Purpose:
Despite recent progress in the management of ischemic heart disease (IHD), the number of patients with severe IHD is increasing. In this study, we aimed to develop low-intensity pulsed ultrasound (LIPUS) therapy for the treatment of IHD and to elucidate the underlying molecular mechanisms for the LIPUS-induced angiogenesis.
Methods and Results:
We first confirmed that the LIPUS up-regulated mRNA expression of vascular endothelial growth factor (VEGF) with a peak at 32-cycle in cultured human vascular endothelial cells (HUVECs). Then, we examined the in vivo effects of LIPUS in a porcine model of chronic myocardial ischemia with reduced left ventricular ejection fraction (LVEF) (n=28). The heart was treated with either sham or LIPUS (32-cycle, 20 min) at 3 different short axis levels (n=14 each). Four weeks after the therapy, LVEF was significantly improved in the LIPUS group (46±4 to 57±5%, P<0.05), whereas it remained unchanged in the control group. Capillary density and regional myocardial blood flow in the ischemic region were also increased in the LIPUS group but not in the control group. The protein expressions of VEGF, eNOS and bFGF in the ischemic area were enhanced in the LIPUS group compared with the control group. To further examine the signaling pathways responsible for the LIPUS-induced angiogenesis, HUVECs were transfected with siRNA or scrambled siRNA of either β1 integrin or caveolin-1. Knockdown of either β1 integrin or caveolin-1 with siRNA suppressed the LIPUS-induced up-regulation of VEGF. siRNA-mediated suppression of either focal adhesion kinase (FAK) or Fyn also inhibited the LIPUS-induced up-regulation of VEGF. Knockdown of these molecules with siRNA was confirmed with real-time PCR.
Conclusions:
These results suggest that the LIPUS therapy is promising as a new, non-invasive therapy for IHD and that β1 integrin and caveolin-1 may be involved in underlying molecular mechanisms for the beneficial effects of the LIPUS.
Low-Intensity Pulsed Ultrasound Induces Angiogenesis and Ameliorates Left Ventricular Dysfunction in a Porcine Model of Chronic Myocardial Ischemia
