Secreted long non-coding RNAs Gadlor1 and Gadlor2 aggravate cardiac remodelling by affecting multiple cardiac cell types during pressure overload

Pathological cardiac overload triggers maladaptive myocardial remodelling that predisposes to the development of heart failure. The contribution of lncRNAs to intercellular signalling during cardiac remodelling is largely unknown. We analysed the expression of Gadlor 1 and 2 lncRNAs in mouse hearts, mouse cardiac cells, extracellular vesicles, human failing hearts as well as human serum from patients. Gadlor knock-out (KO) mice were generated and analysed. The effect of Gadlor knock-out and Gadlor overexpression during cardiac pressure overload induced by transverse aortic constriction (TAC) was analysed by echocardiography, histological analyses and RNA sequencing in isolated cardiac cells. Gadlor interaction partners were identified by RNA antisense purification coupled with mass-spectrometry (RAP-MS). In the heart, the related lncRNAs Gadlor1 and 2 are mainly expressed in endothelial cells and to a lesser extent in fibroblasts. Gadlor1 and 2 are upregulated in failing mouse hearts as well as in the myocardium and in serum of heart failure patients. Interestingly, Gadlor1 and 2 are secreted from endothelial cells within extracellular vesicles (EVs), which are taken up by cardiomyocytes. Gadlor KO mice exerted reduced cardiomyocyte hypertrophy, myocardial fibrosis and improved cardiac function, but paradoxically suffered from sudden death during prolonged overload. Gadlor overexpression, in turn, triggered hypertrophy, fibrosis and cardiac dysfunction. Mechanistically, Gadlor1 and 2 inhibit angiogenic gene expression in endothelial cells, while promoting the expression of pro-fibrotic genes in cardiac fibroblasts. In cardiomyocytes, Gadlors upregulate mitochondrial genes, but downregulate angiogenesis genes, while at the same interacting with the transcriptional regulator Glyr1 and the calcium/calmodulin-dependent protein kinase type II (CaMKII), entailing cardiomyocyte hypertrophy and perturbed cardiomyocyte calcium dynamics.We describe that Gadlor1 and 2, two related, novel lncRNAs, are upregulated in cardiac pathological overload and are secreted from endothelial cells within EVs. Gadlors induce cardiac dysfunction, cardiomyocyte hypertrophy and myocardial fibrosis by exerting heterocellular effects on cardiac cellular gene-expression and by affecting calcium dynamics in cardiomyocytes, which take up the Gadlors by EV mediated transfer from endothelial cells. Targeted inhibition of Gadlors in endothelial cells or fibroblasts might serve as therapeutic strategy in the future.