Study On The Defense Mechanism Of Escherichia Coli Nissle 1917 Against Salmonella In Human Gut-on-chip

Probiotics play an important role in resisting intestinal dysfunction,which can resist intestinal pathogens invasion and regulate intestinal immune function.But in current research,the traditional in vitro research model is difficult to realize long-term co-culture of intestinal cells and bacteria and dynamic analysis of the interaction between probiotics and pathogenic bacteria,so that the effective mechanism of probiotics is still unclear.The microfluidic based gut-on-chip technology can simulate the human intestinal physiological structure,nutrient absorption,material transport and pathophysiology,becoming a powerful tool for studying the interaction between intestinal microorganisms and hosts in vitro.This study combined microfluidic technology and cell biology to build an intestinal organ chip in vitro,and used the gut-on-chip to study the defense effect of probiotic E.coli Nissle 1917 against Salmonella and further analyzed the defense mechanism.In the experiment,a three-dimensional villous structure intestinal chip was constructed using Caco-2 cells and a mucus-secreting HT-29 cell co-culture system.An in vitro Salmonella infection model was established and the effect of probiotics on Salmonella infection was evaluated at different time points.To explore the mechanism of probiotics.The experimental results show that the gut-on-chip has the function of intestinal epithelial barrier and can support the growth of intestinal bacteria.The results of Salmonella infection experiments show that as the infection time increased,the degree of destruction of the intestinal epithelial tight junctions become greater.By studying the effects of E.coli Nissle 1917 on the growth of Salmonella in three modes of action: prevention,competition,and therapy,it was found that E.coli Nissle 1917 can most effectively reduce Salmonella adhesion and proliferation in the prevention mode,while Salmonella proliferation in the therapy mode was not affected.At the same time,the protective effect of E.coli Nissle 1917 on the tight junction of intestinal epithelium was also studied.The results show that E.coli Nissle 1917 can protect the complete structure of tight junction protein between epithelial cells,and the protective effect of the prevention group was significantly stronger than competition and therapy group.In order to further reveal the protective mechanism of probiotics,a proteomic analysis of intestinal cells in the intestinal chip was performed,and it was found that the prevention mode compared with competition and therapy modes,cell adhesion and cytoskeleton-related protein expression were significantly up-regulated.Therefore,in this study,the gut-on-chip was used to simulate the structure and function of the human intestine in vitro,establish a disease model,and analyze the mechanism of probiotics.It is expected to provide an effective strategy for the in vitro analysis of the relationship between intestinal microorganisms and intestinal physiology.