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Significance Here we show that the histone demethylase JMJD2B is induced in endothelial cells by EndMT provoking stimuli and thereby contributes to the acquirement of a mesenchymal/smooth muscle phenotype. Silencing of JMJD2B inhibited EndMT in vitro and reduced the induction of EndMT after myocardial infarction in vivo. Inhibition of JMJD2B prevents the demethylation of repressive trimethylated histone H3 at lysine 9 (H3K9me3) at promoters of mesenchymal and EndMT-controlling genes, thereby reducing EndMT. Together, our study reports a crucial role for JMJD2B in controlling histone modifications during the transition of endothelial cells toward a mesenchymal phenotype., Endothelial cells play an important role in maintenance of the vascular system and the repair after injury. Under proinflammatory conditions, endothelial cells can acquire a mesenchymal phenotype by a process named endothelial-to-mesenchymal transition (EndMT), which affects the functional properties of endothelial cells. Here, we investigated the epigenetic control of EndMT. We show that the histone demethylase JMJD2B is induced by EndMT-promoting, proinflammatory, and hypoxic conditions. Silencing of JMJD2B reduced TGF-β2-induced expression of mesenchymal genes, prevented the alterations in endothelial morphology and impaired endothelial barrier function. Endothelial-specific deletion of JMJD2B in vivo confirmed a reduction of EndMT after myocardial infarction. EndMT did not affect global H3K9me3 levels but induced a site-specific reduction of repressive H3K9me3 marks at promoters of mesenchymal genes, such as Calponin (CNN1), and genes involved in TGF-β signaling, such as AKT Serine/Threonine Kinase 3 (AKT3) and Sulfatase 1 (SULF1). Silencing of JMJD2B prevented the EndMT-induced reduction of H3K9me3 marks at these promotors and further repressed these EndMT-related genes. Our study reveals that endothelial identity and function is critically controlled by the histone demethylase JMJD2B, which is induced by EndMT-promoting, proinflammatory, and hypoxic conditions, and supports the acquirement of a mesenchymal phenotype.

Background: The majority of the human genome comprises noncoding sequences, which are in part transcribed as long noncoding RNAs (lncRNAs). lncRNAs exhibit multiple functions, including the epigenetic control of gene expression. In this study, the effect of the lncRNA MALAT1 (metastasis-associated lung adenocarcinoma transcript 1) on atherosclerosis was examined. Methods: The effect of MALAT1 on atherosclerosis was determined in apolipoprotein E–deficient (Apoe − /− ) MALAT1-deficient (Malat1 −/− ) mice that were fed with a high-fat diet and by studying the regulation of MALAT1 in human plaques. Results: Apoe −/− Malat1 −/− mice that were fed a high-fat diet showed increased plaque size and infiltration of inflammatory CD45 + cells compared with Apoe −/− Malat1 +/+ control mice. Bone marrow transplantation of Apoe −/− Malat1 −/− bone marrow cells in Apoe −/− Malat1 +/+ mice enhanced atherosclerotic lesion formation, which suggests that hematopoietic cells mediate the proatherosclerotic phenotype. Indeed, bone marrow cells isolated from Malat1 −/− mice showed increased adhesion to endothelial cells and elevated levels of proinflammatory mediators. Moreover, myeloid cells of Malat1 −/− mice displayed enhanced adhesion to atherosclerotic arteries in vivo. The anti-inflammatory effects of MALAT1 were attributed in part to reduction of the microRNA miR-503. MALAT1 expression was further significantly decreased in human plaques compared with normal arteries and was lower in symptomatic versus asymptomatic patients. Lower levels of MALAT1 in human plaques were associated with a worse prognosis. Conclusions: Reduced levels of MALAT1 augment atherosclerotic lesion formation in mice and are associated with human atherosclerotic disease. The proatherosclerotic effects observed in Malat1 −/− mice were mainly caused by enhanced accumulation of hematopoietic cells.

Objective— Endothelial cells play important roles in tissue homeostasis and vascularization, a function that is impaired by aging. Here, we aim to decipher the role of the microenvironment underlying the impairment of endothelial cell functions by aging. Approach and Results— RNA sequencing of isolated cardiac endothelial cells derived from young and 18-month-old mouse hearts revealed that aging affects the endothelial expression of genes encoding extracellular matrix proteins, specifically the laminin β1 ( Lamb1 ) and laminin β2 ( Lamb2 ) chains. Whereas Lamb1 was upregulated, Lamb2 was decreased in endothelial cells in old mice compared with young controls. A similar change in expression patterns was observed after induction of acute myocardial infarction. Mimicking aging and injury conditions by plating endothelial cells on laminin β1–containing laminin 411 matrix impaired endothelial cell adhesion, migration, and tube formation and augmented endothelial-to-mesenchymal transition and endothelial detachment compared with laminin 421, which contains the laminin β2 chain. Because laminins can signal via integrin receptors, we determined the activation of ITGB1 (integrin β1). Laminin 421 coating induced a higher activation of ITGB1 compared with laminin 411. siRNA-mediated silencing of ITGB1 reduced laminin β2–dependent adhesion, suggesting that laminin β2 more efficiently activates ITGB1. Conclusions— Mimicking age-related modulation of laminin β1 versus β2 chain expression changes the functional properties and phenotype of endothelial cells. The dysregulation of the extracellular matrix during vascular aging may contribute to age-associated impairment of organ function and fibrosis.