Non-coding RNAs: Lincing DNA damage and protection in the cardiovascular system

The inner layer of the blood vessels is the so-called endothelium that consists of a single layer of endothelial cells.The endothelium is an important part of the blood vessel that is needed for blood clotting, wound healing inflammation, formation of new blood vessels, and blood pressure regulation. Abnormal functioning of the endothelial cells may lead to cardiovascular diseases such as atherosclerosis, myocardial infarction, hypertension, and stroke. In this thesis, new and promising RNA-based therapeutics for cardiovascular diseases are described (chapter 2). RNA-based therapy is a promising new strategy against cardiovascular disease Cardiovascular disease is the major cause of death globally, in which the number of deaths is increasing every year. Much effort is put into development of new treatment strategies. RNA-based therapy is a promising new strategy to treat different cardiovascular disorders. LncRNA AERRIE and TERRA are important regulators of cellular function In this thesis we focus on two lncRNAs called AERRIE and TERRA. AERRIE is an abbreviation for Aging and EndMT regulated RNA in Endothelium, whereas TERRA stands for Telomeric-Repeat-containing RNA. In chapter 3 we describe the role of lncRNA AERRIE in endothelial cells. Cells are constantly exposed to DNA damaging factors and they must maintain its genomic integrity by repairing its DNA. We found that the loss of AERRIE shows endothelial dysfunction. The affected cells are showing impairment of migration, barrier function, and angiogenic sprouting. Upon overexpression of AERRIE we observed that angiogenic sprouting, and DNA repair is improved. We found that AERRIE associates with a protein called YBX1 to regulate DNA damage signaling and repair to improve angiogenic sprouting. AERRIE and YBX1 act as important RNA-protein partners of the DNA repair pathway to maintain cellular function in endothelial cells. We further investigated the role of AERRIE in Endothelial-to-Mesenchymal Transition (EndMT) (chapter 4). EndMT is a process where endothelial cells change their phenotype towards mesenchymal cells. It is a dynamic process in which the cells become more migratory and invasive. This event is found in embryonic development, but also in pathological conditions. We observed that AERRIE was upregulated in endothelial cells that are undergoing EndMT. Although we expected to see a change in the structure of the monolayer, EndMT and endothelial markers, and barrier function upon change of expression of AERRIE in EndMT cells, no significant changes were observed. Interestingly, the study showed that AERRIE is regulated by an EndMT regulator called JMJD2B and subsequently regulates SULF1 expression. We concluded that Aerrie is a novel factor in EndMT, required for SULF1 expression, but not important to the transition process itself. The role of lncRNA TERRA in cardiovascular setting was still unknown. In our study described in chapter 5, we investigated the function of TERRA in cardiomyocytes and endothelial cells. We found that TERRA is upregulated in the hearts of old mice and late passage human endothelial cells. Knockdown of TERRA resulted in increased apoptosis, telomere dysfunction induced foci (TIFs), activated P53, DNA damage, and decreased telomere length in cardiomyocytes and endothelial cells, while overexpression led to a decrease of all the called events and an increased telomere length in endothelial cells. We found that TERRA regulates PON2 and XIAP in endothelial cells, but our knowledge of their mechanism is still rather limited and needs more investigation.