Introduction: Atherosclerotic plaque vulnerability and subsequent rupture are mediated by alterations in miRNAs that promote inflammation and fibrous cap thinning, leading to an acute ischemic stroke. Release of these miRNAs from the plaque tissue into the circulation may provide a miRNA profile that serves as a biomarker panel to identify the vulnerable patient at greatest risk of plaque rupture.
Methods: Using RNA-Seq methodology, serum microRNA content was compared between patients undergoing carotid endarterectomy (CEA) for 2 distinct clinical phenotypes: patients without previous neurological events but high-grade carotid stenosis (asymptomatic, n=5), and patients with an acute neurological event within 5 days of the CEA (urgent, n=7). Differential expression of miRNAs was performed using the R statistical software and the DESeq2 package.
Results: A total of 695 miRNAs detected in sera on RNA-Seq, 54 were significantly different between the asymptomatic and urgent groups. 22 miRNAs were decreased and 32 were increased in the serum of urgent patient’s compared to asymptomatic patients (adjusted p-value < 0.05). Of these miRNAs, miR-21, miR-486, miR-23b, miR-27b, and let-7f were selected for validation as a biomarker panel based on a prior association with vascular disease. A pilot study (n= 6 asymptomatic and 6 urgent) measuring these miRNAs demonstrated that while miR-486 was detectable in all samples and exhibited a 9.4-fold increase (p < 0.10) in the urgent group, the other miRNAs were only detected in a fraction of the samples (33 - 75%). Furthermore, miR-486 alone did not exhibit characteristics of a good indicator of ischemic stroke. A score normalizing the expression of miR-486 to the mean expression of the detectable miRNAs from this panel, did yield a promising C-statistic (0.97 ± 0.08, p < 0.01), suggesting its potential as an indicator of an acute ischemic event.
Conclusion: Carotid plaque rupture resulting in an acute ischemic event is associated with alterations in the profile of circulating miRNAs and these may be useful as biomarkers of ischemic stroke. Our pilot data suggest that the development of a score based on a panel of circulating miRNAs may allow for the diagnosis of patients experiencing plaque rupture and an acute ischemic stroke.