Several hundred small RNAs called microRNAs (miRNAs) have been identified and characterized from various organisms, including humans. In humans, some of these miRNAs have been found to regulate (patho)physiologic conditions such as tumor progression/regression, cholesterol and glucose homeostasis, etc. In this report, researchers from the National University of Singapore present data on the miRNAs expressed under ischemic conditions in both the brain and blood of rats subjected to middle cerebral artery occlusion (MCAo).
Sprague-Dawley rats subjected to MCAo were reperfused for either 24 or 48 hours, and both blood and brain samples were harvested. miRNA expression profiling and oligonucleotide microarray were carried out by LC Sciences, and the data were validated by quantitative real-time polymerase chain reaction and correlated with published data on protein and gene expression in MCAo rats.
The researchers report here for the first time the involvement of miRNA regulation in brain pathogenesis associated with MCAo. Comparison with the corresponding DNA microarray data revealed that the target mRNA expression is correlated with the regulation of miRNA. They have also provided evidence that some of the miRNAs that are highly expressed in the ischemic brain can be detected in blood samples. Further studies are needed to evaluate the possible use of miRNAs as biomarkers in stroke and related pathologies.
Hierarchical clustering analysis of 236 miRNAs expressed in the MCAo rat brain and blood with average linkage and euclidean distance as the similarity measure. Green indicates downregulation and red, upregulation. Reperfusion time points (24 and 48 hour) at which the brain and blood samples were collected are also noted. For both times, MCAo was maintained for 60 minutes. Each miRNA listed was detected as significantly and differentially expressed between the normal and ischemic brain. Heat map and dendrogram for miRNA profiles of (a) brain samples only and (b) transcripts detected in both brain and blood samples are indicated. c, Venn diagram illustrating the miRNAs detected in the brain and blood.
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Reference
Lim KY, Jeyaseelan K. (2008) MicroRNA Expression in the Blood and Brain of Rats Subjected to Transient Focal Ischemia by Middle Cerebral Artery Occlusion. Stroke 39(3), 959-66. [article]