MicroRNA expression profiles in abdominal aortic aneurysms: A systematic review of potential diagnostic and prognostic biomarkers.

Background: MicroRNAs (miRNAs) are critical regulators of vascular biology and have been implicated in the pathogenesis of abdominal aortic aneurysm (AAA). However, the diversity of study designs and heterogeneous findings has limited their clinical translation. This study aimed to systematically review available evidence on miRNA expression in AAA, both in aortic tissue and circulating blood, and to explore their potential regulatory pathways. Methods: We conducted a comprehensive literature search across five databases -PubMed, Scopus, Embase, Web of Science (WoS), and EBSCO - up to June 2025, following the PRISMA guidelines. Eligible studies included those reporting differential miRNA expression in human AAA samples, whether tissue or blood, with validated results. Data on expression direction, sample type, pathways, and target genes were extracted and synthesized. Results: A total of 39 studies were included reported diagnostic performance varied substantially across studies. Circulating miRNAs in AAA patients exhibited distinct dysregulation patterns, reflecting disease-associated vascular and inflammatory processes. Key Up-regulated miRNAs included miR-21, miR-146a, miR-155, miR-1281, and miR-34a, while prominent Down-regulated candidates comprised miR-15a, miR-29, miR-150-5p, miR-27a-3p, and let-7 family members. These alterations were observed in plasma, serum, and specific cell types, suggesting possible utility as non-invasive biomarker candidates for AAA detection and disease monitoring, although external validation remains limited. Conclusion: Our systematic review highlights a panel of consistently dysregulated miRNAs in AAA, with roles in inflammation, extracellular matrix remodeling, and vascular cell regulation, and they may represent promising candidates for future screening and diagnostic evaluation, pending standardization and prospective validation.