Objective: Impaired glymphatic waste clearance function during brain aging leads to the accumulation of metabolic waste and neurotoxic proteins e. However, how the age-related glymphatic dysfunction exerts its effects on different cerebral regions and affects brain waste clearance remain unclear. Methods: We investigated alterations of glymphatic transport in the aged rat brain using dynamic contrast-enhanced magnetic resonance imaging DCE-MRI and advanced kinetic modeling.
Model-derived parameters of infusion rate and clearance rate, characterizing the kinetics of cerebrospinal fluid CSF tracer transport via the glymphatic system, were evaluated in multiple representative brain regions. Changes in the CSF-filled cerebral ventricles were measured using contrast-induced time signal curves TSCs in conjunction with structural imaging.
Results: Compared to the young brain, an overall impairment of glymphatic transport function was detected in the aged brain, evidenced by the decrease in both infusion and clearance rates throughout the brain. Enlarged ventricles in parallel with reduced efficiency in CSF transport through the ventricular regions were present in the aged brain.
While the age-related glymphatic dysfunction was widespread, our kinetic quantification demonstrated that its impact differed considerably among cerebral regions with the most severe effect found in olfactory bulb, indicating the heterogeneous and regional preferential alterations of glymphatic function. Conclusion: The robust suppression of glymphatic activity in the olfactory bulb, which serves as one of major efflux routes for brain waste clearance, may underlie, in part, age-related neurodegenerative diseases associated with neurotoxic substance accumulation.
Our data provide new insight into the cerebral regional vulnerability to brain functional change with aging. Aging is accompanied by a wide array of progressive and deteriorating changes in the brain Peters, ; Kirkwood, ; Harada et al. These broad-spectrum and complex changes occur at all levels e. Along with these gradual and subtle changes that deleteriously affect the brain, undesirable alterations with age are present in the glymphatic transport pathway Benveniste et al.
