Secreted long non-coding RNAs Gadlor1 and Gadlor2 affect multiple cardiac cell types and aggravate cardiac remodeling during pressure overload
BackgroundPathological overload triggers maladaptive myocardial remodeling that leads to heart failure. Recent studies have shown that long non-coding RNAs (lncRNAs) regulate cardiac remodeling. This study investigates two recently discovered, secreted lncRNAs, Gadlor1 and Gadlor2 (Gadlor 1/2). MethodsWe generated compound Gadlor1/2 knock-out (KO) mice and compared their response to pressure overload by transverse aortic constriction (TAC) to that of wild-type (WT) littermates. Endothelial cells, fibroblasts and cardiomyocytes were isolated from the hearts of both genotypes after TAC and their transcriptome was investigated by RNA sequencing. Gadlor target proteins were identified by RNA antisense purification coupled with mass spectrometry (RAP-MS) in cardiomyocytes. In addition, we investigated the effects of cardiac overexpression of Gadlor1/2. ResultsGadlor1/2 are jointly upregulated in failing mouse hearts as well as in the myocardium of heart failure patients. Cardiac overexpression of Gadlor1 and Gadlor2 aggravated myocardial dysfunction and enhanced hypertrophic and fibrotic remodeling in mice exposed to pressure overload. Compound Gadlor1/2 KO mice, in turn, exerted markedly reduced myocardial hypertrophy, fibrosis and dysfunction, but more angiogenesis during short and long-standing pressure overload. Paradoxically, Gadlor1/2 KO mice suffered from sudden death during prolonged overload, possibly due to cardiac arrhythmia. Gadlor1 and Gadlor2, which are mainly expressed in endothelial cells (ECs) in the heart, where they inhibit pro-angiogenic gene-expression, are strongly secreted within extracellular vesicles (EVs). These EVs transfer Gadlor lncRNAs to cardiomyocytes, where they bind and activate calmodulin-dependent kinase II, induce pro-hypertrophic gene-expression and enhance calcium re-uptake into the sarcoplasmic reticulum. ConclusionGadlor1 and Gadlor2 are lncRNAs that are mainly enriched in EC-derived EVs and are jointly upregulated in mouse and human hearts during pathological overload. We reveal a crucial endothelial cell-cardiomyocyte crosstalk, which aims at restoring calcium homeostasis in cardiomyocytes during overload at the cost of aggravated hypertrophy and fibrosis.