Introduction

Permeability alterations, associated with excessive and inappropriate inflammatory responses, underlie the pathogenesis of many diseases such as inflammatory bowel diseases (IBD). Identification of novel molecular players involved in the control of the intestinal barrier is therefore of great interest for the management of IBD. A recent study has revealed that dysfunction of a cadherin-based intermicrovillar adhesion complex (IMAC), critical for brush border (BB) assembly and maturation, is associated with disease severity and treatment response in IBD ^1,2,3.

Aims & Methods

The aim of this study was to determine the effects of the probiotic yeast Saccharomyces boulardii CNCM I-745 (Sb, Biocodex, France) on the protection and/or restauration of the intestinal epithelium barrier function upon inflammation.
Experimental models for the human colon were based on 2D monolayers (Transwell insert) formed by either the Caco-2/TC7 cell line or organoids. Inflammatory set-ups included treatment with TNF-a/IL1-b cytokines and IBD organoids. Paracellular and transcellular permeability were assessed by real-time transepithelial electrical resistance (TEER) and dextran-FITC measurements. Localization and expression levels of junction and BB proteins (E-cadherin, sucrase isomaltase, DPP-IV, Villin; IMAC: CDHR5, CDHR2, MYO7-b) were analyzed by Western blot and immunofluorescence. BB assembly through microvilli clustering was observed using super-resolution spinning-disk confocal microscopy. Sb treatment was initiated either prior (preventive model) or after (curative model) cytokines stimulation.

Results

We showed that Sb supernatant strengthens intestinal barrier function both in Caco-2/TC7 cells and colonoïd organoid-derived monolayers. In Caco-2/TC7 cells exposed to pro-inflammatory cytokines, Sb is able to preserve the structural and functional parameters of the cell monolayer and to accelerate their recovery. We found that Sb treatment has a positive effect on the adherens junction localization (E-cadherin complex) in both preventive and curative situations. In addition, we discovered that Sb also acts on the IMAC, favoring microvillar clustering and maintaining the presence of IMAC at the top of microvilli, thereby restoring a mature and functional BB.

Conclusion

Taken together our results demonstrate that Sb CNCM I-745 globally protects and reestablishes functional integrity of the intestinal epithelium in inflammatory conditions. Sb may thus offer a significant benefit in diseases with persistent lesions of the intestine, such as IBD. In addition, they suggest that a better understanding of BB assembly through the IMAC will foster new therapeutic opportunities.

References

1. Crawley, S. W. et al. Intestinal Brush Border Assembly Driven by Protocadherin-Based Intermicrovillar Adhesion. Cell 157, 433–446 (2014).
2. Gaeta, I. M., Meenderink, L. M., Postema, M. M., Cencer, C. S. & Tyska, M. J. Direct visualization of epithelial microvilli biogenesis. Curr. Biol. 31, 2561 (2021).
3. VanDussen, K. L. et al. Abnormal Small Intestinal Epithelial Microvilli in Patients With Crohn’s Disease. Gastroenterology 155, 815–828 (2018).

Disclosure

The present study was sponsored by Biocodex (Gentilly, France) who did not play any role in the execution of the experiments or the interpretation of the data.