The role of lncRNA Sarrah in human cardiomyocytes

Long non-coding RNAs (lncRNAs) contribute to (patho)physiological processes in the heart. Aging is the major risk factor for cardiovascular disease and cardiomyocyte apoptosis is an underlying cause for age-related cardiac dysfunction. RNA sequencing of cardiomyocytes from young and aged mouse hearts revealed several aging-regulated lncRNAs. An siRNA screen for caspase activity identified the aging-regulated lncRNA Sarrah (ENSMUST00000140003) as anti-apoptotic, which we confirmed in human cells (human SARRAH is annotated as OXCT1-AS1). Importantly, human engineered heart tissue showed impaired contractile force development upon SARRAH knockdown compared with controls. Computational prediction of RNA-DNA triple helix formation showed that SARRAH may directly bind the promoters of genes downregulated after SARRAH silencing, which mainly consist of cell survival genes. Indeed, nuclear magnetic resonance spectroscopy confirmed RNA-DNA triple helix formation and cardiomyocytes lacking the triple helix-forming domain of Sarrah showed an increase in apoptosis. One of the key direct SARRAH targets is NRF2, an anti-oxidant transcription factor. Restoration of NRF2 levels after SARRAH silencing partially rescues the reduction in cell viability. RNA affinity purification mass spectrometry analysis identified CRIP2 as main protein interaction partner. Furthermore, SARRAH associates with acetyltransferase p300 and acetylated histone H3K27. Finally, Sarrah was also profoundly downregulated after acute myocardial infarction (AMI) in mice. Adeno-associated virus-mediated overexpression of Sarrah in mice showed better recovery of cardiac contractile function after AMI compared to control mice, as measured by echocardiography and magnetic resonance imaging, consistent with a decrease in cardiomyocyte cell death and an increase in endothelial cell proliferation. In summary, we identified the anti-apoptotic evolutionary conserved lncRNA Sarrah, which is downregulated by aging, as a pivotal regulator of cardiomyocyte survival. Sarrah overexpression has beneficial effects on AMI recovery highlighting it as a potential therapeutic approach against heart failure. 3 replicates human cardiomyocytes were transfected with control gapmeRs and, in parallel, 3 replicates human cardiomyocytes were transfected with gapmeRs targeting lncRNA Sarrah