This cross part of a mouse Colon Chip exhibits the actin cytoskeleton of epithelial cells in magenta, the overlying mucus in yellow, and the cells’ nuclei in blue. The staff used this chip in a comparative evaluation of mouse and human microbiomes to check their totally different skills to induce tolerance to the pathogen Salmonella typhimurium. Credit score: Wyss Institute at Harvard College

Trillions of commensal microbes dwell on the mucosal and epidermal surfaces of the physique and it’s firmly established that this microbiome impacts its host’s tolerance and sensitivity of the host to quite a lot of pathogens. Nonetheless, host tolerance to an infection with pathogens shouldn’t be equally developed in all organisms. For instance, it’s recognized that the intestine microbiome of mice protects extra successfully towards an infection with sure pathogens, such because the bacterium Salmonella typhimurium, than the human intestine microbiome.

This raises the attention-grabbing risk that analyzing variations between host-microbiome interactions in people and different species, reminiscent of mice, and pinpointing particular person varieties of bacterial that both defend or sensitize towards sure pathogens, might result in solely new varieties of therapeutic approaches. Nonetheless, whereas the intestinal microbiome composition and its impact on host immune responses have been properly investigated in mice, it’s not attainable to review how the microbiome interacts immediately with the epithelial cells lining the gut beneath extremely outlined circumstances, and thereby uncover particular bacterial strains that may induce host-tolerance to infectious pathogens.

Now, a collaborative staff led by Wyss Founding Director Donald Ingber, M.D., Ph.D. at Harvard’s Wyss Institute for Biologically Impressed Engineering and Dennis Kasper, M.D. at Harvard Medical College (HMS) has harnessed the Wyss’s microfluidic Organs-on-Chip (Organ Chip) know-how to mannequin the totally different anatomical sections of the mouse gut and their symbiosis with a fancy residing microbiome in vitro. The researchers recapitulated the damaging results of S. typhimurium on the intestinal epithelial floor in an engineered mouse Colon Chip, and in a comparative evaluation of mouse and human microbiomes have been in a position to affirm the commensal bacterium Enterococcus faecium contributes to host tolerance to S. typhimurium an infection. The research is revealed in Frontiers in Mobile and An infection Microbiology.

The venture was began beneath a DARPA-supported “Applied sciences for Host Resilience” (THoR) Challenge on the Wyss Institute, whose aim it was to uncover key contributions to tolerance to an infection by learning variations noticed in sure animal species and people. Utilizing a human Colon Chip, Ingber’s group had proven in a earlier research how metabolites produced by microbes derived from mouse and human feces have totally different potential to influence susceptibility to an infection with an enterohemorrhagic E. coli pathogen.

“Biomedical analysis strongly is determined by animal fashions reminiscent of mice, which undoubtedly have great advantages, however don’t present a chance to review regular and pathological processes inside a selected organ, such because the gut, close-up and in real-time. This necessary proof-of-concept research with Dennis Kasper’s group highlights that our engineered mouse Gut Chip platform presents precisely this functionality and gives the likelihood to review host-microbiome interactions with microbiomes from totally different species beneath extremely controllable circumstances in vitro,” stated Ingber. “Given the deep degree of characterization of mouse immunology, this functionality might drastically assist advance the work of researchers who at the moment use these animals to do analysis on microbiome and host responses. It permits them to check their outcomes they get hold of immediately with human Gut Chips sooner or later in order that the main focus may be on figuring out options of host response which are most related for people.” Ingber is also the Judah Folkman Professor of Vascular Biology at HMS and Boston Youngsters’s Hospital, and Professor of Bioengineering on the Harvard John A. Paulson College of Engineering and Utilized Sciences.

Engineering a mouse Gut-on-Chip platform

Of their new research, the staff centered on the mouse intestinal tract. “It has historically been extraordinarily tough to mannequin host-microbiome interactions outdoors any organism as many micro organism are strictly anaerobic and die in regular atmospheric oxygen circumstances. Organ Chip know-how can recreate these circumstances, and it’s a lot simpler to acquire main intestinal and immune cells from mice than having to depend on human biopsies,” stated first-author Francesca Gazzaniga, Ph.D., a Postdoctoral Fellow who works between Ingber’s and Kasper’s teams and spear-headed the venture.

Gazzaniga and her colleagues remoted intestinal crypts from totally different areas of the mouse intestinal tract, together with the duodenum, jejunum, ileum, and colon, took their cells by way of an intermediate “organoid” step in tradition wherein small tissue fragments type and develop, which they then seeded into one among two parallel microfluidically perfused channels of the Wyss’ Organ Chips to create region-specific Gut Chips. The second independently perfused channel mimics the blood vasculature, and is separated from the primary by a porous membrane that enables the alternate of vitamins, metabolites, and secreted molecules that intestinal epithelial cells use to speak with vascular and immune cells.

Homing in on the pathogen

The staff then honed in on S. typhimurium as a pathogen. First, they launched the pathogen into the epithelial lumen of the engineered mouse Colon Chip and recapitulated the important thing options related to the break-down of intestinal tissue integrity recognized from mouse research, together with the disruption of usually tight adhesions between neighboring epithelial cells, decreased manufacturing of mucus, a spike in secretion of a key inflammatory chemokine (the mouse homolog of human IL-8), and modifications in epithelial gene expression. In parallel, they confirmed that the mouse Colon Chip supported the expansion and viability of advanced bacterial consortia usually current in mouse and human intestine microbiomes.

Placing these capabilities collectively, the researchers in contrast the results of particular mouse and human microbial consortia that had beforehand been maintained stably within the intestines of ‘gnotobiotic’ mice that have been housed in germ-free circumstances by the Kasper staff. By accumulating advanced microbiomes from the stool of these mice, after which inoculating them into the Colon Chips, the researchers noticed chip-to-chip variability in consortium composition, which enabled them to narrate microbe composition to practical results on the host epithelium. “Utilizing 16s sequencing gave us an excellent sense of the microbial compositions of the 2 consortia, and excessive numbers of 1 particular person species, Enterococcus faecium, generated by solely one among them within the Colon Chip, allowed the intestinal tissue to raised tolerate the an infection,” stated Gazzaniga. “This properly confirmed previous findings and validated our strategy as a brand new discovery platform that we are able to now use to research the mechanisms that underlie these results in addition to the contribution of significant immune cell contributions to host-tolerance, in addition to infectious processes involving different pathogens.”

“The mouse gut on a chip know-how gives a singular strategy to know the connection between the intestine microbiota, host immunity, and a microbial pathogen. This necessary interrelationship is difficult to review within the residing animal as a result of there are such a lot of uncontrollable components. The great thing about this method is that primarily all parameters you want to research are controllable and might simply be monitored. This technique is a really helpful step ahead,” stated Kasper, who’s the William Ellery Channing Professor of Drugs and Professor of Immunology at HMS.

The researchers imagine that their comparative in vitro strategy might uncover particular cross-talk between pathogens and commensal micro organism with intestinal epithelial and immune cells, and that recognized tolerance-enhancing micro organism may very well be utilized in future therapies, which can circumvent the issue growing antimicrobial resistance of pathogenic bacterial strains.


Human intestine microbiome physiology can now be studied in vitro utilizing Organ Chip know-how


Extra info:
Francesca S. Gazzaniga et al, Harnessing Colon Chip Know-how to Establish Commensal Micro organism That Promote Host Tolerance to An infection, Frontiers in Mobile and An infection Microbiology (2021). DOI: 10.3389/fcimb.2021.638014

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