Abstract 512: The Long Non-coding Rna MIAT Regulates Smooth Muscle Cell Proliferation and Macrophage Activity in Advanced Atherosclerotic Lesions

Background: Long noncoding RNAs (lncRNAs) have emerged as critical epigenetic regulators in various biological processes and diseases. Here we sought to identify and functionally characterize the lncRNA MIAT as a novel regulator in atherosclerotic plaque stability. Methods and results: We profiled RNA transcript expression in patients with advanced atherosclerotic lesions from the Biobank of Karolinska Endarterectomies (BiKE). By microarray analysis, lncRNA MIAT was identified as one of the most highly up-regulated non-coding RNAs in carotid plaques compared to iliac artery controls, which was confirmed by qRT-PCR and in situ hybridization. Additional in silico analysis indicated a substantial positive correlation of MIAT with markers of inflammation, apoptosis and matrix degradation in carotid plaques. Experimental knock-down of MIAT, utilizing site-specific antisense oligonucleotides (LNA-GapmeRs) not only markedly decreased proliferation and migration rates of cultured human carotid artery smooth muscle cells (hCASMCs), but also increased their levels of apoptosis. In addition, MIAT inhibition significantly impaired oxidized LDL (oxLDL) uptake of murine peritoneal as well as human monocyte-differentiated macrophages in vitro. In contrast, induction of MIAT expression by lipoprotein-a (LPa) treatment, displayed the opposite effect. Conditioned medium from macrophage cultures after MIAT knock-down substantially decreased hCASMC proliferation, indicating a potential involvement of MIAT in macrophage-SMC interactions during advanced stages of atherosclerosis. Conclusion: The lncRNA MIAT is a novel regulator of cellular processes in atherosclerosis and plaque stability, which influences SMC proliferation and apoptosis and interacts with disease-triggering macrophages.