Middle cerebral artery occlusion increases cerebral capillary permeability

Area of Science:

• Neuroscience
• Cerebrovascular Research
• Biophysics

Background:

• Middle cerebral artery occlusion (MCAO) is a common cause of ischemic stroke.
• Understanding changes in brain capillary permeability during ischemia is crucial for developing effective treatments.

Purpose of the Study:

• To determine the regional blood-to-brain transfer coefficient of alpha-aminoisobutyric acid after MCAO.
• To measure cerebral regional capillary surface area in ischemic and contralateral cortex.
• To calculate and compare capillary permeability and permeability-surface area product between ischemic and contralateral regions.

Main Methods:

• Rats underwent MCAO, and alpha-aminoisobutyric acid transfer coefficient was measured.
• Alkaline phosphatase staining and fluorescein isothiocyanate-dextran were used to assess total and perfused capillary surface area.
• Extraction fraction, permeability-surface area product, and capillary permeability were calculated using established and novel methods.

Main Results:

• The transfer coefficient of alpha-aminoisobutyric acid was significantly higher in the ischemic cortex (10.6 +/- 2.3) than the contralateral cortex (6.5 +/- 1.0).
• Perfused capillary surface area was markedly lower in the ischemic cortex (141 +/- 31 cm2/cm3) compared to the contralateral cortex (426 +/- 32 cm2/cm3).
• Capillary permeability to small molecules increased more than four-fold in the ischemic cortex one hour after MCAO.

Conclusions:

• MCAO leads to a significant increase in brain capillary permeability.
• The reduced perfused capillary surface area in the ischemic region contributes to altered transport dynamics.
• These findings provide novel insights into the biophysical changes of brain capillaries during acute ischemic stroke.