While genomic array studies have shown that cohorts of messenger RNA (mRNA) levels in blood can be used to delineate between stroke types, there are some drawbacks with this approach. Not least the relatively poor stability of mRNA in blood. We are exploring the utility of circulating microRNAs (miRNAs) as biomarkers of ischemic stroke. miRNAs are small (∼22 nt) evolutionarily conserved single-stranded, non-coding RNA species that function as potent regulators of gene expression. They suppress gene expression by hybridizing with the 3’ untranslated region (3’UTR) of target messenger RNAs (mRNAs) and trigger mRNA degradation and/or translational repression. miRNAs are contained within several cellular and non-cellular compartments in the blood and are more stable in the bloodstream than messenger RNAs.
Fifteen patients diagnosed with acute ischemic stroke (initial National Institutes of Health Stroke Scale of 5 or greater) and six no-stroke controls were enrolled in this study. Three blood samples were drawn from each patient into PAXgene tubes. Sample 1 was drawn within 5 hours of stroke, before IV tissue plasminogen activator t-PA treatment. Sample 2 was drawn at 24 hours following stroke onset, after IV rt-PA, thrombectomy and IA rt-PA. Sample 3 was drawn at 7 days post-stroke. RNA quality and concentration was determined and cDNA libraries generated to perform deep sequencing analysis on a SOLiD Sequencer.
Our data strongly suggests that miRNA expression profiles in peripheral blood are significantly altered in patients with ischemic stroke compared with control patients. We found 23 miRNAs that are differentially expressing in ischemic patients versus controls. Fifteen of these miRNAs were significantly decreased in ischemic stroke, while 8 were significantly increased in ischemic stroke. Moreover, comparison of the miRNA expression levels in the blood of a patient presenting with signs of ischemic stroke, but who was diagnosed with a transient ischemic attack (TIA) and released without treatment, grouped with control patients upon analysis.
We have convincing preliminary data showing that miRNA expression profiles in peripheral blood following ischemic stroke are significantly altered.