Mapping Blood-Brain-Barrier Dysfunction with Water Permeability

Published on April 8, 2022

Think of your brain as a super-exclusive club. The blood-brain-barrier (BBB) acts like the bouncer, selectively allowing certain substances in and keeping others out. But sometimes, as we get older, the bouncer gets a bit lax and starts letting in more than it should. That’s where BBB dysfunction comes in. Researchers have found that BBB water exchange rate, measured using specialized MRI techniques, is an indicator of this dysfunction. In a recent study, they used an improved MRI sequence to map the permeability of the BBB in different brain regions of adults without dementia. They discovered that the cerebral cortex had higher permeability compared to the white matter of the brain. Age was found to be a significant factor contributing to this dysfunction in various brain regions. This study not only provides valuable insights into the relationship between aging and BBB water exchange, but also opens up possibilities for developing targeted therapies for age-related brain disorders. If you’re eager to dive deeper into this fascinating research, check out the full article!

Blood-brain-barrier (BBB) dysfunction is a hallmark of aging and aging-related disorders, including cerebral small vessel disease and Alzheimer’s disease. An emerging biomarker of BBB dysfunction is BBB water exchange rate (kW) as measured by diffusion-weighted arterial spin labeling (DW-ASL) MRI. We developed an improved DW-ASL sequence for Quantitative Permeability Mapping and evaluated whole brain and region-specific kW in a cohort of 30 adults without dementia across the age spectrum. In this cross-sectional study, we found higher kW values in the cerebral cortex (mean = 81.51 min–1, SD = 15.54) compared to cerebral white matter (mean = 75.19 min–1, SD = 13.85) (p < 0.0001). We found a similar relationship for cerebral blood flow (CBF), concordant with previously published studies. Multiple linear regression analysis with kW as an outcome showed that age was statistically significant in the cerebral cortex (p = 0.013), cerebral white matter (p = 0.033), hippocampi (p = 0.043), orbitofrontal cortices (p = 0.042), and precunei cortices (p = 0.009), after adjusting for sex and number of vascular risk factors. With CBF as an outcome, age was statistically significant only in the cerebral cortex (p = 0.026) and precunei cortices (p = 0.020). We further found moderate negative correlations between white matter hyperintensity (WMH) kW and WMH volume (r = −0.51, p = 0.02), and normal-appearing white matter (NAWM) and WMH volume (r = −0.44, p = 0.05). This work illuminates the relationship between BBB water exchange and aging and may serve as the basis for BBB-targeted therapies for aging-related brain disorders.

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