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. 2018 Oct 22;115(45):E10539–E10547. doi: 10.1073/pnas.1810819115

Fig. 1.

Fig. 1.

Administration of DSS specifically induces epithelial barrier dysfunction in a gut inflammation-on-a-chip. (A) An experimental design that describes the microenvironment of the human intestine undergoing DSS-mediated epithelial barrier dysfunction and subsequent transmigration of gut bacteria and immune cells (+DSS) compared with the normal healthy condition (−DSS). AP, apical; BL, basolateral. (B) Morphology of the villus epithelium visualized by the differential interference contrast (DIC) (gray, top views) and immunofluorescence (IF) microscopy (colored, side views) at 0 and 48 h after DSS treatment (2%, wt/vol). A white dashed line indicates the location of a porous basement membrane. A white dotted line indicates the contour of villous microarchitecture. The height of villi was measured by analyzing IF micrographs of the vertical cross-cut view (n = 7). (C) Intestinal barrier function of the control intestinal villi (circle; n = 10) compared with the villi challenged to 2% (wt/vol) DSS (square; n = 10) quantitated by TEER. (D) Apparent permeability of a paracellular marker (FITC-dextran; 20 kDa) through the villous epithelial layer in the absence (Control) or the presence of DSS (DSS) (n = 3). Permeability values of the Control was below the detection range. Localization of E-cadherin adherens junction (E) and ZO-1 tight junction proteins (F) (Upper) and the line scan of corresponding IF images (Lower) in the absence (Control) or the presence of DSS treatment (+DSS) for 48 h. (G) Visualization of the mucus layer via IF staining with Alexa Fluor 633-conjugated WGA at 48 h after DSS treatment (Upper) and its quantification (Lower) (n = 8). (H) Epithelial cytotoxicity in response to the DSS treatment quantitated by an lactic acid dehydrogenase (LDH) assay. The culture medium collected from the AP and BL microchannels in the gut inflammation-on-a-chip challenged to DSS for 48 h did not show any LDH release. Cell lysate of Caco-2 cells grown on a chip was used as a positive control (n = 10). (Scale bars, 50 μm.) *P < 0.05, **P < 0.001, ***P < 0.0001.