Fig. 1

BLECs in co-culture with pericytes develop a tight barrier. CD34⁺-derived endothelial cells were cultured as monoculture or co-culture with brain pericytes for 6 days in a transwell system. a Expression of selected BBB marker proteins was induced in co-culture (Co) in comparison to monoculture (Mono) as shown by Western blot. Numbers under the representative bands indicate protein levels normalised to β-actin and to monoculture control. b Paracellular permeability for fluorescein of CD34⁺-derived endothelial cells monolayers either cultured alone or together with pericytes. Data are shown as mean ± SD (n = 3), ***p < 0.001. c Expression of claudin-5 in CD34⁺-derived endothelial cells cultured alone or in co-culture with brain pericytes shown by immunofluorescence. Magnification ×400, green: claudin-5, blue: DAPI nuclear staining. d Messenger RNA expression of transporters and tight junction proteins in BLECs was quantified by qPCR. Target gene expression was normalized to endogenous control and shown as fold over control, which was arbitrarily set as 1 (control level marked in graph). Data are shown as mean ± SD of three experiments. *p < 0.05 statistically significant versus control. BCRP breast cancer resistance protein (ABCG2), CLDN5 claudin-5, GLUT-1 glucose transporter type 1 (SLCA1), LRP1 LDL receptor related protein 1, MCT1 monocarboxylate transporter 1 (SLC16A1), MRP4 multidrug resistance-associated protein 4 (ABCC4), OCLN occludin, P-GP P-glycoprotein 1 (ABCB1), RAGE receptor for advanced glycation end-products (AGER), TFR transferrin receptor (TFRC), ZO1 zonula occludens 1 (TJP1)