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AimsPathological overload triggers maladaptive myocardial remodelling that leads to heart failure. Recent studies have shown that long non-coding RNAs (lncRNAs) contribute to the development of cardiac disease. This study investigates two recently discovered and secreted lncRNAs,Gadlor1andGadlor2(Gadlor 1/2).Methods and ResultsIn the heart,Gadlor 1/2are mainly expressed in endothelial cells and to a lesser extent in fibroblasts and cardiomyocytes.Gadlor1/2are upregulated in failing mouse hearts as well as in the myocardium and serum of heart failure patients. Interestingly,Gadlor1/2are secreted from endothelial cells (EC) within extracellular vesicles (EV) and are taken up by cardiomyocytes.Gadlor1/2 knock-out (Gadlor-KO) and overexpression during experimental cardiac pressure overload by transverse aortic constriction (TAC) was analysed.Gadlor-KO mice exhibited reduced cardiomyocyte hypertrophy, enhanced angiogenesis, diminished myocardial fibrosis, and improved cardiac function, but paradoxically suffered from sudden death during prolonged overload.Gadlor1/2overexpression, in turn, aggravated hypertrophy, fibrosis and cardiac dysfunction during TAC. Mechanistically,Gadlor1/2inhibited angiogenic gene expression in endothelial cells, while promoting the expression of pro-fibrotic genes in cardiac fibroblasts. We employed RNA antisense purification coupled with mass spectrometry (RAP-MS) and identified the calcium/calmodulin-dependent protein kinase type II (CaMKII) as interaction partner ofGadlor1/2in cardiomyocytes. By activating CaMKII,Gadlor1/2promoted hypertrophic gene-expression and excitation-contraction coupling in these cells. Accordingly,Gadlorablation entailed reduced hypertrophy, but also increased diastolic calcium levels in the cytosol and arrhythmic beating in cardiomyocytes.ConclusionGadlor1andGadlor2are novel lncRNAs that are mainly enriched in EC-derived EVs and are upregulated in mouse and human hearts during pathological overload.Gadlor1/2affect multiple cardiac cell types and inhibit angiogenesis, induce myocardial fibrosis and hypertrophy as well as alterations in calcium homeostasis in cardiomyocytes. We suggest that inhibition ofGadloreffects in cardiac non-myocytes could be a therapeutic strategy in heart failure.Translational PerspectiveHere, we characterized two secreted lncRNAsGadlor1/2, which are conserved in humans. We observed increasedGadlor1/2levels in human failing myocardium and a negative correlation betweenGADLOR2serum levels and left ventricular ejection fraction in heart failure patients.Gadlor1/2ablation in mice reduces cardiac hypertrophy and fibrosis and increases angiogenesis, but slows calcium re-uptake into the sarcoplasmic reticulum (SR) and might thereby trigger arrhythmia and sudden death when cardiac overload persists in the long term. Inhibition ofGadlor1/2effects in endothelial cells and fibroblasts, on the other hand, could be beneficial by increasing angiogenesis and reducing fibrosis in the heart.

Heart failure due to high blood pressure or ischemic injury remains a major problem for millions of patients worldwide. Despite enormous advances in deciphering the molecular mechanisms underlying heart failure progression, the cell-type specific adaptations and especially intercellular signaling remain poorly understood. Cardiac fibroblasts express high levels of cardiogenic transcription factors such as GATA-4 and GATA-6, but their role in fibroblasts during stress is not known. Here, we show that fibroblast GATA-4 and GATA-6 promote adaptive remodeling in pressure overload induced cardiac hypertrophy. Using a mouse model with specific single or double deletion of Gata4 and Gata6 in stress activated fibroblasts, we found a reduced myocardial capillarization in mice with Gata4/6 double deletion following pressure overload, while single deletion of Gata4 or Gata6 had no effect. Importantly, we confirmed the reduced angiogenic response using an in vitro co-culture system with Gata4/6 deleted cardiac fibroblasts and endothelial cells. A comprehensive RNA-sequencing analysis revealed an upregulation of anti-angiogenic genes upon Gata4/6 deletion in fibroblasts, and siRNA mediated downregulation of these genes restored endothelial cell growth. In conclusion, we identified a novel role for the cardiogenic transcription factors GATA-4 and GATA-6 in heart fibroblasts, where both proteins act in concert to promote myocardial capillarization and heart function by directing intercellular crosstalk.

Cachexia is associated with poor prognosis in chronic heart failure patients, but the underlying mechanisms of cachexia triggered disease progression remain poorly understood. Here, we investigate whether the dysregulation of myokine expression from wasting skeletal muscle exaggerates heart failure. RNA sequencing from wasting skeletal muscles of mice with heart failure reveals a reduced expression of Ostn, which encodes the secreted myokine Musclin, previously implicated in the enhancement of natriuretic peptide signaling. By generating skeletal muscle specific Ostn knock-out and overexpressing mice, we demonstrate that reduced skeletal muscle Musclin levels exaggerate, while its overexpression in muscle attenuates cardiac dysfunction and myocardial fibrosis during pressure overload. Mechanistically, Musclin enhances the abundance of C-type natriuretic peptide (CNP), thereby promoting cardiomyocyte contractility through protein kinase A and inhibiting fibroblast activation through protein kinase G signaling. Because we also find reduced OSTN expression in skeletal muscle of heart failure patients, augmentation of Musclin might serve as therapeutic strategy., Cachexia is associated with poor prognosis in heart failure. Here the authors show that mice and patients with cardiac cachexia display reduced skeletal muscle expression and circulating levels of Musclin. Musclin ablation in skeletal muscle worsens, while its muscle-specific overexpression ameliorates heart failure in mice.