Altered MicroRNA Expression in Intracranial Aneurysmal Tissues: Possible Role in TGF-β Signaling Pathway

The molecular mechanisms behind the rupture of intracranial aneurysms remain obscure. MiRNAs are key regulators of a wide array of biological processes altering protein synthesis by binding to target mRNAs. However, variations in miRNA levels in ruptured aneurysmal wall have not been completely examined. We hypothesized that altered miRNA signature in aneurysmal tissues could potentially provide insight into aneurysm pathophysiology. Using a high-throughput miRNA microarray screening approach, we compared the miRNA expression pattern in aneurysm tissues obtained during surgery from patients with aneurysmal subarachnoid hemorrhage (aSAH) with control tissues (GEO accession number GSE161870). We found that the expression of 70 miRNAs was altered. Expressions of the top 10 miRNA were validated, by qRT-PCR and results were correlated with clinical characteristics of aSAH patients. The level of 10 miRNAs (miR-24-3p, miR-26b-5p, miR-27b-3p, miR-125b-5p, miR-143-3p, miR-145-5p, miR-193a-3p, miR-199a-5p, miR-365a-3p/365b-3p, and miR-497-5p) was significantly decreased in patients compared to controls. Expression of miR-125b-5p, miR-143-3p and miR-199a-5p was significantly decreased in patients with poor prognosis and vasospasm. The target genes of few miRNAs were enriched in Transforming growth factor-beta (TGF-β) and Mitogen-activated protein kinases (MAPK) pathways. We found significant negative correlation between the miRNA and mRNA expression ( TGF-β1 , TGF-β2 , SMAD family member 2 ( SMAD2 ) , SMAD family member 4 ( SMAD4 ), MAPK1 and MAPK3 ) in aneurysm tissues. We suggest that miR-26b, miR-199a, miR-497and miR-365, could target multiple genes in TGF-β and MAPK signaling cascades to influence inflammatory processes, extracellular matrix and vascular smooth muscle cell degradation and apoptosis, and ultimately cause vessel wall degradation and rupture.