The Epithelial Barrier Model Shows That the Properties of VSL#3 Depend from Where it is Manufactured

BACKGROUND: VSL#3 has been extensively investigated and is currently recommended for the prevention and treatment of chronic pouchitis and ulcerative colitis. Nonetheless, in vitro and in vivo stud-ies have recently shown variability in the VSL#3 efficacy often attributed to the manufacturing process. OBJECTIVE: The aim was to comparatively study the in vitro effects of two VSL#3 preparations produced in different sites (named US- and Italy-made VSL#3) on CaCo-2 epithelial barrier model in terms of trans-epithelial electrical resistance (TEER), dextran flux and expression of Tight Junctions (TJ) proteins i.e. zonulin-1 (ZO-1) and occludin, in the absence or presence of a heat stress-related damage of mono-layer. METHODS: TEER was evaluated on CaCo-2 differentiated monolayers. Epithelial permeability of polarized monolayers was assessed by measuring the FITC-labeled dextran flux from the apical to basolateral chambers. ZO-1/occludin levels were analyzed by western blot analysis. A set of experiments was per-formed to compare the effects of both VSL#3 on TEER values, dextran flux and ZO-1/occludin expres-sion in CaCo-2 monolayers after heat stress exposure. RESULTS: US- and Italy-made VSL#3 have opposing effects on TEER values, dextran flux, and ZO-1/occludin expression, being all these parameters negatively influenced just by Italy-made product. US-made probiotic did not affect baseline TEER, dextran flux and ZO-1 expression and strongly increased occludin levels. Of note, pre-treatment of monolayer with US-made VSL#3, but not Italy-made product, totally prevented the heat-induced epithelial barrier integrity loss. CONCLUSION: Our data trigger the need for reassessing efficacy or safety of the Italy-made VSL#3 con-sidering intestinal epithelial barrier plays an important role in maintaining host health.