Quantitative Water Permeability Mapping of Blood-Brain-Barrier Dysfunction in Aging

Aging is commonly linked to changes in brain function and structure, with the blood-brain barrier (BBB) being a key area of interest. BBB dysfunction is a known feature of aging and age-related neurological conditions like Alzheimer's disease. While BBB water exchange rate (kW) has emerged as a potential biomarker, its relationship to aging remains unclear. Prior research has shown that cerebral blood flow (CBF) declines with age, but the specific role of BBB permeability in aging is less understood. This gap motivated the need for more precise methods to map BBB water exchange rates. Existing studies have used diffusion-weighted arterial spin labeling (DW-ASL) MRI, but improvements in imaging sequences could enhance accuracy. This paper introduces a new DW-ASL sequence to better quantify BBB permeability. The study explores whether kW values vary with age and brain regions. It also investigates if kW correlates with white matter hyperintensity (WMH) volume. This work builds on prior findings but adds new insights into BBB function in aging.

The aim of this study was to evaluate BBB water exchange rate (kW) in aging using an improved diffusion-weighted arterial spin labeling (DW-ASL) MRI sequence. The researchers sought to determine if kW values differ across brain regions and whether they increase with age. They also aimed to assess if kW correlates with white matter hyperintensity (WMH) volume. This work builds on prior studies that found age-related changes in cerebral blood flow (CBF) but adds a focus on BBB permeability. The motivation stems from the need to better understand BBB dysfunction in aging and its potential as a therapeutic target. By using a newly developed DW-ASL sequence, the study aimed to improve the accuracy of kW measurements. The study also aimed to compare kW values in different brain regions, such as the cerebral cortex and white matter. The researchers wanted to determine if kW is influenced by vascular risk factors and sex. This approach allows for a more detailed mapping of BBB permeability in aging populations.

The study employed an improved diffusion-weighted arterial spin labeling (DW-ASL) MRI sequence to measure BBB water exchange rate (kW). A cross-sectional design was used with 30 adults without dementia across various age groups. Whole-brain and region-specific kW measurements were obtained using this advanced MRI technique. The researchers analyzed data from cerebral cortex, cerebral white matter, hippocampi, orbitofrontal cortices, and precunei cortices. They used multiple linear regression to assess the relationship between kW and age, adjusting for sex and vascular risk factors. Cerebral blood flow (CBF) was also measured and compared with kW values. White matter hyperintensity (WMH) volume was evaluated for correlations with kW in normal-appearing white matter (NAWM) and WMH regions. The study combined imaging data with statistical analysis to explore age-related changes in BBB function. This method allowed for precise quantification of BBB permeability across different brain regions.

The study found higher BBB water exchange rate (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). Age was significantly associated with kW 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). With cerebral blood flow (CBF) as the outcome, age was significant only in the cerebral cortex (p = 0.026) and precunei cortices (p = 0.020). The study observed a moderate negative correlation between white matter hyperintensity (WMH) kW and WMH volume (r = -0.51, p = 0.02). A similar negative correlation was found between normal-appearing white matter (NAWM) kW and WMH volume (r = -0.44, p = 0.05). These findings suggest that BBB permeability increases with age and is region-specific. The results highlight the potential of kW as a biomarker for BBB dysfunction in aging. Adjusting for sex and vascular risk factors did not diminish the significance of age-related effects.

The authors suggest that BBB water exchange rate (kW) increases with age in multiple brain regions, including the cerebral cortex, white matter, hippocampi, and precunei cortices. This finding aligns with prior studies on cerebral blood flow (CBF) and aging. The study also found that kW correlates negatively with white matter hyperintensity (WMH) volume. These results support the use of kW as a potential biomarker for BBB dysfunction in aging. The authors propose that improved diffusion-weighted arterial spin labeling (DW-ASL) MRI sequences can enhance the accuracy of BBB permeability measurements. The findings may inform future research on BBB-targeted therapies for age-related brain disorders. The authors emphasize the importance of region-specific analysis in understanding BBB changes. The study contributes to the growing evidence linking BBB permeability to aging and neurological conditions.