Abstract Aims Vascular aging is characterized by the progressive deterioration of endothelial function. Long non-coding RNAs (lncRNAs) are critical regulators of gene expression and protein function. However, their involvement in aging-related dysregulation of endothelial cell function remains largely unknown. Here, we aim to characterize the aging-regulated lncRNA MIRIAL in endothelial cells. Methods + Results We identified Mirial as an aging-induced lncRNA in RNA-sequencing data of mouse cardiac endothelial cells. In human umbilical vein endothelial cells (HUVECs), gapmer-mediated knockdown of MIRIAL led to decreases in proliferation, migration and basal angiogenic sprouting. Additionally, MIRIAL knockdown led to increased mitochondrial mass, spare respiratory capacity, and vascular endothelial growth factor (VEGF)-stimulated sprouting. Mechanistically, we demonstrate that MIRIAL forms an RNA ·DNA:DNA triple helix (triplex) with a regulatory region of the quiescence-promoting Forkhead Box O1 ( FOXO1 ) gene, thus inducing its expression. The formation of this triplex involves an Alu element within the MIRIAL transcript, representing a previously undescribed mechanism of action for a lncRNA. Further, we generated a global Mirial knockout mouse line of. Angiogenic sprouting of aortic rings from Mirial knockout mice was reduced under basal conditions, but increased after VEGF administration, validating the in vitro angiogenic phenotype. Importantly, cardiac contractile function after acute myocardial infarction is severely reduced in Mirial knockout mice, as compared to wild-type littermates. Conclusions The lncRNA MIRIAL is an aging-induced regulator of endothelial quiescence and metabolism. Translational Perspective LncRNAs often exhibit cell-type or tissue-specific expression and regulation, rendering them potentially druggable targets requiring lower doses and having fewer side effects compared to protein targets. Our current research highlights, that loss of Mirial correlates with adverse outcomes post-acute myocardial infarction in a murine model. Dysregulation of MIRIAL in various human pathological conditions, such as ischemic heart disease, abdominal aortic aneurysm, cancer, and aging, indicates its potential as a diagnostic marker. Mechanistically, MIRIAL regulates endothelial quiescence by modulating FOXO1 expression, suggesting it as a promising therapeutic target to counteract the age-related decline in endothelial cell function.

The aging-induced long non-coding RNAMIRIALcontrols endothelial cell and mitochondrial function