Abstract
BackgroundDespite a genomic revolution in biological sciences, clinical medicine has yet to integrate diagnostics based upon gene expression into practice. While commonly used plasma protein assays rely on organ-specific origins, nearly all nucleic acid in whole blood is derived from white blood cells limiting their utility to diagnose non-immune disorders. The aim of the study was to use cell-free plasma to define circulating messenger RNA sequences diagnostic of acute organ injury, including myocardial infarction (MI) and acute kidney injury (AKI).MethodsIn healthy human subjects (N = 4) and patients with acute MI (N = 4), we characterized the concentration and nature of circulating plasma RNA through spectrophotometry and chromatography. Through reverse transcriptase polymerase chain reaction (RT-PCR) of amplicons up to 939 base pairs, we determined whether this mRNA was intact but of insufficient quantity to sequence. In mice, we induced an acute anterior myocardial infarction through 1 h of ischemia followed by reperfusion of the left anterior descending (LAD) artery. We compared the cell-free plasma transcriptome using cDNA microarray in sham-operated mice compared to ischemia upon reperfusion and at 1 and 4 h. To determine organ specificity, we compared this profile to acute ischemia-reperfusion of the kidney.ResultsIn humans, there is more plasma RNA in those with acute MI than in healthy controls. In mice, ischemia-reperfusion of the LAD artery resulted in a time-dependent regulation of 589 circulating mRNA transcripts with less than a 5% overlap in sequences from acute ischemia-reperfusion injury of the kidney.ConclusionsThe mRNA derived from cell-free plasma defines organ injury in a time and injury-specific pattern.Electronic supplementary materialThe online version of this article (doi:10.1186/2197-425X-2-7) contains supplementary material, which is available to authorized users.
Highlights
Despite a genomic revolution in biological sciences, clinical medicine has yet to integrate diagnostics based upon gene expression into practice
Human studies Blood samples International review board (IRB) approval was obtained for this study from the Providence Health Care IRB; written informed consent was obtained from all subjects
The final concentration of plasma RNA obtained from control subjects (N = 4) was 1.9 ± 0.1 μg/mL blood, while in patients with acute myocardial infarction (MI) (N = 4) who had plasma drawn at primary angiography, the mean concentration of plasma RNA was 6.5 ± 2.4 μg/mL blood
Summary
Despite a genomic revolution in biological sciences, clinical medicine has yet to integrate diagnostics based upon gene expression into practice. While commonly used plasma protein assays rely on organ-specific origins, most nucleic acid in whole blood is derived from white blood cells limiting their utility to diagnose non-immune disorders. The aim of the study was to use cell-free plasma to define circulating messenger RNA sequences diagnostic of acute organ injury, including myocardial infarction (MI) and acute kidney injury (AKI). Microparticles are most commonly platelet-derived, and a class of procoagulant apoptosis-marker positive (annexin V) microparticles is found [1]. In a number of vascular disease states, endothelial-derived microparticles become important [1]. Plasma-derived microparticle mRNA has been used to distinguish patients who have colon cancer from those free of the disease [5]
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