Related Experiment Video
Updated: Jun 9, 2026
Monitoring Blood-Brain Barrier Opening in Rats with a Preclinical Focused Ultrasound System
Published on: September 13, 2024
A temporal study of ultrasound contrast agent-induced changes in capillary density
Chenara A Johnson1, Sandhya Sarwate, Rita J Miller
1Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Objective:
The ability of ultrasound (US) and ultrasound contrast agents (UCAs) to induce angiogenesis has been explored as a means of restoring blood flow to ischemic muscle. Because UCAs demonstrate an increasing percentage of collapse cavitation with increasing US pressure (Pr), this study sought to explore the effects of a US Pr that produces 100% collapse cavitation, determine the capillary density changes, and determine the time point of angiogenic rebound in a normal animal model.
Methods:
Using a 1-MHz focused transducer and a peak rarefactional US Pr of 3.8 MPa, rat gracilis muscles were exposed to US, and bioeffects were assessed. Capillary density, as a measure of angiogenesis, was examined. As an additional measure, inflammatory cells were quantified via a color threshold analysis to detect the presence of CD31 and CD34 as a percentage of the total section on stained slides. Six groups (0, 3, 6, 13, 20, and 27 days postexposure [DPE]; n = 3 each) and 5 cage controls were used to characterize the angiogenic response.
Results:
Ultrasound-UCA treatment caused the capillary density to decrease acutely (0 DPE) by 70% and inflammatory cells to increase by up to 250%. The angiogenic rebound was observed at 3 DPE but did not return to control levels by 27 DPE, suggesting an incomplete healing response.
Conclusions:
Capillary destruction and inflammation played an important role in the angiogenic response induced by US-UCA. Exposure that causes 100% collapse cavitation causes capillary destruction from which normal rats are unable to recover and suggests a nontherapeutic effect.
