Measuring Epithelial Barrier Function

TER was measured as described previously^{47 (link)}. SC cells were seeded on Transwell polyester membrane insert (0.4 μm pore size, 6.5 mm diameter; 3470, Corning Inc., Corning, NY) in 24-well culture plates and cultured for 7 days or more until the TER values were stabilized. The cells were cultured in serum-free DMEM overnight before treatment. Then they were treated with 5 ng/mL human recombinant TGF-β2 (302-B2, R&D Systems, Minneapolis, MN) with or without Y-27632 (259-00613, FUJIFILM Wako Pure Chemical), human recombinant bone morphogenic protein 4 (BMP4, 022-17071, FUJIFILM Wako Pure Chemical) or SB203580 (S1076, Selleck Chemicals, Huston, TX). TER was measured at 24, 48, and 72 h after treatment. At least three independent experiments were performed.