Fig. 2. Gene expression levels in human-derived kidney proximal tubule cells cultured in the chip compared with regular 2D cultures. Gene expression analysis of drug transporters, endocytosis receptors, and proximal tubule epithelial cell markers show significantly higher MATE1 (SLC47A1), MATE2-k (SLC47A2), breast cancer resistance protein (ABCG2), and LRP2 gene expression in HRPTECs cultured for 7 days in chips compared with HRPTECs cultured for the same time in 2D, whereas expression of P-glycoprotein (ABCB1) is reduced when using GAPDH as reference gene [mean ± S.D., gene expression in chip-cultured HRPTECs compared with 2D cultures by multiple Student’s t tests n = 5 (number of biologic replicates set in advance except when otherwise indicated); n = 8 (GAPDH; due to inclusion of additional biologic replicates after experimental design); n = 4 (AQP1; due to technical error); and n = 3 (ABCG2, SLC5A2, SLC22A1, SLC22A4, SLC22A5, SLC31A1, SLCO4C1; due to inclusion after experimental design) performed with one experimental replicate with 18 comparisons in total, and **P < 0.01, ***P < 0.001, and ****P < 0.0001 (corrected for multiple comparisons using the Holm-Sidak method)]. AQP1, aquaporin 1; CUBN, cubilin; GGT1,gamma-glutamyltransferase 1; HPRT1, hypoxanthine phosphoribosyltransferase 1; TJP1, tight junction protein 1.