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

Background: This study aimed to evaluate the dynamic changes of the perivascular space diffusion index (index for diffusivity along the perivascular space, ALPS) and its relationship with aquaporin 4 (AQP4) polarization after cerebral ischemia in rats.

Methods: Rats were subjected to transient middle cerebral artery occlusion (tMCAO) and evaluated at 1, 3, 7, 14, and 28 days post-ischemia using diffusion tensor imaging (DTI), T2-weighted imaging (T2WI), and susceptibility-weighted imaging (SWI). The ALPS index was determined from imaging data, focusing on periventricular and corpus callosum/cingulate regions. Brains were analyzed for AQP4 and glial fibrillary acidic protein (GFAP) via immunofluorescence.

Results: The results showed that ischemic rats displayed reduced ALPS indexes, particularly on the ipsilateral side, with an initial decrease at day 1 and subsequent recovery by days 14 and 28. AQP4 polarization in the non-glial scar area around the infarction followed a similar pattern, demonstrating that there was a concordant trend between the ALPS index and AQP4 polarization status.

Conclusion: In conclusion, the ALPS index can reflect changes in AQP4-mediated glymphatic pathway function, suggesting a significant decline in the hyperacute phase and a notable recovery in the early chronic phase, which may have implications for stroke therapeutic strategies.