Fig 1: Cytoarchitectural characterization of vessel-like structures.(A) Astrocytes (monoclonal GFAP+ cells) form a layer of support around endothelial cells that organize into tubular structures readily identified by phalloidin. (B) Tubular structures are tightly packed with endothelial cells expressing intercellular adhesion molecule-2 (ICAM-2), although there is a degree of inconsistency in along the VLS indicating different stages of development/maturity. (C) Endothelial cells organized into VLS are polarizing as indicated by the expression of the apical marker podocalyxin that influences astrocytes positioning of endfeet. (D) Endothelial cells within the VLS also express markers indicative of tight junctions, such as Claudin-5 and Occludin.