Ultrasound-targeted microbubble destruction-mediated Ang1 gene transfection improves left ventricular structural and sympathetic nerve remodeling in canines with myocardial infarction

BACKGROUND: The present study aimed to determine whether ultrasound-targeted microbubble destruction (UTMD)-mediated angiopoietin 1 (Ang1) gene transfection can improve angiogenesis and potentially reverse left ventricular (LV) structural and sympathetic nerve remodeling in canines with myocardial infarction (MI). METHODS: Thirty dogs were randomly divided into groups (n=10/group) as follows: the MI group (MI dogs without UTMD treatment), the UTMD group (MI dogs with UTMD-mediated negative control plasmid treatment), and the UTMD-Ang1 group (MI dogs with UTMD-mediated Ang1 plasmid treatment). LV dimensions, systolic function, and synchrony were used to reflect the structural remodeling. The density of tyrosine hydroxylase (TH)- and growth-associated protein 43 (GAP43)-positive nerve fibers were calculated to assess the sympathetic nerve remodeling. RESULTS: One month after treatment, the UTMD-Ang1 group showed lower LV end-diastolic dimension (LVEDD: 31.2±2.3 mm) and higher LV ejection fraction (LVEF: 44.6%±4.3%) than the MI group (LVEDD: 34.5±2.2 mm, t=2.282, P=0.014; LVEF: 37.3%±3.1%, t=3.718, P=0.003) and the UTMD group (LVEDD: 34.1±2.8 mm, t=2.264, P=0.040; LVEF: 39.3%±4.5%, t=2.408, P=0.030). LV synchrony was higher in the UTMD-Ang1 group compared with the MI group by 2-dimensional speckle-tracking echocardiography. Angiogenic density was higher in the UTMD group than the MI group but was highest in the UTMD-Ang1 group according to immunohistochemistry of CD31 and α-smooth muscle actin staining. The density of TH- and GAP43-positive nerve fibers were decreased in the UTMD-Ang1 group (TH: 1,928.2±376.6 μm(2)/mm(2); GAP43: 2,090.8±329.2 μm(2)/mm(2)) compared with the MI group (TH: 2916.5±558.4 μm(2)/mm(2), t=4.069, P=0.001; GAP43: 3,275.4±548.6 μm(2)/mm(2), t=5.153, P=0.000) and the UTMD group (TH: 2,552.7±408.1 μm(2)/mm(2), t=3.181, P=0.007; GAP43: 2,630.5±419.3 μm(2)/mm(2), t=2.863, P=0.013). The relative Ang1 and sarcoplasmic reticulum Ca(2+)-ATPase 2a protein levels were significantly higher in the UTMD-Ang1 group than the UTMD and MI groups by Western blot, while the phospholamban levels exhibited the opposite trend. Plasma norepinephrine and N-terminal pro-B-type-natriuretic peptide were significantly reduced in the UTMD-Ang1 group from day 1 to 1 month after MI. CONCLUSIONS: UTMD-mediated Ang1 transfection can promote angiogenesis, reverse LV structural and sympathetic nerve remodeling, and improve LV synchrony after MI.