The circular RNA Ataxia Telangiectasia Mutated regulates oxidative stress in smooth muscle cells in expanding abdominal aortic aneurysms

An abdominal aortic aneurysm (AAA) is a pathological widening of the aortic wall characterized by loss of smooth muscle cells (SMCs), extracellular matrix degradation, and local inflammation. This condition is often asymptomatic until rupture occurs, leading to high morbidity and mortality rates. Diagnosis is mostly accidental and the only currently available treatment option remains surgical intervention. Circular RNAs (circRNAs) represent a novel class of regulatory non-coding RNAs that originate from backsplicing. Their highly stable loop structure, combined with a remarkable enrichment in body fluids, make circRNAs promising disease biomarkers. We investigated the contribution of circRNAs to AAA pathogenesis and their potential application to improve AAA diagnostics. Gene expression analysis revealed the presence of deregulated circular transcripts stemming from AAA-relevant gene loci. Among these, the circRNA to the Ataxia Telangiectasia Mutated gene (cATM) was upregulated in human AAA specimens, in AAA-derived SMCs, and serum samples collected from aneurysm patients. In primary aortic SMCs, cATM increased upon angiotensin II and doxorubicin stimulation, while its silencing triggered apoptosis. Higher cATM levels made AAA-derived SMCs less vulnerable to oxidative stress, compared with control SMCs. These data suggest that cATM contributes to elicit an adaptive oxidative-stress response in SMCs and provides a reliable AAA disease signature

Long Noncoding RNA MIAT Controls Advanced Atherosclerotic Lesion Formation and Plaque Destabilization

BACKGROUND Long noncoding RNAs (lncRNAs) are important regulators of biological processes involved in vascular tissue homeostasis and disease development. The present study assessed the functional contribution of the lncRNA myocardial infarction-associated transcript (MIAT) to atherosclerosis and carotid artery disease. METHODS We profiled differences in RNA transcript expression in patients with advanced carotid artery atherosclerotic lesions from the Biobank of Karolinska Endarterectomies. The lncRNA MIAT was identified as the most upregulated noncoding RNA transcript in carotid plaques compared with nonatherosclerotic control arteries, which was confirmed by quantitative real-time polymerase chain reaction and in situ hybridization. RESULTS Experimental knockdown of MIAT, using site-specific antisense oligonucleotides (LNA-GapmeRs) not only markedly decreased proliferation and migration rates of cultured human carotid artery smooth muscle cells (SMCs) but also increased their apoptosis. MIAT mechanistically regulated SMC proliferation through the EGR1 (Early Growth Response 1)-ELK1 (ETS Transcription Factor ELK1)-ERK (Extracellular Signal-Regulated Kinase) pathway. MIAT is further involved in SMC phenotypic transition to proinflammatory macrophage-like cells through binding to the promoter region of KLF4 and enhancing its transcription. Studies using Miat$^{-/-}$ and Miat$^{-/-}$ApoE$^{-/-}$ mice, and Yucatan LDLR$^{-/-}$ mini-pigs, as well, confirmed the regulatory role of this lncRNA in SMC de- and transdifferentiation and advanced atherosclerotic lesion formation. CONCLUSIONS The lncRNA MIAT is a novel regulator of cellular processes in advanced atherosclerosis that controls proliferation, apoptosis, and phenotypic transition of SMCs, and the proinflammatory properties of macrophages, as well

Biobanking: Objectives, Requirements, and Future Challenges—Experiences from the Munich Vascular Biobank

Collecting biological tissue samples in a biobank grants a unique opportunity to validate diagnostic and therapeutic strategies for translational and clinical research. In the present work, we provide our long-standing experience in establishing and maintaining a biobank of vascular tissue samples, including the evaluation of tissue quality, especially in formalin-fixed paraffin-embedded specimens (FFPE). Our Munich Vascular Biobank includes, thus far, vascular biomaterial from patients with high-grade carotid artery stenosis (n = 1567), peripheral arterial disease (n = 703), and abdominal aortic aneurysm (n = 481) from our Department of Vascular and Endovascular Surgery (January 2004⁻December 2018). Vascular tissue samples are continuously processed and characterized to assess tissue morphology, histological quality, cellular composition, inflammation, calcification, neovascularization, and the content of elastin and collagen fibers. Atherosclerotic plaques are further classified in accordance with the American Heart Association (AHA), and plaque stability is determined. In order to assess the quality of RNA from FFPE tissue samples over time (2009⁻2018), RNA integrity number (RIN) and the extent of RNA fragmentation were evaluated. Expression analysis was performed with two housekeeping genes—glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and beta-actin (ACTB)—using TaqMan-based quantitative reverse-transcription polymerase chain reaction (qRT)-PCR. FFPE biospecimens demonstrated unaltered RNA stability over time for up to 10 years. Furthermore, we provide a protocol for processing tissue samples in our Munich Vascular Biobank. In this work, we demonstrate that biobanking is an important tool not only for scientific research but also for clinical usage and personalized medicine