Evaluation of Porcine Intestinal Epitheliocytes as an In vitro Immunoassay System for the Selection of Probiotic Bifidobacteria to Alleviate Inflammatory Bowel Disease

The use of in vitro systems that allow efficient selection of probiotic candidates with immunomodulatory properties could significantly minimize the use of experimental animals. In this work, we generated an in vitro immunoassay system based on porcine intestinal epithelial (PIE) cells and dextran sodium sulfate (DSS) administration that could be useful for the selection and characterization of potential probiotic strains to be used in inflammatory bowel disease (IBD) patients. Our strategy was based on two fundamental pillars: on the one hand, the capacity of PIE cells to create a monolayer by attaching to neighboring cells and efficiently mount inflammatory responses and, on the other hand, the use of two probiotic bifidobacteria strains that have been characterized in terms of their immunomodulatory capacities, particularly in mouse IBD models and patients. Our results demonstrated that DSS administration can alter the epithelial barrier created in vitro by PIE cells and induce a potent inflammatory response, characterized by increases in the expression levels of several inflammatory factors including TNF-α, IL-1α, CCL4, CCL8, CCL11, CXCL5, CXCL9, CXCL10, SELL, SELE, EPCAM, VCAM, NCF2, and SAA2. In addition, we demonstrated that Bifidobacterium breve M-16V and B. longum BB536 are able to regulate the C-jun N-terminal kinase (JNK) intracellular signalling pathway, reducing the DSS-induced alterations of the in vitro epithelial barrier and differentially regulating the inflammatory response in a strain-dependent fashion. The good correlation between our in vitro findings in PIE cells and previous studies in animal models and IBD patients shows the potential value of our system to select new probiotic candidates in an efficient way.