Immunostaining using anti-AQP4 and anti-CD31 antibodies can be used to determine glioma cells in perivascular space.
Perivascular space is a cavity around blood vessels in the brain and is covered by astrocyte endfeet. If a glioma cell is in perivascular space, it should be located between astrocyte endfeet and blood vessel endothelial cells. Therefore, immunostaining using anti-AQP4 (stain astrocyte endfeet) and anti-CD31 antibodies (stain blood vessel’s endothelial cells) can locate glioma cells in perivascular space (Watkins et al., 2014).
Since glioma cells are known to cause retraction of astrocyte endfeet over the blood vessels, sometimes you may see glioma cells very close to endothelial cells without astrocyte endfeet (Watkins et al., 2014).
Watkins et al., 2014. Disruption of astrocyte-vascular coupling and the blood-brain barrier by invading glioma cells. Nat Commun. 5, 4196. PMID-24943270; Full Text Link: nature, PMC4127490