Abstract
Appropriate intestinal barrier maturation during infancy largely depends on colonization with commensal bacteria. Faecalibacterium prausnitzii is an abundant obligate anaerobe that colonizes during weaning and is thought to maintain colonic health throughout life. We previously showed that F. prausnitzii induced Toll-like receptor 2 (TLR2) activation, which is linked to enhanced tight junction formation. Therefore, we hypothesized that F. prausnitzii enhances barrier integrity, an important factor in appropriate intestinal barrier maturation. In order to test metabolically active bacteria, we used a novel apical anaerobic co-culture system that allows the survival of both obligate anaerobic bacteria and oxygen-requiring intestinal epithelial cells (Caco-2). The first aim was to optimize the culture medium to enable growth and active metabolism of F. prausnitzii while maintaining the viability and barrier integrity, as measured by trans-epithelial electrical resistance (TEER), of the Caco-2 cells. This was achieved by supplementing the apical cell culture medium with bacterial culture medium. The second aim was to test the effect of F. prausnitzii on TEER across Caco-2 cell layers. Live F. prausnitzii did not improve TEER, which indicates that its benefits are not via altering tight junction integrity. The optimization of the novel dual-environment co-culturing system performed in this research will enable the investigation of new probiotics originating from indigenous beneficial bacteria.
Highlights
Faecalibacterium prausnitzii is one of the most abundant bacterial species in the colon of healthy human adults [1,2]
Increasing the abundance of F. prausnitzii in the colonic microbiota has become the target of much research, either by directly delivering the bacterium as a probiotic [11] or by using food ingredients that preferentially stimulate the growth of endogenous F. prausnitzii [12]
Using a novel dual-environment co-culturing system we previously showed that live F. prausnitzii induced Toll-like receptor 2 (TLR2) activation in transfected human embryonic kidney cells (HEK293) [19], which has been implicated in maintaining homeostasis between immunity and tolerance in the intestinal epithelium [20]
Summary
Faecalibacterium prausnitzii is one of the most abundant bacterial species in the colon of healthy human adults [1,2]. Intestinal maturation, including the development of the intestinal barrier integrity and immune function as well as the establishment and stabilization of the microbiota, occurs throughout the first two years of life. Much of this process is regulated by diet (e.g., breast milk versus infant formula), Nutrients 2017, 9, 1349; doi:10.3390/nu9121349 www.mdpi.com/journal/nutrients
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