Author + information
- Christoph Liebetrau, MD∗ (, )
- Helge Möllmann, MD,
- Christian Troidl, PhD and
- Holger Nef, MD
- ↵∗Department of Cardiology, Kerckhoff Heart and Thorax Center, Benekestrasse 2-8, 61231 Bad Nauheim, Germany
We read with great interest the letter by Dr. Mayr and colleagues regarding our work and the important topic of the effects of heparin on temporal microRNA (miRNA) profiles and the best timing of miRNA measurement after administration of heparin. Dr. Mayr and colleagues were recently able to show that both the timing of blood sampling relative to heparin dosing and the normalization procedure are critical for reliable miRNA measurements in patients receiving intravenous heparin (2,3). At this point, it can clearly be stated that heparin is not the only confounder in the setting of miRNA measurements; several factors, including different isolation protocols, blood sample type (plasma or serum), and inflammation-driven shifts in hematopoietic compartments after myocardial infarction, appear to further affect the detection of cell-free (truly circulating) miRNA (4).
With reference to the letter, the baseline blood samples in our study (1) were taken before administration of heparin. Therefore, we have a true control for the comparison of miRNA concentrations after transcoronary ablation of septal hypertrophy. The transcoronary ablation of septal hypertrophy procedure itself was performed after administration of heparin (bolus 5,000 IU heparin). The miRNAs were isolated from serum samples before miRNA isolation and spiking with native cel-miR-39. The samples were treated with heparinase to minimize the influence of heparin on the miRNA measurements. Of course, we cannot entirely exclude the further existence of an effect of heparin, but pre-study tests using the heparinase protocol showed comparable results for miRNA concentrations with and without heparin. Furthermore, our results clearly show a steep increase in miR-1 and miR-133a levels (approximately a 30-fold change) within 60 min after induction of myocardial infarction. Even if heparin were to cause a 30% difference in miRNA concentrations, the difference compared with miRNA concentrations at 15 min would still be significant.
The patients in our study were without antiplatelet medication. Therefore, we can exclude the interference of this medication with the measurement of miR-21 concentrations. Nevertheless, miR-21 is known to be up-regulated in the presence of cardiac hypertrophy. Thus, an influence on this subset cannot be entirely excluded.
Although methodological issues may slightly interfere with the final miRNA measurements, our results add important information to this new field, and miRNAs may well have a future as biomarkers for myocardial ischemia.
- American College of Cardiology Foundation
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