SOX7 and ERG reprograms neuroectoderm into microenvironmentally attuned brain endothelial cells that possess forebrain regional bias

Reliable human blood brain barrier (BBB) models are limited by a persistent problem of cellular identity: many protocols select cells for barrier or transporter properties rather than authentic, regionally specified brain endothelium. Here we show that constitutive expression of the transcription factors SOX7 and ERG converts human pluripotent stem cell derived epithelial barrier-forming cells into bona-fide vascular endothelial cells (SE rECs) whose transcriptome and proteome converge on primary human brain endothelium. Benchmarked against a human adult-brain endothelial atlas, SEr ECs acquire a forebrain-biased regional program stronger than that of permissively (ETS-)reprogrammed or umbilical-vein endothelial cells, reproducibly across biological replicates, although it does not reach the absolute regional identity of in-vivo brain endothelium. At the transcript level, epithelial-derived barrier forming cells (iBFCs) cells score highly on select barrier and transporters genes yet lack endothelial lineage identity, showing that transporter benchmarks alone do not establish endothelial fate. Coculture of SE rECs with astrocytes and pericytes in a two-dimensional neurovascular-unit model as well as a perfused microfluidic device induces mature BBB features and reduces paracellular permeability. SE rECs thus provide a lineage-faithful, organotypically informed platform for modelling the human BBB.