Abstract 12973: High-Intensity Focused Ultrasound (HIFU) Promotes Angiogenesis in a Rat Model of Peripheral Arterial Disease

Abstract

Shock wave therapy (SWT) delivers single pulses of pressure to tissue, and promotes angiogenesis in animal models and humans with PAD and CAD. HIFU applies pulses of multiple pressure waves, which may be more efficient. We hypothesized that setting HIFU intensity to replicate peak negative pressures (-6 MPa) typically used for SWT would lead to greater angiogenesis. Eight week-old female Sprague-Dawley rats underwent left femoral artery excision to induce hindlimb ischemia, and the right hindlimb was used as an internal control. Rats were randomized to three groups (n=10 each): SWT (0.10 mJ/mm2), HIFU (1.054 MHz, 1 ms pulse duration), and sham therapy. Both treatments were applied at a pulse repetition frequency of 5 Hz, 200 pulses per spot, for six spots along the hindlimb. Rats were treated three times weekly for two weeks, and hindlimb perfusion was assessed with a Moor LDI Laser Doppler scanner. Compared with pre-treatment baseline (Fig 1A), HIFU improved the ratio of left:right perfusion by 23.6 ± 4.5% (mean ± SEM; Fig 1B), SWT by 17.0 ± 5.9%, and sham by 4.7 ± 3.4% (Fig 1C). Immunohistochemistry of gastrocnemius muscle was performed using anti-CD31 (PECAM) antibody, and microvascular density was quantified using ImageJ software. Both HIFU and SWT increased microvascular density in the left hindlimb (223 ± 4 and 217 ± 5 vessels/hpf, respectively) compared with sham (196 ± 7, p = 0.0001 for HIFU, p = 0.01 for SWT), but there was no significant difference between HIFU and SWT. RT-PCR was performed to examine the level of VEGF mRNA. HIFU increased left:right VEGF mRNA compared with sham (2.98 ± 0.69 vs 1.17 ± 0.23, p = 0.03), whereas SWT did not exhibit a significant change compared with sham (0.75 ± 0.20, p = 0.19). In conclusion, HIFU may be a potential non-invasive therapy for promotion of angiogenesis and reperfusion for PAD patients. Further research is needed to define a dose-response relationship of HIFU-mediated angiogenesis, and to elucidate its pro-angiogenic mechanisms.