Hi Joachim,

If your goal is to check homogeneity of the cell population for the beginning I would suggest using anti-PECAM-1 (CD31) antibody for endothelial cells and anti-GFAP for glia. You could also consider staining vWF to identify ECs. In our hands ZO-1 immunostaining is weak in cultured primary HBEC and depends on the fixation protocol.

Best

Another classic pan-endothelial marker that should distinguish these cells from glia is Ve-Cadherin.