Deciphering aquaporin-4's influence on perivascular diffusion indices using DTI in rat stroke studies

Area of Science:

• Neuroscience
• Medical Imaging
• Biochemistry

Background:

• Cerebral ischemia, a major cause of stroke, disrupts brain fluid dynamics.
• The glymphatic system, crucial for waste clearance, is impaired following ischemic events.
• Aquaporin 4 (AQP4) polarization is implicated in glymphatic dysfunction after brain injury.

Purpose of the Study:

• To investigate dynamic changes in the perivascular space diffusion index (ALPS) post-cerebral ischemia in rats.
• To assess the relationship between ALPS and aquaporin 4 (AQP4) polarization following ischemic stroke.
• To evaluate ALPS as a potential imaging biomarker for glymphatic pathway function after ischemia.

Main Methods:

• Transient middle cerebral artery occlusion (tMCAO) model in rats.
• Diffusion tensor imaging (DTI), T2-weighted imaging (T2WI), and susceptibility-weighted imaging (SWI) at multiple time points (1-28 days).
• Immunofluorescence analysis for AQP4 and glial fibrillary acidic protein (GFAP) in brain tissue.

Main Results:

• Ischemic rats showed significantly reduced ALPS index, particularly ipsilaterally.
• ALPS demonstrated an initial decrease at day 1 post-ischemia, with recovery by days 14 and 28.
• AQP4 polarization changes mirrored ALPS index trends, indicating a concordant relationship.

Conclusions:

• The ALPS index serves as a sensitive indicator of AQP4-mediated glymphatic pathway function after cerebral ischemia.
• A significant decline in glymphatic function is observed in the hyperacute phase, followed by notable recovery in the early chronic phase.
• ALPS imaging may offer valuable insights for developing novel therapeutic strategies for stroke.