Vascular Ultrasound for In Vivo Assessment of Arterial Pathologies in a Murine Model of Atherosclerosis and Aortic Aneurysm

Figure 1. ApoE−/− mice were fed a high-cholesterol Western diet for 12 weeks to induce atherosclerosis (A). Picrosirius Red-stained aortas were visualized in brightfield and polarized light for collagen quantification (B). Binarization by splitting red and green channels was utilized to separate collagen (red) and non-collagen proteins (green). White pixels in the binarized images were counted to determine total collagen within the samples. Paravertebral view in B-Mode of the abdominal aortas in control (C) and ApoE−/− mice after 28 days of Ang II infusion (D); arrows indicate abdominal aortic aneurysm). Longitudinal images of the aorta were acquired. Borders of the vessel wall were defined in VevoVasc 1.2 software, and movement of lumen-intima border (E), ventral (green), and dorsal (yellow) outer vessel wall were traced by speckle tracking (F). Maximum diameter (G), intima–media thickness (H), pulse-wave velocity (I), wall distensibility (J), and global radial strain (K) of the carotid arteries are presented for Ang II-infused ApoE−/− mice and control animals; n = 5–7. Scale bar: 200 µm.

Figure 2. Angiotensin II (Ang II) was infused via osmotic minipumps for 28 days to provoke formation of abdominal aortic aneurysm in ApoE−/− mice (A). Segments of the carotid artery were examined from its origin to carotid bifurcation ((B) longitudinal acquisition of carotid artery). Pulse wave velocity (PWV) was examined in M-mode, measuring time differences in vessel excursion in different segments of the carotid artery (C). Vessel demarcation was performed at the luminal and adventitial sites. Distensibility and strain analysis were performed by speckle tracking using the VevoVasc software (D). Results for intima–media thickness (E), PWV (F), wall distensibility (G), and global radial strain (H) of the carotid arteries are presented for Western diet-fed ApoE−/− mice and control animals; n = 4–5.

Figure 3. Representative images of control and AAA mice in brightfield and polarized light (A) with histological (B) and sonographic (C) cross-section of AAA region. Collagen content (D) and area (E) of the tunica media and collagen content of the tunica adventitia (F) as assessed by automated analysis of Picrosirius Red-stained cross-sections. Correlation of media collagen content with intima–media thickness (G) and of media area with intima–media thickness (H), global radial strain (I), and distensibility (J) as assessed by high-resolution ultrasound. Scale bars: 200 µm (left panel) and 100 µm (right panel); n = 4.

Figure 4. Aortic sections of ApoE−/− mice fed a Western diet and controls were stained with Picrosirius Red, and collagen content was visualized in polarized light (A). Representative images show collagen content (B) and area (C) of the tunica media and collagen content of the tunica adventitia (D) as assessed by automated image analysis. Correlation of media collagen content with pulse wave velocity (E) and global radial strain (F) and of media area with distensibility (G) or global radial strain (H) as assessed by high-resolution ultrasound. Scale bars: 200 µm (left panel) and 100 µm (right panel); n = 4–5.