Isogenic blood–brain barrier models based on patient‐derived stem cells display inter‐individual differences in cell maturation and functionality

The blood–brain barrier ( BBB ) constitutes an important component of the neurovascular unit formed by specialized brain microvascular endothelial cells ( BMEC s) surrounded by astrocytes, pericytes, and neurons. Recently, isogenic in vitro models of the BBB based on human pluripotent stem cells have been documented, yet the impact of inter‐individual variability on the yield and phenotype of such models remains to be documented. In this study, we investigated the impact of inter‐individual variability on the yield and phenotype of isogenic models of the BBB , using patient‐derived induced pluripotent stem cells ( iPSC s). Astrocytes, BMEC s, and neurons were differentiated from four asymptomatic patient‐derived iPSC s (two males, two females). We differentiated such cells using existing differentiation protocols and quantified expression of cell lineage markers, as well as BBB phenotype, barrier induction, and formation of neurite processes. iPSC ‐derived BMEC s showed barrier properties better than hCMEC /D3 monolayers; however, we noted differences in the expression and activity among iPSC lines. In addition, we noted differences in the differentiation efficiency of these cells into neural stem cells and progenitor cells (as noted by differences in expression of cell lineage markers). Such differences were reflected later in the terminal differentiation, as seen as ability to induce barrier function and to form neurite processes. Although we demonstrated our ability to obtain an isogenic model of the BBB with different patients’ iPSC s, we also noted subtle differences in the expression of cell lineage markers and cell maturation processes, suggesting the presence of inter‐individual polymorphisms.