Abstract
miRNA are post-transcriptional gene regulators which modulate RNA silencing and gene expression. In chronic myocardial ischemia, miRNA are altered and dysregulated. MiR92a inhibition in a mouse model of LAD occlusion led to improved neovascularisation and reduced infarct sizes. We aimed to investigate this therapeutic effect of miR92a- inhibition in a pig model of chronic myocardial ischemia. Methods: In pigs (n=5/group) reduction stent graft implantation in the circumflex artery led to a gradual occlusion of the vessel within 28 days (d28) after intervention. Using selective pressure-regulated retroinfusion the nucleic acid-modified antisense miR92a (LNA-92a; 5 mg/KG heart weight) was injected 28 days post implantation. The global myocardial function (Ejection Fraction (EF)) and the left end-diastolic pressure (LVEDP) were obtained at day 28 and 56. At day 56 after stent implantation regional myocardial function (subendocardial segmentshortning) as well as post mortem angiographies for collateral growth were analyzed. For the histological quantification the ischemic tissue was stained for PECAM-1 positive cells (capillaries) and for NG2- positive cells (vessel maturation, pericyte coverage). Results: The regionally applied locked nucleic acid-modified anti-sense miR-92a significantly reduced miR-92a expression in the heart and enhanced capillary coverage in the ischemia. Improved collateral growth (3±1 control vs. 6±1 in LNA-92a treated hearts) and distal perfusion of the occluded coronary artery (Rentrop score: 1.3±0.2 control vs. 2.4±0.2 in LNA-92a treated hearts) was seen after miR-92a inhibition. Moreover the increased LVEDP at day 28 (control: 16±1 mmHg vs. LNA-92a 15±1mmHg) was reduced after regional miRNA-92a inhibition (control: 16±1 mmHg vs. LNA-92a 15±1mmHg) and EF clearly increased after LNA-92a application (39±4% vs. 25±2 % in control). Regional myocardial function, obtained in the ischemic area under increased heart rate, was significantly improved after miR-92a inhibition (SES at hear rate 150bpm: 7±3 % of non-ischemic in control vs. 70±11 %% of non-ischemic in LNA-92a treated animals). Conclusion: Even single application of LNA-92a was able to reduce ischemia dependent impaired myocardial function
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