐92a‐3p, miR‐125b‐5p, miR‐140‐5p, miR‐195‐5p, miR‐424‐5p, and miR‐451a were significantly down‐regulated, and let‐7a‐5p, let‐7c‐5p, let‐7e‐5p, miR‐23b‐3p, miR‐107, miR‐155‐5p, miR‐181a‐5p, miR‐181b‐5p and miR‐320a were up‐regulated in heart failure. Left ventricular filling pressure was negatively correlated with miR‐195, miR‐16, miR‐29b‐3p, miR‐29c‐3p, miR‐451a, and miR‐92a‐3p. The failing heart released let‐7b‐5p, let‐7c‐5p, let‐7e‐5p, miR‐122‐5p, and miR‐21‐5p, and absorbed miR‐16‐5p, miR‐17‐5p, miR‐27a‐3p, miR‐30a‐5p, miR‐30d‐5p, miR‐30e‐5p, miR‐130a‐3p, miR‐140‐5p, miR‐199a‐5p, and miR‐451a. In silico analyses suggest that the transcardiac gradient of microRNAs in heart failure may target pathways related to heart disease. Conclusion We determined the transcardiac gradient of cardio‐microRNAs in failing hearts, which supports the use of these microRNAs as potential biomarkers. The microRNAs described here may have a role in the pathophysiology of heart failure as they might be involved in pathways related to disease progression, including fibrosis.

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This study suggests the presence of iron depletion in the failing human heart, providing a potential link for the association between anemia and adverse prognosis in HF.

Background-Despite adequate rate control, the combination of atrial fibrillation with heart failure (HF) has been shown, in a number of studies, to hasten HF progression. In this context, we aimed to test the hypothesis that an irregular ventricular rhythm causes an alteration in ventricular cardiomyocyte excitation-contraction coupling which contributes to the progression of HF. Methods and Results-We investigated the effects of electrical field stimulation (average frequency 2 Hz) in an irregular versus regular drive train pattern on the expression of calcium-handling genes and proteins in rat ventricular myocytes. The effect of rhythm on intracellular calcium transients was examined using Fura-2AM fluorescence spectroscopy. In conjunction, calcium-handling protein expression was examined in left ventricular samples obtained from end-stage HF patients, in patients with either persistent atrial fibrillation or sinus rhythm. Compared with regularly paced ventricular cardiomyocytes, in cells paced irregularly for 24 hours, there was a significant reduction in the expression of sarcoplasmic reticulum calcium (Ca 2+ ) ATPase together with reduced serine-16 phosphorylation of phospholamban. These findings were accompanied by a 59% reduction (P<0.01) in the peak Ca2+ transient in irregulary paced myocytes compared with those with regular pacing. Consistent with these observations, we observed a 54% (P<0.05) decrease in sarcoplasmic reticulum Ca 2+ATPase protein expression and an 85% (P<0.01) reduction in the extent of phosphorylation of phospholamban in the left ventricular myocardium of HF patients in atrial fibrillation compared with those in sinus rhythm. Conclusions-Together, these data demonstrate that ventricular rhythmicity contributes significantly to excitationcontraction coupling by altering the expression and activity of key calcium-handling proteins. These data suggest that control of rhythm may be of benefit in patients with HF. (Circ Heart Fail. 2012;5:786-793.)