Tissue structure and inflammatory processes shape viscoelastic properties of the mouse brain

Area of Science:

• Neuroimaging
• Biophysics
• Immunology

Background:

• Magnetic resonance elastography (MRE) quantifies tissue mechanical properties (viscosity, elasticity).
• Previous studies showed reduced brain viscoelasticity in multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE).
• Mechanisms underlying altered brain viscoelasticity in disease remain unclear.

Purpose of the Study:

• Investigate regional differences in native mouse brain viscoelasticity.
• Determine how viscoelastic properties change during chronic EAE.
• Examine the role of interferon-gamma (IFN-γ) in EAE-associated brain mechanical alterations.

Main Methods:

• Utilized 7T animal MRI scanner for sagittal plane brain scans.
• Analyzed anterior (cerebral) and posterior (cerebellar) regions separately.
• Combined MRE with contrast-enhanced MRI, histopathology, and gene expression analysis.

Main Results:

• Healthy mouse cerebellum exhibits lower viscoelasticity (is "softer") than the cerebrum.
• Wild-type mice with EAE showed no significant changes in brain viscoelasticity.
• IFN-γ(-/-) mice with more severe EAE displayed altered brain elasticity, correlating with F4/80 gene expression (macrophage/microglia marker).

Conclusions:

• MRE can differentiate viscoelastic properties between distinct brain anatomical structures.
• MRE detects disease-associated mechanical alterations in the brain in vivo.
• A link exists between neuroinflammation and changes in brain mechanical properties, particularly in IFN-γ deficient models.