Abstract 14914: VEGFR2 (Flk-1+/-) Gene Knockout Leads to Reduced Angiogenesis, Ventricular Dysfunction, and Alterations in Micro-RNA Profile Following Myocardial Infarction
Introduction: The vascular endothelial growth factor (VEGF) and its receptors (VEGFR1 and VEGFR2) are essential for angiogenesis and maintenance of blood vessel integrity. We explored the effects of heterozygous silencing of VEGFR2 (FLK-1 KO) on myocardial angiogenesis, ventricular function, and miRNA expression in a murine knockout model.
Methods: FLK-1 KO (n=30) and WT (n=30) animals underwent permanent left descending arterial (LAD) ligation (MI) or sham surgery. Animals were divided into four groups: (1) WTSHAM (2) WTMI (3) KOSHAM, and (4) KOMI. miScript miRNA PCR array was performed 24 hours after MI. Immunohistochemical analysis for capillary density and myocardial fibrosis as well as functional assessment of cardiac function with echocardiography, was done 30 days after MI.
Results: Post-infarction, systolic function showed significant reduction of ejection fraction and fractional shortening in KOMI group compared to WTMI [EF (28.21±1.02 (n=6) vs. 37±0.71% (n=6), p<0.05) and FS (13.24±0.52 (n=6) vs. 17.94±0.39% (n=6), p<0.05)]. We also observed decreased capillary density [2048±98.84 (n=6) vs. 2443±69.84 (n=9), p<0.05] in KOMI compared to WTMI. Infarct scar extension and the thinning of the infarct and myocardial fibrosis measured by picrosirrus red staining were more evident in the KOMI compared to WTMI (17.51±1.09 (n=6) vs. 8.37±0.79% (n=6), p<0.05). Disruption of Flk-1 (KOMI) induced measurable changes in miRNA profile compared to the corresponding WT group. Out of 41 differentially regulated miRNAs found in KOMI, miR-21, miR-150, miR-92a, miR-106B play key roles in the regulation of angiogenesis and miR-9, miR-15a, miR-15b, miR-182, miR-503 are known to regulate cell death and survivability. These, miRs are the important targets of VEGFR2/Flk-1 through which VEGF induces pro-angiogenic and cardioprotective activities. More studies are warrented to understand the role of individual miRNAs in angiogenesis and for the treatment of ischemic heart disease.
Conclusion: Our study, for the first time shows the disruption of the Flk-1 receptor in a murine MI model causes impaired angiogenesis, increased fibrosis and reduced cardiac function presumably via the modulation of these identified miRNAs and their respective target genes.
- © 2012 by American Heart Association, Inc.