Abstract 172: Circulating Mirna Profiles Discriminate Stroke Severity Associated With Age and Sex

Abstract

Background: Age and sex have significant effects on stroke outcomes, however, the precise mechanisms by which these factors affect stroke pathophysiology remains unclear. Small non-coding RNA (miRNA) found in circulation have been used successfully as biomarkers and mechanistic targets for chronic and acute diseases. The present study investigated the impact of age and sex on microRNA expression following ischemic stroke. Methods: Adult (6 mo) and middle aged (11-12 mo) female and male rats were subject to middle cerebral artery occlusion (MCAo) using Endothelin-1. Blood samples were drawn at 2d and 5d post stroke. All animals were terminated at 5d and the brains processed for infarct analysis by standard histological procedures. Total RNA isolated from serum was subject to QPCR amplification for serum microRNAs (168) and 7 reference microRNAs (Exiqon focus panels). Normalized miRNA values were analyzed by Genesifter program using a two-way ANOVA with Benjamini and Hochberg corrections for false discovery rates.. Results: Normalized infarct volume was significantly smaller in adult females (0.12+) as compared to middle-aged females (0.4; p<0.05), young males (0.51 ) or middle aged males (0.51. p<0.05). At 2d post stroke, 30 circulating miRNAs were differentially regulated and principal component analysis (PCA) confirmed that most of the variance was due to age. At 5d post stroke, 79 circulating miRNAs exhibited significantly different regulation, and PCA indicated that most of the variance was associated with sex. A small cohort (5) of miRNAs, miR-15a, -19b, -32, -136 and -199a-3p were found to be highly expressed in adult females compared to middle aged females, adult and middle-aged males. Predicted and experimentally validated gene targets for these 5 miRNAs analyzed for Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways revealed that the top 10 KEGG pathways (high p values, large gene numbers) were related to growth factor signaling, cell structure and MAPK signaling. Conclusion: Overall, the pattern of circulating miRNA expression suggests an early influence of age in stroke pathology, with a later emergence of sex as a factor for stroke severity. Furthermore, a small cohort of miRNAs were found to discriminate severe and mild stroke infarction.