AQP4 and Stroke: With regard to previous work where a lack of perivascular AQP4 polarization hampered perivascular CSF penetration into the brain parenchyma 41, stroke induction yielded a significantly decreased CSF tracer penetration when compared to non-stroke sham mice (Figure 8A and B). When mice where given EVs, however, the CSF tracer penetration into the ischemic cortex was increased, suggesting a new way of action for these EVs.