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

Abstract

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.