Role of differential microRNA 378 expression in increased pro-angiogenic activity of mobilized CD34+ progenitor cells of patients with acute ST-elevation myocardial infarction:

Rationale: Pro-angiogenic effects of mobilised bone-marrow-derived stem/progenitor cells are essential for cardiac repair after myocardial infarction. MicroRNAs (miRNA/miR) are key regulators of angiogenesis. Objective: To determine the differential regulation of angiomiRs, i.e microRNAs regulating neovascularisation, in mobilised CD34+ progenitor cells obtained from patients with an acute ST-segment elevation myocardial infarction (STEMI) as compared to those with stable coronary artery disease (sCAD) or healthy subjects. Methods and Results: CD34+ progenitor cells were isolated from patients with STEMI (on day 0 and day 5), sCAD and healthy subjects (n=27). CD34+ progenitor cells of patients with STEMI exhibited increased pro-angiogenic activity as compared to CD34+ cells from the other groups. Using a PCR-based miRNA-array and Real-Time PCR validation we identified a profound up-regulation of two known angio-miRs, i.e. miR-378 and let-7b, in CD34+ cells of patients with STEMI. Especially, we demonstrate that miR-378 is a critical regulator of the pro-angiogenic capacity of CD34+ progenitor cells and its stimulatory effects on endothelial cells in-vitro and in-vivo, whereas let-7b up-regulation in CD34+ cells failed to proof its effect on endothelial cells in-vivo. Conclusion: The present study demonstrates for the first time a significant upregulation of the angiomiRs miR-378 and let-7b in mobilised CD34+ progenitor cells of patients with STEMI. The increased pro-angiogenic activity of these cells in patients with STEMI and the observation that in particular miR-378 regulates the angiogenic capacity of CD34+ progenitor cells in-vivo suggest that this unique microRNA expression pattern represents a novel endogenous repair mechanism activated in acute myocardial infarction. CD34+ progenitor cells from patients with acute STEMI, patients with stable CAD and healthy subjects were isolated from 60 ml of anticoagulated peripheral blood (BD Vacutainer, K2EDTA 18.0 mg) using the CD34-MicroBead-Kit (Miltenyi Biotec) according to the manufacturer’s protocol. Total RNA was isolated from CD34+ cells according to the Mini Kit (Qiagen) manufacturer’s instructions. Differential miR-expression in CD34+ cells was analysed using PCR-based miRNA profiling on Human panel I plates from Exiqon and validated using real-time PCR analysis according to miRCURY LNA™ Universal RT microRNA PCR protocol (Exiqon)