Fig. 4: Extracellular matrix targeting increases colon residence time of S. boulardii and decreases inflammation in acute DSS-induced murine colitis.

A Schematic depicting time course of in vivo murine colitis study. C57BL6/J mice were administered 2% dextran sulfate sodium (DSS) in the drinking water for 5 days, then administered regular drinking water for the remainder of the study. Mice were dosed on day 5 with 10⁹ colony-forming units (CFU) of nontargeted (S.b. mSA), fibrinogen-targeted (S.b. FB), collagen IV-targeted (S.b. CIV), or fibronectin-targeted (S.b. FN) yeast via oral gavage. Stool was collected at 12, 24, 48, 72 h post-gavage to measure viable yeast by quantitative culture. B S. boulardii CFU in the stool post-gavage, n = 5 independent animals. C S. boulardii CFU in colon tissue 72 h post-gavage, n = 5 independent animals. D Mean percent body weight of mice over the course of the study. N = 5, significance indicates comparisons to average weights of DSS-only mice at each timepoint. Arrow indicates day of DSS removal and yeast dosing. E Mouse colon length at study termination, n = 5 independent animals, lines represent the mean. Black asterisks indicate significance against DSS and grey asterisks indicate significance against S.b. mSA. F Mean relative expression of pro-inflammatory (Tnfa, Ifng, Il6) and anti-inflammatory (Tgfb, Il10) cytokines in distal colon tissue compared to healthy controls, n = 5. Statistical tests between groups for each gene were independently performed then represented in a single heatmap. Black asterisks indicate significance against DSS and grey asterisks indicate significance against S.b. mSA. Significance indicated as compared to mean relative expression values of DSS-only mice. G Representative images of hematoxylin and eosin staining of colon Swiss rolls; black arrows indicate lesions of severe inflammation/ulceration. H Semi-quantitative histological scores of inflammation accounting for extent of mucosal loss, hyperplasia, and erosions, n = 5 independent animals. Black asterisks indicate significance against DSS and grey asterisks indicate significance against S.b. mSA. I Mean relative expression of Fn1, Fgb, and Col4a1 in the distal colon of DSS mice relative to healthy controls, n = 4. No statistical significance was found. J Representative immunofluorescence of DSS-only colons dosed with either S.b. mSA or S.b. FN. Cell nuclei (blue), fibronectin (pink), and S.b. (cyan) imaged with 2x and 10x objectives, n = 3. Dotted lines represent the limit of detection (Panels B and C). Data are shown as mean ± SD. Significance was determined using ordinary one-way ANOVA with Dunnett’s (panels B, C, D) or Tukey’s (panels E, F, H) multiple comparisons test α = 0.05, *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. Scale bars are 100 μm.