Figure 6.

Transforming growth factor-β (TGFβ)/bone morphogenetic protein (BMP) signaling via SMAD4 modulates barrier function/transepithelial resistance in a cell-autonomous manner. Representative images of hematoxylin and eosin (H&E) stain demonstrating polarized monolayers of colon epithelial cells grown on collagen-coated transwell membranes before (A) and after (B) initiation of air-liquid interface (ALI). C: normalized transepithelial resistance (TER) for wild-type (SMAD4+) colonoids on collagen-coated transwells in an ALI system. TGFβ/BMP co-treatment in the basolateral chamber was associated with a significant increase in TER compared with vehicle-treated controls at 24- and 48-h (P < 0.001 by repeated-measured ANOVA/mixed effects model). D: normalized TER for SMAD4 knockout colonoids grown on collagen-coated transwells in an ALI system. TGFβ/BMP co-treatment in the basolateral chamber failed to elicit a change in TER compared with vehicle-treated controls at 24- or 48-h. For both C and D, data represent the mean and standard deviation of three biological replicates, with biological replicates being plated, treated, and measured on separate days. Experimental arms were compared using repeat measures ANOVA/Mixed effects model. TER measurements for each well were normalized to the final pretreatment TER for that well (Day 0 on the X-axis).