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Microvascular Embolism Mouse Model for In Vivo Two-photon Microscopy Using Fluorescent Polystyrene Microspheres
Published on: November 21, 2025
Do microemboli reach the brain penetrating arteries?
Lei Zhu1, Angelika Hoffmann, Max Wintermark
1Vascular Surgery Service, San Francisco Department of Veterans Affairs Medical Center, San Francisco, California 94121, USA.
The Journal of Surgical Research
|January 21, 2012
Summary
The rat brain shows significant tolerance to microemboli, with larger particles and higher numbers causing more injury. Arteriovenous (AV) fistulae do not significantly contribute to this tolerance, as most microemboli lodge in the pial vasculature.
Area of Science:
- Neuroscience
- Cerebrovascular Research
- Ischemia Models
Background:
- Microembolic obstruction of brain arteries can cause ischemia due to their "end artery" nature.
- Mammalian brains exhibit remarkable tolerance to experimental microembolization, with ischemia only occurring after substantial particulate injection.
- Potential explanations for brain tolerance include particulate margination in pial vasculature or escape via arteriovenous (AV) fistulae.
Purpose of the Study:
- To investigate the tolerance of the rat brain to microemboli of varying sizes and numbers.
- To determine the role of arteriovenous (AV) fistulae in the clearance of microemboli from the cerebral circulation.
- To elucidate the distribution and impact of microemboli within the brain's vasculature.
Main Methods:
- Injection of fluorescent microspheres (20, 45, 90 μm) into Sprague-Dawley rats to assess injury and infarction.
- Quantification of microsphere fluorescence in brains and lungs to determine distribution.
- 2T-MRI with SPIO-labeled microthrombi to locate larger microemboli in the pial and penetrating vasculature.
Main Results:
- Minimal injury or infarction observed with 20 μm microspheres, even at high doses.
- Limited small areas of injury and infarction occurred with 45 μm microspheres.
- 93%-96% of microspheres remained in the brain, with approximately 40% of microemboli found on the brain surface.
Conclusions:
- The rat brain demonstrates significant tolerance to microemboli, influenced by particle size and quantity.
- Arteriovenous (AV) connections are not a primary mechanism for microemboli clearance in this model.
- While 40% of microemboli lodge superficially, the remaining 60% enter penetrating arteries with limited ischemic விளைவுகள்.
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