Study of Dysregulated Micrornas in Abdominal Aortic Aneurysm Tissue

Abstract

Introduction - microRNAs (miRs) are small non-coding RNA molecules that regulate protein expression (1). The initiation and progression of Abdominal Aortic Aneurysm (AAA) can be regulated by miRs (2), hence their expression in abdominal aortic tissue could be useful for the identification of novel therapeutic targets. In a previous study, we identified some dysregulated miRs in plasma of patients with AAA. In the current study we have measured the expression level of those miRs in AAA and in healthy tissues in order to elucidate their local dysregulation. Methods - We obtained abdominal aortic tissue from patients undergoing AAA open repair (N=21) and from healthy organ donors (N=8). Tissue samples were snap-frozen and stored in liquid N2. A cross section of the tissue was homogenized with the TissueLyser LT® (Qiagen), and total RNA was obtained with the miRVANA PARIS® kit (Ambion). cDNA was obtained from 10 ng of total RNA. Sixteen miRs were quantified by Real Time quantitative PCR (RT-qPCR)(Exiqon) and results (CTs) were normalized with the endogenous and stable miR 423-5p selected using RefFinder. Normalized results were adjusted in a linear regression model using the statistic software R (3.3.2 version). Results - Six miRs were significantly underexpressed in AAA vs healthy tissue. The expression of miR-1, miR-27-b-3p, miR-29b-3p, mir-133a-3p, miR-133b and miR-195-5p was 4.8 (p<0.001); 2 (p<0.001); 1.4 (p=0.018); 4.4 (p<0.001); 4.6 (p<0.001) and 1.6 (p=0.023) fold lower than healthy tissue, respectively. Furthermore, 3 miRs were overexpressed in AAA tissue. Thus, miR-146a-5p, miR-21-5p and miR-144-3p were overexpressed 5.8 (p<0.001); 1.9 (p=0.012) and 7.2 (p<0.001) times, respectively. Some targets of these dysregulated miRs are related to vascular wall integrity (COL), apoptosis (PTEN) or inflammation (IRAK1) pathways. Conclusion - Our preliminary study confirms the dysregulation of 9 miRs in AAA tissue. Our results support the role of these miRs in the development of AAA. Some of the target proteins of these dysregulated miRs are involved in several mechanisms related to vascular pathologies. Thus, miR-29b is involved in collagen deposition and fibrosis, miR146a-5p in inflammation and apoptosis and miR-133b or miR-21-5p in inflammation, apoptosis and cellular proliferation and differentiation (3). However, the role of other miRs such as miR-27b-3p or miR-144-3p in AAA development is yet to be elucidated. The validation of our results in a larger cohort could reveal these miRs as therapeutic targets in AAA.