Fig. 5

Comparison of barrier characteristics of ECPC4 versus pmCPECs. a The time-dependent progression of the transepithelial electrical resistance (TEER) of ECPC4 cells and pmCPECs grown on standard (luminal) or inverted (abluminal) Transwell filter inserts was measured by impedance spectroscopy using the cellZscope device. The TEER of ECPE4 hardly differs from the TEER measured across laminin coated empty filters (EF). In contrast, pmCPECs reach a TEER of 150–200 Ω cm² on d7. The figure shows one representative experiment (of 4) of pmCPECs in comparison to ECPC4 over their last 72 h in culture with 3 filters per condition and 1 empty filter. The colored lines show the mean TEER values of triplicate measurements surrounded by colored areas, which represent the SD. The area under the curve (AUC) as a measure for the overall TEER across the cellular barriers over time (Unit: Ω cm² h) was assessed for a comparison of the overall resistance of the cell layers. *p < 0.05. b, c The permeability for Alexa Fluor 680-3 kDa dextran (Pe_3kDa) (b) was measured in 5 independent experiments with at least three filters per condition (ECPC4 standard: n = 3, ECPC4 inverted: n = 3, pmCPECs standard: n = 5, pmCPECs inverted n = 4) and the permeability for 457 Da Lucifer Yellow (Pe_LY) was measured once with at least 3 filters per condition (ECPC4 standard: n = 3, ECPC inverted: n = 3, pmCPECs standard: n = 5, pmCPECs inverted: n = 4) ****p < 0.0001 (c). d Immunofluorescence staining for claudin-1 (Cldn-1), cytokeratin (CK) and nuclei (DAPI) showed no differences between monolayers grown on the upper (standard) or lower (inverted) side of the filter. Scale bar 100 μm. Bars in b, c represent the mean permeability coefficients Pe ± SD