Role and therapeutic potential of non-coding RNAs in vascular remodeling and atherosclerotic plaque formation

Abstract: Atherosclerosis and its clinical sequelae remain a world leading cause of disease and death, despite recent advances in primary and secondary prevention. The silently progressive character of the disease, in combination with the influence of individual patient characteristics, makes acute events difficult to predict and prevent. There is a need for (1) noninvasive, accurate diagnostic methods and (2) individually tailored therapies, in order to provide effective treatment whilst avoiding unnecessary interventions and iatrogenic damage. In the search for novel detection methods and drugs, non-coding RNA has emerged as a class of important biological regulators, being crucially involved in virtually every cellular process. We show that patients at risk for cardiovascular events display characteristic non-coding RNA patterns and could be treated with RNA interference (RNAi) therapy, targeting and normalizing previously ‘undruggable’ physiological disruptions. In order to measure up to these high expectations, findings from basic non-coding RNA research need to be applied in (pre-)clinical studies. MicroRNAs (miRNA, miR) have been demonstrated to be modifiers of cardiovascular disease via posttranscriptional inhibition of messenger RNA. In this thesis, in vitro as well as in vivo modulation of clinically relevant miRNAs are presented as a therapeutic approach to alter vascular cell behavior and induce reparative arterial remodeling in three cardiovascular diseases (stroke, abdominal aortic aneurysm (AAA) and radiation-induced vasculopathy). In two different mouse models of AAA, we showed that miR-24 treatment hampers AAA expansion. Cell and human tissue experiments demonstrated a positive effect of miR-24 that could be attributed to an inhibitory action of this miRNA on chitinase 3-like 1, a marker of macrophage-induced inflammation. In AAA, a disease for which screening has been suggested but fails to meet socioeconomic demands, we are the first to present a sufficiently powered biomarker study, where miR-99b, detected in the circulation, could predict aneurysm expansion and rupture risk. In patients with carotid artery atherosclerosis at risk for stroke, miR-210 was decreased in the atherosclerotic fibrous cap. In vivo experiments of murine carotid injury and plaque rupture showed that low expression of miR-210 was associated with fibrous cap smooth muscle cell apoptosis through adenomatous polyposis coli, and that miR-210 treatment could prevent carotid plaque rupture in mice. In chronic arterial inflammation secondary to radiotherapy, miR-29b deregulation demonstrated an adverse inflammatory and fibrotic response, which in mice could be corrected with miR-29b mimic therapy, partly through a restored inhibition of miR-29b targets pentraxin 3 and dipeptidyl-peptidase 4. Our approaches have not only revealed possible diagnostic and therapeutic use of non-coding RNAs, but have also presented us with the difficulties and limitations of presenting exogenous RNA modifiers to a diseased circulatory system. Distribution, efficacy, off-target effects, and pleiotropy are issues that need to be addressed before non-coding RNAi therapy can be exploited clinically.