Researcher(s)
- Meggan Bischoff, Neuroscience, University of Delaware
Faculty Mentor(s)
- Curtis Johnson, Biomedical Engineering, University of Delaware
Abstract
Several studies have shown that human brain tissue becomes softer with age. Likewise, tissue softening is a hallmark of neurodegenerative disease such as Alzheimer’s disease. As a result, researchers have begun using advanced imaging techniques such as Magnetic Resonance Elastography (MRE) to detect changes in brain biomechanics associated with disease. Rodent models have helped advance our understanding of MRE’s ability to detect disease-related changes, and how neurobiology and pathology manifest as changes in tissue mechanics, but little is known about how aging alone affects brain biomechanics in rats. Therefore, we investigated age-related changes in the mechanical properties of the rat brain to establish a model of brain aging using MRE. We hypothesized that rat brains would become less stiff and exhibit an increased damping ratio over time, similar to trends in humans.
We used MRE to scan 15 female rats aged 3 months (cohort 1) and 15 female rats aged 12 months (cohort 2). Brain stiffness and damping ratio (a measure of relative viscosity) were calculated from MRE tissue deformation measurements to quantify biomechanical changes across the aging rat brain. An unpaired t-test between the two cohorts revealed that the older cohort had significantly higher whole brain stiffness compared to the younger group (p < 0.001; µyoung= 6.37 kPa; µold = 7.39 kPa). The damping ratio was significantly lower in the older group (p = 0.02; µyoung= 0.281; µold = 0.259).
Contrary to our hypothesis and trends in human data, older rats exhibited stiffer brains with lower damping ratios. These findings suggest aging in rat brains may follow a distinct biomechanical trajectory from humans. Differences in inherent tissue microstructures between humans and rats may explain these unexpected trends. Establishing this distinction is critical for accurately modeling age-related neurological changes in rodents using MRE. Future studies will examine region-specific changes and biological contributors such as cellular composition, hormones, and sex.