VSL# 3 Probiotic Mixture Modifies Microflora but Does Not Heal Chronic Dextran-Sodium Sulfate-Induced Colitis or Reinforce the Mucus Barrier in Mice

The mucus layer covering the epithelium is one of the main lines of defense of the colonic barrier. Both mucus gel and mucin expressions are altered during colonic inflammation and could be involved in epithelial repair. We postulated that modulating colonic mucus and mucins by probiotic supplementation could contribute to healing inflammatory mucosa. Our aim in this study was to determine whether probiotics could repair dextran-sodium sulfate (DSS)-induced chronic colitis in mice, and whether modifications of the colonic mucins could be involved. For that purpose, the VSL#3 probiotic mixture of 8 lactic acid bacteria probiotic strains was administered daily for 2 wk to mice with a mucosa impaired by a mild DSS treatment, and to mice with a normal mucosa. Probiotic strains survived in the gastrointestinal tract, increased the cecal concentrations of bifidobacteria, and modified cecal microflora metabolic activity in both DSS-treated and healthy mice. However, probiotic supplementation did not reverse the inflammation induced by DSS at either the macroscopic or histological level. Concurrently, probiotics did not modify the colonic mucus barrier, in terms of either mucin gene expression or adherent mucus layer thickness. In conclusion, the modification of microflora by supplementation with the VSL#3 probiotic mixture did not help to repair the colonic barrier breakdown caused by DSS treatment. The potential healing roles of mucins were neither confirmed nor invalidated by this study.