Fig. 2. The effect of L. casei AMBR2 on nasal epithelial barrier function in vitro. Primary nasal epithelial cells from healthy controls and CRSwNP patients were grown at air-liquid interface for 21 days, and were stimulated with different concentrations of L. casei AMBR2 (both n = 6) for 6 hours. (A) Effect of different concentrations of L. casei AMBR2 on TEER and FD4 passage at time point six hours of epithelial cell cultures from healthy controls and patients with CRSwNP. (B) mRNA expression of occludin, ZO-1, claudin-1 and claudin-4 in nasal biopsies of healthy controls and patients with CRSwNP (both n = 5). Relative mRNA expression vs the housekeeping gene β-actin. (C) Representative immunofluorescence staining for occludin and ZO-1 in CRSwNP patients after treatment with L. casei AMBR2 (10⁷ CFU/mL), compared to controls. White arrow indicates disrupted tight junction formation (scale bar = 1 μm). In (A), data are presented as mean ± SEM and in (B) data are presented as median with interquartile range. Two-way ANOVA with post hoc analysis for TER measurements in (A). One-way ANOVA with post hoc analysis for FD4 measurements in A and B.

CRSwNP, chronic rhinosinusitis with nasal polyps; TEER, trans-epithelial electrical resistance; FD4, fluorescein isothiocyanate-dextran 4 kDa; CFU, colony-forming unit; SEM, standard error of mean; ANOVA, analysis of variance; ZO-1, zonula occludens-1.

^*P < 0.05; ^†P < 0.01; ^‡P < 0.001.